Solid State SPS Microwave Generation and Transmission Study€¦ · Owen E. Maynard CONTRACT NASS-33157 NOVEMBER 1980 . TECH LIBRARY KAFE, NM ll~ll~lllul~Il~lIMII#l~~l 0062038 NASA

A CI~A Contractor Report 3339

Solid State SPS Generation and Volume II - Phase

Microwave Transmission Study

U Final Report, Appendices

Owen E. Maynard

CONTRACT NASS-33157 NOVEMBER 1980

TECH LIBRARY KAFE, NM

ll~ll~lllul~Il~lIMII#l~~l 0062038

NASA Contractor Report 3339

Solid State SPS Microwave Generation and Transmission Study

Volume II - Phase II Final Report, Appendices

Owen E. Maynard Raytheon Company Wayland, Massachusetts

Prepared for Marshall Space Flight Center under Contract NASS-3 3 15 7

National Aeronautics and Space Administration

Scientific and Technical Information Branch

1980

Technical Note

SPS._Pilot_B_eam Ionosp.heri.c Effects ..:..Discussion of Critical Issues

1. INTRODUCTION

The ionosphere will introduce phase errors in the pilot beam system through

a combination of “bias” and stochastic fluctuations effects. Specific actions must

be taken to remove these errors in order to make the pilot beam system capable

of performing its assigned function.

The approach available for the solutipn of the problem involves the use of

averaging processes. However, in order to perform them in an effective manner,

we must first measure and,remove from the arriving phase of the pilot beam the

steady state ionospheric “bias”. The dual frequency scheme assumed for the SPS

Pilot Beam Baseline System (October 1978 version) employing two tones one at

either side of the carrier of the downcoming power beam, each separated from

this carried by Af = 100 MHz, cannot accomplish this task. An alternative

scheme based on the use of three frequencies can, on the contrary, do it. We

review here-under its basic principle, which could be applied to a broad family

of mechanizations. Once the “bias” is removed, we have to cope with the sto-

chastic fluctuations. Starting point of any action in this sense must be a reliable

estimate of the expected stochastic phase errors. This note also addresses this

critical is sue.

2. The 3-frequency versus the 2-fre

ionospheric “bias”

The SPS Pilot Beam Baseline System (October 1978 version) suggested to

implement the pilot beam approach with a dual frequency arrangement. Two

carriers were allocated at either side of the 2.45 GHz carrier of the downcoming

power beam, each with a typical separation from it of Af = 100 MHz. From phase

measurements performed at these two carriers, it was claimed that it would be

possible, through suitable processes, to remove the ionospheric effects.

Unfortunately this is not the case. In fact, it can be shown that the two-

frequency method cannot work unless the spacing between the two frequencies is

at least one order of magnitude smaller than the spacing chosen in the Baseline

System de sign. The reason is that there is a severe ambiguity in the value of the

measured phase, that does not make it possible to remove the ionospheric bias.

A numerical example will clarify the difficulty.

A-l

The value of the phase path length over a transionospheric path with

geometric length L and total electron content s

Ndl, is given at the frequency f

by the expression:

G rad s Ndl)

where v 1 is the velocity of light in free space.

By specializing Equation (1) to the frequencies f 1 and f2, by then multi-

plying @l (at frequency fl) by the ratio f2/fl, and by finally subtracting from

this product the quantity @2 (phase at the frequency f2) we obtain:

4@ rad =@ f2 40

1 fl - 02 = 2l-r. 5

In Equation (2) we have:

9 = 3 x lo8 m/set

fl = 2.35109 Hz

f2 = 2.55 109 Hz 1

Ndl = 1018 el/m2

\’ 3 Ndl (2)

Values chosen by the Baseline System Design

(We assume here a large value for this quantity, a value, however, that is not uncommon at all)

Under these assumptions, we have

This is an unacceptable value for A@. The reason is that phase measuring

instrumentation of every conceivable type will read for the A@ above the erroneous

value 0.2 x 2rr, from which an incorrect value for s

Ndl would be derived. In

other words, no instrumentation or approach exists that could eliminate the 27-r

ambiguity (in this case a 9 fold ambiguity) from the measurements.

Equation (2) shows that in order to keep A# < 21-r, for c

Ndl = 1018 el/m2

and for f2 = 2. 55 109 Hz, we must keep Af < 10 MHz, a spacing an order of

magnitude smaller than contemplated by the Baseline System Design (by adopting

Af = 10 MHz, we would have A@ = 0.89 x 21-r). However, in the SPS case, it is not

A-2

advisable to allocate the carriers of the pilot beam system so close to the power

beam carrier.

This fundamental limitation of the Z-frequency method was recognized

twenty years ago by Prof. Von R. Eshleman of Stanford University. He solved

the problem of achieving wide carrier-to-carrier separation in an ionospheric

correction link and still avoided the 2rr ambiguity problem, with his scheme

known as the “3-frequency method” (Eshleman et al, 1960; Burns and Fremouw,

1970).

The basic principle of the method can be illustrated as follows. Let us

consider three frequencies

fl = f. - Af

f. ’

f2 = f. + Af,

and let’s call @,, flo and f12 the phase path lengths in a transionospheric link,

respectively at fl, f. and f2.

The following expressions apply for the two phase differences ($J~ - @,)

and (@, - 8,):

A@, = @1 - tie = ZTT . $- 1

(fl - fo) L - 40

A8B =@o - G2 = 2l-r + 1

(f. - f2) L - 40 (t-t) SNdl}

At this point, the method goes further than is usually the case with the dual

frequency approach, and requires the computation of the difference of the two

differences above:

(3)

This is the fundamental observable, from which 1 Ndl is computed.

A-3

A numerical evaluation of Equation (3) shows that for s

Ndl = 1018

el/m2 and for f. = 2. 55 109 Hz, .-

A@B = 2Tr (1.6 x lo- 17) Af2

With the USC’ of the three frequencies, the avoidance of the 2rr ambiguity brings

forth the following requirement for the maximum allowable value of the fre-

quency separation among the various tones:

Af2<-- ’ 1.6 x 10

-12

Af zc 249MHz

We conclude therefore that we can easily meet the requirements of keeping

any carrier of the multifrequency p,ilot beam system at least 100 MHz away from

the frequency of the downcoming power beam and still retain the ability of correc-

ting for the ionospheric “bias” without 21-r ambiguities.

Figure 1 shows a possible way in which the various frequencies could be

allocated. Several other suitable allocations are also possible. See Appendix A

for a possible mechanization of the 3-frequency scheme.

f2

149 MHz 100 MHz

fO fl

-- -------.-L.__

249 MHz

--bf

Figure 1. Possible Frequency Allocation

A-4

Once that, with the use of the three frequency method, it has been possible to

remove from the measured phase the effect of the ionospheric “bias” at the

wanted pilot beam frequency, we can properly apply to the residuals suitable

averaging processes in order to reduce the effect of the stochastic fluctuations

due to ionospheric inhomogeneities.

3. Stochastic Phase Fluctuations due to Ionospheric Inhomogeneities

In this past dccadc surprising results have been obtained by researchers

active in the arca of ionospheric scintillation, while cxpc rimenting with trans -

ionospheric paths at microwave. Unexpectedly, large scintillation indeces have

been observed at microwave in space-to-ground links that cross the nighttime F

region of the ionosphere at equatorial, tropical and aurora1 latitudes. Observed

phase fluctuations were found to be much larger than could be expected from such

analytical approaches as the “thin scattering layer” theory. In fact, by applying

thin scattering theory to the spectral density distribution 6n n

t- -1 versus K(wave

Km

number, Km-l) of the electron density inhomogeneities actually measured in the

ionosphere with rockets and other means, the phase fluctuations that would be

computed for a microwave link that crosses the region containing these inhomo-

geneiticbs are much smaller than c>xpcrimentally ascertained. A “workman-like

approach” to solve at lcast temporarily the difficulty (while a suitabb: nc:w theory

is being worked out) is the one suggested by Basu and Basu (1976). It involves

altering “phenomenologically” the spectral density distribution of Figure 2 by

moving the curve A-A to the B-B location and using the new curve as the basis

for the computation of phase fluctuations with the thin scattering theory formula.

In this way, results are obtained that match the observations. The applicable

formula is (Costa and Kelly, 1976):

QO 2 d z = 27-r (reX)2 F ( 6d2 (L set 0) K

0

where:

$0 = rms phase fluctuation, rad.

r e = classical radius of electrons = 2. 818 10 -15,

0 = angle between the ray path and the vertical

(4)

A-5

L = thickness of the irregular layer, m (at ionospheric F2 layer heights)

x = wavelength of the propagating wave, free space value,

m (X = 0.12245 m at 2.45 GHz)

P2 = cos 2 $ + a2 sin2 Jl, where ti is the angle between the direction of

the Earth magnetic field and the ray path and where (11 is the axial

ratio

iI P

a~ 1 for equatorial paths ( II = 90”, p2 = CL~)

K = wave number = - cn (where Xs is the spatial wavelength of the

irregularities) ’

KO = outer scale wave number

For equatorial transionospheric paths, we have in (4) L = 2~10~ m, K. = 0.31 Km-l

set 0 2 1.

Figure 2. The dashed line is a model spectrum used by Costa and Kelley (1976) to characterize the breakup of density gradients in upwelling structures. The solid line is a spectrum used by Basu and Basu (1976) to typify extended topside irregularities. (From Basu and Kelley, 1977)

A-6

To proceed in the computation, we must define the wave number interval’

in the x-axis of Figure ‘2, across which to integrate the spectral density curve.

This interval must include all spatial wavelengths equal to or smaller than the

“size” of the pilot beam ray at ionospheric heights. This could not be derived

from purely geometrical considerations (where a 10 meter spatial size F layer

height would be obtained). The value obtained this way would not have physical

meaning. On the contrary, physically meaningful results are obtained by con-

structing the Fresnel ellipsoid(J%got et al, 1959) for the ground-to-space pilot

beam link (Figure 3). The radius of the first Fresnel zone at ionospheric height

is the rational representation of the “size” of the ray. From Figure 3, we have

that this radius is:

radius of the first Fresnel zone = FB = /y-p-

In the case of the peak of the F layer, dl * 400 Km, d2 = 37500 Km and therefore

FB = 2.2 x lo2 = 220 meters.

The interval of integration in Figure 2 must therefore be extended from at least

a spatial wavelength equal to this value down to all smaller wavelengths (wave

numbers from w 28 Km -1

to -300 Kin -l). Figure 2 yields:

I&,- 0.025 n 2 J- 272 = 0.2

and with an electron density in the F2 layer of 2. 5 lo-l1 rnm3, Equation (4) gives

I() = 1.3 x 10 -11( 64 = 1.3 lo-l1 x 0.2 x 2.5 10;:; 538'

This value of @o is a realistic estimate for the phase fluctuations to be expected

at 2.45 GHz in transionospheric paths crossing perturbed regions such as the

equatorial or the aurora1 ionosphere. In fact, this estimate is substantiated by

the experimental evidence collected by the DNA wideband satellite (Eremouw et al,

1978). Figures 4 and 5 show fluctuations upwards of 3 5O which is comparable with

the above calculation. We are reminded that the DNA satellite could not see,

A-7

37500. Km

x = 0. 12245 m

TF = dl

FR = d2

TR = dl +d2

# ,

I \ Ellipsoid I \ I I

, i I - F First Fresnel Zone

layer

Figure 3. Fresnel Ellipsoid of the Pilot Beam Ray

A-8

-I---I ’ ’ 1””

POKER FUT 20 MAY 1976 - 300

-w

-- lal

P --2’ if .

I -20 I

d 2

- 10

---w- 0.1 1 -6

_ =CDRtlECTED FOR PHASE I

- ,SCINTILLATIONS DN SMND -3 - REFERENCE CHANNEL (mm text)

I -2

2.45 GHz -, 0.01 1 ,111111l ,I , , , , ,,L

0.1 1.0 10 FREQUENCY - ‘3-k

Figure 4. Frequency dependence of phase-scintillation index, during two 20 set periods of the ass above Poker Flat, 29 May 1976 compared with an f’ P dependence. (from Fremouw et al, 1978)

16 DECEMBER 1076

UNCERTAINTY DUE TO - PHASE SCINTILLATIDNS

0.1 1.0 10 FREOUENCY - GHz

Figure 5. Frequency dependence of phase scintillation index during two 20 set periods of pass recorded at Ancon on 16 I)ec. 1976, compared with an f -Idependence arbitarily passc:d through the 413 -MHz data point. (from Fremouw et al, 1978)

A-9

(because of the integration time used in the measurements), spatial wavelengths

shorter than approximately 25 m. However, because of the size of the Fresnel

zone, (approximately 200 m), these results apply to our case. The question

now is: what value for Go should be adopted in the design of, and associated

experiments for, the SPS pilot beam system that is expected to cross the iono-

sphere at middle latitudes? There are two opposite factors that play a role in

this decision:

1. Natural ionospheric inhomogeneities at mid latitude are smaller than

at the equator and in the aurora1 zones. Vessot and Levine (1977)

measured in a mid latitude transionospheric path phase fluctuations

with rms value of about 4O at S-band on a very quiet day, with the

3-frequency gravitational red-shift rocket probe experiment that they

performed for NASA-MSFC. No data base exists, however, that would

make it possible to compute the percentage of time during which, (in

spread F events or other occurrences of mid latitude ionospheric per-

turbations), the value @o, (that typically applies to equatorial paths),

could be reached or even exceeded. However small that percentage

might be, it could be significant in the overall performance of the pilot

beam system;

2. The medium where the pilot beam will propagate in the SPS case is

expected to be heated and perturbed by the downcoming power beam.

The interactions phenomena could resemble the natural phenomena of

field aligned striations and similar structures formation occurring at

the magnetic equator and in the aurora1 zones. These are the natural

causes of the phase perturbations illustrated in Figures 2, 4 and 5.

Therefore, while waiting for the results of the ionospheric/magneto-

spheric heating experimental program (which is part of the SPS environ-

mental assessment effort), it is advisable to adopt the equatorial or the

aurora1 situations as representative of what is to be expected for the

pilot beam when the SPS high-power radiation is “on”. In other words,

it is advisable to make the assumption that the phase fluctuations in a

mid latitude transionospheric link perturbed by the SPS power beam

heating will be of similar intensity to the ones observed as naturally

occurring at the equator or in aurora-crossing transionospheric links.

A-10

It appears from the above that it is advisable, in Raytheon’s opinion, to adopt

the value i o s 40° for the expected phase fluctuations in the SPS pilot beam

system and to design a system that can cope with this expectation as well as to

design experiments that will address these parameters during the GBED program.

4. Conclusions

The ionospheric effects on the pilot beam phase stability and phase measure-

ment accuracy will not be inconsequential and require the project’s attention.

However, several approaches are potentially suited to the solution of the various

problems and could be adopted to make the pilot beam capable of operating within

rational performance specifications in the expected conditions of ionospheric bias

and stochastic fluctuations.

Developing fur the r this approach should not add to the system complexity

to the point that it could possibly lead to a potential program stoppage. On the

cclltrary, the inclusion in the system of features that would make it work under

the conditions above could only reinforce the SPS case.

5. References

Basu, S. and Kelley, M. C., “Review of Equatorial Scintillation Phenomena in

Light of Recent Developments in the Theory and Measurement of Equatorial

Irregularities, ” J. Atmos. and Terres. Physics, Vol. 39, No. 9/l2,

pp 1229-1242, 1977.

Costa, E. and Kelley, M. C., “Calculations of Equatorial Scintillation at UHF

and GHz Frequencies Based on a New Model of the Disb.lrbed Equatorial

Ionosphere, ” Geophys. Res. Lett. 3, 677-680, 1976.

Basu, Sunanda and Basu, Santimay, “Correlated Measurements of Scintillations

and In-Situ F-Region Irregularities From OGO-6,“Geophys, Res. Lett., 3,

681-684, 1976.

Fremouw, E. J. et al, “Early Results From The DNA Wideband Satellite

Experiment-Complex-Signal Scintillation, ‘I Radio Science, 13, pp 167-

187, 1978.

Vessot, R. F. C., and Levine, M. W. (1977), “A Preliminary Report on the

Gravitational Red-Shift Rocket-Probe Experiment, ” Proc. International

Symposium on Experimental Gravitation, Pavia, Italy, 17-20 September

1976.

A-11

Eshleman, ‘V. R., Gallagher, D. B., and Barthle, R. C. (1960), “Radar

Methods of Measuring the Cislunar Electron Density, I1 J. G. R., Volume 65,

pp 3079-3086, October.

Burns, A. A., and Fremouw, E. J.. , (19701, “A Real-Time Correction Technique

For Transionospheric Ranging Error, If IEEE Transactions on Antenna and

Propagation, Vol. AP-18, No. 6, pp 785-790, November.

Fagot, T., and Mague, P. (1959), La Modulation de frequence - Theorie Applicatic

aux Faisceaux Hertziens Publisher; Sot. Fran Dot Electronique, Paris, Frai

A-12

APPENDIX A

A POSSIBLE MECHANIZATION OF THE 3-FREQUENCY SCHEME

A-13

I I

A POSSIBLE MECHANIZATION OF THE S-FREQUENCY SCHEME

Figure A- 1 illustrates the simplified block diagram of one of the possible

mechanizations of the 3-frequency approach. The diagram follows closely the

Stanford University design guidelines contained in the paper by Burns and

Frcmouw (1970).

We are reminded that it is quite all right to perform arithmetic manipu-

lations on the phases of the arriving signals. This fully preserves phase

coherence, and it is currently done in ionospheric correction schemes. Figure

A-2 gives an example of the S-frequency scheme adopted by Vessot and Levine

(1977) to cancel the ionospheric bias error in their gravitational red- shift experi-

ment, conducted for NASA-MSFC. Their 3-frequency scheme characterized by

extensive arithmetic manipulations of the phases worked perfectly and the iono-

spheric bias was eliminated from the phase observations (NASA awarded to

Dr. Vessot the Gold Medal for Exceptional Achievement, in connection with this

experiment). Raytheon has no doubt that the technology exists today to imple-

ment the ionospheric correction scheme recommended for SPS in Section 2.

Literature References for Appendix A

Burns, A. A., and Fremouw, E. J., (1970), “A Real-Time Correction Technique

For Transionospheric Ranging Error, ‘I IEEE Transactions on Antenna and

Propagation, Vol. AP-18, No. 6, pp 785-790, November.

Vessot, R. F. C., and Levine, M. W. (1977), “A Preliminary Report on the

Gravitational Red-Shift Rocket-Probe Experiment, ‘I Proc. International

Symposium on Experimental Gravitation, Pavia, Italy, 17-20 September

1976.

A-14

A@A - A@,

Phase

Process01

L (Geomet ry)

s Ndl (Ionospheric

Bias)

Af

Af

Common Master Oscillator

Figure A-l. Three Frequency Approach - Simplified Block Diagram of Proposed Mechanization

A-15

Figure A-2. Schematic Concept of the Doppler-Cancelling System. (Vessot and Levine, 1977)

A-16

IONOSPHERIC COLUMNAR ELECTRON DENSITY

0 This function is a random process in the time domain. It has a non-zero

mean.

0 This mean value is called the ionospheric "bias."

0 The "bias" is slowly changing with time (1 sample every 15 minutes is an

appropriate sampling rate).

0 Superimposed to the "bias" there are random fluctuations (ionospheric

scintillation phenomenon). Typical scintillation rates are between

O.l/minute to lo/minute, requiring sampling rates of dpproximately one

every 3 minutes to one every 2 seconds respectively.

APPENDIX B

MICROWAVE POWER TRANSMISSION ANTENNA ANALYSES

I. Introduction

Antenna tradeoffs are described for the application of solid state technology

to microwave power transmission from space. The concept is illustrated in Figure

B-l. Solar Power impinges on mirrors which concentrates the sun's rays on a panel of

solar cells. The solar power is converted to DC to power solid state RF amplifiers

for subsequent beaming to earth Dl~

The excitation for the amplifier modules is derived from a pilot signal from

earth which is combined, frequency shifted, phase conjugated, and divided among

the amplifiers. The power output per GaAs FET amplifier is expected to range

between 5 and 30 watts at 80% efficiency.

The pilot signal is transmitted from the ground at several frequencies

simultaneously as listed in Table B-l, thereby averaginq the pilot electrmaonetic

transmission characteristics through the ionosphere.- The received pilot wavefront

at the spacetenna is retrodirected by dedicated phase conjugation and reference

circuitry forming a pencil beam pointed back to earth. Here a large rectenna is

used to collect the microwave power for conversion to DC and subsequent AC distribu-

tion to the utility power grid. PI, c31, r41

The beam of electromagnetic power transmitted to the ground is at 2.45 GHz

(.121 m wavelength) under the tentative constraint of 23 mW/cm' power density at

the beam peak in the ionosphere. The objective is to deliver the maximum power

to the utility grid at lowest cost without exceeding this power density.

II. Parametric Studies

The objective is to deliver to the utility grid the maximum power at the lowest

cost under the 23 mW/cm' ionospheric power density constraint. The power delivered

to the grid is given by

B-l

SOLAR CELLS (PHOTOVOLTAICS)

DC DISTRIBUTION & CONDITIONING

PHASE CONJUGATION,, ELECTRONICS , 4cQ

RF ELEMENTS / 'V& -

& AMPLIFIERS ( : % \

SUBARRAY RF COMBINER

I \I

I \ REFERENCE DISTRIBUTION

SPACETENNA

,ELAI LVL unllD DFRTnn

'1 SUN-CENTERED 'PRIMARY

REFLECTOR (PLANER)

‘> ~ .

K/;H;;\TAICS

m-a---- SECONDARY REFLECTORS

Figure B-l. Solid-State Sandwich - Typical SPS Concept

Table B-l Solid State MPTS Parameters and Constraints

FREQUENCY (TRANSMIT) = 2.450 GHz

FREQUENCIES (PILOT) = 2.301 GHz 2.550 2.799

SYNCHRONOUS ORBIT RANGE = 37x 103 kM

POWER DENSITY LIMITS

AT IONOSPHERE 23 mW/sq an

AT EDGE OF RECTENNA 1 mW/sq cm

PEOPLE SAFETY 0.1 mW/sq an

ELECTROMAGNETIC INTERFERENCE - 154 dBW/m2/4 kHz

SOLAR FLUX

NOM INAL 1350 ‘W/m2

USEFUL 820 W/m2

B-3

where PT is the total available power at the output of the active transmit ele-

ments. nB is the beam efficiency and 'no includes the atmospheric efficiency (nAT)

the array efficiency (n,), the rectenna conversion efficiency (QR,-~~), and the

power grid interface efficiency (ni).

The cost to develop this power is critically dependent on the size and weight

of the spacetenna and secondarily on the size of the rectenna and on the real

estate at the ground site. It is therefore desirable to have the smallest diameter

spacetenna with amplifier modules and radiating elements arranged to transmit at

the maximum power density.

It is also noted that the maximum power density capability of the active ele-

ments is dependent on thermal considerations which include primarily: junction

temperature, amplifier junction waste heat, waste heat from the rest of the active

element, waste heat from the DC distribution system, solar load on the microwave

side and solar cell waste heat. These are discussed more completely in Sections

6 and 8.

A uniformly illuminated aperture with each active element operating at the

same power level would satisfy this objective except for nB, the beam efficiency.

The beam efficiency is the ratio of the power subtended by a given solid angle of

the beam to the total power radiated. cw A uniformly illuminated aperture has

high sidelobes which are not collected by the rectenna, therefore wasting power and

resulting in a lower beam efficiency. Other illumination functions such as hyper-

spheroidal and Gaussian are known to result in higher beam efficiencies. c51 These

as well as uniform have been included in the parametric study; the necessary

formulas are described below.

The power density at the ionosphere is given by

'T GT 'di = 4nR 2 nAR nAT

0

(B-2)

where PT is the total power transmitted, GT the gain of the spacetenna, nAR the

array losses, nAT the atmospheric losses and R. the synchronous orbit range.

The spacetenna gain is given by

4rA, GT = x 2’ ni

0

(B-3)

B-4

where AT is the area of the transmitting antenna (AT = i DT2 for circular aperture),

X, is the transmitting wavelength and ni is the illumination taper efficiency..

The available transmitted power is

pT = PoATF (B-4)

where PO is the transmit power density at the active element and F is the power

taper factor.

It has been determined that hyperspheroidal is the illumination with the highest

beam efficiency. Gaussian illumination taper closely approximates this function

and has therefore been used in the parametric study.

The Gaussian illumination power density is given by

p = PO e-2Kr 2

This results in an available transmitted power level of

PT = ff

P e-2Kr2 rdrd$ 0

0 0

Plr PT = $-- l-e

-2KRT2

>

K is related to the edge taper B in dB and the spacetenna radius

K = .115 B 2

Rt .

F = (1 - lo-B/lo) 0.23B

and substituting for F in Equation (B-4),

PT = PO At (1 - 10-B'lo)

.23B -

(B-5)

(B-6)

(B-7)

03-a

(B-9a)

(B-9b)

B-5

The power density at the ionosphere is a function of the power available as

well as the illumination tap,er efficiency ni.

'di = 'T AT

(R x )2 nAV nAT ni 00

(B-10)

The illumination taper efficiency is given by the rat:io of the power at the peak

of the beam to the total available power in the aperture,

2 rdrd+ 1

PO At (1 - lO-B"o)

2

(B-11)

.2313

T). = 2 (1 _ 1 0-B/2~~2

1 .115B(l - l0-B'1o) (B-12)

From (B-7), (B-10) and (B-12) the diameter of the spacetenna can be determined

as follows:

DT = 2 (B-13)

The diameter of the spacetenna as a function of .the edge taper for various

element power densities is plotted in Figure B-2.

The parameters for uniform illumination are obtained from (B-10) for ni = 1

and from (B-4) for F = 1 where

and

'di = '0 AT2

(R. xo)2 nAV nAT (B-14)

DT = 2(po ';;nATj25j/F (B-15)

B-6

I - po = 525 W/M2

n (5 WATTS/tLEMENT) 2.5

iLl

3 1.0 ul

0.5

PO= 1050 W/M2

(10 WATTS/hEMENT)

PO = 2100 W/M2

(20 WATTS/ELEMENT)

PO = 3150 W/M2

(30 WiTTSbLEMENT)

-10 DB EDGE TAPER CORRESPONDING

TO 0.1 MW/CM2 AT PEAK OF FIRST

I 2

-8.5 DB EDGE TAPER CORRESPONDING TO SIDELOBE FOR PDI = 23 MW/CM

0.1 MW/CM2 AT PEAK OF FIRST SIDELOBE y; :

FOR pDI = 23 MW/CM2 I .

I :'

I 2

I I I

1 I I I I 4 6 8 1 10 12

EDGE TAPER, B (de)

Figure B-2 Spacetenna Diameter and Power Density Vs Edge Taper

which is the same result obtained by substituting 10 -B/20 y 1 - .115B + (.l15B)2

into Equation (B-13) and letting B 0 dB edge taper.

Determining the power delivered to the grid requires exploration of the second

constraint which is to restrict the power density outside of.the rectenna diameter

to be less than 1 mW/cm'. There is also a third constraint which is for the power

density outside of a fenced area to be less than 0.1 mW/cm2. This third constraint

has a cost impact associated with land acquisition. These two constraints can be

examined using similar formulations which depend on the antenna pattern of'the

spacetenna.

A circulir Gaussian illumination taper has been assumed on the spacetenna which

for 0 dB edge taper encompasses uniform illumination. For this Gaussian illumina-

tion the first sidelobe level versus edge taper is shown in Figure B-3 c81. In

Figure B-4 is plotted the angular location from the aim-axis corresponding to the

-13.6 dB (1 mW/cm' and the -23.6 dB (0.1 mW/cm2) levels in terms of

DT U = F sin 13 (B-16)

Assuming that the spacetenna line of sight is perpendicular to a plane at the

earth's surface, then the pattern of equi-amplitude contours will intersect this

plane in concentric circles whose diameter is

D = 2R, tan 8 (B-17)

From (B-16), (B-17) and (B-13),

D = (‘0~;fPATj’i’ Jvu

i

where Pd is the power density at the peak of the main lobe at the ground. i

From this equation, the rectenna diameter has been computed and plotted in

Figure B-5 versus edge taper and corresponds to the spacetenna diameters and peak

power densities listed in Figure B-2.

Examples of the far field antenna patterns and rectenna and fence locations

for uniform illumination and 10 dB Gaussian edge taper are shown in Figures 8-6

and B-7. A 10 dB Gaussian taper can use a smaller rectenna and fenced area but

requires a larger spacetenna than the corresponding uniform illumination case.

B-8

-35 -.-- -I'-,~r~~~-r---"r.~.-T l-T 1 I I I I I 1 1 .ln ," 2 16

EDGE TAPER (-dB)

Figure B-3 First Sidelobe Level for Truncated Gaussian Taper

3.

I SECOND SIDELOBE

1 -23.6 dB (0.1 mW/cm2)

2

FIRST SIDELOBE U

rc

RECTENNA - __. ._---.- - -t-----

-13.6 dB

-23.6 dB (0.1 mW/cm2)

MAIN LOBE

iDGE_+./-- - ------+

(1 mW/cm2)

U = D/X Sine for x = 0.121 m

Note: Power levels correspond to Pd = 23 mW/cm2

i

Edge Taper (B), dB

Figure B-4 Location of Power Density Limits on Ground for Gaussian Illumination Tapers at the Spacetenna

W I

-1 -I

7

i, 'di = Power Density at Lonosphere = 23 mW/cm2)

"t

3

-++. P = Pnwor bnzitv at Fdoe nf Rectenna q l.mW/cm2

--,

,_ . -J -- --=- -. ..-- -------

6 -------W PO (w/m2

------Y 3150

1050.

525.

I J

4 . ...%_ 3 --. ‘-3 42

A

A ---I

3 3 -2 I

/

I-- ---T--- - 0 ! '2' 4 '7 '--ii--

I l'o ' 12

I i I l I 14 16 18

Edge Taper (B), dB

2100.

Figure B-5 Rectenna Diameter vs Gaussian Edge Taper

-10

-14

-18

-22

-26

-30

-34

-.a5

\

\

El I

I I I I I I , .80 I I 1 I I

0 I ;I; 4;5 6 7 8 9

2.25 KM 4.6 KM

RECTENNA RA!WS, KM

Figure B-6 Rectenna Size Vs Beam Efficiency - Uniform Illumination

10 dB TAPER

J Es k 5

-16-

-2o-

-24

m13.6 dB _

-23.6 dB

I I I ,I” /-ii’ PATTERN

1, / ;:

1

I I I I I I I I 0 1 2 3 4 5 6 7 8

) <2 4 km RECTENNA RADIUS, km.

2.03 km (Rectenna Radius) (site Radius)

Figure B-7 Rectenna Size vs Beam Efficiency - Tapered Illumination

.85

.80

One other antenna pattern related quantity in the power grid formula of

Equation (B-l) is the beam efficiency. For the uniform case the rectenna would

collect 82.5% of the available radiated power while the 10 dB Gaussian taper case

would collect 95% of the available radiated power.

The parameters for uniform illumination and for -10 dB taper are summarized in

Table B-Z. The tapered case requires a 30% larger spacetenna to deliver 23% less

power than uniform; the rectenna diameter is 11% smaller and approximately 27% of

the land area is required. The costs for the land facilities are less but the

spacetenna and the transportation costs will be much greater. The cost comparison

is covered in a parametric format in Section 3.10.

Based on the above parametrics the uniformly illuminated spacetenna was

selected as a baseline.

As indicated earlier in this appendix, thermal considerations must be included

in the evaluation of an optimum design. These are covered in Sections 6 and 8.

Also certain land use aspects play an important role in the antenna system

selection.

Concerning this latter item, it became of interest to reduce the first and

second sidelobes in the uniformly illuminated patterns; the first to bring in the

fence thereby requiring less land use and the second to demonstrate that power

densities of lower than 0.1 mW/cm* were achievable outside the fenced area. In

order to accomplish these goals in a practical implementation, a single step taper

was investigated.

Results of the single step taper investigation are reported in Appendix C.

B-14

Table B-2

Comparison Between Uniform and -10 dB Gaussian Taper for Spacetenna

--__- Antenna

Illumination

Uniform

Gaussian

- 10 dB

DT (km) I-----

‘T (GW) 1.95 1.568

2.545 1.045

P (W

1.072

0.823

- T

DR (km) DS (km)

4.5 9.2

4.0 4.8

B-15

References

[1] Finnell, W., "MSFC Solid State SPS Concepts and Design Description," Material from presentation at NASA Headquarters, February 22, 1979.

[2] Brown, W.C., "The Technology and Application of Free Space Power Transmission by Microwave Beam," Proc. IEEE, Vol. 62, No. 1, January 1974.

[3] Brown, W.C. and O.E. Maynard, "The Adaptation of Free Space Power Transmission Technology to the SSPS Concept," AIAA/AAS Solar Energy for Earth Conference, #75-642, April 1975.

[4] Nalos, E.J., "New Developments in Electromagnetic Energy Beaming," Proc. IEEE, Vol. 66, No. 3, March 1978.

[5] Borgiotti, G.V., "Design of Circular Apertures for High Beam Efficiency and Low Sidelobes," Alta Frequenza, Vol. XL, 1971.

[6] Borgiotti, G.V., "Maximum Power Transfer Between Two Planar Apertures in the Fresnel Zone," Vol. AP-14, No. 2, March 1966.

[7] Sherman, J.W., "Properties of Focused Apertures in the Fresnel Region," Vol. AP- , July 1962.

[8] Barton, D.K. and H.R. Ward, "Handbook of Radar Measurement," Prentice-Hall, 1969.

[9] Kay, A.F., "Near Field of Aperture Antennas, Vol. AP- , November 1960.

[lo] Goubau, G., "Microwave Power Transmission," Journal of Microwave Power, Vol. 5, No. 4, 1970.

[11] Young, L., "Advances in Microwaves," Academic Press, Vol. 3, 1969.

[12] Maynard, O., "Microwave Power Transmission System Studies," NASA CR-134886, December 1975.

B-16

APPENDIX C

SINGLE STEP TAPER

The object ive of investigat

pattern sidelobes. Reduction of

ing the single step taper was to reduce spacetenna

the first sidelobe would result in requiring less

real estate at the fenced-in rectenna site and reduction of the second and other

sidelobes would demonstrate that power densities lower than 0.1 mW/cm' were achiev-

able outside the fenced-in area.

The single step taper illuminaton is illustrated in Figure C-l. This is con-

sidered to be a practical illumination which can be implemented using active ele-

ments operating at two different power levels.

The step taper illumination has been designed so that the power density at the center of the spacetenna aperture and power density at the peak of the beam are

equal to those obtained with uniform illumination. This requires an increase,in

aperture diameter (2k2a) to offset the step in aperture voltage (C); the inner

diameter of the step being 2k,a.

By equating the power at the beam peak for the uniform and step taper cases,

the illumination parameters are related as follows:

1 k2 =

- k12(l - C)

C

1 1 7/2

1 - k22C

kl = 1-c

For example, if C = 0.4 and k, = 0.8, then k2 = 1.24 which results in a 24%

increase in aperture diameter. This is derived as follows:

Uniform:

E,(o) = 1~ a2 (c-2)

C-l

STEP TAPER

/ -..A

I -. . 1 +a --i a --.- 4

- k2a --4

RADIAL DISTANCE

Figure C-l Spacetenna S,tep-Taper Aperture Illumination

c-2

Step:

k2a 2n kla 2lT

E(o) Is C rdrd$ =

I (1 - C) rdrd$

0 0 0

E,(o) = r(k2a)2C + n(k,a)2(l - C)

when EU(o) = E,(o),

1 = k22C + k,2(l - C)

(C-3)

K-4)

(C-5)

and Equation (C-l) is obtained.

The far field pattern for a uniformly illuminated circular aperture

2 J,(u) E(u) = u (C-6)

and the corresponding patterns for the single step taper are obtained by super-

imposing uniform illumination patterns of the step of amplitude C and the

amplitude 1 - C with the following results:

E(u) = 2 k 2C !!(u2) + 1 - C k,2 J,(u,)

2 0 u1 1 where

2na u ___ = x sin 8

u1 = k,u

u2 = k2u

When C = 1, k2 = 1 then Equation (C-7) is the pattern of a uniformly

illuminated circular aperture, as shown-in Figure C-2.

step of

(C-7)

(C-8)

(C-9)

(C-10)

Examples of the patterns obtained by stepping the illumination under the

above constraints are shown inFigure C-3. Here"power steps of l/3 and l/4

-c-3

I I I ---- I

:: ti e I. i . 0.00 ‘4.00 KC0 12.00 16.00 zb.00

u SPfm

k, = 1.0000

k2 = 1.0000

:: pc.i w

E J

Q m 3

z d

B %z co . . co e. 00 lZ.UO lI.CJ 2b. co

u SPRCE

Figure C-Z Antenna Pattern - Uniform Illumination

c-4

TRANSMITTING ANTENNA

0

c!n KEY:

UN IFORM POWER D ISTRIB~ION

--- l/3 STEP AT EDGE

------ l/4 STEP AT EDGE

-mm 0 4 8 12 16 20

U SPACE I I ,,,,,,,, ,,,,I1 0 3 6 9 12 15 RADIUS KM (FOR D, = 1.95 KM

x =O.l2M R = 37,000 KM)

% = POWER CENSITY AT

TRANSMITTING ANTENtiFj

% = DIAMETEE AT TRANSMITTING

AliTENNA FOR UN IFORM POV.‘ER DlSTRl5UTlON

U SPACE

u lrDu SlNe

=\

X = W&E LiNGiH

8 = SEAM WIDTH (HALF ANGLE)

Figure C-3 Sidelobe Comparison of Uniform Power Distribution With Two Examples of Single Step Edge Taper

(.58 and .5 voltage) result in significant second sidelobe reduction (between 5

and 10 dB) with a resulting increase in aperture size of between 8.9% and 13%.

The lower power region of the spacetenna diameter has excess potential solar

cell area which can be used to provide power for inboard active elements. The

thermal and power distribution considerations that permit this redistribution of

power are discussed in Sections 6 and 8.

- Another characteristic of the single step taper is that it results in a re-

duction in available power as compared to the uniform case as follows:

'TT _ k 2(, -- 'TU 1

- c2) t C2k22 (c-11)

where

'TT = Total transmitted power in the tapered case;

'TU = Total transmitted power in the untapered case.

The results of applying this formula are shown in Figure C-4 where the

available power ratio is plotted versus the spacetenna diameter ratio for various

amplitude steps. For the cases shown in Figure C-3 the.available power is 91% for

the l/3 power step and 85% for the l/4 power step as compared to that available

for uniform illumination.

Formula (C-12) for the available power has been derived by integrating the

power in the circular aperture:

kla 21T k2a 27T

P = II

(1)2 rdrd$ + II

C2 rdrd+

0 0 0 0

(C-12)

The remaining pattern characteristic to be evaluated is beam efficiency.

This has been computed relative to the uniform case. The power collected for

uniform illumination versus pattern angle is determined from the beam efficiency

f( 2 f$)' wdw n U

YA =

'AV (c-13)

C-6

where w = (2na/x) sin 8 and Pvu = ma' is the power available for 1 volt amplitude.

The uniform illumination far field pattern is

E(w) 2 J,(w)

= 2.1ra _ _ W

(c-14)

The power collected for the step taper case relative to uniform is determined from

the step taper beam efficiency, '

1 2

t (1 - C> K,2 J,(w,)

w1 wdw

P vu

where w 1 = k,w and w2 = k2w.

The relative efficiency of the step taper case is

nsr

k22 C J1(w2) (1 - C)k12 J,b,) I 2

wdw

% w2 w1

z-z X j’( J;i

0

) 2

wdw

(c-15)

(C-16)

and w' ranges from 0 to + 20. -

The numerator approaches the power available ratio in the limit as plotted

in Figure C-4.

The antenna

voltage step rat

from 1 to 1.6 as

patterns and relative efficiency rat

ios between .2 and .8 over a range of

shown in Figure C-5.

o have been plotted for

spacetenna diameter ratios

Sidelobe envelopes and efficiency nTA are presen ed in Figures C-6 , C-7

and C-8 for power tapers of .04, .@I and .I6 respectively.

Figure C-9 shows the efficiency nTA due to the step-tapered aperture power

distribution. For uniform power distribution the first sidelobe is at -17.4 dB.

The dotted curve shows the combinations of C2 and k2 to reduce the first sidelobe

to -23.6 dB, thus eliminating the need for fences out of the main lobe. There

c-7

_ .__--.-

0.8

0.7

0.

I ---I ‘\

C=O.4 - -_

\,,.

c=o.3

I

. . . ‘.. \. \ ‘\

‘\.

“\ c=o.2

I 6j_a ..__ _ -__ __._. --- _._. __ ._. _ __ -. _ “”

1.0 1.1 12

SFiiENNA Ri, FACTO,';i

._. -- I

1.5

I

Figure C-4 Step Taper Power Ratio Vs Radius Factor

C-8

C = 0.20

kl = 0.9000

k2 = ] .3266

C = 0.20

kl = 0.9500

k2 = 1 .I790

C = 0.20

kl = 0.9000

k2 = ] .3266

k2 = 1.1790

Figure C-5 Near-In Sidelobe and Relative Efficiency Data

c-9

:: d

n C = 0.'20

\, kl = 0.8000

k2 = 1.5620

iiiL U SPRCE

C = 0.20

kl = 0.8500

k2 = I.4526

r I

;: ‘c. aa 4. CO I?. co 1z. CO 16. co 7x2. ca

u srficc

111 . a;

C = 0.20

kl = 0.8000

k2 = 1.5620

CC ’ 4.co e. 00 12. co 16. co 2b. co iJ SPRCE

C = 0.20

kl = 0.8500

k2 = I.4526

Q I

Lc I l . ca !z.ca re. ca zs.ca * za. cc u YRCE

Figure C--5 I-- Continued

c-10

= 0.30 = 0.9000 = 1.2014

C

kl

k2

. . . / '

\

/” ‘1 :li’

co ! 4: 00 e: co Ai. 00 Iii. 00 2b. co U SPWE

C = 0.30

k = 1 0.9500‘

k2 = 1.1079

Jl-/---- 4.co 8. co 12.00 16.00 2’0. co

U SPRCE

x +oo I rlco 8. co 12.00 16.00 2’0. co

U SPRCE

kl = 0.9500

k2 = 1.1079

ii b. oniqr:co --e: co-

1 12. co 16.00 20. Cd %V” 4. co I?. co 12. co 16. cc 2’0. co

U SPFlCE u SPIICE

Figure C-5 -- Continued

c-11

a

C = 0.30

kl = 0.8000

k2 = 1.3565

0 0.00 Ii. 00 lb. 00 zil. 00 u SPACE

C = 0.30

kl = 0.8500

k2 = 1.2835

5

a

E d

c = 0.30

kl = 0.8000

k2 = 1.3565

c = 0.30

kl = 0.8500

k2 = 1.2835

\ 00 14.00

1 I. co LP. 00 II. 00 PO. co U SPACE


c-12

C = 0.30 kl = 0.7000 k2 = I -4799

3 ‘0.00 ! 4.00 6. co AZ. co 16.00 20. 1 co

U SPFICE

n,

C

k 1

k2

f

\

= I.4216

J

\

r

4.00 6. co iz. co J SPACE

16. co

/’ I: z’; w

-2. co

L” ri

Q

d

c d

c = 0.30 '

kl = 0.7000

k2 = 1.'4799

8 co I 4.co 8. co 12. co 16. co 20.

u SPRCE co

C = 0.30

kl = 0.75

k2 = I.4216

c ‘J-‘I-...

-.- -

0 1 4. cc 8. co 12. co 16. co 20. I co U SPRCE


c-13

1 7

C Z 0.40 kl = 0.9000 k2 = 1.1336

co

c = 0.40

kl = 0.9500

k2 = 1.0706

1

?ii 8. co 12. co lb. co 20. co U SPflCE

k = 1 0.9500 k = 1.0706 2

4. co B.CR 12. cc 16. cc 20. co %co ‘4Ico *. co 12. co 16. cc A. LIP U SPfICE u SPf7CE


c-14

0.40 = 0.8000

1.2410'

c = 0.40

kl = 0.8500

k2 = 1.1901

IO 4.00 I

6. co 12. co 16. co 20. co u SPflCE

$ ‘0.00

I . ’ 4. co n. 00

u SPRL2

n

c = 0.40 kl = 0.8000 k2 = 1.2410

C = 0.40 kl = 0.8500 k2 = 1.1901

on ’ 4.co 8.00 12. co 16. CO 2b. co u SPIKE


c-15

c = 0.40

kl = 0.7000 = 1.3285

b’ cc s’--- i SPIKE

IZ.

C = 0.40

kl = 0.7000

k2 = i.3285

is.cco. 00 QCO 4.00 0. co 12.00 ID. 00

1 20. cc U SWICE

c = 0.40

kl = 0.7500

k2 = 1.2870

C = 0.40

kl = 0.7500

k = 2 1.2870

0 1 d

E 6

8. I %oo ’ (‘CO e.co 12.00 II. co 2;. co

u SPflCF. Figure C-5 -- Continued

C-16

C = 0140

kl = 0.6000

k2 = 1.4000

8 d 9, ’ i la.00 4.00 8.00 12.00 16.00 20.00 U SPRCE

C =* 0.40

kl = 0.6500

k, = 1.3661

C = 0.40

kl = 0.6000 k2 = 1.4000

I I ch.00 I .

I ‘. 00 8.00 12.00 16.00 20.00

u SPACE

C = 0.40

kl = 0.6500

k2 = 1.3661

d P 1

coo '

4.00 8.00 12.00 18.00 20.00 t!ih

4:oo 8'00 AZ. I

i SPACE 00 16.00 ZP. 00

u SPRCE


c-17

iz 8

&

0.00 4.00 0.00 12.00 16.00 20. co u SPACE

C = 0.50

k, = 0.9500

8 d 4

0.00 : 4.00 0.00 12.00 16.00 u SPRCE

00

-=-rr = 1..090? k2 k2 = l..O90?

I

;; 8.00 12.00 lb. 00 20.00 U SPRCE

k, = .0.9500


c = c = 0.50 0.50

C-18

C = 0.50

k, = 0.8000

k, = 1.1662

E d

i B 5.00 4. co a. 00 I 17.00 16. co

20. co U SPACE

c = 0.50

kl = 0.8500

k, = 1.1303

Figtire,C-5 -- Continued

ci Y 0. co 4. co 8.00 1 P2. co 16. co

U SPACE 20. co

:: B.00 4.co t!. 00 12.00 16.CO 2b. co

U SPRCE

c-19

.-__--

C = 0.50

k, = 0.7000

k2 = 1.2288

ri u I 0.00 4. co 0.00 12.00

U SPRCE lb.00 2a.w

c = 0.50

k, = 0.7500

k2 = 1.1990

D n.co 12.00 U SPACE

lb.00 ab. co

C = 0.50

k, = 0.7000

k2 = 1.2288

d .-.-

I? d

I d

z I =i?w ’ * 4. co 8.00 12.00 rkw

u SPRCE zb. co

C = 0.50

k, = 0.7500

k2 = l.lwo


c-20

n,

C = 0.50

k, = 0.6000

k2 = 1.2806

n

4: 00 s: 00 ii?. 00 U SPIXE

lb. 00 2b. 00

c = n-_

k, = 0.6500

k2 = 1.2560

U SPRCE .co 20. co

Figure C-5

c = 0.50

k, = 0.6000

= 1.2806 k2

;; 4. co a. 00 12.00 16. OO- PO. co

U SPIXE

c = 0.50

k, = 0.6500

k2 = 1.2560

-- Continbed U SPACE

c-21

c = 0.50

k, = 0.5000

k, = 1.3229

c = 0.50

k, = 0.5000

k2 = 1.3229

iti ,

10 4.00 8.00 AZ. 00 16.00 20.00 5.4 U SPACE

1 4. 00 I). 00 12.00 16.00 20. co

U SPRCE

c = 0.50 c = 0.50

k, = 0.5500

k2 = 1.3029

k, = 0.5500

k2 = 1.3029

L I. 01

I- DO 4.00 KC0 12

U SPRCE 8

D 16. CO 20.co U SPACE


c-22

c =

k, =

k2 =

0.60

0.8000

1.1136

ia,-L 6.00 12.00 16.00 20. co U SPFlCE

9

C = 0.60 .; C = 0.60

k, = 0.8500

k2 = 1.0886

k, = 0.8500

7 : d

s:

P 9 n

1 ‘ci

IL

u-l -m d

0

d

z d

$ ::

‘C. 00 4. co 6. CO ii. co 16. CO 2h. cc P. #- u SPRCE 00 4. co B. co 12.00 16.CI 26. co u SPRCE

C = 0.60

:: ci

::

8.00 4.00 8.00 12.00 16.00 2;. co U SPRCE


C-23

C = 0.60

kl = 0.7000

k2 = i.1576

C = 0.60

k, = 0.7500

k2 = 1.1365

0” %. 00 4. co 6. co 12. co ~6.00 I

U SPACE 20. co

C = 0.60

kl = 0.7000

k2 = 1.1576

z 400 4. co 6.00 12.00 16.00 -I ,

U SPRCE 20. co

r” ci

c =

k, =

k2 =

0.60

0.7500

1.1365

B: co 4. co 6. co co 1 12. 16. co U SPRCE

20. co


C-24

C = 0.60

k, = 0.6000

k2 = 1.1944

z ‘0.00

I I 4. co 6. co 12. co 16.CO 20. co

U SPFICE

C =

k, =

k2 =

C = 0.60

kl = 0.6000

k2 = 1.1944

-

0.60

0.6500 : <

1.1769

2 5. 4. co 6.00 12. co is. co 20. co

U SPRCE

ii!00 ’ ’ 4. co 8. co 12. co 16.00 - u SPACC: 20. co


C-25

C = 0.60

k, = 0.6500

k2 = 1.1769

I , I ! 4.co 8.00 12. co 16. co I

U SPRCE 20. co

IO 4. cc E I

c =

k, =

k, = L

-I I. co 12.00 U SPRCE

c =

k, =

0.70

0.9000

1.0399

I 16.00 2O.CQ

0.70

0.9500

1.0207

k, = 0.9000

k2 = 1.0399

0 a9 l-0 W

E! ci

U SPRCE

1 lZ.CO 16.00. 2o.co 4: co s: co

U SPflCE

c = 0.70

k, = 0.9500

k2 = 1.0207

4.co n. co 12.00 16.CO 20. co U SPRCE

\ Figure C-5 -- Continued

C-26

zoo 4.00 8.00 12.00 20. co U SPFlCE

e d

:: d

P 5. co 4.00 e. 00 12. co 1c. co A. co

u SPRCE


C-27

c = 0.70

k, = 0.8000

k2 = 1.0744

8 6 7 0.00 4. co 6. co 12.00 16.00 7

20. co u SPRCE

2

=i?co I

4.00 6. co 12.00 lb. co 20. co U SPACE


C-28

C = 0.70

kl = 0.7000

k2 = 1.1039

U SPFKE

c = 0.70

k, = 0.7500

k2 = 1.0897

:: d P c.00 4. co 0. co 12. co 16. cc t

20. co U SPRCE

k, = 0.7000

8 5.

co 4. co a. cc 12. co 16. co 1

20. co u SPACE

4. co 8. co I 12.00 16.00 20. co u SPRCE


c-29

C = 0.80

k, = 0.9000

k2 = 1.0235

0 P

c. co 4. co a.00 I

12.00 16. co 20. co u SPRCE

c = 0.80

k, = 0.9500

k, = 1.0121. L

s :c. co 4. co 8. co 12. cc 16. cc 2;. co

u SPRCE

--: - c = 0.80

k, = 0.9000

k2 = 1.0235

4. co 8. co I 12. co 16.CO

U SPACE 20. co

..-_

C = 0.80

kl = 0. 950,o

k2 = 1.0121

;I._ 4. cc B.CO 12. cc 16. cc 2k. co

u SPRCE


c-30

C = 0.80

k, = 0.8000

k2 = 1.0440

P IO. 00

, 4.00 0.00 12.00 18.00 70.00

u SPACE

C = 0.80

k, = 0.8500

k2 = 1.0341

0.00 12.00 u SPRCE

C = 0.80 C = 0.80

k, = 0.8000 = k, 0.8000

k2 = 1.0440

=i? 00 4. co 0.00 12.00 16.00 20. # co U SPACE

C = 0.80 C = 0.80

k, = 0.8500 k, = 0.8500

k2 = 1.0341 k2 = 1.0341

z d

P ci

::

+A 00 4.00 0.00 II. 00 16.00 20. PO u SPRCE


c-31

I -

C = 0.60

k, = 0.9000

I d 7, 6

a. 00 ,. 00 0.00 12. a0 16. co 20. co U SPIXE

C = 0.60

k, = 0.9500

k2 = 1.0320

:: ‘c. OP 4.00 0.00 12.00 16.00 PP. 00

U SPRCE

c = 0.60

k, = 0.9000

k2 = 1.0614

P coo 4.00 0.00 12.00 IS. 00 20.00 1

U SPFlCE

C = 0.60

k, = 0.9500

k2 = 1.0320

s

=i!,O 4.00 0.00 1% OP 16.00 OP. 00 u SPFlCE


C-32

Peak Sidelobe Power Relative to Main Lobe

(23 mW/cm2)

'First Sidelobe dB Vs k2

Third Sidelobe dB Vs k, ‘\

y-=

*@A Fourth Sidelobe dB Vs k2

- -\.. -

---k... Fifth Sidelobe dB Vs k2

“1,. -'. ._

-

--

a 0 I 7 A ;

u

/ I

O/

I k2 = 1.468

, at -25 dB k2 = 1.396

\ ' /

Tapered Spacetenna Radius k iJniform Spacetenna Radius = 2

6

Figure C-6 Sidelobe Envelope and Efficiency For .04 Power Taper

c-33

KEY

ffiricnrv n-. V< k- I “TA - - “2

x 3

0

-10

-20

Peak Sidelobe Power -x

Yirst Sidelobe dB Vs k2

Relative to Main Lobe

Second Sidelobe dB Vs k2

(23 mW/cm') \‘=-. y Third Sidelobe dB Vs k2

nTA = 0.894 for -24 dB -. --. _-.- --- ---

---J 1.0

4.8 dB Margi - - - ". -Q .___ _

--“o.,. .. -23.6 dB\, ' .,.

_ -_ = 0.86 fo; -28.2 dB --'

(.l mW/cm2 1

41 \' .m _ .-- - -, H

= 1.2835

at -24 dB \

, I I \ I d = 1.325

j l k2 for -28.2 dB (min)

I 1.6

Tapered Spacetenna Radius = k \ Uniform Spacetenna Radius 2

Figure C-.7 Sidelobe Envelope and Efficiency For O.OgPower Taper

c-34

KEY

Peak Sidelobe Pdwer Relative to Main Lobe

J23 mW/cm')

fficiency nTA Vs k2

Yirst Sidelobe dB Vs k2

'Second Sidelobe dB Vs k2

'Third Sidelobe dB Vs k2 .

--I----, -. -. M- Foul

1 --=A.. .- \c . . x-.

rth Sidelobe dB Vs k2 1.0

‘t9 Fifth Sidelobe dB Vs k,

-I \ - .-I

n,. = 0.89 for -23.6 dB -I- -

-._ _-. -. ------ 0.84 for. -28 dB

@ k2 = 1.23

at -23.6 dB

i , . ~~~-,-,~ ,I:. j7’r-~’ , , . ,,~n~~~:;~T~6 . . . . Tapered Spacetenna Radius = k Uniform Spacetenna Radius 2

Figure C-8 Sidelobe Envelope and Efficiency For 0.16 Power Taper

c-35

1 .oo

3

0.80

1

---m-s q.A VERSUS k 2 FOR FREE SPACE SIDELOBES 23.6 dB DOWN FROM

PEAK OF MAIN LCBE WITH ZERO dB MARGIN

vTA VERSUS k2 FOR MAXIMUM MARGIN BELOW 23.6 dB DOWN

dB MARGIN MAXIMA FOR NEAR-IN SIDELOBES ---

NOTE 1: 10.6% PENALTY IN nTA COMPARED TO UNIFORM (1 ST SIDELOBE

REDUCED FROM -17.4 d6 TO -23.6 d8)

NOTE 2: ADDITIONAL 3.4% PENALTY IN r+A TO ACHIEVE MAXIMUM (4.76 dB) OF MAXIMA MARGINS BELOW -23.6 dB

f ------

/* i 7

AT SINGLE STEP FOR AT SINGLE STEP FOR POWER DENSITY AT POWER DENSITY AT PEAK OF MAIN LOBE PEAK OF MAIN LOBE SAME AS FOR UNIFORM SAME As FOR UNIFORM

: 1 : 1

-4

-3

-2

,l

TAPERED SPACETENNA RADIUS k UNIFORM SPACETENNA RADIUS = 2

Figure C-9 Single Stepped Taper Aperture Efficiencies and Sidelobe Margins Relative to Uniform

C-36

is no dB margin included in the dotted line , while the solid line shows the

combinations of C2 and k2 to achieve the maximum margin in sidelobes below the

-23.6 dB point.

In that the cases for C = 3, 4 and 5 show significant potential for near in

sidelobe control, the performance at further out sidelobes was investigated. As

shown in Figures C-10 and C-11 the further out sidelobes are well behaved.

A glossary of terms is given in Table C-l.

The power delivered for the step taper (PDT) can be obtained from

'DT = nT nil 'TT

k12U - C2) + C2k2 (C-17)

where n T is the beam efficiency for the tapered case referenced to uniform

pDT -- nT = PD (C-18)

U

is the power delivered for uniform illumination which is obtained from

nu the uniform illumination beam efficiency where

pDU X

=-

pTU

(c-19) ,

pTU is the total available power for uniform illumination on the spacetenna. The

available power for the step taper is less than this as follows:

pTT = PT (k12(l - C2) + C2k22) (C-20)

II

and

'DT = nT nu 'Tu (c-21)

c-37

s z '0. 00 4. 00 6. 00 I 12.00 16.00 20.00

U SPRCE

\

c = 0.30

k, = 0.8188

\ k, = 1.3300 L L

Figure C-10 Typical Near-In Sidelobe and Relative Efficiency Behavior

C-38

c = 0.30

k, = 0.8188

k2 = 1.3300

c = 0.40

k, = 0.7579

k2 = 1.2800

c = 0.30

kl = 0.8188

k2 = 1.3300

c = 0.40

k, = 0.7579

k2 = 1.2800

e d

g 0

:: %. co I 20. cc 40. co 80. co 80. co 100. co

u SPFlCE

Figure C-11 Typical Far Out Sidelobe and Relative Efficiency Behavior

c-39

c = 0.50 k, = 0.6614

k2 = 1.2500

c = 0.50

k, = 0.6614

k2 = 1.2500

Figure 11 -- Contjmued

c-40

Table C-l Glossary of Terms

C Step Amplitude t:

;i.j a Spacetenna Radius 1 !. ',.I I!. kl Fractional Radius (Beginning of Step)

:I 9

k2 Fractional Radius (End of Step)

\ (Modified Spacetenna Radius)

1 4 i) U-Space U = (27ra/x) sin 8

1; x

1

Operating Wavelength !nA iit 0 1 Angle Off Boresight of Spacetenna

h ? Eta (nr) Ratio of Beam Efficiencies Between Step Taper (ns) and Uniform (nu

nr =

+u

/ P Ratio of Total Available Power for Step Taper Illumination to Uniform

Illumination (Constraint is 23 mW/cm' at Beam Peak)

(1) First Sidelobe Peak

(2) Second Sidelobe Peak

(3) Third Sidelobe Peak

(4) Fourth Sidelobe Peak

c-41

1) 8) APPENDIX D 1,

h DESIGNS, CONSIDERATIONS AND ISSUES

j, $1 '&

The Progress Report on Solid State Sandwich Concept presented at Lyndon B.

Johnson Space Center in Houston, Texas on 15-18 January 1980 is incorporated in

total.

D-l

-

PROGRESS REPORT ON SOLID STATE SANDWICH CONCEPT

- DESIGNS, CONSIDERATIONS AND ISSUES -

Owen E. Maynard

Raytheon Company, Equipment Division

Presented At

Solid State Configurations Session of the SPS Microwave Systems Workshop 15-18 January 1980

Lyndon B. Johnson Space Center, Houston, Texas

ABSTRACT

Progress in analysis and design of solid state approaches to the SPS

Microwave Power Transmission System is reviewed with special emphasis on the

Sandwich concept and the issues of maintenance of low junction temperatures

for amplifiers to assure acceptable lifetime. Ten specific issues or considera-

tions are discussed and their resolution or status is presented.

Introduction and Background

Investigations of Microwave Power Transmission System (MPTS) concepts by

Raytheon in the past have not addressed solid state approaches due primarily

to the problem of trying to achieve long life ( 30 years) in an application

where high power density and limited waste heat dissipation capabilities are

inherent.

Solid state amplifier efficiencies for the current technology are too low

(50% to 70% range) requiring 50 to 30% of the DC power to be radiated as waste

heat while keeping junction temperatures within acceptable limits. Recent

projections of solid state amplifiers have indicated that the efficiency may

be as high as 80%, requiring 20% of the DC power to be radiated as waste heat

reducing the problem by a factor close to 2.

Solid state amplifiers operate at low voltage, 20 V, compared to 20 kV

to 40 kV for tubes and the DC power transmission and conditioning system

weights, complexities and cost for known overall system concepts were of major

concern for kV power distribution systems and incredible for low voltage

systems. The solid state sandwich concept, where the DC power distribution is

a simple grid interface with the static microwave portion of the sandwich, is

such that investigation of the solid state approach became of considerable

interest. D-2

Results have been encouraging and the concept is considered to warrant I further and more in-depth investigation. The critical outstanding issues

include the need for demonstration of the high efficiency for the amplifiers.

1,' When this is accomplished, the issues and considerations discussed herein become

important.

4i ,G ii

Results of Investigation by Raytheon for NASA-MSFC _=_-~-- {:i ;4 ff

I(

Raytheon's investigation has included the following tasks:

'i 1. Definition and Math Modeling of Basic Solid State Microwave Devices r "! 2. Initial Conceptual Subsystem and System Design

1, 3. Sidelobe Control and System Selection

ICI 4. Assessment of Selected System Concept

F'ir 5. Parametric Solid State MPTS Data Relevant to SPS Concept

j! j An efficiency goal for the DC to RF amplifiers of 80% has been established. 1' I Although this has not been demonstrated it is considered to be a realistic goal

and is therefore the basis for the investigation. Parametric data for 75% and

85% are included.

Conceptual subsystem and system design investigations resulted in the

following:

(a) .1.95 km diameter transmitting antenna having uniform power density

of 500 W/m2 (RF);

(b) 4.5 km beam diameter or minor axis rectenna having maximum power

density of 23 mW/cm2;

I (c) Free space sidelobes < 0.1 mW/cm' for 2nd and further out sidelobes;

(d) First sidelobe above 0.1 mW/cm2 out to the fenced minor axis of

9.2 km;

(e) Subarray size 32 x 32 elements 3.2m x 3.2m;

(f) Microwave subsystem for spacetenna weight of ~3 kg/m2;

(g) DC to DC efficiency of 0.51;

(h) Total transmitted power of IT x41*g5L x 500 x lo6 = 1.493 x 10' W RF

(i) DC power into antenna = 1.493 x log .99 x .99 x .8 x .96 x .98 =

1.493 x log .738

= 2.02 x 10' W DC

D-3

I. -

(j) Power out of rectenna to power grid = 1.49 x 10' x .98 x .825 x .89 x .97

= 1.04 x 10' W DC

(k) Antenna concept is one amplifier/transmitting antenna element (narrow

bandwidth) with element printed on tape l/4 X from ground plane.

Receiving antenna elements are wide bandwidth and are orthogonal to

the transmit elements to minimize adverse coupling.

(1) Waste heat is passively radiated to deep space from pyrographite

radiators having E = 0.8 and c1 = 0.05 thermal control coatings.

Waste heat ( 500 W/m2) from the photovoltaic array is assumed to add

to the heat load on the microwave side.

(m) Single step taper at the transmitting antenna was investigated to

determine sensitivity for reduction of 2nd sidelobe. Significant

reduction is achievable with single step.

(n) Further parametric investigations indicate that the RF power per

element may be increased from 5 W/element to 6, thus permitting a

significant reduction in spacetenna diameter for the same power den-

sity on the ground.

(0) Further detailed investigation of the concept is warranted.

Issues/Considerations

The issues and considerations along with their resolution and status,

shown in the attached table, have evolved during the investigation. Each of

them will be discussed in turn in the oral presentation and copies of the

visual aids will be made available.

D-4

-

SOLID STATE SANDWICH CONCEPT

DESIGNS AND ISSUES

OWEN MAYNARD

RAYTHEON COMPANY

AT

NASA JSC

15-18 JANUARY 1980

CENTRAL PHASE REFERENCE

t

PHASE RERERENCE DISTRIBUTION

PHASE

SOLID STATE MPTS SPACETENNA SUBARRAY CIRCUIT DIAGRAM

32:l POWER COMBINER

I 134 SUN

‘ORS

1

AMPLIFIER (1) In

CONJUGATION CIRCUITS (1)

i 32:l POWER COMBINERS (32)

/ /

/

RF

DRIVER AMPLIFIER (1)

I:32 POWER DIVIDER

PILOT PASSIVE RECEIVER

t OUT

SPACETENNA - DIPOLE CONCEPT

GROUNDP’LANE y

PRELIMINARY ESTIMATES OF POWER TRANSMISSION AND CONVERSION EFFICIENCY CHAIN

r --- DC POWER FROM PHOTOVOLTAIC ARRAY

1 . PHOTOVOLTAIC

-ARRAY POWER y SLIP RINGS ANTENNA DC TO RF

*POWER =-CONVERSION L DISTRIBUTION DISTRIBUTION

.9368 .9995 .963 .85 I

.98 N.A. .85

.99 N.A. .99 .80

ITRANSMITTINGJ ~ATM~SPHERIC 1 63 - * 'ANTENNA -LOSSES ENERGY

,COLLECTION

.9653 .98 .88.

.98 .98 .79

.96 .98 . . 98 ,825 ,

7

RECTENNA GRID POWER OUT DC POWER FROM -ENERGY -1 NTERFACES I - OF GRID PHOTOVOLTAIC ARRAY

CONVERSION

.89 .97 NASA REF CONCEPT (KLYSTRON) .55

.89 :97 MSFC SOLID STATE (MAY 1979) .54

.89 .97 RAYTHEON SOLID STATE STUDY .51 .

ISSUES/CONSIDERATIONS

LOW VOLTAGE DISTRIBUTION

HARMONIC AND NOISE SUPPRESSION

SUBARRAY SIZE

MONOLITHIC TECHNOLOGY

LIFETIME

MUTUAL COUPLING

INPUT TO OUTPUT ISOLATION

CHARGED PARTICLE RADIATION EFFECTS

TOPOLOGICAL CONSIDERATIONS

SIDELOBE SUPPRESSION

ISSUES/CONSIDERATIONS RESOLUTION/STATUS

o LOW VOLTAGE DISTRIBUTION FURTHER REFINEMENT REQUIRED TO MINIMIZE lrlEIGHT AND CONTROL THERMAL LEAKAGE


SUBARRAY SIZE


LIFETIME

MUTUAL COUPLING




SIDELOBE SUPPRESSION

DC POWER CHARACTERISTICS OF SANDWICH

o DC POWER FROM PHOTOVOLTAIC BLANKET (PVB) TRANSMITTED TO POWER DISTRIBUTION LAYERS

(+ GRID, - GROUND PLANE) (CONDUCTOR LENGTHS 40 CM).

o NEAR-UNIFORM VOLTAGE DIFFERENTIAL IS AVAILABLE CLOSE TO ALL USING EQUIPMENT ACROSS A

SUBARRAY (75 V NOMINAL). LOCAL POWER CONDITIONING PROVIDED AT EACH AMPLIFIER MODULE.

o DC CONDUCTOR INCLUDING GROUND PLANE CROSS SECTIONS AND WEIGHT KEPT SMALL TO MINIMIZE

"UNCONTROLLABLE" HEAT TRANSFER TO RF DEVICES HAVING LOWER CRITICAL JUNCTION TEMPERATURES

THAN THOSE ASSOCIATED HITH PHOTOVOLTAIC PORTION OF SANDWICH.

- TRANSFER OF POWER BETWEEN SUBARRAYS IS LIMITED BY GENERAL HEAT TRANSFER LIMITS

AND BLOCKAGE FROM WASTE HEAT RADIATION POINT OF VIEW.

- TRANSFER OF POWER FROM POWER GRID AND GROUND PLANE TO USING EQUIPMENT IS BY SHORT

(DESIGN CONTROLLED) CONDUCTORS WITH BUILT-IN FUSES TO ISOLATE EQUIPMENT OVER-CURRENT

FAILURES FROM THE POWER GRID AND GROUND PLANE.

m SPECIFIC WEIGHT OF GROUND PLANE IS .005 GM/WATT AND OF GRID IS .002 GM/WATT

(WATTS ARE DC FROM PVB) FOR A SUBARRAY.


o LOW VOLTAGE DISTRIBUTION

o HARMONIC AND NOISE SUPPRESSION FREQUENCY ALLOCATION NEEDS AT HARMONICS SHOULD BE CONSIDERED OR CONSIDER SPREAD SPECTRUM At'!D ACTIVE SUPPRESSION

l SUBARRAY SIZE

o MONOLITHIC TECHNOLOGY

o LIFETIME

l MUTUAL COUPLING

o INPUT TO OUTPUT ISOLATION

o CHARGED PARTICLE RADIATION EFFECTS

l TOPOLOGICAL CONSIDERATIONS

m SIDELOBE SUPPRESSION

HARMONIC NOISE GENERATION, SUPPRESSION AND TRANSMISSION CHARACTERISTICS

o NOISE FILTERS ARE PROVIDED AT THE ELEMENT MODULE LEVEL ON TRANSMIT AND AT THE SUBARRAY

CONJUGATING ELECTRONICS LEVEL ON RECEIVE.

e RESIDUAL NOISE IS NON-COHERENT BETWEEN SUBARRAYS.

o RESIDUAL HARMONICS MAY PERIODICALLY BE COHERENT OVER TOTAL TRANSMITTING ARRAY.

o NOISE AT EARTH IS ESTIMATED AS -181 DBW/M*/4 KHZ.

o HARMONIC POWER DENSITY AT EARTH IS ESTIMATED AS -66 DBW/M2 AT 3RD HARMONIC AND LESS

AT HIGHER HARMONICS. GRATING LOBES FOR LOWER HARMONICS DO NOT INTERSECT THE EARTH.

o FREQUENCY ALLOCATION AT 3RD AND HIGHER HARMONICS SHOULD BE CONSIDERED. SPREAD SPECTRUM

AND ACTIVE SUPPRESSION CONCEPTS SHOULD BE INVESTIGATED AS POSSIBLE MITIGATING APPROACHES.


l LOW VOLTAGE DISTRIBUTION

o HARMONIC AND NOISE SUPPRESSION

o SUBARRAY SIZE 3M x 3ri MAY BE CLOSE To OPTIMUM, FURTHER STUDY OF IMPLEMENTATION REQUIRED I


l LIFETIME

o MUTUAL COUPLING


l CHARGED PARTICLE RADIATION EFFECTS

o TOPOLOGICAL CONSIDERATIONS

o SIDELOBE SUPPRESSION

SIJBARRAY CHARACTERISTICS

THE FOLLOWING HAVE BEEN CONSIDERED IN SIZING OF THE SUBARRAY:

TOPOLOGICAL CONSIDERATIONS TO MINIMIZE ELEMENT SPACING (MAXIMIZE TRANSMITTED

POWER DENSITY), MINIMIZE DIVISIONS OF DRIVE POWER (MAXIMIZE EFFICIENCY) AND

PROVIDE FOR OTHER FUNCTIONS WITH MINIMUM LAYERING (MINIMIZE INTER-LAYER

CONNECTIONS) RESULTED IN A BASELINE SIZE OF 3.2M x 3.2M.

SUBARRAY STEERING AND POINTING CONSIDERED SATISFACTORY.

ARRAY FLATNESS CONSIDERED TO IMPOSE NO OVER-RIDING ISSUES.

REMAINING COMPLEXITIES ARE PRIMARILY IN PACKAGING,

BETWEEN SUBARRAYS.

THERMAL AND INTERFACING

KNOWN SPECIFIC WEIGHT ("3 KG/M") FOR 3.2M X 3.2M SUBARRAY MAY BE REDUCED BY 1%

FOR 6.4M x 6.4M SUBARRAY WHILE POSSIBLE COMPLEXITY, HANDLING AND LOSSES NULLIFY

THE KNOWN ADVANTAGE.

LOSSES UNIQUE TO THE SUBARRAY ABOVE THE ELEMENT CELL LEVEL (ELEMENT SPACING 10 CM)

HAVE BEEN ESTIMATED TO BE < 0.5%.

NEAR-I:! SIDELOBE INCREASES DUE TO THE SUBARRAY HAVE BEEN ESTIMATED TO BE (0.2 DB.


l LOW VOLTAGE DISTRIBUTION


@ SUBARRAY SIZE 4

o MONOLITHIC TECHNOLOGY MONOLITHIC APPROACHES APPLY AND REQUIRE TECHNOLOGY DEVELOPMENT FOR MINIMIZATION OF COST AND WEIGHT

o LIFETIME

o MUTUAL COUPLING



l TOPOLOGICAL CONSIDERATIONS


MONOLITHIC TECHNOLOGY FOR THE SANDWICH

0 THE GENERAL CONCEPT OF MONOLITHIC TECHNOLOGY TO INCORPORATE MULTIPLE FUNCTIONS INTO

ONE SERIES OF PROCESS AT BOTH THE AMPLIFIER LEVEL AND AT THE ANTENNA LAYER LEVEL IS

THE.SELECTED APPROACH FOR HIGH PRODUCTION RATE AND LOW COST PURPOSES.

7 @ TOTAL SANDWICH CONCEPTS INCLUDE INTERCONNECTIONS BETWEEN LAYERS AND BETWEEN z SUBARRAYS.




o SUBARRAY SIZE


RESOLUTION/STATUS

a LIFETIME LIFETIME AFFECTED BY JUNCTION TEMPERATURE LIMITS AND CHARGED PARTICLES RADIATION REQUIRING TECHNOLOGY DEVELOPMENT IN BOTH AREAS.

7 o MUTUAL COUPLING z





LIFETIME CONSIDERATIONS

LIFETIME GOAL IS 30 YEARS WITH LOW PROBABILITY OF FAILURE.

PRIMARY FAILURE MECHANISMS RELATE MOST DIRECTLY TO JUNCTiON TEMPERATURE.

RANGE OF INTEREST FOR JUNCTION TEMPERATURE IS 100°C TO 150°C REQUIRING ADVANCED

TECHNOLOGY DEVELOPMENT FOR LONG LIFE.

HEAT GENERATION AT AMPLIFIER DEVICES IS PRIMARY CONTRIBUTOR TO HIGH JUNCTION

TEMPERATURE. ADVANCED TECHNOLOGY DEVELOPMENT REQUIRED FOR HIGH EFFICIENCY.

HEAT TRANSPORT FROM DEVICE TO WASTE HEAT RADIATOR IS A MAJOR SANDWICH DESIGN

CONSIDERATION INVOLVING:

- HIGH CONDUCTIVITY MATERIALS

- DEDICATED REGIONS FOR WASTE HEAT RADIATION TO COLD SPACE

- HIGH EMISSIVITY AND LOW ABSORPTIVITY THERMAL CONTROL SURFACES TO MAXIMIZE WASTE

HEAT DISSIPATION WITHOUT EXCEEDING LONG-LIFE JUNCTION TEMPERATURES

MATERIALS AND COATINGS MUTUAL TECHNOLOGY DEVELOPMENT GOALS HAVE BEEN ESTABLISHED

- MATERIALS SUCH AS PYROLYTIC GRAPHITE, HAVING HIGH THERMAL CONDUCTIVITY, IN

CONJUNCTION WITH HIGH PERFORMANCE THERMAL CONTROL COATINGS NEED TECHNOLOGY

DEVELOPMENT TO ASSURE INTEGRITY AND PERFORMANCE OF HIGH EMISSIVITY AND LOW

ABSORPTIVITY SURFACES.

- WHERE WEIGHT IS NOT A SIGNIFICANT FACTOR COPPER MAY BE SATISFACTORY.

OPTIMIZATION TOOLS HAVE BEEN CONCEIVED TO MAXIMIZE THE ABILITY OF THE TOTAL

SANDWICH TO TRANSMIT HIGH POWER DENSITY.

l- AMPLIFIER JUNCTION TEMPERATURE VS WASTE HEAT

‘J (“0

'-200 E = 0.8 Thermal Control k-190 a = 0.05 Coating Wt = 1.59 gm

180-

160-

-180

-170

-160

-150

-140

-130

-120

-110

-100

- 90

Dia = 8.66 cm

t root = 1.0 mm

ttip = 0.1 mm

Thermal Conductor

(gm) Wt.

Aluminum 6.35 -.------ Copper 20.94 ----- Pyrographite 5.29

60

TJ = Amplifier Junction Temperature

PA = Waste Power Generated at Amplifier Junction q

PB = Waste Power w/mL - Uniform Over Thermal lY-J2-I-.- rtaa iaixr.

' = Incident Solar Power P Conditions - F

' (1300 W/m')

Radiation Cooling - To Absolute Zero

P I I I I -/ 1 2 3 4 I 5

-20

v '

PA (WATTS)

c c,

-; c. \ - . . I I A

350

300

250

T('C)

200

160 150

140 131 122 114

ACCELERATED LIFE DATA AND PROJECTIONS

FOR SOLID STATE SPS MPTS STUDY

I I I ll I I I . . . I I I I I 1 I I 1 I I I I

1.6 ' \ --- I

; \y \ RAYTHEON AL

q \ -- -- _.._ _ 1' - - -- -. \ \ \ --- _ -- I I

REFERENCE MTTF DATA MSC TT W A,,

Al.8 --- - \ I I

1 1000/T

7 i2.4

\t

\i .42.6

100~~ , , l , , , , , I‘;‘ <I\‘=:;L&y 10 lo2 lo3 lo4 lo5 I lo6 lo7 lo8

TIME TO FAILURE (TTF) 22v-t 12 10 20 30 YEARS

HOURS

o PYROGRAPHITE RADIATORS (8.66 CM DIA) o AMPLIFIER EFFICIENCY = 0.8 o DC TO RF EFFICIENCY = 0.7377

(WATTS

T = EFFECTIVE

'RF pA

CbNCENTRATION

(WATTS ) PROBABILITY OF SURVIVAL RATIO FOR:

i

r FOR AMPLIFIER JUNCTION %

' 50 i

PDc TS = TS =

- T, ('C) = AMPLIFIER JUNCTION TEMPERATURE (WATTS) 2oo"c 250°c \I cl

160 L 201~ r t

18

i-16

-10 -12

'- 10 -8

-8

-6

-6

l I I I 1 ---1- ’

-12

-. 10

8

-6

-4

-2

-0 r)

-4 -4

-2 -2

co t-0 0 200 400 600 800 PB W/ML

PB = THERMAL POWER FROM SOLAR CELLS RADIATED FROM MICROWAVE ARRAY




e SUBARRAY SIZE

m MONOLITHIC TECHNOLOGY

o LIFETIME

RESOLUTION/STATUS

o MUTUAL COUPLING IMPLEMENTATION BY PRINTED DIPOLES SPACED FROM GROUND PLANE WITH BALUN IN CIRCUITRY AND CLOSE ELEMENT SPACING TO MINIMIZE DETRIMENTAL MUTUAL COUPLING EFFECTS





MUTUAL COUPLING CONSIDERATIONS

o ELEMENT SPACING (0.8 X) TO SUPPRESS GRATING LOBES.

o PHYSICAL IMPLEMENTATION OF DIPOLES SUPPORTED ABOVE (0.25 X) GROUND PLANE

TO PREVENT SURFACE WAVE RESONANCES AND PROVIDE BALUN ACTION.

o DIPOLES AND TRANSFORMERS INCORPORATED IN CIRCUITRY USED FOR IMPEDANCE MATCHING

IN PRESENCE OF MUTUAL COUPLING AMONG ELEMENTS.



RESOLUTION/STATUS -

a HARMONIC AND NOISE SUPPRESSION

e SUBARRAY SIZE

a MONOLITHIC TECHNOLOGY

o LIFETIME

o MUTUAL COUPLING CJ I k? o INPUT TO OUTPUT ISOLATION ORTHOGONAL DIPOLES, OFFSET FREQUENCIES

AND FILTERING PROVIDE SATISFACTORY ISOLATION OF TRANSMIT FROM RECEIVE SIGNALS

l CHARGED PARTICLE RADIATION EFFECTS




0 TRANSMIT AND RECEIVE DIPOLES ARE ORTHOGONAL TO MAXIMIZE INPUT/OUTPUT ISOLATION.

0 SEPARATE PILOT FREQUENCIES FROM FUNDAMENTAL (OUTSIDE HIGH NOISE BAND).

l FILTERING PROVIDED ON PILOT RECEIVER WILL BE IMPLEMENTED AT THE PHASE

CONJUGATION NETWORK AT THE SUBARRAY LEVEL.




o SUBARRAY SIZE


l LIFETIME

o MUTUAL COUPLING


RESOLUTION/STATUS

o CHARGED PARTICLE RADI'ATION EFFECTS GaAs IS CURRENTLY BEST TECHNOLOGY (REQUIRES MORE ADVANCEMENT IN "MECHANISMS" OF FAILURE)


@ SIDELOBE SUPPRESSION

0

0

0

0

CHARGED PARTICLE RADIATION EFFECTS/CONSIDERATIONS

VAN ALLEN BELT DISTRIBUTION OF ELECTRONS GEOMAGNETICALLY GO OUT TO 40-50K NAUTICAL

MILES. NO SINGLE PEAK BUT VARIES IN TIME.

11 YEAR SOLAR SUNSPOT CYCLE RESULTS IN CHARGED ELECTRONS AND PROTONS HAVING POSSIBLY

SIGNIFICANT EFFECTS.

SOLAR WINDS RESULT IN LOW ENERGY ELECTRONS HAVING MUCH SMALLER EFFECTS THAN CHARGED

PARTICLES TRAPPED IN VAN ALLEN BELTS.

GaAs MESFETS TEND TO BE HARDEST OF EXISTING TECHNOLOGIES.

TEST RESULTS ARE NON-CONCLUSIVE RE FAILURE OR DEGRADATION MECHANISMS AND EFFECTS OF

PROTECTIVE SCHEMES.

SELECTION OF GaAs TECHNOLOGY AND SHIELDING APPEAR TO BE MOST EFFECTIVE APPROACH

AT PRESENT.

ADVANCED TECHNOLOGY DEVELOPMENT REQUIRED TO ADDRESS MATERIALS, FAILURE MECHANISMS

AND PROTECTIVE SCHEMES.

ISSUES/CONSIDERATIONS -


l HARMONIC AND NOISE SUPPRESSION

a SUBARRAY SIZE


o LIFETIME

o MUTUAL COUPLING

l INPUT TO OUTPUT ISOLATION


RESOLUTION/STATUS

o TOPOLOGICAL CONSIDERATIONS REQUIRED FUNCTIONS CAN BE IMPLEMENTED IN SANDWICH CONCEPT. FURTHER DETAILS AT SUBARRAY BOUNDARIES REQUIRED.



TOPOLOGICAL CONSIDERATIONS HAVE BEEN GIVEN AT THE TOTAL ARRAY, PHASE DISTRIBUTION SYSTEM,

SUBARRAY AND ELEMENT MODULE LEVELS.

STRUCTURAL SUPPORT FOR THE ARRAY IS CONSIDERED TO BE PROVIDED BY MAJOR STRUCTURAL

RING AT PERIPHERY WITH TENSION GRID ASSURING RELATIVE FLATNESS. GRID MEMBERS ARE

CONSIDERED TO BE SMALL WITH RESPECT TO SANDWICH THICKNESS AND DO NOT SHIELD RF OR

WASTE HEAT RADIATION.

MECHANICAL SUPPORT AT SUBARRAY BOUNDARIES ARE REQUIRED LARGELY FOR HANDLING,

INSTALLATION AND REPLACEMENT PURPOSES. DETAILS OF HOW SUBARRAYS WILL BE MATED TO

PRECLUDE ADVERSE DISCONTINUITIES ARE YET TO BE DEVELOPED.

RF TRANSMIT ELEMENT LATTICE IS MAINTAINED IN REGION OF SUBARRAY EDGES TO MINIMIZE

SYSTEMATIC ERROR SIDELOBES.

FREE RADIATION OF WASTE HEAT FROM RADIATORS NEAR SUBARRAY EDGES IS COMPROMISED

REQUIRING CUSTOMIZED EDGE TREATMENT TO MAXIMIZE THE EFFICIENCIES OF THE THERMAL

RADIATORS AT THE EXPENSE OF WEIGHT AND COST. FURTHER INVESTIGATION IS REQUIRED.

'ISSUES/CONSIDERATIONS RESOLUTION/STATUS

LOW VOLTAGE DISTRIBUTION


SUBARRAY SIZE


LIFETIME

MUTUAL COUPLING




o SIDELOBE SUPPRESSION SINGLE STEP EDGE TAPER MAY BE REQUIRED J

SIDELOBE SUPPRESSION CONSIDERATIONS

UNIFORM VERSUS 10 DB GAUSSIAN ILLUMINATION AT SPACETENNA RESULTS IN THE FOLLOWING:

ADVANTAGES FOR UNIFORM DISADVANTAGES FOR UNIFORM

- SMALLEST TRANSMIT ANTENNA - LOWER POWER BEAM EFFICIENCY

- ALL AMPLIFIER MODULES OPERATE AT SAME - HIGHER SIDELOBES (-17 DB, -24 DB, -28 DB

POWER LEVEL BELOW 23 MW/CM2 AND MORE LAND REQUIRED TO

- EASY TRANSFER OF DC VOLTAGES FROM SOLAR FENCE RECTENNA

ARRAY (IF DENSITY TAPERING IS EMPLOYED

TO APPROXIMATE GAUSSIAN ILLUMINATION

THEN DC DISTRIBUTION AND SOLAR ARRAY

ARCHITECTURE BECOMES COMPLEX AND HEAVIER)

SINGLE STEP TAPER VERSUS UNIFORM (CONSTANT POWER DENSITY AT EACH LEVEL)

ADVANTAGES FOR STEP DISADVANTAGES FOR STEP

- LOWER SIDELOBES (-28 DB BELOW 23 MW/CM2) - LESS POWER AVAILABLE

- ALL AMPLIFIERS OPERATED AT SAME POWER - LARGER SPACETENNA

LEVEL

SIDELOBE COMPARISON OF UNIFORM POWER DISTRIBUTION

WITH TWO EXAMPLES OF SINGLE STEP EDGE TAPER t-- 0.85 D,---

I I ‘” ‘” D

KEY:

UNIFORM POWER DISTRIBUTION

--- l/3 STEP AT EDGE ---__- l/4 STEP AT EDGE

-20 -

-3o- a 7J g -4o-

2 -50;

-60 -,

-70 j

l-1.1303 D, -1

ITTING ANTENNA

P” = POWER DENSITY AT TRANSMITTING ANTENNA

DU = DIAMETER AT TRANSMITTING

ANTENNA FOR UN IFORM POWER DlSTRlBUTlON

U SPACE

U lrDu SIN0

=-

X = WhE LENGTH I

-1 I

8 = BEAM WIDTH -80

(HALF ANGLE) 1 I I I I

0 4 8 12 16 20 U SPACE

I I , , , , , , , , , , , , , , 0 3 6 9 12 15 RADIUS KM (FOR D, = 1.95 KM

j, =O.l2M R = 37,000 KM)

SUMMARY AND CONCLUSIONS SOLID STATE SANDWICH CONCEPT ISSUES AND RESOLUTION SUMMARY


LOW VOLTAGE DISTRIBUTION FURTHER REFINEMENT REQUIRED TO MINIMIZE WEIGHT AND CONTROL THERMAL LEAKAGE

HARMONIC AND NOISE SUPPRESSION FREQUENCY ALLOCATION NEEDS AT HARMONICS SHOULD BE CONSIDERED OR CONSIDER SPREAD SPECTRUM AND ACTIVE SUPPRESSION

SUBARRAY SIZE 3M X 3M MAY BE CLOSE TO OPTIMUM, FURTHER STUDY OF IMPLEMENTATION REQUIRED

MONOLITHIC TECHNOLOGY MONOLITHIC APPROACHES APPLY AND REQUIRE TECHNOLOGY DEVELOPMENT FOR MINIMIZATION OF COST AND WEIGHT

LIFETIME LIFETIME AFFECTED BY JUNCTION TEMPERATURE LIMITS AND CHARGED PARTICLE RADIATION REQUIRING TECHNOLOGY DEVELOPMENT IN BOTH AREAS

MUTUAL COUPLING IMPLEMENTATION BY PRINTED DIPOLES SPACED FROM GROUND PLANE WITH BALUN IN CIRCUITRY AND CLOSE ELEMENT SPACING TO MINIMIZE DETRIMENTAL MUTUAL COUPLING EFFECTS

INPUT TO OUTPUT ISOLATION ORTHOGONAL DIPOLES, OFFSET FREQUENCIES AND FILTERING PROVIDE SATISFACTORY ISOLATION OF TRANSMIT FROM RECEIVE SIGNALS

CHARGED PARTICLE RADIATION EFFECTS GaAs IS CURRENTLY BEST TECHNOLOGY (REQUIRES MORE ADVANCEMENT IN "MECHANISMS" OF FAILURE)

TOPOLOGICAL CONSIDERATIONS REQUIRED FUNCTIONS CAN BE IMPLEMENTED IN SANDWICH CONCEPT. FURTHER DETAILS AT SUBARRAY BOUNDARIES REQUIRED.

SIDELOBE SUPPRESSION SINGLE STEP EDGE TAPER MAY BE REQUIRED.

AMPLIFIER THERMAL MODEL

I ?G - PYROGRAPHITE (with CUBER)

--w--m Cu - COPPER RADIATOR

T°C --_I_ n 1 - ALUMINlltl RAeQIATC)R

JUNCTION TEMPERATURE = TJ "N TE + 9 Pp, ' A

Al

T PG "

-rT

DIA = 10 Ctl

TC = 1.0 MM

TT = 0. 1 :1b!

p,4 =4w

pB = 100 W/M2

C-Y. = 0.05

E = 0.8

11.9 13 22').2 fl pc/w) \ pA

\ _----

-w--, - -_ -I I

FIN CENTER

-NJ FIN TIP

I I u 1 1 1 I I I , I

13 +4 5 78 9 10 11 12 13 14 15

\

6

MODEL ELEtlENTS ALONG RADIATOR RADIUS

JUNCTION

16 17

RECTENNA SIZE VS BEAM EFFICIENCY - UNIFORM ILLUMINATION

-10

% -14

; iii 4

2 -18

-34

\ I -13.6dB -------

II 82.5% EFFICIENCY ----

% II G! \I

1 2 i 3 4 i 5 6 7 8 9

2.25 KM 4.6 KM

.80

RECTENNA RADIUS, KM

mE (MINUTES) LEFT

.Ol

1.0

1.0

1.0

0.5

1.0

1.0

0.5

0.5

2.0

3.0

l.D

1.0

1.0

0.5

0.5

1.0

1.0

1.0 1.0

SOLID STATE SANDWICH CONCEPT DESIGNS AND ISSUES

VUGRAPH NUMBERS AND SCREEN LOCATIONS

L2

L2

L6-1

L6-2

L6-3

L6-4

L6-5

L12

L12

L12

L6-5

L6-6

L6-7

L6-8

L6-9

L6-10

CENTER --

Cl

C4

c5

c7

C8

c9

Cl0

Cl1

Cl1

Cl4

Cl4

Cl6

Cl7

Cl8

Cl9

c20

c22

RIGHT

R3

R3

R3

R3

R3

R13

R13

R15

R15

R3

R3

R13

R13

R21

1. Report No. 1 2. Government Accession No. 1 3. Recipient’s Catalog No.

NASA CR-3339 I I 4. Title and Subtitle I 5. Report Date

Solid State SPS Microwave Generation and Transmission Study Volume II - Phase II Final Report Appendices

November 1980 6. Performing Organization Code

7. Author(s) I

8 Performing Organization Report No.

Owen E. Maynard ER80-4074-2 10. Work Unit No.

9. Performing Organization Name and Address

Raytheon Company Equipment Division Advanced Development Laboratory Wayland, MA 01778

M-312 11. Contract or Grant No.

NASB-'33157 lj. Type of Report and Period Covered

2. Sponsoring Agency Name and Address National Aeronautics and Space Administration Contractor Report Washington, DC 20546 14. Sponsoring Agency Code

5. Supplementary Notes

NASA Marshall Technical Monitor: Charles Guttman Final Report

6. Abstract

The purpose of this investigation was to further define the solid state sandwich concept for SPS. The design effort concentrated on the spacetenna, but did include some system analysis for parametric comparison reasons. The study specifically included definition and math modeling of basic solid state microwave devices, an initial conceptual subsystems and system design, sidelobe control and system selection, an assessment of selected system concept and parametric solid state microwave power transmission system data relevant to the SPS concept. Although device efficiency was not a goal of this study, the sensitivities to design of this efficiency were parametrically treated. Sidelobe control consisted of various single step tapers, nultistep tapers and Gaussian tapers. A preliminary assessment of a hybrid concept using tubes and solid state is also included. I'here is a considerable amount of thermal analysis provided with emphasis on sensitivities to waste heat radiator form factor, emissivity, absorptivity, amplifier efficiency, material and junction temperature.

Fhe document is organized to provide useful design data for future studies, identify issues associated with the solid state sandwich design, and estimate technology requirements.

7. Key Words. (Suggested by Author.(s) 1 18. Distribution Statement SPS Microwave Dipole Subarray Solid State Sandwich Efficiencv Unclassified - Unlimited ?ower Balance Tapered Illumination ?ower Density RF Radiating Element jpacetenna Gaussian Pilot Receiver icrowave Power Transmission Svs (MPTSJ 9. Security Classif. (of this report) 20. Security Classif. (of this page)

Subject Category 44 21. No. of Pages 22. Price

Unclassified Unclassified 113 A06

For safe by the National Technical Information Service, Springfield, Vrrgrnra 22161 NASA-Lang1 ey , 1980

Documents

Solid State SPS Microwave Generation and Transmission Study€¦ · Owen E. Maynard CONTRACT NASS-33157 NOVEMBER 1980 . TECH LIBRARY KAFE, NM ll~ll~lllul~Il~lIMII#l~~l 0062038 NASA