Section 11.0

Communications Subsystem

Victor J. SankCommunications Lead Engineer

5Space Technology

“Tomorrow’s Technology Today”GSFC

ST5 PDR June 19-20, 2001

ST5 PDR June 19-20, 2001

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Agenda• Key Requirements

• Documentation

• Allocations

• Transponder, Diplexer and HPA Layout

• System Concept Design

• Link Budgets

• Antenna

• Block Diagram

• Development

• Testing

• Issues

• Back-up Slides

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System Requirements• S/C shall implement X-band communications link with the ground. (MRD

10104040)

• The spacecraft shall be able to downlink telemetry and receive uplinked commands. (MRD 10303060)

• The transponder system shall be capable of decoding “special/hardware" commands from the uplink without the use of the CDH or FSW and execute discrete pulse signals to other units on the spacecraft. (MRD 10303062)

• The spacecraft shall have two, ground selectable, downlink data rates; 1Kbps and 100Kbps. (MRD 10303063)

• The spacecraft shall be able to support 2-way radiometric Doppler tracking. The system radiometric Doppler tracking accuracy shall be sufficient to support ground antenna pointing at distances of 2 to 5 Re. (MRD 10301010 and MRD 10301011)

• The spacecraft shall provide a minimum RF output power of 1.5 W, measured at the antenna port of the diplexer. (MRD 10303067)

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Derived Requirements• 10MB HK and Science data playback plus RT HK in

25-30 min contact

• 11m Ground Antenna (minimum)

• Convolutional coding on telemetry , r = 1/2, K = 7

– Due to the use of 1/2 rate convolutional encoding, the necessary symbol rate (in kilosymbols per second, Ksps) is twice the required data rate (in kilobits per second, Kbps).

• Coherent RF turn around using CCSDS recommended ratio

• Stable oscillator

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DocumentationCommunicationSubsystem

Specification

ST5-495-023 Preliminary

X-Band Transponder SOW

ST5-495-004 21DEC00

X-Band TransponderSpec

ST5-495-003 14MAR01

X-Band TransponderMechanical ICD

ST5-495-041 Preliminary

X-Band TransponderElectrical ICD

ST5-495-042 Preliminary

X-Band Antenna ICD

ST5-495-047 Preliminary

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System Allocations• Mass

– Transponder Unit .198 Kg– Front End Unit (Dplxr & HPA) .210 Kg– Antenna .120 Kg– System Total .528 Kg

• Volume – Transponder Unit 187.5 cm3

– Front End Unit 80.0 cm3

– Antenna 157.5 cm3

• DC Power– Rcvr Only 4 W – Rcvr and Xmtr 12 W

• Thermal Operate Survive– Transponder, HPA & Dplxr -20 to 50 °C -40 to 60 °C – Antenna -60 to 40 °C -80 to 80 °C

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Transponder, Diplexer and HPA Layout

Transponder

(2.95 x 2.45 x 1.97 in)

Diplexer

(3.3 x 1.1 x 0.5 in)HPA

(3.0 x 1.5 x 0.6 in)

Scale: 3”

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Communications System Design Concept (1 of 2)

• Performance

– Two Data rates baselined; 1 and 100 Kbps

– At <5Re Data transfer of 100Kbps with a BER of <1X10-5

– Two-way, Coherent Doppler Tracking is baseline

– One-way Doppler will provide backup orbit determination

• Other Attributes

– 5V transponder, excluding HPA

– HPA mount point minimizes thermal variation at Oscillator

– X-band Uplink and Downlink

– 3 dB margin in Telemetry link budget

– >20 dB in Command link budget

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Communications System Design Concept (2 of 2)

• Frequency and Spacecraft ID Registration (MRD 30104000)

– NTIA Frequency allocation approval; currently Stage 2

• X-band 8470.000 MHz downlink, 7209.125 MHz uplink

• S-band 2263.000 MHz, 2084.000 MHz

– CCSDS GSCIDs assigned; minimum Hamming distance 4; (used to uniquely identify spacecraft in CCSDS frame header)

• ST5-1 0011100000 E0• ST5-2 0001011110 5E • ST5-3 0010011011 9B

– SOMO/CSOC SCIDs assigned (for ground handling of data)• ST5-1 0100011 23• ST5-2 0100100 24• ST5-3 0100101 25

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Link Budget: X-band Space – Ground (1 of 2)

1 Transmitter Power (W) 1.9 2.79 dB2 Antenna gain (dB) 0.003 SC Antenna beamwidth (°) 40.00 FWHM4 Passive Loss (dB) 1.0 cables, etc.5 EIRP (dBW) 1.79 31.79 dBm6 Freq. (MHz) 84707 Range (km) 32000 5Re8 Space loss (dB) 201.119 Atmos, Scint, Rain Att (dB) 0.9 high elevation10 Polarization loss (dB) 1.511 Rcvd power den (dBW/m2) -162.0112 Rcvd PSD over 4 KHz -181.91 convo coded

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Link Budget: X-band Space – Ground (2 of 2)

13 Ground antenna size (m) 11 36.09 ft 14 Antenna gain (-surf loss)(dB) 56.92 55% eff15 Antenna beamwidth (deg) 0.22 FWHM16 Power Received (dBm) -115.00 Bkg Temp 40K17 Antenna to LNA Loss (dB) 1.00 diplexer Temp 75.0918 LNA gain (dB) 25 N=1.2dB, T=92.29K19 System temp (deg K) 231.28 23.64 dB K20 System G/T (dB/K) 33.27 L14 - L1921 C/No (dB-Hz) 59.86 L12 + L 20 + 228.622 Data rate (bps) 100000 50dB (N = -

154.96dBw)23 Implementation loss (dB) 2.4 Rcvr and BS24 Avail Eb/No (dB) 7.46 L21 - L23 - L2425 Eb/No required (dB) 4.4 10E-5 coded (4.2

ideal)26 Avail margin (dB) 3.06 Line 24 - Line 25

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Link Budget: X-band Ground – Space (1 of 2)

1 Transmitter Power (W) 5.0 6.99 dB2 Antenna gain (dB) 55.8 11 m3 SC Antenna beamwidth (°) 0.26 FWHM4 Passive Loss (dB) 1.0 cables, etc.5 EIRP (dBW) 61.79 91.79 dBm6 Freq. (MHz) 7209.1257 Range (km) 32000 5Re8 Space loss (dB) 199.719 Atmos, Scint, Rain Att (dB) 1.4010 Polarization loss (dB) 1.011 Rcvd power den (dBW/m2) -102.2112 Rcvd PSD over 4 KHz -102.11

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Link Budget: X-band Ground – Space (2 of 2)

13 Space antenna size (m) omni14 Antenna gain (-surf loss) 0.015 Antenna beamwidth (deg) 40 FWHM16 Power Received (dBm) -110.69 Bkg Temp 40K17 Antenna to LNA Loss (dB) 1.00 diplexer Temp 75.0918 LNA gain (dB) 25 N=3 dB, T=288.63K19 System temp (deg K) 315.45 Bkg 40. dB K20 System G/T (dB/K) -24.96 L14 - L1921 C/No (dB-Hz) 62.82 L12 + L 20 + 228.622 Data rate (bps) 1000 30dB (N = -173.43 dBW)23 Implementation loss (dB) 2.4 incl mod & diff coding24 Avail Eb/No (dB) 30.42 L21 - L23 - L2425 Eb/No required (dB) 9.6 10E-5 uncoded26 Avail margin (dB) 20.82 Line 24 - Line 25

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ST5 Quadrafilar Helical Antenna

Operating Frequency: 8.47 GHzLHCPDiameter: 0.150 inchesLength: 1.125 inchesTurns: 1

Trace: copperDielectric core: EccoStock LoK(Dielectric Constant =1.7)

Notes:There are four traces in the dielectric core. Traces are 90° apart from each other. Traces do not touch each other. Drawing not to scale.

Beamwidth +20 to +60º from eclipticReceive Gain 0dB Transmit Gain 0dB

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Antenna Gain (Stand alone)

ST5 Quadrifilial Helical Antenna

-30

-25

-20

-15

-10

-5

0

5

Angle (Deg)

LHCP RHCP

(Ga

in in

dB

)

-180

-160

-140

-120

-100

-8

0

-6

0

-4

0

-2

0

0

2

0

4

0

6

0

8

0

100

120

140

160

180

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Antenna Gain with Choke Rings

ST5 Ideal Antenna with Choke Ring

-50

-40

-30

-20

-10

0

10

-180

-155

-130

-105 -80

-55

-30 -5 20

45

70

95

120 145

170

Degree

Ga

in (

dB

)

LHCP RHCP

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Transponder Functional Block Diagram

Downlink Telemetry from C&DH

Transponder Mode Control from C&DH

Rx/Tx Status Output to C&DH

UpLink Lock to C&DH Cmd Decoder

Auxiliary Command Inputs

C&DH Data

C&DH Clock

+7.2Vdc +5Vdc

Diplexer

Transponder Controller

Special Command Detector

Receiver

TransmitterHPA

Tx

RxCoherent Reference

Telemetry

Status

Control

Command

Status/Control

Front End Units Transponder

LO Generator

Oscillator

X-band Up/Down

LNA

SpecialCmd reset

Downlink Clock to C&DH

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Transponder RF Block Diagram

113

244

636

LoopFilter

LoopFilter

LoopFilter

9.625 MHzTCVCXO

DIPLEXER

SP

LIT

TE

R

DR

V

LNA VGABPF BPF

BPF LPF

VE

CT

OR

MO

DU

LA

TO

RZ

ER

O-I

FR

EC

EIV

ER

BASEBAND PROCESSOR

6121.5 MHz

2348

.5 M

Hz

1087

.625

MH

z

2348.5 MHz8470.0 MHz

7209.125 MHz 1087.625 MHz

AGC

RX I

RX Q

TX Q

TX I

FROM BASEBANDPROCESSOR

Front-EndAssembly

TRANSMITTER

RECEIVER

C-BAND SYNTHESIZER DUALSYNTHESIZER

RX

CO

ND

ITIO

NIN

G

TR

AC

KIN

G

REFERENCETUNING

TX

CO

ND

ITIO

NIN

G

C&DHINTERFACE

SPECIALCOMMANDDECODE

TX DATA

C&DH

RX

DA

TA

SYNTHESIZERLOCK DETECT

ADC

ADC

HP

A

Electronics Unit

C&

DH

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L, C and S-band Synthesizers

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Transponder Digital Block Diagram

TrackingRX

Conditioning

Data ClockGeneration

SpecialCommandDecode

C&DHCommand /

StatusInterface

LPF,2kHz-1MHz

LPF,2kHz-1MHz

I fromTuner IC

Q fromTuner IC

I in

Q in

RX DataData out

9.625MHzVCO

To Synth.

MasterClock

Lock Indication& other status

OscillatorControl

I in

Q in Q out

I out

RX Clock

TX Clock

RX Data

Commands/ Status

Commands/ Status

Parameter change / status read

ADCClocking

SpecialCommands

TXConditioningData Out Data In

Synthesizer setup &other commands

Radiostatus

RadioCommand

C&DHinterface

Discreteinterface

Hard & SoftC&DH ResetC&DH Cmd& Status

CommandsOut RX Clock

RX Data

RX Clock

TX Clock

TX Data6-8 bitDAC or

ResistorLadder

To Modulator IC

To AGC AGC +/-

Loopback

(2 rates, andset-to-nominal)

8 bitADC

8 bitADC

XpdrResetSoft Reset

Bit Lock Bit Lock

CarrierDetectSignal Detect

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Communications System Development

• Transponder System Development– Transponder being designed under phase 2/3 SBIR

• Will result in breadboard/test unit and Qual unit

– Firm fixed price (FFP) contract expected for flight units

– After Transponder CDR, Aug 2001, contract for flight units will be issued

– No Heritage; New technology, 5 volt, digital, single reference oscillator

– New development. Requires full qualification

• Antenna Development– In progress at GSFC Code 567

• Feed blanks under contract with Emerson & Cuming

• Polyflon to lay traces on blank feeds

• Have prototype Choke Ring Assembly; needs final design and fab

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Communications System Technology

• Technology Characteristics

– Receiver and transmitter will use common frequency synthesis (common to any transponder)

– Under development by AeroAstro

– Technical Readiness Level is currently about 3/4

• Untested conventional design, Hardware prototyping

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Testing and RFGSE• Test Program is under Development per ST5-495-007,

Component Test Requirements and Guide Lines

– Will include compatibility and performance characterization

• RFGSE

– One RF Rack to include

• PSK Modulator/Xmtr (µdyne TSS-2000)• S-band Receiver (µdyne MRB-1200 or 700)• Upconverter (Miteq UP-25020)• Downconverter (Miteq DN-25020)• Spectrum Analyzer (HP 8596E)• Oscilloscope (HP54602B)• Plotter/Printer/PC• Power Meter (HP4418A)• Power Meter Heads (HP8481A, H)• Bit Error Rate Test Set (FBD-6000A or BitAlyzer 26, 400, 622)

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Risk Mitigation (1 of 2)• Risk

– Oscillator; 40 weeks ARO for flight units

– HPA 1.5 W DC to RF efficiency not confirmed

– Diplexer transmit filter may have high insertion loss

• DSNBand stop filter may be required that adds to insertion loss

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Risk and Mitigation (2 of 2)• Mitigation

– GSFC is working with AeroAstro to specify and buy the transponder oscillator. GSFC will provide for screening and qualification of the oscillator for flight with the chosen vendor and deliver it to AeroAstro for integration and qualification of the transponder. To mitigate scheduling risk, AeroAstro is building a non flight oscillator for the EM unit. The Qualification Transponder Unit will be fully tested and flight qualified, enabling it to be utilized for flight.

– A backup/replacement amplifier has been built by AeroAstro. Its 1.5 W output does not meet the 2.0 W HPA output requirement, but it can be utilized by ST-5, lowering the risk from mission critical to a performance (data rate) issue.

– Use of a low insertion loss Diplexer may require an additional band stop/ band reject filter (BRF). The filter needs to have steep cut-off characteristics at the band edges and high selectivity or Q factor and low insertion loss in-band. Even though BRF may not be needed, specifications are being drawn up and filter will be ordered.

Back-up Slides

Communications Subsystem

ST5 PDR June 19-20, 2001

GSFC 5Space Technology

“Tomorrow’s Technology Today”

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ST5 PDR June 19-20, 2001

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ST5 Mission Overview• S/C - Mission Configuration

– Satellite constellation technology mission (3 satellites)

– GTO orbit, Spin stabilized

– < 25 Kg, < 25 watts

– X-band space to ground; S-band space to space

– Magnetometer

• Space - Ground Communication

– AeroAstro transponder is 1 of 8 technologies to be demonstrated

– Orbit determination via 2 way coherent Doppler

– S/C Position Accuracy for pointing 11 m antenna: 10 Km

– 1 Kbps to 100 Kbps downlink rate, CCSDS format

– 1 Kbps to 8 Kbps uplink rate, BPSK on X-band carrier

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Transponder Tracking Block Diagram

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SINDA/G Thermal Analysis

6145Oscillator

7257Up/Down converter

8469Synthesizer

6045Baseband

Max Board Temp(°C)

Max board Temp (°C)

Radio Board

S/C 40 °CS/C 25 °C

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CCNT Link Budget: S-band Space - Space

1 Transmitter Power (W) 1.0 0.00 dB2 Antenna gain (dB) 0.003 SC Antenna beamwidth (deg) omni FWHM4 Passive Loss (dB) 1 cables, etc.5 EIRP (dBW) -1.0 29.0 dBm6 Freq. (MHz) 22657 Range (km) 10008 Space loss (dB) 159.559 Atmos, Scint, Rain Att (dB) 0.010 Polarization loss (dB) 0.211 Rcvd power den (dBW/m2) -132.7012 Rcvd PSD over 4 KHz -102.11 convo coded

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CCNT Link Budget: S-band Space - Space

14 Antenna gain (-surf loss)(dB) 0.0 55% eff15 Antenna beamwidth (deg) omni FWHM16 Power Received (dBm) -131.25 Bkg Temp 40K17 Antenna to LNA Loss 1.10 diplexer Temp 75.0918 LNA gain (dB) 20 N=3.5dB T=359.23K19 System temp (deg K) 399.23 26.01 dB K20 System G/T (dB/K) -27.11 L14 - L1921 C/No (dB-Hz) 40.23 L12 + L 20 + 228.622 Data rate (bps) 1000 30 dB (N = -172.59dBw)

23 Implementation loss (dB) 2.4 incl mod & diff coding24 Avail Eb/No (dB) 7.83 L21 - L23 - L2425 Eb/No required (dB) 4.4 10E-5 coded (4.2 ideal

soft)

26 Avail margin (dB) 3.43 L25 - L26

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Transponder PDR Review Actions

• SCR Held May 10-11, 2000

–8 actions assigned, all closed with originator

• Transponder PDR October 19, 2000, PDR January 31, 200156 RFAs written, 39 closed, 17 Open until Transponder CDR

–2 Compliance matrix AA Close, fill by CDR–3 Incomplete items AA Open, close by CDR–10 Present signal characteristic to electrical systems ST5 Done, close by CDR–11 Mechanical, thermal, electrical interfaces AA Done, close by CDR–13 Define resets ST5/AA Done, close by CDR–16 Work with electrical systems on C&DH interface AA/ST5 Done, close by CDR–17 Provide parts list AA Done, close by CDR–29 Parts qualification and testing AA Open, close by CDR–31 Plan for reduced magnetic signature AA Open, close by CDR–35 Specify transponder-C&DH command and telemetry AA Done, close by CDR–36 above plus special commands ST5/AA Done, close by CDR–46 Phase noise vs tracking accuracy ST5/AA Open, close by CDR–47 Specify limit on spurs to meet system requirements AA Open, close by CDR–49 Show that Cmd format is supported by ground stationsST5 Open, close by CDR–50 Define testing for development and compatibility AA/ST5 Open, close by CDR–53 Develop plans for false and self lock testing AA Open, close by CDR–54 Generate plans for packaging AA Open, close by CDR