AMTA2012 110 Innovative Approach for Satellite Antenna Integration and TestVerification LS8 MB1 GG7 GV GC vL25July 4

7/29/2019 AMTA2012 110 Innovative Approach for Satellite Antenna Integration and TestVerification LS8 MB1 GG7 GV GC vL2

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INNOVATIVE APPROACH FOR SATELLITE ANTENNA INTEGRATION AND

TEST/VERIFICATION

L.J. Foged, L. Scialacqua, F. Saccardi

SATIMO, Pomezia, Italy

M. Bandinelli, M. Bercigli, G. Guida

IDS, Pisa, Italy

G. Giordanengo, F. Vipiana

Antenna and EMC Lab, ISMB, Torino, Italy

M. Sabbadini

ESA/ESTEC,

P.O. Box 299, AG 2200 Noordwijk ZH, The Netherlands

G. Vecchi

Antenna and EMC Lab, Politecnico di Torino, Torino, Italy

ABSTRACTThe increasing complexity and stringent performances

in RF instruments and payloads often demands that

the final RF functional verification is performed on

the integrated satellite. In order to minimize the

overall time and cost of future Antenna Integration

Verification and Test campaigns (AIV/AIT) it is

necessary to investigate and develop advanced test

methodologies to minimize the test duration.

This paper reports the preliminary results of a

functional testing solutions for RF end-to-end antenna

testing. The proposed approach is based on the

intelligent and innovative use of existing measurementcapabilities and advanced numerical modeling tools.

The scope of the activity is to demonstrate through the

implementation of a demonstrator and measurement

on suitable hardware the possibility to achieve

accurate and fast measurement results using a radical

measurement under-sampling with respect to the

conventional Nyquist criteria.

Keywords: Electromagnetic Testing, Near- Field,

Measurements, Sampling, Verification.

1. Introduction

Modern telecommunication payloads are excellentexamples of the increased satellite testing complexity and

have been subject to the development of dedicated testing

techniques and hardware in the past [1-14]. Today,

complex telecommunication payloads feature tens or

hundreds of beams, each operating with frequency reuse

and variable connectivity, which need to be characterized

accurately to ensure proper in-orbit system performance.

In related the area of space science, future missions

foresee the use of antennas with hundreds of beams

operating over an extremely large frequency band, high

beam efficiency and very low noise figures. Finally, Earth

observation instruments, like imaging radiometers,

synthetic aperture radars and synthetic aperture

radiometers have reached a level of complexity that makes

strategies for test time reduction very appealing if not

already necessary.

Considering future planned satellite missions, the sizes of

the antennas can reach up to 12 meters in diameter at L-S

band and the very large satellites of the next generations

becomes prohibitive for the existing quiet zones ofconventional Compact Antenna Test Ranges (CATR) or

would require major investments into new larger facilities

[6-10]. Very large, dedicated near field systems based on

planar, cylindrical or spherical scanning geometries are

expected to be a viable intermediate solution to achieve a

better compromise between accommodation of the device

under test and the cost of the measurement facility [11-

14]. However, due to the sampling criteria the

measurement time associated with these tests becomes a

serious obstacle.

A new and promising testing strategy for time demanding

satellite tests scenarios has been presented recently in

[14]. The preliminary results, based on theoretical data,

demonstrated the possibility to perform accurate and fast

antenna measurement with a radical under-sampling of the

Near Field (NF) with respect to the conventional Nyquist

criteria. This paper reports on the further developments of

the techniques and present preliminary results from the

testing of a representative multi beam satellite mission in

Ku-band.


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2. Proposed solution

The proposed approach is discussed in some detail in

[14]. The proposed solution is based on a robotic arm

sniffer system, sampling the radiated near field of the

Antenna Under Test (AUT) mounted on the spacecraft.

The use of the robot and non-canonical NF scanning allow

for the antenna not be positioned optimally for traditional

testing. Since the robotic arm NF sampling is slower thana traditional canonical scanning a radical under sampling

is needed to make the proposed approach appealing.

The radical under sampling is obtained by an interpolation

of the measured NF values by a special algorithm taking

advantage of the physical information provided by

numerical modeling of the antenna. The modeling is

performed prior to the measurement. Included in the

modeling are several physical permutations of the realistic

antenna model of the AUT. This is to generate a self-

consistent representative basis for the expansion of the

AUT. If the basis is constructed correctly [14], the

measured antenna can be fully represented by a linear

combination of the permutated numerical modeling. The

actual AUT measurement, then consist in determining the

correct coefficients of the linear combination of the

expansion basis. The coefficients of the expansion basis is

much less than the actual antenna sampling criteria

leading to a drastic reduction in the number of

measurement samples.

2.1 Advanced robotic arm sniffer system

The use of the robotic arm sniffer system approach give

access to different scanning and sampling strategies

including canonical scanning. The system is based on a

Kuka high precision robot [5] and a SATIMO Dualpolarized Open-Ended Waveguide DOEW6000 probe

with interchangeable apertures covering the frequency

band [6-20] GHz as shown in Figure 1. This probe is

designed with a radiation pattern nearly identical to

traditional circular open ended waveguides on a much

wider bandwidth.

Figure 1 - Kuka robot (left) and SATIMO DOEW6000

probe covering the 6-20GHz band (right).

Different examples of scanning surfaces that can be

performed with the sniffer system are shown in Figure 2

and Figure 3. The assembly of the DOEW6000 precision

probe on the robotic arm, is shown in Figure 4.

Figure 2 - Example of planar scanning performed with

the proposed sniffer system.

Figure 3Different sampling strategies: planar,

cylindrical and spherical scan surfaces.

Figure 4Example of assembly for the advanced

measurement sniffer system.


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2.2 Antenna Under Test (AUT)

The AUT for validation and demonstration of the

proposed test technique is a Multibeam antenna system in

the frequency range [14-16] GHz.

The Multibeam antenna is composed by the SATIMO

SR40-A reflector and a feed array of 7 linearly polarized

Ku band horns. The feed array configuration is shown in

Figure 5. Dimensions of the SATIMO high precision

offset parabolic reflector antenna SR40-A are 20

@15GHz. The Multibeam antenna is shown in Figure 6.

The Multibeam antenna is equipped with a high precision

mechanical flange. The alignment is determined by a

precision pin in mechanical interface plate.

The horns can be fed and mounted independently on its

basement, which is connected to the arm of the reflector.

Changing the basement allows to get different array

configurations.

Figure 5Feed array configuration of the AUT.

Figure 6Multibeam antenna.

2.3 Modelling and simulations of the AUT

The AUT, consisting in the Multibeam antenna has been

simulated using ADF-EMS tool [17]. The complete

simulation, electrical current distribution, of the model of

the antenna is shown in Figure 7. Copolar coverage

patterns of all beams are shown in Figure 8.

Figure 7Simulated electrical current distribution on

the Multibeam antenna, beam #5 is fed.

Figure 8Simulated beam coverage patterns

@15GHz.

To obtain the induced electrical currents a full-wave

approach (Method of Moment) was used. The MoM

solution was accelerated by means of Multi-level Fast

Multi-pole Algorithm. The Multibeam antenna was

discretized into a total of 409,090 triangles and 21 wires,

i.e. 613,531 unknowns (613,510 RWG, 14 PWL and 7

attachments). With the purpose of generating a high-

fidelity model, all the initial CAD external surface was

taken into account (i.e. discretized).


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2.4 Reference measurement of the AUT

Preliminary analysis of the test technique has been done

starting from a reference measurement of the antenna,

before using the measured samples by the advanced

robotic arm sniffer system. This reference measurement

has been done in the SATIMO SG-64 Spherical near field

test facility in Paris (SNF), see Figure 9. The measured

results have been preliminary compared with the resultssimulated by ADF-EMS tool. Comparison between

simulation and measurement for the beam #2, see Figure

10, shows that the agreement is good.

Figure 9Multibeam antenna in the SATIMO SG-64

spherical near field test facility in Paris.

Figure 10 Comparison between simulation and

measurements (PNF and SNF) of the AUT. Solid lines

show co-polar components, dashed lines show cx-polar

components.

2.5 Specialized interpolation algorithm

As discussed previously, the interpolation algorithm uses

a reduced expansion base for the near field to far field

transformation formed from permutations of the numerical

modeling of the antenna prior to the measurement.

There are two relevant constituent of the pre and post

processing tools in the proposed approach. The first is the

Equivalent Current (EC) expansion that allows forward

and backward mapping between NF and FF on arbitrary

(non canonical) surfaces. A robust and accurate

formulation has been implemented that has already been

tested by the team with real data and employed in tasks of

industrial relevance [2-4]. The second is the Synthetic

Function eXpansion (SFX) as presented in [15]. This

technique was developed for efficient MoM simulations,

but its theoretical foundations provide an important

framework for the integration of simulation and measured

data in the present application.

3. Preliminary results of test technique emulation

using measured data on the AUT

Preliminary evaluation of the achievable performance in

terms of accuracy and down sampling ration with respect

to conventional measurement techniques has been

performed starting from the samples of the reference

measurement in the SG-64 Spherical Near Field (SNF)

test facility. The simulations of the AUT has been

performed by ADF-EMS tool.

The reference measurement has been done on a spherical

surface constant angular grid set of points and it

represents the target measured field. Emulating a

measurement scenario by the sniffer system, various

subsets of the measured NF points can be selected by the

interpolation algorithm for reconstructing the target

measured field using a reduced set of measurement points.

This approach is not fully representative of the real

sniffer system since all NF points must lie on the

measurement sphere and on the regular angular grid used

by the SG-64, SNF measurement system. However, the

constructed test scenario is nevertheless indicative of what

can be achieved in the final system implementation.

The reference measurement in the SG-64, SNF system

was performed using close to 58.000 measurement points.

This is very close to the minimum criteria for such AUT

measurement considering a minimum sphere of diameter0.5m or 25 at 15GHz. The Nyquist minimum sampling

criteria obtained by dividing the minimum sphere surface

in areas of (/2)2 is 31.416 dual polarized field samples.

The far-field reference field and the reconstructed field

based on only 909 dual polarized field samples are

compared in Figure 11. This number of samples

represents a down sampling factor of 34 with respect to


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the Nyquist sampling criteria and a factor of 63 with

respect to a standard SNF measurement using a regular

angular grid over the spherical measurement surface [16].

The difference in AUT peak directivity between the

reconstructed field and the reference field obtained using

our proposed methodology is shown as a function of the

under-sampling factor in Figure 12 (blue curve). The

Nyquist criteria is used as the reference samplingminimum level. The 0.27dB directivity difference

obtained with under-sampling factor ~34, corresponding

to the plots in Figure 11 is highlighted on the plot.

When the number of the measured samples is increased

the blue curve tends to the red one in Figure 12, which

represents the peak directivity difference between the

measurement and the best single numerical simulation.

The red curve shows the best results that can be expected

starting from the actual measurements and simulations

used for preliminary testing the methodology.

Figure 11 Far Field Reconstruction (Beam #2) with

respect to the measured Field (top =90, bottom

=90).

Figure 12Peak directivity difference (Beam #2) with

respect to the measured samples (the sampling factor

is the ratio between the samples of Nyquist and the

selected samples).

4. Conclusion

The scope of the on-going activity is to demonstrate

through the implementation of a demonstrator and

measurement on suitable hardware the possibility to

achieve accurate and fast measurement results using aradical measurement under-sampling with respect to the

conventional Nyquist criteria.

The proposed solution is based on an intelligent and

innovative use of existing measurement capabilities and

advanced numerical modeling tools. The AUT is a multi-

beam antenna system, widely used in space applications

for mobile and broadband communications.

Preliminary results, emulating a sniffer type measurement

scenario, show that under-sampling factors of ~34 with

respect to the conventional Nyquist criteria and a factor of

~63 with respect to a standard regular angular grid SNF

measurement can be achieved with this approach. Thepreliminary testing scenario has shown that it is possible

to reconstruct efficiently the general shape and level of the

main lobe of the radiation pattern despite the radical under

sampling. Theses preliminary results indicate the

feasibility of this technique in RF test scenarios to

minimize the cost and duration of test campaigns.

While reference measurements (see above) can be used

for preliminary investigations on the testing technique, the

use of the advanced robotic arm sniffer system will lead

to a further optimization of the methodology due to the

increased degree of freedom of the system.

Mechanical aspects of the system, such as the stability andpossible vibrations of the robotic arm during movement

need to be carefully controlled during the measurements

in order to increase the accuracy of the results. Realization

of a measurement scenario fully based on the sniffer

system approach and demonstration of the testing

technique are the next steps of this activity.


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5. References

[1] ANSI/IEEE Std 149-1979 IEEE Standard Test

Procedures for Antennas.

[2] J .L.A. Araque and G. Vecchi. Improved-accuracy

source reconstruction on arbitrary 3-D surfaces. Antennas

and Wireless Propagation Letters, IEEE, 8:10461049,

2009.

[3] J .L.A. Araque and G. Vecchi. Field and source

equivalence in source reconstruction on 3-D surfaces.

Progress in Electromagnetic Research (PIER), 2010.

[4] L. Foged, L. J.; Sabbadini, M.; Araque Quijano, J.L.;

Vecchi, G.; Mioc, F. Advanced Antenna Diagnostics

based on Equivalent Currents, Proc. EUCAP 2010 .

[5] Kuka website: www.kuka-robotics.com

[6] J. Hartmann, J. Habersack, H.-J. Steiner, Accurate

and Efficient Satellite Payload Testing in Compact

Ranges, 28th ESA Antenna Workshop on Space Antenna

Systems and Technologies, 31. May - 3. June 2005,

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[7] J. Hartmann, J. Habersack, H.-J. Steiner,

Improvement of Efficiency for Antenna and Payload

Testing, 30th ESA Antenna Workshop on Antennas for

Earth Observation, Science, Telecommunication and

Navigation, May 2008, ESA/ESTEC Noordwijk, The

Netherlands.

[8] J. M.Lopez, L. Duchesne, L. Durand, Ph. Garreau, P.

Meisse, H. Garcia, C. Bouvin, C. Fat, F. Viguier, Fast

Test Technique to reduce RF measurement time of

satellite antenna payload at system level, Aerospace

Testing 2007, Munich, Germany, 29 March 2007.

[9] L. Duchesne, J.M. Lopez, L. Durand, Ph. Garreau, C.

Fat, F. Viguier, H. Garcia, C. Bouvin, P. Meisse, Study

of innovative fast techniques to reduce the measurement

time of the patterns of multi beam antennas, 29th ESA

Antenna Workshop on Multiple Beams and

Reconfigurable Antennas, April 18-20, 2007, ESTEC,

Noordwijk, The Netherlands.

[10] M. Boumans, L. Duchesne, Electronically scanned

arrays as probe and feed system in compact ranges, The

third European conference on Antennas and propagation,

EuCap2009, Berlin, March 23 - 27 2009.

[11] U. Shemer, A. Gandois, A High Performance Stateof the Art Planar Hybrid Scanner, 32nd Annual AMTA

Symposium, October 10-15, 2010 in Atlanta, Georgia,

USA.

[12] L. Durand, L. Duchesne, F. Chauvet, L. J. Foged

Fast and Accurate Testing of Electrically Large Antennas

using Probe Arrays, ISAP, International Symposium on

Antennas & Propagation, Oct 2011, Jeju, Korea.

[13] L. Durand, L. Duchesne, T. Blin, Ph. Garreau, R.

Braun, R. Konevky, L. Shmidov, G. Forma, P. Meisse, E.

Decoux, M. Paquay Innovative Technique for fast

Testing of Multibeam Space Antennas, 33rd Annual

Symposium of the Antenna Measurement Techniques

Association, AMTA, October 2011, Englewood,Colorado, USA.

[14] L.J. Foged, L. Scialacqua, M. Bandinelli, M.

Bercigli, F. Vipiana, G. Giordanengo, M. Sabbadini, G.

Vecchi, Numerical Model-Augmented RF Test

Techniques, 6th European Conference on Antennas and

Propagation, EuCAP 2012, Prague, 2630 March 2012.

[15] L. Matekovits, V. A. Laza, G. Vecchi, Analysis of

Large Complex Structures With the Synthetic-Functions

Approach, IEEE transactions on antenna and propagation

VOL. 55, NO. 9, September 2007.

[16] J. E. Hansen (ed.), Spherical Near-Field Antenna

Measurements, Peter Peregrinus Ltd., on behalf of IEE,

London, United Kingdom, 1988

[17] ADF website:

http://www.idscompany.it/page.php?f=92&id_div=7
http://www.idscompany.it/page.php?f=92&id_div=7http://www.idscompany.it/page.php?f=92&id_div=7

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AMTA2012 110 Innovative Approach for Satellite Antenna Integration and TestVerification LS8 MB1 GG7 GV GC vL25July 4