cnes workshop mw_filters_2015_angeletti_lisi_v01

ESA UNCLASSIFIED - For Official Use

Integration of Microwave Filters in Active Array Antennas for Space Applications

Dr. Piero Angeletti, Dr. ing. Marco Lisi International Workshop on Microwave Filters CNES, Toulouse, 23-25/03/2015

P. Angeletti – M. Lisi | 24/03/2015 | Slide 2


Summary

• Active array antennas for space applications require a wide range of state-of-the-art technologies and a large number of passive and active electronic equipment;

• Filters play an essential role both in terms of their impact on the overall payload performance and in the perspective of mass and cost reduction;

• A system engineering approach to the design and development of active arrays (specifically to the definition of filtering requirements) is mandatory in order to achieve a synergic and effective integration of all functions.



Direct Radiating Array (DRA) Active Antenna Configuration



Array Fed Reflector (AFR) Active Antenna Configuration



Input (Rx) Filter Fundamental Functions 1.To suppress the leakage from the

transmit section of the same payload as well as all other out-of-band signals (carriers and intermodulations) generated on-board;

2.To reduce the overall out-of-band noise received by the antenna and otherwise reaching the LNA input.



Artemis S-Band DRA Input Filter

Measured response of an S-band DRA input filter (Artemis Multiple Access Data Relay Payload Study), showing a higher than 70 dB rejection at Tx frequencies (L and S bands).



Output (Tx) Filter Fundamental Functions 1.Reduce the noise transmitted at the Rx

frequency of the same payload; 2.Reduce noise and intermodulation

products at the receive frequencies of other payloads on-board the satellite;

3.Reduce noise and intermodulation products transmitted to ground over protected frequency bands (e.g. radio astronomy bands).



Why to Optimize Filters Requirements? • In a traditional payload one or a few input filters are

needed in the receive section, while one or a few output filters or multiplexers (OMUX’s) are present in the transmit section;

• In active antennas as many input filters and output filters as the number N of feed elements are needed, where N can be as high as several tens or even several hundreds of units;

• Optimizing filters requirements means minimizing complexity, mass and cost of the payload;

• It is worth noting that, while electronic devices lend themselves to miniaturization, electromagnetic structures (such as microwave filters) are strongly constrained by the laws of physics (e.g. wavelength, current densities, conductivity, Q-factor).



Main Characteristicis of Filters Integrated in Active Antennas • Insertion loss; • Out-of-band rejection; • VSWR (a high VSWR, besides introducing reflection

losses, would also cause in-band amplitude and phase ripples);

• Phase tracking (over temperature and ageing); • Power handling; • Passive intermodulation (PIM) products; • Multipactoring (not likely in active antennas, as each

transmit filter is handling a somehow limited RF power level, as compared to a traditional payload configuration);

• Size; • Mass.



Insertion Loss Always Plays an Essential Role • Pass-band loss (insertion loss) is

important in both Rx and Tx filters; • In a receive filter, the insertion loss will

add to the Noise Figure of the low-noise amplifier degrading the overall payload G/T;

• In the transmit filter, a higher insertion loss would mean tougher power amplifier specs, higher power consumption and more heat dissipation.



Amplitude and Phase Tracking Requirements • An accurate phase (amplitude) tracking is required

between any two chains in the active antenna, at all operating temperatures and over the entire life time;

• Two kinds of errors can be identified: "systematic" errors and "random" errors;

• Systematic errors are defined as predictable and/or measurable deviations of the absolute insertion phase (or absolute amplitude) of an active chain from its nominal value at reference conditions, i.e. at reference temperature (e.g. ambient) and at beginning of life;

• Systematic errors can be easily calibrated out; • Random errors derive mainly from temperature and

aging effects, adding to systematic errors.



Systemic Definition of Filtering Requirements (1/3) Factors to be considered in a Rx active antenna design: • The out-of-band performance of the radiating

elements (both conducted, e.g. return loss, and radiated, i.e. pattern);

• The optimal apportionment between filtering at RF and filtering at IF;



Systemic Definition of Filtering Requirements (2/3)

• Apportionment of the required overall filter response, in an analogue beam-forming antenna, having filters at the M outputs of the BFN (N, number of feeds, is usually much higher than M, number of beams);

• The spatial isolation between RX and TX antennas of the same payload and between antennas of different payloads on-board the satellite.



Systemic Definition of Filtering Requirements (3/3)

Factors to be considered in a Tx active antenna design: • spatial isolation w.r.t. other antennas on-board

the spacecraft; • “filtering” effect deriving from the

intermodulation products being radiated with radiation patterns far different from that of the TX carrier. This dispersion effect derives from a linear combination of the amplitude and phase excitation coefficients, according to the order of the intermodulation.



Artemis S-Band Active Antenna (Feasibility Study)



Globalstar 1st Gen S-Band Tx Active Antenna



Ka-Band “Transmit Multibeam Antenna (TXMBA)”

Astrium Casa Espacio



Ceramic 3D Stereolithography Technology

Université de Limoges/CNRS



Substrate Integrated Waveguide (SIW) Technology



Conclusion

• Filters are among the most challenging components in the realization of active array antennas for space applications;

• More efforts are required in terms of new technologies and of a better integration with active components (LNA’s and SSPA’s);

• The final objective is making active antennas highly performing and truly affordable, with drastic improvements in terms of complexity, size, mass and cost;

• A systemic approach is mandatory to the purpose of best matching the overall architecture to physical and technological constraints.

cnes workshop mw_filters_2015_angeletti_lisi_v01

Engineering

esa unclassified

input filters

output filters

filters requirements

microwave filters cnes

piero angeletti

band noise

active antennas insertion