A precision T/R module for X-Band SAR applications with a transmit chain in HBT-Technology

Klaassen, Andreas ; Reber, Rolf ; Ludwig, Michael (1999) A precision T/R module for X-Band SAR applications with a transmit chain in HBT-Technology. In: Gallium Arsenide Applications Symposium. GAAS 1999, 4-5 October 1999, Bologna, Italy.
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T/R modules suitable for spaceborne SAR instruments have to fulfil very strong requirements given by the challenging environmental and electrical conditions in space. This paper shows that the HBT (Heterojunction-Bipolar-Transistor) technology is able to meet these requirements for future SAR systems. For this application a separate breadboard Tx-chain as well as a T/R module have been realised which operate in X-Band and use the HBT technology for the high power chain. For the breadboard Tx-chain with driver and HPA in balanced configuration an output power of 39.5 dBm with an efficiency of 32.5% at 10% duty cycle was achieved. For the medium power T/R module with HBT driver and HPA in single ended configuration the output power is stabilised by a power control loop to 35 dBm with an overall module efficiency of better than 11.5% at 10% duty cycle. Full amplitude and phase stability of the T/R module is realised by a phase stable variable gain amplifier (VGA) and a 7-bit phase shifter. An accuracy of ± 0.5 dB in Rx gain and ± 6° in Rx/Tx phase under all operating conditions has been achieved by a novel and highly flexible calibration method. The paper will discuss the T/R module architecure with emphasis on the Tx-chain with HBT-amplifiers (fabricated at UMS) and the realised concept for the power control loop. Furthermore the T/R module performance will be presented with respect to SAR system requirements.

Document type
Conference or Workshop Item (Paper)
Klaassen, Andreas
Reber, Rolf
Ludwig, Michael
Deposit date
15 Feb 2006
Last modified
17 Feb 2016 14:29

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