The UAVSAR Transmit / Receive Module

This paper describes the L-band transmit/receive (T/R) modules of the UAVSAR phased array antenna. UAVSAR (uninhabited aerial vehicle synthetic aperture radar) is an airborne, repeat-pass, polarimetric radar interferometer instrument that is being developed at JPL and NASA Dryden. The instrument has demanding requirements for phase stability over temperature and the antenna components, particularly the T/R modules, are key to meeting these requirements. The UAVSAR T/R modules have a bandwidth of more than 80 MHz centered at 1257.5 MHz and support dual receivers for full quad polarization measurements. Phase and amplitude are controlled by a 7- bit phase shifter and a 5-bit attenuator, respectively. Custom microwave integrated circuits were developed and fabricated for the low noise amplifier (LNA) and phase shifter circuits. The receiver noise figure is 2.25 dB at OC including all front-end losses. The transmitter power amplifiers use silicon bipolar junction transistors that typically generate 162 W peak into a nominal 50 ohm load. The modules have an overall efficiency of 32% at the peak operating duty cycle of 5%. Module mass and dimensions are 567 g and 16 cm times 12 cm times 3 cm, respectively. Fifty four of these T/R modules were fabricated for integration into two antennas. System architecture and performance data for this ensemble of modules are discussed.