12-W $X$ -Band MMIC HPA and Driver Amplifiers in InGaP-GaAs HBT Technology for Space SAR T/R Modules

The chip-set for the transmitting power lineup of satellite SAR antenna T/R modules has been designed and implemented exploiting a 2- μm GaInP-GaAs heterojunction bipolar transistor (HBT) technology suitable for space applications. The HBT technology features an integrated emitter ballast resistor that enables high-power density operation without suffering thermal runaway phenomena. Two monolithic microwave integrated circuit (MMIC) driver amplifiers and a MMIC HPA are described: the drivers exhibit small-signal gains exceeding 21 dB and P1 dB output power of about 28 and 29 dBm, respectively, in a 2-GHz bandwidth and CW condition. The HPA delivers more than 40-dBm power at about 2.5-dB gain compression and power-added efficiency (PAE) exceeding 36% in a 700-MHz bandwidth in pulsed operation. Its peak performance at the center of the band are 40.9-dBm output power and 45% PAE. These performance are obtained within tight de-rating conditions for space applications.

I. Introduction

This paper describes the design and performance of two monolithic driver amplifiers and an HPA, operating at -band to be used in the transmitting power lineup of transmit–receive (T/R) modules, employed in satellite synthetic aperture radar (SAR) antennas for earth observation. This activity was promoted by the Italian Space Agency with the object of assessing the achievable performance of new monolithic microwave integrated circuits (MMIC) and technologies for the second generation of Cosmo SkyMed [1], a European constellation of four satellites equipped with SAR antennas [2], whose T/R modules will be produced by Thales Alenia Space Italia. The four satellites of first generation of Cosmo SkyMed are currently in orbit sending to ground bases a huge amount of information useful for scientific research, Earth monitoring and security in Europe [3]. Indeed the capability of -band SAR to gather ground images continuously, regardless of lightness and weather conditions, is extremely useful in several fields, such as agriculture, floods and earthquake control, natural hazard and sea-level monitoring, boarder control, and military applications. The next-generation SAR antenna addresses increasing performance in terms of duration, coverage, and resolution of the service. As far as regarding the transmitting chain of the T/R module, the demand for improved system performance implies the optimization of key parameters: bandwidth, gain, power-added efficiency (PAE), and output power. To assess the achievable performances, different technologies already suitable for space application (GaAs pHEMT and InGaP-GaAs HBT) and different European suppliers were explored. In the following, the performance achieved by a space-evaluated HBT technology is reported.