Integrated T/R modules employ GaAs ICs

Design and performance features of GaAs chip-based phased array radars which can function in both transmit and receive (T/R) modes are surveyed. Incorporating both T/R on the same array requires phase coded signals which are then shifted, amplified and shaped into a beam and also switching for the return signal. GaAs FETs are restricted to thicknesses under 100 microns to avoid high microstrip losses. The devices can each produce a 2 W output but also generate 4.5 W heat each. Heat sink substrates, flip chipping, airbridging and vias in the chips are all methods of reducing the heat loads. No outputs greater than 2 W from production chips are expected before 1986. MESFET configurations being explored as single pole double throw switches between the T/R modes are described, along with numerical expressions for the I-V states of the array during switching. Finally, suggestions for the phase shifter and matched circuit (to maintain sensitivity) are provided.