Design and Implementation of SPDT Switch, 6 Bit Digital Attenuator, 6 bit Digital Phase Shifter For L-Band T/R Module Using 0.7μm GaAs MMIC Technology

Abstract

The performance of modern radar systems with active phased array antennas is mainly driven by the performance of the microwave T/R modules. To reduce the size, weight, cost and power consumption, as well as to achieve better phase and amplitude accuracies for realizing low side lobe levels with an accurate beam steering, T/R modules, now-a-days, employ MMICs (Monolithic Microwave Integrated Circuits) for implementing Transmit/ Receive chain.The L-band SPDT Switch, 6-Bit Digital Attenuator, 6-Bit Digital Phase Shifter have been designed using GAETEC Hyderabad 0.7μm GaAs MESFET Switch model to handle 30dBm peak power. All the above components have been designed and simulated using Agilent ADS CAD tool interfaced with Academy Layout.The SPDT Switch with insertion loss less than -1dB, isolation greater than 60dB and return loss better than 20dB has been realized on a single 3.0 mm × 2.35 mm GaAs chip. A 6-Bit Digital Attenuator has a 31.5dB attenuation range in 0.5dB increments, 2.5° phase error and return loss better than 15dB. The 6 bits are cascaded to form a complete attenuator on a double 3.5 mm × 2.35 mm GaAs chip with 3 attenuator bits in each for a better yield. A 6-Bit Digital Phase Shifter with 9dB insertion loss, return loss better than 15 dB has been realized on a two GaAs chips with size 4.0mm × 2.35mm and 3.0 mm × 2.35 mm and 3 phase bits in each chip for the better yield.