Design of SPDT Switch, 6 Bit Digital Attenuator, 6 Bit Digital Phase Shifter for L-Band T/R Module using 0.7 μM 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 sidelobe 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 0.7 μm GaAs MESFET switch model to handle 30 dBm 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 -1 dB, isolation greater than 60 dB and return loss better than 20 dB has been realized on a single 3.0 mm × 2.35 mm GaAs chip. A 6-bit digital attenuator has a 31.5 dB attenuation range in 0.5 dB increments; 2.5° phase error and return loss better than 15 dB. 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 9 dB insertion loss, return loss better than 15 dB has been realized on a two GaAs chips with size 4.0 mm × 2.35 mm and 3.0 mm × 2.35 mm and 3 phase bits in each chip for the better yield