CMOS integrated circuits for X-band phased array systems

Abstract

A power amplifier, a phase shifter, a digital attenuator, and a transmit/receive (T/R) switch are fabricated for X-band phased array applications, which are implemented with CMOS 0.18 um technology. The power amplifier has 2-stage differential and cascode structures. It provides 1-dB gain-compressed output power (P 1dB ) of 20 dBm and power-added-efficiency (PAE) of 19 % at 8–11 GHz frequencies. The 6-bit phase shifter utilizes embedded switched filter structure which consists of n-MOS transistors as a switch. It has 360° phase-control range with 5.6° phase resolution. It shows RMS phase and amplitude errors are below 5° and 0.8 dB, and insertion loss of −15.7 ± 1.1 dB. The 6-bit digital attenuator is comprised of embedded switched Pi-and T-type attenuators resistive networks and nMOS switches and employs compensation circuits for low insertion phase variation. It has maximum attenuation of 31.5 dB and 0.5 dB amplitude resolution. Its RMS amplitude and phase errors are below 0.4 dB and 2° at 8–11 GHz frequencies, and insertion loss is −10.5 ± 0.8 dB. The SPDT T/R switch has series and shunt transistor pairs on transmit and receive path, and only one inductance to reduce chip area. It shows insertion loss of −1.5 dB, return loss below −15 dB, and isolation about −30 dB.