Ku band digital CMOS phase shifter

Abstract

Phase shifters are essential components in a phased array system for scanning of the radiated beam in minimal time. Recently, active phased array radar (APAR) systems utilizing monolithic microwave integrated circuit (MMIC)-based transmit/receive (T/R) modules are receiving increased attention for telecommunications and radar applications. The most expensive component in developing such an active phased array system is a number of digital phase shifters. Most of MMIC phase shifters have been developed with GaAs pHEMT technology for military applications. However, their price is much higher, costing beyond any reasonable budget for commercial application. Other technologies based on MESFET and HBT have also emerged during last decade and are now available for the low cost. Recent sub-quarter micron CMOS technology offers excellent microwave performances which are comparable to those of GaAs technology. In addition, RF CMOS product can be cost effective if the volumes are sufficiently high. Therefore, in order to significantly reduce the cost, it is obvious to develop CMOS digital phase shifter, thereby developing such low cost, low profile, and electronically steerable phased array antennas. A Ku band 5-bit MMIC phase shifter using parallel resonator in 0.18-um CMOS technology is described. A body-to-source short technique of MOSFET switches improves the insertion loss of a switch by removing the ground path through a body port. Although the isolation of the switch is not good, the large off capacitance can be used as an element of the phase shifter. The $1^{st}$ - metal ground of the microstrip line completely eliminates the field penetration through the silicon substrate, thereby enabling low loss propagation. The proposed $90^\icrc$ phase shifter has broadband phase characteristics. All circuit parameters have been derived to obtain a minimum variation of phase difference around the operating frequency. The fabricated 5-bit phase shifter demonstrates an ov...