A multioctave active MMIC quadrature phase shifter

A 0.1-4.5-GHz GaAs monolithic quadrature phase shifter with very small phase error, based on a phase-locked loop system, was designed, fabricated, and tested. The phase shifter consists of two RC all-pass networks with FETs used as voltage-controlled resistors. It delivers four quadrature output signals as required for the operation of the double balanced mixers used in the receiver. The main feature of this system is that it has an overall phase error of less than 2 degrees . When integrated in a broadband receiver the system produced an image rejection of at least 30 dB over the 0.1-4.5-GHz frequency band.<>