Monolithic Phase and Gain Control Circuit for Broadband Frequency Tuning of Multipole Microwave Active Filters

In this article, a lossless variable gain and analog transmission-type phase shifter which consists of a MESFET with series resonant impedances including varactor diodes is designed. Layout, simulated and measured results of the MMIC chip are presented. The final function of this original monolithic circuit is to be introduced in multipole ring resonator planar filters to tune the frequency response and to compensate for the intrinsic losses of the resonators. The frequency tunability of these new selective active filters is better than one octave bandwidth.