High-Isolation and Wide-Band 180º Hybrids Based on Electronically Tunable Lumped-Element Filters

Abstract

Abstract-A new high isolation lumped-element 180 • hybrid, using electronically adjustable filters with varactor diodes, are proposed. This design is very simple and based on only two configurable low order (N = 2) filters. Due to the limited tuning frequency range of varactor diodes, maximum near-octave frequency coverage of 2.5-5 GHz was planned in the high isolation hybrid. An impressive simulated typical isolation in the range of > 60 dB was achieved. One of the typical applications of developed hybrids could be the conversion of 70 MHz IF to microwave frequencies, with broadband mixers in single-conversion converters and very high LO rejection (> 60 dB).