Dual-Band Rat-Race Coupler With Arbitrary Power Divisions Using Microwave C-Sections

Abstract

Rat-race coupler is designed to have dual-band operation, a miniaturized area, and arbitrary power division using microwave C-sections. With a C-section and two transmission line sections attached to both of its ends, an elementary two-port is designed to play the role of a quarter-wave section in a conventional rat-race. It is designed to possess phase changes of 90 degrees and 270 degrees at the first and second frequencies, respectively. Transcendental equations are derived for calculating its structure parameters. Two circuits operating at 2.45/5.8 GHz with various output power ratios are fabricated and measured. Both couplers have only 31% area of conventional rat-race at the first band. It is believed that these circuits have the best size reduction for microstrip dual-band rat-race with arbitrary power division in open literature. Measured results agree well with their simulation counterparts.