A Compact Single-Layer Ultra-Wideband Phase Shifter Using Weakly Coupled Lines

This paper presents a novel compact single-layer ultra-wideband phase shifter using weakly coupled lines, which contains a main line and a reference line. The basic equations of this phase shifter are calculated based on the even-odd mode theory. Then, the parameters are determined in the design procedure. A compact ultra-wideband 90° phase shifter is designed, fabricated, and measured for demonstration. The measured results, in good agreement with the EM simulation, show that this phase shifter can provide a wide bandwidth from 1.36 to 4.53 GHz (107.6%) with a phase deviation of only ±5°. Meanwhile, return loss better than 10 dB and insertion loss less than 1.25 dB can be obtained.