360° Balanced Tunable Reflection-Type Phase Shifter With High Common-Mode Suppression

Abstract

A balanced tunable reflection-type phase shifter (RTPS) with a broad phase shift range (PSR) and high common-mode (CM) suppression is proposed. The configuration includes two identical reflection loads, comprising two varactor diodes connected in parallel at the output ports of a coupled line and a six-port balanced-to-unbalanced quadrature coupler. The coupler rejects CM signals and supplies quadrature phase to the reflection loads, whereas the electronic-controlled diodes in the reflection loads enable tunable phase shift. The RTPS is capable of precisely attaining 365° PSR and 25 dB CM rejection, and can therefore be implemented in balanced antenna systems.