Reflection-Type Phase Shifter Integrated With Tunable Power Attenuation Mechanism for Sub-6 GHz Wireless Applications

Abstract

An integrated configuration of the reflection-type phase shifter (RTPS) and attenuator with simultaneous phase and amplitude control is presented for a phased-array front-end beamforming. The phase shift function of the RTPS adopts a quadrature coupler with high/low pass lumped elements and the corresponding π-type C-L-C loads. An RF tuner is subsequently incorporated into the 90° coupler to provide an energy reduction path and applied at the intermediate inductor of the coupler, thereby enabling a tunable transmission power. The merged coupler/RF-tuner realizes a matched and symmetrical structure with less impact on the load impedance variation, which can be regarded as part of the RTPS that performs RF signal degradation and maintains phase shift tuning. Furthermore, the π-type attenuator is incorporated into the RTPS to obtain an adequate power control range for the side-lobe suppression of the beamforming network. The simulated and measured results demonstrate the feasibility and suitability of the network for the proposed merged configuration applied to the phased-array system.