Compact 140–220 GHz E/H Waveguide Phase Shifter and Its Application to Terahertz Multiport Circuits

In this article, four low-loss compact waveguide phase shifters with self-compensating characteristics are proposed, studied, and demonstrated over the entire G-band (140–220 GHz) for the first time. The full-band phase shifting is achieved by combining opposite properties of the reference line and the main line. In addition, the proposed phase shifters can be easily fabricated by using a split-block machining technology in both E- and H-plane-cut configurations, therefore making them attractive for simultaneously combined E-plane and H-plane waveguide circuits and systems. Compared with the state-of-art techniques, the proposed phase shifters present competitive advantages in terms of bandwidth performance, phase shift range, low loss, simplicity, and compactness as well as fabrication flexibility. Four prototypes with 45° and 90° phase shifts, covering the whole G-band with both E-plane-cut and H-plane-cut configurations were fabricated and measured. Measured results confirm the anticipated performances and their potential applications for THz waveguide circuits and systems. To validate its feasibility, a 90° phase shifter was integrated with a multiport interferometric circuit as an application example. Compared with other reported works, the performance of the multiport circuit is significantly enhanced in terms of return loss, insertion loss, isolation, and phase error, which makes the phase shifter a very practical component for THz systems, in particular broadband multiport interferometric transceiver systems.