A Compact Machinable 90° Waveguide Twist for Broadband Applications

We present a novel machinable 90° waveguide twist design suitable for broadband applications from microwave to terahertz frequency. The design achieves compactness and ease of fabrication by utilizing a series of quarter-wave transformer steps machined in split blocks. Three WR3.4 (220-330 GHz) prototypes with standard UG-387 flanges were fabricated and measured. The prototypes outperform two commercial waveguide twists in both return loss and insertion loss. The simulation and measurement results show that this design achieves a performance of -25 dB return loss for full waveguide bandwidth. Tolerance studies confirm that this design could be scaled up to terahertz frequency with modern computer numerical control (CNC) fabrication technology. In integrated waveguide systems, the waveguide twist design presented in this article can reduce losses at millimeter wave frequencies and achieve valuable weight savings in aerospace and other applications.