A Full WR-3 Band and Low-Loss 90° Waveguide Twist Based on CNC

Modern terahertz (THz) receivers used in radio astronomy are aimed at developing multipixel instruments, in which the polarization twists are often required. In this article, an allin-one and low-loss 90° waveguide twist is developed for working over the full WR-3 band. A square waveguide junction with a doubler-corner-cut is integrated between the H-plane and E-plane waveguides to provide 90° polarization rotating. All the vertical corners are fillet to comply with the fabrication constraints of the current computer numerical control (CNC) machining. The prototype integrated with a twist section of one-fourth wavelength thickness and two straight waveguides with total 12 mm length is processed through means of split block. Measured results exhibit a low insertion loss of 0.4 dB and better than 25 dB return loss across the entire WR-3 band, which are all in good agreement with the simulations. Such excellent performance is highlighted comparing with the reported THz waveguide twists, which indicates that this compact design is well suited for the delicate CNC-machining restrictions in the THz band.