Design and development of broadband gap waveguide‐based 0‐dB couplers for Ka‐band applications

Abstract

The design and fabrication of a wideband millimetre-wave 0-dB coupler is proposed in this paper using gap waveguide technology for low-loss and high-power applications in 30-GHz frequency band. To overcome the fabrication challenges in millimetre-wave frequencies, the gap waveguide technique is utilised. Two gap waveguide-based coaxial- and waveguide-fed 0-dB couplers are designed with broadband performance, high return loss, acceptable coupling flatness and high isolation. For verifying the performance of the proposed structures, a prototype of the waveguide-fed 0-dB coupler is manufactured and measured. The measurement results show that the return and insertion losses and the isolation of the fabricated 0-dB coupler is better than 18 dB, 0.5 and 18 dB, respectively, in the specified frequency range from 26.2 to 34 GHz. Moreover, the breakdown power level of the proposed millimetre-wave structures is in kW orders to satisfy the high-power requirements.