Ka-Band Gap Waveguide Coupled-Resonator Filter for Radio Link Diplexer Application

Gap waveguide technology represents an interesting alternative as low-loss, cost-effective, and high-performance transmission line and package of microwave and millimeter-wave systems. A Ka-band coupled-resonator filter for a radio link diplexer, which requires high selectivity to isolate transmit and receiving channels, is proposed and realized using gap waveguide technology. The band-pass filter, which has a central frequency of 37.37 GHz and a pass bandwidth of 560 MHz, is fabricated between two parallel metal plates, leaving an air gap between them. After milling one of the plates, silver-plating is applied on them. Measurements show a minimum in-band insertion loss of 1 dB and agree quite well with simulations.