Evanescent mode compact waveguide filter

An evanescent mode waveguide filter is designed. Simulations show that the length and width can be reduced by 40% and 50% respectively, compared with a conventional directly- coupled waveguide filter. This is verified by the tested results from an order-7 sample filter. From 7.55 GHz to 8.25 GHz, the insertion loss is lower than 0.45 dB and reflection lower than -20 dB.