Miniaturised multi‐channel millimetre wave filter bank

This Letter presents a miniaturised multi‐channel millimetre‐wave filter bank implemented by stripline and substrate integrated waveguide (SIW). Since the orthogonal transverse electric mode and transverse electromagnetic mode can coexist in the same hybrid structure cavity and be transmitted almost without mutual interference, embedding stripline into SIW to miniaturise the size of the filter bank is achievable. A prototype composed of four bandpass filter units working at X‐band is designed, fabricated and tested. Measurement results show that the proposed device has four independent channels with a good quality of bandpass filtering and the isolation among ports of different filter units are relatively high. The proposed prototype has 39.5% volume reduction than traditional stacking structure as well as good scalability, which has broad prospects in the application of next‐generation wireless communication system.