Compact W-band E-plane Waveguide Filter with High Selectivity

In this letter, an E-plane substrate is inserted into the W-band standard waveguide to construct a bandpass filter (BPF) with high selectivity. This E-plane waveguide BPF with three transmission zeroes (TZs) is developed by using a novel compact beeline resonant cell (CBRC) and uniform-impedance resonant cells (UIRCs). It is shown that the locations of the TZs can be designed. Three TZs, with two located in the upper stopband, and the other one located in the lower stopband, are produced by a novel CBRC and two UIRCs, respectively. For verification, the BPF prototype is designed, fabricated and measured, whose total length is just 3.21 mm, namely, less than 0.83 λ g ( λ g is the waveguide wavelength at the center frequency). Moreover, the minimum insertion loss (IL) is only 1.02 dB, and the measured return loss (RL) of the proposed BPF is greater than 14 dB at the frequency range of 94 to 99.3 GHz. The 3-dB fractional bandwidth (FBW) is 6.5%, which is from 93.6 to 99.9 GHz. Good agreement between the simulations and measurements validates the design method. The proposed W-band E-plane waveguide BPF and the efficient design method used in their design are believed to be of importance for future filter device applications in millimeter wave systems.