Miniaturized Substrate-Integrated Waveguide Bandpass Filter Using Symmetric Vertical Slots

A substrate-integrated waveguide (SIW) bandpass filter designed by introducing a vertical slot in the central metallic septum of the SIW is proposed in this paper. The input/output arrangement analysis and the stub variation in the port termination are also demonstrated, resulting in a wider bandwidth and better performance characteristics. The SIW bandpass filter (BPF) has a passband in the range of 18.23 GHz - 28.74 GHz depending on the stub variation arrangement with the central symmetric slot synthesized on a 0.5 mm thick planar RO 3003 substrate using a periodically arranged metal via holes. The proposed filter has excellent wide stopband rejection characteristics of -16 dB from 30 GHz to 40 GHz. Furthermore, the experimentally measured S-parameters of the filter are in good agreement with the simulated results; thus, the performance of the filter is validated.