Miniaturized Sixteenth-Mode Substrate Integrated Waveguide Bandpass Filter with Helical Slot Lines

A novel miniaturized sixteenth-mode substrate integrated waveguide (SIW) bandpass filter with helical slot lines is proposed in this paper. Thanks to the application of the sixteenth-mode SIW resonator, the circuit size reduces to 6.25% of the traditional circular SIW resonator. In order to further miniaturization of the circuit size, the helical slot lines are etched into the sixteenth-mode SIW resonator, which can reduce another 10% circuit size. To verify the proposed design method, a bandpass microstrip line filter is designed and fabricated. The measurement results show that the central frequency is 2.3 GHz with 14% bandwidth and -1.0 dB insertion loss.