Millimeter wave cross-coupled bandpass filter based on groove gap waveguide technology

Abstract

This paper presents a new type of cross coupled low loss and high selectivity bandpass filter operating at millimeter wave band. The filter is designed based on groove gap waveguide technology. A Ka-band 4 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> -order bandpass filter is proposed, designed and fabricated. Cross coupling between a one pair of non-adjacent resonators has been introduced to produce two transmission zeros at the frequencies below and above the passband. The designed filter, which operates at a central frequency of 35.65 GHz with a fractional bandwidth of 1%, is fabricated using CNC milling machine. A reasonable agreement between the measured and simulated results has been obtained. Most design specifications are met although the measured insertion loss and return loss are not as good as the predicted which may be due to discrepancy between the material properties and fabrication errors.