Substrate Integrated Waveguide Quasi-Elliptic Millimeter Wave Filter

In this paper, a novel substrate integrated waveguide quasi-elliptic filter based on low temperature co-fired ceramic (LTCC) technology is proposed. To get two controllable transmission zeros below and above the pass-band, mixed electrics and magnetic energy coupling is used for filter design. By using mixed energy coupling, only three resonators are required to build up two transmission zeros, three SIW resonators are laminated vertically with compact size. The electric and magnetic mixed coupling is realized by etching a narrow slot and a circular hole on the common metal layer between adjacent resonators, in which the electric and magnetic coupling can be controlled by adjusting the length of slot and the radius of circular hole, and a controllable transmission zero can be produced below or above the pass-band. The simulation results of the filter are as follows: the center frequency is 29.7 GHz, a 3 dB fractional bandwidth of 3%, the return loss is better than 20 dB, and the frequencies of the two transmission zeros are 27.58 GHz and 31.12 GHz, the upper-stopband rejection is more than 30 dB from 31 GHz to 46 GHz.