Design of a dual-band bandpass filter with miniaturization and high selectivity

In order to meet the application requirements of C-band satellite communication system, a dual-band bandpass substrate integrated waveguide filter with miniaturization and high selectivity is proposed. The first passband of the filter is provided by an L-shaped resonant slot etched in the top layer of the quarter-mode substrate integrated waveguide cavity, and the second passband is provided by a new right/left-handed structure. The L-shaped resonant slot can act as a quarter-wavelength resonator to excite the fundamental mode in the cavity to produce a response at low frequencies; the new right/left-handed structure increases the fork-finger capacitance value compared with the conventional structure, then reduces the resonant frequency. Through simulation optimization and testing, the center frequencies of the dual-band bandpass filter are 3.9 GHz and 6.2 GHz with relative bandwidths of 3.3% and 2.1%, and the attenuation between the passbands is better than 70 dB, and three transmission zeros exist outside the passbands with good frequency selectivity. It is shown that the proposed filter has the characteristics of small size and high selectivity, which is very suitable for integration in the front-end system of satellite communication.