A novel symmetrical folding miniaturized substrate integrated waveguide tunable bandpass filter

In order to improve the utilization of spectrum resources, dynamic frequency allocation technology has become a method of spectrum saving. The research of electric tunable filter has received much attention in recent years. Substrate integrated waveguide (SIW) is a new technology of microwave integration in the field. The innovation of this article is to combine the SIW miniaturization technology with tunable technology. In this article, a miniaturized symmetrically folded substrate integrated waveguide (SFSIW) filter is designed. Based on the miniaturization of SIW filter, the center frequency can be adjusted electrically and the measured data show that the tunable filter can achieve eight states under the condition that the bandwidth below -3 dB remains approximately constant 300 MHz. The center frequency varies from 3.23 GHz to 3.9 GHz. The range of the filter's insertion loss is 1.2 dB to 2.04 dB, and the return loss is higher than 20.9 dB. This filter has practical value in the electronic countermeasures of military communication.