Miniaturized dual-band waveguide band-pass filter

In this paper, a new compact H-plane dual-band waveguide band-pass filter is proposed. The filter is composed of one thick dielectric substrate with copper on both sides. Three complementary split ring resonators (CSRRs) and three asymmetric resonator slots are etched on copper layers. The asymmetric resonator slots on the single copper layer can generate two transmission zeros to form a wide pass-band. The CSRRs aim to introduce another transmission zero in the wide pass-band and strengthen the out-of-band suppression. Because of the short distance, two copper layers interact with each other, strengthening the flatness of pass-band and enhancing the selectivity of the filter. The isolation between two pass-bands has also been greatly improved. The proposed filter has a dual-band band-pass response and operates at 8.69/11.63GHz. Insertion loss of each frequency is at around 0.5 dB and the 3dB bandwidth is 0.48/0.54 GHz, respectively. The prototype is measured with fairly good performance, but the insertion loss is a little higher. Also, the total length of this filter is only 3.245mm, which is much smaller than similar filters.