SIW (substrate integrated waveguide) quasi-elliptic filter based on LTCC for 60-GHz application

This paper presents substrate integrated waveguide (SIW) cavity resonator and SIW quasi-elliptic filter with low insertion loss and high selectivity based on LTCC for 60-GHz application. The SIW cavity resonators with high Q factor are suggested and applied for the filter having low insertion loss and high selectivity, the resulting Q value and the resonance frequency are 224.5 and 60.371 GHz, respectively. In the filter design, the quasi-elliptic filter using positive and negative couplings is applied to get high selectivity, the positive and negative couplings are evaluated by the holes between resonators and the slots on ground planes, respectively. The proposed SIW quasi-elliptic filter exhibits an insertion loss 1.77 dB at 60.8 GHz and the return loss is better than 10.2 dB with a 3-dB fractional bandwidth of 11 % (6.92 GHz). The measured insertion loss is lower and the selectivity is higher than those in previous works due to the effects of the high Q resonators and quasi-elliptic structure adapting the negative coupling. The overall size of the fabricated filter is 4.6 mm times 2.8 mm times 0.2 mm.