A v-band compect bandpass filter in Si-BCB technology using the coupled-line resonators

This letter presents a V-band compact bandpass filter in Si-BCB technology. The coupled line resonator employing the tight coupling-broadside coupled-structure is used for filter design and the length of the coupled line resonator is minimized by increasing the coupling level between lines. In this work, the resonance at 60 GHz is obtained by the length of λ_g/10 with the coupling level of 0.9. And the positive and negative couplings are realized by adjusting the coupling direction of the resonators, such as parallel and antiparallel. The V-band bandpass filter is designed and evaluated in BCB layers on Si substrate using 4^th order quasi-elliptic function based on the optimized coupled line resonators and the couplings between them. The measured center frequency of the fabricated filter is 60.4 GHz and the minimum insertion loss and the return loss and 3-dB FBW of 17.5 % are 3.2 dB and better than 13 dB, respectively, and the fabricated filter occupies only the area of 0.29 mm². Finally, the designed filter is compared with previously reported filters using CMOS technology by adopting the factor of merit (FOM) of filter, and the proposed filter in this work has higher FOM value in the comparison with other filters without the sacrifice in compactness.