Dual-mode SICL bandpass filter with via based perturbation technique forKu-band

This Letter presents a dual-mode substrate integrated coaxial line (SICL) based bandpass filter for K-u-band application. The proposed bandpass filter is realised by exciting the even and odd modes in an SICL ring resonator. A novel perturbation technique to control the coupling between orthogonal modes is realised by varying the width of the outer conductor formed by metallic vias in this planar coaxial line. Further, the effect of perturbation length and inset on resonant frequency and attenuation pole is studied. The two transmission zeros produced close to the pass band provide excellent selectivity and reject spurious frequencies up to 1.9f(o). The proposed SICL based filter is manufactured using low cost PCB fabrication process. Experimental results indicate an insertion loss of 1.18 dB and a 3 dB bandwidth of 360 MHz centred at 13.83 GHz. The self packaged SICL filter occupying only 0.31 lambda(2)(g) lateral area is suitable for implementation in densely integrated systems.