Compact wideband combline filter using LCP bonded multilayer PCB technology

A novel compact wideband third-order combline filter using LCP bonded multilayer PCB technology is proposed in this letter. Thanks to the use of the proposed new multilayer technology, it not only can very conveniently realize a very strong coupling to achieve a wideband, but also can achieve more miniaturized size in comparison of the conventional design based on the LCP technology. In addition, two dissimilar quarter-wavelength stepped-impedance resonators with tapped input/output coupling were adopted in the design, which resulted in two transmission zeros in the upper stopband to improve the upper stopband performance. The predicted results are verified by the experiments, which show the fabricated filter has a 3 dB fractional bandwidth of 81% operating at 0.95GHz, 6^th harmonic suppression with two transmission zeros and a very compact size of 0.153λ_g*0.06λ_g (λ_g is the guided wavelength at the center frequency).