Compact Integrated Lumped Element LCP Filter

The filter presented in this letter is a novel, compact, 4-pole, UHF-band integrated lumped element filter with a 20% fractional bandwidth operating at center frequency f0=500 MHz with a 17 dB passband return loss and a wide upper stopband with high rejection. The circuit was designed to minimize the overall footprint, as well as ensuring a wide, high attenuated stopband. This was achieved by building on previous work using LCP as a fabrication medium which implemented a block of shared vias; however, by adding a new controlled coupling between two capacitors, the stopband performance was significantly improved. The final filter dimensions are 0.03λg×0.06λg, and the out-of-band rejection is significantly larger than its predecessor at 50 dB up to 3f0 and 40 dB up to 5f0 with a stopband width extended to 7 times the center frequency.