Design of Optimized Minimum Inductor Bandpass Filters

A design methodology for optimized minimum inductor bandpass filters (BPFs) is presented. Design curves are provided to determine the filter order for a required out-of-band rejection as a function of bandwidth (BW). Coefficients for BWs from 10% to 100% in steps of 10% for different filter orders and two different transmission zero placements are provided. For both cases, the required in-band return loss is larger than 10 dB. Using the derived coefficients, filters with required rejections can be designed for a given center frequency. To validate the design methodology, five discrete element filters with different BWs are designed and fabricated at a center frequency of 1.5 GHz. Furthermore, to show the application of the minimum inductor filters in complementary metal-oxide-semiconductor (CMOS), an S-band BPF in 0.13-μm CMOS, with 60% BW, is designed and fabricated. The out-of-band rejection of the fabricated filter is larger than 50 dB.