A compact band-pass filter using transformed radial stubs with ultra-wide stopband

摘要

A compact microstrip band-pass filter (BPF) with ultra-wide-band rejection and compact size by using transformed radial stubs (TRS) is presented. Three TRS cells and two shunt stubs are used in the design. The implemented 2.5 GHz BPF with a bandwidth of 19% using three TRS cells demonstrates more than 22-dB rejection from 3 to 23 GHz (up to 9.2f). The measured passband insertion loss is 2.15dB and the board size of the BPF is only 0.251 × 0.211λ, without using any lumped elements.