Chebyshev type-I low pass filter using annular ring resonator: A comparative performance analysis for different substrates

Abstract

In this letter, compact microstrip Chebyshev function low pass filters (LPFs) with sharp roll-off based on annular ring resonators (ARRs) on various substrates and it's design theory are demonstrated. To fabricate ARRs, Chebyshev type - I function with fixed side lobe level (SLL) and method of moments (MOM) for numerical analysis are applied. The ARRs inscribed on the ground plane, behave as shunt connected capacitances with low radiation, nevertheless the 50 Ω transmission line on the upper plane provide the total transmission to realize the Chebyshev function response. Consequently, RT/Duroid 5880 prevails with low insertion loss (<0.6 dB), wide stopband, very sharp roll-off (>90 dB/GHz) and isolation up to 70 dB in the stopband. The frequency responses of the device from the two different software's are in good agreement with the known theoretical data.