A novel compact microstrip lowpass filter with wide rejection band and sharp transition band using diamond-shaped resonator

Abstract

In this paper, a novel compact microstrip lowpass filter (LPF) using diamond-shaped resonator with wide rejection and sharp transition band is presented. The proposed filter has −3 dB cut off frequency at 2.6 GHz. The maximum insertion loss is only 0.1 dB in the passband and the rejection band extends from 2.89 to 20.84 GHz with the attenuation level better than −21 dB. The transition band is only 0.288 GHz, from 2.606 to 2.894 GHz with corresponding attenuation levels of −3 and −20 dB, respectively. The filter size is 12.4 × 11.5 mm2. The proposed filter is fabricated and tested, where the measurement results are in good agreement with the simulation results. The proposed LPF has compact size, simple structure, wide rejection band, and low insertion loss, where all of these characteristics are essential for LPF in the modern communication circuits.