High-Performance LPF Using Coupled C-Shape DGS and Radial Stub Resonators for Microwave Mixer

A high-performance microstrip low-pass filter (LPF) with low cutoff frequency, negligible passband insertion loss, very sharp transition band, and deep ultra-wide stopband is designed, fabricated and measured. The presented filter is realized using three types of resonators which are coupled C-shape defected ground structure (C-CDGS), mirrored series-resonant branch loaded by radial stub and high impedance line loaded by radial stub. A novel equivalent circuit model of the C-CDGS resonator is created, and its corresponding parameters are also extracted. The proposed filter is experimentally verified through the measured results which show good agreement with electromagnetic simulations.