A New Design of Quasi-Elliptic High-Low Microstrip Lowpass Filter Using SC-Defected Ground Structure Technique

This paper proposes for microwave communication areas a new design of Quasi-Elliptic High-Low Microstrip Lowpass Filter (QE-HL-MLPF) based on a Semicircular Defected Ground Structure (SC-DGS). The filter design employs a new technique of cascading high (Hi) and low (Lo) impedance elements in simulating the ladder LC lumped-circuit prototype. MATLAB and full wave electromagnetic simulator are used to model the proposed design and extract the scattering parameters. A semicircular-shaped resonator is implemented into the 4
^th
order Butterworth filter structure which uses a Quasi-Elliptic function as a systematic design process, providing a sharp roll-off at 2.5 GHz, good rejection of less than -30dB up to 3 GHz, and low return loss of approximately -20dB over the entire filter passband. The filter parameters show interesting insertion loss of -3.025dB at a cut-off frequency equals to 1.53 GHz, and wide stopband with efficient harmonics suppression for more than 2 GHz from the cut-off frequency.