Modelling and validation of microwave LPF using modified rectangular split ring resonators (SRR) and defected structures

We propose a design of lowpass filter (LPF) using modified rectangular split ring resonator (SRR) that acts as a unit cell of metamaterials. Initially, a conventional LPF of 4.5 GHz is designed and the low impedance line is replaced to produce a sharp cut-off with a modified SRR structure. A brief parametric study is done to establish a relationship between the inner perimeter of the SRR to the cut-off frequency of the proposed LPF. Same study is also done for the outer perimeter. Using this relationship, another LPF of 2.4-GHz cut-off frequency is obtained. Defected ground structures (DGS) and microstrip structures (DMS) are incorporated with the 2.4-GHz LPF structure for the removal of harmonics and better pass-band characteristics. The IE3D simulation results and the circuit simulation results are in good agreement with the measured results. The obtained structure can thus be used for several useful applications such as in Bluetooth, Wi-Fi, cordless phones, computers, and other wireless communication devices.