MICROSTRIP LOW PASS FILTER DESIGNS USING DEFECTED GROUND STRUCTURE

Dhara Gadhvi, Urvik Shah

Abstract: The microwave filters play an important role in most RF/microwave applications. They are designed to remove undesired harmonics to reduce the system noise or to remove spurious mixing products. DGS slot with an interdigital shape are introduced here in two elliptic low pass filter designs. Here a fifth order low pass filter was designed, simulated and fabricated for a cut off frequency of 3GHz. Finally a prototype model were designed based on the simulation results obtained. These prototype filter designs have more than 20 dB of stop band rejection and a good return loss in the pass band. The fabricated results proved to be better than the simulation results. In the first low pas filter design the central aperture was replaced with the interdigital slot structure which improved the stop band response at the resonant frequency around 7.8 GHz. To improve the stop band rejection two interdigital structures were introduced in the bottom layer (Ground)

Keywords: Defected ground structure (DGS), low pass filters, microstrip filter, transmission zero.

DOI: https://doi.org/10.15623/ijret.2015.0410009