Design of Lowpass Filter with Improved Roll Off Factor using Coin Shape Fractal DGS

Abstract

This paper presents the design of lowpass planar filter with improved roll of factor. To improve the performance figures of filter such as return loss, roll off factor, compactness, etc. coin shape fractal defected ground structure (DGS) has been embedded in the ground plane of the filter. The proposed filter gives improvement of roll off factor about 5 times as compared to traditional filter design technique. Laboratory prototypes of all three configurations (without DGS, with 1^st iteration DGS, with 2^nd iteration DGS) have been fabricated and measured the performance parameters using vector network analyzer. The simulated and measured results are almost matched with each other.