Investigation of the Use of Asymmetric Feed in Planar Filters Based on Matryoshka Geometry

Filters are essential devices in telecommunication systems, as they are responsible for selecting signals and, consequently, reducing possible interference that could damage the quality of the information. At GTEMA-IFPB, a geometry, called matryoshka has been used to make planar filters. Considering that, in order to obtain a certain frequency response, asymmetric feeding can be used as a design parameter, this work investigates this feeding. Parametric analysis is presented, describing how the different types of asymmetry influence the frequency response. Numerical and experimental results are presented for band-reject filters based on open square ring and matryoshka geometries, with rectangular rings, applied in the Wi-Fi range, specifically at 2.4 GHz. The results showed the miniaturization capacity and greater bandwidth for the asymmetric feed.