Identification of Most Suitable Dielectric Substrate for UWB Bandpass Filter

Abstract

In this paper, the performance of an Ultra-Wideband (UWB) bandpass filter with three commonly used dielectric substrates has been analyzed and presented[1-2]. The selection of suitable dielectric substrates is very important in order to minimize dielectric losses in microstrip lines. PCB (Printed Circuit Board) with suitable dielectric substrates are used extensively in the design of microstrip lines and have emerged as the best technique with low cost, compact size, and high accuracy. A good understanding of the details of the electrical properties of dielectric substrates can improve the designer’s models and circuit performance. It has become extremely challenging to design such devices as the geometric structures become extremely small at microwave frequencies[3-4].

Fig 1 indicates the PCB layout of the UWB bandpass filter designed with characteristic impedance Zo=50Ω using RT Duroid dielectric substrate having a thickness of 1.6 mm. The design approach of the UWB microstrip bandpass filter is carried out using coupled simplified composite Electromagnetic Bandgap (EBG) resonator structures with inter-digital coupled feed lines and meets all the UWB requirements. The results are compared with FR4 and Alumina-based resonators and the response is presented in Fig. 2. The effect of the change in the full-wave Electromagnetic (EM) algorithm on the insertion loss and other characteristics of the UWB bandpass filter is presented. Table 1 indicates that the best results are obtained with RT Duroid compared to FR4 and Alumina.