Microstrip Interdigital Bandpass Filters: Design analysis

Conventionalmicrostriplowpass and bandpass filters such as stepped-impedance filters, open-stub filters, semilumped element filters, endand parallel-coupled half-wavelength resonator filters, hairpin-line filters, interdigital and combline filters, pseudocombline filters, and stub-line filters are widely used in many RF/microwave applications. Modern RF and microwave communication systems, specifically mobile and satellite communications required high performance, wide band filters with linear phase. Most communication systems require an RF front end, where RF/microwave filters and low noise amplifiers perform analog signal processing. Microwave filters are commonly used in receivers and transmitters operating in 800 MHz to 30 GHz frequency range. A lot of research work has been done in design and analysis of RF/microwave filters such as, design of low pass, high pass and band-pass, and band-stop filters using lumped elements or microstrip techniques [1-3], application of DGS, EBG, in microwave filters [4-8], etc. Microwave band-pass filters are essential components in the development of wireless communication systems. The advanced performance of modern communication systems has imposed stringent requirements on filters including compact size, minimal insertion loss, low cost, and high selectivity. It is the purpose of this paper to present the designs and analysis and advantages of Interdigital Bandpass filters with instructive design examples.