Compact UWB Bandpass Filter with Multiple Ultra Narrow Notched Bands

Abstract

An ultra-wideband (UWB) bandpass filter (BPF) with multiple ultra narrow notched bands is presented in this paper. The notched band inside the UWB passband is implemented by embedding a pair of parallel coupled lines into the interference line. The central frequency and the bandwidth of the notched band can be easily controlled by the electrical length and coupling coefficient of the coupled lines. For verification, two UWB BPFs, filter I with a single notched band at 5.8 GHz and filter II with dual notched bands at 5.8 and 8.0 GHz respectively, are designed, simulated and measured. Good agreement is observed between the measurements and simulations. The results show that the proposed filters have compact sizes, ultra narrow notched bands and can be easily fabricated with the conventional microstrip techniques.