Development of new miniaturised bandpass filter having ultrawide bandwidth

A new, compact, very-broadband bandpass filter, consisting of two-parallel-conductor short-circuited spurline resonators, quarter-wavelength long, is described. Approximate design formulas for the filter are derived. The chain matrix of the resonators is also obtained and used in predicting the filter response. It is found that this filter possesses a very wide bandwidth, more than 5:1. A microstrip filter having a passband from 1.8 to 9.2 GHz has been designed and tested with less than 1 dB insertion loss. There is also a reasonably good agreement between the experimental and theoretical performances. The developed filter is very attractive for wideband microwave integrated circuits due to its compactness and very wide bandwidth