Design and performance of novel printed-circuit spurline bandpass filters

Novel spurline bandpass filters are presented. Approximate design equations are derived. Two microstrip spurline bandpass filters employing two- and three-conductor spurline resonators, with passbands centered near 5 GHz, have been designed and tested with less than 1- and 1.3-dB insertion losses and more than 20- and 15-dB return losses in the passbands, respectively. Good agreement between the measured and calculated results has been observed. The filters behave very similar to the conventional open-circuited shunt-stub bandpass filters, but are more compact and less radiative, sensitive to the adjacent objects, and dispersive, making them more attractive.<>