Microstrip spurline band-pass filters

We present two novel spurline band-pass filters employing two and three parallel-coupled microstrip lines along with the approximate design equations. These filters exhibited insertion losses of less than 1 and 1.3 dB and return losses of more than 20 and 15 dB in the pass bands centered near 5 GHz. We obtained a good agreement between the measured and calculated performances. These filters behave similarly to the conventional open-circuited shunt-stub band-pass filters, but are smaller and have less radiation, dispersion, and sensitivity to the adjacent objects.