More accurate model of the coupled microstripline section

A parallel coupled microstripline bandpass filter was designed to operate at a frequency of 10 GHz with a 10% bandwidth. The theoretical transmission-loss response was predicted for a coupled microstripline section using a more accurate model. A discrepancy of about 2% remained between the predicted and the measured centre frequencies of the filter. This was partly attributed to the possible influence of nonadjacent resonators which were not included in the model. Further evidence of the presence of such a couplig phenomenon between nonadjacent resonators was demonstrated experimentally.