Electrically regulated filter having a selectable stop band

摘要

A band-rejection filter (1) comprising transmission line resonators (2, 3) further comprises switching means (7, 8) to provide an electrical connection between each transmission line resonator and a certain fixed potential in response to a certain control signal. The fixed potential is advantageously the ground potential, whereby the control signal causes the resonators to be shunted and the frequency response of the filter to be changed into a low-pass-type frequency response.