Absorptive tunable bandstop filter with wide tuning range and electrically tunable all-pass filter useful therein

摘要

This invention features an absorptive tunable bandstop filter with a wide tuning range including first and second branches of all-pass filter networks, an input power divider for splitting the input signal and passing approximately half of the input signal power through each branch of the all-pass filter networks, and an output power combiner for recombining the signal power from each branch of the all-pass filter networks, at least one of the branches of the all-pass filter networks being electrically tunable to provide an approximately 180° phase difference with similar amplitudes of the split signal power to be recombined at the output power combiner for rejecting but substantially absorbing selected frequencies.

主权项

1. An absorptive tunable bandstop filter with a wide tuning range comprising:
first and second branches of voltage-tunable all-pass filter networks configured such that the first branch includes at least a first all-pass filter having a first voltage tuning port and a second all-pass filter having a second voltage tuning port, and the second branch includes at least a third all-pass filter having a third voltage tuning port, the third tuning port of the third all-pass filter tied to a first fixed voltage to provide a first phase in said second branch and wherein said first phase is defined as a 0° reference phase relative to a phase of the first branch and one of the first all-pass filter and the second all-pass filter having a lower center frequency and the other having a higher center frequency and said third all-pass filter having a center frequency corresponding to said higher center frequency; an input power divider for splitting an input signal power and passing approximately half of the input signal power through each of said first and second branches of said all-pass filter networks; and an output power combiner for recombining the signal power from each of said first and second branches of said all-pass filter networks; the first branch of said all-pass filter networks being electrically tunable to provide an approximately 180° phase difference of said split signal power to be recombined at said output power combiner for rejecting but substantially absorbing selected frequencies.