Patent ID: 8981873
Filing Date: 2015-03-17
Classification: H03H

Abstract:
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.