RF-Power-Activated and Signal-Tracking Tunable Bandstop Filters

Two new classes of RF-power-dependent tunable bandstop filters that share a common filter topology are presented in this paper. RF-power-activated tunable bandstop filters transition from a resonant-allpass response to a bandstop response in the presence of a high-power RF signal, allowing for optimum use of the spectrum when used to solve interference issues in a receiver. Signal-tracking tunable bandstop filters automatically tune their center frequencies to that of a high-power RF signal, eliminating the need for complex sensing and control systems. The theory and design as well as laboratory prototypes are presented for both. The RF-power-activated tunable bandstop filter prototype achieves a minimum allpass-state insertion loss of 2.5 dB and a bandstop-state attenuation of greater than 50 dB. The signal-tracking tunable bandstop filter prototype attenuates a high-power signal by greater than 33 dB over a frequency range of 251-304 MHz.