Autonomously-Switchable Bandstop Filters with Integrated Sensor and Driver Circuitry
The integration of a resonant power sensor, switch driver circuit, and switchable bandstop filter is shown in this paper. The co-design of these circuits enable a switchable bandstop filter that autonomously responds to an unexpected above-threshold interfering signal within its bandwidth in orders of magnitude less time than conventional switchable or tunable bandstop filters. In contrast to limiter circuits that are based on PIN diodes that are switched by RF power, the proposed autonomously-switchable bandstop filter has high linearity in all states. A third-order suspended-stripline prototype switchable bandstop filter with a second-order resonant power sensor was fabricated and measured to test the technique at 2.15 GHz. Within 14–22.2 ns of the arrival of an above-threshold interfering signal, the fabricated driver circuit switches a bandstop filter with 18 dB attenuation and an OIP3 value of over 38 dBm.