A filter includes multiple filter circuits. The filter circuits are coupled in series between an input terminal and an output terminal, to generate an output signal according to an input signal. One of the filter circuits operates as an active filter circuit or a passive filter circuit according to amplitude of the input signal.

A filter includes multiple filter circuits. The filter circuits are coupled in series between an input terminal and an output terminal, to generate an output signal according to an input signal. One of the filter circuits operates as an active filter circuit or a passive filter circuit according to amplitude of the input signal.

According to one embodiment, in a biquad filter, an output terminal of a first integrator is connected to an input terminal in a negative pole side of a second integrator, an output terminal of the first integrator is connected to a first input terminal in a negative pole side of an adder through the inversion amplifier, an output terminal of the second integrator is connected to a second input terminal in the negative pole side of the adder, an input terminal to which an input signal is input is connected to a third input terminal in the negative side of the adder, and an output terminal of the adder is connected to an input terminal in a negative pole side of the first integrator.

Systems and methods for estimating frequency and bandwidth of unknown signals using learned features of a filter pair for the purpose of detecting, separating and tracking these signals in an electronic receiver. The techniques could be part of a signal cueing system that initiates signal detection, separation and tracking or a signal separation and tracking system which is initialized by the cueing system and adaptively updates frequency and bandwidth estimates so as to continuously separate and track signals after initial detection. The methodology is to train the filter responses using machine learning by creating a grid of training data based on signal examples that cover a span of frequencies and bandwidths. The system estimates frequency and bandwidth in real time, inputs those estimates into interpolating lookup tables to retrieve filter coefficients, and provides those filter coefficients to a tunable tracking filter.

A high-yield, tunable radio frequency (RF) filter includes a plurality of process-dependent capacitors and a plurality of non-volatile RF switches. Each of the plurality of process-dependent capacitors is connected to at least one of the plurality of non-volatile RF switches. An auxiliary capacitor in the plurality of process-dependent capacitors is engaged by an ON-state non-volatile RF switch in the plurality of non-volatile RF switches. A primary capacitor in the plurality of process-dependent capacitors is disengaged by an OFF-state non-volatile RF switch in the plurality of non-volatile RF switches. The auxiliary capacitor substitutes for the primary capacitor.

A reconfigurable analog filter includes a transimpedance amplifier configured to convert a current signal into a voltage signal, an input capacitor configured to form a current-mode low pass filter together with an input impedance of the transimpedance amplifier, a variable load circuit including at least one switch configured to selectively close a circuit path to provide a resistor and/or a capacitor as a load of the transimpedance amplifier according to a control signal, and a low pass filter configured to filter the voltage signal.

A reconfigurable analog filter includes a transimpedance amplifier configured to convert a current signal into a voltage signal, an input capacitor configured to form a current-mode low pass filter together with an input impedance of the transimpedance amplifier, a variable load circuit including at least one switch configured to selectively close a circuit path to provide a resistor and/or a capacitor as a load of the transimpedance amplifier according to a control signal, and a low pass filter configured to filter the voltage signal.

A system includes a conductive chassis having a first ground terminal. The conductive chassis couples to a switching circuit having a second ground terminal and having a first switching frequency. The second ground terminal is electrically isolated from the first ground terminal. An active electromagnetic interference (EMI) filter has an output and first and second inputs, and is configured to receive a first AC voltage having a second switching frequency at the first input, receive a second AC voltage having the second switching frequency at the second input referenced to the first ground terminal, sense noise having the first switching frequency on at least one of the first or second inputs, and generate an injection signal at the output based on the detected noise. The output couples to at least one of the first or second inputs.

A system includes a conductive chassis having a first ground terminal. The conductive chassis couples to a switching circuit having a second ground terminal and having a first switching frequency. The second ground terminal is electrically isolated from the first ground terminal. An active electromagnetic interference (EMI) filter has an output and first and second inputs, and is configured to receive a first AC voltage having a second switching frequency at the first input, receive a second AC voltage having the second switching frequency at the second input referenced to the first ground terminal, sense noise having the first switching frequency on at least one of the first or second inputs, and generate an injection signal at the output based on the detected noise. The output couples to at least one of the first or second inputs.

A circuit includes a filter, a first inverter, and a second inverter. The filter is coupled to an input of the first inverter. The second inverter includes an input and an output. The input of the second inverter is coupled to the output of the first inverter. The output of the second inverter is coupled to the input of the first inverter.