Provided is a polyphase filter, which is capable of achieving amplitude matching and phase matching while achieving a low insertion loss with a single-stage configuration. A first variable resistor and a second variable resistor have resistance values that are equal to each other, and the resistance values are set so as to correct an amplitude error between orthogonal signals of outputs of a first output terminal to a fourth output terminal. A first variable capacitor, a second variable capacitor, a third variable capacitor, and a fourth variable capacitor have capacitance values that are equal to one another, and the capacitance values are set so as to correct a phase error between the orthogonal signals of the outputs of the first output terminal to the fourth output terminal.

Self-interference cancellers are provided. The self-interference cancellers can include multiple second-order, N-path G.sub.m-C filters. Each filter can be configured to cancel self-interference on a channel of a desired bandwidth. Each filter can be independently controlled using a variable transmitter resistance, a variable receiver resistance, a variable baseband capacitance, a variable transconductance, and a variable time shift between local oscillators that control switches in the filter. By controlling these variables, magnitude, phase, slope of magnitude, and slope of phase of the cancellers frequency responses can be controlled for self-interference cancellation. A calibration process is also provided for configuring the canceller.

Provided is a polyphase filter, which is capable of achieving amplitude matching and phase matching while achieving a low insertion loss with a single-stage configuration. A first variable resistor and a second variable resistor have resistance values that are equal to each other, and the resistance values are set so as to correct an amplitude error between orthogonal signals of outputs of a first output terminal to a fourth output terminal. A first variable capacitor, a second variable capacitor, a third variable capacitor, and a fourth variable capacitor have capacitance values that are equal to one another, and the capacitance values are set so as to correct a phase error between the orthogonal signals of the outputs of the first output terminal to the fourth output terminal.

An active filter comprising an operational amplifier, and a controller configured to control the bandwidth of the operational amplifier based on a filter cutoff frequency setting and/or a noise performance setting.

A tank circuit (200) includes a tunable resonator subcircuit (210) having a first control input and having an effective parallel resistance that varies with tuning of the tunable resonator subcircuit (210). The tank circuit (200) further comprises a variable negative-resistance subcircuit (250) having a second control input and coupled in parallel to the tunable resonator subcircuit (210), where the variable negative-resistance subcircuit (250) is configured to provide a variable negative resistance, responsive to the control input, so as to increase the effective parallel resistance of the tank circuit (200).

A variable filter for an RF circuit has a signal loop comprising a signal input port and a signal output port, and a plurality of circuit elements connected within the signal loop. The plurality of circuit elements comprise a multi-pole resonator comprising a plurality of frequency tunable resonators and an adjustable scaling block that applies a gain factor. Adjacent frequency tunable resonators within the multi-pole resonator are reciprocally coupled. A controller is connected to tune the multi-pole resonator and to adjust the gain factor of the adjustable scaling block such that the signal loop generates a desired bandpass response.

A method and apparatus for modifying or controlling a resonator connected to a signal loop having an input, an output, and a closed loop frequency response. The signal loop has a primary resonator having a primary frequency response. There is at least one adjustable resonator having an adjustable frequency and a secondary Q-factor. An adjustable scaling block applies a gain factor. A controller is connected to the at least one adjustable resonator and the adjustable scaling block. The controller has instructions to adjust the closed loop frequency response toward a desired closed loop frequency response by controlling the adjustable frequency of the at least one adjustable resonator and the gain factor of the adjustable scaling block.

Techniques to maintain gain flatness in the frequency response of a passband signal over a circuit chain. The techniques may be employed in the receive chain of a millimeter wave band wireless receiver, in the transmit chain of a millimeter wave band wireless transmitter, or in both the receive chain and the transmit chain of a millimeter wave band wireless transceiver. The techniques include mismatching the input and output impedance of a passive low pass filter used in the chain to peak the gain of the passband signal at or near the cutoff frequency (Fc) of the filter.

A device includes a controller and an adaptive continuous-time filter that includes a control input and a first array of elements. The controller generates a digital word responsive to a time constant and compares a select bit of the digital word to a corresponding reference word to generate a control bit. The controller includes a duplicate array of elements, and applies the control bit to an adjustable element of the duplicate array of elements to modify the time constant. The controller provides the output word to the control input of the adaptive continuous-time filter to generate a filter response that accounts for effects of semiconductor process variation in the first array of elements.

A tank circuit includes a tunable resonator subcircuit having an effective parallel resistance that varies with tuning of the tunable resonator subcircuit. The tank circuit further comprises a variable negative-resistance subcircuit coupled in parallel to the tunable resonator subcircuit, where the variable negative-resistance subcircuit is configured to provide a variable negative resistance, so as to increase the effective parallel resistance of the tank circuit. A control circuit is configured to increase the negative resistance presented by the variable negative-resistance subcircuit in response to a change in the tunable resonator subcircuit that lowers the resonant frequency of the tunable resonator subcircuit.