An acoustic-wave device with active calibration mechanism is provided. The acoustic-wave device with active calibration mechanism includes at least one acoustic-wave duplexer, a voltage-controlled oscillator (VCO), a frequency discriminator and a control circuit. The acoustic-wave duplexer includes a TX filter and an RX filter. The voltage-controlled oscillator includes a calibration resonator and a tunable negative impedance circuit. The TX filter, the RX filter and the calibration resonator are disposed on the same piezoelectric substrate. The frequency discriminator generates a calibration signal according to a frequency deviation of the calibration resonator. The control circuit is connected to the acoustic-wave duplexer and the frequency discriminator. The control circuit adjusts an operating frequency of the TX filter or an operating frequency of the RX filter according to the calibration signal.

A high order filter circuit is integrated by a plurality of the low order filter circuits. Before correcting the high order filter circuit, switch units may restore the high order filter circuit to the low order filter circuits for correction, and then combine the corrected low order filter circuits to form the original high order filter circuit.

Certain aspects of the present disclosure are generally directed to a tunable active filter and a method of calibrating a tunable active filter. One example apparatus is a filter circuit that generally includes a resistor-capacitor (RC) topology tunable active filter comprising a first amplifier, a second amplifier, and a feedback path coupled between an input of the first amplifier and an output of the second amplifier. The filter circuit also includes a negative transconductance circuit coupled to a first node of the tunable active filter.

RF communications circuitry, which includes a first tunable RF filter and a first RF low noise amplifier (LNA) is disclosed. The first tunable RF filter includes a pair of weakly coupled resonators, and receives and filters a first upstream RF signal to provide a first filtered RF signal. The first RF LNA is coupled to the first tunable RF filter, and receives and amplifies an RF input signal to provide an RF output signal.

A low order filter circuit having a frequency correction function, a frequency correction method for a low order filter circuit, and a high order filter circuit are provided. An analog to digital converter (ADC) may detect a peak of a signal processed by a second order filter unit, and after comparison and determination are performed by a digital correction unit, a frequency control signal is outputted as a feedback to a notch filter or a band-pass filter in the second order filter unit where frequency adjustment is performed. The high order filter circuit is integrated by a plurality of the low order filter circuits. Before correcting the high order filter circuit, switch units may restore the high order filter circuit to the low order filter circuits for correction, and then combine the corrected low order filter circuits to form the original high order filter circuit.

The cut-off frequency of an electronic filter having a nominal transfer function and a nominal cut-off frequency is estimated by: applying a first signal at a first frequency to an input of the filter while sampling an output of the filter in order to obtain a first magnitude measurement, the first frequency being less than the nominal cut-off frequency; applying a second signal at a second frequency to the input of the filter while sampling the output of the filter in order to obtain a second magnitude measurement, the second frequency being greater than the nominal cut-off frequency; and estimating the cut-off frequency of the filter based on the nominal transfer function, the first magnitude measurement, and the second magnitude measurement.

An acoustic-wave device with active calibration mechanism is provided. The acoustic-wave device with active calibration mechanism includes at least one adjustable acoustic-wave duplexer, a frequency discriminator and a control circuit. The adjustable acoustic-wave duplexer has a first terminal point, a second terminal point and a third terminal point. The adjustable acoustic-wave duplexer includes a TX filter, an RX filter, a first loop switch and a second loop switch. The first loop switch is used for conducting a first loop. The second loop switch is used for conducting a second loop. The control circuit adjusts the operating frequency of the TX filter according to a first loop calibration signal. The control circuit adjusts the operating frequency of the operating frequency of the RX filter according to the second loop calibration signal.

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 radio frequency (RF) receiver, which has an RF filter and impedance matching circuit and an RF low noise amplifier (LNA), is disclosed. The RF filter and impedance matching circuit includes a first passive RF acoustic resonator; provides an RF bandpass filter having an RF receive band based on the first passive RF acoustic resonator; and presents an input impedance at an RF input and an output impedance at an RF output, such that a ratio of the output impedance to the input impedance is greater than 40. The RF LNA is coupled to the RF output.

Embodiments of resonator circuits and modulating resonators and are described generally herein. One or more acoustic wave resonators may be coupled in series or parallel to generate tunable filters. One or more acoustic wave resonances may be modulated by one or more capacitors or tunable capacitors. One or more acoustic wave modules may also be switchable in a filter. Other embodiments may be described and claimed.