A radio-frequency transceiver circuit, comprising: a first port and a second port, configured to receive, together, a pair of differential signals; a radio-frequency matching circuit communicatively coupled to the first port and the second port, and configured to process the pair of differential signals to obtain a radio-frequency signal and configured to increase transmission power for the radio-frequency signal, wherein the radio-frequency matching circuit includes at least one capacitor, at least one distributed inductor; a band pass filter circuit, communicatively coupled to the radio-frequency matching circuit and configured to filter the radio-frequency signal, wherein the band pass filter circuit includes at least one capacitor and at least one distributed inductor; and a third port, communicatively coupled to the band pass filter circuit and configured to output the filtered radio-frequency signal, wherein both of the at least one distributed inductors have a length of microstrip line.

The present disclosure provides a variable filter circuit capable of controlling a band width and a center frequency of a pass band, and also capable of suppressing the total number of pieces of variable reactance. That is, a variable filter circuit includes a serial arm in which a plurality of circuit elements are connected in series with respect to a signal path and a parallel arm in which a plurality of circuit elements are connected in parallel with respect to the signal path, wherein the serial arm and the parallel arm each includes a variable reactance element, a series reactance element that is connected in series to the variable reactance element and resonates therewith, and a parallel reactance element that is connected in parallel to the variable reactance element and resonates therewith.

An apparatus according to one embodiment includes a hardware based controller that is configured to perform operations. The operations include performing anti-aliasing filtering on each of a plurality of signals, each signal having a frequency that is a different fraction of a frequency of a data read clock. An amplitude is measured of each of the signals after the anti-aliasing filtering. Moreover, the operations include determining whether the measured amplitudes of the signals are within a predefined range. Anti-aliasing settings used during the anti-aliasing filtering are stored in response to a determination that the amplitudes of the signals are within the predefined range. The anti-aliasing settings are changed in response to a determination that the amplitudes of the signals are outside the predefined range.

Radio frequency (RF) systems with tunable filters are provided herein. In certain embodiments, an RF system includes a first RF processing circuit configured to process a first frequency band of a first communication standard and a second frequency band of a second communication standard. The first frequency band and the second frequency band are close in frequency and/or partially overlapping in frequency. The first RF processing circuit includes a tunable filter for changing the bandwidth of the first RF processing circuit to enhance the robustness of the first RF processing circuit to blocker or jammer signals of a third frequency band.

A technique for attenuating common mode transient events uses a differential receiver circuit including a band-stop filter having a stopband f.sub.SB around a notch frequency f.sub.n of a received signal. The differential receiver circuit includes a first high-pass filter coupled in series with the band-stop filter. The notch frequency f.sub.n is less than a carrier frequency f.sub.c of a signal received by the differential receiver circuit. The band-stop filter may include a buffer circuit and a notch filter coupled in series with the buffer circuit. The notch filter may have a second stopband around the notch frequency f.sub.n. The differential receiver circuit may have a propagation delay that is independent of a pulse width of common mode transient energy attenuated by the differential receiver circuit.

Embodiments of radio frequency (RF) filtering circuitry are disclosed. In one embodiment, the RF filtering circuitry includes a first port, a second port, a first RF filter path, and a second RF filter path. The first RF filter path is connected between the first port and the second port and includes at least a pair of weakly coupled resonators. The weakly coupled resonators are configured such that a first transfer response between the first port and the second port defines a first passband. The second RF filter path is coupled to the first RF filter path and is configured such that the first transfer response between the first port and the second port defines a stopband adjacent to the first passband without substantially increasing ripple variation of the first passband defined by the first transfer response.

A band pass filter includes filter circuits, first and second intermediate circuits, and a first capacitor. The first intermediate circuit includes an inductor connected between second and third capacitors. The second intermediate circuit includes an inductor connected between third and fourth capacitors. Resonant circuits included in the filter circuit are connected to ground via a common capacitor. Resonant circuits included in the filter circuit are connected to the ground via a common capacitor. The first capacitor is connected between the first and second intermediate circuits.

A digital decimation filtering circuit of an analog to digital conversion circuit includes an n-tap anti-aliasing filter operable to receive a 1-bit analog to digital converter (ADC) output signal at an oversampling rate and filter the 1-bit ADC output signal to remove frequencies higher than a selected cut-off frequency to produce an n-bit filtered signal at a first data output rate. The digital decimation filtering circuit further includes a decimator operable to receive the n-bit filtered signal at the first data output rate, decimate the n-bit filtered signal by a decimation factor to produce a set of output signals, and sum the set of outputs to produce a decimated signal at a second data output rate. The first data output rate is greater than the second data output rate.

A filter device includes a first ladder filter including serial resonators disposed in a terminal-to-terminal path and parallel resonators disposed in connection paths, a first acoustic wave resonator disposed in parallel to the parallel resonator, and a second acoustic wave resonator disposed in parallel to the serial resonator. Resonance points and anti-resonance points of the first and second acoustic wave resonators are both positioned on the lower frequency side or the higher frequency side of a pass band of the first ladder filter, and on the same side of the pass band of the first ladder filter, when viewed from the pass band of the first filter.

A ladder filter includes series-arm resonators each including an IDT electrode and a reflector, and a parallel-arm resonator. In at least one of the series-arm resonators, where a wavelength that is determined by an electrode finger pitch of the IDT electrode is , an electrode finger center-to-center distance between an electrode finger located closest to the reflector among electrode fingers of the IDT electrode and an electrode finger located closest to the IDT electrode among electrode fingers of the reflector is less than about 0.5, and an anti-resonant frequency of the at least one of the series-arm resonators is higher than an anti-resonant frequency of at least another one of the series-arm resonators.