A noise reduction system for a digital receiver reduces noise in signals received at the digital receiver. The digital receiver includes an input for receiving an analogue signal, analogue signal processing circuitry for processing an analogue signal, and an output for providing the processed signal to a digital signal processor. The noise reduction system is located between the input and the analogue signal processing circuitry, and includes a first component that outputs results of a noise signal identification and a second component that applies one or more counter-measures to the received analogue signal to produce a modified analogue signal. The modified analogue signal has a reduced level of noise compared to the received analogue signal, wherein the noise reduction system is arranged to assess the effectiveness of the one or more counter-measures applied by the second component to determine whether any further counter-measures are required.

A radio frequency receiver is provided that comprises an antenna, an RF amplifier, at least one down conversion mixer stage and a variable notch filter. The at least one down-conversion mixer stage is arranged to act on signals provided by the RF amplifier and is tuned to a tuned frequency ft which is selected from a plurality of possible tuned frequencies corresponding to a frequency of the RF signal to be received at the antenna. The variable notch filter is arranged to act on signals passing from the antenna to the RF amplifier and has a resonance frequency f.sub.r which is selected from a plurality of possible resonance frequencies such that f.sub.r=f.sub.t in where n is a whole number between 2 and 10. The variable notch filter thereby acts to attenuate signals from the antenna at said resonance frequency.

One example includes a receiver system. The receiver system includes an analog-to-digital converter (ADC) configured to convert an analog input signal into a digital output signal at a sampling frequency. The receiver system also includes a spur correction system configured to receive the digital output signal and to estimate spurs associated with the digital output signal and to selectively correct a subset of the spurs associated with a set of frequencies that are based on the sampling frequency.

Systems, methods, and computer program product embodiments are disclosed for removing any fixed frequency interfering signal from an input signal without introducing artifacts that are not part of the original signal of interest. An embodiment operates by using a virtual buffer with a length that matches a length of one cycle of an interfering signal. The embodiment extracts the interfering signal into the virtual buffer. For a sample in the next cycle of the interfering signal that corresponds to a virtual memory location for the virtual buffer, the embodiment can update one or more physical memory locations of the virtual buffer that are in the vicinity of the virtual memory location. This use of virtual buffer can remove any interfering signal without creating the artifacts associated with conventional notch filters.

A reconfigurable image suppressing receiver includes a front-end amplifier, a first multi-mode circuit, a second multi-mode circuit, a wideband combining transformer, and a controller. The front-end amplifier is configured to receive a radio frequency (RF) signal from an antenna and adjust a gain of the RF signal. The first multi-mode circuit is configured to mix a first instance of the RF signal with an in-phase local oscillator signal to generate an in-phase intermediate frequency (IF) signal. The second multi-mode circuit is configured to mix a second instance of the RF signal with a quadrature local oscillator signal to generate a quadrature IF signal. The wideband combining transformer is configured to combine the in-phase IF signal and the quadrature IF signal to generate a combined IF signal. The controller is configured to adjust one or more tunable parameters associated with the combined IF signal.

An active canceller includes a magnitude estimator, a phase estimator, a tone generator, and a suppressor. The magnitude estimator estimates the magnitude of spurious signals on a channel. The phase estimator estimates the phase of the spurious signals on the channel. The tone generator generates a tone signal based on the estimated magnitude and phase. The suppressor subtracts the tone signal from a channel signal to suppress the spurious signals. The magnitude and phase estimators and the suppressor may operate in the time domain.

Architectures and techniques relate to selectively implementing certain components to suppress emissions. For example, an emissions-suppression circuit can include a notch filter associated with a first frequency range, a switch assembly coupled to the notch filter, and a duplexer coupled to the switch assembly. The switch assembly can be configured to, in a filter state, couple the notch filter to a transmit path and configured to, in a bypass state, decouple the notch filter from the transmit path. The transmit path can be associated with two or more switch connections in the notch-filter state and associated with one switch connection in the bypass state. The duplexer can include a transmit filter that is associated with a second frequency range.

Disclosed is a radio frequency (RF) amplifier having channel selectivity. The RF amplifier includes a main path including an amplifier, and a feedforward path including a gain/phase compensator, a high-pass filter, and a mixer.

A filter circuit comprises in a signal line a band filter (BF) allowing to let pass a useful frequency band and a notch filter (NF) circuited in series to the band filter for filtering out a stop band frequency. The notch filter comprises a series circuit of a number of parallel shunt elements (SE1 . . . SE6) wherein each shunt element is shifted infrequency against the other shunt elements that the frequencies thereof are distributed (f1 . . . F6) over a notch band. All shunt elements may be realized as a SAW one-port resonator (TR.sub.NF) including regions with different pitches.

A radio frequency module includes: a switch that includes: a common terminal connected to a first common transmission path; a first selection terminal connected to a first transmission path; and a second selection terminal connected to a second transmission path, and switches between connecting the common terminal to the first selection terminal and to the second selection terminal; a transmission power amplifier disposed on the module board and on first common transmission path; and first circuit components disposed on a reception path. The first transmission path is a path through which a transmission signal of a first communication band is transferred, the second transmission path is a path through which a transmission signal of a second communication band is transferred, the switch is disposed on a first principal surface, and at least one of the first circuit components is disposed on a second principal surface.