355 results about "Signal cancellation" patented technology

The present invention is directed to the selective provision of interference canceled signal streams to demodulating fingers in a communication receiver. According to the present invention, potential interferer signal paths are identified. Signal streams having one or more potential interferer signals removed or canceled are created, and a correlation is performed to determine whether the strength of a desired signal path increased as a result. If the correlation indicates that the strength of a desired signal path was increased by the signal cancellation, the interference canceled signal stream is provided to the demodulation finger assigned to track the desired signal path. If the correlation determines that the strength of the desired signal path did not increase as a result of performing interference cancellation, the raw or a different interference canceled signal stream is provided to the demodulation finger.

A circuit that cancels a self-interference signal includes, in part, a pair of signal paths that are substantially in phase, each of which paths includes a passive coupler, a delay element and a variable attenuator. The circuit further includes, in part, a first group of P signal paths each of which is substantially in phase with the pair of paths, and a second group of M signal paths each of which is substantially out-of-phase relative to the pair of signal paths. Each of the P and M signal paths includes a delay element and a variable attenuator. Furthermore, (P−1) signal paths of the first group of P signal paths, and (M−1) signal paths of the second group of M signal paths include a passive coupler. Optionally, each of the M signal paths is optionally 180° out-of-phase relative to the pair of signal paths.

An active terminating device (30) for an electrical transmission line with optional line-receiving and line-driving capabilities. The basic device is a two-terminal unit, denoted as a Signal Canceling Unit (SCU), which sensesthe signal available at its terminals (34a, 34b), and applies negative feedback in order to cancel and absorb the signal. When applied to the end of a transmission line (15a, 15b) as part of wired communication network, the SCU functions as a terminator. When connected in the middle of such wired transmission line, the SCU splits the transmission line into two separate and isolated segments. In such a configuration, the SCU can be used to isolate a portion of a network from signal degradation due to noise or bridge-tap. Furthermore, the two isolated segments may each employ independent communications, such that no interference exists between the segments. In another embodiment, line receiver functionality is integrated into the SCU, designated as a Signal Canceling and Receiving Unit (SCRU) (90). The SCRU can perform all the SCU functions, and also serves as a line receiver in the communication network. In yet another embodiment, line driver functionality is integrated into the SCRU, designated as a Signal Canceling, Receiving and Transmitting Unit (SCRTU) (120). The SCRTU can perform all the SCRU functions, and also serves as a line driver in the communication network. Upon connecting multiple SCRTU's to a continuous transmission line, terminated independent point-to-point communication segments are formed.

A circuit that cancels a self-interference signal includes, in part, a pair of signal paths that are substantially in phase, each of which paths includes a passive coupler, a delay element and a variable attenuator. The circuit further includes, in part, a first group of P signal paths each of which is substantially in phase with the pair of paths, a second group of M signal paths each of which is substantially out-of-phase relative to the pair of signal paths, and at least a pair of feedback paths. Each of the P and M signal paths, as well as the feedback paths includes a delay element and a variable attenuator. Optionally, each of the M signal paths is optionally 180° out-of-phase relative to the pair of signal paths.

An apparatus and method for interference cancellation and synchronization maintenance over interference channel estimation in a communication system are provided. An interference channel estimator fixes synchronization and estimates an interference signal. An interference signal controller eliminates the estimated interference signal from a received RF signal. A synchronization unit unfixes fixed synchronization and tracks synchronization when the interference signal cancellation is stable. A data buffer stores data from which the interference signal is canceled.

A transmitter/receiver combination system and a transmission signal canceling method for use in a wireless communication system using a single common antenna are provided. The system includes a circulator for receiving an original transmission signal from the transmitter, transmitting the received transmission signal to an antenna without a signal loss, and transmitting a reception signal received from the antenna to other ends without a signal loss, and a transmission signal canceller for dividing the transmission signal input in an attenuated form as much as a predetermined magnitude via the circulator together with the reception signal into two paths, producing two is phase inverted transmission signals with the same magnitude and delay time as those of the original transmission signal, and recombining the produced two transmission signals with each other, to thereby canceling the transmission signal and transmitting only the reception signal to the receiver.

A self-interference signal cancellation circuit includes a transmitter for transmitting a transmit signal, a plurality of signal paths, a controller, and a receiver for receiving a signal. Each signal path includes a delay element and a variable attenuator having attenuation levels set by the controller. A combiner generates an output signal by combining outputs of the signal paths. The circuit computes a matrix based on first and second output signals associated with first and second attenuation levels. The controller concurrently varies the attenuation level of each signal path so that a product of the matrix and the attenuation levels of the signal paths is substantially equal to the received signal. The circuit may iteratively compute the matrix using different transmit signal frequencies or with an FFT. The controller iteratively varies the attenuation level of the attenuators until a sum of the product and the received signal satisfies a predefined condition.

An apparatus comprises a transmitter, a receiver, an antenna and a signal cancellation circuit. The transmitter is configured to send a transmitter signal associated with a frequency. The receiver is associated with the frequency. The antenna is coupled to the transmitter and the receiver. The signal cancellation circuit is coupled to the transmitter, the receiver and the antenna. The signal cancellation circuit is configured to phase shift a first portion of the transmitter signal to produce a phase-shifted signal. The signal cancellation circuit is configured to combine the phase-shifted signal with a second portion of the transmitter signal to produce a combined signal. The second portion of the transmitter signal is associated with a reflection of a third portion of the transmitter signal from the antenna. The first portion, the second portion and the third portion of the transmitter signal are different from each other.

A method for communication includes receiving a Radio Frequency (RF) channel containing a desired signal conforming to a first air interface and an interfering signal conforming to a second air interface. A first receiver configured for the first air interface and a second receiver configured for the second air interface are synchronized to a common frequency and timing reference. While the first and second receivers are synchronized, the desired signal is decoded from the RF channel using the first receiver to generate a first output, the interfering signal is decoded from the RF channel using the second receiver to generate a second output, and the desired signal is reconstructed while suppressing the interfering signal by jointly processing the first and second outputs.

An RF mixer includes a plurality of submixers coupled to a single input transistor pair and a single tail current source. An input LO signal is divided into multiple individual waveforms, each having a different phase. The phase differences are even in that the phase difference between any two time-adjacent individual waveforms is approximately equal to the phase difference between any other two time-adjacent individual waveforms. The submixers are appropriately scaled so that the individual waveforms, when summed, create a piecewise linear LO signal. The submixers also combine the individual waveforms with an input baseband signal to produce an output signal or to produce a baseband signal from an input mixed signal. In order to reduce noise in the system, only one submixer is active at any time. Further, polarities of some individual waveforms are reversed so that to avoid signal cancellation when by combining waveforms of opposite polarities.

An interference signal cancellation device comprises a signal splitter, a delay element and a signal combiner. The signal splitter distributes a disturbed signal to a first signal path and a second signal path. The delay element is situated in at least one of the first signal path and the second signal path for introducing a relative delay between a first signal in the first signal path and a second signal in the second signal path. The signal combiner combines the first signal and the second signal. An interference signal within the disturbed signal is substantially reduced within the signal combiner. A method for interference signal cancellation is also proposed. Furthermore, a computer program product with instructions for the manufacture and a computer program product enabling a processor to carry out the method for interference signal cancellation are also proposed.

A method, system and apparatus for generating a cancellation signal in a RFID reader to isolate a transmit section and a receive section of a RFID reader, where the RFID reader generates a local reference signal from a broadcast transmit signal, receives a receive signal from a remote device, determines at least one correction factor, e.g., an amplitude correction factor, to generate a cancellation signal. The method, system and apparatus can further include combining a cancellation signal and a receive signal to minimize or cancel out interference and noise on the receive signal.

A quadrature modulator divides a part of a transmitted signal to generate a cancel signal. A signal comparator compares the amplitude and phase of the cancel signal which is generated by the quadrature modulator with those of a received signal, and outputs signals corresponding to the comparison results to the quadrature modulator. The quadrature modulator generates the cancel signal on the basis of the output signals of the signal comparator, and these components perform feedback control such that the cancel signal has the same amplitude as the leakage signal and is in phase with the leakage signal. A combiner combines the cancel signal with an antiphase cancel signal, which is made to be in opposite phase with the cancel signal outputted from the quadrature modulator, to cancel out the leakage signal.

The invention belongs to the field of signal processing. The invention provides an improved Capon beamforming algorithm for the problem that the performance of a conventional Capon beamforming algorithm is significantly degraded, wherein the problem is caused by estimation errors of an array steering vector or inaccurate estimation of a data covariance matrix. On the basis that a reception data covariance matrix is reconstructed based on linear contraction estimation, a mismatch steering vector is projected to an updated subspace by updating the signal and interfering subspace, so as to acquire the optimal reception right. The algorithm maintains a high gain in the true wave incoming direction and assumed wave incoming direction of a desired signal, which avoids signal cancellation. Compared with other algorithms, the algorithm can more accurately point to the true direction of the desired signal. The algorithm is robust for steering vector mismatch caused by the observation error of the signal arrival direction.

The present invention is directed to signal cancellation in spread spectrum communication systems. In particular, the present invention provides method and apparatus for selectively canceling interfering signals, even where symbols to be canceled do not align with symbols associated with a desired signal path. Furthermore, the interference cancellation provided by embodiments of the present invention is capable of functioning to remove interference associated with channels utilizing a symbol length that is different than the symbol length of a desired signal path. In accordance with a further embodiment of the present invention, method and apparatus for efficiently calculating projections to enable signal cancellation are provided.

An interference cancellation device comprises an input for a disturbed signal, a first frequency shifter, a bandpass filter, and a signal combiner. The first frequency shifter shifts the disturbed signal from an original frequency range to a filtering frequency range. The frequency-shifted signal is filtered by the bandpass filter. The filtered signal is supplied to the signal combiner which combines the filtered signal with the disturbed signal to substantially reduce the interference signal that is present in the disturbed signal. A method for interference signal cancellation is also proposed. Furthermore, a computer program product with instructions for the manufacture and a computer program product enabling a processor to carry out the method for interference signal cancellation are also proposed.

The invention discloses a leakage signal cancellation circuit of a linear frequency modulation continuous wave radar. A transmission signal is transmitted by an antenna via a circulator; an input end of a first coupler is connected with the transmission signal; a through end of the first coupler is connected to the circulator; a coupled end of the first coupler is connected to an input end of a second coupler; a through end of the second coupler is connected to a signal input end of a vector modulator; a coupled end of the second coupler is connected to a phase shifter; the phase shifter is connected to an LO (Local Oscillator) signal input end of a quadrature mixer; leakage signal in the circulator is input to a third coupler; a through end of the third coupler is connected to a fourth coupler; a coupled end of the third coupler is connected with an output end of the vector modulator; a through end of the fourth coupler is connected to a receiver; a coupled end of the fourth coupler is connected to an RF (Radio Frequency) signal input end of the quadrature mixer; two differential signals output by the quadrature mixer are connected to the vector modulator via a differential operational amplifier, an active low pass filter and a summing circuit respectively; and the summing circuit and offset voltage carry out additive operation.

The present invention relates to the field of self-adaption beam forming during array signal processing, in particular, relates to a method for forming a steady beam based on an interfering noise covariance matrix estimation. The present invention includes using an antenna array to receive a distant field narrowband incident signal, using a limited snapshot number to estimate the covariance matrix for receiving data, then performing characteristic decomposition on the covariance matrix for receiving data, wherein prior information of the number of an incident signal source can be obtained via a method of estimating the number of the signal source; optimally obtaining a more accurate desired signal steering vector at a projection of a noise subspace according to an estimated desired signal steering vector, and performing estimation obtaining of the interfering noise covariance matrix according to interference signal steering vector prior information and an estimated noise power so as to perform beam forming. The present invention first performs the interfering noise covariance matrix estimation to get rid of the component of the desired signal in the training data, which can avoid the generation of signal cancellation.

A CDMA coded, spread spectrum radio signal containing a strong signal and a weak signal is received, and the interference of the strong signal with the weak signal is computed to enhance the ability to track the weak signal. The codes modulating both signals are known, and the weak signal can be predicted. The interference of the strong signal is calculated as the product of the amplitude of the strong signal and the predicted crosscorrelation of the strong signal with the weak signal. The strong signal may be measured, predicted, or acquired through a combination of both methods. The crosscorrelation may be predicted for a range of weak signal values, and the weak signal selected as the prediction producing the greatest received power.