Abstract: An apparatus is disclosed, comprising means for determining a noise floor for a radio frequency (RF) system. The apparatus may also comprise means for determining a Passive InterModulation (PIM) value of a component of the RF system contributing as a source of PIM; determining that a passive intermodulation (PIM) cancellation system should be enabled if the PIM value is above a predetermined threshold from the noise floor. The apparatus may also comprise means for determining that the PIM cancellation system should be disabled if the PIM value is at or below the predetermined threshold.

Abstract: As solution for predistorting a signal is presented. The solution comprises receiving (600) as an input a signal comprising at least two signal components on a different band, sampling (602) the input signal comprising linear terms, composite non-linear terms causing intermodulation outside Nyquist band of the input signal and further non-linear terms causing intermodulation inside the Nyquist band, the further non-linear terms comprising multi-band terms. Oversampling (604) by a given factor is applied to the signal in a first predistortion circuit for processing the linear terms and composite non-linear terms causing intermodulation outside Nyquist band; processing (606) the input signal without oversampling in a second predistortion circuit in parallel with the first predistortion circuit for the further non-linear terms. The rates of the output signals of the predistortion circuits are matched (608), combined and filtered (610).

Abstract: A method, apparatus and computer program product is disclosed. The apparatus may comprise means for providing a model for a system for mitigating unwanted effects in a received signal and a means for determining a first curve, acorr, by performing autocorrelation of the model. The apparatus may also comprise means for determining a second curve, Xcorrenv, by performing cross-correlation of the model and a received signal comprising unwanted components due to first and second sources and means for estimating first and second delays associated with respective first and second sources based on the first and second curves, acorr, Xcorrenv. The unwanted effects in the received signal may be PIM products/components, but the disclosure is not limited to PIM alone, and embodiments may be used to mitigate or compute peaks in any interfering scenario where peaks may be hidden.

Abstract: A method comprising determining a plurality of digital pre-distortion engines, determining signals for the pre-distortion engines, determining terms for a matrix and filter the matrix, based on the filtered matrix, determining correlation matrixes, obtaining pre-distorted signals from the digital pre-distortion engines, wherein the pre-distorted signals are pre-distorted based on the determined correlation matrixes, and combining the pre-distorted signals to a combined pre-distorted signal.

Abstract: Various communication devices may benefit from the appropriate use of modeling techniques. For example, devices that include components that may be driven into non-linear ranges of operation may benefit from low complexity non-linear modelling techniques. Such devices may be used, for example, in wireless communication systems. A method can include obtaining a sample of a signal representative of power consumed by a device while the device is operating in a non-linear range while being driven according to a driving signal. The method can also include computing a correction to the driving signal based on the sample. The correction can be calculated based on a plurality of non-overlapped non-linear sections corresponding to a response of the device. The method can further include applying the correction to adjust the driving signal. The correction can be configured to adjust the power to a desired value of power.

Abstract: An apparatus is disclosed, comprising means for determining a noise floor for a radio frequency (RF) system. The apparatus may also comprise means for determining a Passive InterModulation (PIM) value of a component of the RF system contributing as a source of PIM; determining that a passive intermodulation (PIM) cancellation system should be enabled if the PIM value is above a predetermined threshold from the noise floor. The apparatus may also comprise means for determining that the PIM cancellation system should be disabled if the PIM value is at or below the predetermined threshold.

Abstract: This specification relates to digital pre-distortion of signals before power amplification during the transmission of a signal. A method comprising: receiving an input signal 1st and 2nd subband signals associated with 1st and 2nd centre frequencies; applying a pre-distortion to the input signal to generate a pre-distorted signal, the pre-distortion applying an inverse to a power amplification model associated with a power amplifier; and outputting the pre-distorted signal for power amplification. The power amplification model or the inverse to the power amplification model comprises a first plurality of terms and a second plurality of terms. Each of the 1st and 2nd plurality of terms comprising a product of a complex coefficient, a power factor, and other factors depending on if it is 1st or 2nd plurality of terms.

Abstract: An apparatus is disclosed, comprising means for providing two or more amplifiers for amplifying signals in two or more respective frequency bands, receiving a composite signal comprising first and second predistorted input signals in first and second frequency bands and filtering the composite signal to provide (i) the first predistorted signal for input to a first amplifier of the two or more amplifiers for producing an amplified first output signal and (ii) the second predistorted signal for input to a second amplifier of the two or more amplifiers for producing an amplified second output signal. The apparatus may also comprise means for routing, at non-overlapping times, the first and second output signals to a common feedback path and for linearizing received first and second input signals based on the respective first and second output signals received on the common feedback path.

Abstract: A method comprising determining a plurality of digital pre-distortion engines, determining signals for the pre-distortion engines, determining terms for a matrix and filter the matrix, based on the filtered matrix, determining correlation matrixes, obtaining pre-distorted signals from the digital pre-distortion engines, wherein the pre-distorted signals are pre-distorted based on the determined correlation matrixes, and combining the pre-distorted signals to a combined pre-distorted signal.

Abstract: The present invention addresses method, apparatus and computer program product for stabilization of the direct learning algorithm for wideband signals. Thereby, a signal to be amplified is input to a pre-distorter provided for compensating for non-linearity of the power amplifier, and the pre-distorted output signal from the pre-distorter is forwarded to the power amplifier. Parameters of the pre-distorter are adapted based on an error between the linearized signal output from the power amplifier and the signal to be amplified using an adaptive direct learning algorithm, and the linear system of equations formed by the direct learning algorithm are solved using a conjugate gradient algorithm, wherein, once per direct learning algorithm adaptation, at least one of the initial residual and the initial direction of the conjugate gradient algorithm are set based on the result of the previous adaptation.

Abstract: Various communication devices may benefit from the appropriate use of modeling techniques. For example, devices that include components that may be driven into non-linear ranges of operation may benefit from low complexity non-linear modelling techniques. Such devices may be used, for example, in wireless communication systems. A method can include obtaining a sample of a signal representative of power consumed by a device while the device is operating in a non-linear range while being driven according to a driving signal. The method can also include computing a correction to the driving signal based on the sample. The correction can be calculated based on a plurality of non-overlapped non-linear sections corresponding to a response of the device. The method can further include applying the correction to adjust the driving signal. The correction can be configured to adjust the power to a desired value of power.

Abstract: The present invention addresses method, apparatus and computer program product for controlling a Direct Learning Algorithm. Thereby, a power amplifier operating in a non-linear state is controlled. A signal to be amplified is input to a pre-distorter provided for compensating for non-linearity of the power amplifier. The pre-distorted output signal is forwarded from the pre-distorter to the power amplifier. Parameters of the pre-distorter are adapted in plural steps based on an error between a linearized signal output from the power amplifier and the signal to be amplified using an adaptive direct learning algorithm. It is detected whether the error diverges; and adapting of the parameters of the pre-distorter is stopped when it is determined that the error is diverging.

Abstract: The present invention addresses method, apparatus and computer program product for stabilization of the direct learning algorithm for wideband signals. Thereby, a signal to be amplified is input to a pre-distorter provided for compensating for non-linearity of the power amplifier, and the pre-distorted output signal from the pre-distorter is forwarded to the power amplifier. Parameters of the pre-distorter are adapted based on an error between the linearized signal output from the power amplifier and the signal to be amplified using an adaptive direct learning algorithm, and the linear system of equations formed by the direct learning algorithm are solved using a conjugate gradient algorithm, wherein, once per direct learning algorithm adaptation, at least one of the initial residual and the initial direction of the conjugate gradient algorithm are set based on the result of the previous adaptation.

Abstract: The present invention addresses method, apparatus and computer program product for stabilization of the direct learning algorithm for wideband signals. Thereby, a signal to be amplified is input to a pre-distorter provided for compensating for non-linearity of the power amplifier, and the pre-distorted output signal from the pre-distorter is forwarded to the power amplifier. Parameters of the pre-distorter are adapted based on an error between the linearized signal output from the power amplifier and the signal to be amplified using an adaptive direct learning algorithm, and the linear system of equations formed by the direct learning algorithm are solved using a conjugate gradient algorithm, wherein, once per direct learning algorithm adaptation, at least one of the initial residual and the initial direction of the conjugate gradient algorithm are set based on the result of the previous adaptation.

Abstract: The present invention addresses method, apparatus and computer program product for controlling a Direct Learning Algorithm. Thereby, a power amplifier operating in a non-linear state is controlled. A signal to be amplified is input to a pre-distorter provided for compensating for non-linearity of the power amplifier. The pre-distorted output signal is forwarded from the pre-distorter to the power amplifier. Parameters of the pre-distorter are adapted in plural steps based on an error between a linearized signal output from the power amplifier and the signal to be amplified using an adaptive direct learning algorithm. It is detected whether the error diverges; and adapting of the parameters of the pre-distorter is stopped when it is determined that the error is diverging.

Abstract: The present invention addresses method, apparatus and computer program product for stabilization of the direct learning algorithm for wideband signals. Thereby, a signal to be amplified is input to a pre-distorter provided for compensating for non-linearity of the power amplifier, and the pre-distorted output signal from the pre-distorter is forwarded to the power amplifier. Parameters of the pre-distorter are adapted based on an error between the linearized signal output from the power amplifier and the signal to be amplified using an adaptive direct learning algorithm, and the linear system of equations formed by the direct learning algorithm are solved using a conjugate gradient algorithm, wherein, once per direct learning algorithm adaptation, at least one of the initial residual and the initial direction of the conjugate gradient algorithm are set based on the result of the previous adaptation.

Abstract: Enhancing the intermodulation performance of an RF power amplifier by determining a coarse time delay represented by an integer TI; determining a reference point for a transmitted signal waveform of the RF power amplifier; shifting the waveform by a set of offsets including a plurality of non-integer fractional steps; correlating the transmitted signal waveform with a feedback signal waveform to obtain a respective correlation value for each of corresponding fractional steps; obtaining an accurate fractional delay value by selecting a fractional step having a highest respective correlation value; applying the obtained correct fractional delay value to the transmitted signal waveform to provide a compensated transmitted signal waveform and combining the compensated transmitted signal waveform with the feedback signal waveform to reduce at least one intermodulation product of the RF power amplifier.

Abstract: Enhancing the intermodulation performance of an RF power amplifier by determining a coarse time delay represented by an integer TI; determining a reference point for a transmitted signal waveform of the RF power amplifier; shifting the waveform by a set of offsets including a plurality of non-integer fractional steps; correlating the transmitted signal waveform with a feedback signal waveform to obtain a respective correlation value for each of corresponding fractional steps; obtaining an accurate fractional delay value by selecting a fractional step having a highest respective correlation value; applying the obtained correct fractional delay value to the transmitted signal waveform to provide a compensated transmitted signal waveform and combining the compensated transmitted signal waveform with the feedback signal waveform to reduce at least one intermodulation product of the RF power amplifier.

Abstract: At a current time, a current intermodulation content of a predistortion system is determined. An intermodulation ratio is determined using the current intermodulation content and a previous intermodulation content for the predistortion system. The previous intermodulation content is determined at a time previous to the current time. The determined intermodulation ratio is compared with stored intermodulation ratios. A warning is communicated in response to the comparing indicating the predistortion system is unhealthy. Apparatus and computer program products are also disclosed.

Abstract: A method for correcting high order IM products is described. The method includes creating a modified input signal by increasing one or more portions of an input signal (such as the whole time domain signal for example). The input signal consists of a desired signal and other non-linear products. Each of the one or more portions includes high order IM products. A pre-distorted signal is created by pre-distorting the modified input signal in accordance with a finite signal plan. An output signal is generated by amplifying the pre-distorted signal. Apparatus and computer-readable media are also described.