1018 results about "Pre distortion" patented technology

A system is provided for substantially reducing variation in AM to PM distortion of a power amplifier caused by variations in RF drive power and temperature. The system includes power control circuitry and power amplifier circuitry. The power amplifier circuitry includes an input amplifier stage and at least one additional amplifier stage coupled in series with the input amplifier stage. The power control circuitry provides a first supply voltage to the input amplifier stage based on a control signal such that the first supply voltage has a predetermined DC offset with respect to the control signal. The first supply voltage is provided such that the predetermined DC offset substantially reduces variations in the AM to PM distortion of the power amplifier due to variations in radio frequency (RF) drive power.

The technique of amplifier sharing is implemented in a system designed to accommodate transmit diversity. In one embodiment of the invention, the amplifiers are shared 1) to amplify a first and a second diversity-encoded signal, each of which represents the information a first signal that is to be transmitted using transmit diversity, and 2) to amplify a second signal to be transmitted without using transmit diversity. The first and second diversity-encoded signals are used to form a first and a second composite signal. Each composite signal is amplified in a different one of two power amplifiers. Each amplified composite signal is then used to form an amplified first diversity-encoded signal and an amplified second diversity-encoded signal. The first and second composite signals can also be formed using the second signal. Each composite signal is then amplified in a different one of the two power amplifiers and the two amplified composite signals are used to form an amplified second signal. In another embodiment of the invention, the first and second composite signals can be formed in the digital domain. Each composite signal is digitally pre-distorted and then modulated onto a transmission frequency signal, such as an RF signal. Each pre-distorted composite signal is then amplified in the respective amplifier.

Near-to-eye displays within head mounted devices offer both users with and without visual impairments enhanced visual experiences either by improving or augmenting their visual perception. Unless the user directly views the display without intermediate optical elements then the designer must consider chromatic as well as other aberrations. Within the prior art the optical train is either complex through additional corrective elements adding to weight, cost, and size or through image processing. However, real time applications with mobile users require low latency to avoid physical side effects. Accordingly, it would be beneficial to provide near-to-eye displays mitigating these distortions and chromatic aberrations through pre-distortion based electronic processing techniques in conjunction with design optimization of the optical train with low weight, low volume, low complexity, and low cost. Further, it would be beneficial to exploit consumer grade low cost graphics processing units rather than application specific circuits.

A method of optimizing performance of a multiple path amplifier includes: splitting an input signal to derive a respective sub-signal for each branch of the multiple path amplifier; independently pre-distorting each sub-signal using a known performance characteristic of its associated branch of the multiple path amplifier; and supplying each pre-distorted sub-signal to its associated branch of the multiple amplifier.

A Dynamic Digital Pre-Distortion (DDPD) system is disclosed to rapidly correct power amplifier (PA) non-linearity and memory effects. To perform pre-distortion, a DDPD engine predistorts an input signal in order to cancel PA nonlinearities as the signal is amplified by the PA. The DDPD engine is implemented as a composite of one linear filter and N-1 high order term linear filters. The bank of linear filters have programmable complex coefficients. To compute the coefficients, samples from the transmit path and a feedback path are captured, and covariance matrices A and B are computed using optimized hardware. After the covariance matrices are computed, Gaussian elimination processing may be employed to compute the coefficients. Mathematical and hardware optimizations may be employed to simplify and reduce the number of multiplication operands and other operations, which can enable the DDPD system to fit within a single chip.

An input signal having amplitude information is pre-distorted and converted into two pre-distorted signals without amplitude information. The two pre-distorted signals are separately amplified and then recombined to generate a linearized amplified output signal having amplitude information. The pre-distortion and conversion may be implemented using a pre-distorter and a LINC modulator. Alternatively, the pre-distortion and conversion may be implemented in circuitry that combines the functions of a pre-distorter and a LINC modulator. The amplified, pre-distorted signals are preferably combined using circuitry that provides at least some impedance matching, such as a transformer or a transmission line tee with transmission line stubs.

An active antenna array comprises a plurality of transmission paths, a predistortion modulation signal generator, and a predistortion modulation signal distribution structure. At least two of the plurality of transmission paths comprise a predistortion modulator for modulating a transmission path signal with a predistortion modulation signal generated by the predistortion modulation signal generator and distributed by predistortion modulation signal distribution structure to the at least two of the plurality of transmission paths. A method for predistorting at least two of a plurality of transmission path signals in an active antenna array and computer program products for manufacture and method execution are also claimed.

An adaptive Digital Pre-distortion System and a method for correcting especially power amplifier memory effects. In particular, the invention relates to an electronic circuit, for amplifying an input signal, comprising: a clipping unit for generating a signal, having a reduced peak-to-average power ratio by clipping the input signal; a pre-distorter for generating a pre-distorted signal, defined by an pre-distortion algorithm which is based on the amplifier model function; a representation unit for representing the amplifier model function; a non-linear processing unit, in particular a power amplifier, for generating a processed signal, in particular by amplifying said received pre-distorted signal; a time delay unit for compensating the processing time for the pre-distorted signal generating the delayed pre-distorted signal; and a time delay cascade for delaying the said delayed pre-distorted signal, at the integer sample clocks generating the signals.

There is disclosed a method of controlling an envelope tracking amplification stage comprising an envelope modulated power supply, the method comprising: determining a shaping function to be applied to an envelope signal for controlling the envelope modulated power supply in dependence on a system linearity objective in a region of operation of the amplifier in which the output power of the amplifier is dependent upon the supply voltage; and determining a pre-distortion function to be applied to an input signal to be amplified in dependence on a further linearity objective of the system, in a region of operation of the amplifier in which the output of the amplifier is dependent upon the input power to the amplifier.

An amplitude- and frequency- or phase-modulated radio frequency signal generator that is used for radio emission, generates a phase or frequency control signal and an amplitude control signal from a phase or frequency modulation signal and from an amplitude modulation signal respectively. The generator comprises a phase or frequency modulator and a variable-gain radio frequency power amplifier. The amplitude of the output signal is automatically controlled. In addition, adaptive pre-distortion is carried out in order to pre-distort the phase or frequency control signal in accordance with the amplitude modulation signal during a permanent operating phase. During a learning phase, a pre-distortion module is adapted from the amplitude modulation signal and from the amplitude control signal.

The invention discloses a self-adaptive predistortion method, which comprises the steps: collecting emission data and feedback data, calculating loop delay according to the emission data and the feedback data, carrying out time unifying to input signals according to the loop delay, compensating collected delay of the emission data and the feedback data according to the loop delay, estimating a predistortion model parameter, constructing a matrix according to the set predistortion model parameter, calculating a predistortion parameter corresponding to a power amplifier, adopting a curve fitting method to sample and quantize the predistortion parameter to obtain an LUT table, modifying the predistortion parameter in a digital predistorter according to the LUT table, carrying out digital predistortion to the input signals according to an LUT address and the predistortion parameter which is modified, and generating the LUT address according to the amplitude of the input signals. The technical scheme of the invention saves the hardware implementation cost and can be realized in an FPGA (programmable gate array) easily.

The present invention provides an amplifier for a wireless transmitter. In one embodiment, the amplifier includes a signal separator for decomposing an input signal into constant envelope signals and amplifier circuits for amplifying the constant envelope signals. The amplifier also includes a combiner for combining the amplified constant envelope signals to form an output signal that is an amplified representation of the input signal. Linear correction circuits are used to apply gain, phase, and/or delay correction to the constant envelope signals. The corrections are determined based upon a feedback portion of the output signal. Pre-distortion circuits are used to apply a non-linear pre-distortion to the constant envelope signals. The non-linear pre-distortion is determined based upon the feedback portion of the output signal.

Methods and systems for calculating pre-distortion coefficients in a closed-loop communication system are presented. Transmission terminals that include high power amplifiers are difficult to operate at or near the saturation point without transmitting signals with nonlinear distortions. By pre-distorting the signal prior to amplification the transmitted nonlinear distortions may be decreased. A closed-looped pre-distortion system may include a receiver that calculates the pre-distortion coefficients and transmits these coefficients back to the transmitter. These coefficients may be stored in a pre-distortion coefficient lookup table and may be updated by the receiver terminal.

A radio frequency modulator based on direct frequency/phase modulation of output signal of a controllable oscillator (724) that is a part of a phase locked loop (PLL) provides a direct modulator that is able to operate over a wide frequency range with a flat frequency response. A modulation signal is digitally processed (721, 730) before injection to a high-pass path of a direct modulator. Applicability of digital signal processing is based on the fact that the modulation signal is a base band signal. Therefore, the modulation signal (702) occupies such a band in the frequency domain so that a sufficient ratio of a sampling rate to an upper edge frequency of the modulation signal can be achieved. Digital processing is used for compensating an effect of non-flat high-pass PLL transfer function and/or to perform pre-distortion of the input signal of a controlled oscillator to compensate an effect of non-linearity of a controlled oscillator.

A circuit for reducing adjacent-channel interference by pre-linearizing and pre-distorting an input signal to be transmitted via a power amplifier having a non-linear transmission characteristic is disclosed. A portion of the input signal exceeding a dynamic range of the power amplifier is determined and expanded along the time axis to produce an expanded version thereof. The expanded version and the input signal are combined, such that the expanded version is subtracted from the input signal, to produce a pre-linearized signal. The circuit further has a pre-distorting unit for pre-distorting the pre-linearized signal using complex pre-distortion coefficients, such that the distortion introduced by the non-linear transmission characteristic of the power amplifier is substantially compensated for according to magnitude and phase.

A radio frequency amplifier system is disclosed in which the amplifier bias supply and power supply voltages are >instantaneously modulated with signals derived from the envelope voltage of the input signal. Separate non-linear mapping functions are used to derive the supply and bias voltages. The two mapping functions are optimised jointly to achieve particular system performance goals, such as optimum efficiency, constant gain, constant phase, or minimum spectral spreading. An optimisation of >particular interest is that which achieves best RF amplifier power added efficiency subject to achieving constant amplifier gain. In this way the need for pre-distortion linearization may be reduced or eliminated.

A data receiver is provided which is operable to receive a signal controllably pre-distorted and transmitted by a transmitter, to generate information for adjusting the pre-distortion applied to the signal transmitted by the transmitter, and to transmit the information to the transmitter. The receiver is further operable to perform adaptive equalization to receive the signal transmitted by the transmitter.

The microwave transmitter of the present invention can perform two-terminal dynamic modulation with respect to the voltage supply terminal and the RF input terminal of a RF power amplifier. The microwave transmitter of the present invention comprises a first modulator and a second modulator. The first modulator uses the baseband digital delta-sigma modulation technique to process the envelope signal and outputs this signal to the voltage supply terminal of the RF power amplifier as a supply voltage. The second modulator uses the baseband digital pre-distortion technique to process the IQ-modulated carrier and outputs this signal to the RF input terminal of the RF power amplifier as a RF input signal. Thereby, the RF power amplifier can highly efficiently reconstruct the power-amplified RF modulated carrier without distortion at the RF output terminal. In addition, the baseband digital processing techniques used in the two modulators make the microwave transmitter of the present invention suitable for multi-mode operation.

In an amplifier system that linearizes an amplifier by pre-distorting the input signal prior to amplification, a baseband pre-distortion processor processes the input signal in a digital baseband domain to generate one or more pre-distortion parameters based on the power of the digital baseband input signal. The digital baseband signal is up-converted and D/A-converted into a non-baseband (e.g., IF or RF) signal which is then pre-distorted, e.g., using a phase/gain adjuster or a vector modulator. By generating the pre-distortion parameters at baseband, while pre-distorting the input signal at non-baseband, the amplifier system avoids the cost and inaccuracies associated with analog signal delay and RF power detection of prior-art “all-RF” pre-distortion implementations, while avoiding the wider-bandwidth filtering of prior-art “all-baseband” pre-distortion implementations.

Embodiments of the present invention include amplitude-modulated or polar-modulated radio frequency (RF) power amplifier circuitry, in which an envelope power supply input to an RF power amplifier is powered by a pre-distorted amplitude modulation (AM) power supply. The pre-distorted AM power supply receives an AM signal, which is then pre-distorted and amplified to provide an AM power supply signal to the RF power amplifier. The pre-distortion of the AM signal is used to improve the linearity, the efficiency, or both, of the RF power amplifier. The pre-distortion provides a feed-forward system, which may allow use of a reduced bandwidth pre-distorted AM signal to an AM power supply and a reduced bandwidth AM power supply, which may increase efficiency.

The invention discloses a method for measuring and correcting distortion of a virtual reality displayer. The method includes the following steps that reticle imaging is carried out through an optical system to obtain a distortion grid image; a distortion coefficient of each grid is obtained through calculation according to the corresponding relationship between a vertex coordinate of the corresponding grid and a vertex coordinate of each distortion grid; non-distortion grids A are marked out on the distortion grid image, according to an optical path reversible principle, an object face of the optical system has distortion grids A' corresponding to the grids A, then vertex coordinates of the distortion grids A' are calculated by means of the distortion coefficients and the vertex coordinates of the grids A, and a coordinate look-up table is generated by means of the vertex coordinates of the distortion grids A'; an image to be projected is converted into a pre-distortion image by means of the coordinate look-up table, an image source is input, a pre-distortion image displayed by the image source is imaged, an imaging image is obtained, the imaging image is compared with the pre-distortion image, the image source is adjusted, and correcting of the image source is completed. The invention further discloses a device for measuring and correcting distortion of the virtual reality displayer.

A method and system enhances the gain of a propagation path of a radio frequency (RF) signal while utilizing an envelope tracking (ET) mechanism to provide power to a power amplifier within the propagation path. An envelope tracking (ET) controller detects using the ET mechanism an RF envelope of the RF signal being propagated towards the power amplifier. The ET controller applies envelope pre-distortion to the RF signal. The ET controller initiates a function for shaping the supply voltage of the power amplifier by selecting a shaping table that can provide a specific level of increasing amplifier gain at higher signal drive level. The ET controller shapes the supply voltage for the power amplifier by adjusting values corresponding to the detected RF envelope. As a result, RF signals are propagated from the transceiver to the power amplifier output port across high and low transceiver drive levels with net constant gain.