Motorola Corporation

Andrew Corporation

Michael David Leffel

Edward Vincent Louis

Mark G Obermann

Timothy Mark Avicola

Grover Charles Burkett, Jr

Douglas Edward Miller

Bradley Warren Holdridge

An amplifier includes an RF power amplifier and a predistortion circuit coupled to the power amplifier. The predistortion circuit affects an input path of an RF input signal to the power amplifier. The predistortion circuit is operable for detecting a level of an input signal and generating a delay in the input path based on the input signal level. This enables predistortion correction of a new distortion term AM/DM, in addition to the well known AM/AM and AM/PM terms. The new AM/DM term represents the distortion that is caused by the delay modulation of the input signal as a function of the envelope power variation within the input signal.

Predistortion system and amplifier for addressing group delay modulation

A predistorter for reducing spurious emissions in an amplified signal including a first path configured to generated memory-less distortion correction and one or more second paths configured to generate memory distortion correction. The paths contain one or more dynamically controllable delay circuits that are configured such that the memory-less and memory distortion correction remains independent irrespective of frequency of use of the predistorter.

Independence between paths that predistort for memory and memory-less distortion in power amplifiers

Frequency-independent and frequency-dependent pre-distortion is implemented using look-up tables to retrieve pre-distortion parameters. To compensate for changes in amplifier operating characteristics over time, fixed pre-distortion tables can be used by appropriately offsetting the index values used to retrieve the pre-distortion parameters. The overall amplifier gain as well as the biases applied to one or more amplifier stages are also preferably controlled. In addition, the frequency-independent and/or frequency-dependent pre-distortion tables can be updated either periodically or as needed, by mapping a measure (e.g., average input signal power) to one or more parameters using equations (e.g., piecewise linear curves), where the parameters are applied to one or more polynomials to update the tables.

Table-based pre-distortion for amplifier systems

A control circuit for a feed forward amplifier provides for pausing control and continuous adjustment of a control signal, provides for the control signal to start at any point, provides for rapid convergence, and that does not perturb the system up or down one step to confirm the convergence of the system. The control circuit receives a sampled version of a feed forward amplifier output signal, generates a non-offset control signal based on the sampled output signal, separately generates an offset voltage by reference to voltages stored in a table or based on the non-offset control signal, and combines the non-offset control signal with the offset voltage to produce a control signal. The feed forward amplifier may then adjust an error signal based on the control signal to produce an adjusted error signal that is capable of reducing distortion in the feed forward amplifier.

Feedforward linear amplifier

The insertion phase or delay of an amplifier can be controlled by comparing signals from the amplifier path with signals from a corresponding reference path without requiring the overall signal delay through the reference path to nominally match the overall signal delay through the amplifier path. Amplifier and reference path signals can be combined to form a combined signal whose power is detected using a narrow-band, frequency-selective power detector. For given phase and delay offsets between the amplifier and reference paths, cancellation (i.e., perfectly destructive interference) will occur at a series of different frequencies. By operating the power detector at one of these cancellation frequencies, a variable phase or delay adjuster in the amplifier path can be controlled to minimize the detected power level in order to achieve a desired level of insertion phase for the amplifier, without having to implement an expensive delay element in the reference path.

Frequency-selective phase/delay control for an amplifier

A transmitter that includes a feed forward amplifier amplifies an input signal to produce an amplified signal that includes a distortion component. The transmitter determines an error signal based on the input signal and the amplified signal and amplifies the error signal to produce an amplified error signal that includes an error signal distortion component. The transmitter combines the amplified error signal with the amplified signal to produce an output signal that includes the error signal distortion component and a portion of the amplified signal distortion component. The transmitter determines a distortion component of an attenuated version of the output signal and an energy of the determined distortion component. Based on the determined energy, the transmitter produces a control signal designed to minimize the energy of the distortion component of the attenuated output signal and thereby minimize distortion in the output signal.

Method and apparatus for reduction of distortion in a transmitter

A transmitter includes a feed forward amplifier that includes main signal path having a radio frequency (RF) power amplifier, a feed forward correction circuit, and a control circuit. An amplification of an input signal by the RF power amplifier produces an amplified signal that includes a distortion component. The feed forward correction circuit produces an error signal, which error signal is used to drive an error amplifier to produce an amplified error signal. In order to minimize a distortion component introduced to the amplified error signal by the error amplifier, the control circuit controls a peak power of the error signal based on a detected energy of an attenuated version of the error signal or based on the distortion component introduced to the amplified error signal by the error amplifier.

Method and apparatus far reduction of distortion in a transmitter

A linear power amplifier having one or more feedforward correction loops automatically reconfigures itself for single loop operation based on a power reduction condition. The power reduction condition may be a function of the input power of the linear power amplifier, a current draw of stages within the linear power amplifier, power consumption levels of feedforward error correction amplifiers, the time of day, or any other suitable condition. The linear power amplifier includes a main amplifier circuit (,) and at least a first feedforward error correction circuit (,). A control circuit (,) removes or reduces power from the power amplifier (,) in the main amplifier circuit (,) and reconfigures the feedforward error correction circuit (,) to serve as a temporary main amplifier circuit. This may be done, for example, at predetermined points where the linear power amplifier does not require the feedforward error correction circuit to obtain a desired level of linearity.

Linear power amplifier with configurable feedforward error correction circuits

A power delivery system (500) including a power splitter (502), a plurality of power amplifier modules (508) responsive to the power splitter (502), a power combiner (504), and a gateway controller (506) is provided. Each of the plurality of power amplifier modules (508) include an input switch (520), a variable attenuator (524), an RF power amplifier (526) responsive to the variable attenuator (524) and the input switch (520), an output switch (530) responsive to the RF power amplifier (526), and an alarm detector (532) for indicating an alarm condition of the RF power amplifier (526). The power combiner (504) is responsive to the plurality of power amplifier modules (508), and the gateway controller (506) is in communication with each of the plurality of power amplifier modules (508). The plurality of power amplifier modules controlled in accordance to whether a sleep criteria has been met. When a said sleep criteria has been met at least one of the plurality of power amplifier modules is placed into sleep mode, and is then returned to active mode if the sleep criteria is exited.

Power delivery system and method of controlling the power delivery

A power delivery system (500) including a power splitter (502), a plurality of power amplifier modules (508) responsive to the power splitter (502), a power combiner (504), and a gateway controller (506) is provided. Each of the plurality of power amplifier modules (508) include an input switch (520), a variable attenuator (524), an RF power amplifier (526) responsive to the variable attenuator (524) and the input switch (520), an output switch (530) responsive to the RF power amplifier (526), and an alarm detector (532) for indicating an alarm condition of the RF power amplifier (526). The power combiner (504) is responsive to the plurality of power amplifier modules (508), and the gateway controller (506) is in communication with each of the plurality of power amplifier modules (508).

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Crystal Lake, IL, United States of America

Michael David Leffel