Spectrian Corporation

Other

Lance Todd Mucenieks

Brian L Baskin

John Alan Eisenberg

David L Brubaker

Dieter Werner Statezni

Charles Stuart Robertson, Iii

James A Proctor

James Arthur Proctor, Jr

Huong M Hang

David Kent Bonds

Armando C Cova

Charles S Robertson

Brent L Irvine

Nemy Salvador

RF power amplifier distortion can be accurately measured in the presence of multi-frequency input signals, by using a swept local oscillator to tune RF input and output receivers. The power detected by the input receiver is compared with a threshold associated with the carrier. Whenever the power detected by the input receiver exceeds the threshold&mdash;indicating that the input receiver is tuned on carrier energy&mdash;the signal path through the output receiver is blanked. The sweeping action combined with selective blanking of the output receiver creates an adaptive notch filter, which allows for the direct measurement of low level distortion power in the presence of high power carriers. This distortion power is digitized and can be processed to control pre-distortion correction circuitry or gain/phase adjustment circuitry of a feed-forward error correction loop.

Carrier-blanking mechanism for sweeping detector used to measure and correct RF power amplifier distortion

RF power amplifier distortion can be accurately measured in the presence of multi-carrier input signals, by using a common swept local oscillator to tune RF input and output receivers, whose outputs are monitored for distortion correction purposes. In carrier cancellation and feedforward cancellation mode, when the power detected by the input receiver exceeds a power threshold, the processor accumulates a digital representation of uncancelled carrier energy detected by the output receiver when sampling the signal at the output of the carrier cancellation combiner. It otherwise accumulates uncancelled IMD sampled at the output of the amplifier downstream of the feedforward cancellation coupler. In predistortion mode, the output receiver monitors only the output of the carrier cancellation combiner. When the power detected by the input receiver does not exceed the carrier power threshold, any energy measured by the output receiver corresponds to residual distortion energy from the predistorted main amplifier. This allows predistortion to be adaptively controlled by minimizing accumulated energy detected by the output receiver when it monitors the output of the carrier cancellation combiner during the entire sweep.

Distortion detection apparatus for controlling predistortion, carrier cancellation and feed-forward cancellation in linear RF power amplifiers

Linearity of an RF/microwave power amplifier is enhanced by an amplitude and phase distortion correction mechanism based upon signal envelope feedback, that operates directly on the RF signal passing through the power amplifier. A phase-amplitude controller responds to changes in gain and phase through the RF/microwave power amplifier signal path caused by changes in RF input power, DC power supply voltages, time, temperature and other variables, and controls the operation of a gain and phase adjustment circuit, so as to maintain constant gain and transmission phase through the RF/microwave power amplifier.

Polar envelope correction mechanism for enhancing linearity of RF/microwave power amplifier

An RF power amplifier linearization architecture has a pair of matched RF amplifiers, RF signal paths through which are intercoupled with a phase and amplitude measurement and predistortion mechanism. By selectively combining the RF output of a main path RF power amplifier with the RF input signal supplied to a parallel path RF power amplifier, the predistortion control mechanism of the invention predistorts the RF input signal applied to the parallel path amplifier, so that it includes the same modulated RF carrier component as that applied to the main path amplifier, as well as a complementary version of the intermodulation component of the output of the main path amplifier. The predistortion for each amplifier is controlled such that the resulting RF output signals produced by the matched amplifier pair will have the desired RF carrier modulation component but equal amplitude and phase-reversed intermodulation components. Combining these two matched amplifier outputs in a quadrature hybrid produces a composite signal, in which the desired amplified modulated RF carrier components produced by each matched amplifier constructively sum, while unwanted IMD components cancel.

RF power amplifier linearization using parallel RF power amplifiers

An RF power amplifier linearization architecture contains main and auxiliary path RF amplifiers. A distortion-inverting circuit extracts the distortion component from the output signal of the main amplifier and combines it with a delayed sample of the RF input signal to drive an auxiliary path RF amplifier, via a predistorter. An output quadrature hybrid combines the output of the main and auxiliary path amplifiers. The cascading of the distortion-inverting circuit with the predistorter compensates for the non-linear behavior of the auxiliary path RF power amplifier thereby producing a composite signal at the output quadrature hybrid, in which RF carrier components from each amplifier combine constructively while distortion components cancel.

High efficiency feed-forward RF power amplifier with predistoration

A digitally implemented, look-up table-based, predistortion and feed-forward correction signal processing mechanism compensates for distortion generated in the RF power amplifier. The input signal to the RF amplifier is stored for comparison with the measured the RF output. In each of predistortion and feed-forward signal processing paths, the magnitude of the complex waveform of the input signal is extracted to derive a read-out address to a dual-port RAM which stores weights to be multiplied by the input signal. In the predistortion signal processing path, the product is coupled to the RF power amplifier. In the feed-forward correction loop, the product is amplified by an auxiliary feed-forward RF amplifier and coupled into the amplified output signal path of the RF power amplifier.

Adaptive digital predistortion linearization and feed-forward correction

An RF power amplifier has an RF input port to which an RF input signal is coupled, an RF output port from which an amplified RF output signal is derived. An RF carrier cancellation combiner has a first input coupled to the RF input port and a second input coupled to the RF output port. The carrier cancellation combiner produces an RF error signal representative of RF distortion of a signal flow path through the RF amplifier between the RF input port and the RF output port. To reduce a residual carrier signal in the RF error signal, a wideband autocalibrating correlator correlates a reference signal, representative of the RF input signal, with the RF error signal, producing a control signal, which is coupled to a vector modulator to modify the signal flow path through the RF amplifier. A digital signal processor within the correlator measures DC distortion associated with the multiplier components of the correlator and controllably removes DC distortion from the control signal, so that modification of the signal flow path through the RF amplifier by the vector modulator is controlled with a higher precision, providing maximal carrier cancellation.

Control of RF error extraction using auto-calibrating RF correlator

Polar envelope correction mechanism for enhancing linearity of

A first loop is provided to subtract a properly scaled and delayed sample of the amplifier's input spectrum from a scaled and phase shifted sample of its output spectrum which contains intermodulation distortion. The result of this subtraction (if the samples are maintained at the same amplitude and 180 degrees out of phase) is a signal rich in the intermodulation products of the amplifier. A feature of the invention is a differential phase-amplifier comparator which compares the signals prior to and after amplification and generates control signals for amplitude and phase trimmers for the signal prior to the amplifier and thus maintains the required equal amplitude and 180 degree phase relationship required for carrier cancellation. The signals before amplification and after amplification are subtracted leaving substantially the intermodulation products resulting from amplification. A second loop is provided to reduce intermodulation distortion when a plurality of signals are amplified, resulting in the intermodulation of the signals. The intermodulation products are then fed forward with suitable amplification by an error amplifier and phase shift to cancel the amplifier intermodulation products when added to the amplifier output.

Growing community of inventors

Boulder Creek, CA, United States of America

Lance Todd Mucenieks