Nortel Networks Corporation

Other

Sige Semiconductor, Inc.

Sige Semiconductor (Europe) Limited

Howard James Smith

Scott T Widdowson

John Duncan McNicol

John Jackson Nisbet

Gordon Glen Rabjohn

Johan M Grundlingh

Graham Dolman

Stefan Fulga

David Neal Wessel

Andrew John Booth

Paul Wallis

David Lewsey

A method of reducing distortion in the output of an amplifier is provided. The method comprises subtractively combining baseband error signals with the appropriate phase shift with baseband input signals, the baseband error signals generated by subtractively combining delayed fed-forward portions of the baseband input signals with baseband converted portions of a fed-back amplified output signal, the amplified output signal being a distorted replica of combined up-converted baseband input signals. The baseband error signals being filtered prior to the combining function, and also providing inputs to a controller which adjusts active elements of the amplification and fed-back paths in order to minimize the distortion within the output of the amplifier.

Method and apparatus for a cartesian error feedback circuit to correct distortion within a power amplifier

A predistortion power amplifier architecture has a power amplifier which receives an input via an amplitude modulator and a phase modulator. A sample of the output of the amplifier and a sample of the input to the amplifier are applied to an adaptive pre-distorter subsystem. The adaptive pre-distorter generates a gain correction signal which is applied to the amplitude modulator and a phase correction signal which is applied to the phase modulator. This serves to predistort the input signal to the power amplifier to compensate for non-linearities in the power amplifier. A switching arrangement alternately couples a sample of the input and output of the amplifier to a first and a second envelope detector. The outputs of the envelope detectors are applied to a difference amplifier. The switching arrangement has a chopping action on the signals which helps to offset imbalances in the characteristics of the two envelope detectors.

Amplitude and phase comparator for microwave power amplifier

A mounting assembly for facilitating the mounting components of a modular system involving a plurality of separate components that are required operationally to interrelate relative to each other when in use so that the relative setting of such components in vertical, horizontal and/or annular orientations with respect to the datum direction is facilitated. A main unit is adapted for mounting to a column support, the main unit being adapted for mounting said components by way of a connection arrangement enabling relative displacement and relative angular setting of the components relative to the base unit.

Multi-component assembly mounting system

A method and apparatus for limiting the effect of interfering transmission on a Global Positioning System (GPS) receiver is disclosed. A first mode of operation of the GPS receiver is provided wherein the AGC of the receiver is operated in a linear state. A second mode of operation of the GPS receiver is provided wherein the AGC of the receiver is operated in a non-linear state. A first signal is provided indicating a presence of a jamming signal. In response to the first signal the GPS receiver is switched from the first mode of operation to the second mode of operation.

GPS receiver with improved immunity to collocated transmissions and method therefor

Movie camera support sled

An amplifier arrangement comprising an amplifier for amplifying an input radio frequency (RF) signal to generate an output RF signal. A linear function processor generates a linear function correction signal which is a linear function of previous samples of the input signal in order to compensate for distortion effects of the amplifier related to the history of the input signal. A non-linear function processor generates a non-linear function of the input signal in order to compensate for instantaneous distortion effects of the amplifier. Then a pre-distortion processor distorts the current input signal in accordance with the linear and nonlinear function correction signals in order to compensate for both types of distortion in the output signal.

Linear amplifier arrangement

This invention relates to high power linear amplifiers. A high power linear amplifier is disclosed for communications such as CDMA communication systems. In accordance with the invention, there is provided a power amplifier comprising a power amplifier, a feedback circuit and a control element; wherein the architecture proposed uses an envelope detector to generate a baseband signal representing the amplitude envelope of the system input RF signal. This is digitised and used to generate phase and gain correction signals. The correction signals modulate the input signal to create a pre-distorted signal: which is applied to the power amplifier for amplification. The pre-distortion is such as to cancel the AM-AM and AM-PM distortion of the power amplifier thus resulting in an amplified output of improved spectral purity. In order to achieve the very high levels of spectral purity required by 3G cellular and multi-carrier 2G cellular systems, the correction coefficients in the lookup table need to be very precisely set. The method proposed incorporates an adaptation system whereby the pre-distorter can 'learn' the contents of the lookup table as it operates.

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Bishops Stortford, United Kingdom

Howard James Smith