Nortel Networks Corporation

Apple Inc.

Martin O'Flaherty

Graham Dolman

Scott Widdowson

Gregory John Bowles

John Ilowski

David M Tholl

Paul Murray Row

Charles E Norman

Andrew John Booth

Roman Nemish

Gordon B Neilson

Colin McGregor

Gordon Neilson

David Tholl

Amplifier units and methods of use are described herein. A amplifier unit includes a first amplifier and a second amplifier connected in parallel, the first amplifier and the second amplifier comprising semiconductor devices that are not the same amplifier design. The present application also discloses a signal input line connected to the first amplifier and the second amplifier. A signal output line is also disclosed which is connected to the first amplifier and the second amplifier.

Enhanced doherty amplifier with asymmetrical semiconductors

A transmit chain comprises a transmit path with a quadrature up-converter which up-converts quadrature signal components to RF. An observation path samples a portion of the RF signal and a quadrature down-converter down-converts the RF signal to baseband quadrature signal components. A local oscillator signal source provides the up-converter and the down-converter with a local oscillator signal and is operable in two states. In a second of the states the local oscillator signal is applied to the up-converter and the down-converter and a phase shift is made to the signal applied to up-converter or the down-converter compared to the first of the states. A processor monitors properties of the down-converted signal while the local oscillator signal source is operating in the first state and the second state. The processor calculates a correction to apply to the baseband observation signal to correct for errors introduced by the observation path. The processor also calculates a correction to apply to the input signal to correct for errors introduced in the transmit path.

Measuring and correcting errors in a transmit chain with an IQ up-converter and IQ down-converter

The present disclosures an amplification unit which comprises a first amplifier and a second amplifier connected in parallel, the first amplifier and the second amplifier comprising semiconductor devices that are not the same amplifier design. The present application also discloses a signal input line connected to the first amplifier and the second amplifier. A signal output line is also disclosed which is connected to the first amplifier and the second amplifier.

A linearized power amplifier including a predistorter and a feedforward circuit is described. By using both a predistorter and a feedforward cancellation system the linearization of the amplifier is increased. The accuracy of the amplified signal may be further improved by training the predistorter using the error signal produced by the feedforward cancellation system. Improved accuracy in the linearizer results in a reduction in the power requirement of the error amplifier and a relaxation in the phase, amplitude and delay accuracy of the feedforward loop.

Linearised power amplifier

Linear power amplifiers tend to be inefficient. This is a particular problem for RF amplifiers in a cellular base station. In order to improve the efficiency of such amplifiers, attempts have been made to modulate the power supply to the amplifier proportional to the envelope of the signal to be amplified. An UMTS signal requires power supply modulation at frequencies of the order of 10 to 20 megahertz. When quantization noise is taken into account, oversampling becomes desirable. However, switching power supplies at frequencies of the order of 40 or 80 or even 160 megahertz becomes difficult. By modifying the coding of phases of the power supply to be switched so that the number of phases enabled is proportional to the desired power supply output voltage rather than the length of a pulse in a time domain on any particular phase being proportional to the output voltage, dramatic improvements are achieved in switching losses, balance between phases and accurate tracking of the input signal. Rotation of switching across the phases achieves good balance and by jittering or randomizing the rotation, switching noise may be moved out of band.

Methods and apparatus for controlling the output voltage of a switched-mode power supply

A significant part of the cost of a base station in the cellular mobile radio system is the power amplifier. Thus it is desirable to maximise usage of a power amplifier and in particular to gain the best power output from the amplifier or to improve its efficiency. Such power amplifiers, however, must operate within strict spectral boundaries and thus power amplifiers are typically over-specified in order to ensure that the spectral requirements are met. By measuring the output of the amplifier and determining distortion factors and then adaptively adjusting the operating characteristics of the amplifier, the degree of over-specification of the amplifier required may be reduced with consequent cost and environmental savings.

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Bishops Stortford, United Kingdom

Martin O'Flaherty