Classifications

• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03F—AMPLIFIERS
  • H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
  • H03F1/32—Modifications of amplifiers to reduce non-linear distortion
  • H03F1/3223—Modifications of amplifiers to reduce non-linear distortion using feed-forward
  • H03F1/3229—Modifications of amplifiers to reduce non-linear distortion using feed-forward using a loop for error extraction and another loop for error subtraction

Definitions

• the present invention relates to feed forward compensation circuits.
• feed forward compensation circuits to compensate for the non-linearity of radio frequency (RF) power amplifiers.
• RF radio frequency
• feed forward compensation circuits included components that can be trimmed to tune the circuit for operation.
• One of the main drawbacks of the feed forward scheme is the difficulty in maintaining an optimum operating state due to the drift of parameters of the components.
• An object of the present invention is to provide an improved feed forward compensation circuit.
• a feed forward compensating circuit for coupling to a radio frequency power amplifier having an input and an output comprising: a first loop for generating an error signal representation of signal distortion due to the power amplifier; and a second loop for the applying a compensating signal derived from the error signal to the output.
• the first loop including a first comparator for controlling amplitude adjustment therein and a second comparator for controlling phase adjustment therein.
• a method of compensating for radio frequency power amplifier distortion comprising the steps of: determining a difference between an input signal to the RF power amplifier and an output from the RF power amplifier.
• Fig. 1 illustrates a known feed forward compensation circuit
• Fig. 2 illustrates a feed forward compensation circuit in accordance with an embodiment of the present invention
• Fig. 3 graphically illustrates various signals within the circuit of Fig. 2 when operational.
• the feed forward compensation circuit 10 includes an input 12, and output 14, a nulling loop 16 and a compensation loop 18.
• the nulling loop 16 includes a first splitter 20, in front of a power amplifier 22, a second splitter 24 after the power amplifier 22, an amplitude adjuster 26 a phase adjuster 28 and a comparator 30.
• the compensation loop 18 includes an amplitude adjuster 32, a phase adjuster 34, and an amplifier 36 and a combiner 38.
• the nulling loop samples an RF signal at the input 12 and at an output of amplifier 22 via splitters 20 and 24. Because of non-linearity of the power amplifier 22, distortions are introduced in the RF amplification chain between the input 12 and the output 14.
• the nulling loop 16 by comparing the input signal to the output of the power amplifier, generates an error signal, which when added with the correct phase and amplitude to the signal as output by the power amplifier 22, can theoretically, cancel out the distortion introduced by the power amplifier.
• the error signal is controlled in amplitude by the amplitude adjuster 32 and by the phase adjuster 34, amplified by the error amplifier
• the feed forward compensation circuit 50 includes an input 52, an output 54, a nulling loop 56 and a compensation loop 58.
• the nulling loop 56 is established by a first splitter 60 before a power amplifier 62 and a second splitter 64 after the power amplifier 62.
• a first path from the first splitter 60 includes a first amplitude adjuster 66, a first phase adjuster 67 and a third splitter 70.
• Detectors 76 and 74 are coupled to the differential inputs of an operational amplifier 78 whose output controls the first amplitude adjuster 66.
• a ninety-degree combiner 80 has its outputs S2, S3 coupled to third and fourth detectors 82 and 84 whose outputs are coupled to a second operational amplifier 86 whose output controls the phase controller 68.
• Input to the 90° combiner 80 is provided by fifth and sixth splitters 88 and 90 connected to splitters 70 and 72, respectively.
• the other outputs of splitters 88 and 90 are connected to 3dB combiner
• the compensation loop 58 includes the 3dB combiner 92, amplitude adjuster 94, phase adjuster 96 and an error amplifier 98, series connected.
• the output of error amplifier 98 is added to the output of splitter 64 via a combiner 100.
• the third and fourth detectors 82 and 84 are configured to maintain an equal level of signals R and D applied to comparison network made of the 3dB splitters 88, 90 and 92 and the 3dB 90° combiner 80. Operation of this combination can be further understood from Figure 3 which shows the change of amplitude of the signals at the connections when the phase between signals R and D is modified between 0° and 360°.
• the signal at the output of 3dB combiner 92 is minimum when signals output from comparator 80 are equal.
• the slope of the variation of the signals output from comparator 80 are opposite which make it possible to generate a differential DC signal which is 0 when the error signal is minimum.

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• Physics & Mathematics (AREA)
• Nonlinear Science (AREA)
• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Amplifiers (AREA)

Applications Claiming Priority (3)

Publications (1)

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ID=23209543

Family Applications (1)

Country Status (3)

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• 2002
  • 2002-08-13 EP EP02754031A patent/EP1425848A2/de not_active Withdrawn
  • 2002-08-13 WO PCT/CA2002/001254 patent/WO2003017478A2/en not_active Ceased
  • 2002-08-13 AU AU2002322892A patent/AU2002322892A1/en not_active Abandoned

Non-Patent Citations (1)

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