Control scheme for distortion reduction
First Claim
1. A method of reducing the appearance of distortion in an output signal which a signal handling means produces in response to an input signal, the method comprising:
- sampling both the input and output signals;
frequency shifting one of the sampled signals by a frequency offset amount;
converting, by incoherent detection, the frequency-offset sampled signal and the other sampled signal to baseband signals, processing the baseband signals to produce control signals; and
predistorting the input signal under control of the control signals.
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Abstract
In predistorter (100), non-linear element (126) generates a distortion signal which is injected into the input (110) of a non-linear power amplifier (112 at 118). The distortion signal is optimised by a vector modulator to cancel distortion caused by amplifier (112). The control signals for the vector modulator are provided by a digital signal processor (FIG. 2). The input signal (110) and the output signal (114) are sampled and processed to produce an audio frequency error signal which is correlated in the DSP to produce the control signals for the vector modulator whilst avoiding analogue correlation problems.
66 Citations
24 Claims
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1. A method of reducing the appearance of distortion in an output signal which a signal handling means produces in response to an input signal, the method comprising:
sampling both the input and output signals;
frequency shifting one of the sampled signals by a frequency offset amount;
converting, by incoherent detection, the frequency-offset sampled signal and the other sampled signal to baseband signals, processing the baseband signals to produce control signals; and
predistorting the input signal under control of the control signals.- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A method as substantially hereinbefore described with reference to the accompanying figures.
- 21. Apparatus for reducing the appearance of distortion in an output signal which a signal handling means produces in response to an input signal, the apparatus comprising means for sampling both the input and output signals, means for frequency shifting one of the sampled signals by a frequency offset amount, means for converting, by coherent detection, the frequency offset sampled signal and the other sampled signal to baseband signals, means for processing the baseband signals to produce control signals, and means for predistorting the input signal under control of the control signals.
Specification