Distortion compensation control for a power amplifier
First Claim
1. A distortion compensation circuit for a power amplifier comprising:
- an input path for forwarding a combined signal to said amplifier to form an amplified signal, said combined signal comprising at least one carrier and a reference signal;
a compensation path for producing a compensation signal for compensating for the distortion produced by said amplifier;
a control unit;
coupler for coupling said amplified signal to said control unit; and
said control unit comprising;
error signal means for producing a first signal indicative of the AM/AM distortion within an amplified reference signal component of said amplified signal and for producing a second signal indicative of the AM/PM distortion within said amplified reference signal component;
an envelope detector for detecting the instantaneous RF signal envelope of said amplified signal,a first mixer for correlating said first signal with said signal envelope in order to form a first error signal anda second mixer for correlating said second signal with said signal envelope in order to form a second error signal; and
a gain and phase adjuster, responsive to said control unit, for adjusting the gain and phase of said compensation signal in order to minimize said error signals.
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Accused Products
Abstract
A control arrangement and method for controlling a gain and phase adjuster used for controlling the gain and phase of a compensation signal for compensating for the distortion produced by a power amplifier is disclosed. The control arrangement makes use of a reference signal, of known frequency, which is amplified along with the desired carrier signals. The reference signal component of the amplified signal is then isolated and a comparison is made, either with the actual reference signal, e.g., by a QAM demodulator, or alternatively with the known frequency of the reference signal, e.g., by a FM discriminator, in order to determine the differences in gain and in phase of the reference signal component of the amplified signal in comparison with the reference signal. For example, a QAM demodulator is used for producing a first difference signal indicative of the phase switch difference, and a second difference signal indicative of the gain switch difference. These signals are then correlated with the signal envelope of the main signal in order to produce signals indicative of the sign and magnitude of the control signals used to adjust the gain and phase adjuster in a feed back loop.
153 Citations
19 Claims
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1. A distortion compensation circuit for a power amplifier comprising:
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an input path for forwarding a combined signal to said amplifier to form an amplified signal, said combined signal comprising at least one carrier and a reference signal; a compensation path for producing a compensation signal for compensating for the distortion produced by said amplifier; a control unit; coupler for coupling said amplified signal to said control unit; and said control unit comprising; error signal means for producing a first signal indicative of the AM/AM distortion within an amplified reference signal component of said amplified signal and for producing a second signal indicative of the AM/PM distortion within said amplified reference signal component; an envelope detector for detecting the instantaneous RF signal envelope of said amplified signal, a first mixer for correlating said first signal with said signal envelope in order to form a first error signal and a second mixer for correlating said second signal with said signal envelope in order to form a second error signal; and a gain and phase adjuster, responsive to said control unit, for adjusting the gain and phase of said compensation signal in order to minimize said error signals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of minimizing the intermodulation distortion produced by a RF power amplifier comprising the steps of:
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(a) introducing an RF signal to be amplified, said RF signal including a reference signal; (b) producing a compensation signal which will largely cancel the distortion produced by the RF power amplifier; (c) producing a pair of error signals indicative of the sign and magnitude of the distortion introduced by said RF power amplifier to the reference signal; and (d) adaptively adjusting the gain and phase of said compensation signal in order to minimize said error signals. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19)
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Specification