Envelope peak and trough limiting to improve amplifier efficiency and distortion characteristics
First Claim
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1. A method for use in amplifying a non-constant envelope signal, the method comprising:
- (a) separating the signal into two component signals, including;
(1) a constant envelope signal containing phase and frequency information; and
(2) a baseband signal representing the envelope;
(b) limiting the baseband signal to magnitudes lying either above or below a predetermined boundary value;
(c) amplifying at least one of the component signals; and
(d) combining the magnitude-limited baseband signal and the constant envelope signal to form an output signal having a limited but non-constant envelope.
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Abstract
The envelope of a non-constant envelope signal is limited to certain maximum and minimum values. An envelope value is calculated for each pair of I-Q samples of the non-constant envelope signal and then is compared to the maximum and minimum values. If the envelope value lies above or below the maximum and minimum values, the I and Q signals are scaled so that the envelope value lies between these values. In some embodiments, the threshold values are selected to ensure that the probability that the envelope value will exceed these values is less than a predetermined amount (e.g., between 0.01 and 0.001).
134 Citations
26 Claims
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1. A method for use in amplifying a non-constant envelope signal, the method comprising:
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(a) separating the signal into two component signals, including;
(1) a constant envelope signal containing phase and frequency information; and
(2) a baseband signal representing the envelope;
(b) limiting the baseband signal to magnitudes lying either above or below a predetermined boundary value;
(c) amplifying at least one of the component signals; and
(d) combining the magnitude-limited baseband signal and the constant envelope signal to form an output signal having a limited but non-constant envelope. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A power amplifier for use in amplifying a non-constant envelope signal, the amplifier comprising:
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(a) an envelope extractor that divides the non-constant envelope signal into two component signals;
(1) a constant envelope signal containing phase and frequency information; and
(2) a baseband signal representing the envelope;
(b) an envelope limiter that limits the baseband signal to magnitudes lying either above or below a predetermined boundary value;
(c) amplification circuitry that amplifies at least one of the component signals; and
(d) an envelope combiner that combines the magnitude-limited baseband signal and the constant envelope signal to form an output signal having a limited but non-constant envelope. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17)
(a) receive input signals representing in-phase (I) and quadrature (Q) components of the non-constant envelope signal; and
(b) provide output signals representing limited envelope in-phase (IL) and quadrature (QL) components of the output signal.
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18. A method for use in limiting the envelope of a non-constant envelope signal, the method comprising:
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(a) receiving signals representing in-phase (I) and quadrature (Q) components of the non-constant envelope signal;
(b) for at least one pair of samples in the I and Q signals, calculating an envelope value for the non-constant envelope signal;
(c) comparing each envelope value to at least one threshold value; and
(d) if the envelope value exceeds the threshold value, scaling the I and Q signals so that the envelope value does not exceed the threshold value. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26)
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Specification