IMD Limiter
First Claim
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1. An intermodulation distortion limiter for controlling the ratio of average power to peak envelope power in an output signal from a power amplifier comprising:
- control means, responsive to a control signal, for controlling the amplitude of an input signal applied to the power amplifier, the input signal having associated therewith, when applied to the power amplifier, an average power and a peak envelope power;
first detector circuit means for detecting the difference between the peak envelope power and the average power of the input signal to provide a first reference signal thereby;
selectable reference source for providing first and second selectable reference signals;
reference generator means for generating a second reference signal that is responsive to the first reference signal and the first selectable reference signal;
second detector circuit means for comparing the peak envelope power of the output signal and the second selectable reference signal to obtain a first analog representation of the peak envelope power difference thereby;
third detector circuit means for detecting the difference between the average power of the output signal and the second reference signal to obtain a second analog representation of the average power difference; and
combination means for combining the first and second analog representations to obtain the control signal to which the control means is responsive.
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Abstract
An intermodulation distortion limiter controls the ratio of average power to peak envelope power in the output of a linear power amplifier and this protects against excess non-linearity by reducing the drive power when the ratio exceeds a similar ratio associated with the incoming RF signal.
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Citations
14 Claims
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1. An intermodulation distortion limiter for controlling the ratio of average power to peak envelope power in an output signal from a power amplifier comprising:
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control means, responsive to a control signal, for controlling the amplitude of an input signal applied to the power amplifier, the input signal having associated therewith, when applied to the power amplifier, an average power and a peak envelope power; first detector circuit means for detecting the difference between the peak envelope power and the average power of the input signal to provide a first reference signal thereby; selectable reference source for providing first and second selectable reference signals; reference generator means for generating a second reference signal that is responsive to the first reference signal and the first selectable reference signal; second detector circuit means for comparing the peak envelope power of the output signal and the second selectable reference signal to obtain a first analog representation of the peak envelope power difference thereby; third detector circuit means for detecting the difference between the average power of the output signal and the second reference signal to obtain a second analog representation of the average power difference; and combination means for combining the first and second analog representations to obtain the control signal to which the control means is responsive. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of controlling the ratio of average power to peak envelope in an output signal from a power amplifier, comprising:
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controlling the amplitude of an input signal applied to the power amplifier in response to a control signal, the input signal having associated therewith, when applied to the power amplifier, an average power and a peak envelope power; detecting the difference between the peak envelope power and the average power of the input signal to provide a first reference signal; providing a first and second selectable reference signal; generating a second reference signal that is in response to the first reference signal and the first selectable reference signal; detecting the difference between the peak envelope power of the output signal and the second selectable reference signal to obtain a first analog representation of the peak envelope power difference; detecting the difference between the average power of the output signal and the second reference signal to obtain a second analog representation of the average power difference; and combining the first and second analog representations to obtain the control signal. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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Specification