Nonlinear distortion detecting circuit and nonlinear distortion compensating circuit for transmitter
First Claim
1. A nonlinear distortion detecting circuit in a transmitter which generates a third-order intermodulation distortion due to nonlinearity thereof, comprising:
- a power amplifier;
input means for entering two reference signals having respective different frequencies at a stage preceding said power amplifier;
extracting means for extracting a frequency component having a frequency which is twice the difference between the frequencies of said two reference signals, based on a signal supplied from a predetermined section of said power amplifier; and
detecting means for detecting the frequency component extracted by said extracting means.
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Abstract
An input unit enters two reference signals having respective different frequencies at a stage preceding a power amplifier. The reference signals are delivered through a predistortion circuit to a power amplifier, and supplied from a predetermined section of the power amplifier. The signals from the power amplifier contain a third-order intermodulation distortion component. Based on the signals from the power amplifier, an extracting unit extracts a frequency component having a frequency which is twice the difference between the frequencies of said two reference signals. A detecting unit detects the extracted frequency component thereby to output a DC voltage. Since the extracted frequency component is correlated to the third-order intermodulation distortion component, the DC voltage represents the magnitude of the third-order inter-modulation distortion component.
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Citations
8 Claims
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1. A nonlinear distortion detecting circuit in a transmitter which generates a third-order intermodulation distortion due to nonlinearity thereof, comprising:
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a power amplifier; input means for entering two reference signals having respective different frequencies at a stage preceding said power amplifier; extracting means for extracting a frequency component having a frequency which is twice the difference between the frequencies of said two reference signals, based on a signal supplied from a predetermined section of said power amplifier; and detecting means for detecting the frequency component extracted by said extracting means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification