| 摘要 |
RF power amplifier distortion is measured in the presence of multi-frequency input signals, by sweeping a local oscillator to tune RF input and output receivers. When the power detected by the input receiver exceeds a carrier energy threshold, the operation of a predistortion processor is blanked. This creates an adaptive notch filter, which allows for the direct measurement of low level distortion power in the presence of high power carriers. The unnecessary complexity of using controllably interrupted high isolation switches in the signal flow path of the output receiver in certain applications may be effectively obviated by buffer amplifier-passband filter stages. These buffer-filter stages provide additional gain to offset the fact that the signal level extracted from the output amplifier is very low, and prevent producing IMDs in the swept receiver's mixer. They are preferably implemented of the same bandpass filter in the swept input receiver.
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