Signal Processing for ADC Clipping Compensation in AM Reception
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Solution Overview
Problem
Existing signal processing technologies fail to effectively compensate for the level decrease of target waves in signals that are clipped by analog-to-digital converters, particularly when strong interference waves cause amplitude exceeding the converter's range, leading to communication disruptions in amplitude modulation methods.
Innovation Solution
A signal processing device that includes an A-D converter, a controller with a counter to calculate clipped samples, a frequency converter, a filter, a rate converter, a digital amplifier, and an amplification factor adjuster, which adjusts the amplification factor based on the ratio of clipped to unclipped samples to compensate for the level decrease of target waves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the A-D converter processes signals with amplitude exceeding its range, then the interference wave can be converted to digital signal, but the target wave level declines due to clipping
Solution Approach 1:
The system performs preliminary detection of clipped samples before final signal processing. By counting clipped samples in advance and calculating the amplification factor adjustment coefficient based on the clipping ratio, the system prepares the appropriate amplification factor before amplifying the digital signal, thereby compensating for target wave level loss caused by clipping
Solution Approach 2:
The system dynamically changes the amplification factor parameter based on the clipping condition. By calculating the amplification factor adjustment coefficient from the ratio of clipped samples to total samples, and multiplying it with the preset amplification factor, the system adapts the amplification parameter to compensate for target wave level decline while maintaining interference wave suppression
2Loss of information
If the amplification factor is increased to compensate for clipped signal level, then the target wave level is restored, but the interference wave may cause further clipping
Solution Approach 1:
The system uses feedback from the clipped sample detection to adjust the amplification factor. By counting the number of clipped samples and calculating the amplification factor adjustment coefficient based on this feedback, the system determines the appropriate amplification level that compensates for target wave loss without excessively amplifying interference waves that would cause further clipping
Solution Approach 2:
The system applies partial amplification based on the proportion of clipped samples. Rather than uniformly amplifying the entire signal, the amplification factor adjustment coefficient is calculated based on the ratio of clipped samples to total samples, applying just enough amplification to compensate for target wave level loss while avoiding excessive amplification that would cause interference wave clipping
Data Source
AI summary
A signal processing device includes an A-D converter and a controller. The A-D converter converts an analog signal to a digital signal in which portions where the amplitude exceeds a predetermined range are clipped. A counter of the controller calculates, for the digital signal, a number of clipped samples for each predetermined number of period samples. A frequency converter performs frequency conversion of the digital signal. An LPF removes high frequency components of the digital signal. A rate converter converts a sampling rate of the A-D converter. A digital amplifier amplifies and outputs the digital signal. An amplification factor adjuster multiplies a preset amplification factor of the digital amplifier by an amplification factor adjustment coefficient based on a ratio of the number of regular samples to the number of period samples, to adjust the amplification factor.