Selective DAC Cancellation for High-PAPR ADC Dynamic Range
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Solution Overview
Problem
Analog to digital converters (ADCs) in communication devices face limitations in dynamic range due to high peak to average power ratio (PAPR) signals, leading to noise and distortion, especially in full duplex systems where echoes from transmitted signals can mask received signals, and existing solutions like pre-cancellation DACs increase power consumption and cost without always providing significant performance gains.
Innovation Solution
Implementing a Peak Amplitude Separation element that evaluates signal amplitudes and applies a reference threshold to a pre-cancellation DAC, allowing only signals above the threshold to be processed, thereby reducing PAPR and improving ADC dynamic range without adding significant noise, using a simple and low-power DAC configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pre-cancellation DAC is used to reduce PAPR peaks, then ADC dynamic range is improved, but power consumption and device cost increase
Solution Approach 1:
The patent applies local quality by making the DAC operate selectively only during high PAPR events rather than continuously. The Peak Amplitude Separation element identifies when PAPR exceeds a threshold and activates the cancellation DAC only during those specific time intervals, rather than maintaining full DAC operation continuously. This localized application reduces overall power consumption while maintaining ADC dynamic range improvement where needed.
Solution Approach 2:
The patent implements periodic action through the time-domain selective cancellation approach. The system periodically monitors the input signal for high PAPR conditions and activates the cancellation DAC in periodic bursts corresponding to these events. This intermittent operation pattern reduces average power consumption compared to continuous DAC operation, while still providing dynamic range improvement during critical high-peak periods.
2Measurement precision
If pre-cancellation DAC is used to reduce PAPR peaks, then ADC dynamic range is improved, but device complexity and cost increase
Solution Approach 1:
The patent reduces device complexity by applying local quality - the cancellation DAC and associated circuitry are activated only during high PAPR events identified by the Peak Amplitude Separation element. This selective activation reduces the average complexity burden on the system compared to having full cancellation capability always active, while maintaining ADC dynamic range improvement during critical periods.
Solution Approach 2:
The patent employs a simple, low-resolution DAC (potentially 1-bit or few-bit) that is inexpensive and consumes minimal resources. Rather than using a high-performance, expensive DAC continuously, the system uses a simplified DAC that operates only during brief high PAPR events. This approach reduces device complexity and cost while achieving the necessary dynamic range improvement during critical moments.
3Productivity
If full duplex operation is implemented, then communication efficiency is improved, but received signals are masked by transmitted signal echoes
Solution Approach 1:
The patent applies preliminary anti-action by using the known transmitted signal to pre-calculate and generate cancellation signals before the echoes interfere with received signals. The Peak Amplitude Separation element identifies high PAPR events in the transmitted signal, and the cancellation DAC generates compensating signals that are subtracted from the received signal path, preventing echo masking before it degrades communication performance.
Solution Approach 2:
The patent converts the harmful effect of high PAPR peaks and transmitted signal echoes into a benefit by using the known transmitted signal characteristics to generate precise cancellation signals. The same high PAPR events that cause distortion are identified and used to trigger targeted cancellation, transforming the problem into a solution where the transmitted signal's own characteristics are used to eliminate its harmful echoes.
Data Source
AI summary
Increasing an analog to digital converter (ADC) dynamic range for a communications device. In the communications device, a reference threshold is established for a peak to average power ratio (PAPR) improvement factor for RF signals received by the communications device. A digital to analog converter (DAC) adjustment factor is established for a DAC to account for inaccuracies of a pre-cancellation DAC and fine tuning of an analog gain of received RF signals. A peak amplitude separation element, disposed within the communications device, evaluates an absolute value of a portion of a particular RF signal against the reference threshold. Upon the peak amplitude separation element determining that the portion is smaller than the reference threshold, the element assigns a zero value to a DAC signal current sample; otherwise, the element assigns a quantized value of the sample to the DAC signal current sample, used in adjusting a post-cancellation signal sample.