Power Amplifier Signal Shaping for Lower IAR and Spectral Leakage
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Solution Overview
Problem
Power amplifiers in mobile devices face inefficiencies due to high power consumption and distortion issues, particularly with high data rate signals causing spectral leakage and adjacent channel interference, which violate the spectrum emission mask and result in poor performance and user dissatisfaction.
Innovation Solution
A method to reduce the Instantaneous to Average Power Ratio (IAR) of a transmitter system by receiving an input digital signal, extracting magnitude information, sorting and filtering samples using an FIR filter, and subtracting the output from a delayed version of the input signal, with scaling and peak spacing optimization to minimize distortion and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the power amplifier operates at high power levels to meet increasing data rate demands, then data transmission capability is improved, but power consumption increases and battery life deteriorates
Solution Approach 1:
The patent applies dynamic back-off techniques where the power amplifier's operating point is dynamically adjusted based on signal conditions. The system varies the back-off level according to the instantaneous signal characteristics, allowing the PA to operate efficiently across different power levels rather than at a fixed point, thus improving overall power efficiency while maintaining data transmission capability
Solution Approach 2:
The patent changes key operating parameters including the instantaneous-to-average ratio (IAR) of the signal, the back-off level, and the power amplifier bias point. By dynamically adjusting these parameters based on signal conditions, the system optimizes the trade-off between power consumption and data transmission performance
2Productivity
If the power amplifier amplifies high data rate signals with fluctuated envelopes, then data rate capability is improved, but spectral leakage and adjacent channel interference increase violating the spectrum emission mask
Solution Approach 1:
The patent applies preliminary signal processing techniques before the signal reaches the power amplifier. These pre-processing actions include envelope shaping and predistortion that prepare the signal to minimize spectral leakage and adjacent channel interference during amplification, thus preventing distortion rather than correcting it afterward
Solution Approach 2:
The patent converts the potentially harmful fluctuated envelope of high data rate signals into a beneficial characteristic by applying controlled envelope shaping. The signal's envelope variations are manipulated to create a more favorable spectral profile that reduces spectral leakage while maintaining the high data rate capability
3Manufacturing precision
If the power amplifier operates in the linear region to avoid distortion, then signal fidelity is improved, but power efficiency deteriorates due to the need to back off from maximum power
Solution Approach 1:
The patent dynamically adjusts the power amplifier's operating region based on signal conditions. Rather than operating continuously in the linear region, the system transitions between linear and non-linear operating modes, applying digital correction techniques when operating in non-linear modes to maintain signal fidelity while improving power efficiency
Solution Approach 2:
The patent introduces digital signal processing algorithms as an intermediary between the power amplifier and the output signal. These algorithms compensate for non-linear distortion introduced when the PA operates outside the linear region, allowing the system to achieve both power efficiency and signal fidelity through the mediating作用 of digital correction
4Object-generated harmful factors
If clipping techniques are applied to reduce spectral leakage, then spectral emission compliance is improved, but signal distortion increases
Solution Approach 1:
The patent converts the harmful clipping distortion into a beneficial characteristic by applying digital predistortion and correction techniques. The clipping operation is intentionally applied to reduce spectral leakage, and the resulting distortion is compensated for through digital signal processing, thus converting the harmful distortion into an acceptable trade-off for achieving spectral compliance
Solution Approach 2:
The patent introduces digital signal processing as an intermediary that compensates for clipping-induced distortion. The clipping operation is performed to reduce spectral leakage, and the digital intermediary processes the clipped signal to restore signal fidelity, thus separating the spectral shaping function from the distortion introduction
Data Source
AI summary
Disclosed is a method of reducing the Instantaneous to Average Power Ratio, IAR, of a transmitter system, comprising the steps of: receiving an input digital signal comprising a plurality of samples; extracting magnitude information for each of the plurality of samples; selecting a plurality of samples whose magnitude exceeds a predefined threshold; sorting, by magnitude, the selected plurality of samples; selecting from the sorted plurality of samples, only those samples having a spacing more than a first pre-defined spacing and filtering those samples, using an FIR filter; subtracting the output of the FIR filter from a delayed version of the input digital signal to produce an output signal.