Envelope Extraction for Power Amplifier Efficiency
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Solution Overview
Problem
Cellular devices face linearity issues and harmonic interference due to non-linearity in power amplifiers, particularly in Quadrature modulation, while polar modulation circuits become overly complex for handling large bandwidth signals, and existing solutions like bandwidth reduction in power supply waveforms or switched power supplies do not fully address efficiency and complexity concerns.
Innovation Solution
A communications device with an encoder generating digital baseband In-phase and Quadrature signals, a processor extracting envelope characteristics based on signal bandwidth, and a power amplifier producing amplified signals, which generates near constant envelope signals when bandwidth is below a threshold, reducing complexity and improving power efficiency by only removing envelope data from high-frequency components when bandwidth exceeds the threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If Quadrature modulation is used, then linearity and power efficiency are improved, but device complexity and bandwidth requirements increase
Solution Approach 1:
The patent extracts and removes the envelope component from the modulated signal, retaining only the constant envelope carrier wave for power amplification. This separation allows the use of efficient saturated power amplifiers while avoiding the complexity of handling the full envelope-varying signal through the amplifier.
Solution Approach 2:
The signal processing is divided into distinct stages: envelope extraction, constant envelope generation, and power amplification. By segmenting the signal processing function, the system can optimize each stage independently, using simple saturated amplifiers for the constant envelope portion while handling envelope variations separately.
2Loss of energy
If polar modulation is used, then power efficiency is improved, but circuit complexity increases significantly for large bandwidth signals
Solution Approach 1:
The envelope information is extracted from the polar modulated signal and separated from the carrier. This allows the carrier to be amplified using simple saturated power amplifiers without requiring complex broadband power amplifier designs, thus reducing circuit complexity while maintaining power efficiency.
Solution Approach 2:
Instead of trying to amplify the envelope-varying signal directly (which would require complex broadband amplifiers), the invention inverts the approach by amplifying only the constant envelope carrier and then recombining with the extracted envelope information, simplifying the amplifier design.
3Loss of energy
If envelope tracking power amplifier is used, then power efficiency is improved, but bandwidth of power supply waveform increases
Solution Approach 1:
The envelope component is extracted from the signal before power amplification. This removes the bandwidth-consuming envelope variations from the power supply waveform, allowing the use of simpler, narrower-bandwidth power supply circuits while still achieving high power efficiency through saturated amplifier operation.
Data Source
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AI summary
A communications device (10, 10') may include an encoder (11, 11') generating digital baseband In-phase (I) and Quadrature (Q) signals, a processor (12, 12') coupled to the encoder and extracting an envelope characteristic from the digital baseband I and Q signals based upon a bandwidth of the digital baseband I and Q signals. A power amplifier (18, 18') may be coupled downstream from the processor and may generate an amplified I and Q signal based upon the envelope characteristic.