Frequency-Dependent Envelope Tracking for Wideband PA Efficiency
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Solution Overview
Problem
Envelope tracking systems deteriorate when used with wideband signals due to their reliance on frequency-specific isogain curves, which are not valid across a range of frequencies, leading to inefficiencies in power amplifier performance.
Innovation Solution
Implementing frequency-dependent envelope tracking that considers both instantaneous amplitude and frequency of the transmit signal, using an isogain surface to select bias voltage for the power amplifier, rather than relying on frequency-specific curves, thereby enabling efficient operation across a wider range of frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If frequency-specific isogain curves are used for envelope tracking, then power amplifier efficiency is improved at specific frequencies, but performance deteriorates when used with wideband signals across a range of frequencies
Solution Approach 1:
The patent transitions from one-dimensional frequency-specific isogain curves to two-dimensional isogain surfaces that map both frequency and amplitude to optimal bias voltage. This dimensional expansion allows the system to handle wideband signals by providing appropriate bias voltage settings for any combination of frequency and amplitude, resolving the contradiction between efficiency at specific frequencies and adaptability across frequency ranges.
Solution Approach 2:
The system dynamically adjusts the bias voltage parameter based on both instantaneous frequency and amplitude of the transmit signal. By changing the bias voltage in response to frequency variations within the wideband signal, the power amplifier maintains optimal efficiency across different frequency components while preserving the adaptability needed for wideband operation.
2Device complexity
If bias voltage is adjusted based only on instantaneous amplitude, then envelope tracking is simple to implement, but efficiency is lost when frequency varies
Solution Approach 1:
The system implements dynamic bias voltage adjustment that responds to both instantaneous amplitude and frequency of the transmit signal. This dynamic approach allows the envelope tracking to adapt to frequency variations within wideband signals, maintaining power amplifier efficiency without requiring overly complex implementation, as the frequency information is already available from the signal processing chain.
Data Source
AI summary
An envelope tracking system includes an instantaneous amplitude circuitry, an instantaneous frequency circuitry, and a two-dimensional (2D) bias voltage selection circuitry. The instantaneous amplitude circuitry is configured to determine an instantaneous amplitude of a transmit signal. The instantaneous frequency circuitry is configured to determine an instantaneous frequency of the transmit signal. The two-dimensional (2D) bias voltage selection circuitry is configured to determine a bias voltage based on both the instantaneous amplitude and the instantaneous frequency of the transmit signal, and control power supply circuitry to supply the determined bias voltage to a power amplifier that is configured to amplify the transmit signal.