RF Power Amplifier Feed-Forward Delay for Pulse Overshoot Control
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Solution Overview
Problem
Conventional RF power amplifiers produce pulses with undesirable overshoot due to the inherent behavior of the RF power amplifier stage, where the gain varies at different power levels, leading to a sharp rise time that the digital control cannot adjust quickly enough, resulting in output power overshoot.
Innovation Solution
A feed-forward design with a RF delay circuit and gain/phase adjustment components is implemented, where the RF input signal is split and processed in both digital and analog domains, with appropriate delays to ensure timely application of gain and phase adjustments, using a SAW filter for analog delay and a Field Programmable Gate Array (FPGA) for digital control, to produce a compensated RF signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the RF power amplifier stage operates with high gain to amplify the input signal, then the output power is increased, but the gain varies at different power levels causing overshoot in the output power pulse
Solution Approach 1:
The patent applies preliminary action by delaying the RF signal in the analog domain using a delay circuit before it reaches the power amplifier stage. This delay allows the digital control system to pre-calculate and apply appropriate gain and phase adjustments before the signal is amplified, preventing overshoot by preparing compensation in advance rather than reacting after the overshoot occurs.
Solution Approach 2:
The patent implements feedback by using the delayed RF signal to generate control signals that adjust the gain and phase of the main signal path. The digital processing circuitry compares the delayed signal with reference values and generates corrective control signals that are applied to the power amplifier stage, creating a closed-loop control system that maintains precise output power control.
2Manufacturing precision
If the digital control processing is made complex to compensate for gain variations, then the output power precision is improved, but the processing time increases causing the digital control to be too slow to adjust quickly
Solution Approach 1:
The delay circuit performs preliminary action by advancing the control signal generation process. By delaying the main RF signal path relative to the control signal path, the system allows sufficient time for complex digital processing to complete while ensuring the control signals are ready before the amplified signal needs adjustment. This temporal arrangement enables complex calculations without sacrificing response time.
Solution Approach 2:
The patent segments the control system into separate digital and analog domains. The digital processing circuitry handles complex calculations for gain and phase control, while the analog delay circuit and power amplifier stage handle signal manipulation. This segmentation allows each component to be optimized independently - digital processing can be complex and precise while the analog path provides real-time signal control.
3Speed
If the rise time of the output power pulse is made sharp to improve signal quality, then the signal quality is improved, but the gain variation at different power levels causes overshoot
Solution Approach 1:
The delay circuit enables preliminary action by providing time for the digital control system to calculate and apply gain and phase adjustments before the sharp rise time pulse is generated. The delayed signal path allows the control system to prepare compensation for the upcoming power transition, ensuring that even with sharp rise times, the output power remains precise without overshoot.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively limits overshoot in the power pulse output, providing improved square wave pulses by ensuring timely adjustment of gain and phase, reducing the undesirable overshoot compared to conventional amplifiers.
Implementation Method 1
using a SAW filter for analog delay
Data Source
AI summary
A power amplifier for producing an amplified radio frequency (RF) signal from an input RF signal includes, inter alia, an RF splitter configured to receive the input RF signal and split the input RF signal into a first split signal and a second split signal; digital processing circuitry configured to receive a digital representation of the first split signal and to produce a gain control signal and a phase control signal; an RF delay stage configured to receive the second split signal and to produce a delayed representation of the second split signal; a gain adjustment stage configured to receive the gain control signal and to adjust a gain based on the gain control signal; a phase adjustment stage configured to receive the phase control signal gain-adjusted signal and to adjust a phase based on the phase control signal, wherein the gain adjustment stage and the phase adjustment stage collectively produce a phase-adjusted and gain-adjusted signal; and an RF power amplifier stage, configured to receive the phase-adjusted and gain-adjusted signal and to produce the amplified RF signal.