RF Envelope Pulsing via Phase-Switched Switch-Mode Amplifiers
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Solution Overview
Problem
Existing RF signal generators face limitations in precisely controlling RF envelope power, particularly in achieving fast rise and fall times, high pulsing frequencies, and small duty cycles, due to limitations in power supply control and RF power amplifier drive control methods, which are not easily extendable to high efficiency switch-mode power amplifiers and result in complex control circuits and reduced reliability.
Innovation Solution
A radio frequency (RF) power generator using a master and slave switch-mode amplifier configuration with phase-controlled Class E amplifiers, where the phase difference between the RF signals is alternated to control the RF envelope, balancing voltage and current profiles and reducing thermal stresses, thereby increasing reliability and flexibility in generating various RF envelope waveforms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If power supply control methods are used for RF envelope pulsing, then RF power can be modulated, but the pulse rise and fall speeds are limited by the dynamic response of the DC rail voltage
Solution Approach 1:
The patent replaces the mechanical/power supply control system with a phase-based control system. Instead of modulating the DC rail voltage amplitude, the invention uses phase shifters to control the phase of RF signals driving the power amplifier, thereby achieving fast envelope modulation without being limited by power supply response time.
Solution Approach 2:
The invention changes the control parameter from voltage amplitude to phase angle. By varying the phase difference between control signals (e.g., from 0 to 360 degrees), the RF envelope amplitude is controlled, enabling fast rise and fall times that are not constrained by power supply dynamics.
2Manufacturing precision
If linear power amplifiers are used for RF envelope pulsing, then multi-amplitude-level pulsing is achieved, but large differential powers need to be dissipated resulting in large thermal capacities
Solution Approach 1:
The patent changes the operating parameter of the power amplifier from linear mode to switch-mode operation. By controlling the duty cycle and phase of the drive signal, the amplifier operates in efficient switching regions, reducing power dissipation and thermal requirements while still achieving precise multi-amplitude-level pulsing through phase modulation.
3Adaptability or versatility
If full-bridge topology with four power switches is used for phase-controlled RF power amplifier, then flexible RF envelope waveform generation is facilitated, but parts count and cost increase and reliability reduces
Solution Approach 1:
The patent extracts and removes unnecessary components from the full-bridge topology. By using a simplified configuration with fewer power switches and eliminating the need for complex gate drive control circuits, the invention maintains flexible RF envelope waveform generation while reducing parts count, cost, and potential failure points.
Solution Approach 2:
The invention enables the RF power amplifier to self-regulate its output envelope through phase control of the drive signal, eliminating the need for complex external gate drive control circuits. This self-service approach reduces component count and improves reliability while maintaining waveform flexibility.
Data Source
AI summary
A radio frequency (RF) power generator includes a first switch-mode amplifier that generates a first RF signal in accordance with a first control signal and a second switch-mode amplifier that generates a second RF signal in accordance with a second control signal. The first and second control signals determine a phase difference between the first and second RF signals. An output signal envelope is based on the first and second RF signals and the phase difference. The first control and second control signals alternate phases of the first and second RF signals.