RF Radiation Control Using Reflected-Wave Pulse Switching
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Solution Overview
Problem
Conventional RF energy radiation devices face challenges in maintaining reliable output power due to reflected-wave power, leading to insufficient heating of targets and protection issues with RF power elements, especially during plasma ignition and when load impedance causes total reflection.
Innovation Solution
The RF energy radiation device employs an oscillator with variable pulse width and period, a power amplifier, a detector, and a protection circuit that switches between control modes to manage reflected-wave power, allowing continuous operation and preventing power amplifier shutdown even during high reflected-wave power conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If output power is supplied as burst waves to protect RF power elements from reflected-wave power, then reliability of RF power elements is improved, but heating efficiency deteriorates due to intermittent operation
Solution Approach 1:
The patent applies periodic action by controlling the RF power amplifier to operate in burst wave mode with specific on-time and off-time intervals. This periodic operation allows the system to deliver high power during on-time for effective heating while providing recovery time during off-time to prevent damage from reflected-wave power, thus resolving the contradiction between heating efficiency and component reliability.
2Duration of action of stationary object
If output level is gradually raised to prevent device protection shutdown, then continuous operation is achieved, but reflected-wave power exceeds allowable range causing damage risk
Solution Approach 1:
The patent implements feedback control by continuously detecting reflected-wave power levels and using this information to control the RF power amplifier operation. The system monitors reflected-wave power in real-time and adjusts the burst wave parameters accordingly, enabling continuous operation while maintaining reflected-wave power within safe limits through closed-loop control.
3Productivity
If matching unit is used to handle total reflection during plasma ignition, then plasma ignition success is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the matching function from a separate external matching unit and integrates it directly into the RF power amplifier circuitry. By incorporating the matching network within the amplifier itself, the system achieves effective plasma ignition support through impedance matching while eliminating the need for additional external components, thus reducing device complexity and cost.
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
This solution enhances the reliability of RF energy radiation by maintaining stable operation and protecting RF power elements, ensuring efficient heating even when load impedance is unstable, and allowing for efficient plasma ignition without excessive power amplifier stress.
Implementation Method 1
a power amplifier, amplifies the RF signal to generate traveling-wave power
Implementation Method 2
a detector, detects reflected-wave power that returns from the radiation element
Data Source
AI summary
In an RF energy radiation device, a controller controls both an oscillator and a power amplifier to set an operation mode to either a first control mode or a second control mode, in accordance with reflected-wave power that returns from a radiation element and is detected by a detector. In the first control mode, the oscillator oscillates a pulsed RF signal having a first pulse width and a first pulse period. In the first control mode, a protection circuit does not shut off traveling-wave power. In the second control mode, the oscillator oscillates a pulsed RF signal having both a second pulse width different from the first pulse width and a second pulse period different from the first pulse period. Alternatively, the oscillator continuously oscillates an RF signal. In the second control mode, the protection circuit shuts off the traveling-wave power when the reflected-wave power exceeds a predetermined threshold.