Microwave Oven Phase Control for Even Cooking
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Solution Overview
Problem
Microwave cooking appliances for professional use face challenges in optimizing cooking efficiency due to unpredictable changes in field distribution within the cooking chamber, especially in large appliances like combi-steamers, where small geometry changes affect field distribution and make it difficult to achieve even cooking.
Innovation Solution
A method and appliance design that uses two antennas supplied with coherent microwave radiation from a semiconductor amplifier, with a phase shifter to control the relative phase position of the microwave signals, minimizing backward-running signal power by dynamically adapting the phase based on detected forward and backward signals, allowing for real-time optimization of power coupled into the cooking item.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If field distribution measurement and control is implemented in large cooking chambers, then cooking evenness is improved, but device complexity and measurement reliability deteriorate due to unpredictable field distribution changes from geometry variations
Solution Approach 1:
The patent extracts and measures only the essential parameter (backward-running signal power) that directly indicates coupling efficiency, rather than attempting to measure and control the entire complex field distribution pattern. This simplifies the measurement system while maintaining effectiveness in optimizing power transfer to the cooking item.
Solution Approach 2:
The patent changes the control parameter from complex field distribution patterns to a single measurable parameter (backward signal power). By adjusting the phase position of microwave signals based on this simplified parameter, the system achieves optimal power coupling without requiring complex field monitoring infrastructure.
2Productivity
If impedance adaptation networks with switchable coils and capacitors are used, then power coupling efficiency is improved, but device complexity and loss of time for adaptation increase
Solution Approach 1:
The patent replaces mechanical impedance adaptation networks (with switchable coils and capacitors) with an electronic phase control system. By using phase shifters to adjust the phase position of microwave signals, the system achieves impedance matching and maximum power transfer without requiring complex mechanical adaptation networks.
Solution Approach 2:
The patent changes the adaptation mechanism from adjusting impedance parameters (using coils and capacitors) to adjusting phase parameters. This allows for faster, electronically-controlled adaptation that reduces both device complexity and adaptation time while maintaining high power coupling efficiency.
3Device complexity
If empirical methods with fixed phase differences are used, then device complexity is reduced, but adaptability to different cooking conditions and power coupling efficiency deteriorate
Solution Approach 1:
The patent introduces a feedback mechanism where the measured backward-running signal power is used to dynamically adjust the phase position of microwave signals. This closed-loop control enables the system to adapt to different cooking conditions (different items, positions, and configurations) while maintaining simple device architecture, resolving the contradiction between simplicity and adaptability.
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 approach maximizes the power coupled into the cooking item by using easily accessible and inexpensive electronic components, ensuring reliable and efficient cooking by dynamically adapting to the specific cooking conditions, avoiding the inefficiencies of empirical methods that rely solely on backward signal measurements.
Implementation Method 1
microwave radiation for cooking food can be generated in that a high-frequency signal or microwave signal provided by a microwave generator is amplified by a semiconductor amplifier
Implementation Method 2
The phase position of the microwave radiation from the two antennas relative to one another is controlled in such a way that the power of the backward-running microwave signal is minimized
Implementation Method 3
a backward running microwave signal, which was coupled from the cooking chamber into the antenna, is detected
Data Source
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AI summary
The invention relates to a method for controlling a microwave oven (10) comprising the following steps: Microwave radiation, originating from a semiconductor amplifier (26, 28) and radiated by the antennas (22, 24) into a cooking chamber (12) of the oven (10), is supplied to a first antenna (22) and at least one second antenna (24). A reverse-propagating microwave signal, coupled from the cooking chamber (12) into the antenna (22, 24), is detected. The phase relationship of the microwave radiation of the two antennas (22, 24) relative to each other is controlled such that the power of the reverse-propagating microwave signal is minimized. The invention also relates to an oven (10).