Solid State RF Oven Calibration Using Modified S-Parameter Measurement
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Solution Overview
Problem
Conventional microwave ovens lack control over RF energy penetration and application, leading to suboptimal cooking results due to indiscriminate energy distribution, and existing calibration methods are inadequate for ovens using solid state RF components.
Innovation Solution
An oven design that employs solid state electronic components for RF heating, featuring a measurement assembly to calculate modified S parameters, allowing for accurate calibration of power amplifier electronics through directional couplers and a calibration manager, enabling precise control over RF energy application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional microwave ovens use magnetron to generate RF energy, then RF heating is achieved, but control over RF energy penetration and application is lost resulting in indiscriminate energy distribution
Solution Approach 1:
The patent replaces the magnetron (electromechanical device) with solid state electronic components including power amplifier electronics. This substitution enables precise electronic control of RF energy generation, allowing accurate measurement and regulation of energy levels applied to the food product, thereby resolving the contradiction between ease of control and measurement precision.
Solution Approach 2:
The patent implements a feedback system using directional couplers to measure forward and reflected power, with these measurements fed back to the control system. This closed-loop feedback enables real-time adjustment of RF energy levels, ensuring both ease of operation and high measurement precision in controlling energy application to the food.
2Measurement precision
If S parameters are measured using conventional two-port network analyzer method, then calibration can be performed, but the open oven cavity prevents identification of ports for closed system measurement
Solution Approach 1:
The patent segments the measurement system into multiple single-port measurement points within the oven cavity, each with its own directional coupler. Instead of requiring a complex two-port measurement system, the cavity is divided into multiple manageable measurement sections, allowing calibration to be performed at each segment independently while maintaining overall system accuracy.
Solution Approach 2:
The patent introduces directional couplers as intermediary devices at each measurement port, which enable the extraction of forward and reflected power measurements without requiring direct access to the RF signal path. These intermediaries facilitate accurate calibration measurements in the open cavity environment by providing isolated measurement points.
3Measurement precision
If directional couplers are installed at port sections of coupling structures, then forward and reflected power can be measured, but device complexity increases
Solution Approach 1:
The patent designs the directional couplers and measurement assembly to serve multiple functions: they measure both forward and reflected power, provide calibration data, and enable real-time monitoring of RF energy levels. This multi-functionality reduces the need for separate measurement devices, thereby limiting the increase in device complexity while maintaining high measurement precision.
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 improves cooking performance by ensuring accurate RF energy levels are applied, resulting in faster and more uniform cooking, enhancing operator experience and cooking quality.
Implementation Method 1
A directional coupler is provided at a port section defined at least one of the first and second coupling structures. The directional coupler is configured to provide a forward power parameter and a reflected power parameter to the measurement assembly.
Implementation Method 2
a radio frequency heating system configured to provide radio frequency energy into the cooking chamber using solid state electronic components
Data Source
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AI summary
An oven includes a cooking chamber configured to receive a load and an RF heating system configured to provide RF energy into the cooking chamber using solid state electronic components. The solid state electronic components include power amplifier electronics configured to provide a signal into the cooking chamber via an antenna assembly. The power amplifier electronics include at least a first power amplifier and a second power amplifier operably coupled to the cooking chamber by respective ones of a first antenna and second antenna of the antenna assembly. The first and second antennas are operably coupled to respective ones of the first and second power amplifiers via a first coupling structure and a second coupling structure, respectively. A directional coupler provided at a port section defined for at least one of the first and second coupling structures. The directional coupler is configured to provide a forward wave parameter and a reflected wave parameter to a measurement assembly configured to calculate modified S parameters at the port section.