Microwave Feeding System Elliptical Polarization
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Solution Overview
Problem
Current microwave feeding systems for ovens suffer from low power efficiency, with significant power loss due to reflection and heating of the magnetron's outer body, resulting in power consumption efficiency of only 50% to 55%, and inadequate microwave distribution within the oven cavity.
Innovation Solution
The microwave feeding system connects a magnetron, rectangular waveguide, and cylindrical cavity in series, using an omnidirectional antenna as a continuous phase shifter to generate elliptically polarized TEM waves, optimizing power transfer to the oven cavity with improved electromagnetic field uniformity and density, and incorporating a Chebyshev waveguide transformer and choke filter for enhanced energy transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional microwave feeding system with a magnetron, rectangular waveguide, and cylindrical cavity is used, then the structure is simple and easy to manufacture, but the power efficiency is low (not more than 55%) due to power reflection and magnetron body heating
Solution Approach 1:
The patent changes the electromagnetic wave parameters by introducing an omnidirectional antenna that generates elliptically polarized TEM waves instead of conventional linearly polarized waves. This parameter change in wave polarization and type improves power transfer efficiency to above 80% by better matching the impedance between the magnetron and oven cavity, reducing power reflection and magnetron body heating.
Solution Approach 2:
The patent introduces a Chebyshev waveguide transformer as an intermediary component between the rectangular waveguide and the oven cavity. This transformer acts as an impedance matching device that facilitates more efficient power transfer, contributing to the improvement of power efficiency from 55% to above 80% while maintaining a manageable system structure.
2Ease of operation
If a wave stirrer is used to shift the phase of electromagnetic waves, then the phase can be changed, but the microwave distribution in the oven cavity is not substantially improved due to big impedance variation between the magnetron antenna and oven cavity
Solution Approach 1:
The patent fundamentally changes the wave type from conventional TE/TM modes to elliptically polarized TEM waves using an omnidirectional antenna. This parameter change in electromagnetic wave characteristics enables effective impedance matching across the system, improving both microwave distribution uniformity and power efficiency simultaneously, achieving above 80% power efficiency.
Solution Approach 2:
The omnidirectional antenna provides continuous phase shifting capability, making the system dynamic rather than static. This dynamic phase adjustment ability allows the system to adapt to impedance variations and optimize microwave distribution throughout the oven cavity, resolving the contradiction between ease of operation and energy loss.
3Ease of operation
If only linearly polarized TE and TM electromagnetic waves are generated, then the wave generation is simple, but a standing wave picture is created in the oven cavity resulting in poor power distribution
Solution Approach 1:
The patent changes the polarization parameter from linear (TE/TM) to elliptical polarization using an omnidirectional antenna. This parameter change eliminates the standing wave picture problem by creating a more uniform electromagnetic field distribution in the oven cavity, achieving both simple operation and improved power distribution without requiring complex additional components.
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 configuration increases energy transfer to the oven cavity, achieving over 80% efficiency of real power absorption by the load relative to the magnetron's power delivery and reducing overall power consumption to about 60% of the main power supply, while improving microwave field distribution.
Implementation Method 1
the omnidirectional antenna acts as a continuous phase shifter, so that the microwave feeding system provides elliptically polarized TEM electromagnetic waves for the oven cavity
Implementation Method 2
a substantial amount of the power delivered by a magnetron is lost by reflecting phenomenon and by heating of the outside body of said magnetron
Implementation Method 3
A Chebyshev waveguide transformer (16) is connected to said rectangular waveguide (14) and arranged opposite to said magnetron (12)
Implementation Method 4
wherein an inner diameter of the cylindrical cavity is between 0.75 and three multiples of the wavelength of the microwaves guided within said cylindrical cavity
Implementation Method 5
The wave stirrer 34 shifts the phase of the electromagnetic waves, but this is not sufficient for improving the microwave distribution
Implementation Method 6
The blades of the wave stirrer 34 reflect a part of the microwave energy back to the antenna of the magnetron 12, so that an outer body of said magnetron 12 is heated up
Data Source
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AI summary
A microwave feeding system (10) for a microwave oven or an oven with microwave heating function, wherein the microwave feeding system (10) comprises a magnetron (12), a rectangular waveguide (14) and a cylindrical cavity (18), the cylindrical cavity (18) is connected or connectable to an oven cavity (20), a rotatable omnidirectional antenna (22) is arranged inside the cylindrical cavity (18), the omnidirectional antenna (22) is driven by an antenna motor (24), the omnidirectional antenna (22) is connected to the antenna motor (24) via a shaft (30) made of conductive material, an inner cavity (26) is arranged inside the cylindrical cavity (18), the inner cavity (26) is arranged coaxially to the cylindrical cavity (18), the inner cavity (26) en- closes at least partially the shaft (30), and the inner cavity (26) and the shaft (30) are arranged coaxially to each other, characterised in that the magnetron (12), the rectangular waveguide (14) and the cylindrical cavity (18) are connected in straight series, wherein the microwave feeding system (10) provides elliptically polarized TEM electromagnetic waves for the oven cavity (20), and wherein the omnidirectional antenna (22) acts as a continuous phase shifter, and wherein an inner diameter of the cylindrical cavity (18) is between 0.75 and three multiples of the wave- length of the microwaves guided within said cylindrical cavity (18).