Waveguide Matching Structure for Low-Reflection Field Exposure
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Solution Overview
Problem
Existing electromagnetic field exposure devices face challenges in achieving high coupling rates of the electric field in objects with high real relative dielectric permittivity, leading to mismatch issues and the need for oversizing the electromagnetic wave source, which is not satisfactory due to power limitations and compatibility with reflected waves.
Innovation Solution
A device with a heterogeneous adaptation structure that includes an extension element made of material with relative dielectric permittivity close to the object, housed in a tubular conductor or between conductors, ensuring good input adaptation and minimizing insertion losses by adjusting the structure's length to multiples of half-wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the object is brought into contact with electrical conductors to promote electric field coupling, then the coupling rate is improved, but the input reflection coefficient increases (matching deteriorates)
Solution Approach 1:
A matching structure made of dielectric material is introduced as an intermediary between the electrical conductors and the object. This matching structure has a relative dielectric permittivity close to that of the object, enabling gradual impedance transition and reducing reflection while maintaining good electric field coupling. The matching structure acts as a bridge that mediates the impedance mismatch between the conductors and the high-permittivity object.
2Device complexity
If the object is placed in the exposure device without special precautions, then the device complexity is reduced, but the coupling rate and input matching deteriorate
Solution Approach 1:
The matching structure's relative dielectric permittivity is specifically designed to be close to that of the object under test. By adjusting this key parameter (dielectric permittivity), the system achieves optimal impedance matching and electric field coupling without requiring complex additional components. This parameter-based approach simplifies the overall device while improving performance.
3Power
If the power of the electromagnetic wave source is increased to compensate for high reflection, then the electric field level in the object is improved, but the source compatibility and safety deteriorate
Solution Approach 1:
The matching structure is placed in advance at the input of the exposure device to prevent high reflection from occurring. By reducing the reflection coefficient through proper impedance matching, the system allows standard-power electromagnetic wave sources to operate effectively without requiring oversized sources or dealing with high-amplitude reflected waves that could damage equipment or limit source selection.
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
The solution achieves improved coupling and homogeneity of the electric field within the object, reducing reflection coefficients and insertion losses, allowing for efficient exposure with minimal power requirements and compatibility with existing wave sources.
Implementation Method 1
The extension element is made of a material having a relative dielectric permittivity equal to the relative dielectric permittivity of the object(s) to be tested, plus or minus 50%
Implementation Method 2
The heterogeneous matching structure has a dimension, along the longitudinal axis, equal to a non-zero multiple of half-wavelengths of the electromagnetic wave that is to propagate in the electromagnetic field exposure device
Implementation Method 3
a section of a guided electromagnetic wave device, such as a waveguide or transmission line, in which the electromagnetic wave propagates
Data Source
Figure 1~2B
Figure 3A~3B
Figure 4A~4C
AI summary
The invention concerns a device for exposing at least one object (8) to an electromagnetic field, formed from a section of a waveguide or transmission line device (1) having a guided electromagnetic wave, extending along a longitudinal axis (XX'), and having a hollow tubular electrical conductor (81) inside which the electric field is established or several electrical conductors (2.1, 2.2) between which the electric field is established. The device is also formed from a heterogeneous adaptation structure (6) in mechanical contact with the electrical conductor or conductors. The device comprises at least one extension element (9) and at least one housing (7) for the object (8), contained in or positioned next to the extension element (9). The extension element (9) is made from a material having a relative dielectric permittivity (E) as close as possible to that of the or each object (8). The heterogeneous adaptation structure (6) has a dimension (L), along the longitudinal axis, equal to a non-zero multiple of half-wavelengths of the electromagnetic wave to be propagated in the exposure device. Such an exposure device can be used to study the effect of an electromagnetic field in the radio and microwave domains on objects such as biological or chemical objects to be tested and makes it possible, for example, to determine harm and safety thresholds of electromagnetic fields.