US-12625175-B2 - Device for electromagnetic exposure assessment comprising a field enhancing element

US12625175B2US 12625175 B2US12625175 B2US 12625175B2US-12625175-B2

Abstract

A device for measuring a physical quantity related to an electromagnetic field emitted by an electromagnetic source. The device is configured to simulate the electromagnetic characteristics of a reference object made of a lossy medium, e.g. a biological tissue. The device includes: a dielectric layer including an upper surface faced to the electromagnetic source and a bottom surface, the dielectric layer being at least partly transparent to the electromagnetic field emitted by the electromagnetic source; an electromagnetic field enhancing element arranged relative to the dielectric layer and configured in a manner to enhance the intensity of the electromagnetic field transmitted through the dielectric layer in a pre-determined zone; and a sensor arranged beneath the electromagnetic field enhancing element and configured to measure the physical quantity related to the electromagnetic field transmitted through the dielectric layer and the electromagnetic field enhancing element.

Inventors

Maxim ZHADOBOV
Artem BORYSKIN
Ronan Sauleau

Assignees

UNIVERSITE DE RENNES
CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE
INSTITUT NATIONAL DES SCIENCES APPLIQUEES DE RENNES
NANTES UNIVERSITÉ
CENTRALESUPELEC

Dates

Publication Date: 20260512
Application Date: 20221020
Priority Date: 20211022

Claims (16)

1 . A device for measuring a physical quantity related to an electromagnetic (EM) field emitted by an electromagnetic source, the device configured to simulate the EM characteristics of a reference object made of a lossy medium, the device comprising: at least one dielectric layer comprising an upper surface face to the electromagnetic source and a bottom surface, said dielectric layer being at least partly transparent to the EM field emitted by the electromagnetic source; at least one electromagnetic field enhancing element arranged relative to the at least one dielectric layer and configured to enhance the intensity of the electromagnetic field transmitted through the at least one dielectric layer in a pre-determined zone; and at least one sensor arranged beneath the at least one electromagnetic field enhancing element and configured to measure said physical quantity related to the electromagnetic field transmitted through the at least one dielectric layer and the at least one electromagnetic field enhancing element.
2 . The device of claim 1 , wherein the at least one electromagnetic field enhancing element extends from the bottom surface of the at least one dielectric layer towards the at least one sensor.
3 . The device of claim 1 , wherein the at least one electromagnetic field enhancing element is at least partly embedded in the at least one dielectric layer, said at least one dielectric layer having a complex permittivity with absolute value smaller than that of the material of the EM field enhancing element.
4 . The device of claim 3 , comprising at least two dielectric layers, the dielectric layer having a bottom surface face to the sensor comprising a cavity filled with a host medium, the at least one electromagnetic field enhancing element being placed in the cavity, the host medium having a complex permittivity with absolute value smaller than that of the material of the EM field enhancing element.
5 . The device of claim 1 , further comprising at least one electrically conductive layer positioned on the bottom surface of the at least one dielectric layer.
6 . The device of claim 5 , wherein the at least one electrically conductive layer comprises one open cavity, the electromagnetic field enhancing element being placed in the open cavity.
7 . The device of claim 5 , wherein the at least one conductive layer comprising at least one through hole and the size of the at least one through hole being smaller than that of the EM field enhancing element, the EM field enhancing element is positioned on the bottom surface of the conductive layer to cover at least one through hole.
8 . The device of claim 4 , wherein at least one conductive layer comprising at least one through hole and the size of the at least one through hole being smaller than that of the EM field enhancing element, the EM field enhancing element placed in the cavity is aligned with the at least one through hole.
9 . The device of claim 1 , wherein a dimension of the electromagnetic field enhancing element is configured to generate a hot zone, corresponding to an enhancement of the electromagnetic field intensity, in a determined position (Z m ) close to one end of the electromagnetic field enhancing element.
10 . The device of claim 1 , wherein a minimum size of the electromagnetic field enhancing element in a cut plane (X-Y) is equal or greater than a half of a wavelength in the medium of the EM field enhancing element and a maximum size of the electromagnetic field enhancing element in a cut plane (X-Y) is equal or smaller than ten times the wavelength in the medium of the EM field enhancing element.
11 . The device of claim 1 , wherein the at least one sensor is a thermal sensor positioned in direct contact with the at least one electromagnetic field enhancing element or embedded in the at least one electromagnetic field enhancing element.
12 . The device of claim 1 , wherein the at least one sensor is an electromagnetic sensor operating at the frequency of the source.
13 . The device of claim 1 , wherein the at least one sensor is an electromagnetic sensor operating at a frequency different from that of the electromagnetic source.
14 . The device of claim 13 , further comprising a frequency converter in contact with or embedded in one end of the at least one electromagnetic field enhancing element.
15 . The device of claim 1 , comprising a plurality of electromagnetic field enhancing element, each element being configured to cover a complementary portion of the electromagnetic field transmitted through one zone of the surface area of the reference object illuminated by an electromagnetic field emitted by the electromagnetic source, said complementary portion of the electromagnetic field being defined by the illumination conditions.
16 . A system for measuring a dosimetry quantity related to an electromagnetic (EM) field emitted by an electromagnetic source comprising the device of claim 1 , a signal analyzing unit configured to analyze the signal transmitted from the at least one sensor, a processing unit configured to calculate the electromagnetic dosimetry quantities and a memory unit.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is a National Stage of International Application No. PCT/EP2022/079267, having an International Filing Date of 20 Oct. 2022, which designated the United States of America, and which International Application was published under PCT Article 21(2) as WO Publication No. 2023/067091 A1, which claims priority from and the benefit of European Patent Application No. 21306475.1 filed on 22 Oct. 2021, the disclosures of which are incorporated herein by reference in their entireties. BACKGROUND Field The disclosure relates to a device for electromagnetic dosimetry, and more particularly, the present disclosure relates to a device for simulating some of the electromagnetic characteristics of a reference object made of lossy medium, e.g a biological tissue, particularly a human tissue, and measuring the electromagnetic dosimetry quantities induced in the lossy medium by electromagnetic fields emitted by an electromagnetic source. Brief Description of Related Developments With the development of the wireless technology, in particularly in case of cellular phones which are used in contact with the human body, measuring precisely the exposure level of the radiation of the electromagnetic (EM) wave in a human body becomes a critical factor. Various categories of devices reproducing electromagnetic properties of biological tissues, commonly named as “phantoms” for evaluating the exposure of the human body to electromagnetic waves exist: liquid phantoms, semi-solid phantoms, solid phantoms as well as hybrid phantoms. The liquid phantom comprises a plastic part or a solid shell filled with a gel or a liquid having similar EM properties to those of the human biological tissues at the measurement frequency typically provided thanks to a high content of water, like in biological tissues, these devices are generally used in the frequency ranges from 30 MHz to 6 GHz. These devices have several problems: the liquid needs to be changed frequently due to the evaporation and/or the degradation of the dielectric properties of the liquid over time. These devices require special test equipment to support their weight. The use of the such devices at frequencies above 6 GHz is not possible due to the strong absorption of the EM field by water molecules, leading to a very shallow EM field penetration depth and thus insufficient signal-to-noise ratio (SNR) for embedded sensors. Composition of the semi-solid phantoms is similar to the liquid phantom and a jellifying agent is usually used instead of a liquid to retain the shape of the phantom without using a solid shell. Their main drawback is a limited lifetime (typically limited to days or weeks). The solid phantom is a solid piece made of solid dielectric material, like plastic, polymer, ceramic or synthetic rubbers doped with conductive particles such as graphite, carbon, or metal. The main advantage thereof is the reliability and the constancy of the dielectric properties thereof over time. However, these devices are quite complex and costly to manufacture. Furthermore, they also suffer from high EM losses that do not allow the measurement above 6 GHz. For instance, at 60 GHz, the penetration depth of electromagnetic radiation in the human tissues is of the order of 0.5 mm and the absorption of radiation is essentially limited to the superficial layers of the body. This leads to a prohibitively low signal-to-noise ratio (SNR) for any sensor embedded in a phantom reproducing the EM properties of said biological tissue. In addition, recent wireless communication devices have more than one antenna and are able to operate in multiple frequency bands and modes. The use of traditional dosimetry devices has several limitations and drawbacks, among which is the complex and time-consuming compliance testing procedure. In this perspective, due to the specificity of the frequency-dependent interaction between the human body and the wireless devices, leading to lower reflection and simultaneously to stronger EM losses, and the compliance testing of wireless devices of 5G and beyond generations operating at frequencies above 6 GHz, the new dosimetry standards and guidelines are formulated in terms of the transmitted and/or absorbed electromagnetic power density per a given surface area, which is proportional to the EM field intensity, instead of the measurement of the volumetric dosimetric quantities, such as specific absorption rate (SAR). The document WO2017/0173350 and with reference to FIG. 1, proposes a device having characteristic of human tissues while being able to measure electromagnetic waves at frequencies greater than 6 GHz. It comprises one layer of a dielectric material (S), a semitransparent metal shield (MSH) with through holes (OSH) and an array of sensors (SENS) placed below the through holes. The sensors are configured to measure the electromagnetic field emitted by an electromagnetic source (EMS). Although the device proposed