ANTENNA STRUCTURE FOR MOTION METAL DETECTOR WITH NON-COPLANAR COILS AND INDUCTION BALANCE

Abstract

The invention relates to an antenna structure for a motion metal detector, comprising an antenna body, at least one receiving coil, and one transmitting coil. One of the main objectives of this invention is to provide an antenna structure capable of maintaining a stable induction balance while being less sensitive to shocks inherent in its field use. To this end, the inventor proposes an innovative configuration of the coils, which are arranged with respect to a reference plane so as to receive or transmit signals of opposite directions in a central portion 113. In particular, the arrangement of the central portion of the antenna structure is designed so that, in response to a shock, the signals received or transmitted in the central portion 113 tend to cancel each other out, while maintaining the induction balance. Figure to be published with the abstract: Figure 1

Description

Title of the invention: ANTENNA STRUCTURE FOR MOTION METAL DETECTOR WITH NON-COPLANAR INDUCTION BALANCE COILS technical field

[0001] The invention relates to the field of antenna structures for motion metal detectors used for searching for metallic objects buried in the ground.

[0002] In particular, it relates to the antenna structures used in these detectors. Previous technique

[0003] Motion metal detectors are widely used in various applications, including searching for buried metal objects, archaeology, security, and recreation.

[0004] These detectors are based on the principle of electromagnetic induction to detect the presence of metals in the soil or in other media.

[0005] It is known that motion and metal discrimination metal detectors generally use antenna structures which include transmit and receive coils to detect metallic objects in the ground.

[0006] These antenna structures are designed to be held and maneuvered by a user when searching for targets.

[0007] When the user moves the detector, shocks to the detection disc can cause relative displacements between the transmitting and receiving coils.

[0008] These movements, even minimal ones, disrupt detection and generate spurious signals, thus reducing the accuracy and reliability of the detector.

[0009] Usually, these transmitting and receiving coils are positioned in induction balance, that is to say that the receiving coil overlaps the transmitting coil so that the electromagnetic signal received by the receiving coil from the transmitting coil is zero or substantially close to zero.

[0010] Traditionally, some of these transmitting and receiving coils are arranged non-coplanarly, with one of the coils inclined relative to the other. This arrangement helps to compensate for the effects of shocks and vibrations on the detector, although this method has limitations in terms of efficiency.

[0011] An alternative configuration consists of arranging the transmitting and receiving coils coplanarly or close to coplanarly in an antenna body, generally in a plane parallel to the ground, in order to compensate for shocks, but also presents constraints in terms of efficiency.

[0012] This coplanar configuration makes it possible to limit the sensitivity of the coils to deformations during shocks or movements of the latter, because the electromagnetic field generated by the transmitting coil varies little in its plane.

[0013] However, existing antenna structures are generally not designed to sufficiently compensate for shock effects, which can lead to false detections or reduced performance under difficult operating conditions.

[0014] Thus, there is a need for a motion metal detector antenna structure that can maintain a stable induction balance while being less sensitive to shocks inherent in its use in the field. Summary of the invention

[0015] The invention aims to solve, at least partially, this need.

[0016] In practice, the invention relates to an antenna structure for a motion metal detector.

[0017] In particular, the antenna structure comprises, - an antenna body that is designed with respect to a user holding and maneuvering the motion metal detector to detect a target in the ground, - at least one receiving coil and at least one transmitting coil, and - a reference plane that is parallel to the ground and that horizontally cuts the antenna body into an upper and a lower part.

[0018] More specifically, the antenna body comprises, - side parts, - front-rear parts, and - a central part which is located between the side parts and the front-rear parts.

[0019] In addition, the transmitting coil and the receiving coil, - are arranged in the antenna body, - each comprise multiple turns of conductors, - partially overlap in the central part, and - are positioned to create an induction balance.

[0020] Furthermore, in a section perpendicular to the reference plane that intersects the central part where the transmitting and receiving coils partially overlap, called the overlap section, the central part is arranged such that at least one of the coils, either the transmitting coil or the receiving coil, is configured non-coplanarly with respect to the reference plane, with positions at different heights relative to the reference plane, such that at least one coil is above or below the reference plane, creating at least one vertical offset, D, between the coils, the vertical offsets, D, being designed to allow the central part to receive or emit signals in opposite directions, so that, in response to a shock which causes a displacement substantially in the same direction of all or part of the receiving coil and / or the transmitting coil, the signals received or emitted in the central part tend to cancel each other out, while maintaining the induction balance.

[0021] In a first embodiment of the invention, the perimeter of the central part corresponds to at least 20% of the total perimeter of the antenna body.

[0022] In a second embodiment of the invention, in the central part, - the transmitting coil and the receiving coil are both configured non-coplanarly with respect to the reference plane, and - the transmitting coil and the receiving coil are oriented in a complementary manner, so that when the receiving coil extends above the reference plane, the transmitting coil extends below the reference plane, and vice versa.

[0023] In a third embodiment of the invention, the vertical offsets, D, are distributed uniformly along the central part or variably distributed along the central part.

[0024] In a fourth embodiment of the invention, the antenna structure further comprises mechanical stiffening elements arranged in the central part which are designed to maintain the vertical offsets, D, between the coils when shocks are applied.

[0025] In a fifth embodiment of the invention, the transmitting and receiving coils are arranged according to a three-dimensional configuration chosen from, - an angular offset between the principal planes of the coils, - a variation in the spacing between the coils along their perimeter, and - a relative inclination of the coils with respect to the reference plane. Brief description of the drawings

[0026] Other features and advantages of the invention will be better understood from the following description and with reference to the accompanying drawings, given by way of illustration and not limitation.

[0027] [Fig-1] Fig. 1 represents a first perspective view of the structure antenna according to the invention.

[0028] [Fig.2] Fig.2 represents a second perspective view of the structure antenna according to the invention.

[0029] [Fig.3] Fig.3 represents a third perspective view of the structure antenna according to the invention.

[0030] [Fig.4] Fig.4 represents a top view of the antenna structure according to the invention.

[0031] [Fig. 5] Fig. 5 represents a first view of the overlap section along the invention.

[0032] [Fig.6] Fig.6 represents a second view of the overlap section along the invention.

[0033] The figures do not necessarily respect the scales, particularly in thickness, for illustrative purposes.

[0034] Furthermore, some drawings are shown in transparency, as their representation in black and white is impossible. In particular, colors are necessary in these drawings to discern details that would be lost if they were shown in black and white. Description of the implementation methods

[0035] Preliminary remarks

[0036] In order not to obscure the description and distract the reader from understanding the teachings of the invention, our explanations will not go beyond what is considered necessary for understanding and appreciating the underlying concepts of the invention. Indeed, the embodiments illustrated in the description are, for the most part, composed of elements known to a person skilled in the art.

[0037] Objective of the invention

[0038] One of the main objectives of the invention is to provide an antenna structure for motion metal detectors that maintains a stable induction balance while being less sensitive to shocks inherent in its use in the field.

[0039] To achieve this, the inventors propose an innovative configuration of the transmitting and receiving coils, which are arranged with respect to a reference plane so as to capture or emit signals of opposite directions in a central part of the antenna structure.

[0040] In particular, the arrangement of the central part of the antenna structure aims to mutually cancel the unwanted signals generated by shocks, while preserving the induction balance essential to the sensitivity of the detector.

[0041] This approach aims to significantly improve the accuracy and reliability of motion metal detectors, even under difficult operating conditions on rough terrain.

[0042] General structure of the invention

[0043] As illustrated in [Fig. 1], [Fig. 2], [Fig. 3] and [Fig. 4], the antenna structure 100 for a motion metal detector comprises several components: a body antenna 110, at least one receiving coil 120, at least one transmitting coil 130 and a reference plane 140.

[0044] The term "antenna structure" refers to a set of elements that form the antenna of a portable device used to detect metallic objects buried in the ground.

[0045] In the invention, the antenna body 110 is designed with respect to a user who holds and maneuvers the motion metal detector to detect a target in the ground, namely metallic objects such as ancient coins, buried jewelry, historical relics, or metallic debris.

[0046] The term "antenna body" refers to the main part of the antenna structure 100 which supports and contains the other components.

[0047] In the example of [Fig. 1], the antenna body 110 is arranged in a housing 10.

[0048] In the invention, as illustrated in [Fig.5] and [Fig.6], a reference plane 140 which is parallel to the ground cuts horizontally the antenna body 110 into an upper part and a lower part.

[0049] The term "reference plane" indicates an imaginary plane used as a reference frame to define the position of the other elements of the antenna structure 100. It therefore serves as a reference frame to describe the geometric configuration of the coils 120, 130 and their relative positions.

[0050] In practice, as illustrated in [Fig. 1], the antenna body 110 comprises several elements: side parts 111, front-rear parts 112 and a central part 113.

[0051] The term "lateral parts" refers to the sides of the antenna body 110.

[0052] The term "front-rear parts" refers to the front and rear sections of the body antenna 110.

[0053] The term "central part" corresponds to the area located in the middle of the antenna body 110 and which is located between the lateral parts 111 and the front-rear parts 112.

[0054] In other words, the antenna body 110 has a three-dimensional structure with distinct parts, each of which plays a specific role in the overall configuration of the antenna structure 100.

[0055] The general shape of the antenna body 110 may vary, but it is generally designed to optimize ground coverage while remaining ergonomic for the user. Common shapes include circular, elliptical, or DD-shaped ("Double D") configurations.

[0056] In the invention, the transmitting coil 130 and the receiving coil 120 have several common characteristics.

[0057] The term "transmitting coil" refers to a winding of conductive wire that generates an electromagnetic field, while the term "receiving coil" refers to a winding of conductive wire that captures variations in the electromagnetic field.

[0058] In the invention, as illustrated in [Fig.1], the transmitting coil 130 and the receiving coil 120 are arranged in the antenna body 110, that is to say inside the antenna body 110.

[0059] In addition, the transmitting coil 130 and the receiving coil 120 each comprise multiple turns of conductors, thus forming multiturn coils.

[0060] The term "conductor turns" indicates the turns of wire that form each coil 120, 130.

[0061] The exact number of turns may vary depending on the performance specifications required for the metal detector. These turns may be made of copper wire or any other suitable conductive material.

[0062] In the invention, as illustrated in [Fig.1], [Fig.2], [Fig.3] and [Fig.4], [Fig.5] and [Fig.6], the transmitting coil 130 and the receiving coil 120 partially overlap in the central part 113.

[0063] The term "partially overlap" refers to the spatial configuration in which the transmitting coil 130 and the receiving coil 120 occupy a common space in an incomplete or limited way within the central part 113 of the antenna structure.

[0064] This arrangement involves a partial superposition of the two coils, allowing a specific electromagnetic interaction within the central part 113.

[0065] In practice, this overlap can occur in both directions, that is to say that the transmitting coil 130 can overlap the receiving coil 120 or conversely, the receiving coil 120 can overlap the transmitting coil 130.

[0066] Furthermore, in the invention, the transmitting coil 130 and the receiving coil 120 are designed and positioned so as to create an induction balance.

[0067] The term "induction balance" refers to the state in which the transmitting coil 130 and the receiving coil 120 are positioned so as to balance the electromagnetic forces received by the receiving coil 120, thus optimizing the detection sensitivity.

[0068] This induction balance is achieved through various techniques, including the precise adjustment of the relative positions of coils 120 and 130, the optimization of the number of turns in each coil, and possibly the use of electronic compensation circuits. These methods aim to maintain a zero or at least minimal signal in the receiving coil 120, thereby ensuring the sensitivity of the metal detector by facilitating signal amplification.

[0069] To establish this balance, a reference point is necessary. For example, "0V" is often used as a reference for the balance of electromagnetic forces. s. In this case, it corresponds to the state where, in the absence of a metallic target, the magnetic field induced in the receiving coil by the transmitting coil is perfectly compensated, resulting in a zero output voltage (0 Volt) at the receiving circuit.

[0070] In other words, the configuration of the transmitting coils 130 and receiving coils 120 is optimized to maximize the detection efficiency of the antenna structure 100.

[0071] In particular, the partial overlap of the coils 120, 130 in the central part 113 leading to an induction balance makes it possible to obtain a more sensitive detection area and to improve the detection accuracy.

[0072] In the invention, the central part 113 has a particular configuration in a specific section.

[0073] The term "section" refers to a specific cross-section of the central part 113.

[0074] In particular, this section is perpendicular to the reference plane 140 and intersects the central part 113. This section, illustrated in [Fig.5] and [Fig.6], is called the overlap section 150.

[0075] In practice, in the overlap section 150, the central part 113 plays an important role in the operation of the antenna structure 100, as it optimizes the interaction between the emitted electromagnetic field and the received signals, thus improving the detection capability of metallic objects buried in the ground.

[0076] For this purpose, in the central part 113, the transmitting coil 130 and the receiving coil 120 together have a specific configuration.

[0077] In particular, as illustrated in [Fig.5] and [Fig.6], in the central part 113, at least one of the coils 120, 130 is configured in a non-coplanar manner with respect to the reference plane 140.

[0078] The term "non-coplanar" for a coil 120, 130 indicates that it is not located on the same plane parallel to the reference plane 140.

[0079] Thus, the coils 120, 130 can have positions at different heights relative to the reference plane 140.

[0080] In other words, this non-coplanar configuration of at least one of the coils 120, 130 creates a complex three-dimensional geometry within the central part 113, so as to optimize detection sensitivity and reduce potential interference.

[0081] In practice, the configuration of the central part 113 is such that at least one coil 120, 130 is located above or below the reference plane 140.

[0082] As illustrated in [Fig.2], [Fig.3], [Fig.5] and [Fig.6], this configuration creates at least one vertical offset D between coils 120, 130.

[0083] The term "vertical offsets" refers to; in the overlap section 150, the height differences between the coils 120, 130 which are measured relative, perpendicularly, to the reference plane 140, in the central part 113.

[0084] Thus, this arrangement of the coils 120, 130 with respect to the reference plane 140, in the overlap section 150, makes it possible to obtain an optimal spatial distribution of the electromagnetic fields within the central part 113. This configuration contributes to improving the accuracy and sensitivity of the detection of metallic objects in the ground.

[0085] In the invention, the vertical offsets D are designed for a specific purpose.

[0086] In particular, in the overlap section 150, the vertical offsets D allow the central part 113 to capture or emit signals in opposite directions.

[0087] The term "opposite-sense signals" refers to electromagnetic signals that have polarities or phases opposite to each other, or to induced currents that flow in opposite directions.

[0088] In practice, this configuration with signals in opposite directions plays an important role in reducing interference related to shocks.

[0089] The term "shock" here refers to a sudden or repeated impact or vibration that affects the antenna structure 100.

[0090] The physical basis of this arrangement, which allows for the capture or transmission of signals in opposite directions in different areas of the antenna, rests on the principle of electromagnetic induction and Lenz's law. Indeed, when a changing magnetic field passes through a conducting loop, it induces a current in that loop. And, the direction of this induced current depends on the orientation of the loop relative to the magnetic field.

[0091] In the context of the overlapping section 150, the coils 120, 130 in the central part 113 are oriented differently with respect to the emitted or received magnetic field. Consequently, the currents induced in each of the coils 120, 130 have opposite directions, resulting in signals of opposite sense.

[0092] In the invention, this configuration has a particular effect in the event of a shock.

[0093] Indeed, in response to a shock which causes a displacement substantially in the same direction of all or part of the receiving coil 120 and / or the transmitting coil 130, the signals captured or emitted in the central part 113 tend to cancel each other out.

[0094] This mutual cancellation of signals makes it possible to avoid, or at least limit, variations in the induction balance, even in the presence of shocks or vibrations. This represents a significant improvement compared to conventional antenna structures, which are often sensitive to mechanical disturbances.

[0095] The term "same direction" refers to the substantially identical spatial orientation in which all or part of the receiving coil 120 and / or the transmitting coil 130 move in response to a shock. This concept implies that the elements concerned follow parallel or coincident trajectories, without necessarily having the same direction of movement.

[0096] In other words, this particular configuration of the antenna structure 100 offers a form of self-compensation in the event of mechanical disturbances. This makes it possible to reduce false signals that could be generated by sudden movements or shocks during the use of the detector, thus improving the reliability and accuracy of detections under various operating conditions.

[0097] Operation of the invention

[0098] The antenna structure 100 operates according to a principle of electromagnetic induction.

[0099] First, the transmitting coil 130 generates an electromagnetic field which penetrates the ground.

[0100] Then, when a metallic object is present, it disturbs this field.

[0101] In response, the receiving coil 120 detects these disturbances and variations in the field, thus enabling the object to be located.

[0102] In the invention, the configuration of the coils 120, 130 in the central part 113, combined with the vertical offsets D, makes it possible to optimize detection while reducing interference.

[0103] Indeed, in the event of a shock or sudden movement, the opposing signals generated in the central part 113 tend to cancel each other out, thus minimizing false positives.

[0104] First embodiment: minimum proportion of the central part 113

[0105] In a first embodiment of the antenna structure 100, the perimeter of the central part 113 corresponds to at least 20% of the total perimeter of the antenna body 110.

[0106] The term "perimeter of the central part 113" refers to the length of the line that delimits the contour of the central part 113, while the term "total perimeter" refers to the total length of the line that delimits the antenna body 110.

[0107] Second embodiment: complementary non-coplanar configuration of the transmitting and receiving coils

[0108] In a second embodiment of the antenna structure 100, as illustrated in [Fig.3], the transmitting coil 130 and the receiving coil 120 are both configured in a non-coplanar manner with respect to the reference plane 140.

[0109] In addition, in the central part 113, the transmitting coil 130 and the receiving coil 120 are oriented in a complementary manner.

[0110] The term "oriented in a complementary manner" means that the coils 120, 130 are arranged so as to complement each other in their positioning with respect to the reference plane 140.

[0111] This complementary orientation, in the central part 113, is manifested in the following way: when the receiving coil 120 extends above the reference plane 140, the transmitting coil 130 extends below the reference plane 140, and vice versa.

[0112] In other words, this particular configuration of the coils 120, 130 in the central part 113 creates an alternating arrangement of the coils 120, 130 with respect to the reference plane 140.

[0113] This alternating arrangement optimizes the interaction between the emitted and received electromagnetic fields and helps to mitigate electromagnetic disturbances induced by sudden movements, thus significantly reducing spurious signals due to shocks.

[0114] Third embodiment: uniformity or variability of vertical offsets

[0115] In a third embodiment of the antenna structure 100, the vertical offsets D can have two types of distribution along the central part 113: a uniform distribution or a variable distribution.

[0116] In the case of a uniform distribution, the vertical offsets D between the coils 120, 130 maintain the same value over the entire length of the central part 113.

[0117] By way of example, the term "uniform vertical offsets" may refer to constant height differences of 5 mm between the coils 120, 130 along the central part 113.

[0118] In the case of a variable distribution, the vertical offsets D between the coils 120, 130 change in value along the central part 113.

[0119] For example, the term "variable vertical offsets D" may also include height deviations that gradually increase from 2 mm to 10 mm from the center of the central part 113 towards the extremities of the central part 113, or an alternation of large and small deviations along the central part 113.

[0120] In other words, this configuration of the vertical offsets D in the antenna structure 100 optimizes the spatial distribution of the electromagnetic fields. The uniform or variable distribution of the vertical offsets D provides flexibility in the antenna design to adapt the compensation of shock effects, thus optimizing detector performance under various operating conditions.

[0121] Fourth embodiment: mechanical stiffening elements

[0122] In a fourth embodiment of the antenna structure 100, the latter includes mechanical stiffening elements, namely structural components designed to reinforce and stabilize the antenna structure 100.

[0123] In practice, the mechanical stiffening elements are arranged in the central part 113.

[0124] In particular, the mechanical stiffening elements fulfill the function of maintaining the vertical offsets D between the coils 120, 130, when shocks are applied.

[0125] By way of example, the mechanical stiffening elements may include composite material reinforcements, honeycomb structures, support ribs, or supports specially designed to fit the shape of the coils 120, 130 in the central part 113.

[0126] These elements could be made of lightweight but strong materials, such as fiber-reinforced polymers, so as not to excessively burden the antenna structure 100 while ensuring its rigidity.

[0127] Fifth embodiment: advanced three-dimensional configurations of the coils

[0128] In a fifth embodiment of the antenna structure 100, the transmitting coils 130 and receiving coils 120 are arranged according to a three-dimensional configuration chosen from three options: an angular offset between the principal planes of the coils 120, 130, a variation of the spacing between the coils 120, 130 along their perimeter, and a relative inclination of the coils 120, 130 with respect to the reference plane 140.

[0129] The term "angular offset" refers to an arrangement where the planes containing the transmitting coils 130 and receiving coils 120 form an angle with each other.

[0130] By way of example, the angular offset between the main planes of the coils 120, 130 could be 15°, 30° or 45°.

[0131] This configuration optimizes the interaction between the emitted and received electromagnetic fields, thus improving the performance of the antenna structure 100.

[0132] The "spacing variation" refers to a configuration where the distance between the transmitting coils 130 and receiving coils 120 is not constant around their entire circumference.

[0133] By way of example, the variation of the spacing between the coils 120, 130 along their perimeter could follow a sinusoidal function or a linear progression.

[0134] This variation in spacing can contribute to creating a non-uniform distribution of the electromagnetic field, allowing the detection sensitivity to be adapted according to the specific needs of the application.

[0135] The relative inclination of the coils 120, 130 with respect to the reference plane 140 indicates that the transmitting coils 130 and receiving coils 120 are not necessarily parallel to the reference plane 140.

[0136] By way of example, the relative inclination of the coils 120, 130 with respect to the reference plane 140 could be 5°, 10° or 20°, depending on the specific requirements of the application.

[0137] This inclination can modify the main direction of the electromagnetic field generated and captured by the antenna structure 100, thus offering additional flexibility in the design of the motion metal detector.

[0138] In other words, these three-dimensional configurations of the transmitting coil 130 and receiving coil 120 in the antenna structure 100 optimize the spatial distribution of the electromagnetic fields. These arrangements can improve detection sensitivity, antenna directivity, or its ability to adapt to different operating conditions.

[0139] Conclusion

[0140] We have described and illustrated the invention. However, the invention is not limited to the embodiments we have presented. Indeed, numerous combinations of variants, alternatives, embodiments, and implementations can be envisaged without requiring substantial modifications to the invention. Thus, an expert in the field can deduce other variants, alternatives, embodiments, and implementations by reading the description and the accompanying figures, and taking into account the economic, ergonomic, and dimensional constraints to be respected.

[0141] In particular, when an expression uses the term "at least one", this means that the element or feature in question may be present in a single occurrence or in multiple occurrences, thus comprising one, two, three or more elements or features, without any upper limit specified.

[0142] On the other hand, when an element is "designed" to perform a particular function, this means that the element is created specifically for the purpose of performing that particular function.

[0143] However, depending on the needs and resources available, consideration may be given to using an existing element, which will be modified or adapted to fulfill this particular function, without requiring substantial modifications to the invention.

[0144] The invention can be the subject of numerous variations and applications other than those described above. In particular, unless otherwise indicated, the different structural and functional features of each particular implementation described above should not be considered as combined and / or closely and / or inextricably linked to one another, but, on the contrary, as simply juxtapositions. In addition, the structural and / or functional characteristics of the different embodiments described above may be subject, in whole or in part, to any different juxtaposition or any different combination.

Claims

Demands

1. Antenna structure (100) for a motion metal detector, the antenna structure (100) comprising: - an antenna body (110) designed with respect to a user holding and maneuvering the motion metal detector to detect a target in the ground; - at least one receiving coil (120) and at least one transmitting coil (130); and - a reference plane (140) parallel to the ground, horizontally dividing the antenna body (110) into an upper and a lower portion, wherein: - the antenna body (110) has lateral portions (111); - front and rear portions (112); and - a central portion (113) located between the lateral portions (111) and the front and rear portions (112); - the transmitting coil (130) and the receiving coil (120) are arranged in the antenna body (110). — each comprise multiple turns of conductors, — partially overlap in the central part (113),and — are positioned so as to create an induction balance, and wherein, in a section perpendicular to the reference plane (140) that intersects the central portion (113) where the transmitting coils (130) and receiving coils (120) partially overlap, referred to as the overlap section (150), the central portion (113) is arranged such that at least one of the coils (120, 130), either the transmitting coil (130) or the receiving coil (120), is configured non-coplanarly with respect to the reference plane (140), with positions at different heights relative to the reference plane (140), such that at least one coil (120, 130) lies above or below the reference plane (140), creating at least one vertical offset, D, between the coils (120, 130), the vertical offsets, D, being designed to permit to the central part (113) to capture or emit signals in opposite directions, so that,in response to an impact that causes a displacement substantially in the same direction of all or part of the coil, of the receiving coil (120) and / or the transmitting coil (130), the signals captured or emitted in the central part (113) tend to cancel each other out, while maintaining the induction balance.

2. Antenna structure (100) according to claim 1, wherein the perimeter of the central part (113) corresponds to at least 20% of the total perimeter of the antenna body (110).

3. Antenna structure (100) according to any one of claims 1 to 2, wherein, in the central part (113), - the transmitting coil (130) and the receiving coil (120) are both configured in a non-coplanar manner with respect to the reference plane (140), and - the transmitting coil (130) and the receiving coil (120) are oriented in a complementary manner, such that when the receiving coil (120) extends above the reference plane (140), the transmitting coil (130) extends below the reference plane (140), and vice versa.

4. Antenna structure (100) according to any one of claims 1 to 3, wherein the vertical offsets, D, are distributed uniformly along the central part (113) or variably distributed along the central part (113).

5. Antenna structure (100) according to any one of claims 1 to 4, further comprising mechanical stiffening elements disposed in the central part (113) which are designed to maintain the vertical offsets, D, between the coils (120, 130) when shocks are applied.

6. Antenna structure (100) according to any one of claims 1 to 5, wherein the transmitting coils (130) and receiving coils (120) are arranged in a three-dimensional configuration selected from, - an angular offset between the principal planes of the coils (120, 130), - a variation in the spacing between the coils (120, 130) along their perimeter, and - a relative inclination of the coils (120, 130) with respect to the reference plane (140).

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