Antenna for in VIVO sensor communication

Abstract

An antenna for communication with an implanted sensor configured to be operative when placed in contact with the skin of a human or animal, or implanted subcutaneously therein to communicate with said implanted sensor. The antenna comprising: a substantially planar dielectric substrate having a first face and a second face; a conductive pattern formed on the first face of the substrate, forming a conductive perimetric trace and extending therefrom to form two adjacent feed terminals proximate to the centre of the first face; a substantially continuous conductive lamina formed on the second face of the substrate, wherein the perimeter of the conductive lamina on the second face is conductively connected with the perimetric trace on the first face; an adhesive layer applied to the first face of the substrate preventing conductive contact with the skin and enabling the attachment of the antenna to the skin of the subject.

Description

[0001] ANTENNA FOR IN VIVO SENSOR COMMUNICATION

[0002] INTRODUCTION AND BACKGROUND TO THE INVENTION

[0003]

[0100] Modern medical practice makes increasing use of radio frequency devices located against the skin to power and / or monitor implanted sensors by emitting and receiving radio signals from a sensor placed against the skin. The monitoring of the functions of internal organs, for example the heart and lungs, is also increasingly used in sports training and fitness exercising.

[0004]

[0101] The present invention relates to an antenna suitable for use with such systems specifically the present invention is an antenna for communication with an implanted sensor. The antenna may be pressed against the skin of the subject or attached to the skin by means of an adhesive layer, or in other applications it may be implanted subcutaneously. In a first implementation the antenna may be fed with radio frequency signals provided by an electronic device and connected by means of a subminiature coaxial cable. In other implementations a radio communication device may be integrated within the antenna.

[0005] BACKGROUND

[0006]

[0102] Cavity-backed slot antennas may be of the order of a half-wavelength long at the operating frequency. The present disclosure may provide that the dimensions of a radiating element and backing cavity may be reduced from the conventional dimensions and / or that the form of the antenna is simplified.

[0007]

[0103] On-body antennas may require the use of an intermediate dielectric layer of low permittivity between the antenna and the body to limit the extent to which the body modifies the impedance characteristics of the antenna (frequently referred to as 'de-tuning'). The antenna that is the subject of thepresent disclosure aims to avoid the use of such an intermediate layer in order to better reduce the level of signals transmitted to or received from radio devices external to the body to which it is attached.

[0008]

[0104] The following papers from the technical literature provide a background to the present disclosure:

[0009] [1] Wonbin Hong, N. Behdad and K. Sarabandi, "Size reduction of cavity-backed slot antennas," in IEEE Transactions on Antennas and Propagation, vol. 54, no. 5, pp. 1461-1466, May 2006, doi: 10.1109 / TAP.2006.874351.

[0010] [2] L. Zou, M. R. Bahmanyar and C. McLeod, "Thin cavity-backed slot antenna for deeply implantable devices," 12th European Conference on Antennas and Propagation (EuCAP 2018), London, UK, 2018, pp. 1-3, doi: 10.1049 / cp.2018.0493.

[0011] [3] H. Li, J. Zhou, L. Kang, Z. Yang and M. Wang, "Optimization design of skin antenna based on Bayesian optimization," 2017 7th IEEE Internationa / Symposium on Microwave, Antenna, Propagation, and EMC Technologies (MAPE), Xi'an, China, 2017, pp. 78-83, doi: 10.1109 / MAPE.2017.8250802.

[0012] [4] S. Agneessens, P. Van Torre, E. Tanghe, G. Vermeeren, W. Joseph, and H. Rogier, "On-Body Wearable Repeater as a Data Link Relay for In - Body Wireless Implants," IEEE Antennas and Wireless Propagation Letters, vol. 11, pp. 1714-1717, 2012.

[0013] BRIEF DESCRIPTION OF THE INVENTION

[0014]

[0105] The antenna which is the subject of the present invention is for communication with an implanted sensor and is configured to communicate with said implanted sensor. The antenna comprises a dielectric substrate havinga first face and a second face. A conductive pattern is formed on the first face, comprising a conductive perimetric trace and extending therefrom to form two adjacent feed terminals proximate to the centre of the first face. The second face is covered by a substantially continuous conductive lamina. The perimeter of the conductive lamina on the second face of the dielectric substrate is conductively connected with the perimetric trace on the first face thereof. Such conductive connection may be provided by means of plated-through holes, known as vias, provided proximate to the perimeter of the dielectric substrate, or by the conductive lamina on the first or second face extending over the edges of the dielectric substrate.

[0015]

[0106] The antenna further comprises a non-conductive adhesive layer covering the first face of the substrate and the conductive pattern thereupon, the function whereof is to prevent conductive contact with the skin and to enable the attachment of the antenna to the skin of the subject. This layer may be in the form of a double-sided adhesive membrane.

[0016]

[0107] When the antenna is placed with its first face against the skin of a human or animal, the conductive pattern thereon forms an antenna radiating energy through the skin into the body. The conductive surface on the second (outer) face, and the conductively connected perimetric trace on the first (inner) face, form an electromagnetic screen, capacitively coupled to the user. This screen suppresses radiation in directions away from the body and directs radiation into the body, at the same time minimising the reception of unwanted signals and radio frequency noise originating from outside the body.

[0017]

[0108] The antenna is suitable for both the transmission and reception of signals. The antenna is configured for communication with and activation of implanted devices such as monitors and sensors.

[0018]

[0109] The faces of the antenna may be of many forms, for example circular, elliptical or rectangular.

[0110] Some implementations of the invention may be suitable for subcutaneous implantation.

[0019]

[0111] In a practical embodiment of the present invention the cavity depth is less than 1% of the free space wavelength while providing a return loss exceeding 6 dB over a relative bandwidth exceeding 2.5:1.

[0020]

[0112] In the following description the human or animal to which the antenna is applied is referred to as the user.

[0021] 4 BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which:

[0023]

[0113] FIGURE 1 shows a view of the first face of an antenna configured according to the present invention wherein a radio frequency transmission line in the form of a coaxial cable is connected to two terminals of the antenna;

[0024]

[0114] FIGURE 2 is an isometric view showing the conductive surface forming the second face and the edge of an antenna configured according to the present invention;

[0025]

[0115] FIGURE 3 shows details of the trace and coaxial feeder cable on the first face of the antenna;

[0026]

[0116] FIGURE 4 shows an embodiment of the invention wherein a coaxial feed cable is accommodated in a recess in the supporting dielectric substrate;

[0027]

[0117] FIGURE 5 shows a further embodiment wherein the perimeter of the conductive pattern extending inwards on the first surface of the antenna is indented, thereby modifying the operating frequency band and impedance characteristics of the antenna;

[0118] FIGURE 6 shows an embodiment of the invention wherein the curved edges defining the perimeter of the first and second faces of an antenna embodying the present invention are blended to form a continuous curved external surface; and

[0028]

[0119] FIGURE 7 shows an embodiment of the present invention wherein the supporting dielectric is curved to avoid edges or corners which may cause discomfort to the user.

[0029] 5 DETAILED DESCRIPTION OF THE INVENTION

[0030]

[0120] FIGURE 1 shows an embodiment 10 of the invention wherein planar conductive elements, also known as traces, are formed on a first face of a substantially planar dielectric substrate 11. The conductive elements comprise a first conductive element 12 extending around the perimeter of the said face, elements 13 and 14 extending inwardly from the perimetric trace 12 to feed arrangements 15 further shown in FIGURE 3. The feed arrangements 15 may be positioned close to the centre of the substrate 11 as shown in Figure 1 or in some embodiments may be offset therefrom.

[0031]

[0121] FIGURE 2 is a view of the invention showing the second face covered by conductive lamina 17, wherein edge 18 is provided with a conductive surface conductively connected to both the face 17 and to the perimetric conductive trace 12 on the first face.

[0032]

[0122] In some embodiments, for example where the substrate 11 is a flexible or conformable substrate, the conductive surfaces on the first face and / or the second face may be provided with a pattern of slots or other features to increase their flexibility.

[0033]

[0123] FIGURE 3 shows an example of a feed arrangement wherein a connecting coaxial cable 20, is provided with a coaxial connector 21. The outer conductor22 of the coaxial cable 20 is conductively connected to the conductors formed on the first face of the dielectric substrate 11 at position 23 proximate to the inner edge of conductive element 14 and preferably also at position 24 proximate to the circumference of the said substrate.

[0034]

[0124] A conductive element 26 is provided between the proximate ends of conductive elements 13 and 14 to enable an impedance matching component 27, typically a capacitor, to be connected in series between the inner conductor 25 of coaxial cable 20 and the proximate edge of conductive element 13. The conductive connections may be provided by soldering.

[0035]

[0125] It will be apparent to those skilled in the art that the impedance matching arrangement could be modified to include additional components configured in series and / or in parallel.

[0036]

[0126] FIGURE 4 is an exploded view showing an antenna 10 according to a further embodiment of the invention comprising dielectric substrate 11 on which are formed conductive elements 12, 13 and 14 on the first face, edge and second face respectively. A recess 30 is provided on the second face of the dielectric substrate 11. The conductive elements and feed arrangements 18 are shaped in the same manner as shown in FIGURE 3, but are formed on a thin dielectric film 31 such as copper-coated polyimide film.

[0037]

[0127] On assembly of the antenna, dielectric lamina 31 is adhesively attached to substrate 11, preferably by means of double-sided adhesive tape 32. It will be understood that in this arrangement the perimetric conductors 12 on the substrate 11 and on the dielectric lamina 31 will not be in conductive contact, but will be separated from one another only by the thickness of the double sided adhesive tape 32, resulting an effective capacitive connection between them at radio frequencies.

[0128] A layer of double sided adhesive tape 33 is positioned on the exposed face of film 31. Protective layer 34 on the outer face of tape 33 is left in position when the antenna is assembled and is not removed until the antenna is attached to the skin of a subject. Double sided adhesive tape 33 is preferably selected to have a high strength adhesive on a first face and an adhesive suitable for application to the skin of the user on a second face, for example 3M 2477P tape.

[0038]

[0129] In embodiments intended for subcutaneous implantation adhesive tape 33 may be a single-sided tape with a non-adhesive external face or the tape 33 may be omitted and the antenna may be coated with medical grade conformal coating.

[0039]

[0130] In some embodiments a series matching capacitor at the point of connection of the inner conductor of the connecting cable may be formed by overlapping conductive areas on the two faces of the supporting film 31.

[0040]

[0131] FIGURE 5 shows a further embodiment of the invention in which the edges of conductive elements 13 and 14 are meandered.

[0041]

[0132] FIGURE 6 shows an edge view of an embodiment of the invention wherein the substrate 11a is provided with a rounded external perimeter.

[0042]

[0133] FIGURE 7 shows an embodiment of the invention wherein the dielectric substrate 11 b is non-planar; it will be understood that curvature may be applied in one plane or in two planes. A non-planar form may be provided for a rigid substrate or for a flexible substrate.

[0043]

[0134] FIGURE 8 shows the measured return loss over the frequency range 0.7 GHz-2.0 GHz of an antenna configured according to the present invention on a polystyrene foam substrate with diameter 38 mm and thickness 3 mm, with conductive elements 13, 14 having sectoral forms each subtending an angle of approximately 90 degrees. The measurements were made with the antennaadhesively affixed to the chest of the user by means of a medical grade doublesided adhesive tape.

[0044]

[0135] The angular width of conductive elements 13 and 14 may be approximately 90 degrees as illustrated in the accompanying figures, but other angles may be chosen by design.

[0045]

[0136] In some embodiments conductive elements 13 and 14 may be of sectoral form as illustrated in the accompanying figures; in other embodiments conductive elements 13 and 14 may have substantially rectangular, linear or meandered shapes.

[0046]

[0137] In some embodiments conductive elements 13 and 14 may be of similar shapes as illustrated in the accompanying figures; in other embodiments conductive elements 13 and 14 may have differing shapes, for example one may be sectoral while the other is substantially rectangular.

[0047]

[0138] The antenna may be matched to a nominal input impedance of 50 ohms by choice of the angular width of conductive elements 13 and 14, and the value of the matching capacitance 27. The frequency response of the antenna may be modified by the use of a meandered perimeter for elements 13 and 14 is advantageous.

[0048]

[0139] The choice of material for the supporting dielectric substrate is not critical, examples having been shown to operate successfully with substrates having relative permittivities between 1.1 and 4.1. This allows a wide choice of material to ensure the necessary bio-compatibility with skin or internal tissue.

[0049]

[0140] In some embodiments at least one of the conductive members may be perforated or formed from a mesh to enhance the flexibility of the antenna.

[0050]

[0141] Embodiments of the invention may be manufactured using printed circuit materials and processing methods.

[0142] Embodiments of the invention may be manufactured using an injection-moulded plastic substrate with conductive areas formed thereon using a process such as laser direct structuring.

[0051]

[0143] Biocompatibility may be provided by the choice of appropriate materials for the construction of the antenna and / or by coating the complete antenna with a biocompatible conformal coating such as an approved silicone conformal coating.

[0052]

[0144] An embodiment of the present invention constructed using a closed-cell polystyrene substrate had a weight of less than 2 grams.

[0053]

[0145] The impedance bandwidth provided by an antenna according to the present invention enables its use for FMCW radar and Doppler radar systems as well as for communications and sensing.

[0054]

[0146] In some implementations a plurality of antennas configured according to the present invention may be configured as an array wherein individual antennas may be excited individually or simultaneously.

[0055]

[0147] The implanted sensor with which the antenna communicates may be an intralumenal sensor implanted in a lumen of a subject's body such as a lumen of the human or animal body. Examples of such lumens include vascular lumens such as arteries, arterioles, capillaries, venules and veins. Other examples of lumens include vessels of the heart such as the Aorta; Pulmonary Artery; Pulmonary Vein; superior Vena Cava and the Inferior Vena Cava. Other examples of lumens include lumens of the gastrointestinal tract. The sensors may also be implanted in organs such as in the tissue and / or chambers of the heart.

[0056]

[0148] For example, the antenna may be an antenna for communication with an implanted sensor configured to be operative when placed in contact with theskin of a human or animal, or implanted subcutaneously therein to communicate with said implanted sensor, the antenna comprising:

[0057] a substantially laminar dielectric substrate having a first face and a second face;

[0058] a conductive pattern formed on the first face of the substrate, forming a conductive perimetric trace and extending therefrom to form two adjacent feed terminals proximate to the centre of the first face;

[0059] a substantially continuous conductive lamina formed on the second face of the substrate, wherein the perimeter of the conductive lamina on the second face is conductively connected with the perimetric trace on the first face;

[0060] an adhesive layer applied to the first face of the substrate preventing conductive contact with the skin and enabling the attachment of the antenna to the skin of the subject.

[0061]

[0149] For example, the antenna may be an antenna for communication with an implanted sensor configured to be operative when placed in contact with the skin of a human or animal, or implanted subcutaneously therein to communicate with said implanted sensor, the antenna comprising:

[0062] a substantially laminar dielectric substrate having a first face and a second face, each of the said faces being substantially planar, the second face being provided with a substantially radial groove dimensioned to accommodate a subminiature coaxial cable;

[0063] a conductive pattern formed on the first face of the substrate, forming a conductive perimetric trace;

[0064] a substantially continuous conductive lamina formed on the second face of the substrate conductively connected with the perimetric trace on the first face;

[0065] a dielectric lamina substantially coextensive with the second face of the substrate and having a first face and a second face, the first face being providedwith a conductive pattern thereon, forming a perimetric trace and extending therefrom to form two adjacent feed terminals proximate to the centre of the first face;

[0066] a double-sided adhesive layer applied to the first face of the dielectric substrate and the first face of the dielectric lamina, thereby securing the said dielectric lamina to the substrate;

[0067] a double-sided adhesive layer applied to the second face of the dielectric lamina, thereby preventing conductive contact with the skin of the user and enabling the attachment of the antenna to the skin of the subject.

[0068]

[0150] For example, the laminar dielectric substrate may consist of a single layer.

[0069]

[0151] In some implementations radio transmission and / or receiving circuit arrangements may be housed within the substrate of an antenna constructed according to the present invention. Such a configuration may include a battery, and / or arrangements enabling the circuit arrangements therein to be powered by an external means such as by contactless charging.

[0070]

[0152] Throughout the description and claims of this specification, the word "comprise" and variations thereof means "including but not limited to", and is not intended to (and does not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0071]

[0153] Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including anyaccompanying claims, abstract and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings) or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

CLAIMS1 An antenna for communication with an implanted sensor configured to be operative when placed in contact with the skin of a human or animal, or implanted subcutaneously therein to communicate with said implanted sensor, the antenna comprising:i. a substantially planar dielectric substrate having a first face and a second face;ii. a conductive pattern formed on the first face of the substrate, forming a conductive perimetric trace and extending therefrom to form two adjacent feed terminals proximate to the centre of the first face;iii. a substantially continuous conductive lamina formed on the second face of the substrate, wherein the perimeter of the conductive lamina on the second face is conductively connected with the perimetric trace on the first face;iv. an adhesive layer applied to the first face of the substrate preventing conductive contact with the skin and enabling the attachment of the antenna to the skin of the subject.2 An antenna for communication with an implanted sensor configured to be operative when placed in contact with the skin of a human or animal, or implanted subcutaneously therein to communicate with said implanted sensor, the antenna comprising:v. a substantially planar dielectric substrate having a first face and a second face, each of the said faces being substantially planar, the second face being provided with a substantially radial groove dimensioned to accommodate a subminiature coaxial cable; vi. a conductive pattern formed on the first face of the substrate, forming a conductive perimetric trace;vii. a substantially continuous conductive lamina formed on the second face of the substrate conductively connected with the perimetric trace on the first face;viii. a dielectric lamina substantially coextensive with the second face of the substrate and having a first face and a second face, the first face being provided with a conductive pattern thereon, forming a perimetric trace and extending therefrom to form two adjacent feed terminals proximate to the centre of the first face;ix. a double-sided adhesive layer applied to the first face of the dielectric substrate and the first face of the dielectric lamina, thereby securing the said dielectric lamina to the substrate; x. a double-sided adhesive layer applied to the second face of the dielectric lamina, thereby preventing conductive contact with the skin of the user and enabling the attachment of the antenna to the skin of the subject.An antenna according to Claims 1 or 2 provided with a coaxial feeder cable having a first end and a second end, wherein:i. the first end is configured to connect to the proximate feed terminals, the outer conductor of the said cable being conductively connected to a first feed terminal and the inner conductor being capacitively connected to a feed second terminal;ii. the second end is provided with provided with a coaxial connector. An antenna according to Claims 1 or 2 wherein the dielectric substrate is a printed circuit laminate.An antenna according to Claims 1 or 2 wherein the dielectric substrate is a closed-cell foam.An antenna according to Claims 1 or 2 wherein the substrate is formed from a thermoplastic material such as polystyrene.An antenna according to Claims 1 or 2 wherein the dielectric substrate is flexible.An antenna according to Claims 1 or 2 wherein the dielectric substrate is non-planar.An antenna according to Claims 1 or 2 wherein at alt least one of the conductive elements thereof is perforated.An antenna according to Claims 1 or 2 wherein at least one of the conductive elements thereof is in the form of a mesh.An antenna according to Claims 1 or 2 wherein the dielectric substrate is substantially circular in shape.An antenna according to Claims 1 or 2 wherein the dielectric substrate is substantially elliptical in shape.An antenna according to Claims 1 or 2 wherein the dielectric substrate is substantially rectangular in shape.An antenna according to Claims 1 or 2 configured to operate at frequencies between 500 MHz and 5 GHz.An antenna according to any preceding claim additionally comprising radio frequency circuit arrangements providing for the transmission or reception of radio signals.

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