Low-profile, impedance-robust radio antenna
Inventors
NIKOLAYEV, DENYS • ZHADOBOV, Maxim • Sauleau, Ronan
Assignees
Centre National de la Recherche Scientifique CNRS • Universite de Rennes 1 • Bodycap SAS
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Publication Number
US-10910701-B2
Publication Date
2021-02-02
Expiration Date
Abstract
The radio antenna comprises a substrate formed of a dielectric material; a ground plane made of an electrically conductive material, the ground plane being arranged on a first face (F2) of the substrate; a resonator configured to convert an incident electrical signal into an electromagnetic wave. The resonator includes a first element (E1) having a first characteristic impedance and a second element (E2) having a second characteristic impedance that is higher than the first characteristic impedance. The first element (E1) is configured to receive the incident electrical signal, the first element (E1) is formed by a strip of electrically conductive material, the strip being arranged on a second face (F1) of the substrate opposite the first face (F2). The second element (E2) is formed by a rectilinear segment, cut in the ground plane and separated from the rest of the ground plane by a slot (202) of fixed width. The second element (E2) is electrically connected to the ground plane at a first end of the segment and electrically connected to the first element at a second end of the segment by means of a via (210) passing through the substrate.
Core Innovation
The radio antenna converts an incident electrical signal into an electromagnetic wave using a resonator configured with a first element and a second element having different characteristic impedances. The first element receives the incident electrical signal and is formed by a strip of electrically conductive material arranged on a second face of a dielectric substrate, while a ground plane is arranged on a first face.
The second element is formed by a rectilinear segment cut out in the ground plane and separated from the rest of the ground plane by a slot of substantially fixed width. Electrical connections are established such that the second element is electrically connected to the ground plane at a first end of the rectilinear segment and electrically connected to the first element at a second end of the rectilinear segment by means of a via passing through the substrate.
The rectilinear segment is oriented in a first direction, and the conductive strip extends longitudinally in a second direction distinct from the first direction. A resonance frequency f_res of the radio antenna is related to a dimension l_high along the first direction, a dimension l_low along the first direction of the strip, and to the characteristic impedances Z_c-low and Z_c-high, with phase constants β_low and β_high defined by the effective relative permittivity of the first and second elements, respectively.
In biotelemetry device forms, the substrate is in a flexible material and is rolled so that the first face turns towards the inside of a capsule while the second face faces the outside, or the substrate is made of a rigid material and of cylindrical shape, integrated in a capsule with the first face turned towards the interior and the second face turned towards the outside.
Claims Coverage
The document includes three independent claims. Across them, the core inventive features are (i) a resonator with first and second elements having first and second characteristic impedances, (ii) coupling via a rectilinear segment cut from a ground plane with a fixed-width slot and a via through the substrate to connect to a strip element, and (iii) resonance-frequency relationships and capsule-oriented substrate configurations (flexible rolled vs rigid cylindrical).
Impedance-variant resonator with strip first element and slot-separated rectilinear second element
A radio antenna having a dielectric substrate, a ground plane on a first face, and a resonator that converts an incident electrical signal into an electromagnetic wave, the resonator comprising a first element with a first characteristic impedance and a second element with a second characteristic impedance greater than the first.
Via-coupled rectilinear segment cut from ground plane separated by fixed-width slot
The first element receives the incident electrical signal and is formed by a strip of electrically conductive material arranged on a second face opposite the first face; the second element is formed by a rectilinear segment cut out in the ground plane and separated from the rest of the ground plane by a slot of substantially fixed width, with the second element electrically connected to the ground plane at a first end and electrically connected to the first element at a second end by means of a via passing through the substrate.
Resonance-frequency relation using characteristic impedances and phase constants
A resonance frequency f_res of the radio antenna related to a dimension l_high along the first direction of the rectilinear segment and a dimension l_low along the first direction of the strip, to the characteristic impedance Z_c-low of the first element and the characteristic impedance Z_c-high of the second element by defined relations using phase constants β_low and β_high based on effective relative permittivity.
Capsule-integrated biotelemetry device with flexible rolled dielectric substrate orientation
A biotelemetry device comprising a radio antenna wherein the substrate is in a flexible material and the biotelemetry device is in the form of a capsule in which the substrate is rolled so that the first face of the substrate is turned towards the inside of the capsule and the second face faces the outside of the capsule.
Capsule-integrated biotelemetry device with rigid cylindrical dielectric substrate orientation
A biotelemetry device wherein the substrate is made of a rigid material and of cylindrical shape, the biotelemetry device being integrated in a capsule with the radioelectric antenna placed so that the first face of the substrate is turned towards the interior of the capsule and the second face is turned towards the outside of the capsule.
Taken together, the independent claims define a radio antenna resonator that combines a strip first element and a slot-separated rectilinear second element with higher characteristic impedance, electrically coupled through a via through the substrate, including an explicit resonance-frequency relationship. They further cover biotelemetry device capsule integration with either a flexible rolled substrate orientation or a rigid cylindrical substrate orientation.
Stated Advantages
Impedance robustness against variations in surrounding biological media.
Reduced resonance shift between air and a muscle-mimicking phantom (reported as about 2%).
Low reflection coefficient magnitude over a surrounding-media range (reported as |S11| < −10 dB).
Miniaturization.
Printed-circuit manufacture.
Flexible, capsule-conformable embodiment.
Documented Applications
A biotelemetry device using the claimed radio antenna.
An ingestible/implantable capsule form described for integration of the radio antenna.
Use of a 434 MHz example antenna with a muscle-mimicking phantom for surrounding-media performance reporting.
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