Radio frequency antenna

Abstract

Radio Frequency Antenna This description relates to a radio frequency antenna (100) comprising at least one antenna element (101A, 101B), each element having conductive regions connected by switches designed, according to a control signal, to switch said antenna element between: – a first operating mode, in which the antenna element has a half-loop antenna structure; – a second operating mode, in which the antenna element has a folded dipole antenna structure; and – a third operating mode, in which the antenna element has a straight dipole antenna structure. Figure for the abbreviation: Fig. 1

Description

Title of the invention: Radio frequency antenna technical field

[0001] This description relates generally to electronic devices, more particularly to radio frequency communication antennas. Previous technique

[0002] Many electronic devices incorporate one or more radio frequency communication antennas, also called radio frequency antennas. These antennas are notably used in the space sector, for example in satellites to enable communication between the satellites and a ground control station. In the case of small satellites such as CubeSat-type nanosatellites, which have, for a single unit (1U), lateral dimensions on the order of ten centimeters for a total volume of approximately 0.001 m³, the radio frequency antenna(s) they incorporate are subject to very strict size constraints.This description is not limited to applications in the space domain, but applies more generally to any field of application implementing telecommunications — for example, remote measurement systems using wireless sensors, radar systems, direction finding and radio-tactical applications, 5G and 6G telephony, etc. — for which it is desirable for antennas to exhibit broadband behavior.

[0003] Numerous antennas have been proposed to try to meet these needs. However, existing antennas have various drawbacks. Summary of the invention

[0004] There is a need to overcome all or part of the drawbacks of existing radio frequency antennas. In particular, it would be desirable to have radio frequency antennas available: - having small dimensions, for example ranging from a few centimeters to a few tens of centimeters; - capable of being frequency-tuned over a wide frequency range; and - exhibiting, between minimum and maximum frequencies of the antenna's operating frequency range, a substantially uniform radiation pattern.

[0005] In particular, it would be desirable for the radio frequency antenna to have a reduced footprint while being able to maintain, over a wide range of frequencies, for example on the order of a few hundred or a few thousand megahertz, a unidirectional radiation with a stable beamwidth.

[0006] To this end, one embodiment provides a radio frequency antenna comprising at least one antenna element, each element having conductive regions connected by switches intended, according to a control signal, to switch said antenna element between: - a first mode of operation, in which the antenna element has a half-loop antenna structure; - a second mode of operation, in which the antenna element has a folded dipole antenna structure; and - a third mode of operation, in which the antenna element has a straight dipole antenna structure.

[0007] According to one embodiment, the first, second and third modes of operation are intended to allow the radio frequency antenna to communicate respectively in first, second and third frequency bands, the third frequency band being higher than the second frequency band and the second frequency band being higher than the first frequency band.

[0008] According to one embodiment: - the first frequency band extends from 500 to 900 MHz; - the second frequency band extends from 900 to 1300 MHz; and - the third frequency band extends from 1300 to 1900 MHz.

[0009] According to one embodiment, the switches are further intended, depending on the control signal, to switch said antenna element into a fourth operating mode, in which the antenna element has a straight dipole antenna structure of shorter length than that of the straight dipole antenna structure of the third operating mode.

[0010] According to one embodiment, the fourth operating mode is intended to allow the radio frequency antenna to communicate in a fourth frequency band.

[0011] According to one embodiment, the fourth frequency band extends from 1900 to 2800 MHz.

[0012] According to one embodiment, the conductive regions of each antenna element form two sets of conductive regions, each having an inverted F shape and arranged symmetrically with respect to a vertical axis.

[0013] According to one embodiment, each assembly comprises: - a first T-shaped conducting region; - a second conducting region of square shape located in the extension of a vertical bar of the T formed by the first conducting region; - a third conducting region, square in shape, located directly above the second conducting region; and - a fourth rectangular conducting region located directly above the third conducting region.

[0014] According to one embodiment, the inverted F formed by each set comprises: - a horizontal bar comprising the second conducting region and a horizontal bar of the T formed by the first conducting region; - a first vertical bar extending from the second conducting region and including the third and fourth conducting regions; and - a second vertical bar extending from the horizontal bar of the T formed by the first conducting region.

[0015] According to one embodiment, each antenna element comprises, for each assembly: - a first switch connecting the first and second conductive regions; - a second switch connecting the second and third conductive regions; and - a third switch connecting the third and fourth conductive regions.

[0016] According to one embodiment: - the first, second and third switches are closed in the first operating mode; - the first and second switches are closed and the third switch is open in the second operating mode; - the first switch is closed and the second and third switches are open in the third operating mode; and - the first, second and third switches are open in the fourth operating mode.

[0017] According to one embodiment, the antenna comprises exactly two antenna elements arranged in a cross on a conductive plane.

[0018] According to one embodiment: - one of the antenna elements includes a radio frequency excitation port intended to be connected to an output of a radio frequency splitter circuit; and - the other antenna element includes a radio frequency excitation port intended to be connected to an output of a phase-shifting circuit, one input of which is connected to another output of the splitter circuit.

[0019] According to one embodiment, the antenna comprises a single antenna element disposed on a conductive plane. Brief description of the drawings

[0020] These features and advantages, as well as others, will be described in detail in the following description of particular embodiments, given by way of non-limiting example, in relation to the accompanying figures, among which:

[0021] [Fig.1] is a schematic and partial perspective view of an example of a radio frequency antenna according to one embodiment;

[0022] [Fig.2A] and [Fig.2B] are schematic and partial side views of a first antenna element of the radio frequency antenna of [Fig.1];

[0023] [Fig.3A] and [Fig.3B] are schematic and partial side views of a second antenna element of the radio frequency antenna of [Fig.1];

[0024] [Fig. 4] is a schematic and partial top view of the radio frequency antenna of [Fig. 1]; and

[0025] [Fig.5A], [Fig.5B], [Fig.5C] and [Fig.5D] illustrate, by schematic and partial side views of the first antenna element, different modes of operation of the radio frequency antenna of [Fig.1]. Description of the implementation methods

[0026] The same elements have been designated by the same reference numerals in the different figures. In particular, the structural and / or functional elements common to the different embodiments may have the same reference numerals and may have identical structural, dimensional and material properties.

[0027] For the sake of clarity, only the steps and elements useful for understanding the described embodiments have been shown and are detailed. In particular, the various applications of radio frequency antennas and the various electronic devices capable of incorporating radio frequency antennas have not been detailed, as the described embodiments are compatible with all or most applications of radio frequency antennas and with all or most electronic devices capable of incorporating such antennas, possibly with adaptations within the grasp of a person skilled in the art upon reading this description.

[0028] Unless otherwise specified, when referring to two elements connected together, this means directly connected without intermediate elements other than conductors, and when referring to two elements coupled together, this means that these two elements can be connected or linked through one or more other elements.

[0029] In the following description, when reference is made to absolute position qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative position qualifiers, such as the terms "above", "below", "superior", "inferior", etc., or to orientation qualifiers, such as the terms "horizontal", "vertical", etc., reference is made, unless otherwise specified, to the orientation of the figures.

[0030] Unless otherwise specified, the expressions "approximately", "about", "substantially", and "in the order of" mean to within 10% or 10°, preferably to within 5% or 5°.

[0031] In the following description, the terms "insulating" and "conducting" mean, unless otherwise specified, electrically insulating and electrically conductive respectively.

[0032] Unless otherwise specified, the expression "in contact with" means "in mechanical contact with".

[0033] Fig. 1 is a schematic and partial perspective view of an example of a radio frequency antenna 100 according to one embodiment.

[0034] In the illustrated example, the radio frequency antenna 100 comprises first and second antenna elements 101A and 101B arranged above a conducting plane 103. The antenna elements 101A and 101B of the antenna 100 are, for example, more precisely located on and in contact with an upper face 103T of the conducting plane 103. Each antenna element 101A, 101B has, for example, the shape of a substantially rectangular plate. In the example illustrated in [Fig.1], the rectangular plate formed by each antenna element 101 A, 101B is located in contact, by its long lower side, with the upper face 103T of the conducting plane 103. In this example, the short sides of the rectangular plate formed by each antenna element 101 A, 101B are substantially orthogonal to the upper face 103T of the conducting plane 103.

[0035] The plate formed by the antenna element 101A, for example, has dimensions substantially identical, within manufacturing variations, to those of the plate formed by the antenna element 101B. The structure of each antenna element 101A, 101B will be described in more detail below.

[0036] In the example shown, the plates formed by the antenna elements 101A and 101B are, in top view, arranged in a cross shape on and in contact with the upper face 103T of the conducting plane 103. The long upper sides of the plates formed by the antenna elements 101A and 101B are, for example, substantially orthogonal. Furthermore, the long upper side of the plate formed by the antenna element 101A intersects the long upper side of the plate formed by the antenna element 101B, for example, substantially at its midpoint.

[0037] In top view, the long sides of the plates formed by the antenna elements 101A and 101B extend, for example, laterally along the Oy and Ox directions, respectively. In the example shown, the Ox and Oy directions are orthogonal to each other and parallel to the upper face 103T of the conducting plane 103.

[0038] The conductive plane 103 includes, for example, a printed circuit board whose upper surface is coated with a conductive layer. By way of example, the conductive layer is a metallic layer, for example, a copper layer. In the example shown, the conductive plane 103 has, in top view, a substantially square shape. This example is not, however, limiting; the conductive plane 103 can more generally present, in top view, any shape, for example a polygonal shape other than square—for example, rectangular, triangular, hexagonal, etc.—or a rounded shape—for example, oval, circular, etc. In the case where the conducting plane 103 is square, the conducting plane 103 has, for example, a side of approximately 20 cm. The conducting plane 103 constitutes, for example, a ground plane for the radio frequency antenna 100, the conducting plane 103 being, in this case, intended to be connected to ground. The conducting plane 103 allows the radio frequency antenna 100 to emit upward-directed radiation along a vertical axis Oz.

[0039] Fig. 2A and Fig. 2B are schematic and partial side views of the first antenna element 101A of the radio frequency antenna 100 of Fig. 1.

[0040] In the example shown, the antenna element 101A is formed in and on a support 201, for example a printed circuit board. The support 201 has, for example, a substantially rectangular shape in top view. The support 201 is, for example, in contact, by one of its lateral faces, with the upper face 103T of the conductive plane 103.

[0041] In this example, the support 201 has a width L1 and a length L2. The width L1 and the length L2 of the support 201 are chosen, for example, according to a minimum operating wavelength / .min of the radio frequency antenna 100. The width L1 is, for example, equal to approximately Xmin / 15.2 and the length L2 is, for example, equal to approximately Xmin / 5.5. As an example, in a case where the wavelength / .min is equal to approximately 500 MHz, the width L1 is equal to approximately 39.5 mm and the length L2 is equal to approximately 110.0 mm.

[0042] In the example shown, the antenna element 101A comprises disjoint conductive regions formed on a face 201F of the support 201 and connected by switches. In the illustrated example, the antenna element 101A more precisely comprises sets 203A and 203B of conductive regions, each comprising a conductive region 205A, 205B connected, by a switch 207A, 207B, to another conductive region 209A, 209B. The conductive region 209A, 209B is connected, by another switch 211A, 211B, to another conductive region 213A, 213B and the conductive region 213A, 213B is connected, by another switch 215A, 215B, to another conductive region 217A, 217B. As an example, the switches 207A, 207B, 21IA, 21IB, 215A and 215B are diodes, for example PIN diodes (from the English "Positive Intrinsic Negative").

[0043] In the example shown, each conducting region 205A, 205B has a T-shape. More precisely, each region 205A, 205B comprises a substantially rectangular horizontal bar extending laterally along the Ox axis, parallel to the longer upper side of the rectangle formed by the support 201, and a A substantially rectangular vertical bar extending vertically along the Oz axis, perpendicular to the horizontal bar, to the lower long side of the rectangle formed by the support 201. In the illustrated example, the upper long side of the rectangle formed by the horizontal bar of the T formed by the conductive region 205A, 205B is adjacent to the upper long side of the rectangle formed by the support 201, and the lower short side of the rectangle formed by the vertical bar of the T formed by the conductive region 205A, 205B is adjacent to the lower long side of the rectangle formed by the support 201. In this example, each conductive region 205A, 205B is connected to the upper face 103T of the conductive plane 103 by the lower short side of the rectangle formed by the vertical bar of the T formed by the conductive region 205A, 205B.

[0044] In the illustrated example, the conductive regions 205A and 205B delimit a slotted line. More precisely, the slotted line is located between the upper parts of the T-shaped sections formed respectively by the conductive regions 205A and 205B.

[0045] In the example shown, each conductive region 209A, 209B has a substantially square shape. The conductive region 209A is located in the upper left corner of the support 201, extending from the horizontal bar of the T formed by the conductive region 205A. Similarly, the conductive region 209B is located in the upper right corner of the support 201, extending from the horizontal bar of the T formed by the conductive region 205B. In the illustrated example, the square formed by each conductive region 209A, 209B has a side substantially equal to the width of the rectangle formed by the horizontal bar of the T formed by the adjacent conductive region 205A, 205B.The square formed by each conductive region 209A, 209B comprises a top side adjacent to the longer top side of the rectangle formed by the support 201 and a bottom side located in the extension of the longer bottom side of the rectangle formed by the upper bar of the T formed by the adjacent conductive region 205A, 205B. Furthermore, the square formed by the conductive region 209A comprises left and right sides adjacent respectively to the shorter left side of the rectangle formed by the support 201 and to the shorter left side of the rectangle formed by the upper bar of the T formed by the conductive region 205A. Similarly, the square formed by the conductive region 209B comprises left and right sides adjacent respectively to the shorter right side of the rectangle formed by the upper bar of the T formed by the conductive region 205B and to the shorter right side of the rectangle formed by the support 201.

[0046] In the example shown, each conductive region 213A, 213B has a substantially square shape. The conductive regions 213A and 213B are located respectively in the vicinity of the lower left and right corners of the support 201. In the illustrated example, the square formed by each conductive region 213A, 213B presents a side approximately equal to that of the square formed by the neighboring conductive region 209A, 209B. Furthermore, the side of the square formed by each conductive region 213A, 213B is, for example, approximately equal to the length of the rectangle formed by the vertical bar of the T formed by the conductive region 205A, 205B. The square formed by each conductive region 213A, 213B includes an upper side adjacent to the lower side of the square formed by the neighboring conductive region 209A, 209B. In addition, the squares formed by the conductive regions 213A and 213B include left and right sides, respectively, adjacent to the shorter left and right sides of the rectangle formed by the support 201.

[0047] In the example shown, each conductive region 217A, 217B has a substantially rectangular shape. The conductive regions 217A and 217B are located in the lower left and right corners of the support 201, respectively. In the illustrated example, the rectangle formed by each conductive region 217A, 217B has a length substantially equal to the side of the square formed by the adjacent conductive region 213A, 213B. In the example shown, each conductive region 217A, 217B is connected to the conductive plane 103 by a long side of the rectangle formed by the conductive region 217A, 217B. The rectangle formed by each conductive region 217A, 217B includes a long upper side adjacent to the lower side of the adjacent conductive region 213A, 213B.Furthermore, the rectangle formed by the conductive region 217A comprises a small left side and a large lower side adjacent respectively to the small left side and the large lower side of the rectangle formed by the support 201. Similarly, the rectangle formed by the conductive region 217B comprises a small right side and a large lower side adjacent respectively to the small right side and the large lower side of the rectangle formed by the support 201.

[0048] The conductive regions 205A, 209A, 213A and 217A of the assembly 203A have a general inverted F shape comprising: - a horizontal bar comprising the conductive region 209A and the horizontal bar of the T formed by the conductive region 205A; - a vertical bar connected to the horizontal bar at the level of the conductive region 209A and comprising the conductive regions 213A and 217A; and - another vertical bar connected to the horizontal bar at the middle of the horizontal bar of the T formed by the conductive region 205A and including the vertical bar of the T formed by the conductive region 205A.

[0049] Similarly, the conductive regions 205B, 209B, 213B and 217B of the assembly 203B have a general inverted F shape comprising: - a horizontal bar including the conductive region 209B and the horizontal bar of the T formed by the conductive region 205B; - a vertical bar connected to the horizontal bar at the level of the conductive region 209B and comprising the conductive regions 213B and 217B; and - another vertical bar connected to the horizontal bar at the level of the middle of the horizontal bar of the T formed by the conductive region 205B and comprising the vertical bar of the T formed by the conductive region 205B.

[0050] In the example illustrated in [Fig.2A], the inverted Fs formed by the sets 203A and 203B of conducting regions are substantially symmetric with respect to a vertical axis orthogonal to the upper face 103T of the conducting plane 103 and separating the face 201F of the support 201 into two regions of substantially equal areas.

[0051] The conductive regions of each assembly 203A, 203B are for example metallic, for example copper.

[0052] In the illustrated example, the conductive regions 205A and 205B are connected by a load 219. The load 219 comprises, for example, one terminal connected to the conductive region 205A and another terminal connected, via a conductor 221 located in the antenna element 101B, to the conductive region 205B. The load 219 is, for example, part of an electronic circuit designed to give the antenna 100 a frequency-agile antenna (FAA) behavior. By way of example, the load 219 is a variable reactive load, for example, a variable inductive load.

[0053] In the example shown, the support 201 of the antenna element 101A further includes a slot 223 for receiving the antenna element 10IB. In this example, the slot 223 extends vertically from the longer upper side of the rectangle formed by the support 201 to the longer lower side of the rectangle formed by the support 201. The slot 223 has, for example, a depth less than the height of the upper bar of the T formed by each conductive region 205A, 205B.

[0054] In the illustrated example, the antenna element 101A further comprises a conductive track 225 located on and in contact with a face 201R of the support 201 opposite face 201F. The conductive track 225 comprises a straight vertical portion located below and directly above the vertical bar of the T formed by the conductive region 205A. By way of example, the conductive track 225 and the vertical bar of the T formed by the conductive region 225 are part of a microstrip line. The conductive track 225 comprises a first end connected, via a conductive via 227 passing through the conductive plane 103, to a radio frequency excitation port 229 of the antenna element 101A located on the underside of the conductive plane 103, and a second end connected to a load 231.The radio frequency excitation port 229 is for example intended to be connected or linked to an excitation circuit of the antenna 100 (not shown), for example by a coaxial cable connected to the excitation port. radio frequency 229. In the illustrated example, the conductive track 225 goes around the slot 223.

[0055] In the example shown, the load 231 connects the conductive track 225 to a conductive region 233 located on and in contact with the face 201R of the support 201, below and directly above the conductive region 205B. Although not shown in Figures 2A and 2B, the conductive region 233 is connected to the conductive region 205B, for example, by a conductive via located directly above the conductive region 233 and passing through the entire thickness of the support 201. The load 231 is, for example, part of a Tunable Matching Network (TMN). As an example, the load 231 is a variable reactive component, for example, a variable capacitive load.

[0056] In the illustrated example, conductive regions 235A and 235B located on and in contact with the upper face 103T of the conductive plane 103 respectively allow the conductive regions 217A and 217B to be connected to the conductive plane 103.

[0057] In the example shown, the straight portion of the conductive track 225 has a width W1, and the vertical bar of the T formed by the conductive region 205A has a width approximately three times greater than the width W1 (3W1). For example, the width W1 is approximately 2.42 mm.

[0058] In the illustrated example, the conductive regions 205A and 205B are separated by a distance W2. The distance W2 corresponds to the width of the gap delimited by the upper bars of the T-shaped sections formed by the conductive regions 205A and 205B. As an example, the distance W2 is approximately 2.18 mm.

[0059] In the example shown, the conductive regions 213A and 217A are separated from the vertical bar of the T formed by the conductive region 205A by a distance W3. Furthermore, in this example, the conductive regions 213B and 217B are separated from the vertical bar of the T formed by the conductive region 205B by a distance W3. For example, the distance W3 is approximately 17.7 mm.

[0060] In the illustrated example, a distance W4 separates the vertical bars from the T-shaped sections formed respectively by the conducting regions 205A and 205B. The distance W4 corresponds, for example, approximately to the sum of the distances W2 and W3. As an example, the distance W4 is equal to approximately 20 mm.

[0061] In the example shown, the slot 223 has a width W5. As an example, the width W5 is approximately 1.18 mm.

[0062] In the illustrated example, the conductive region 205B is connected to the conductor 221 via a conductive track 237 having a width W6. As an example, the width W6 is approximately 1.0 mm.

[0063] Fig. 3A and Fig. 3B are schematic and partial side views of antenna element 101B of radio frequency antenna 100 of Fig. 1.

[0064] The antenna element 10IB of Figures 3A and 3B includes elements in common with the antenna element 101A of Figures 2A and 2B. These common elements will not be detailed again below. The antenna element 101B differs from the antenna element 101A in that the antenna element 101B lacks the slot 223.

[0065] In the example shown, the antenna element 101B includes a slot 323 for receiving the antenna element 101A. Slot 323 of antenna element 101B is specifically designed to cooperate with slot 223 of antenna element 101A to allow the supports 201 of antenna elements 101A and 101B to be nested together, thus forming the cross-shaped structure of the radio frequency antenna 100. In the illustrated example, slot 323 of antenna element 101IB extends vertically from the lower long side of the rectangle formed by support 201 to the upper long side of the rectangle formed by support 201. In the illustrated example, the conductive track 225 of antenna element 101B flows around slot 323. Slot 323 has a depth, for example, that is strictly greater than the height of the vertical bar of the T formed by each conductive region 205A, 205B.

[0066] Fig. 4 is a schematic and partial top view of the radio frequency antenna 100 of Fig. 1. Antenna elements 101A and 101B have not been shown in Fig. 4 in order to avoid cluttering the drawing.

[0067] In the example shown, the radio frequency excitation port 229 of the antenna element 101A and the conductive regions 235A and 235B intended to connect the antenna element 101A to the conductive plane 103 are substantially aligned along the horizontal Ox direction. Furthermore, in this example, the radio frequency excitation port 229 of the antenna element 101B and the conductive regions 235A and 235B intended to connect the antenna element 101B to the conductive plane 103 are substantially aligned along the horizontal Oy direction.

[0068] Although not detailed in the figures, the radio frequency excitation port 229 of the antenna element 101A is, for example, intended to be connected to an output of a radio frequency splitter circuit, one input of which is, for example, connected to a transmit / receive circuit. Furthermore, the radio frequency excitation port 229 of the antenna element 101B is, for example, intended to be connected to an output of a phase-shifting circuit, which includes, for example, an input connected to another output of the radio frequency splitter circuit. In transmission, the phase-shifting circuit is, for example, intended to introduce a phase shift, for example, of approximately 90°, between the signals applied to the radio frequency excitation ports 229 of the antenna elements 101A and 101B.

[0069] In this case, signals exhibiting substantially orthogonal polarizations are respectively emitted by the antenna elements 101A and 101B of the radio frequency antenna 100. This allows the radio frequency antenna 100 to emit radiation exhibiting circular polarization.

[0070] Fig. 5A, Fig. 5B, Fig. 5C and Fig. 5D illustrate, by schematic and partial side views of the antenna element 101A, different modes of operation of the radio frequency antenna 100 of Fig. 1.

[0071] In Figures 5A to 5D, each switch 207A, 207B, 211A, 211B, 215A, 215B is symbolized by a filled square when the switch is in a conducting, or closed, state, and by an empty square when the switch is in a blocking, or open, state. Furthermore, in Figures 5A to 5D, each conductive region 205A, 205B, 209A, 209B, 213A, 213B, 217A, 217B is hatched when the conductive region is isolated from the other conductive regions of the antenna element 101A.

[0072] Fig. 5A illustrates an operating mode in which the antenna element 101A has a half-loop antenna structure.

[0073] In the illustrated example, switches 207A, 21IA, and 215A are in the conducting state. This allows the conductive regions 205A, 209A, 213A, and 217A to be connected. Similarly, in this example, switches 207B, 21IB, and 215B are in the conducting state. This allows the conductive regions 205B, 209B, 213B, and 217B to be connected.

[0074] In the operating mode illustrated in [Fig.5A] where the antenna element 101A has a half-loop antenna structure, an electric current 501A runs through all the conductive regions of the assemblies 203A and 203B, for example from the bottom of the vertical bar of the T formed by the conductive region 205B and from the bottom of the conductive region 217B to the bottom of the vertical bar of the T formed by the conductive region 205A and to the bottom of the conductive region 217A.

[0075] The operating mode illustrated in [Fig. 5A] is, for example, intended to allow the radio frequency antenna 100 to communicate in a first frequency band. For example, the first frequency band extends from 500 to 900 MHz. In this example, the load 219 has a capacitance varying from approximately 2 pF, for an operating frequency of approximately 500 MHz, to 0 pF, for an operating frequency of approximately 900 MHz. Furthermore, the load 231 has an inductance varying from approximately 3.5 nH, for an operating frequency of approximately 500 MHz, to approximately 0.5 nH, for an operating frequency of approximately 900 MHz.

[0076] Fig. 5B illustrates an operating mode in which the antenna element 101A has a folded, or bent, dipole antenna structure.

[0077] In the illustrated example, switches 207A and 21IA are in the conducting state, and switch 215A is in the blocked state. This allows the conductive regions 205A, 209A, and 213A to be connected, and the conductive region 217A to be isolated. Similarly, in this example, switches 207B and 21IB are in the conducting state, and switch 215B is in the blocked state. This allows the conductive regions 205B, 209B, and 213B to be connected, and the conductive region 217B to be isolated.

[0078] In the operating mode illustrated in [Fig.5B] where the antenna element 101A has a folded dipole antenna structure, an electric current 501B flows through the conductive regions 205A, 205B, 209A, 209B, 213A and 213B, for example from the bottom of the conductive region 213B to the bottom of the conductive region 213A.

[0079] The operating mode illustrated in [Fig. 5B] is, for example, intended to allow the radio frequency antenna 100 to communicate in a second frequency band. By way of example, the second frequency band extends from 900 to 1300 MHz. In this example, the load 219 has a capacitance varying from approximately 2.2 pF, for an operating frequency of approximately 900 MHz, to approximately 0.3 pF, for an operating frequency of approximately 1300 MHz. Furthermore, the load 231 has an inductance varying from approximately 16 nH, for an operating frequency of approximately 900 MHz, to approximately 13 nH, for an operating frequency of approximately 1300 MHz.

[0080] Fig. 5C illustrates an operating mode in which the antenna element 101A has a straight, or straight, dipole antenna structure.

[0081] In the illustrated example, switch 207A is in the conducting state, and switches 21IA and 215A are in the blocked state. This allows the conductive regions 205A and 209A to be connected, and the conductive regions 213A and 217A to be isolated. Similarly, in this example, switch 207B is in the conducting state, and switches 21IB and 215B are in the blocked state. This allows the conductive regions 205B and 209B to be connected, and the conductive regions 213B and 217B to be isolated.

[0082] In the operating mode illustrated in [Fig.5C] where the antenna element 101A has a straight dipole antenna structure, an electric current 501C flows through the conductive regions 205A, 205B, 209A and 209B, for example from the right of the conductive region 209B to the left of the conductive region 209A.

[0083] The operating mode illustrated in [Fig. 5C] is, for example, intended to allow the radio frequency antenna 100 to communicate in a third frequency band. For example, the third frequency band extends from 1300 to 1900 MHz. In this example, the load 219 has a capacitance varying from approximately 0.7 pF, for an operating frequency of approximately 1300 MHz, to approximately 0.1 pF, for an operating frequency of approximately 1900 MHz. Furthermore, the load 231 has an inductance varying from approximately 8 nH, for an operating frequency of approximately 1300 MHz, at approximately 5 nH, for an operating frequency of approximately 1900 MHz.

[0084] Fig. 5D illustrates an operating mode in which the antenna element 101A has a straight, or straight, dipole antenna structure of strictly lesser length than the antenna structure previously described in relation to Fig. 5C.

[0085] In the illustrated example, switches 207A, 21IA, and 215A are in the blocked state. This isolates the conductive regions 205A, 207A, 213A, and 217A. Similarly, in this example, switches 207B, 21IB, and 215B are in the blocked state. This isolates the conductive regions 205B, 209B, 213B, and 217B.

[0086] In the operating mode illustrated in [Fig.5D] where the antenna element 101A has a straight dipole antenna structure of reduced length compared to the case illustrated in [Fig.5C], an electric current 501D flows through the conductive regions 205A and 205B, for example from the right of the conductive region 205B to the left of the conductive region 205A.

[0087] The operating mode illustrated in [Fig. 5D] is, for example, intended to allow the radio frequency antenna 100 to communicate in a fourth frequency band. By way of example, the fourth frequency band extends from 1900 to 2800 MHz. In this example, the load 219 has a capacitance varying from approximately 0.2 pF, for an operating frequency of approximately 1900 MHz, to 0 pF, for an operating frequency of approximately 2800 MHz. Furthermore, the load 231 has an inductance varying from approximately 3 nH, for an operating frequency of approximately 1900 MHz, to approximately 1 nH, for an operating frequency of approximately 2800 MHz.

[0088] The switching between the operating modes of the radio frequency antenna 100 described above in relation to Figures 5A to 5D is, for example, a function of a control signal applied to the switches. The control signal is, for example, provided by a control circuit (not shown) connected to each switch.

[0089] Although not detailed, antenna element 101B, for example, operates in a manner similar or identical to that of antenna element 101B. Furthermore, the switching between operating modes is, for example, controlled substantially simultaneously for antenna elements 101A and 101B. This ensures that antenna elements 101A and 101B have substantially identical antenna structures, apart from manufacturing variations.

[0090] One advantage of the radio frequency antenna 100 is its compact size. For example, at a maximum operating wavelength Xmax, the radio frequency antenna 100 has an electrical dimension equal to approximately 0.7. More precisely, the radio frequency antenna 100, for example, has an electrical length equal to approximately Xmax / 5.5 and an electrical height equal to approximately Xmax / 15.2.

[0091] Another advantage of the 100 radio frequency antenna is that it has a wide frequency tuning range. The 100 radio frequency antenna, for example, has a tunable fractional bandwidth of approximately 143%.

[0092] Another advantage of the radio frequency antenna 100 is that it exhibits a unidirectional and very stable radiation pattern. This stability is also achieved within a very wide frequency band, extending, for example, from 500 MHz to 2.9 GHz.

[0093] Various embodiments and variations have been described. Those skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will become apparent to them. In particular, an example of an embodiment of the radio frequency antenna 100 has been described above in which the antenna 100 comprises two antenna elements 101A and 101B arranged in a cross and is intended to emit radiation with circular polarization. This example is not, however, limiting, and those skilled in the art are able, from the indications in this description, to foresee various types of geometries for the radio frequency antenna 100.

[0094] By way of example, a person skilled in the art could, based on the information in this description, design a radio frequency antenna similar to antenna 100 but comprising only one antenna element from among antenna elements 101A and 101B, for example, antenna element 101A. In this case, the radio frequency antenna would, for example, be designed to emit radiation with linear, or rectilinear, polarization. The practical implementation of such an antenna is within the capabilities of a person skilled in the art upon reading this description. In particular, it would be possible to omit slot 223 and via 221.

[0095] Furthermore, although Figures 5A to 5D illustrate four operating modes of the radio frequency antenna 100, some operating modes may be omitted, for example, depending on the intended application. By way of example, the operating mode shown in relation to [Fig. 5D] may be omitted, for example, in a case where the antenna is not intended to transmit a signal with a frequency above 2 GHz.

[0096] Finally, the practical implementation of the described embodiments and variants is within the reach of a person skilled in the art, based on the functional specifications given above. In particular, the practical implementation of antenna elements 101A and 101B, in particular the construction of conductive regions, switches and loads, is within the reach of a person in the trade upon reading this description.

[0097] Moreover, the adjustment of the loads, i.e. the choice of the capacitance and inductance values ​​for each operating frequency value of the antenna 100, is within the reach of a person skilled in the art from the indications in this description.

Claims

Demands

1. Radio frequency antenna (100) comprising at least one antenna element (101A, 101B) each having conductive regions (205A, 205B, 209A, 209B, 213A, 213B, 217A, 217B) connected by switches (207A, 207B, 21IA, 21IB, 215A, 215B) intended, according to a control signal, to switch said antenna element between: - a first operating mode, in which the antenna element has a half-loop antenna structure; - a second operating mode, in which the antenna element has a folded dipole antenna structure; and - a third operating mode, in which the antenna element has a straight dipole antenna structure.

2. Antenna (100) according to claim 1, wherein the first, second and third modes of operation are intended to enable the radio frequency antenna to communicate respectively in first, second and third frequency bands, the third frequency band being higher than the second frequency band and the second frequency band being higher than the first frequency band.

3. Antenna (100) according to claim 2, wherein: - the first frequency band extends from 500 to 900 MHz; - the second frequency band extends from 900 to 1300 MHz; and - the third frequency band extends from 1300 to 1900 MHz.

4. Antenna (100) according to any one of claims 1 to 3, wherein the switches (207A, 207B, 21 IA, 21 IB, 215A, 215B) are further intended, depending on the control signal, to switch said antenna element (101 A, 101B) into a fourth operating mode, wherein the antenna element has a straight dipole antenna structure of shorter length than the straight dipole antenna structure of the third operating mode.

5. Antenna (100) according to claim 4, wherein the fourth mode of operation is intended to enable the radio frequency antenna to communicate in a fourth frequency band.

6. Antenna (100) according to claim 5, wherein the fourth frequency band extends from 1900 to 2800 MHz.

7. Antenna (100) according to any one of claims 4 to 6, wherein the conductive regions (205A, 205B, 209A, 209B, 213A, 213B, 217A, 217B) of each antenna element (101A, 101B) form two sets (203A, 203B) of conductive regions each having an inverted F shape and arranged symmetrically with respect to a vertical axis.

8. Antenna (100) according to claim 7, wherein each assembly (203A, 203B) comprises: - a first T-shaped conducting region (205A, 205B); - a second square-shaped conducting region (209A, 209B) located in the extension of a vertical bar of the T formed by the first conducting region; - a third square-shaped conducting region (213A, 213B) located directly above the second conducting region; and - a fourth rectangular-shaped conducting region (217A, 217B) located directly above the third conducting region.

9. Antenna (100) according to claim 8, wherein the inverted F formed by each assembly (203A, 203B) comprises: - a horizontal bar comprising the second conductive region (209A, 209B) and a horizontal bar of the T formed by the first conductive region (205A, 205B); - a first vertical bar extending from the second conductive region and comprising the third (213A, 213B) and fourth (217A, 217B) conductive regions; and - a second vertical bar extending from the horizontal bar of the T formed by the first conductive region.

10. Antenna (100) according to claim 8 or 9, wherein each antenna element (101 A, 101B) comprises, for each assembly (203A, 203B): - a first switch (207A, 207B) connecting the first (205A, 205B) and second (209A, 209B) conductive regions; - a second switch (21 IA, 21 IB) connecting the second (209A, 209B) and third (213A, 213B) conductive regions; and - a third switch (215A, 215B) connecting the third (213A, 213B) and fourth (217A, 217B) conductive regions.

11. Antenna (100) according to claim 10, wherein:

12.

13.

14. - the first (207A, 207B), second (21 IA, 21 IB) and third (215A, 215B) switches are closed in the first operating mode; - the first (207A, 207B) and second (21 IA, 21 IB) switches are closed and the third switch (215A, 215B) is open in the second operating mode; - the first switch (207A, 207B) is closed and the second (21IA, 21IB) and third (215A, 215B) switches are open in the third operating mode; and - the first (207A, 207B), second (21 IA, 21 IB) and third (215A, 215B) switches are open in the fourth operating mode. Antenna (100) according to any one of claims 1 to 11, comprising exactly two antenna elements (101 A, 101 B) arranged in a cross on a conductive plane (103). Antenna (100) according to claim 12, wherein: - one of the antenna elements (101A) includes a radio frequency excitation port (229) intended to be connected to an output of a radio frequency splitter circuit; and - the other antenna element (101B) includes a radio frequency excitation port (229) intended to be connected to an output of a phase-shifting circuit, one input of which is connected to another output of the splitter circuit. Antenna (100) according to any one of claims 1 to 11, comprising a single antenna element (101A) disposed on a conductive plane (103).