Metamaterial-enabled beam scanning antenna

Abstract

This invention discloses a leaky-wave antenna device comprising: a first metasurface including a first dielectric substrate having a first conductive element array; and a second metasurface including a second dielectric substrate having a second conductive element array. The antenna device further includes a conductive ground plane, a microactuator, and a feed including a pair of switchable dipoles. The first and second metasurfaces and the conductive ground plane are stacked and substantially parallel to each other, wherein the first metasurface is located between the second metasurface and the conductive ground plane. A spacing between the conductive ground plane and the first metasurface is adjustable by operation of the microactuator. The feed is positioned between the first and second metasurfaces at a location corresponding to the center of one of the first and second arrays. The leaky-wave antenna device is operable to control a beam over a wide range by selectively energizing (powering) the pair of dipoles and by adjusting the spacing between the conductive ground plane and the first metasurface.

Description

Technical Field

[0001] The present invention relates to an antenna in which the surface of a metamaterial is controllably displaced relative to a ground plane to introduce a phase shift and thereby achieve beam manipulation. Prior Technology

[0002] Beam-controllable high-gain antennas operating in millimeter-wave (mm-wave) frequency bands (e.g., 30 GHz to 300 GHz) are expected to play a critical role in several wireless applications, including 5G and above, particularly in maintaining wireless links in dynamic environments. However, beam control of antennas at such high frequencies is challenging because conventional phased array and beam-switching techniques are limited by several factors, including loss performance and the availability of off-the-shelf components.

[0003] The inventors of this case (early work by Rabbani, Churm and Feresidis; "Electro-Mechanically Tunable Meta-Surfaces for Beam-Steered Antennas from mm-Wave to THz"; Proceedings of the 50th European Microwave Conference; 12-14 January 2021; Utrecht; pp. 416-419; the entire contents of which are incorporated herein by reference) have led to the development of a leaky wave antenna (LWA) using an extremely low-loss tunable meta-surface as a phase-shifting material to achieve beam manipulation capabilities.

[0004] An LWA is a type of traveling-wave antenna to distinguish it from a more conventional resonant antenna (such as a monopole or dipole). In an LWA, the radio frequency (RF) current that generates the radio signal propagates along the antenna in one direction. This is the opposite of a resonant antenna, where the RF current propagates along the antenna in two directions to bounce between ends. The traveling wave in an LWA is typically a fast wave, with a phase velocity greater than the speed of light.

[0005] In the context of this application, a metasurface is a thin sheet material (its thickness is less than the wavelength of the RF signal modulated by the metasurface) having a periodic array of scattering elements whose size and period are relatively small compared to the operating wavelength. A typical metasurface may include a thin dielectric substrate with a thickness of < 1 mm, on which a two-dimensional array of conductive metal elements having a size on the order of millimeters is printed or etched.

[0006] The inventor's early work revealed two different LWA designs.

[0007] The first LWA design shown in Figure 1(b) is based on a tunable high impedance surface (HIS) 1 and a static partial reflective surface (PRS) 2, each formed as a supersurface and configured substantially parallel to each other. The first LWA design is configured to operate at 37 GHz. As shown in Figure 1(b), HIS 1 and PRS 2 are each formed by a two-dimensional array of square conductive patch elements etched on a planar printed circuit board (PCB). HIS 1 and PRS 2 each include a Rogers RT / Duroid 5880 substrate having a copper cladding layer with a dielectric constant εr = 2.2, a thickness h1 = 0.787 mm, and a thickness t = 0.035 mm. HIS 1 is etched to define a two-dimensional array of square conductive patch elements 4, each having a periodicity of 1.53 mm and 1.83 mm in length, on a first dielectric substrate 100 of thickness h1. PRS 2 is etched to define a two-dimensional array of square conductive patch elements 5, each with a periodicity of 3 mm and 3.3 mm, on a second dielectric substrate 200, which also has a thickness h 1. HIS 1 is positioned substantially parallel to and above a conductive ground plane 3, with a distance h 2 between HIS 1 and the ground plane 3. PRS 2 is positioned on HIS 1 and with a distance h 3 between HIS 1 and the ground plane 3. The distance h 3 defines a cavity height of LWA and determines a resonant frequency of LWA. The total area of ​​the HIS / PRS assembly is approximately 3 cm × 9 cm. The ground plane 3 is mounted on a piezoelectric actuator 6 and can be vertically displaced by the piezoelectric actuator 6 to allow the distance h 2 to vary. Figure 1(a) shows a discrete unit cell of HIS 1 of Figure 1(b), but upside down relative to Figure 1(b). A unit cell includes a single square conductive patch element 4 on a first dielectric substrate 100. The conductive ground plane 3 is spaced apart from the first dielectric substrate 100 by a distance h 2.

[0008] The corresponding edges of HIS 1 and PRS 2 are joined on one side of LWA by a reflector 7, and a printed dipole-fed antenna 8 is provided adjacent to the reflector 7 and between HIS 1 and PRS 2.

[0009] Figures 2(a) and 2(b) respectively show the simulated S11 values ​​and S11 phase responses of the HIS reflection coefficient for various displacements h2 of the LWA of Figure 1(b) operating within a frequency band from 35 GHz to 40 GHz. The ground distance h2 can be varied from 0 μm to 400 μm. It can be seen that a variation from 40 μm to 400 μm (Δh2 = 360 μm) produces a phase shift of approximately ΔφHIS = 142° in the reflection coefficient (φHIS) of HIS 1 at 37 GHz, while exhibiting a negligible low loss of approximately 0.06 dB. A flexural amplified piezoelectric actuator 6 can be used to adjust the displacement h2 between the periodic array layer of HIS 1 and the ground plane 3. Similarly, the simulated S11 absolute values ​​(R) and phase (φPRS) of PRS 2 can be obtained, and at 37 GHz these are 0.94 and 156°, respectively. According to the following relationship, the directivity and main beam angle of the LWA will depend on the S11 responses of HIS 1 and PRS 2: (1) Where F(θ) represents the radiated power pattern of the feed element, and λ represents the operating wavelength. The phase shift provided by HIS 1 is given by the following relationship: (2) Where φt is the phase shift applied to the wave as it passes through the patterned metal surface.

[0010] Using equations (1) and (2), it is predicted that for a HIS phase shift of Δφ HIS = 142° at 37 GHz, LWA will exhibit a beam control range of approximately 37° (from 14° to 51°), as shown in Figure 3.

[0011] The piezoelectric actuator 6 may include a linear piezoelectric actuator with flexural amplification, and may provide a displacement up to 0.5 mm. The piezoelectric actuator 6, on which the ground plane 3 is mounted, may expand or contract depending on an applied DC bias voltage, thus allowing the displacement h2 to vary as needed.

[0012] The printed dipole antenna 8 of the LWA is a half-wave antenna designed to operate at 37 GHz, as shown in Figure 4 (for example). The directivity of the printed dipole antenna 8 is enhanced by providing a reflector 7 (see Figure 1(b)) at a distance of 0.9 mm from the rear side of the antenna 8. The printed dipole antenna 8 is implemented in an LWA with 9 × 27 PRS elements and 16 × 49 HIS elements, and a suitable simulation is run around the operating frequency of 37 GHz to generate the S11 response for different values ​​of h2 shown in Figure 5(a). Figure 5(b) shows the far-field radiation pattern (FRP) in the H plane at 37 GHz for various h2 values. As can be seen from the figure, the S11 response remains below -10 dB at approximately 37 GHz for various displacements. The LWA has a maximum gain of 23.9 dBi and a maximum beam control of 33° at 37 GHz over an h² variation from 40 μm to 400 μm.

[0013] A second LWA design, as shown in Figure 6, has been proposed for the low THz band (e.g., approximately 280 GHz). To reduce structural complexity, this second LWA design includes a periodic PRS 10 with a circular aperture and ignores the HIS near the ground plane 3. In this variation, the PRS 10 is vertically displaced relative to the ground plane 3 by a piezoelectric actuator 6, thus allowing adjustment of the resonant cavity height h 3. The PRS 10 is in the form of a metal layer with a thickness h 1 = 0.3 mm and a two-dimensional 11 × 31 array of circular apertures 11 with a diameter of 0.6 mm and a periodicity of 0.75 mm. The metal ground plane 3 has a thickness h 2, and the PRS 10 is positioned 0.46 mm above the ground plane 3, wherein the cavity height h 3 is variable between 0.44 mm and 0.5 mm by applying different DC bias currents to the piezoelectric actuator 6. The thickness h2 is typically on the order of millimeters to provide a stable substrate and sufficient anchoring for one of the flanges of a standard waveguide feed. Preferably, the thickness h2 is greater than a skin depth, ideally greater than two skin depths. The LWA is excited by a waveguide feed slot element 12 formed toward one edge of the ground plane 3. Embodiments with or without a HIS 1 near the ground plane 3 can be designed for frequencies at least between 20 GHz and 1 THz.

[0014] Figures 7(a) and 7(b) show the simulation results of the second LWA design operating at 280 GHz. For different values ​​of h3, Figure 7(a) shows the FRP in the H-plane, while Figure 7(b) shows the S11 response. It can be seen that the LWA has a maximum gain of 18 dBi and produces beam control within approximately 18° of a displacement of 0.06 mm, within a 3 dB gain loss. However, it can be seen that for some displacements, the S11 response increases from -10 dB.

[0015] Although the inventors’ earlier work demonstrated the feasibility of beam manipulation, there is still room for improvement. Summary of the Invention

[0016] From a first-state perspective, a leaky antenna device is provided, comprising: A first metasurface, comprising a first dielectric substrate having a first array of conductive elements; A second metasurface, comprising a second dielectric substrate having a second array of conductive elements; One conductive ground; A micro actuator; and A power supply, comprising a pair of switchable dipoles; The first and second metasurfaces and the conductive ground plane are stacked and substantially parallel to each other, wherein the first metasurface is located between the second metasurface and the conductive ground plane; The distance between the conductive ground plane and the first metasurface can be adjusted by the operation of the microactuator; and The power supply is positioned between the first and second metasurfaces at a location corresponding to the center of one of the first and second arrays.

[0017] The first metasurface can be configured as a high-impedance surface.

[0018] The second metasurface can be configured as a partial reflective surface.

[0019] The first and second metasurfaces are designed to impart a designed phase shift to the RF signals when reflected from their respective metasurfaces. The amount of phase shift applied to a reflected RF wave can be altered by changing or adjusting the spacing between the conductive ground plane and the first metasurface. Therefore, the reflective properties of the first metasurface can be dynamically changed by controlling the microactuator.

[0020] The first and second metasurfaces can be spaced apart by a distance h1. The first metasurface can be spaced apart from the conductive ground plane by a distance h2. The distance h1 can be fixed, while the distance h2 can be adjusted by the microactuator across a predetermined distance range.

[0021] The microactuator can be a piezoelectric actuator. It can also be any other type of fast-switching microactuator, including (but not limited to) solenoid actuators, electroactive polymer actuators, microelectromechanical systems (MEMS), magnetically driven actuators, or micromotors. The conductive ground plane can be mounted on or connected to the microactuator such that the microactuator can move the conductive ground plane relative to the first metasurface, thereby controllably adjusting the distance h2.

[0022] The first conductive element array may be formed on or in the first dielectric substrate. The second conductive element array may be formed on or in the second dielectric substrate. These conductive elements may be formed, for example, by etching, printing, and / or micromachining.

[0023] The conductive elements of the first array may all be substantially identical. In some embodiments, the conductive elements of the first array are square patches. The conductive elements of the first array do not need to be square, but may have other shapes that can be modified to allow for any suitable geometry to achieve the desired phase shift sensitivity. The conductive elements of the first array may have a first size and a first periodicity.

[0024] The conductive elements of the second array may all be substantially identical. In some embodiments, the conductive elements of the second array are square patches. The conductive elements of the second array do not need to be square, but may have other shapes that can be modified to allow for any suitable geometry to achieve the desired phase shift sensitivity. The conductive elements of the second array may have a second size and a second periodicity.

[0025] The first and second sizes and / or the first and second periodicities may be the same or different. In some embodiments, the first size is smaller than the second size. In some embodiments, the first periodicity is smaller than the second periodicity. In some embodiments, the first size is smaller than the second size and the first periodicity is smaller than the second periodicity.

[0026] Preferably, the conductive elements of the first and second arrays are formed on the surfaces of their respective dielectric substrates facing the ground plane. This configuration provides maximum control over the phase of the reflected wave. The conductive elements of one or both of the first and second arrays can be formed on the opposing surfaces of their respective dielectric substrates, but this reduces the range of possible phase shifts and thus reduces the range of achievable beam manipulation.

[0027] The first dielectric substrate may have a thickness ranging from 0.01 wavelengths to 2 wavelengths. The first dielectric substrate may have a dielectric constant εr greater than 1, and optionally about 2.3. The conductive elements of the first array may be of any suitable thickness if the geometry of the patches is appropriately designed. The conductive elements of the first array may be square patches with a side length between 0.01 and 0.5 wavelengths; for operation at 25.5 GHz, the side length may be about 1.5 mm, optionally 1.53 mm. The conductive elements of the first array may have a periodicity between 0.01 and 0.5 wavelengths; for operation at 25.5 GHz, the periodicity may be about 1.8 mm, optionally 1.83 mm.

[0028] The second dielectric substrate may have a thickness ranging from 0.01 wavelengths to 2 wavelengths. The first dielectric substrate may have a dielectric constant εr greater than 1, and optionally about 2.3. For operation at 25.5 GHz, the conductive elements of the second array may be square patches having a side length of approximately 3 mm, between 0.01 and 0.5 wavelengths. The conductive elements of the second array may have a periodicity between 0.01 and 1.0 wavelengths; for operation at 25.5 GHz, the periodicity may be approximately 3.3 mm, optionally 3.30 mm.

[0029] The spacing h1 between the first and second metasurfaces is typically about equal to an operating half-wavelength multiple to allow for optimization and dielectric effects.

[0030] The spacing h2 between the first metasurface and the conductive ground plane can be adjusted by the microactuator at a fraction of a wavelength, ranging from 0 mm to 2 mm, or from 0 µm to 500 µm. In some embodiments, the spacing h2 can be adjusted from 25 µm to 400 µm. When the conductive elements of the first array on the first metasurface contact the conductive ground plane (h2 = 0 µm), the first metasurface becomes perfectly reflective to effectively remove the effects of the metasurface.

[0031] The microactuator can be configured to allow substantially continuous adjustment of one of the pitches h2. Alternatively, the microactuator can be configured to adjust the pitch h2 in a step-by-step manner.

[0032] The first and second arrays can take on a wide range of sizes. Generally, a larger array is preferred in view of the angle of the waves passing through the metasurfaces. In some embodiments, the arrays can be on the order of tens to tens. In some embodiments, the arrays can be on the order of hundreds to hundreds or larger.

[0033] The feed comprises a pair of switchable dipoles positioned between the first and second metasurfaces at a location corresponding to the center of one of the first and second arrays. This has the remarkable advantage of achieving beam manipulation greater than that of an earlier LWA device proposed by the inventors of this invention.

[0034] The feed can be configured as a microstrip feed or a waveguide feed.

[0035] The pair of switchable dipoles is configured such that one dipole excites one right-hand side of the LWA, while the other dipole excites one left-hand side. In this way, an LWA can be constructed such that RF current can selectively flow in two opposite directions. By selectively exciting one or the other dipole and adjusting the spacing h2 by the microactuator, beam manipulation across a range greater than that of prior art LWAs can be achieved. For example, in some embodiments, beam manipulation can be achieved through a range of at least -40° to +40° (relative to a line perpendicular to the second metasurface).

[0036] Several LWAs can be used in an array, geometrically spaced to provide, for example, ±40° sectors. In this way, five LWAs can be used to cover a radial plane around 360°.

[0037] Embodiments of the present invention provide a high-efficiency antenna device particularly suitable for mm-wave and / or megahertz applications. Because the micro-actuated tuning mechanism of the embodiments of the present invention is based on a relatively small adjustment of the spacing between the first metasurface and the conductive ground plane, and because there are no active elements in the path of the RF signals, the LWA efficiency will be very high. In some embodiments, good RF matching is achieved between 26 GHz and 28 GHz for h² values ​​up to 200 μm. This is a sufficiently wide bandwidth for use with 5G infrastructure.

[0038] From the perspective of a second-state sample, a leaky antenna device is provided, comprising: A metasurface comprising a periodic array of conductive elements, or a periodic array of apertures in a conductive layer; One conductive ground; A micro actuator; and A power supply, comprising a pair of switchable dipoles; The super-surface and the conductive ground plane are arranged in a stacked configuration and are substantially parallel to each other; The distance between the conductive ground plane and the metasurface can be adjusted by operating the microactuator; and The power supply is located between the conductive grounding surface or between the conductive grounding surface and the superstructure at a position corresponding to one of the centers of the periodic array.

[0039] This metasurface can be configured as a partially reflective surface.

[0040] The metasurface is designed to impart an engineered phase shift to RF signals when reflected from it. The amount of phase shift applied to a reflected RF wave can be altered by changing or adjusting the distance between the conductive ground plane and the metasurface. Therefore, the reflective properties of the metasurface can be dynamically changed by controlling the microactuator.

[0041] The superconducting surface and the conductive ground plane can be spaced apart by a distance h2. This distance h2 can be adjusted by the microactuator across a predetermined distance range.

[0042] The microactuator can be a piezoelectric actuator. It can also be any other type of fast-switching microactuator, including (but not limited to) solenoid actuators, electroactive polymer actuators, microelectromechanical systems (MEMS), magnetically driven actuators, or micromotors. The conductive ground plane can be mounted on or connected to the microactuator such that the microactuator can move the conductive ground plane relative to the metasurface, thereby controllably adjusting the distance h2. Alternatively, the metasurface can be mounted on or connected to the microactuator such that the microactuator can move the metasurface relative to the conductive ground plane, thereby controllably adjusting the distance h2.

[0043] The periodic array may include an array of periodic conductive elements formed on or in a dielectric substrate. These conductive elements may be formed, for example, by etching, printing, and / or micromachining. Alternatively, the periodic array may include an array of periodic apertures formed in a conductive layer. These apertures may be formed, for example, by etching and / or micromachining.

[0044] The apertures or conductive elements of the periodic array may all be substantially identical. In some embodiments, the apertures of the periodic array are substantially circular. The apertures or conductive elements of the periodic array may have other shapes that can be modified to allow any suitable geometry to achieve the desired phase shift sensitivity. The apertures or conductive elements of the periodic array may have a given size and a given periodicity.

[0045] The spacing h2 between the metasurface and the conductive ground plane can be adjusted by the microactuator at a fraction of a wavelength, ranging from 0 mm to 2 mm, or from 0 µm to 500 µm. In some embodiments, the spacing h2 can be adjusted from 25 µm to 400 µm. When the apertures or conductive elements of the periodic array on the metasurface contact the conductive ground plane (h2 = 0 µm), the metasurface becomes totally reflective to effectively remove the effects of the metasurface.

[0046] The microactuator can be configured to allow substantially continuous adjustment of one of the pitches h2. Alternatively, the microactuator can be configured to adjust the pitch h2 in a stepwise manner.

[0047] The periodic array can be of a wide range of sizes. Generally, a larger array is preferred when viewed from the angle of the waves passing through the metasurface. In some embodiments, the array can be on the order of tens to tens. In some embodiments, the array can be on the order of hundreds to hundreds or larger.

[0048] In an embodiment where the second state provided by the microactuator is fully movable, a leaky antenna device requiring only a single metasurface is achieved. This single metasurface, positioned on the conductive ground plane, defines a cavity therebetween.

[0049] The feed comprises a pair of switchable dipoles positioned between the supersurface at a location corresponding to one of the centers of the periodic array and the conductive ground plane. The feed can be configured as a microstrip feed or a waveguide feed on or within the conductive ground plane. This offers the remarkable advantage of achieving beam manipulation capabilities greater than those of earlier LWA devices proposed by the inventors of this invention.

[0050] The pair of switchable dipoles is configured such that one dipole excites one right-hand side of the LWA, while the other dipole excites one left-hand side. In this way, an LWA can be constructed such that RF current can selectively flow in two opposite directions. By selectively exciting one or the other dipole and adjusting the spacing h2 by the microactuator, beam manipulation across a range greater than that of prior art LWAs can be achieved. For example, in some embodiments, beam manipulation can be achieved through a range of at least -40° to +40° (relative to a line perpendicular to the metasurface).

[0051] Several LWAs can be used in an array, geometrically spaced to provide, for example, ±40° sectors. In this way, five LWAs can be used to cover a radial plane around 360°.

[0052] An embodiment using a switchable dipole first or second state can be configured for operation at frequencies up to 100 GHz. Simple Explanation of the Diagram

[0053] Embodiments of the present invention will be further described below with reference to the accompanying drawings, wherein: Figure 1(a) shows a unit cell of a prior art HIS under a conductive ground plane; Figure 1(b) illustrates a prior art LWA comprising an HIS disposed between a PRS and a conductive ground plane; Figure 2(a) shows the simulated S11 value response of the LWA ground plane of Figure 1(b) under different displacements; Figure 2(b) shows the simulated S11 phase response of the LWA at different ground surface displacements in Figure 1(b); Figure 3 shows the beam scanning achieved by LWA in Figure 1(b); Figure 4 illustrates a printed dipole antenna (PDA) suitable for use with the LWA of Figure 1(b) and also with embodiments of the present invention; Figure 5(a) shows the simulated S11 response of the PDA in Figure 4 of the LWA in Figure 1(b) to different displacements of the ground plane; Figure 5(b) shows the simulated far-field radiation pattern of the PDA in Figure 4 of the LWA in Figure 1(b) for different displacements of the ground plane; Figure 6 illustrates an alternative to the prior art LWA, which includes a metal PRS with a circular aperture and no HIS. Figure 7(a) shows the simulated far-field radiation pattern of LWA in Figure 6; Figure 7(b) shows the simulated S11 response of LWA in Figure 6; Figure 8 illustrates one embodiment of the LWA of the present invention; Figure 9 shows the simulated far-field gain (absolute) of LWA in Figure 8 at phi = 90° for different displacements of the ground plane; Figure 10 shows the simulated far-field radiation pattern of the LWA in Figure 8 at 25.5 GHz in the E-plane at zero displacement of the ground plane; Figure 11(a) shows a front view of one of the bidirectional switchable printed dipole feeds; Figure 11(b) shows a first detail of one of the dipole feeding methods in Figure 11(a); Figure 11(c) shows a second detail of one of the dipole feeding methods in Figure 11(a); and Figure 12 shows a rear view of one of the dipole feeds in Figure 11(a). Implementation

[0054] Figure 8 illustrates one embodiment of the LWA of the present invention. Similar to the LWA of Figure 1(b), the LWA includes a tunable high impedance surface (HIS) 1, each formed as a supersurface and arranged substantially parallel to each other, and a static partially reflective surface (PRS) 2. The LWA illustrated in the figure is configured to operate at 26 GHz to 28 GHz, but can be configured to operate at other GHz frequencies as needed. HIS 1 and PRS 2 are each formed from a two-dimensional array of conductive patch elements etched onto a planar dielectric PCB substrate 100, 200. The substrates 100, 200 may each include a Rogers RT / Duroid 5880 substrate having a dielectric constant εr = 2.2, a thickness of about 0.8 mm, and a copper cladding layer having a thickness of about 0.035 mm, although these measurements are merely illustrative and non-limiting. HIS 1 is etched to define a first two-dimensional array of conductive patch elements 4. PRS 2 is etched to define a second two-dimensional array of conductive patch elements 5. HIS 1 is positioned substantially parallel to and above a conductive ground plane 3, with a distance h 2 between HIS 1 and the ground plane 3. PRS 2 is positioned on HIS 1 and with a distance h 1 between HIS 1 and the ground plane 3. The distance h 1 defines a cavity height of LWA and determines a resonant frequency of LWA. Ground plane 3 is mounted on a piezoelectric actuator 6 and can be vertically displaced by the piezoelectric actuator 6 to allow variation of the distance h 2.

[0055] A key difference from the prior art LWA of Figure 1(b) is that the feed antenna, instead of being positioned near an edge of the LWA, includes a pair of switchable dipole feeds 150 positioned between HIS 1 and PRS 2 at a location corresponding to the center of the first and second arrays. By employing a pair of switchable dipoles at this location, a significant increase in the beam control angle θ is achieved, in this example, ±40° relative to a direction perpendicular to PRS 2.

[0056] The feed 150, shown in more detail in Figures 11 and 12 and further described below, is configured to selectively excite the LWA structure to increase the available beam scanning range.

[0057] Metamaterial devices can be designed to reflect waves when an engineered phase shift is applied. This can be achieved using a high-impedance surface consisting of a periodic metal patch printed on a dielectric substrate suspended on a ground plane. By changing the distance between the periodic array and the ground plane, the amount of phase shift applied to a reflected wave can be altered. Therefore, the reflective properties of the high-impedance surface can be dynamically changed using a piezoelectric actuator (or other fast-switching microactuator).

[0058] As shown in Figure 8, if this HIS 1 is integrated into a leaky antenna (using an engineered partial reflective surface (PRS) 2) and fed from a center with a switchable dipole 150, a highly directional antenna can be obtained that can efficiently control its main radiating beam at millimeter-wave frequencies where other competing technologies typically increase losses.

[0059] Because the tuning mechanism in this invention represents only a slight adjustment in height and has no active elements within the RF path itself, micro-actuated tuning provides best-in-class efficiency. For example, the embodiment of Figure 8 has proven to provide excellent RF matching between approximately 26 GHz and approximately 28 GHz for distances up to 0.32 mm h². This is a sufficiently wide bandwidth for state-of-the-art communication systems used in 5G infrastructure.

[0060] By positioning a pair of switchable dipoles 150 within a metamaterial stack, a further switching element can be generated on either the right or left portion of the excited antenna to produce the beam control performance shown in Figure 9, which illustrates the far-field gain (absolute) (phi = 90°) at various distances h² from 0.0 mm to 0.32 mm, and on either the right or left portion of the excited antenna with the switchable dipole-fed 150. A beam angle between ±40° is feasible, enabling 5G infrastructure to direct data toward individual consumers as they move within the service area of ​​the antenna system with a specific beam angle.

[0061] Figure 10 shows the simulated far-field radiation pattern of the LWA of Figure 8 in the E-plane at 25.5 GHz (i.e., 26 GHz) at zero displacement (h 2 = 0.0 mm) of the ground plane. The E-plane is perpendicular to the H-plane shown in Figure 9, which is the plane in which beam manipulation occurs. The main lobe magnitude is 19 dBi in one direction of 1.0°. The angular width (3 dB) is 18.7° and the sidelobe level is -12.3 dB.

[0062] The table below shows the simulated performance results of the beam-controlled antenna at 26 GHz: h 2(mm) Active power supply Peak gain (dBi) Peak gain angle (ᵒ) HPBW (ᵒ) 0.0 right+left (center) 19 0 12.8 0.05 right / left 18.8 -7 / +7 12.4 0.1 right / left 21.3 -12 / +12 8.1 0.2 right / left twenty two -22 / +22 7.2 0.3 right / left 19.6 -35 / +35 6.3 0.32 right / left 18.7 -39 / +39 7.5

[0063] These devices are compatible with the electromagnetic requirements of 5G systems.

[0064] By providing a feed in the form of a pair of switchable dipoles at the center of the leaky antenna, different parts of the leaky antenna can be selectively excited, thus extending the possible beam scanning angle and resulting in a more commercially viable device.

[0065] Figure 11(a) shows a front view of an exemplary bidirectional switchable printed dipole feed, typically indicated by 150. The feed 150 comprises conductive tracks printed on the front surface of a dielectric substrate 200, one end of which includes an RF connector 201. In the configuration shown, the dielectric substrate 200 is a 0.254 mm thick RT / Duroid 5880 substrate, but it should be understood that other suitable dielectric substrates may also be used. A feed line 202 extends from the RF connector 201 via a bias network 203 toward this location, pointing back to the front surface dipole arms 204a, 204b of the RF connector 201. The front surface dipole arms 204a, 204b are shown in more detail in Figure 11(c).

[0066] In the bias network 203, shown in more detail in Figure 11(b), a capacitor 205 is provided to prevent the DC bias current supplied at V1 from flowing back to the RF connector 201. An inductor 206 is provided between V1 and the feed line 202 to prevent RF current from flowing back to the DC bias circuit. A resistor 208 is included in the bias network 203 to control the DC bias current to an appropriate level for connecting the feed line 202 to one of the phase-shifting switch (pin) diodes 207a, 207b of the front-surface diode arms 204a, 204b. The DC bias current is terminated at V2 or V3 by inductors 209, 210 and resistors 211, 212, respectively, as shown in Figure 11(c).

[0067] As shown in Figure 12, a ground strip 213 is provided on the rear surface of the dielectric substrate 200. The ground strip 213 follows the path of the feed line 202 and includes rear surface dipole arms 214a, 214b, shown here pointing away from the RF connector 201. The ground strip 213 is positioned at a quarter-wavelength distance from the feed line 202 and acts as a reflector to guide the dipole antenna radiation along the y-axis.

[0068] On one hand, the respective front and rear surface dipole arms 204a and 214a, and on the other hand, dipole arms 204b and 214b define a pair of dipoles disposed on both sides of the feed line 202 and the ground strip line 213. Depending on the operation of the phase-shifting diodes 207a and 207b, the dipoles can be excited individually or together. For example, if the phase-shifting diode 207a is switched to allow current to pass through the front surface dipole arm 204a, the dipole formed by the front surface dipole arm 204a and the rear surface dipole arm 214a is excited and can radiate. Similarly, if the phase-shifting diode 207b is switched to allow current to pass through the front surface dipole arm 204b, the dipole formed by the front surface dipole arm 204b and the rear surface dipole arm 214b is excited and can radiate. If only one of the dipoles is excited and radiates, the corresponding side (positive or negative y-axis) of the beam control LWA is determined. If both dipoles are excited and radiate, the beam will be a central beam.

[0069] The printed dipole feed 150 shown in the figure allows the S11 return loss to remain below 10 dB, where the radiating main beam is directed to the left, right, or center depending on whether one or both of the phase-shifting diodes 207a and 207b are on. Once an appropriate state of the phase-shifting diodes 207a and 207b is set for a desired beam orientation, i.e., by varying the bias voltage of the piezoelectric actuator 6 to adjust the spacing h2, HIS 1 is tuned to control the LWA main beam to a desired pointing angle.

[0070] The printed dipole feed 150 shown in Figures 11 and 12 is merely illustrative, and other configurations are possible.

[0071] Throughout the description and claims of this specification, the terms "comprising" and "containing," and variations thereof, mean "including (but not limited to)" and are not intended (and do not exclude) other parts, additions, components, wholes, or steps. In the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. Specifically, where the indefinite article is used, the specification should be understood to be prudently considered in terms of both the plural and singular forms unless the context otherwise requires.

[0072] Unless incompatible with it, any feature, integral, characteristic, compound, chemical part, or group described in connection with a particular aspect, embodiment, or example of the invention should be understood to be applicable to any other aspect, embodiment, or example described herein. Except for at least some mutually exclusive combinations of such features and / or steps, all features disclosed in this specification (including any appended claims, abstracts, and drawings) and / or all steps of any method or procedure so disclosed may be combined in any combination. The invention is not limited to the details of any of the foregoing embodiments. The invention extends to any novel one or any novel combination of the features disclosed in this specification (including any appended claims, abstracts, and drawings), or to any novel one or any novel combination of the steps of any method or procedure so disclosed.

[0073] The reader’s attention is directed to all papers and documents filed concurrently with or prior to this specification, which are available for public examination together with this specification, and the contents of all such papers and documents are incorporated herein by reference.

[0074] 1: Tunable High Impedance Surface (HIS) 2: Static Partial Reflective Surface (PRS) 3: Conductive grounding 4: Conductive Patch Components 5: Conductive Patch Components 6: Piezoelectric actuator 7: Reflector 8: Printed dipole-fed antenna 10: Circular aperture periodic static partial reflective surface (PRS) 11: Circular aperture 12: Waveguide-fed slot element 100:Substrate 150: Power supply 200:Substrate 201: Radio Frequency (RF) Connector 202: Feeder 203: Bias Network 204a: Front surface dipole arm 204b: Front surface dipole arm 205: Capacitor 206: Inductor 207a: Phase-shifting switch diode 207b: Phase-shifting switch diode 208: Resistor 209: Inductor 210: Inductor 211: Resistor 212: Resistor 213: Grounding strip wire 214a: Rear surface dipole arm 214b: Rear surface dipole arm h 1: Thickness / Distance h 2: Distance / Displacement / Ground Distance h 3: Distance / Resonant Cavity Height / Cavity Height t: thickness εr: Dielectric constant θ: Beam control angle

Claims

1. A leaky antenna device, comprising: A first metasurface, comprising a first dielectric substrate having a first array of conductive elements; A second metasurface includes a second dielectric substrate having a second array of conductive elements; a conductive ground plane; a microactuator; and a power supply including a pair of switchable dipoles; wherein the first and second metasurfaces and the conductive ground plane are stacked and substantially parallel to each other, wherein the first metasurface is located between the second metasurface and the conductive ground plane; wherein a spacing between the conductive ground plane and the first metasurface is adjustable by operation of the microactuator; and wherein the power supply is disposed between the first and second metasurfaces at a position corresponding to the center of one of the first and second arrays.

2. The antenna device of claim 1, wherein the first metasurface is configured as a high-impedance surface.

3. The antenna arrangement of claim 1 or 2, wherein the second metasurface is configured as a portion of the reflective surface.

4. A leaky antenna device, comprising: A metasurface comprising a periodic array of conductive elements, or a periodic array of apertures in a conductive layer; a conductive ground plane; A micro actuator; And a power supply including a pair of switchable dipoles; wherein the supersurface and the conductive ground plane are stacked and substantially parallel to each other; wherein a gap between the conductive ground plane and the supersurface can be adjusted by operation of the microactuator; and wherein the power supply is disposed on the conductive ground plane or at a position corresponding to one of the centers of the periodic array between the conductive ground plane and the supersurface.

5. The antenna device as claimed in items 1, 2 or 4, wherein the microactuator is a piezoelectric actuator.

6. The antenna device as claimed in claim 1, 2 or 4, wherein the microactuator is a fast-switching microactuator, such as a solenoid actuator, an electroactive polymer actuator, a microelectromechanical system actuator, a magnetically driven actuator or a micro motor.

7. An antenna device as claimed in claim 1, 2 or 4, wherein the pair of switchable dipoles is configured such that one of the dipoles excites a first side of the antenna device relative to the center and the other dipole excites a second side of the antenna device relative to the center.

8. The antenna arrangement of claim 7, wherein the pair of switchable dipoles is configured to excite RF currents that flow selectively in two opposite directions.

9. An antenna device as claimed in claims 1, 2 or 4, configured to manipulate a beam relative to a line perpendicular to the metasurface within a range of at least -40° to +40° by selectively stimulating one or the other of the pair of switchable dipoles and by adjusting the spacing between the metasurface and the conductive ground plane by the microactuator.

10. The antenna device as claimed in claim 1, 2 or 4, wherein the microactuator is configured to move the metasurface.

11. The antenna device as claimed in claim 1, 2 or 4, wherein the microactuator is configured to move the conductive ground plane.

12. The antenna apparatus of claim 1, 2 or 4, wherein the feed includes a feed line disposed on a front surface of a dielectric substrate, wherein first and second front surface dipole arms extend on either side of the feed line, and a ground strip line disposed on a rear surface of the dielectric substrate, following a path defined by the feed line on the first surface of the dielectric substrate, wherein the first and second rear surface dipole arms extend on either side of the ground strip line, the first front surface dipole arm and the first rear surface dipole arm together form a first dipole on one side of the feed, and the second front surface dipole arm and the second rear surface dipole arm together form a second dipole on the other side of the feed.

13. The antenna arrangement of claim 12, wherein the first front surface dipole arm is connected to the feed line by a first switchable diode, and wherein the second front surface dipole arm is connected to the feed line by a second switchable diode.

14. The antenna arrangement of claim 13, wherein the first and second switchable diodes are operable to allow the first dipole and the second dipole to be excited together or individually.

15. A composite antenna comprising a plurality of antenna devices as claimed in any one of claims 1 to 14.

16. The composite antenna of claim 15, wherein the plurality of antenna devices are arranged to face different directions.

17. The composite antenna of claim 15, wherein the plurality of antenna devices are arranged to face the same direction.

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