Metamaterial-enabled beam-steering antennas

Abstract

A leaky-wave antenna device is disclosed that includes a first metasurface that includes a first dielectric substrate having a first array of conductive elements, and a second metasurface that includes a second dielectric substrate having a second array of conductive elements. The antenna device further includes a conductive ground plane, a microactuator, and a feed that includes a pair of switchable dipoles. The first and second metasurfaces and the conductive ground plane are substantially parallel to each other in a stacked arrangement, and the first metasurface is disposed 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 disposed between the first metasurface and the second metasurface at a location corresponding to a center of the first and second arrays. The leaky-wave antenna device is operable to steer a beam over a wide range by selectively energizing the pair of dipoles and 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 a meta-material surface is controllably displaced relative to a ground plane to introduce a phase shift and thereby enable beam steering. [Background technology]

[0002] Beam-steerable high-gain antennas operating at millimeter-wave (mm-wave) frequencies (e.g., 30-300 GHz) are expected to play a key role in several wireless applications, including 5G and beyond, especially for maintaining wireless links in dynamic environments. However, steering antenna beams at these high frequencies is challenging because traditional phased array and beam switching techniques are limited by several factors, including loss characteristics and availability of commercially available components.

[0003] Previous work by the present inventors (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 disclosure of which is incorporated herein by reference) has led to the development of leaky-wave antennas (LWAs) that employ extremely low-loss tunable metasurfaces as phase-shifting materials to obtain beam steering capabilities.

[0004] LWA is a type of traveling wave antenna that should be distinguished from more conventional resonant antennas such as monopoles or dipoles. In an LWA, the radio frequency (RF) current that creates the transmitted radio signal travels in one direction along the antenna. This is in contrast to a resonant antenna, where the RF current travels in both directions along the antenna and bounces between the ends. The traveling waves in an LWA are typically fast waves with a phase velocity faster than the speed of light.

[0005] A metasurface in the context of this application is a thin sheet of material (of thickness less than the wavelength of the RF signal being modulated by the metasurface) that has a periodic array of scattering elements whose dimensions and period are small compared to the operating wavelength. A typical metasurface comprises a thin dielectric substrate of thickness <1 mm with a two-dimensional array of conductive metal elements printed or etched onto the substrate, where the conductive elements may have a size on the order of millimeters.

[0006] Previous work by the inventors discloses two different LWA designs.

[0007] The first LWA design, shown in FIG. 1(b), is based on a tunable high impedance surface (HIS) 1 and a static partially reflective surface (PRS) 2, each formed as a metasurface and arranged approximately parallel to each other. The first LWA design is configured to operate at 37 GHz. As shown in FIG. 1(b), HIS1 and PRS2 are each formed by a two-dimensional array of square conductive patch elements etched on a planar printed circuit board (PCB). HIS1 and PRS2 are each formed by a two-dimensional array of square conductive patch elements etched on a planar printed circuit board (PCB) with a copper cladding of thickness t=0.035 mm and a dielectric constant ε r = 2.2, thickness h 1 The HIS1 has a Rogers RT / Duroid 5880 substrate with a thickness of h = 0.787 mm. 1 The PRS2 are etched to define a two-dimensional array of square conductive patch elements 4, each having sides of length 1.53 mm and a periodicity of 1.83 mm, on a first dielectric substrate 100 of 1. 1 A two-dimensional array of square conductive patch elements 5 having sides of 3 mm length and a periodicity of 3.3 mm is etched onto the second dielectric substrate 200 of FIG. 1. HIS1 is disposed substantially parallel to and above the conductive ground plane 3, and HIS1 is disposed a distance h above the ground plane 3. 2 The PRS2 is disposed over the HIS1 and is spaced apart from the HIS1 by a distance h 3 They are spaced apart by a distance h 3defines the cavity height of the LWA and determines the resonant frequency of the LWA. The total area of ​​the HIS / PRS assembly is approximately 3 cm x 9 cm. The ground plane 3 is mounted on the piezoelectric actuator 6 and is spaced at a distance h 2 1(a) shows an isolated unit cell of the HIS1 of FIG. 1(b), but upside down with respect to FIG. 1(b). The unit cell comprises a single square conductive patch element 4 on a first dielectric substrate 100. A conductive ground plane 3 is disposed at a distance h from the first dielectric substrate 100. 2 are spaced apart by.

[0008] The corresponding ends of HIS1 and PRS2 are joined on one side of the LWA by a reflector 7, and a printed dipole feed antenna 8 is provided adjacent the reflector 7 between HIS1 and PRS2.

[0009] Figures 2(a) and 2(b) show the various displacements of the LWA in Figure 1(b) operating in the frequency band from 35 GHz to 40 GHz. 2 The simulated HIS reflection coefficient for 11 Amplitude and S 11 The phase response is shown. 2 can vary from 0 μm to 400 μm. A change of 40 μm to 400 μm (Δh 2 = 360 μm), at 37 GHz, approximately

[0010]

number

[0011] of

[0012]

number

[0013] It can be seen that the HIS1 exhibits a negligible loss of about 0.06 dB while a phase shift in the reflection coefficient of the HIS1 is generated. 2 A curvature-amplified piezoelectric actuator 6 can be employed to adjust the S. Similarly, the simulated S of PRS2 11 Absolute amplitude (R) and

[0014]

number

[0015] can be obtained, which are 0.94 and 156°, respectively, at 37 GHz. The directivity and main beam angle of the LWA are the S of both HIS1 and PRS2 according to the following equation: 11 Depends on the response.

[0016]

number

[0017] where F(θ) is the radiated power pattern of the feed element and λ is the operating wavelength. The phase shift provided by HIS1 is given by:

[0018]

number

[0019] Here, φ t is the phase shift applied to the wave as it passes through the patterned metal surface.

[0020] As shown in Figure 3, using equations (1) and (2), the LWA is

[0021]

number

[0022] is predicted to exhibit a beam steering range of approximately 37° (14° to 51°).

[0023] The piezoelectric actuator 6 may comprise a linear piezoelectric actuator with curvature amplification and may provide a displacement of up to 0.5 mm. The piezoelectric actuator 6, on which the ground plane 3 is disposed, scales depending on the applied DC bias voltage and therefore provides a displacement h as required. 2 It may be possible to vary

[0024] As shown for example in Figure 4, the printed dipole antenna 8 of the LWA is a half-wave antenna designed to operate at 37 GHz. The directivity of the printed dipole antenna 8 is enhanced by placing a reflector 7 0.9 mm from the back side of the antenna 8 (see Figure 1(b)). By implementing the printed dipole antenna 8 in a LWA with 9 x 27 PRS elements and 16 x 49 HIS elements and running suitable simulations centered around the operating frequency of 37 GHz, the h 2 The S shown in Fig. 5(a) for different values ​​of 11 Responses are provided. 2 The far field radiation pattern (FRP) in the H-plane at 37 GHz for the S 11 The response remains below -10 dB at about 37 GHz for various displacements. The maximum gain of the LWA is 40 μm to 400 μm. 2 The change in the beam width is 23.9 dBi at maximum beam steering of 33° at 37 GHz.

[0025] A second LWA design, shown in Fig. 6, is proposed for the low THz band (e.g., around 280 GHz). To reduce the structural complexity, this second LWA design comprises a periodic PRS 10 with a circular aperture and omits the HIS close to the ground plane 3. In this variant, the PRS 10 is displaced perpendicular to the ground plane 3 by a piezoelectric actuator 6, thus reducing the resonant cavity height h 3The PRS 10 has a thickness of h 2 and a two-dimensional 11×31 array of circular apertures 11, each 0.6 mm in diameter and with a periodicity of 0.75 mm. 1 = 0.3 mm. The metal ground plane 3 has a thickness h 2 , the PRS 10 is disposed at a distance of 0.46 mm above the ground plane 3, and the cavity height h 3 is the cavity height h by applying different DC bias currents to the piezoelectric actuator 6. 3 The thickness h can be varied between 0.44mm and 0.5mm. 2 is typically on the order of a few millimeters to provide a stable base and sufficient support for a standard waveguide feed flange. 2 is thicker than a skin depth, ideally thicker than two skin depths. The LWA is excited by a waveguide-fed slot element 12 formed towards one end of the ground plane 3. Embodiments with or without the HIS1 near the ground plane 3 can be designed at least for frequencies between 20 GHz and 1 THz.

[0026] Figures 7(a) and 7(b) show the simulation results for the second LWA design operating at 280 GHz, where Figure 7(a) shows the FRP in the H-plane and Figure 7(b) shows the S 11 The response is shown in each case as h 3 It can be seen that the LWA has a maximum gain of 18 dBi and provides beam steering over a range of about 18°, with a 3 dB gain loss over a 0.06 mm range of displacement. However, 11 It can be seen that the response rises from -10 dB for some displacement. [Prior art documents] [Non-patent literature]

[0027] [Non-Patent Document 1] 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. Summary of the Invention [Problem to be solved by the invention]

[0028] While previous work by the inventors has shown that beam steering is possible, there remains room for improvement. [Means for solving the problem]

[0029] From the first aspect, 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; a conductive ground plane; A microactuator; A feed section including a pair of switchable dipoles; Equipped with the first and second metasurfaces and the conductive ground plane are substantially parallel to one another in a stacked arrangement, the first metasurface being disposed between the second metasurface and the conductive ground plane; a spacing between the conductive ground plane and the first metasurface is adjustable by actuation of the microactuator; A leaky-wave antenna device is provided in which a feed is disposed between the first and second metasurfaces at a location corresponding to the centers of the first and second arrays.

[0030] The first metasurface can be configured as a high impedance surface.

[0031] The second metasurface can be configured as a partially reflective surface.

[0032] The first and second metasurfaces are designed to impart a designed phase shift to an RF signal when such signal is reflected by the respective metasurface. By varying or adjusting the spacing between the conductive ground plane and the first metasurface, it is possible to vary the amount of phase shift imparted to the reflected RF wave. Thus, by controlling the microactuator, it is possible to dynamically change the reflective properties of the first metasurface.

[0033] The first and second metasurfaces are spaced apart by a distance h 1 The first metasurface may be spaced apart from one another by a distance h 2 may be separated from the conductive ground plane by a distance h 1 may be fixed, while the distance h 2 is adjustable over a predefined range of distances by a microactuator.

[0034] The microactuator may be a piezoelectric actuator. The microactuator may be any other type of fast switching microactuator, including but not limited to a solenoid actuator, an electroactive polymer actuator, a microelectromechanical system, a magnetically driven actuator, or a micromotor. The microactuator moves the conductive ground plane relative to the first metasurface, thereby moving a distance h 2 A conductive ground plane can be attached or connected to the microactuator so that the impedance can be controllably adjusted.

[0035] A first array of conductive elements can be formed on or in a first dielectric substrate. A second array of conductive elements can be formed on or in a second dielectric substrate. The conductive elements can be formed, for example, by etching, printing, and / or micromachining.

[0036] The first array of conductive elements may all be substantially identical. In some embodiments, the first array of conductive elements is a square patch. The first array of conductive elements need not be square, but may have other shapes of any suitable geometry that can be altered to enable the required phase shift sensitivity. The first array of conductive elements may have a first size and a first periodicity.

[0037] The second array of conductive elements may all be substantially identical. In some embodiments, the second array of conductive elements is a square patch. The second array of conductive elements need not be square, but may have other shapes of any suitable geometry that can be altered to enable the required phase shift sensitivity. The second array of conductive elements may have a second size and a second periodicity.

[0038] 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.

[0039] Preferably, the first and second arrays of conductive elements are formed on the surface of the dielectric substrate of each array that faces the ground plane. This arrangement provides the greatest control over the phase of the reflected wave. It is possible to form the conductive elements of one or both of the first and second arrays on both sides of each dielectric substrate, but this may reduce the range of possible phase shifts and therefore the range of beam steering that can be obtained.

[0040] The first dielectric substrate may have a thickness in the range of 0.01 to 2 wavelengths. The first dielectric substrate has a dielectric constant ε greater than 1, optionally about 2.3. rThe first array of conductive elements may have a thickness of any suitable thickness if the geometry of the patch is suitably designed. The first array of conductive elements may be a square patch with a side length between 0.01 and 0.5 wavelengths, and for operation at 25.5 GHz, the side length may be about 1.5 mm, optionally 1.53 mm. The first array of conductive elements may have a periodicity between 0.01 and 0.5 wavelengths, and for operation at 25.5 GHz, the periodicity may be about 1.8 mm, optionally 1.83 mm.

[0041] The second dielectric substrate may have a thickness in the range of 0.01 to 2 wavelengths. The second dielectric substrate has a dielectric constant ε greater than 1, optionally about 2.3. r The second array of conductive elements may be a square patch with a side length between 0.01 and 0.5 wavelengths, optionally about 3 mm for operation at 25.5 GHz. The second array of conductive elements may have a periodicity between 0.01 and 1.0 wavelength, optionally about 3.3 mm for operation at 25.5 GHz, optionally about 3.30 mm.

[0042] The spacing h between the first and second metasurfaces 1 is typically approximately equal to a multiple of the half wavelength of operation to allow for optimization and dielectric effects.

[0043] The spacing h between the first metasurface and the conductive ground plane 2 can be adjusted by a microactuator to a fraction of a wavelength, optionally between 0 mm and 2 mm, optionally between 0 μm and 500 μm. In some embodiments, the spacing h 2 can be adjusted to be between 25 μm and 400 μm. When the first array of conductive elements on the first metasurface contacts the conductive ground plane (h 2 = 0 μm), the first metasurface becomes fully reflective, effectively eliminating the effect of the metasurface.

[0044] The microactuators are spaced apart by h 2Alternatively, the microactuator can be configured to allow for nearly continuous adjustment of the interval h 2 can be configured to adjust in a stepwise manner.

[0045] The first and second arrays can have a wide range of array sizes. In general, it is preferable for the arrays to be large from the perspective of waves passing through the metasurface. In some embodiments, the arrays may be on the order of tens by tens. In some embodiments, the arrays may be on the order of hundreds by hundreds or even larger.

[0046] The feed comprises a pair of switchable dipoles disposed between the first and second metasurfaces at locations corresponding to the centers of the first and second arrays, which provides the surprising advantage of enabling a wider range of beam steering than previous LWA devices proposed by the inventors.

[0047] The feed may be configured as a microstrip feed or a waveguide feed.

[0048] The switchable dipole pair is configured such that one of the dipole pair excites the right hand side of the LWA and the other of the dipole pair excites the left hand side of the LWA. In this manner, the LWA can be constructed such that RF current can selectively flow in two opposite directions. By selectively energizing one or the other of the switchable dipole pair and by the microactuator, the spacing h 2 By adjusting the second metasurface, it is possible to achieve beam steering over a wider range than in prior art LWAs. For example, in some embodiments, beam steering over a range of at least -40° to +40° (relative to a line normal to the second metasurface) is achievable.

[0049] Several LWAs can be used, geometrically spaced in an array to achieve, for example, a sector of ±40°. In this way, five LWAs can be used to cover 360° around one radiating surface.

[0050] The embodiments of the present disclosure provide highly efficient antenna devices that are particularly suitable for mm-wave and / or terahertz applications. The microactuated tuning mechanism of the embodiments of the present disclosure is based on a relatively small adjustment of the spacing between the first metasurface and the conductive ground plane, and there are no active elements in the path of the RF signal, making the LWA highly efficient. In some embodiments, the LWA can achieve a h of up to 200 μm. 2 For values, a good RF match is obtained between 26 GHz and 28 GHz, which is a wide enough bandwidth for use in 5G infrastructure.

[0051] From the second aspect, a metasurface comprising a periodic array of conductive elements or a periodic array of openings in a conductive layer; a conductive ground plane; A microactuator; A feed section including a pair of switchable dipoles; Equipped with the metasurface and the conductive ground plane are approximately parallel to one another in a stacked arrangement; the spacing between the conductive ground plane and the metasurface is adjustable by actuation of the microactuator; A leaky-wave antenna device is provided in which a feed is disposed on a conductive ground plane or between a conductive ground plane and the metasurface at a location corresponding to the center of the periodic array.

[0052] The metasurface can be configured as a partially reflective surface.

[0053] The metasurface is designed to impart a designed phase shift to an RF signal when such signal is reflected by the metasurface. By varying or adjusting the spacing between the conductive ground plane and the metasurface, it is possible to vary the amount of phase shift imparted to the reflected RF wave. Thus, by controlling the microactuators, it is possible to dynamically change the reflective properties of the metasurface.

[0054] The metasurface and the conductive ground plane are separated by a distance h 2 The distance h 2 is adjustable over a predefined range of distances by a microactuator.

[0055] The microactuator may be a piezoelectric actuator. The microactuator may be any other type of fast switching microactuator, including but not limited to a solenoid actuator, an electroactive polymer actuator, a microelectromechanical system, a magnetically driven actuator, or a micromotor. The microactuator moves a conductive ground plane relative to the metasurface, thereby moving a distance h 2 A conductive ground plane can be attached or connected to the microactuator so that the distance h can be controllably adjusted. Alternatively, the microactuator can move the metasurface relative to the conductive ground plane, thereby adjusting the distance h 2 The metasurface can be attached or connected to a microactuator so that the surface area can be controllably tuned.

[0056] The periodic array can comprise a periodic array of conductive elements formed on or in the dielectric substrate. The conductive elements can be formed, for example, by etching, printing, and / or micromachining. Alternatively, the periodic array can comprise a periodic array of openings formed in the conductive layer. The openings can be formed, for example, by etching and / or micromachining.

[0057] 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 of any suitable geometry that can be altered to allow the required phase shift sensitivity. The apertures or conductive elements of the periodic array may have a given size and a given periodicity.

[0058] The spacing h between the metasurface and the conductive ground plane 2 can be adjusted by a microactuator to a fraction of a wavelength, optionally between 0 mm and 2 mm, optionally between 0 μm and 500 μm. In some embodiments, the spacing h 2 can be adjusted to be between 25 μm and 400 μm. When the periodically arranged apertures or conductive elements on the metasurface contact a conductive ground plane (h 2 = 0 μm), the metasurface becomes completely reflective, effectively eliminating the effect of the metasurface.

[0059] The microactuators are spaced apart by h 2 Alternatively, the microactuator can be configured to allow for nearly continuous adjustment of the interval h 2 can be configured to adjust in a stepwise manner.

[0060] The periodic arrays can take on a wide range of array sizes. In general, larger arrays are preferred from the perspective of waves passing through the metasurface. In some embodiments, the arrays may be on the order of tens by tens. In some embodiments, the arrays may be on the order of hundreds by hundreds or even larger.

[0061] An embodiment of the second aspect in which sufficient motion is achieved by a microactuator enables a leaky-wave antenna device in which a single metasurface is required: a single metasurface disposed over a conductive ground plane to define a cavity therebetween.

[0062] The feed comprises a pair of switchable dipoles disposed between the metasurface and a conductive ground plane at a location corresponding to the center of the periodic array. The feed can be configured on or in the conductive ground plane as a microstrip feed or a waveguide feed. This has the surprising advantage of enabling a wider range of beam steering than previous LWA devices proposed by the inventors.

[0063] The switchable dipole pair is configured such that one of the dipole pair excites the right hand side of the LWA and the other of the dipole pair excites the left hand side of the LWA. In this manner, the LWA can be constructed such that RF current can selectively flow in two opposite directions. By selectively energizing one or the other of the switchable dipole pair and by the microactuator, the spacing h 2 By adjusting the angle, it is possible to achieve beam steering over a wider range than in prior art LWAs. For example, in some embodiments, beam steering over a range of at least -40° to +40° (relative to a line normal to the metasurface) is achievable.

[0064] Several LWAs can be used, geometrically spaced in an array to achieve, for example, a sector of ±40°. In this way, five LWAs can be used to cover 360° around one radiating surface.

[0065] An embodiment of the first or second aspect using a switchable dipole may be configured to operate at frequencies up to 100 GHz.

[0066] Embodiments of the present invention are further described hereinafter with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0067] [Figure 1(a)] FIG. 1 illustrates a unit cell of a prior art HIS under a conductive ground plane. [Figure 1(b)]FIG. 1 illustrates a prior art LWA with a HIS disposed between a PRS and a conductive ground plane. [Figure 2(a)] FIG. 1(b) shows the simulated S11 amplitude response for different displacements of the ground plane of the LWA of FIG. [Figure 2(b)] FIG. 1(b) shows the simulated S11 phase response for different displacements of the ground plane of the LWA of FIG. [Diagram 3] FIG. 1(b) illustrates beam scanning achieved by the LWA of FIG. [Figure 4] FIG. 1(b) illustrates a printed dipole antenna (PDA) also suitable for use with the LWA of FIG. 1(b) and embodiments of the present disclosure. [Figure 5(a)] FIG. 5 shows simulated S11 responses for the PDA of FIG. 4 in the LWA of FIG. 1(b) for different displacements of the ground plane. [Figure 5(b)] FIG. 5 shows simulated long-distance radiation patterns for the PDA of FIG. 4 in the LWA of FIG. 1(b) for different displacements of the ground plane. [Figure 6] FIG. 1 shows an alternative prior art LWA with a metal PRS having a circular aperture and no HIS. [Figure 7(a)] FIG. 7 shows the simulated long-distance radiation pattern of the LWA of FIG. [Figure 7(b)] FIG. 7 shows the simulated S11 response of the LWA of FIG. [Figure 8] FIG. 1 illustrates an LWA according to an embodiment of the present disclosure. [Figure 9] FIG. 9 shows simulated long distance gain (absolute value) at phi=90° of the LWA of FIG. 8 for different displacements of the ground plane. [Figure 10] FIG. 9 shows the simulated long-distance radiation pattern of the LWA of FIG. 8 in the E-plane at 25.5 GHz at zero displacement of the ground plane. [Figure 11(a)] FIG. 1 is a front view of a bidirectional switchable printed dipole feed. [Figure 11(b)] FIG. 11(b) shows a first detail of the dipole feed of FIG. [Figure 11(c)] FIG. 11(b) shows a second detail of the dipole feed of FIG. 11(a). [Figure 12] FIG. 11(b) is a rear view showing the dipole feed unit of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0068] FIG. 8 illustrates an embodiment of the LWA of the present disclosure. Similar to the LWA of FIG. 1(b), the LWA comprises a tunable high impedance surface (HIS) 1 and a static partially reflective surface (PRS) 2, each formed as a metasurface and arranged approximately parallel to one another. The illustrated LWA is configured to operate at 26 GHz to 28 GHz, but can be configured to operate at other GHz frequencies as required. The HIS 1 and PRS 2 are each formed by a two-dimensional array of conductive patch elements etched onto a planar dielectric PCB substrate 100, 200. The substrates 100, 200 each have a copper cladding with a thickness of about 0.035 mm and a dielectric constant ε r = 2.2 and a Rogers RT / Duroid 5880 substrate having a thickness of approximately 0.8 mm, although these measurements are merely exemplary and not limiting. HIS1 is etched to define a first two dimensional array of conductive patch elements 4. PRS2 is etched to define a second two dimensional array of conductive patch elements 5. HIS1 is disposed substantially parallel to and above the conductive ground plane 3, such that HIS1 is disposed a distance h above the ground plane 3. 2 The PRS2 is disposed over the HIS1 and is spaced apart from the HIS1 by a distance h 1 They are spaced apart by a distance h 1 defines the cavity height of the LWA and determines the resonant frequency of the LWA. The ground plane 3 is mounted on the piezoelectric actuator 6 at a distance h 2 is vertically displaceable by a piezoelectric actuator 6 to enable varying

[0069] 1(b) is that instead of a feed antenna located adjacent a reflector at one end of the LWA, a feed 150 comprising a switchable dipole pair is disposed between HIS1 and PRS2 at a location corresponding to the centers of the first and second arrays. By employing a switchable dipole pair at this location, a surprising increase in the beam steering angle θ is obtained, in this example to ±40° with respect to the normal to PRS2.

[0070] A power feed 150, shown in more detail in Figures 11 and 12 and described further below, is configured to selectively energize the LWA structures to increase the available beam scanning range.

[0071] Metamaterial devices can be designed to reflect waves to which a designed phase shift is applied. This can be done using a high-impedance surface consisting of a sheet of periodic metallic patches printed on a dielectric substrate, suspended over a ground plane. By varying the separation distance between the periodic array and the ground plane, it is possible to vary the amount of phase shift imparted to the reflected wave. Thus, piezoelectric actuators (or other fast-switching microactuators) can be used to dynamically change the reflective properties of the high-impedance surface.

[0072] When such an HIS 1 is constructed into a leaky-wave antenna (using an engineered partially reflective surface (PRS) 2) and center-fed with a switchable dipole 150, as shown in FIG. 8, a highly directional antenna is obtained that can steer its main radiation beam with high efficiency at millimeter-wave frequencies where other competing technologies typically have increased losses.

[0073] The adjustment mechanism in the present disclosure provides only small adjustments in height, and due to the lack of active elements within the RF path itself, micro-actuated adjustments provide best-in-class efficiency. For example, separation distances h up to 0.32 mm 28 embodiment has been demonstrated between about 26 GHz and 28 GHz, which is a sufficiently wide bandwidth for modern communication systems used in 5G infrastructure.

[0074] By positioning switchable pairs of dipoles 150 within the metamaterial stack, it is possible to create additional switching elements that energize either the right or left portion of the antenna, creating the beam steering performance that can be seen in FIG. 9. This can be achieved with various separation distances h from 0.0 mm up to 0.32 mm. 2 , where a switchable dipole feed 150 energizes either the right or left portion of the antenna. Beam angles between ±40° are possible, allowing the 5G infrastructure to direct data to individual consumers as they move around within the coverage area of ​​a particular antenna system.

[0075] Figure 10 shows the zero displacement (h 2 9 shows the simulated far-field radiation pattern of the LWA of FIG. 8 in the E-plane at 25.5 GHz (i.e., 26 GHz) at 1.0° (A = 0.0 mm). The E-plane is perpendicular to the H-plane shown in FIG. 9, which is the plane where the beam steering is performed. The main lobe amplitude is 19 dBi at 1.0° direction. The angular width (3 dB) is 18.7° and the side lobe level is -12.3 dB.

[0076] The following table gives the results for the beam steering antenna simulation characteristics at 26 GHz.

[0077] [Table 1]

[0078] These devices meet the electromagnetic requirements of 5G systems.

[0079] By providing a feed in the form of a switchable dipole pair at the centre of the leaky-wave antenna, it is possible to selectively energise different parts of the leaky-wave antenna, thus increasing the possible beam scanning angles resulting in a more commercially practical device.

[0080] FIG. 11(a) shows a front view of an exemplary bidirectional switchable printed dipole feed, generally designated 150. The feed 150 comprises conductive tracks printed on the front surface of a dielectric substrate 200 that includes an RF connector 201 at one end. In the illustrated arrangement, the dielectric substrate 200 is a 0.254 mm thick RT / Duroid 5880 substrate, although it will be appreciated that other suitable dielectric substrates can be used. A feed line 202 runs from the RF connector 201, through a bias network 203, to front dipole arms 204a, 204b, which are here shown pointing back to the RF connector 201. The front dipole arms 204a, 204b are shown in more detail in FIG. 11(c).

[0081] A capacitor 205 is provided in the bias network 203, shown in more detail in Figure 11(b), to prevent the DC bias current provided at V1 from flowing back towards the RF connector 201. An inductor 206 is provided between V1 and the feed line 202 to prevent RF current from flowing back into the DC bias circuit. A resistor 208 is included in the bias network 203 to control the DC bias current to a suitable level for the pin diodes 207a, 207b connecting the feed line 202 to the front dipole arms 204a, 204b. Inductors 209, 210 and resistors 211, 212 allow the DC bias current to terminate at V2 or V3, respectively, as shown in Figure 11(c).

[0082] 12, a grounded stripline 213 is provided on the back surface of the dielectric substrate 200. The grounded stripline 213 follows the path of the feedline 202 and includes rear dipole arms 214a, 214b, which are shown here pointing away from the RF connector 201. The grounded stripline 213 is placed a quarter wavelength away from the feedline 202 and acts as a reflector to direct the radiation of the dipole antenna along the y-axis.

[0083] Each of the front and back dipole arms 204a, 214a on one side and 204b, 214b on the other side defines a pair of dipoles, one on each side of the feed line 202 and the grounded strip line 213. The dipoles can be energized separately or together, depending on the operation of the pin diodes 207a, 207b. For example, if the pin diode 207a is switched to allow current to flow in the front dipole arm 204a, the dipole formed by the front dipole arm 204a and the back dipole arm 214a can be energized and radiate. Similarly, if the pin diode 207b is switched to allow current to flow in the front dipole arm 204b, the dipole formed by the front dipole arm 204b and the back dipole arm 214b can be energized and radiate. If only one of the dipoles is energized and radiates, the beam is steered towards the corresponding side (positive or negative y-axis) of the LWA. When both dipoles are energized and radiate, the beam becomes a central beam.

[0084] The illustrated printed dipole feed 150 has a 11 This allows return losses to be kept below 10 dB, and the emitted main beam is directed to the left, right, or center, depending on whether one or the other or both of the pin diodes 207a, 207b are switched on. Once the suitable pin diode 207a, 207b states are set for the desired beam orientation, the separation distance h 2The bias voltage of the piezoelectric actuator 6 is changed to adjust HIS1 to steer the LWA main beam to the desired pointing angle.

[0085] The printed dipole feed 150 shown in Figures 11 and 12 is merely an example and other configurations are possible.

[0086] Throughout the description and claims of this specification, the words "comprise" and "contain" and variations thereof mean "including but not limited to" and they are not intended to (and do not) exclude other ingredients, additives, components, integers, or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless otherwise indicated. In particular, when the indefinite article is used, the specification should be understood to contemplate the plural as well as the singular, unless otherwise indicated.

[0087] It should be understood that features, integers, properties, compounds, chemical moieties, or groups described with a particular aspect, embodiment, or example of the invention are applicable to any other aspect, embodiment, or example described herein, unless incompatible. All of the features disclosed herein (including any accompanying claims, abstract, and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations in which at least some of such features and / or steps are mutually exclusive. The invention is not limited to the details of any of the above-mentioned embodiments. The invention extends to any novel, or any novel combination, of the features disclosed herein (including any accompanying claims, abstract, and drawings), or any novel, or any novel combination of the steps of any method or process so disclosed.

[0088] The reader's attention is directed to all papers and documents filed together with this application herewith or filed prior to this application and published herein, and the contents of all such papers and documents are incorporated herein by reference. [Explanation of symbols]

[0089] 1 Adjustable High Impedance Surface, HIS 2 Partially reflective surface, PRS 3 Conductive ground plane 4 Square Conductive Patch Elements 5 Square Conductive Patch Elements 6 Piezoelectric Actuator 7 reflector 8 Printed dipole antenna 10 Periodic PRS 11 Circular opening 12 Waveguide-fed slot element 100 First dielectric substrate, planar dielectric PCB substrate 150 Feed, Switchable Dipole, Printed Dipole Feed 200 Second dielectric substrate, planar dielectric PCB substrate 201 RF Connector 202 Feed line 203 Bias Network 240a front dipole arm, front diode arm 204b Front dipole arm, front diode arm 205 Capacitor 206 Inductor 207a pin diode 207b pin diode 208 Resistor 209 Inductor 210 Inductor 211 Resistor 212 resistor 213 Grounded strip line 214a Rear dipole arm 214b Rear dipole arm

Claims

1. 1. A leaky wave antenna device, 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; a conductive ground plane; A microactuator; A feed section including a pair of switchable dipoles; Equipped with the first and second metasurfaces and the conductive ground plane are substantially parallel to one another in a stacked arrangement, the first metasurface being disposed between the second metasurface and the conductive ground plane; a spacing between the conductive ground plane and the first metasurface is adjustable by actuation of the microactuator; A leaky-wave antenna device, wherein the feed is disposed between the first metasurface and the second metasurface at a location corresponding to a center 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 device of claim 1 or 2, wherein the second metasurface is configured as a partially reflective surface.

4. 1. A leaky wave antenna device, comprising: a metasurface comprising a periodic array of conductive elements or a periodic array of openings in a conductive layer; a conductive ground plane; A microactuator; A feed section including a pair of switchable dipoles; Equipped with the metasurface and the conductive ground plane are substantially parallel to one another in a stacked arrangement; a spacing between the conductive ground plane and the metasurface is adjustable by actuation of the microactuator; A leaky-wave antenna device, wherein the feed is disposed on the conductive ground plane or between the conductive ground plane and the metasurface at a location corresponding to a center of the periodic array.

5. An antenna device according to claim 1 , wherein the microactuator is a piezoelectric actuator.

6. 5. The antenna device according to claim 1, wherein the microactuator is a fast switching microactuator, such as a solenoid actuator, an electroactive polymer actuator, a microelectromechanical system actuator, a magnetic drive actuator, or a micromotor.

7. 7. The antenna device of claim 1, wherein the pair of switchable dipoles are configured such that one of the pair of dipoles excites a first side of the antenna device relative to the center and the other of the pair of dipoles excites a second side of the antenna device relative to the center.

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

9. 9. The antenna device of claim 1, configured to steer a beam over a range of at least −40° to +40° with respect to a line normal to the metasurface by selectively energizing one or the other of the pair of switchable dipoles and adjusting the spacing of the metasurface from the conductive ground plane with the microactuator.

10. The antenna device of claim 1 , wherein the microactuator is configured to move the metasurface.

11. 10. An antenna device according to claim 1, wherein the microactuator is configured to move the conductive ground plane.

12. 12. The antenna device of claim 1, wherein the feed section comprises: a feed line disposed on a front surface of a dielectric substrate, with first and second front dipole arms extending on either side of the feed line; and a grounded 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, with first and second rear dipole arms extending on either side of the grounded strip line, the first front dipole arm and first rear dipole arm together forming a first dipole on one side of the feed section, and the second front dipole arm and second rear dipole arm together forming a second dipole on the other side of the feed section.

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

14. 14. The antenna device of claim 13, wherein the first and second switchable diodes are operable to allow the first dipole and the second dipole to be energized together or separately.

15. A composite antenna comprising a plurality of antenna devices according to 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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