Lens antenna, radio unit and base station

Abstract

A lens antenna, a radio unit and a base station are disclosed. According to one embodiment, the lens antenna comprises an antenna array and a lens unit having a first focal point located at a first side of the lens unit and a second focal point located at a second side of the lens unit opposite the first side. The lens unit is capable of causing at least a portion of a beam emitted from the antenna array located at the first side of the lens unit to converge at the second side of the lens unit.

Description

TECHNICAL FIELD

[0001] Embodiments of the present disclosure generally relate to communications, and more particularly to lens antennas, radio units, and base stations. BACKGROUND

[0002] This section introduces aspects that can facilitate a better understanding of the present disclosure. Accordingly, the statements of this section are to be read in the context of this purpose, and not in a literal or restrictive sense.

[0003] For future cellular networks, such as Beyond 5th Generation (B5G) and 6th Generation (6G), wider radio bandwidths will be needed, but these wider radio bandwidths can only be found at high frequencies. In general, there is no clear boundary between low and high frequencies. However, the Third Generation Partnership Project (3GPP) has defined two frequency ranges (FRs) for New Radio (NR), FR1 and FR2. Thus, high frequencies generally mean FR2 (carrier frequencies ≥ 24.25 GHz) and even up to THz.

[0004] For example, high frequency bands ranging between 24.25 GHz and 3 THz are promising bands for B5G and 6G wireless communication systems. Short wavelengths and wider available bandwidths will increase data rates, but the utilization of these frequency spectrums will bring many challenges. One challenge is that high frequency band channels will attenuate very rapidly at tens of meters or even meters. The attenuation of high frequency band propagation waves is mainly caused by the following factors: free space path loss, molecular absorption path loss, and Mie scattering of dust, rain, water vapor, snow, or hail.

[0005] Molecular absorption has a significant impact on path loss, especially at longer distances (1-10 dB / km at frequencies up to 400 GHz). However, compared to free space loss, the molecular impact is still small. Figure 1 The impact of free space loss and molecular absorption at a distance of 10 m is shown. As Figure 1 shown, the THz radio frequency spectrum can be divided into favorable spectral windows between atmospheric absorption peaks above 500 GHz. These band windows can be easily used for high-speed B5G and 6G networks, covering up to hundreds of meters. In addition, the increase in free space loss is very small when moving forward into the THz region from 30 GHz. If the antenna area remains constant, the increase in free space loss can be compensated by the increase in antenna gain.

[0006] The physical space required for radio solutions will drastically decrease with increasing frequencies. For example, an antenna array of 1000 antenna elements will fit just in an area of less than 4 square centimeters at 250 GHz. Large antenna arrays required to compensate for the higher path loss at high frequency bands in order to achieve a suitable range for communication or sensing will result in extremely narrow cell coverage. The size of an antenna element is proportional to the wavelength and inversely proportional to the carrier frequency. Extremely small wavelengths enable extremely high antenna gains in extremely small physical dimensions.

[0007] A lens antenna is an antenna with a single or multiple lenses. A lens antenna utilizes the converging and diverging properties of a lens to transmit and receive signals. The size of a lens depends on the operating frequency. The higher the frequency, the smaller the lens. Due to this, lens antennas are typically used at high frequencies (millimeter waves and above) as lenses would be quite bulky at lower frequencies. Lenses are usually made of glass, polystyrene, artificial fluorescent resin, and polyethylene. SUMMARY

[0008] This summary is provided to introduce a selection of concepts further described below in the detailed description. This summary is not intended to determine key or essential features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter.

[0009] It is an object of the present disclosure to provide an improved lens antenna. In particular, it is an object of the present disclosure to address that existing lens antenna topologies cannot be used for mobility scenarios.

[0010] According to a first aspect of the present disclosure, a lens antenna is provided. The lens antenna can comprise an antenna array and a lens unit having a first focal point at a first side of the lens unit and a second focal point at a second side of the lens unit opposite to the first side. The lens unit can be capable of converging at least a portion of a beam transmitted from the antenna array at the first side of the lens unit at the second side of the lens unit.

[0011] In this way, the lens antenna can be used for mobility scenarios.

[0012] In embodiments of the present disclosure, the lens unit can be capable of converging at least a portion of a beam transmitted from the antenna array at the first focal point to the second focal point.

[0013] In embodiments of the present disclosure, the lens unit can be capable of converging at least a portion of a beam transmitted from a terminal device within an intended coverage range of the lens antenna to the antenna array.

[0014] In embodiments of the disclosure, a distance between the lens unit and the second focal point can be based on an intended coverage range of the lens antenna.

[0015] In embodiments of the disclosure, the lens unit can be provided with an aperture that penetrates the lens unit, such that another portion of the beam emitted from the antenna array is able to propagate through the aperture without being converged by the lens unit.

[0016] In embodiments of the disclosure, the aperture can be disposed at a center of the lens unit.

[0017] In embodiments of the disclosure, the lens unit can be one lens.

[0018] In embodiments of the disclosure, the one lens can be one of: a single refractive elliptical lens; a single refractive hyperbolic lens; a birefringent lens; and a Maxwell fish-eye lens.

[0019] In embodiments of the disclosure, the lens unit can be a combination of more than one lens.

[0020] In embodiments of the disclosure, the combination of more than one lens can be a pair of convex lenses spaced apart.

[0021] In embodiments of the disclosure, the lens antenna can operate at a frequency of 24.25 GHz or above.

[0022] According to a second aspect of the disclosure, there is provided a radio unit. The radio unit can include a lens antenna according to the first aspect described above.

[0023] According to a third aspect of the disclosure, there is provided a base station. The base station can include a radio unit according to the second aspect described above. BRIEF DESCRIPTION OF DRAWINGS

[0024] These and other objects, features and advantages of the present disclosure will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings.

[0025] Figure 1 is a graph showing the effects of free space loss and molecular absorption;

[0026] Figure 2 is a graph for explaining Snell's law;

[0027] Figure 3 is a graph showing a conventional lens antenna having a single refractive elliptical lens;

[0028] Figure 4 is a graph showing a conventional lens antenna having a single refractive hyperbolic lens;

[0029] Figure 5 is a diagram showing a conventional lens antenna having a birefringent lens;

[0030] Figure 6 is a diagram showing an application example of a conventional lens antenna;

[0031] Figure 7 is a diagram showing a disadvantage of a conventional lens antenna;

[0032] Figure 8 is a diagram showing a lens antenna according to an embodiment;

[0033] Figure 9 is a diagram showing a lens antenna according to an embodiment;

[0034] Figures 10A-10B is a diagram showing a beam shape of an antenna array;

[0035] Figure 11 is a diagram showing uplink transmission from a terminal device to an antenna array;

[0036] Figure 12 is a diagram showing uplink transmission from a terminal device to an antenna array;

[0037] Figure 13 is a diagram showing a lens antenna according to an embodiment;

[0038] Figure 14 is a diagram showing an effect of a lens antenna of Figure 13 ;

[0039] Figure 15 is a diagram showing an effect of a lens antenna of Figure 13 ;

[0040] Figure 16 is a diagram showing a lens antenna according to an embodiment;

[0041] Figure 17 is a diagram showing a lens antenna according to an embodiment;

[0042] Figure 18A is a diagram showing a lens antenna according to an embodiment;

[0043] Figure 18B is a diagram showing a coverage of an antenna array;

[0044] Figure 19 is a diagram showing an application example of a lens antenna according to an embodiment;

[0045] Figure 20 is a diagram for explaining a design of a lens antenna according to an embodiment;

[0046] Figure 21 is a diagram illustrating a lens antenna according to an embodiment; and

[0047] Figure 22 is a diagram illustrating a lens antenna according to an embodiment. DETAILED DESCRIPTION

[0048] For the purposes of explanation, specific details are set forth in the following description to provide a thorough understanding of the embodiments disclosed. However, it will be apparent to one skilled in the art that the embodiments can be practiced without these specific details or with an equivalent configuration.

[0049] Lens antennas can be classified based on three different physical characteristics. First, depending on the feeding position with respect to the lens body, lens antennas can be classified as off-body fed lens antennas or integrated lens antennas. In off-body fed lens antennas, the focal point of the lens is away from the lens and at a distance comparable to the diameter. In integrated lens antennas, the lens can have a feeding component in direct contact with the lens body. Second, depending on the refractive index profile, lens antennas can be classified as constant refractive index lens antennas, stepped refractive index lens antennas, and non-uniform refractive index lens antennas. Third, depending on the number of refractive surfaces, lens antennas can be classified as single refractive lens antennas and double refractive lens antennas.

[0050] Lens antennas can be designed by using Snell's law. As shown in Figure 2 Snell's law, assuming that the interface between two dielectrics can be locally considered as a plane, the refraction is governed by Snell's law as shown below:

[0051] n1sin(θ i )=n2sim(θ r ),

[0052] where n1and n2are the refractive indices of each medium, θ max and θ 2 are the angles of incidence and refraction defined with respect to the interface normal. According to Snell's law, if the refracted wave enters a medium with a higher refractive index, the refracted wave bends towards the surface normal, while when the refracted wave exits a medium with a higher refractive index, the refracted wave bends away from the normal.

[0053] Figure 3is a diagram illustrating a conventional lens antenna having a single refractive elliptical lens. As shown, in the elliptical lens, the surface closer to the antenna has a spherical shape and does not refract any rays. The collimation of the rays is achieved by refraction from the outer surface of the elliptical lens. Let us assume that the inner surface has a radius r1 that can be predetermined, and the shape of the outer surface can be represented by r2(0). Then, by applying the path length collimation condition shown below (that is, the time required for an electromagnetic wave to propagate through r1, l(0), and s(0) is the same as the time required for an electromagnetic wave to propagate through r1 and T), the shape of the outer surface in polar coordinates can be obtained:

[0054] r1 + nl(0) + s(0) = r1 + nT.

[0055] Note that n is the refractive index of the lens, and the time required for an electromagnetic wave to propagate through the dielectric of the lens is n times the time required for an electromagnetic wave to propagate through the same distance in a vacuum. In addition, the following physical length condition is satisfied:

[0056] (r1 + l(0)) cos 0 + s(0) = r1 + T,

[0057] r1 + l(0) = r2(0),

[0058] r1 + T = f,

[0059] where T is the thickness of the lens selected along the axis. Using the above four equations, the outer surface profile can be represented as:

[0060]

[0061] Figure 4 is a diagram illustrating a conventional lens antenna having a single refractive hyperbolic lens. As shown, in the hyperbolic lens, refraction occurs at the hyperbolic lens surface closer to the antenna. In this configuration, the outer lens surface is planar and does not refract rays. The shape of the inner surface represented by r1(0) can be similarly calculated by applying the path length collimation condition and the physical length condition.

[0062] Figure 5 is a diagram illustrating a conventional lens antenna having a double refractive lens. As shown, according to Snell’s law, a lens having two refractive surfaces allows more control over the radiation pattern characteristics. Based on the geometrical optics approach, the coordinates of the inner and outer surfaces can be determined. The main advantage of the double refractive lens over the single refractive lens is that the maximum 0 max is greater than that of the single refractive lens. As a result, the double refractive lens can support a larger steering range of the array antenna.

[0063] Figure 6is a diagram illustrating an application example of an existing lens antenna. As shown, on the transmitter side, after diverging rays are incident on and come out of the lens, the diverging rays are collimated, which forms a planar wavefront. Collimation occurs due to the refraction mechanism. On the receiver side, due to the refraction mechanism, parallel rays converge at a focal point after they have passed through the lens. Therefore, existing microwave lens antenna applications (e.g., in wireless backhaul, data center, etc.) are used for point-to-point network topologies in which a lens is placed in front of a transmitter antenna to concentrate the radiated energy into a narrow beam or focus the received energy on a receiving antenna. When the frequency increases to millimeter wave and above, the propagation of electromagnetic waves is very close to the characteristics of light.

[0064] The above conventional lens antenna solution is not beneficial for cellular network scenarios. For point-to-point network topologies, the receiving antenna is at a fixed location, and the receiving lens is placed in front of the receiving antenna and increases the receiving antenna aperture (effective antenna area). However, for 5G and 6G cellular networks, this lens antenna topology cannot be used for mobility scenarios. As shown, due to the limitation of terminal size, the lens cannot be integrated in the user terminal, and misalignment with the wavefront direction is inevitable for a mobile user. Without a receiving lens, the antenna aperture (effective antenna area) of the receiving antenna will shrink as the frequency increases. Figure 7

[0065] In addition, conventional sidelobe suppression (SLS) methods (e.g., tapering) have been implemented in almost all directional antenna systems to mitigate signal leakage in directional antennas. However, these conventional SLS methods are too complex to be implemented in practical use for large antenna arrays operating in high frequency bands. In the worst case, these suppression methods cannot completely suppress sidelobes.

[0066] The present disclosure proposes improved solutions for lens antennas, radio units, and base stations. Figure 8 is a diagram illustrating a lens antenna according to an embodiment of the present disclosure. As shown, the lens antenna includes an antenna array and a lens having a first focal point located at a first side (e.g., left side) of the lens and a second focal point located at a second side (e.g., right side) of the lens opposite to the first side. Figure 8 Figure 8 ​​the second focus (on the right side in FIG. 1). Thereafter, in the present disclosure, the first focus refers to an inner focus located on the inner side of the lens, and the second focus refers to an outer focus located on the outer side of the lens. Thus, the lens can also be referred to as a bifocal lens hereinafter. Hereinafter, the first side can also be referred to as the inner side, and the second side can also be referred to as the outer side. The lens is capable of converging at least a portion of a beam emitted from the antenna array located at the first focus to the second focus. Since the propagation path is reversible, the lens is capable of converging at least a portion of a beam emitted from a terminal device located on the second side of the lens within the intended coverage of the lens antenna to the antenna array.

[0067] As will be described later, there can be two options for the intended coverage. As a first option, the distance between the lens and the second focus can be relatively large, and this distance can be used to substantially reflect the intended coverage. In other words, the intended coverage can be based on this distance. As a second option, the distance between the lens and the second focus can be relatively small, and an angle formed between the refracted beams diverging from the second focus can be used to substantially reflect the intended coverage. In other words, the intended coverage can be based on the formed angle.

[0068] Optionally, as will be described later, the lens can be provided with an aperture that penetrates the lens, so that another portion of the beam emitted from the antenna array can propagate through the aperture without being converged by the lens. Optionally, the lens antenna can operate at high frequencies (e.g., 24.25 GHz or above). The typical lens radius that conforms to the geometric optics approximation ranges from 10 to 30 wavelengths. For example, for a frequency band of 30-300 GHz, the supported link distance is about 100 meters. For a frequency band of 28 GHz, the wavelength is about 1 centimeter, and the lens radius is about 10-30 times the wavelength, i.e., 10-30 centimeters. For a frequency band of 0.3-3 THz, the supported link distance is less than 10 meters. For a frequency band of 0.28 THz, the wavelength is about 0.1 centimeter, and the lens radius is about 1-3 centimeters. For a frequency band of 2.8 THz, the lens radius is about 1-3 millimeters. It should be noted that the lens antenna according to embodiments can also operate at other frequencies (e.g., relatively lower frequencies) at the cost of larger size and weight.

[0069] In the following, reference will be made to Figures 9-22 Several embodiments are described in detail to explain the features of the above-described lens antenna.

[0070] Figure 9 is a diagram illustrating a lens antenna according to an embodiment of the present disclosure. This embodiment corresponds to the downlink scenario and the first option for the intended coverage described above. As Figure 9As shown, a bifocal lens is placed in front of the antenna array to refract the rays and concentrate the radiated energy in the desired direction (e.g., the main lobe direction). The bifocal lens has two focal points, an inner focal point and an outer focal point. The diverging rays (main lobe and side lobes) are emitted from the inner focal point and refracted by the bifocal lens. The refracted rays converge at the outer focal point, which is located at the area to be covered (or the intended coverage area). It should be noted that only one pair of side lobes is drawn in the figure for simplicity. In reality, a large antenna array has many side lobes.

[0071] As described in the background section, the physical space required for an antenna array will drastically decrease as the frequency increases. At high frequency bands, a few square centimeters of surface area can accommodate thousands of antennas. In this case, as Figure 9 As shown, the angle between the main lobe and the refracted side lobe is very small, and thus, the main lobe and the refracted side lobe converge and overlap over a very long distance. The overlapping main lobe and side lobe can increase the downlink antenna gain.

[0072] Figures 10A-10B is a graph showing the beam shape of an antenna array. As shown, for an antenna array used for a cellular network, most of the energy (about 80-90% without employing any side lobe suppression method) is concentrated in the main lobe, which can be considered as a conical shape. However, the energy of the beam cannot be completely confined within the limits of the main lobe. Outside the main lobe, the intensity of the wave decreases rapidly, except in a few side lobes where the power increases again.

[0073] For the bifocal lens solution shown in Figure 9 , most of the side lobe energy can be concentrated by refraction. Thus, for the solution shown in Figure 9 , there is no need to perform the conventional side lobe suppression, which leads to low design complexity and also to better performance.

[0074] Assuming that the bifocal lens concentrates most of the side lobe energy (10-20% of the total transmitted power) to the main lobe steering range, which is not difficult for current optical technology. Then, with the proposed solution, the main lobe antenna downlink gain will increase by 0.46 dB to 1 dB, as calculated as follows:

[0075] 10 log ((20% + 80%) / 80%) = 1 dB,

[0076] 10 log ((10% + 90%) / 90%) = 0.46 dB.

[0077] Figure 11is a diagram showing an uplink transmission from a terminal device to an antenna array. Due to power consumption and beamforming capability limitations, the uplink beam from the terminal device is typically wide. As shown, the uplink beam emitted by the terminal device expands in space and the power density decreases. As mentioned above, at high frequency bands, the size of the antenna panel becomes very small. Therefore, the effective antenna area is much smaller than the uplink beam expansion area, which results in lower uplink reception power without a lens.

[0078] Figure 12 shows the uplink beam propagation of a conventional antenna. As shown, the effective antenna area (antenna aperture) is equal to the physical size of the antenna panel. At high frequencies, the effective antenna area is quite small. Therefore, a large portion of the uplink radiated power is not received by the receiving antenna.

[0079] In contrast, Figure 13 shows a lens antenna according to an embodiment of the present disclosure. This embodiment corresponds to the first option of the expected coverage range and the uplink scenario described above. As shown, all the rays directed to the lens can be redirected to the antenna panel. This means that the effective antenna area (antenna aperture) has the same size as the lens. Therefore, a bifocal lens can increase the effective antenna area.

[0080] The typical lens radius that fits the geometrical optics approximation ranges from 10 to 30 wavelengths. In a high frequency band example, the wavelength of the 28 GHz band is 1 cm and the wavelength of the 280 GHz band is 1 mm. The corresponding lens radii are 10 cm ~ 30 cm and 1 cm ~ 3 cm, respectively. Assuming a 280 GHz antenna array with a 32*32 dual-polarized configuration, the wavelength λ is 1 mm and the length of each antenna element is half of the wavelength. Then, the area occupied by these antenna elements can be calculated as:

[0081]

[0082] Considering the margin set between the antenna elements, the antenna panel size is approximately 200 mm 2 . According to the lens radius that fits the geometrical optics approximation ranges from 10 to 30 wavelengths, the lens size can be calculated as:

[0083] π*λ 2 = 314 ~ 2826 mm 2 .

[0084] Then, the uplink gain obtained with the bifocal lens antenna will increase from 2 dB to 11.5 dB, as calculated below:

[0085] 10 log (314 / 200) = 2 dB,

[0086] 10 log(2826 / 200) = 11.5 dB.

[0087] Based on the above embodiments shown in Figure 9 and Figure 13 , for an antenna array with 32x32 dual-polarization configuration operating at 280 GHz, the bifocal lens antenna can have an extra 0.46-1 dB downlink gain and an extra 2-11.5 dB uplink gain. Considering that the cellular network coverage is limited by the uplink due to the power and hardware limitations of the terminal devices, the bifocal lens antenna can greatly improve the uplink gain compared to the downlink gain, so that the uplink cell coverage can be extended, as shown in Figure 14 .

[0088] In addition, channel estimation can result in significant training overhead. This problem becomes even more challenging in a mobile scenario, as the path is constantly changing. The transmitter then needs to frequently send pilot beams to update the estimation results, resulting in a considerable increase in training overhead and thus a sharp reduction in data throughput. However, with the embodiments shown in Figure 13 , coarse channel information is sufficient for beam alignment, as shown in Figure 15 .

[0089] Figure 16 Problems that can exist in the embodiments shown in Figure 9 are shown. The principle of the bifocal lens used in the embodiments of Figure 9 is that, after the lens refraction, all the rays emitted from the inner focal point are directed to the outer focal point. Therefore, a large antenna array for high frequency bands can have a narrow main lobe coverage, as shown in Figure 16 . In the case of terminal devices moving around, a beam sweeping and tracking function can be performed to track the movement of the terminal devices. After a beamformed wave is incident on the outer surface of the lens, it can be refracted by the lens. Then, the lens covers the space will be divided into two parts, the part covered by the refracted main lobe beam and the part covered by the refracted side lobe beam. For example, a terminal device located at point A can be served by the refracted main lobe beam. A terminal device located at point B can be served by the refracted side lobe beam. However, a terminal device located at point C cannot be served by the lens antenna, as no beam can propagate to point C. Therefore, although the power is concentrated, the coverage of the bifocal lens is reduced.

[0090] To overcome the problems shown in Figure 16 , the bifocal lens antenna can be used in combination with the embodiments shown in Figure 17A lens antenna according to another embodiment of the present disclosure is shown. This embodiment corresponds to the downlink scenario, the first option of the intended coverage, and the optional through-hole feature described above. The through-hole feature can also be referred to as a perforated bifocal lens, which can improve the coverage of the bifocal lens antenna. As shown in Figure 17 the intended coverage range, the bifocal lens is perforated to have a conical hole of space. In this way, the main lobe beam steers and tracks the terminal devices within the main lobe steering range (the conical region 1710) as the main lobe beam is not refracted. The lens coverage space is divided into three parts 1710, 1720, and 1730. According to the geometric optics theory, only the main lobe beam can cover region 1710, only the side lobe beam can cover region 1730, and both the main lobe and the side lobe can cover region 1720. For example, a terminal device located at point B can be served by both the refracted side lobe beam and the main lobe beam. A terminal device located at point C can be served by the main lobe beam. Compared to the embodiment of Figure 16 , the coverage of the perforated bifocal lens is improved, and spatial multiplexing gain can be obtained in region 1720.

[0091] Figure 18A is a diagram showing a lens antenna according to an embodiment of the present disclosure. This embodiment corresponds to the downlink scenario and the second option of the intended coverage described above. As shown in Figure 18A , a bifocal lens with an outer focus point close to the lens is used to widen the coverage of the pencil cell, so that the rays converging to the outer focus point will diverge to a wider range than the conventional high-frequency antenna array shown in Figure 18B . Optionally, as shown in Figure 18A , if the side lobe gain is not needed, the lens physical size can be reduced to keep only the central part to minimize the antenna size for micro-scale applications.

[0092] Figure 19 shows a micro-scale application example of the lens antenna shown in Figure 18A . In this application example, a 280GHz antenna panel (32*32 phased array) is placed above the office desk for users to connect laptops and mobile phones at any location within a 2-meter range. The 32*32 phased array only has a half-power beamwidth (HPBW) of 1.875 degrees.

[0093] Figure 20 is a diagram for explaining the design of the lens antenna according to an embodiment. As shown in the diagram, the lens profile design is explained by taking an elliptical bifocal lens as an example. All the rays refracted by the lens are converged to the outer focus point. The shape of the outer surface of the elliptical bifocal lens in polar coordinates can be obtained by imposing the path length collimation condition as shown below:

[0094] r1+ nl+ s+ r3= r1+ nT+ r3,

[0095] where r3 is the minimum distance between the outer focus and the lens. In addition, the following physical length conditions are satisfied:

[0096]

[0097] r1+ l= r2,

[0098] r1+ T= f,

[0099] where T is the thickness of the lens selected along the axis. Then, from the above four equations, the following quadratic equation can be obtained:

[0100] (1-n 2 )r2 2 +(2n 2 T+2n 2 r1+2nr3-2fcosθ-2r3cosθ)r2-n 2 T 2 -2n 2 Tr1-n 2 r1 2 -2nTr3-2nr1r3+2r3f+f 2 = 0, where r2 represents the outer surface profile. By solving the roots of the quadratic equation, the shape of the bifocal lens can be determined. Since optics and technology have been well developed for centuries, the lens antenna according to this embodiment is easy to design by geometrical optics and physical optics methods, and is easy to manufacture by computer numerical control milling machine (CNC), molding, and three-dimensional (3D) additive manufacturing.

[0101] Although in the above embodiment, the bifocal lens has been described as a singly refractive elliptical lens, the present disclosure is not limited to this example. As another example, a singly refractive hyperbolic bifocal lens can be used as the lens, as shown in Figure 21 . As yet another example, a birefringent bifocal lens can be used as the lens, as shown in Figure 22 . As yet another example, any other suitable type of lens having two foci can be used as the lens. The profile of other lens types can be calculated in a manner similar to the singly refractive elliptical lens. As yet another example, instead of a single lens, a combination of more than one lens having two foci can be used. For example, a pair of spaced apart convex lenses can be used in combination to act as a bifocal lens. As yet another example, the antenna array is not limited to being strictly located at the inner focus of the lens. Rather, the antenna array can be arranged to be spaced apart from the inner focus, as long as it is arranged on the inner side of the lens.

[0102] Based on the above description, at least one aspect of the present disclosure provides a lens antenna. The lens antenna includes an antenna array and a lens unit having a first focal point located at a first side of the lens unit and a second focal point located at a second side of the lens unit opposite the first side. The lens unit is capable of converging at least a portion of a beam emitted from the antenna array located at the first side of the lens unit at the second side of the lens unit.

[0103] In addition, the present disclosure also provides a radio unit including the above lens antenna and a base station including the radio unit. Other configurations of the radio unit and the base station can be well known to those skilled in the art, and for the sake of brevity, their details are omitted herein.

[0104] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the specification and relevant art and should not be interpreted in an overly idealized or overly formal sense unless expressly so defined herein.

[0105] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises", "comprising", "includes" and / or "including" when used herein, specify the presence of stated features, elements and / or components but do not preclude the presence or addition of one or more other features, elements, components and / or combinations thereof. As used herein, the statement that two or more parts or components "couple" or "connect" together refer to either an indirect coupling or connection between the parts or components or an direct coupling or connection between the parts or components.

[0106] It should be understood that, although the terms "first", "second" etc. can be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element without departing from the scope of the present disclosure. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed terms.

[0107] References in the disclosure to “one embodiment,” “an embodiment,” etc., mean that a described embodiment might include, but not require, the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that implementations of such feature, structure, or characteristic can be implemented in connection with other embodiments whether or not explicitly described.

[0108] It should be understood that the terms such as “top,” “bottom,” “left,” “right,” and the like refer to the orientation or positional relationship in the drawings shown by the figures, which are for purposes of convenience and brevity only and do not necessarily describe a specific orientation or position of the referenced elements, components, or devices, and are not intended to limit the scope of the disclosure. Thus, these terms are not to be construed as limiting the present disclosure.

[0109] As used herein, the term “example” is merely an example and illustrative, and should not be deemed to be exclusive or limiting. It should be noted that various aspects of the disclosure can be implemented individually or in combination with one or more other aspects. Further, the detailed description and specific examples are intended to be illustrative only and are not intended to limit the scope of the disclosure.

[0110] The present disclosure includes any novel feature or combination of features disclosed herein either explicitly or in any generalization thereof. Various modifications and adaptations to the foregoing exemplary embodiments of this disclosure will be apparent to those skilled in the relevant art in view of the foregoing description. However, any and all modifications shall not leave the scope of the non-limiting and exemplary embodiments of this disclosure.

Claims

1. A lens antenna comprising: an antenna array; and a lens unit having a first focal point located at a first side of the lens unit and a second focal point located at a second side of the lens unit opposite the first side, wherein the antenna array is located at the first focal point of the lens unit, wherein the lens unit is capable of converging at least a portion of a beam emitted from the antenna array located at the first side of the lens unit at the second focal point of the lens unit, wherein the antenna array is arranged to emit a main lobe beam at the first focal point and a plurality of side lobe beams diverging from the main lobe beam, wherein the lens unit is arranged to converge the main lobe beam and the plurality of side lobe beams to the second focal point, and wherein the lens unit is provided with an aperture that penetrates the lens unit such that another portion of the beam emitted from the antenna array is capable of propagating through the aperture without being converged by the lens unit. The lens unit is capable of converging the at least a portion of the beam emitted from the antenna array located at the first focal point to the second focal point.

2. The lens antenna of claim 1, wherein, The lens unit is capable of converging at least a portion of a beam emitted from a terminal device located within an intended coverage range of the lens antenna to the antenna array.

3. The lens antenna of claim 1 or 2, wherein, The intended coverage range of the lens antenna is based on a distance between the lens unit and the second focal point.

4. The lens antenna of claim 3, wherein, The aperture is disposed at a center of the lens unit.

5. The lens antenna of claim 1, wherein, The lens unit is one lens.

6. The lens antenna of claim 1, wherein, The one lens is one of:

7. The lens antenna of claim 6, wherein, a single refractive elliptical lens; a single refractive hyperbolic lens; a birefringent lens; and a Maxwell fish-eye lens. The lens unit is a combination of more than one lens.

8. The lens antenna of claim 1, wherein, The combination of more than one lens is a pair of convex lenses spaced apart.

9. The lens antenna of claim 8, wherein, The lens antenna operates at frequencies above 24.25 GHz.

10. The lens antenna of claim 1, wherein, 11. A radio unit comprising the lens antenna of claim 1.

12. A base station comprising the radio unit of claim 11. ​

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