Gradient index lens and manufacturing method thereof

Abstract

A gradient index lens (100) for shaping one or more microwave beams includes a primary lens (102) and one or more secondary lenses (104A to 104K). The primary lens (102) includes a cylinder of dielectric material with a cutout on a side surface of the cylinder. Each secondary lens (104A to 104K) of the one or more secondary lenses (104A to 104K) includes a plate of dielectric material that extends radially from the primary lens (102) within the cutout. The primary lens (102) and each of the secondary lenses have the same dielectric constant at a connection point of a central region of the plate of the secondary lens and the primary lens (102). The gradient index lens provides wide angle scanning while maintaining a high gain radiation pattern without suffering from scan loss effects.

Description

Technical Field

[0001] The present invention generally relates to antenna systems, and more particularly to gradient index lenses for shaping one or more microwave beams, and methods for manufacturing gradient index lenses. Background Art

[0002] With the development of new wireless communication technologies, there is an increasing demand to improve the key performance indicators (KPIs) of microwave antenna systems. The key performance indicators (such as directivity, gain, front-to-back ratio (FBR), coupling, beam width) are related to various parameters of the antennas used in the antenna system (such as electrical length, size, efficiency). In addition, due to the flexible structure of the multi-beam antenna scheme compared to the dynamic beamforming system, there is an increasing demand for the multi-beam antenna scheme.

[0003] Generally, due to the high directivity of each beam, the radiation pattern of a multi-beam antenna supports providing higher transmission power to multiple devices of user equipment (UE). However, traditional antenna systems are usually fed by bulky and lossy feed networks. When the beam points in a direction away from the line of sight, traditional antenna systems also suffer significant scan losses, which results in the performance of the antenna system being dependent on the azimuth angle. In addition, traditional antenna systems use lenses with circular symmetry, which makes the structure complex and the feed matching poor. Moreover, the feed ports of these lenses are sub-optimal and have a single linear polarization, which causes interference in the scan angle scan and low radiation pattern gain. Summary of the Invention

[0004] The inventors have identified the above disadvantages associated with antenna systems. The present invention aims to improve the gain and radiation pattern of a lens-based antenna system and reduce the scan loss effect.

[0005] The present invention provides a gradient index lens for transmitting one or more microwave beams and a method for manufacturing the gradient index lens. The present invention provides a solution to the existing problems related to the gain and radiation pattern of a lens-based antenna system due to the scan loss effect. The object of the present invention is to provide a solution that at least partially overcomes the problems encountered in the prior art and provides an improved gradient index lens for transmitting one or more microwaves and an improved lens manufacturing method.

[0006] One or more objects of the present invention are achieved by the solutions provided in the appended independent claims. Advantageous implementations of the present invention are further defined in the dependent claims.

[0007] In one aspect, the present invention provides a gradient index lens for shaping one or more microwave beams. The gradient index lens includes a main lens and one or more sub-lenses. The main lens includes a cylinder of dielectric material. In the cylinder, the dielectric constant decreases as the radial distance from the axis of the cylinder increases. The cylinder has a side surface and a notch on the side surface. The notch has an annular sector cross-sectional area. Thus, the notch extends radially (i.e., in the radial direction) and axially (i.e., parallel to the axis of the cylinder). The notch extends radially to an inner focal radius. The notch may extend axially over the entire height of the cylinder. Each of the one or more sub-lenses includes a plate of dielectric material extending radially from the main lens within the notch. In the plate, the dielectric constant decreases as the axial distance from the central region of the plate increases. Each of the main lens and the sub-lenses has the same dielectric constant at the connection point of the sub-lens with the main lens in the central region of the sub-lens. In other words, at the connection point of the sub-lens with the main lens in the central region of the sub-lens, the dielectric constant is spatially continuous.

[0008] The gradient index lens is a beam shaping optical device for microwaves and has a wide bandwidth. "Microwave" refers to electromagnetic radiation with a frequency between 1 GHz and 100 GHz. The gradient index lens provides wide-angle scanning while maintaining a high-gain radiation pattern without suffering from scanning loss effects. The gradient index lens includes a main lens and one or more sub-lenses to provide a zero focal length and a smooth dielectric transition between the one or more sub-lenses and the main lens. Thus, good impedance matching is achieved. In addition, circuits can be avoided, and commercially available dielectric materials with a low loss tangent can be used. Therefore, low induced losses of the gradient index lens can be achieved. The gradient index lens supports a wide bandwidth through a dielectric beam former, limited only by the feed radiation element. In addition, the input matching of the feed of each of the sub-lenses benefits from the smooth dielectric transition between different parts.

[0009] In one implementation, the sub-lenses are connected to the main lens at different azimuthal positions within the notch.

[0010] This supports the gradient index lens to be geometrically simple.

[0011] In another implementation, each of the sub-lenses is arranged to be fed a corresponding microwave beam from the one or more microwave beams and further feed the corresponding microwave beam to the main lens.

[0012] This supports the gradient index lens for use in a transmitting device. Use in a receiving device is also possible (the microwave beam will then propagate in the opposite direction to the transmitting device).

[0013] One of the one or more microwave beams may have dual polarization (i.e., includes two mutually orthogonal polarizations).

[0014] It should be noted that the gradient index lens supports dual polarization and does not require additional space.

[0015] In another implementation, each sub-lens in the sub-lenses includes a plurality of axially stacked sub-lenses, wherein each sub-lens includes a plate of axially extending dielectric material, and wherein the dielectric constant in the plate has an axial gradient.

[0016] In this implementation, the gradient index lens can be fabricated in a single molded part or in slices that are subsequently stacked together and support different heights (or different gain values).

[0017] The gradient index lens can be used in a multiple-input / multiple-output (MIMO) system.

[0018] On the other hand, the present invention provides a method for manufacturing a gradient index lens. The method includes providing a cylinder of dielectric material, wherein the dielectric constant in the cylinder decreases as the radial distance from the axis of the cylinder increases, and wherein the cylinder has a notch on the side surface of the cylinder. The notch has an annular sector cross-sectional area. Thus, the notch extends radially and axially. The notch extends radially to the inner focal radius. Axially, the notch can extend in a vertical direction over the entire height of the cylinder. The method includes connecting one or more plates of dielectric material to the cylinder such that each plate in the plates extends radially from the cylinder within the notch, and wherein the dielectric constant in the plate decreases as the axial distance from the central region of the plate increases. Thus, each plate in the one or more plates is connected to the cylinder within the notch and is aligned with the axis of the cylinder. The cylinder and each plate in the plates have the same dielectric constant at the connection point of the plate to the cylinder in the central region of the plate.

[0019] This method realizes all the advantages and technical effects of the gradient index lens of the present invention.

[0020] It should be noted that all devices, elements, circuits, units, and modules described in this application can be implemented by software or hardware elements or any combination thereof. All steps performed by the various entities described in this application and the functions to be performed by the various entities described are intended to mean that the corresponding entities are used to perform the corresponding steps and functions. Although in the description of the following specific embodiments, the specific functions or steps performed by external entities are not reflected in the description of the specific detailed elements of the entity performing the specific steps or functions, those skilled in the art should clearly understand that these methods and functions can be implemented by the corresponding software or hardware elements or any combination thereof. It should be understood that the features of the present invention are easily combinable in various combinations without departing from the scope of the present invention defined by the appended claims.

[0021] Additional aspects, advantages, features, and objects of the present invention will become apparent from the accompanying drawings and the detailed description of the illustrative implementations, which is to be interpreted in conjunction with the appended claims below. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above summary of the invention and the following detailed description of the illustrative embodiments can be better understood when read in conjunction with the accompanying drawings. For purposes of illustrating the present invention, an exemplary configuration of the present invention is shown in the drawings. However, the present invention is not limited to the specific methods and tools disclosed herein. In addition, those skilled in the art should understand that the drawings are not drawn to scale. Whenever possible, the same elements are denoted by the same reference numerals.

[0023] Embodiments of the present invention will be described by way of example only with reference to the following drawings, in which:

[0024] Figure 1 is a diagram of a gradient index lens according to an embodiment of the present invention;

[0025] Figure 2 is a diagram of a beamforming network of a gradient index lens according to an embodiment of the present invention;

[0026] Figure 3A is a diagram of a gradient index lens according to an embodiment of the present invention;

[0027] Figure 3B is a diagram of a gradient index lens according to an embodiment of the present invention;

[0028] Figure 4 is a diagram of a beamforming network of a gradient index lens according to an embodiment of the present invention;

[0029] Figure 5A and Figure 5B are graphical representations showing the phase and amplitude of the microwave field in the main lens of a gradient index lens according to different embodiments of the present invention;

[0030] Figure 5C and Figure 5D are graphical representations showing the phase and amplitude of the microwave field in the secondary lens of a gradient index lens according to different embodiments of the present invention;

[0031] Figure 6 shows a flowchart of a method for manufacturing a gradient index lens according to an embodiment of the present invention.

[0032] In the drawings, underlined numbers are used to denote the item in which the underlined number is located or an item adjacent to the underlined number. Non-underlined numbers relate to the item identified by a line associating the non-underlined number with the item. When a number is non-underlined and has an associated arrow, the non-underlined number is used to identify the general item to which the arrow points. Detailed Description of the Invention

[0033] The following detailed description illustrates embodiments of the invention and ways in which these embodiments may be implemented. Although some modes of carrying out the invention have been disclosed, those skilled in the art will recognize that there may be other embodiments for carrying out or practicing the invention.

[0034] Figure 1 is a diagram of a gradient index lens according to an embodiment of the invention. Referring to Figure 1 , a gradient index lens 100 is shown that includes a main lens 102 and one or more sub-lenses 104A through 104K.

[0035] The gradient index lens 100 may be used for microwave beamforming with wide bandwidth and wide angle scanning while maintaining a high gain radiation pattern without suffering from scan loss effects. The gradient index lens 100 provides a zero focal length, as well as a smooth dielectric transition between the one or more sub-lenses 104A through 104K and the main lens 102, which provides effective impedance matching.

[0036] The gradient index lens 100 includes a main lens 102 in the form of a cylinder of a dielectric material having a radially varying refractive index. The cylinder includes a cutout in a side surface of the cylinder. The cutout has an annular sector cross-sectional area. The cutout extends radially and axially. The cutout extends radially to an inner focal radius. The cutout may extend axially beyond the entire height of the cylinder. In other words, the cutout on the surface of the cylinder has such a shape in a cross-sectional view that it forms a cutout of a particular shape (which are annular sectors) at the base of the cylinder. In the example shown, the cutout extends axially along the entire height of the cylinder.

[0037] For transmitting (or receiving) in a primarily horizontal direction relative to the Earth, the axis of the cylinder may be oriented perpendicular to the Earth. In this case, the axial direction is vertical. Other orientations are possible.

[0038] The dielectric constant of the main lens 102 decreases as the radius of the cylinder increases. In one example, a Gutman graded index (GRIN) material is used as the dielectric material to fabricate the main lens 102 in the form of a cylinder. For example, the feed element of the main lens 102 is also based on a flat GRIN lens mechanism, which is fully dielectric to improve impedance matching. In addition, since circuits and commercially available dielectric materials with low loss tangents are avoided, the induced loss of the gradient index lens 100 is low. In one example, the notch extends radially to the inner focal radius represented by f (i.e., half of 2f), and the radius of the cylinder is represented by R (i.e., the diameter is 2R). In one implementation, the inner focal radius is half of the radius of the cylinder. In addition, the notch forms a protruding structure protruding from the cylinder in the axial direction, as Figure 1 shown.

[0039] The gradient index lens 100 further includes one or more sub - lenses 104A to 104K. In addition, each sub - lens is in the form of an axially - oriented plate of a dielectric material having an axial gradient index of refraction, and this plate is connected as a feed in the notch to the main lens 102 such that the axial orientation of each of the one or more sub - lenses 104A to 104K is aligned with the axis of the cylinder. The axial gradient index of refraction causes the dielectric constant of each of the sub - lenses to decrease as the distance from the central region of the sub - lens increases in the axial direction. In other words, one or more axially - oriented plates of dielectric material are axially connected to the notch of the main lens 102 to form one or more sub - lenses 104A to 104K. In addition, the vertical orientation of each of the one or more axially - oriented plates is also aligned with the axis of the cylinder of the main lens 102. In other words, one or more sub - lenses 104A to 104K are connected to the main lens 102 in such a way that each sub - lens is placed in a different position from another sub - lens. In one implementation, each sub - lens includes a beam port, for example, the sub - lens 104A includes a beam port 106. Similarly, the other sub - lenses also include corresponding beam ports for feeding the corresponding sub - lenses. In addition, since the feed is displaced to the zero - focal - length arc, the gradient index lens 100 is compact. In addition, the overall size of the gradient index lens 100 is reduced, for example, by moving the focal arc of the feed port from the lens surface to the interior of the gradient index lens 100. In addition, due to the use of a non - uniform distribution of dielectric constant materials, different beams are generated while reducing interference. Advantageously, compared with traditional methods, the gradient index lens 100 does not require the use of electronic components and provides wide - angle scanning while maintaining a high - gain radiation pattern without suffering from scan - loss effects. In addition, the main lens 102 and each of the sub - lenses have the same dielectric constant at the connection point of the central region of the sub - lens and the main lens 102. Therefore, the main lens 102 and each of the sub - lenses can be manufactured together by assembling using the symmetry of the structure, and thus improved prototyping can be achieved, for example, by using a 3D printer.

[0040] According to one embodiment, the main lens 102 and one or more sub - lenses 104A to 104K are manufactured from a substrate using molding. In one implementation, the main lens 102 includes a molded portion of the substrate, and the molded portion has holes in a first varying pattern to achieve the radial gradient index of refraction of the main lens 102. In another implementation, the main lens 102 includes a set of axially - stacked molded slices of the substrate, and each slice has holes in a first varying pattern to achieve the radial gradient index of refraction of the main lens 102. In yet another implementation, each of the sub - lenses includes a molded plate of the substrate, and the molded plate has holes in a second varying pattern to achieve the axial gradient index of refraction of the sub - lens.

[0041] In one implementation, one or more secondary lenses 104A to 104K are connected to the main lens 102 at different azimuthal positions within the notch. In one example, all feeds of each secondary lens among the secondary lenses are equal, and are fabricated by molding (e.g., by 3D printing) and assembled at different azimuthal positions. For example, the secondary lenses are connected to the main lens 102 at different azimuthal positions within the notch. In addition, the cylindrical configuration of the main lens 102 also simplifies the 3D printing process of the gradient index lens 100 in part. Thus, the gradient index lens 100 can be fabricated by a general and simplified manufacturing process. In one example, a radial multi-layer GRIN plate beamformer is distributed on the spherical surface of the main lens 102. In one example, o a two-dimensional (2D) azimuthal scan with dual polarization can be obtained within the range of ±60

[0042] without significant scan loss. In one implementation, the secondary lens is fed by one or more dual-polarized radiation sources. Thus, the gradient index lens 100 supports dual polarization and does not require additional space. In one implementation, the gradient index lens 100 is part of a multiple-input / multiple-output (MIMO) system (e.g., a fifth generation (5G) MIMO system). The 5G MIMO system can improve the signal range, increase the spectral efficiency, and reduce the power consumption. However, the gradient index lens 100 can be used in any multi-beam antenna scenario without limiting the scope of the present invention, such as for a sixth-generation (6G) small cell base station. The gradient index lens 100 can also be applicable to any product composed of multi-beam antennas, such as having special value for a 6G cellular system.

[0043] The gradient index lens 100 is a beam antenna with a wide bandwidth, which provides wide-angle scanning while maintaining a high-gain radiation pattern without suffering from scan loss effects. The gradient index lens 100 includes a main lens 102 and one or more secondary lenses 104A to 104K to provide a zero focal length, and a smooth dielectric transition between the one or more secondary lenses 104A to 104K and the main lens 102, which achieves effective impedance matching. In addition, due to the avoidance of circuits and commercially available dielectric materials with low loss tangents, the induced loss of the gradient index lens 100 is low. The gradient index lens 100 supports a wide bandwidth through a dielectric beamformer and is only limited by the feeding radiation elements. In addition, the input matching of the feeds of each secondary lens among the secondary lenses benefits from the smooth dielectric transition between different parts.

[0044] Figure 2 A beamforming network 202 including the gradient index lens 100 described above is schematically shown. In combination withFigure 1 Element description Figure 2 .

[0045] In one implementation, the gradient index lens 100 includes thin radial plates, such as one or more sub-lenses 104A to 104K, which form a feed network including a plurality of beam ports 204, as Figure 2 shown. The plurality of beam ports 204 are shown according to the degrees of the radiation pattern that vary with the value of θ. For example, the radiation pattern includes a main beam of zero degree and a plurality of side beams ranging from -60 degrees to -15 degrees and +15 degrees to +60 degrees. In addition, the plurality of beam ports 204 of one or more sub-lenses 104A to 104K are used to generate different beams using a non-uniform dielectric constant material distribution. In one example, the dielectric beam former supports a wide bandwidth, limited only by the feed radiation elements of one or more sub-lenses 104A to 104K. In addition, the input matching of the plurality of beam ports 204 benefits from the smooth dielectric transition between components. In addition, a single-component structure with a compact size is achieved by using a zero-focal-length feed at the inner focal radius. Therefore, the gradient index lens 100 supports dual polarization and does not require additional space occupancy.

[0046] Figure 3A is a diagram of a gradient index lens according to an embodiment of the present invention. In combination with Figure 1 and Figure 2 Element description Figure 3A . Referring to Figure 3A , a gradient index lens 100 including a main lens 102 ( Figure 1 ), a sub-lens 302, and a beam port 304 is shown. A scale representing the change in dielectric constant is also shown, ranging from 1 decibel (dB) to 5 dB with a step of 0.4 dB.

[0047] In one implementation, the overall size of the main lens 102 is reduced by moving the focal arc of the feed port from the surface of the main lens 102 to the inside of the main lens 102. In addition, the sub-lens 302 is in the form of a plate of an axially oriented dielectric material having an axial gradient index, and this plate is connected to the main lens 102 as a feed source within a cutout such that the axial orientation of the sub-lens 302 is aligned with the axis of the cylinder. In one example, by distributing a radial multi-layer GRIN plate beam former on the spherical surface of the main lens 102, a two-dimensional (2D) azimuthal scan with dual polarization can be obtained within a range of ±60 o degrees without significant scan loss. In addition, the dielectric constant at the center of the sub-lens 302 is the same as the dielectric constant at the focal point of the main lens 102. For example, the smooth transition optimizes the impedance matching of the gradient index lens 100.

[0048] Figure 3Bis a diagram of a gradient index lens according to another embodiment of the present invention. In combination with Figure 1 、 Figure 2 and the element descriptions of FIG. 3 Figure 3B . Referring to Figure 3B , a gradient index lens 100 is shown that includes a main lens 102, a first sub-lens 306A, a second sub-lens 306B, a first beam port 308A, and a second beam port 308B (including Figure 1 ). A scale representing the change in dielectric constant is also shown, with a range from 1 decibel (dB) to 5 dB and a step size of 0.4 dB.

[0049] In one implementation, each sub-lens in the secondary lens includes axially stacked sub-lenses, each sub-lens formed of a plate of axially oriented dielectric material having an axial gradient index of refraction and configured as a feed. In this implementation, the gradient index lens 100 can be fabricated in a single molded component. Alternatively, the gradient index lens can be fabricated in slices that are stacked together and allow for different heights (or different gain values). For example, the secondary lens (e.g., Figure 3A secondary lens 302) includes a first sub-lens 306A and a second sub-lens 306B, for example, the second sub-lens 306B is axially stacked on the first sub-lens 306A. Additionally, the first sub-lens 306A and the second sub-lens 306B are formed of plates of axially oriented dielectric material having an axial gradient index of refraction. Further, the first sub-lens 306A includes a first beam port 308A, and the second sub-lens 306B includes a second beam port 308B. In one example, more than one GRIN plate can be allocated and individually controlled, thus supporting scanning in the elevation plane.

[0050] Figure 4 is a diagram of a beamforming network of a gradient index lens according to an embodiment of the present invention. In combination with Figure 1 、 Figure 2 、 Figure 3A and Figure 3B the element descriptions Figure 4 . Referring to Figure 4 , a schematic diagram 400 of a beamforming network 202 of a gradient index lens 100 of Figure 1 is shown. In one implementation, the gradient index lens 100 includes radial thin plates that form a feed network including beam ports 402 as shown in Figure 4 . The beam ports 402 are shown according to the degrees of the radiation pattern that vary with the value of θ. For example, the radiation pattern includes a main beam and two side beams.

[0051] Figure 5A and Figure 5Bis a graphical representation showing the phase and amplitude of a main lens of a gradient index lens according to different embodiments of the present invention. In combination with Figure 1 、 Figure 2 、 Figure 3A 、 Figure 3B and Figure 4 element descriptions Figure 5A and Figure 5B . Referring to Figure 5A , a graphical representation 500A of the phase of the main lens 102 of the gradient index lens 100 of Figure 1 is shown. Referring to Figure 5B , a graphical representation 500B of the amplitude of the main lens 102 of the gradient index lens 100 of Figure 1 is shown. In one example, the phase is changed to obtain a plane wave at the output interface of the gradient index lens 100.

[0052] Figure 5C and Figure 5D are graphical representations showing the phase and amplitude of the microwave field in the secondary lens of a gradient index lens according to different embodiments of the present invention. In combination with Figure 1 、 Figure 2 、 Figure 3A 、 Figure 3B and Figure 4 element descriptions Figure 5C and Figure 5D . Referring to Figure 5C , a graphical representation 500C of the phase of the secondary lens (e.g., the secondary lens 302 of Figure 1 ) of the gradient index lens 100 of Figure 3A is shown. Referring to Figure 5D , a graphical representation 500D of the amplitude of the secondary lens of the gradient index lens 100 of Figure 1 is shown. In one implementation, the dielectric constant at the center of the secondary lens 302 is the same as the dielectric constant at the focal point of the main lens 102 to which the secondary lens 302 is connected.

[0053] Figure 6 shows a flowchart of a method for manufacturing a gradient index lens according to an embodiment of the present invention. In combination with Figure 1 、 Figure 2 、 Figure 3A and Figure 3B element descriptions Figure 6 . Referring to Figure 6 , a flowchart of a method 600 including steps 602 to 606 is shown.

[0054] In step 602, method 600 includes fabricating a main lens 102 in the form of a cylinder of a dielectric material having a radial gradient refractive index, wherein the cylinder has a notch on a lateral surface of the cylinder, the notch having an annular sector cross-sectional area. The notch extends radially and axially. Radially, the notch extends in a radial direction to an inner focal radius. The notch may extend axially along an entire height of the cylinder. The radial gradient refractive index causes the dielectric constant of the main lens 102 to decrease as the radius of the cylinder increases. In one example, a Gutman gradient refractive index (GRIN) material is used as the dielectric material to fabricate the main lens 102 in the form of a cylinder. For example, the feed element of the main lens 102 is also based on a flat GRIN lens mechanism, which is fully dielectric to improve impedance matching. Additionally, due to the avoidance of circuitry and commercially available dielectric materials with low loss tangents, the induced loss of the gradient refractive index lens 100 is low. Additionally, the notch forms a protruding structure protruding from the cylinder, as Figure 1 shown.

[0055] In step 604, method 600 includes fabricating one or more secondary lenses 104A to 104K, each secondary lens in the form of a plate of an axially oriented dielectric material having an axial gradient refractive index. Additionally, the axial gradient refractive index causes the dielectric constant of each of the secondary lenses to decrease as the distance from a central region of the secondary lens increases in the axial direction. In other words, each of the one or more secondary lenses 104A to 104K is fabricated in the form of an axially oriented plate and axially connected to the main lens 102. For example, each secondary lens is placed at a different position from another secondary lens. Advantageously, compared to conventional methods, the gradient refractive index lens 100 provides wide-angle scanning while maintaining a high-gain radiation pattern without suffering from scan loss effects.

[0056] In step 606, method 600 includes connecting each of the one or more secondary lenses 104A to 104K, which are serving as feed sources, to the main lens 102 within the notch such that the axial orientation of each of the secondary lenses is aligned with the axis of the cylinder. Additionally, the main lens 102 and each of the secondary lenses have the same dielectric constant at a connection point of the central region of the secondary lens with the main lens 102. According to one embodiment, the main lens 102 and the one or more secondary lenses 104A to 104K are fabricated from a substrate by molding. Thus, the main lens 102 and each of the secondary lenses can be fabricated together by assembling by taking advantage of the symmetry of the structure, whereby improved prototyping can be achieved, for example by using a three-dimensional printer.

[0057] In one implementation, the main lens 102 includes a molded portion of a substrate, the molded portion having holes in a first varying pattern to achieve a radial gradient index of refraction of the main lens 102. In one example, a three-dimensional printer can be used to fabricate the molded portion of the substrate. In another implementation, the main lens 102 includes a set of axially stacked molded slices of the substrate, each slice having holes in a first varying pattern to achieve a radial gradient index of refraction of the main lens 102. Thus, the gradient index lens 100 can be fabricated in one molded component or in slices that are subsequently stacked together and support different heights (or different gain values). According to one embodiment, each sub-lens in the sub-lenses includes a molded plate of the substrate, the molded plate having holes in a second varying pattern to achieve an axial gradient index of refraction of the sub-lens. Thus, the gradient index lens can be fabricated by a general and simplified manufacturing process. Advantageously, compared with traditional methods, the gradient index lens 100 provides wide-angle scanning while maintaining a high-gain radiation pattern without suffering from scanning loss effects.

[0058] The method 600 for fabricating the gradient index lens 100 provides wide-angle scanning while maintaining a high-gain radiation pattern without suffering from scanning loss effects. In addition, the method 600 provides a zero focal length and a smooth dielectric transition between one or more sub-lenses 104A to 104K and the main lens 102, which achieves effective impedance matching. Further, due to the avoidance of circuitry and commercially available dielectric materials with low loss tangents, the induced loss of the gradient index lens 100 is low. The method 600 is used to fabricate the gradient index lens 100, and the gradient index lens 100 supports a wide bandwidth through a dielectric beam former and is limited only by the feed radiation element. In addition, the input matching of the feed of each sub-lens in the sub-lenses benefits from the smooth dielectric transition between different parts.

[0059] Method modifications may be made to the embodiments of the present invention described above without departing from the scope of the present invention as defined by the appended claims. Expressions such as "comprising", "including", "having", "being", etc. used to describe and claim the present invention are intended to be interpreted in a non-exclusive manner, i.e., to support the existence of items, components or elements not explicitly described. References to the singular should also be interpreted as referring to the plural. The term "exemplary" as used herein means "serving as an example, instance, or illustration". Any embodiment described as "exemplary" is not necessarily to be construed as more preferred or advantageous than other embodiments, nor does it necessarily exclude combinations of features of other embodiments. The term "optionally" as used herein means "provided in some embodiments and not provided in other embodiments". It should be understood that certain features of the present invention described in the context of separate embodiments for clarity may also be provided in combination in a single embodiment. Conversely, the various features of the present invention described in the context of a single embodiment for brevity may also be provided separately, in any suitable combination, or in any other described embodiment suitable for the present invention.

Claims

1. A gradient index lens (100) for shaping one or more microwave beams, characterized in that, the gradient index lens (100) comprises a main lens (102) and one or more sub - lenses (104A to 104K); the main lens (102) comprises a cylinder of dielectric material, wherein the dielectric constant in the cylinder decreases as the radial distance from the axis of the cylinder increases, wherein the cylinder has a side surface and a cut on the side surface, and wherein the cut has an annular sector cross - sectional area; each of the one or more sub - lenses (104A to 104K) comprises a plate of dielectric material, the plate radially extending from the main lens (102) within the cut, wherein the dielectric constant in the plate decreases as the axial distance from the central region of the plate increases; the main lens (102) and each of the sub - lenses have the same dielectric constant at the connection point of the central region of the plate of the sub - lens and the main lens (102).

2. The gradient index lens (100) according to claim 1, wherein, The sub - lenses are connected to the main lens (102) at different azimuthal positions within the cut.

3. The gradient index lens (100) according to claim 1 or 2, characterized in that, Each of the sub - lenses (104A to 104K) is arranged to be fed a corresponding one of the one or more microwave beams and to further feed the corresponding microwave beam to the main lens (102).

4. The gradient index lens (100) according to any one of claims 1 to 3, characterized in that, Each of the one or more microwave beams has dual polarization.

5. The gradient index lens (100) according to any one of claims 1 to 4, characterized in that, Each of the sub - lenses comprises a plurality of axially stacked sub - lenses, wherein each sub - lens comprises an axially extending plate of dielectric material, and wherein the dielectric constant in the plate has an axial gradient.

6. The gradient index lens (100) according to any one of claims 1 to 5, for use in a multiple - input / multiple - output MIMO system.

7. A method (600) of manufacturing a gradient index lens (100), comprising: providing a cylinder of dielectric material, wherein the dielectric constant in the cylinder decreases as the radial distance from the axis of the cylinder increases, and wherein the cylinder has a cut on the side surface of the cylinder, and wherein the cut has an annular sector cross - sectional area; connecting one or more plates of dielectric material to the cylinder such that each of the plates radially extends from the cylinder within the cut, wherein the dielectric constant in the plate decreases as the axial distance from the central region of the plate increases; wherein the cylinder and each of the plates have the same dielectric constant at the connection point of the central region of the plate and the cylinder.

8. The method (600) according to claim 7, comprising: forming the cylinder and the one or more plates by molding.

9. The method (600) according to claim 7 or 8, characterized in that, The cylinder comprises holes arranged in a first pattern such that the dielectric constant in the cylinder decreases as the radial distance from the axis of the cylinder increases.

10. The method (600) according to claim 7 or 8, characterized in that, The cylinder includes a set of axially stacked molded slices, wherein each of the molded slices includes holes arranged in a first pattern such that the dielectric constant in the cylinder decreases as the radial distance from the axis of the cylinder increases.

11. The method (600) according to any one of claims 7 to 10, characterized in that, Each of the plates includes holes in a second pattern such that the dielectric constant in the plate decreases as the axial distance from the central region of the plate increases.

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