Patent Description:
According to an aspect of the invention, there is provided an antenna unit according to claim <NUM>. The mask pattern may be based on a Fresnel zone plate. The first angle may be <NUM>° and the mask pattern may be defined by an interference pattern produced when the Fresnel zone plate is irradiated by the second waves at the second angle. The mask pattern may comprise sections opaque to the first waves and to the second waves and sections transparent to the first waves and to the second waves. The mask pattern may comprise a difference in thickness between first sections and second sections that result in a path length difference equivalent to a wavelength of the first waves or second waves divided by two. The first waves and the second waves may each have a frequency in a range of <NUM> to <NUM>. A difference between the first angle and the second angle may be up to <NUM>°.

The Fresnel zone plate may comprise alternating rings opaque to the waves incident on the lens plate and rings transparent to the waves incident on the lens plate. The mask pattern may comprise a difference in thickness between first sections and second sections that result in a path length difference equivalent to a wavelength of the waves incident on the lens plate divided by two. The waves incident on the lens plate may have a frequency in a range of <NUM> to <NUM>.

In still another aspect, embodiments of the disclosure relate to an antenna unit according to claim <NUM> or claim <NUM>. The plurality of superimposed Fresnel zone plates may comprise at least three Fresnel zone plates that overlap along at least one of a horizontal axis or a vertical axis of the lens plate, the at least three Fresnel zone plates producing at least three focal points. Each of the at least three focal points may lie along a line. The plurality of superimposed Fresnel zone plates may comprise four Fresnel zone plates that overlap in such a way to produce four focal points that form a square. The mask pattern may comprise an obround Fresnel zone plate. The mask pattern may comprise two Fresnel zone plates in which a center ring of a first Fresnel zone plate overlaps with a center ring of a second Fresnel zone plate.

Additional features and advantages will be set forth in the detailed description that follows, and, in part, will be readily apparent to those skilled in the art from the description or recognized by practicing the embodiments as described in the written description and claims hereof, as well as the appended drawings.

The accompanying drawings are included to provide a further understanding and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiment(s), and together with the description serve to explain principles and the operation of the various embodiments. In the drawings:.

Embodiments of the present disclosure relate to an antenna unit having a Fresnel zone plate lens with a mask pattern that manipulates the focal point(s) and/or direction of an incident incoming wave. In embodiments, the mask pattern allows for waves having two different incident angles to have the same focal spot on an antenna array of the antenna unit. Further, in embodiments, the mask pattern allows for the focal spot to be offset vertically and/or horizontally from the center position. In still further embodiments, the mask pattern is created by superimposing multiple Fresnel zone plates to produce multiple focal points that can be spaced out vertically and/or horizontally.

The mask patterns disclosed herein include alternating opaque (absorbing or reflecting) and transparent sections or sections with alternating thicknesses whose spacings are dictated by the lens focal length at the specified microwave frequency. The mask patterns can be produced through various deposition or coating or printing techniques, such as screen printing, spray coating, slot coating, and thin film deposition techniques. Further, in embodiments, the mask patterns can be produced trough material removal or addition.

Applicant believes that the antenna units described herein are applicable to the <NUM> infrastructure. As used herein, "<NUM>" refers to signals transmitted via microwaves, in particular having a frequency of <NUM> to <NUM>. The <NUM> network includes many antenna units that transmit directional waves to other antenna units. Applicants have found a way to enhance the lens gain of the antenna units by focusing the waves incident upon the antenna units to specific, desired regions of an antenna array. In this way, the antenna units can transmit and receive over greater distances, thereby reducing the required number of antenna units in the network. Various embodiments of an antenna unit, in particular that is usable in the <NUM> infrastructure, are disclosed herein. These embodiments are presented by way of example and not by way of limitation.

<FIG> depicts an embodiment of an antenna unit <NUM> having a housing <NUM> surrounding an antenna array <NUM>. In embodiments, the antenna array <NUM> comprises a plurality of individual antennas, such as patch antennas, mounted to a ground plane. In embodiments, the patch antennas are rectangular sheets (i.e., "patches") of metal that may be connected with microstrip transmission lines so as to group the antennas into multiple phased arrays. The housing <NUM> includes a lens plate <NUM>. In embodiments, the lens plate <NUM> is a planar surface arranged parallel to and spatially disposed from a plane defined by the antenna array <NUM>. By "parallel" or "substantially parallel" it is meant that the plane of the lens plate <NUM> is substantially geometrically parallel to within about +/- <NUM>° to the plane of the antenna array, such as within about +/- <NUM>°, such as within about +/- <NUM>°, such as within about +/- <NUM>° or for more complex geometry (e.g., slightly convex curve, etc.), the net angle is within about +/- <NUM>°. As will be disclosed herein, the lens plate <NUM> focuses the intensity of electromagnetic waves incident upon the lens plate <NUM> onto a particular region of the antenna array <NUM>.

In order to focus the radiation, the lens plate <NUM> includes a mask pattern <NUM> including a series of first sections <NUM> and second sections <NUM>. As will be appreciated from the discussion that follows, the mask pattern <NUM> focuses the incident waves via diffraction from the first sections <NUM> and the second sections <NUM>. In embodiments, the first sections <NUM> are opaque, and the second sections <NUM> are transparent. By "opaque," it is meant that the first sections <NUM> block electromagnetic radiation of a particular wavelength from passing through the lens in the area of the first sections <NUM>. By "transparent," it is meant that the second sections <NUM> permit electromagnetic radiation of a particular wavelength to pass through the lens in the area of the second sections <NUM>. In embodiments, the second sections <NUM> transmit at least <NUM>% of electromagnetic radiation of a particular wavelength through the lens in the area of the second sections <NUM>. In other embodiments, the second sections <NUM> transmit at least <NUM>% of electromagnetic radiation of a particular wavelength through the lens in the area of the second sections <NUM>, and in still other embodiments, the second sections <NUM> transmit at least <NUM>% of electromagnetic radiation of a particular wavelength through the lens in the area of the second sections <NUM>. In other embodiments, the first sections <NUM> have a different thickness than the second sections <NUM>.

In particular embodiments, a difference in thickness of the lens plate <NUM> is provided between the first sections <NUM> and the second sections <NUM>. In embodiments, a difference in thickness between the first sections <NUM> and the second sections <NUM> is chose to result in a path length difference equivalent to the wavelength of the incident wave divided by two.

The mask pattern <NUM> is based on the diffraction pattern produced by a wave of electromagnetic radiation incident on a Fresnel zone plate (FZP) as shown in <FIG>. In an FZP, the first sections <NUM> and the second sections <NUM> are a series of concentric rings that alternate between rings of the first section <NUM> and rings of the second section <NUM>. The radii of the rings are based on the following equation: <MAT>.

In this equation, rn is the radius of the nth ring of the FZP, n is the integer number of rings, λ is the wavelength of the incident wave, and f is the focal length. The equation considers a wave that is incident at an incident angle θinc of <NUM>°. When the incident angle θinc is <NUM>° (i.e., the incident wave is substantially normal (e.g., within +/-<NUM>°) to the plane of the lens plate <NUM>), the FZP will focus the waves through diffraction to a spot directly in line with an axis perpendicular to and passing through the center of the Fresnel zone at the focal length f away from the lens plate <NUM>. Thus, in designing the antenna <NUM> of <FIG>, the antenna array <NUM> would preferably be placed at the focal length f away from the lens plate <NUM> so that the maximum intensity of the wave is received by the antenna array <NUM>. However, when the incident angle θinc does not equal <NUM>°, the focal spot of the incident wave will not be directly in line with the axis perpendicular to the FZP. Instead, the focus of the obliquely incident wave will be off-center and diffuse as compared to the in-line and concentrated focal spot of an on-axis wave.

To illustrate, <FIG> depicts an FZP for a wave with an incident angle θinc of <NUM>°, and <FIG> illustrates the distribution of intensity for a diffracted wave having an incident angle θinc of <NUM>° off the perpendicular in the x-direction. As can be seen in <FIG>, the focal spot of the diffracted wave is displaced more than <NUM> away from the center. Thus, with respect to the embodiment shown in <FIG>, the lens plate <NUM> would not diffract the incident wave to the desired region of the antenna array <NUM>.

In order to re-center and concentrate the intensity of an incident wave that is off-axis, the mask pattern <NUM> is based off the intensity distribution pattern shown in <FIG>. That is, the mask pattern <NUM> shown in <FIG> is substantially the same as the intensity distribution shown in <FIG>. As shown in <FIG>, when a wave is incident upon the mask pattern <NUM> at an incident angle of <NUM>°, the intensity distribution has a focal spot <NUM> centered at <NUM> in the x- and y-directions with respect to the graph shown in <FIG>. Additionally, when a wave is incident upon the mask pattern <NUM> at an incident angle of <NUM>°, the diffracted intensity distribution also has a focal spot <NUM> centered at <NUM> in the x- and y-directions as shown in <FIG>. Thus, the mask pattern <NUM> of <FIG> provides a centered and concentrated intensity for waves that are incident at both <NUM>° (<FIG>) and <NUM>° (<FIG>). In practice, the mask pattern <NUM> provides a centered and concentrated intensity for waves incident at angles of <NUM>° ± <NUM>° and <NUM>° ± <NUM>°. That is, the mask pattern <NUM> can concentrate the intensity of a range of incident waves centered on the desired directions of incidence. In embodiments, the degree of separation between the directions of incidence is up to <NUM>°. Accordingly, antennas <NUM> utilizing such a mask pattern <NUM> on the lens plate <NUM> are able to receive signals from multiple directions, or antennas <NUM> that are restricted in the installation geometry can still direct an off-axis signal to a desired region of an antenna array <NUM>.

In other embodiments, the mask pattern <NUM> can be used to deliberately move the focal spot <NUM> off-center. For example, with reference to <FIG>, the embodiment discussed in relation to <FIG> were designed to provide an on-center focal spot in the case of an incident wave that was off-axis. However, in the embodiments of <FIG>, the mask pattern <NUM> is configured to move the focal spot of an on-axis wave to an off-center position. For example, the wave may be incident on the lens plate <NUM> along a first axis, and the mask pattern <NUM> will produce a focal spot that is not on that first axis but on another axis spatially disposed from the first axis. In exemplary embodiments, the mask pattern <NUM> is configured to move the focal spot, e.g., to irradiate a desired portion of an antenna array <NUM> (as shown in <FIG>) that is not located along the axis of incidence, or to accommodate off-axis placement of the array <NUM>. In embodiments, the mask pattern <NUM> is configured to move the focal spot at least <NUM> off-center. In another embodiment, the mask pattern <NUM> is configured to move the focal spot at least <NUM> off-center, and in still another embodiment, the mask pattern <NUM> is configured to move the focal spot at least <NUM> off-center. In certain embodiments, the mask pattern is configured to move the focal spot up to <NUM> off center.

<FIG> depicts a mask pattern <NUM> designed to move the focal spot <NUM> down in the y-direction. The mask pattern <NUM> is based on an FZP <NUM> in which the center ring of the FZP <NUM> is off-set from the geometric center of the lens plate <NUM>. <FIG> depicts the intensity distribution for a diffracted, on-axis wave (i.e., on an axis running through the geometric center of the mask pattern <NUM>). As can be seen, the focal point <NUM> is at the same position (i.e., located along the same axis) as the center ring of the FZP <NUM>. That is, with respect to the antenna unit <NUM> of <FIG>, offsetting the center ring of the FZP <NUM> by <NUM> on the lens plate <NUM> causes the focal point <NUM> to be offset by <NUM> on the antenna array <NUM>. <FIG> depicts an offset of the FZP <NUM> by <NUM>, and as can be seen in <FIG>, the focal point <NUM> is also offset by <NUM>.

The mask pattern <NUM> of <FIG> and <FIG> may be useful, e.g., to accommodate deployment of the antenna unit <NUM> in situations where alignment of a phased antenna array with the lens plate <NUM> is not possible or is undesirable. Further, in embodiments, the antenna array <NUM> of the antenna <NUM> may not be centered within the housing <NUM>. While the vertical position of the focal spot <NUM> was depicted as being moved in <FIG>, the horizontal position of the focal spot <NUM> could also be moved in embodiments by moving the center ring of the FZP <NUM> along the horizontal axis, and in other embodiments, the focal spot <NUM> can be moved both horizontally and vertically from the center of the mask pattern <NUM> by moving the center ring of the FZP <NUM> along both the horizontal and vertical axes.

In still other embodiments, the mask pattern <NUM> is configured to provide multiple focal spots <NUM>. <FIG> depicts an embodiment in which the mask pattern <NUM> comprises multiple superimposed FZP <NUM> across the x-direction. In general, each superimposed FZP <NUM> will produce its own focal spot <NUM>. In particular, <FIG> includes three superimposed FZP <NUM>: a central FZP 26a, a left FZP 26b, and a right FZP 26c. As shown in <FIG>, this pattern of FZP 26a, 26b, 26c produces three focal spots <NUM> in which each focal spot <NUM> is located at the center of each FZP 26a, 26b, 26c for an incident wave at an incident angle of <NUM>°. Thus, the spacing of each focal spot <NUM> is determined by the spacing of the FZP 26a, 26b, 26c. The focal spots <NUM> are quasi-uniform in that the intensity is slightly greater and more concentrated in the focal spot <NUM> behind the center FZP 26a than the intensity of the focal spots <NUM> behind the outer FZP 26b, 26c. A multi-focal spot mask pattern may be used, e.g., to focus the wave on both a primary and a backup antenna array <NUM> such that the antenna unit <NUM> easily be switched back and forth between the primary and backup antenna array if one is damaged.

<FIG> depicts another embodiment in which the mask pattern <NUM> includes five superimposed FZP <NUM>: a center FZP 26a, an intermediate left FZP 26b, a far left FZP 26c, an intermediate right FZP 26d, and a far right FZP 26e. As can be seen in the intensity distribution of <FIG>, the five, quasi-uniform focal spots <NUM> are produced behind the centers of each FZP 26a-26e. As with the previous embodiment shown in <FIG>, the embodiment of <FIG> demonstrate that the intensity and concentration of the focal spots <NUM> decreases moving outward from the center focal spot <NUM>, which is located behind the center FZP 26a.

The embodiments of <FIG> and <FIG> demonstrate that the focal spots <NUM> can be spaced along the horizontal axis of the antenna array <NUM>. However, in other embodiments, the focal spots <NUM> could instead be spaced along the vertical axis of the antenna array <NUM> by superimposing the FZP <NUM> across the vertical axis instead. Further, the focal spots <NUM> of the embodiment depicted are all located along the same line as the other focal spots <NUM>. However, by shifting one or more of the superimposed FZP <NUM> relative to the other FZP <NUM>, the focal spots <NUM> can be arranged out of line from each other (see discussion of <FIG>, below).

<FIG> demonstrates another configuration of an FZP <NUM> that provides two horizontally separated focal spots. The FZP <NUM> in this instance is obround, comprising two semicircles separated by a rectangular section. As shown in <FIG>, the focal points <NUM> are located at the ends of the rectangular section between the semicircle portions. In embodiments, the obround FZP <NUM> can be arranged along the vertical axis instead of the horizontal axis to provide focal points spaced apart on the horizontal axis. Further, in embodiments, the obround FZP <NUM> is arranged at an angle to both the horizontal and vertical axes to provide focal points <NUM> spaced apart diagonally.

<FIG> depicts an embodiment in which a first offset FZP 26a is overlapped with a second offset FZP 26b. The FZP 26a, 26b are offset along the vertical axis such that the center ring of each FZP 26a, 26b is offset from the center of the lens plate <NUM>. The center rings of the FZP 26a, 26b are also overlapped. As shown in <FIG>, the focal points <NUM> are located along the same axis as the center rings of the offset FZP 26a, 26b. <FIG> depicts another embodiment in which the center rings of FZP 26a, 26b are overlapped to a greater degree than in <FIG>. Thus, as shown in <FIG>, the focal points <NUM> are positioned closer together while still remaining offset. In embodiments, the overlapped and offset FZP 26a, 26b may be arranged along the horizontal axis instead of the vertical axis to provide focal points <NUM> spaced along the horizontal axis.

<FIG> depicts still another embodiment having multiple focal points <NUM> that are spaced apart. In particular, <FIG> includes four superimposed FZP 26a-26d. The FZP 26a-26d are arranged in a 2x2 array with overlapping quadrants. As shown in <FIG>, the focal points <NUM> are arranged in a square at the center of each FZP 26a-26d.

Having described various embodiments of the mask pattern <NUM>, the following discussion will be directed to how to fabricate the mask pattern <NUM> on the lens plate <NUM>. In embodiments, the mask pattern <NUM> is fabricated using screen printing or sputter coating. In an exemplary embodiment of screen printing, modelled data for the mask pattern <NUM> can be converted to screen-printable file using pattern design software. Thereafter, the screen mesh, emulsion thickness, and tension based on the pattern resolution are determined for the screen printing process. The material of the lens plate (e.g., glass having a thickness of <NUM>-<NUM>) is cleaned. For the screen printing ink, a microwave opaque material is selected for screen printing. The material can be absorbing or reflecting of microwaves. Examples include silver-based ink, silver nanowire-based ink. The screen area is flooded with the selected screen ink for the printing step, and when sufficient wetting of the screen surface is achieved, the print step is applied using varying print speed (mm/sec), gap (mm) and print pressure (KgF or psi). In embodiments, the thickness of the opaque material deposited onto the lens plate is about <NUM> to <NUM> thick. Once the ink is applied, it is baked or UV-cured. Alternatively, low E coating (such as those used for window applications) can be vacuum deposited on a pre-masked glass substrate and followed by the removal of the mask after deposition. Resistitivity values of <NUM>-<NUM>Ω/m indicate that the layer will be opaque to microwave in the frequency of interest.

Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not actually recite an order to be followed by its steps or it is not otherwise specifically stated in the claims or descriptions that the steps are to be limited to a specific order, it is in no way intended that any particular order be inferred. In addition, as used herein, the article "a" is intended to include one or more than one component or element, and is not intended to be construed as meaning only one.

Claim 1:
An antenna unit (<NUM>), comprising:
an antenna array (<NUM>) comprising a plurality of antennas, the antenna array defining a first plane; and
a lens plate (<NUM>) comprising a mask pattern (<NUM>), the lens plate defining a second plane, wherein the lens plate is spaced apart from the antenna array and wherein the second plane of the lens plate is substantially parallel to the first plane of the antenna array;
wherein the mask pattern (<NUM>) is configured to focus first waves incident on the lens plate (<NUM>) through diffraction to a first region of the antenna array (<NUM>), the first waves being incident on the lens plate at a first angle relative to an axis normal to the second plane of the lens plate; and
characterized in that the mask pattern (<NUM>) is configured to focus second waves incident on the lens plate (<NUM>) through diffraction to the first region of the antenna array (<NUM>), the second waves being incident on the lens plate at a second angle relative to the axis, the second angle being different from the first angle;
and wherein the mask pattern is defined by an interference pattern produced by the superposition of two mask patterns.