Improved gain roll-off for hybrid mechanical lens antenna phased arrays

Abstract

A hybrid mechanical lens array antenna is described that can be configured with multiple lenses in different orientations and arrangements within the array to control and enhance performance at different scan regions. This can include adding a second-stage array (skirt) at a large tilt angle, tilting the first-stage array, tilting individual lenses within the first-stage array, or any combination. While keeping the number of lens modules (and therefore cost and power consumption) constant, these design choices have the effect of changing the system height, reducing boresight gain, and increasing scan gain, with each option presenting a different trade-off between height, scan, and boresight performance.

Description

[0001] Related applications

[0002] This application claims priority to U.S. Provisional Application No. 62 / 842,905, filed May 3, 2019, the entire contents of which are relied upon and incorporated herein by reference. Technical Field

[0003] The present disclosure relates to methods and systems for improving the gain roll-off of scanning of hybrid mechanical lens antenna phased arrays used for satellite or terrestrial communications. The present disclosure more particularly relates to methods and systems for configuring lens elements with various tilt and rotation arrangements. Background Art

[0004] Arrays of essentially planar elements suffer from gain reduction when scanning in elevation, primarily due to the reduction in projected antenna aperture area in the scan direction. Gimbaled parabolic antennas and gimbaled flat panel antennas overcome this gain reduction by using two-dimensional mechanical motion to continuously point the entire antenna in the desired scan direction. These gimbaled solutions result in very high-profile terminals that can be problematic or undesirable in some applications.

[0005] A phased array panel configured for electronic steering along one axis can be rotated to produce an antenna that covers all azimuth and elevation plane scan ranges achievable for the panel. In this way, the azimuth scan axis is mechanically controlled and the elevation axis is electrically controlled. This reduces the height of the dual-gimbaled solution but introduces scan loss for far elevation scan angles. The elevation plane scan range can be increased (or scan loss reduced / far scan gain improved) by tilting the panel toward the ground plane in the same plane as the elevation plane scan axis. This increases the height but reduces the effective elevation plane scan angle for pointing at targets near the ground plane.

[0006] Single-axis electrically steered panels are simpler and cheaper than full 2D scanning phased arrays, but have narrower azimuth beamwidths, which maintain high requirements on the pointing accuracy and response time of the mechanical actuators.

[0007] Phased arrays of electrically reconfigurable RF lens modules, such as the one in Scarborough et al., US Pat. No. 10,116,051, offer numerous advantages in terms of power consumption and parts count over conventional phased arrays used for satellite communications (SATCOM), radar, and other purposes. Summary of the Invention

[0008] The present disclosure generally relates to a radio frequency lens array that employs tilted elements, tilted subarrays, and / or a degree of mechanical azimuth scanning of all or a subset of lens elements. The addition of mechanical rotation allows for a reduction in the required scan range of each lens element and, therefore, the number of feeds per lens element. The azimuth scanning provided by the mechanical rotation also enables various configurations of tilted elements and tilted arrays. Tilting individual lens elements and / or tilting the array provides improved scan gain performance compared to standard planar phased arrays while maintaining a low profile compared to gimbaled antennas.

[0009] In the simplest case, a planar array of multiple lens modules is mechanically rotated. This configuration allows for a significant reduction in the scan range and, therefore, the number of feeds required for each lens element. The elements themselves primarily provide elevation scanning with a limited azimuth scanning range. The primary azimuth scanning is provided by mechanical rotation. Unlike standard phased arrays that are configured for single-axis scanning, the lens array maintains a degree of two-dimensional scanning capability within the beamwidth of the lens element pattern (typically 5-15 degrees). In this way, the antenna can be electrically scanned within any + / - 5 degree cone at all points on a line between 0 and 65 degrees parallel to the axis with azimuth = 0 degrees relative to the panel itself (for example).

[0010] To improve the scanning gain performance of the above configuration, the array can be tilted towards the ground plane at a specific azimuth angle. This provides a larger projection area of the array facing the scanning direction, thereby increasing the scanning gain.

[0011] Alternatively, or in combination with the tilted array described, each element within the array can be tilted towards a specific azimuth angle. This configuration reduces the scanning requirements of each lens element, thereby increasing the element pattern gain at far scan angles.

[0012] Another configuration has two separate lens arrays: a primary array and a secondary array. Each array can be configured with various combinations of array tilt, lens tilt, and mechanical rotation to focus scanning performance on different angular regions.

[0013] In one configuration, the first-stage array has planar elements that scan in both azimuth and elevation. A second-stage lens array surrounds the first-stage array, with the lenses tilted outward from the center of the antenna to supplement gain at far scan angles (greater than 60 degrees). Neither array uses mechanical motion.

[0014] Another configuration of the described antenna utilizes mechanical movement of both the first-stage array and the second-stage array. The first-stage array can have planar elements, tilted elements, or a tilted array. The second-stage array is configured along the perimeter of half of the first-stage array, with all elements facing the same azimuth. Each element in the second-stage array contributes additional gain performance at a specific azimuth, while mechanical rotation of both the first-stage array and the second-stage array provides azimuth scanning. The feeds under the first-stage array and the second-stage array can be reduced to a single row of feeds or less, so that each element scans primarily in elevation, while mechanical rotation scans in azimuth.

[0015] Another configuration tilts each individual lens to various independent angles. The tilted variant provides grating lobe reduction because there is no single, consistent element pattern, thus constructive interference occurs.

[0016] In all described cases, the transmit and receive signals from both the first and second stage arrays are combined to provide a single beam. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings are incorporated into and constitute a part of this specification. It should be understood that the accompanying drawings illustrate only some examples of the present disclosure, and that other examples or combinations of various examples not specifically shown in the drawings may still fall within the scope of the present disclosure. The examples will be described in more detail using the accompanying drawings, in which:

[0018] Figure 1 (a)-1(c) show a hybrid mechanical lens array capable of azimuth rotation, consisting of multiple lens modules located within a radome and a housing, and related graphs.

[0019] Figure 2 Figure 2 is a single lens module showing the RF lens, feed, feed plate, and mounting structure.

[0020] Figure 3 (a)-3(h) show several variations of the feed layout and associated scan patterns of the lens module, and illustrate the effect on the accessible scan range of a single lens, where Figure 3 (a), (c), and (e) are top views. Figure 3 (g) is a stereogram.

[0021] Figure 4 (a)-(c) show an improved hybrid mechanical lens first stage array with an additional second stage array ("skirt") of lens elements tilted toward the ground plane to extend the scanning performance of the antenna, and the associated graphs.

[0022] Figure 5(a)-(l) show variations of the hybrid mechanical lens array and different methods and combinations of tilting the first-stage array and the second-stage array of the lens module, as well as related graphs.

[0023] Figure 6 (a)-(c) show a hybrid mechanical lens array and related graphs, which has a first-stage array and two second-stage arrays pointing in opposite directions to allow selective gain to be added to either side of the array and increase operational flexibility.

[0024] Figure 7 (a)-7(c) show the effect of adding a lens skirt around a planar array without mechanical rotation, and the related curve graphs. DETAILED DESCRIPTION

[0025] The present disclosure relates to specific design enhancements to lens array antennas, such as the planar lens arrays of, for example, U.S. Patent No. 10,116,051, to support design simplification, cost reduction, and increased design flexibility around the tradeoff between boresight and scanning antenna gain performance. The entire contents of the '051 patent are incorporated herein by reference.

[0026] refer to Figure 1 (a), 1(b), shows the base hybrid mechanical lens array antenna assembly 101 (side view Figure 1 (a), top view Figure 1 (b)). The antenna is referred to as a hybrid antenna because it uses a combination of electrical beamforming and mechanical steering to direct the beam across the field of view. Antenna 101 includes a substantially planar lens array 120, a housing 105, a rotating platform 109, and a rotating actuator 107. The lens array 120 is formed from a plurality of lens modules 121 (sometimes referred to below as lenses) that are arranged substantially planar with respect to one another so that the array 120 is substantially planar, i.e., using aspheric lenses that are tiled on a plane. In an example embodiment, the lens modules 121 can have a flat bottom surface and a slightly curved or curved top surface, but the size of each individual lens module provides a substantially planar overall combined top surface of all lens modules 121. Reference Figure 1 (b) The lens module 121 may be circular, but any suitable shape may be used, such as a hexagonal shape. The actuator 107 rotates the array 120 about the vertical axis of 101, so that the antenna 101 can point the beam to any azimuth direction of the lens module 121, which is capable of scanning only on a limited subset of azimuth axes. The array 120 can be configured to be tilted at a fixed angle by the rotating platform 109 when rotated by the actuator 107 in different applications, as will be described below with respect to Figure 4-7Any suitable actuator 107 may be used, such as the actuator shown in U.S. Publication No. 2020 / 0091622, the entire contents of which are incorporated herein by reference.

[0027] Antenna 101 is mounted on a flat surface below a support platform 103. For example, support platform 103 can represent a tower, a building roof, or the top of a car, boat, bus, or other vehicle on which the antenna may be mounted. Platform 103 can be, but does not need to be, horizontal, in which case the terminal's boresight direction and scan angle are related to the platform's orientation and the resulting orientation of antenna 101. Antenna assembly 101 also includes a housing 105, which mechanically supports the rest of the structure (but is not RF transparent), and an RF-transparent radome 111, which is removably attached to 105, protecting the antenna from the elements and allowing RF signals to propagate through. Housing 105 can be directly connected to platform 103 via bolts or other fastening means. Together, housing 105 and radome 111 form a closed or sealed enclosure that houses the antenna (e.g., lens 121, platform 109, and actuator 107) to prevent moisture, dust, and environmental debris from interacting with the antenna's electrical and mechanical components.

[0028] The rotating platform 109 can be relatively thin and have a flat top surface and a flat bottom surface. The lens array 120 is mounted to the top surface of the rotating platform 109 so that the flat bottom surface of the lens module 121 engages the flat top surface of the rotating platform 109 directly or indirectly (for example, the lens module 121 can be located on a flat substrate and / or coupled to a flat substrate). The rotary actuator 107 has a base member and a connector extending upward from the base. In one example embodiment, the connector can pivot and / or rotate relative to the base member. The connector has a flat top surface that is fixedly connected to the flat bottom surface of the rotating platform 109. In another example embodiment, the connector can rotate relative to the base member, but does not pivot, and instead the rotating platform 109 is fixedly connected to the flat top surface of the connector at a fixed or adjustable angle.

[0029] Thus, the lens modules 121 in the array 120 are fixedly mounted on the rotating platform 109 and face substantially orthogonal to the plane of the rotating platform 109 and the support platform 103. The beams transmitted by these lens modules 121 are also substantially orthogonal to the plane of the rotating platform 109 and the support platform 103. The rotating platform 109 is fixedly mounted to a connector of an actuator 107, the base of which is fixedly mounted to the bottom surface of the housing 105. The rotating actuator 107 pivotally and / or rotationally mounts the rotating platform 109 to the housing 105, which in turn is fixedly mounted to the support platform 103. In particular, as Figure 1 As shown by the arrow in (b), the rotating platform 109 can axially rotate around the central axis of the antenna 101.

[0030] Figure 1 (c) shows the gain curve (plotted in polar coordinates) versus the scan angle θ. This scan curve is shown at a nominal φ value and will be the same for each φ (azimuth) angle as the array 120 is oriented in different directions by the rotating actuator 107. This allows lens modules within the array to use feeds that only allow scanning over a subset of azimuth angles (see Figure 1 (b) and Figure 1 (c)) (i.e., the lens cannot scan over 360 degrees but only over, for example, + / - 90 degrees in azimuth (φ). Using only enough feeds to support the limited azimuth scan allows the total number of feeds to be reduced and optimized (and therefore the cost) while maintaining the full antenna scan range with the help of the mechanical actuators. The graph shows that for this lens arrangement, the highest gain of the antenna is at boresight (θ = 0 degrees), where the gain drops smoothly to a maximum usable scan angle of about 65-70 degrees.

[0031] Similar to most electrically steered antennas, a gain drop of 6 to 10 dB between boresight and 70 degrees is common. This reduced gain during scanning is a result of a reduction in effective aperture area (the projected area of array 120 when viewed from 70 degrees is smaller than at smaller scan angles). The reduced gain indicates that signals received at scanning angles relative to boresight have lower signal strength. This general behavior is expected for all beam-steering antennas and is not unique to this antenna.

[0032] refer to Figure 2 , the lens modules 121 themselves each have an RF lens 201, a feed plate 203, a plurality of feeds 205, and a mounting structure 207 by which the module 121 is attached to the rotating platform 109. The lens 201 is shown as having a circular profile, and the feeds are closely spaced from the lens, but any suitable feed profile shape and spacing may be provided within the scope of the present disclosure. For example, different profiles and non-zero gaps between the lens 201 and the feed plate may be utilized.

[0033] refer to Figure 3 , shows different example configurations and arrangements of feeds 105 that can be used with the lens array antenna 101. In each lens antenna (e.g., lens module 121 in lens array 120) or reflector antenna, the position and number of feeds determines the range of angles at which the resulting antenna beam can be pointed. For example, a typical reflector antenna with a single feed fixed at the focus of a parabolic reflector can produce a single beam orthogonal to the reflector. In the same way, a lens module 121 with a single feed at the center of the focal region can produce a beam orthogonal to the lens. However, moving the feed laterally within the focal region causes the beam to move within the focal region by an angle of θ / φ related to the x / y position of the feed. Adding multiple feeds within the focal region of the lens allows for real-time selection of a particular feed to generate a beam in a desired direction, as well as combining signals from adjacent feeds to allow fine-tuning of the beam direction and properties. In the following discussion, Figure 3 (b), (d), (f), (h) are top views of the θ / φ spacing, showing the accessible scanning angles for the relevant feed configurations.

[0034] exist Figure 3 In (a), completely filling the focal area 303 of the lens allows it to point the beam in any direction within the lens' field of view. As shown, the circular focal area 303 on the feed plate 301 is completely filled with feed. The available scanning range and relative gain strength 303 of the lens module 121A using the feed plate 301 are given by Figure 3 (b) shows a graph where the θ / φ plot is shaded for all combinations of θ / φ where the lens can point the beam, with the darkest shading where the signal is strongest. The signal is on the boresight ( Figure 3 b) since the lens has its strongest gain at zero scan (θ = 0°).

[0035] In all cases, the feeds form a regular or generally uniform (hexagonal or rectilinear) grid, where the spacing of the feeds depends on the characteristics of the lens and is typically (but not exclusively) spaced approximately half a wavelength apart at the operating frequency of the antenna for optimal scanning performance and resolution of the resulting beam.

[0036] and Figure 3 (a) Several examples of alternative feed arrangements for reduced feed count and cost for reduced angular scan coverage. Broad categories are given in Figure 3 (c), (e) and (g) show that the corresponding angular scanning range is Figure 3 (d), (f) and (h) are shown.

[0037] Reference Figure 3(c) Lens module 121b with feed plate 311 shows approximately half of the focal region 303 filled with feeds 205, offering the benefit of lower cost (due to the reduced number of supported feeds and the required circuitry) compared to 121a. More specifically, feeds 205 are arranged in a semicircular pattern in the upper half of feed plate 301. This configuration enables a scanning range 313 covering approximately the upper hemisphere, plus a small area in the lower hemisphere. This lens module 121b cannot scan the φ spacing (limited to electronic scanning only for -90° <= φ <= 90°, as shown) unless mechanically rotated by adding an azimuth plane via a rotary actuator 107 beneath the entire array. However, the ability to perform two-dimensional electronic scanning within the upper hemisphere, as shown, significantly reduces the scanning speed and accuracy required of the mechanical actuator 107.

[0038] In this case, actuator 107 can rotate lens 121b to track the target's movement sufficiently to keep the desired beam target within addressable area 313, without the need to track the target satellite or communication target with the 0.2-degree accuracy required by conventional gimbaled antennas for SATCOM purposes. Even with substantial (>1-5 degrees) pointing errors in the mechanical actuator, the antenna as a whole will meet the required accuracy and fast scan response time through electronic scanning, accessing the full range of β angles through the rotation supported by actuator 107. A full antenna 101 constructed using this module 121b can support multiple beams connected to different satellites, as mechanical rotation of the array 120 including module 121b only requires pointing the center of the coverage area toward the midpoint of two or more satellites. Any two or more configurations of three or more satellites (particularly geostationary satellites that are always located fully north or fully south of the antenna) can be simultaneously addressed using this configuration.

[0039] refer to Figure 3 (e) The number of feeds 205 can be further reduced, as shown in module 121c using a feed plate 321 that uses only a single row of feeds starting near the center and extending to the edge of the focal region 303. Figure 3 As shown in (f), in coverage area 323, this configuration allows lens module 121c to scan only within a narrow azimuth (β-axis) cone of + / - 5-15 degrees (depending on the lens size and other properties relative to the wavelength), rather than over the entire scanning angle range supported by lens 201 and focal region 303. For this lens module 121c, the dependence on azimuth is much stronger than for 121b, and only a single beam is reasonably usable for a single target. Multiple beams can be generated, but they need to be within + / - 5-15 degrees of each other in the azimuth plane, which would be a more restrictive constraint.

[0040] When the lens module is tilted so that the visual axis direction of the lens itself is at a non-zero scanning angle θ in the elevation plane relative to the rotation axis and the visual axis direction of the antenna as a whole, case 121c ( Figure 3 (e)) is possible. If the lens module 121d ( Figure 3 303 。

[0066] If the feed row 205 below the lens is pointed downwardly toward ground level (or any angle θ greater than 0 degrees, but typically between 45 and 70 degrees), the feed row 205 below the lens can be moved to the center of the focal region 303 and still cover the same angular range. The benefit of tilting the lens and moving the feeds to match is that the lens operates at a lower scan angle θ on average, and thus operates with increased gain. That is, the feeds 205 on the feed plate 331 for the tilted lens module 121d are adjacent to each other at the center of the focal region and do not extend to the edge of the focal region 303, rather than extending from the center of the focal region to the edge of the focal region as in 121c. This moves the location of the highest gain obtained from the lens module 121d in the elevation plane. As shown in the coverage area 333, the highest (darkest shaded) gain occurs from 0 to θ max As follows, Figure 4-7 As discussed more fully, the tilt angle of the lens controls the angle of maximum gain of the element pattern.

[0041] In all of these cases, reducing the number of feeds 205 by removing feed elements from lens assembly 121a (for example) to obtain a modified configuration (such as lens 121c) reduces the scan range of lens module 121, but does not directly reduce or affect the gain of the lens module within the remaining accessible scan range. Since a feed is only enabled when the antenna is pointed in the direction covered by the feed, removing a feed simply means that the feed cannot be enabled (meaning that the antenna cannot be pointed in the direction supported by the feed), while the remaining feeds can be selected and operated normally. Any situation where the scan range is limited in the azimuth direction then requires mechanical rotation of the lens, feed, or the entire array (via actuator 107) in order to point the beam to any position within the normal scan range of the lens (i.e., scan in the direction corresponding to the feed that has been removed). In these cases, any necessary movement can be accomplished using low-resolution, relatively low-accuracy rotational motion of a single axis driven by rotary actuator 107, rather than the multi-dimensional, high-precision actuators required for gimbaled SATCOM parabolic reflector antennas. Here, the low resolution and accuracy required are evaluated relative to that of a multi-axis gimbaled satellite communication dish antenna, which requires accuracy to be consistently better than 0.2 degrees on all axes and has very high constraints on tracking speed and acceleration to track both platform 103 and potential satellite motion.

[0042] refer to Figure 4 , another example embodiment of the antenna assembly 401 ( Figure 4 (a) Side view, Figure 4 (b) shows the top view of the lens module 121 in the array 120 is divided into a plurality of lens modules 121c ( Figure 3 (e), although it can also be used with Figure 3 The first stage array 421 (used together with the configuration of lenses 121 shown in (a), (c), and (g)) and the second stage array or skirt array 423 composed of a plurality of tilted lens modules 121d. The rotating platform 409 has a first stage portion 409a and a second stage portion 409b. The second stage portion 409b is angled or tilted at an elevation relative to the first stage portion 409a, and specifically, the second stage portion 409b is angled downward relative to the first stage portion 409a. The first stage portion can be a thin, flat, planar plate to which the first stage array 421 of the first stage lens modules 121e is mounted. The first stage portion 409a is in a first stage plane that is substantially parallel to the plane of the bottom of the housing 105 and the plane of the support platform 103. The second stage portion 409b is a thin, flat, planar plate to which the second stage array 423 of the second stage lens modules 121d is mounted. The second stage portion 409b forms a skirt around the left side (in the embodiment shown) of the array in a second stage plane that is angled or inclined relative to the first stage plane.

[0043] Therefore, in Figure 4 In an exemplary embodiment, the second stage portion 409b extends partially around the outer periphery or peripheral portion of the first stage portion 409a of the rotating platform 409. The second stage portion 409b can have a curved shape, such as a partial C-shape, or can have a crescent shape or other suitable shape. The first stage portion 409a and the second stage portion 409b together form a complete circle, but any suitable size and shape can be used, regardless of whether the shapes and sizes of the portions 409a, b match or align with each other. And the first stage portion 409a can be integral with the second stage portion 409b, or separate from the second stage portion and coupled to the second stage portion 409b. In addition, the second stage portion 409b can be movable from a first position aligned with and coplanar with the first stage portion 409a and a second position angled or tilted relative to the first stage portion 409b, such as around a hinge, or can be fixed in place.

[0044] like Figure 4As further illustrated in the example embodiment of FIG. 1 , the second stage portion 409b can be arranged so that the feed and scan range defined by the feed plate 331 in the second stage lens module 121d are aligned with the scan axis of the row of feeds 205 on the feed plate 321 of the first stage lens module 121c in the first stage array 421. Thus, the second stage portion 409b is to the side and below the first stage portion 409a. Both arrays 421 and 423 continue to be supported and rotated with the rotating platform 409. Signals from the first and second stage array elements 121e, f are combined to form a single beam during transmit or receive operations. Also, while a single second stage array 423 is shown along only a portion of the perimeter of the first stage array 421, any number of second stage arrays 423 may be provided, either continuous with and adjacent to the first stage array 421 (as shown) (i.e., as close as possible to be adjacent to and / or contact the first stage array), or separated from the first stage array 421 by a gap or distance and extending along an outer periphery of the first stage array 421 or a smaller portion of the first stage array 421 than shown.

[0045] The effect of separating into two arrays 421, 423 and configuring the second stage array 423 as a skirt that partially surrounds the perimeter of the array is that at scan angles close to the tilt angle of the skirt (typically between 45 and 70 degrees relative to the boresight), the lens modules 121 d in the second stage (skirt) array 423 are nearly aligned with the desired beam and therefore do not suffer the same scan loss as the lens modules in the first stage array 421. Thus, the first stage portion is in the first stage plane and the second stage portion is in the second stage plane, and these planes are at an acute angle of approximately 45-70 degrees to each other. Thus, these planes are offset from each other at an angle. Figure 4 As shown in (c), due to the reduced number of boresight-directed lenses, the boresight gain 425 of the first-stage array 421 is reduced compared to the performance 125 (shown as a dashed line) of the original planar reference array 101. However, the scan gain is significantly improved. Although the number of second-stage lenses 121d in the skirt can be relatively small compared to the first-stage lenses 121c, the larger scan loss seen between (e.g.) 0 and 70 degrees is sufficient to allow a smaller number of lenses to add a significant performance boost at long scan angles. This has the effect of flattening the gain roll-off curve and increasing the scan angle, for which the gain is high enough to meet a given threshold (such as 3dB, 4.5dB, 7dB, etc.).

[0046] An interesting result is that the worse the raw roll-off (difference between boresight and scan gain) of the lens module itself, the better the impact and gain improvement that can be achieved when scanning the skirt second stage array 423. This means that the skirt array 423 should be scanned at the same θ as the first stage array 421. maxThe skirt is targeted at or near the edge of the first-stage array (in 333) to maximize the improvement while minimizing the sacrificed boresight gain. This means that targeting the skirt at low scan angles, such as 30 degrees, will provide little noticeable benefit, as the scan loss at 30 degrees is typically small to moderate, and targeting the skirt array beyond the scan range of the first-stage array 421 (such as approximately beyond 70 degrees or even 75-85 degrees) will require the skirt array to be very large in order to maintain performance, as it will no longer assist the first-stage array. For these reasons, the optimal angle for the skirt is between 45 and 70 degrees, as smaller angles show less benefit, while larger angles are beyond the support range of the first-stage array.

[0047] It should also be noted that the relative sizes of the first-stage array 421 and the second-stage array 423 (measured in terms of the number of lens modules and aperture area) are subject to some constraints. The skirt has the greatest impact when the number of lenses in the skirt is approximately 3-9dB (1 / 2 to 1 / 8) of the number of lenses in the first-stage array. Depending on the number of modules in the first-stage array 421, this can be achieved with one or more stacked skirt layers; a single layer is more convenient, as multiple layers (while possible) would increase the height of the antenna and are therefore less ideal. Figure 4 As shown, this places an upper limit on the size of the array that can practically include an effective single-layer skirt. The number of lenses increases with the square of the aperture diameter, but the number of lenses available in the skirt (proportional to the circumference) increases only linearly with the aperture diameter - in larger arrays, the skirt has so few elements relative to the first-stage array that it has little effect and is useless. In one exemplary non-limiting embodiment, the fraction of lens modules in the second-stage array 423 is between 12-35% of the number of modules in the first-stage array 421. For example, 12 out of 50 lenses, or 8 out of 38 (e.g., 8 out of 100) are used. Figure 4 b) is a reasonable ratio.

[0048] In order to extend the elevation plane scanning range of the antenna beyond the range of a single lens 201 and lens module 121, the first stage array needs to be modified. Figure 5 , shows a set of four example variations that increase the scanning range of the terminal. For individual lens modules that can scan to 60 or 70 degrees, these methods can enable the antenna to scan to 80 or 90 degrees in the elevation plane with good performance.

[0049] Modified antenna assembly 500( Figure 5 (a) Side view, Figure 5 (b) The top view uses the first-stage array 521 and the second-stage array 523, but in the first-stage array 521, the rotating platform 509 is modified to move all the lenses 121c ( Figure 3 (e)), although this can also be combined with Figure 3 (a), (c), and (g) are used together with the configuration of lens 121 shown in Figures 1 and 2.) The lens 121c is slightly tilted toward the ground plane. As shown, the lens 121c is positioned at an angle or tilt relative to the bottom surface of the housing 103 and the support platform 103. As shown, the top surface of the platform 509 is formed with angled ridges or shelves arranged in a zigzag pattern, and the lens 121c is mounted to the angled side of the top surface. Of course, any other suitable technique can be used to position one or all of the lenses 121c at an angle relative to the center plane of the platform 509 or the bottom plane of the housing 105 or the support platform 103. For example, the top surface of the rotating platform 509 can be flat and the shelves can be mounted to the top surface of the rotating platform 509, or the lens module 121c can have a base that angles the lens 201.

[0050] The angled lens 121c moves the coverage area toward the ground plane by the tilt amount. Figure 5 (c) shows coverage 525. There is a limit to how much tilt can be applied to each lens individually without one lens blocking an adjacent lens, and due to the geometry of the lenses, this approach rarely yields overall improved performance beyond 75 degrees. As in antenna assembly 401, the second-stage array 523 in assembly 500 continues to support scan response at far scan. The significant effect of this modification is that the gain is no longer highest at the antenna boresight.

[0051] Example variations of antenna assembly 530 ( Figure 5 (d) is a side view, Figure 5 (e) shows the effect of using the rotating platform 539 to tilt the entire first stage lens array 531 while maintaining the second stage lens array 533. That is, in one non-limiting embodiment, the platform 539 is fixedly mounted to the actuator 107 at an angle. In another embodiment, the actuator 107 can tilt or pivot the rotating platform 539 so that one end of the rotating platform is higher than the other end. Tilting the entire array significantly increases the height of the system, but does not cause blockage between adjacent lens modules 121c in the first stage array. Gain performance 535 ( Figure 5 (f)) is slightly better than tilting lens 525 alone, but shows similar performance.

[0052] The above two methods can be used in combination; Example variant antenna assembly 540 ( Figure 5 (g) is a side view, Figure 5The top view in (g) shows the effect of tilting the entire first stage array 541 except for the second stage skirt array 543 and the lenses 121c within the array. Both the first stage array 541 and the second stage array 543 are supported in the desired position by a rotating platform 549. This approach allows the antenna scan range to be extended without obstruction between adjacent lenses 121c in the first stage array 541, and also supports scanning performance in the middle of the scan range. As the scan range increases, the position and height of the housing 105 and the emission angle response of the radome 111 may become limiting factors. As shown in the representative coverage diagram 545 ( Figure 5 As shown in (i)), this configuration offers the opportunity to maximize performance at the scan, in exchange for significantly reduced performance at the boresight.

[0053] Another example variant antenna assembly 550 ( Figure 5 (j) is a side view, Figure 5 The top view in (k) shows a combination of two first-stage arrays 551 and 552, where 551 is pointed at one angle and 552 is tilted at a different angle, and finally a skirt second-stage array 553 is applied. This combination (and other similar combinations) can be adjusted to produce a specific scan curve; the coverage 555 ( Figure 5 (l)) shows an example of nearly flat gain between 20 and 70 degrees. Variations in the relative number of lens modules 121c and 121d in each array 551, 552, 553, as well as the included tilt or other effects, can be used to shape and control the gain roll-off experienced by the antenna 550 as a whole. Thus, as shown herein, lenses 121 within the same array (e.g., a first-stage array or a second-stage array) need not be pointed or angled in the same direction, but can be pointed or angled or tilted in different directions. That is, lens 551 is angled in a first direction and lens 552 is angled in a different direction, both of which are mounted on a rotating platform 559. Additionally, lens 551 can be angled in the opposite direction as lens 552 (e.g., to the right in the illustrated embodiment).

[0054] refer to Figure 6 , the antenna 601 can be constructed using a single first-stage array 621 of the lens module 121 and two second-stage arrays 622 and 623 oriented in different azimuth directions, where ( Figure 6 (a) Side view, Figure 6(b) is shown in opposite orientations (β = 0 degrees and β = 180 degrees). In this case, the skirt array 622 can be composed of lens modules configured for reception only, and the skirt array 623 can be composed of lens modules configured for transmission only. These limitations may be to reduce cost or complexity, or due to fundamental limitations in the circuitry. By including transmit and receive skirts on opposite sides of the array, the end user of the antenna can choose to have performance in either receive enhancement 625 (by rotating the actuator 107 to orient the antenna toward the receive skirt 622) or transmit enhancement 626 (by rotating the actuator 107 to orient the antenna toward the transmit skirt 623) mode (refer to FIG. Figure 6 (c)). This configuration is of most interest in height-constrained applications where adding a second skirt layer capable of providing both transmit and receive performance is undesirable, but operational flexibility is required.

[0055] In each of the above cases, the rotating platform 107 is shown as an integral unit between the first and second stage arrays. In all cases, separate rotating platforms can be used for the first and second stage arrays (e.g., the first stage array is mounted to the first stage rotating platform, the second stage array is mounted to the second stage rotating platform, and the second stage rotating platform rotates independently of the first stage rotating platform (in the same direction or opposite directions)) to support each lens module as a whole or separately. The separate rotating platform (if used) can be formed integrally with the first platform, or separate and discrete from the first platform and fixedly, removably and / or dynamically rotatably coupled to the first platform. For example, one rotating platform can be concentrically positioned inside the other rotating platform, or on top of the other platform. Thus, each element can be at a fixed tilt, or dynamically adjustable tilt, in unison with each other element or separately. The lens elements in the second stage array are tilted at an angle that is the same as or different from the tilt angle of the first stage lenses. Both the first and second stage arrays are mechanically rotated to provide azimuth scanning.

[0056] As an extension of the skirt concept, the skirt second stage array can be applied to a fixed or non-rotating antenna 701 with a first stage array 721 (see Figure 7 (a) Side view and Figure 7 (b) top view), the first stage array consists of lens modules 121a, which have focal plane 303 completely filled with feed 205. Then the second stage skirt array 723 is added radially on the periphery of the first stage array 721, supported by structure 709, and consists of lens modules 121d with an elevation plane scan range adjusted to the skirt angle. As can be seen in the roll-off diagram 725, the effect of this arrangement of lens modules (see Figure 7(c) significantly reduces the boresight gain, but also flattens the gain roll-off to give a very flat response with the elevation plane scan angle θ centered about the boresight. Adding an additional skirt layer to the first stage array 721 or adding a radial tilt angle to the lens module 121 converts the skirt array into a dome array, which allows for further control of the roll-off curve in exchange for reduced peak gain and increased antenna height.

[0057] In each of the embodiments described above, the primary and secondary arrays each have standard circuitry and control capabilities to independently point one or more beams at commanded elevation and azimuth angles relative to the orientation of the rotating platform 109. In addition, a joint controller and circuitry is included to combine the signals from the separate primary and secondary arrays to form a single beam from the combined arrays.

[0058] In each of the embodiments described above, the mounting platform and support table are substantially planar members having a flat top surface, and one or more elements of the array are secured or coupled to the respective platform or support table. However, in other embodiments, the platform and support need not be planar.

[0059] Also note that regarding Figure 1-7 , the actuator 107 rotates the lens 121 and the platform 109, 409, 509, 539, 549 between a first position having a first azimuth angle and a second position having a second azimuth angle. The first azimuth angle can be different from, overlap with, or be a subset of the second azimuth angle, as desired for a particular application. The different positions enable a user to achieve a desired scanning coverage of up to a full 360 degrees. Also, the platform 109, 409, 509, 539, 549 can be secured to the actuator 107 at a first angle or a second angle different from the first angle. The first angle or position can have a first elevation angle, and the second angle or position can have a second elevation angle that is the same as or different from the first elevation angle. For example, with respect to Figure 3 (c), the actuator 107 can be Figure 3 (c) shows the lens in a first position in the upper half and the lens in a second position in the lower half rotating the lens 121b to provide full 360 degree scanning coverage.

[0060] Furthermore, in one embodiment, the actuator 107 can be manually rotated and fixed in position. The second stage portion of the rotating platform 409 can be formed at a fixed angle relative to the first stage portion of the rotating platform 409. However, in another embodiment, a processing device, such as a controller, processor, computer, etc., can be provided to control the rotation of the actuator 107 under user control or automatically. Furthermore, the second stage portion 409b of the rotating platform 409 can be pivotally or rotatably coupled to the first stage portion 409a of the rotating platform 409, such as via a hinge, and the user can manually rotate the second stage portion 409b to a suitable angle or plane relative to the first stage portion 409a between the first and second angles, or the processing device can control this movement automatically or under user control. Similarly, the top surface of the platform 509 can be integrally formed at a fixed angle, or can be pivoted relative to the platform 509 for separate adjustment, either manually or via a processing device.

[0061] The embodiments described above describe and illustrate arrays and apertures as circular or approximately circular. Circular arrays are convenient when using rotation because circular apertures are more efficient in terms of gain over the size of the area the rotating structure passes through (e.g., compared to a rectangular aperture). However, the details described above can be applied to arrays and antennas of any shape and profile.

[0062] Any frequency band can be used, and the most flexible system is one where the antenna and system can operate and listen at different frequency bands. However, electrically steerable antennas that operate at multiple frequencies are difficult and expensive to build. Therefore, most practical systems will operate at a single frequency band, with the most common communication system bands being Ka and Ku, which are used for VSAT operations.

[0063] The present disclosure, although primarily described for satellite communication purposes, may be applied to different applications in communications and remote sensing, such as reconfigurable or mobile point-to-point microwave links, radar, 5G, etc.

[0064] As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Similarly, the adjective "another," when used to introduce an element, is intended to mean one or more elements. The terms "comprising," "including," "having," and similar terms are intended to be inclusive, such that there may be additional elements other than the listed elements.

[0065] Furthermore, where the method described above or the method claims below do not explicitly require an order in which their steps must be followed, or where an order is not required based on the description or claim language, no particular order is intended to be inferred. Similarly, where a method claim below does not explicitly recite a step mentioned in the description above, it should not be assumed that the step is required by the claim.

[0066] It should be noted that the description and claims may use geometric or relational terms such as right, left, up, down, top, bottom, linear, curved, parallel, orthogonal, concentric, crescent, flat, planar, coplanar, etc. These terms are not intended to limit the present disclosure and are generally used for convenience to facilitate the description based on the examples shown in the figures. In addition, geometric or relational terms may not be exact. For example, due to, for example, surface roughness, tolerances allowed in manufacturing, etc., the walls may not be completely parallel to each other, but can still be considered perpendicular or parallel.

[0067] Those skilled in the art will readily appreciate the various applications of the present system and method. Therefore, it is not intended to limit the present invention to the specific examples disclosed or the exact construction and operation shown and described. On the contrary, all suitable modifications and equivalents may fall within the scope of the present invention.

Claims

1. An antenna system, comprising: a. A substantially planar phased array (120) of multiple radio frequency lens modules; as well as b. a mechanical actuator to which the plurality of RF lens modules are mounted; Its characteristics are: Each of the plurality of radio frequency lens modules is configured to electronically scan at a first azimuth angle; The mechanical actuator is configured to mechanically rotate the plurality of radio frequency lens modules to scan at a second azimuth angle, and the substantially planar phased array has a same scan curve for each second azimuth angle.

2. The antenna system according to claim 1, wherein The second azimuth angle overlaps or differs from the first azimuth angle to scan over a combined 360 degrees.

3. The antenna system according to claim 1 or 2, wherein: Each radio frequency lens module is individually tilted at an elevation angle relative to the mechanical actuator toward the first azimuth angle.

4. The antenna system according to claim 1 or 2, further comprising a rotating platform connected to the mechanical actuator, wherein: The phased array (120) is mounted to the rotating platform and the rotating platform is tilted relative to the mechanical actuator toward the first azimuth angle.

5. The antenna system according to claim 4, wherein: Each RF lens module is individually tilted at an elevation angle relative to the rotating platform toward the first azimuth angle.

6. The antenna system according to claim 1 or 2, wherein: The plurality of radio frequency lens modules are configured to electronically scan in an elevation plane.

7. An antenna system comprising: a. a first-stage phased array of a plurality of RF lens modules, each of the plurality of RF lens modules being configured to electronically scan at a first azimuth angle, and b. A second-stage phased array of multiple RF lens modules, wherein each RF lens module is tilted at an elevation angle and at a fixed angle relative to the first azimuth angle of the first-stage phased array.

8. The antenna system according to claim 7 further includes a mechanical actuator, wherein the multiple RF lens modules in the first-stage phased array and the second-stage phased array are mounted to the mechanical actuator, and the mechanical actuator is configured to mechanically rotate the multiple RF lens modules from pointing at the first azimuth angle to scanning at a second azimuth angle.

9. The antenna system according to claim 7 or 8, wherein: The elements in the second-stage phased array are mounted on the periphery of the first-stage phased array.

10. The antenna system according to claim 7, further comprising a mechanical actuator, wherein only the plurality of RF lens modules in the second-stage phased array are mounted to the mechanical actuator, and the mechanical actuator is configured to mechanically rotate the plurality of RF lens modules from pointing to scan at a first azimuth angle to pointing to scan at a second azimuth angle.

11. The antenna system according to claim 8, wherein: The second azimuth angle overlaps with the first azimuth angle to scan over a combined 360 degrees.

12. The antenna system according to claim 8 or 11, wherein: Each radio frequency lens module is individually tilted at an elevation angle relative to the mechanical actuator toward the first azimuth angle.

13. The antenna system according to claim 8 or 11, further comprising a rotating platform connected to the mechanical actuator, wherein: The first-stage phased array and the second-stage phased array are mounted to the rotating platform and the rotating platform is tilted toward the first azimuth angle relative to the mechanical actuator.

14. The antenna system according to claim 13, wherein: Each RF lens module is individually tilted at an elevation angle relative to the rotating platform toward the first azimuth angle.

15. The antenna system according to claim 7 or 8, wherein: The plurality of radio frequency lens modules are configured to electronically scan in an elevation plane.

16. An antenna assembly comprising: a. A platform having a first stage portion (409a) and a second stage portion (409b), the second stage portion being angled to be offset relative to the first stage portion; b. a first stage phased lens array mounted to the first stage portion (409a) of the platform, the first stage phased lens array having a plurality of first stage antenna lens assemblies; as well as c. A second stage phased lens array mounted to the second stage portion (409b) of the platform, the second stage phased lens array having a plurality of second stage antenna lens assemblies whereby the second stage phased lens array is angled to be offset relative to the first stage phased lens array.

17. The antenna assembly of claim 16, further comprising an actuator coupled to the platform for rotating the platform to provide azimuth steering of the first stage phased lens array and the second stage phased lens array.

18. The antenna assembly according to any one of claims 16 or 17, wherein the first-level portion (409a) has a first-level plane, the second-level portion (409b) has a second-level plane, the second-level plane is at an angle of 30-70 degrees to the first-level plane, and the second-level portion is below and to the side of the first-level portion.

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