Reflector antenna repointing apparatus and reflector antenna

Abstract

The present application relates to a reflector antenna repointing device and a reflector antenna, the reflector antenna repointing device comprising: a microwave lens receiving an input field and providing an output field; a mounting structure connecting the microwave lens to the reflector antenna and mounting the microwave lens above a feed horn; and an alignment feature at the mounting structure, the alignment feature being configured for setting a position and orientation of the microwave lens relative to the reflector antenna, the alignment feature defining a lateral shift of the output field relative to the input field perpendicular to an axis of the reflector; the reflector antenna repointing device being configured to repoint the input field from an old satellite to a new target satellite without manual fine tuning.

Description

[0001] Cross-references to related applications

[0002] This application claims the benefit of priority to U.S. Provisional Application No. 62 / 981,367, filed February 25, 2020, the contents of which are incorporated herein by reference in their entirety. Background Technology

[0003] The following references are incorporated herein by reference: US6075497, Chen et al., “Multiple-feed Electromagnetic Signal Receiving Apparatus”, filed June 30, 1997, granted June 13, 2000; US9722316, Haziza and Dedi David, “Horn lens antenna”, filed July 7, 2014, granted August 1, 2017; US10158177, Cook and Scott, “Antenna horn with suspended dielectric tuningvane”, filed March 11, 2016, granted December 18, 2018.

[0004] Satellite communications at microwave frequencies, whether one-way or two-way, allow for the distribution of large amounts of data over a wide geographical area, but require large antennas that must be precisely pointed at the desired satellite to maintain high signal strength. The most common satellite antennas used for microwave (C, X, Ku, Ka, and higher frequency bands) applications are horn-illuminated reflectors, center-fed or offset-fed parabolic (or near-parabolic) reflectors available in a variety of shapes, sizes, and operating frequencies.

[0005] Mobile platforms and ground terminals used for communicating with non-geostationary orbit (NGSO) satellites typically have motorized tracking systems and electronics to maintain connectivity when either the ground terminal or the satellite is in motion relative to the other. However, this hardware is very expensive. For fixed ground locations communicating with GEO (geostationary orbit) satellites, pointing a fixed antenna at the satellite once and locking it in place is both cost-effective and simple. However, a drawback of fixed reflectors is that changing the satellite to which the antenna is connected requires skilled or semi-skilled workers and tools. This reduces the ability of subscribers to change their service providers or broadcasters and also limits the ability of service providers or broadcasters to change satellites or operators for capacity, commercial, or other reasons. Ideally, while the cost of terminals and antennas remains low for the mass market, subscribers would have a simple way to repoint their own antennas from their original, current satellite to a new one without tools, tuning, or significant effort.

[0006] The present disclosure introduces a system and method by which unskilled personnel can use a microwave horn or lens on a reflector antenna by snapping or otherwise mating the microwave horn or lens to the horn in a controlled orientation to point the main beam of the reflector to connect to a different satellite.

[0007] Referring to FIG. 1, a parabolic reflector antenna 101 for SATCOM purposes has a shaped metal or conductive material reflector 103 of minimum one piece parabolic shape, a horn antenna 109 to feed or illuminate the reflector 103, and support structures 105, 107 to mount the components in the correct relative positions and secure the entire assembly to point rigidly at a satellite. A radome or cover 111 over the horn mouth protects the horn from water or debris intrusion. Some antennas will include an additional shaped or parabolic sub-reflector in the beam path to better control the illumination of the main reflector and / or to modify the shape of the main reflector. The least expensive antennas for Ku and Ka DTH most typically use an offset fed reflector which reduces blockage by the feed horn. The feed horn will commonly be highly integrated with low noise block (LNB) downconverter circuitry 113 and with mounting arms to support the LNB and feed. Fixtures are included on the back of the reflector, either pole or wall mounted, which allow the orientation of the feed assembly and reflector to be adjusted and then locked in place by bolts or other fasteners.

[0008] New subscribers to a broadcast or two-way satellite service either purchase an antenna 101 or are provided one as part of the service. While sometimes advertised as being able to be installed and pointed by the subscriber themselves, installation by the service provider is almost universal.

[0009] The reflector 103, while possibly mounted to a solid structure and securely locked in place, can become displaced from position due to wind, snow, or other events. Correcting this problem requires a truck roll, which means dispatching a trained technician with tools to properly re-point the antenna. The service visit is a significant expense to the service provider, even though the problem can only take a few minutes to resolve.

[0010] Changing the connected satellite when the antenna is not configured with multiple pre-pointed receivers requires knowledge, tools, and skills. Currently, there are smartphone apps and websites that provide guidance on how to point a satellite antenna, but most subscribers are not interested in doing this themselves. For this reason, service providers are locked into specific orbital slots by their subscriber base - the more successful the broadcaster, the less flexibility they have in trying to provide or modify a satellite from which the broadcaster provides their service.

[0011] Microwave lenses and prisms constructed of dielectrics, metamaterials, or metasurfaces are commonly used to control the radiation pattern or direction of an antenna. Microwave lenses use the same principles as optical lenses, but use materials that have desirable properties for radio frequencies rather than optical wavelengths. Different features and approaches have different benefits. Anti-reflective coatings are common but not universal in microwave lenses that are typically implemented as a quarter-wave plate or coating on the lens. Anti-reflective coatings are used to improve the impedance match of the signal traveling from free space into the lens material, and again to improve the impedance match of the signal leaving the lens. Because it is difficult to achieve the low dielectric constant desired for a good anti-reflective coating, there are many approaches to constructing such lenses, including the use of foams, textured surfaces, and 3D printing.

[0012] Beam shifters are a common device in optics, consisting of a polished parallel plate prism that can also be described as a piece of glass. When rotated at different angles relative to an incoming beam of light, the exit point of the light from the prism is laterally shifted a distance that is related to the angle of incidence of the light and the thickness of the prism. Such devices will include optical anti-reflective coatings and are used as adjustment points in optical and laser workbenches to align different parts of the system. The Thorlabs XYT / MA Post-Mountable Tweaker Plate, 2.5 mm thick (optical beam shifter), thorlabs.com provides a typical example. SUMMARY

[0013] A reflector antenna re-pointing device for use with a reflector antenna. The reflector antenna re-pointing device has a microwave prism that receives an input field and provides an output field. The device also has a mounting structure configured to connect the prism to the reflector antenna. And, the device has an adjustable alignment feature at the mounting structure to set an adjustable position and an adjustable orientation of the microwave prism relative to the reflector antenna, where the alignment feature defines a lateral shift of the output field relative to the input field. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 shows a conventional parabolic reflector antenna.

[0015] Figure 2 shows the principle of using a prism to re-direct a beam from a reflector of a current satellite to a new target satellite.

[0016] Figure 3 A parabolic reflector antenna is shown equipped with a re-directing prism that snaps into place above the receiver.

[0017] Figure 4 Components of the system are shown.

[0018] Figure 5 shows multiple candidate prism implementations.

[0019] Figure 6 Geometric considerations for prism size and structure are shown.

[0020] Figure 7 The orientation and angle that a terminal must point to relative to the original satellite for a representative pair of satellites serving a geographic area are shown.

[0021] Figure 8 (a) shows how the installation of a prism allows the same prism to support multiple scan angle adjustments, with the alignment and prism in a first position E.

[0022] Figure 8 (b) is a side view of Figure 8 (a).

[0023] Figure 8 (c) is similar to Figure 8 (a) with the alignment and prism in a second position A. DETAILED DESCRIPTION

[0024] In describing the illustrative, non-limiting embodiments shown in the drawings, specific terminology will be used for the sake of clarity. However, the disclosure is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes all technical equivalents that operate in a similar manner to accomplish a similar purpose. Several embodiments are described for illustrative purposes, it being understood that the specification and claims are not limited to the embodiments shown and that other embodiments not specifically shown in the drawings can also be within the scope of the disclosure.

[0025] Turning to the drawings, Figure 3A reflector antenna 200 is shown with a reflector re-pointing device 201. The reflector re-pointing device 201 enables the main beam of the reflector antenna 200 to be steered at a fixed and determined angle relative to the original angle of the antenna 200 without the re-pointing device 201 installed. The reflector re-pointing device 201 is mounted above the feed horn 109 of the reflector, its position and orientation controlled by the device itself. The position and orientation are set so that for a reflector antenna 200 within a given geographic location that has been pointed at a particular satellite 213 (Figure 2(a)), the installation of the reflector re-pointing device will cause the antenna to be converted to instead point at a separate particular satellite 215, without the need to physically move the reflector 103 or the feed horn 109. A single device 201 or different orientations of the same device 201 can enable scanning within a range of + / - 10 degrees of the nominal angle. This is not a hard limit, but further scanning will result in more significant performance degradation compared to the nominal case without the reflector re-pointing device installed. As a specific example, by installing a device 201 that is specifically designed to shift the feed 109 by 5 degrees, an antenna 200 located within, for example, a 50 mile range of Washington D.C. and configured to receive signals from a satellite at 50°W can be converted to instead receive signals from a satellite at 45°W without the need for skilled installation or pointing calibration.

[0026] For convenience, the following sections describe signals and fields as being emitted from the antenna and reflector toward one satellite or another. The reciprocal behavior of emission from a satellite versus reception by an antenna is not described, but is entirely analogous to the cases described.

[0027] Referring to Figure 2(a), the horn antenna 109 is positioned in typical operation so that the aperture of the horn is at the focal point 203 of the parabolic reflector 103. In typical operation shown in Figure 2(a), the system 101 is oriented so that the signal or antenna field 205 from the horn interacts with the reflector 103 and is directed toward the desired target satellite 213, forming a beam 207. Referring to Figure 2(b), steering the system 101 to form a beam 211 toward a different satellite 215 can be performed by re-orienting the entire antenna 101, but can also be performed by shifting the feed horn 109 away from the focal point 203 of the reflector 103. The antenna field 209 from the offset horn then interacts with the reflector 103 to form a beam 211 directed toward the alternate satellite 215. However, re-orienting the entire antenna 101 or physically moving the horn 109 both require skilled workers to perform and support for the movement in the design of the reflector, neither of which can be easily performed as a retrofit operation in most cases without tools.

[0028] Turning to FIG. 2(c), 3, a reflector re-pointing device 201 is added to the horn 109 at the focal point 203 of the reflector 103 to laterally displace the field 205 normally pointing a beam 207 to the primary satellite 213 to instead produce a beam 211 pointing to the backup satellite 215. Here lateral displacement indicates a direction perpendicular to the axis of symmetry of the parabolic reflector, which is also the direction of the feed support arm. The lateral displacement can be horizontal, vertical, or a combination of both, but should remain within a plane aligned with the original feed aperture perpendicular to the reflector axis to ensure that the apparent phase center continues to lie approximately on the focal plane of the reflector 103. The position of the feed aperture defines the starting point for all displacement comparisons. Lateral displacement of the angle of the field and potentially correction forces the reflector 103 to behave as if the horn 109 were in a different location, thereby producing the beam 211 in the new, desired direction.

[0029] Reference is now made to Figure 4 The reflector re-pointing device 201 has a microwave prism or prism 401 with optional anti-reflective coating features 403 at one or both surfaces (top and bottom surfaces) of the prism 401 in embodiments, a mounting system or features 407 designed to connect and secure the prism to the host horn 109, and a radome or other cover 405 to protect from the weather. All terms microwave prism, prism, microwave lens, and lens are intended to apply to the device 401, and the term prism is used in this disclosure to include microwave prisms. Figure 4

[0030] The construction of the microwave prism has many similarities in practice and in principle to microwave lenses including GRIN lenses. A prism denotes an optical device whose primary purpose is to bend or displace a beam or cone, beam, or other electromagnetic energy distribution, while a lens denotes an optical device whose primary purpose is to expand or contract a cone, beam, or other electromagnetic energy. There is no strict division between these two concepts, as prisms can also be designed to focus, and lenses can also be designed to bend energy. For this disclosure, prisms are considered more meaningful because the primary purpose of the device 401 is to bend and displace energy, rather than to expand or contract it, although some expansion or contraction can also be included.

[0031] The prism 401 and mounting features 407 are specific to the particular make or model of the reflector antenna 101 and accompanying horn 109, and will also be specific to the particular satellite 213, 215. The mounting features 407 can be, for example, fasteners such as bolts, nuts, screws, or adhesives.

[0032] As Figure 4 ​As shown, in one embodiment, the microwave prism 401 has a body 402 having a first prism surface 402a and a second prism surface 402b opposite the first surface 402a. The prism body 402 has a top, a bottom, and at least one side, and can have any suitable shape cross-section, such as a circular, square, or rectangular cross-section. The first prism surface 402a is at the top of the body 402, and the second prism surface 402b is at the bottom of the body 402. The first prism surface 402a and the second prism surface 402b are planar. The anti-reflective coating features 403 can be coatings applied to the first prism surface 402a and the second prism surface 402b. In one embodiment, the anti-reflective coating features have a top coating surface and a bottom coating surface, and the first coating feature 403a has a bottom coating surface that contacts the top prism surface 402a of the prism body 402, and the second coating feature 403b has a top coating surface that contacts the bottom prism surface 402b of the prism body 402.

[0033] In Figure 4 In one embodiment, the prism is a parallel plate prism. The first prism surface 402a is parallel to the second prism surface 402b. In addition, the flared side of the horn 109 forms a forwardly open mouth, and the forward edge of the flared side forms a planar forward perimeter. The horn 109 also has a central longitudinal axis that extends from the rear of the horn to the front of the horn. The first prism surface 402a and the second prism surface 402b are substantially parallel to the planar mouth of the horn 109, and perpendicular to the longitudinal axis of the horn 109.

[0034] In one embodiment, the horn 109 and the reflector re-pointing device 201 can instead be connected to a common support, such as a frame or housing, and the mounting system or features 407 can connect the reflector re-pointing device 201 to the support instead of to the horn 109.

[0035] The prism 401 functions by being positioned in a prescribed orientation close to or at the aperture of the horn antenna 109 enforced by the mounting features 407. In FIG. 5, when properly positioned, the prism 401 creates a lateral shift 507 in the corresponding positions of the input and output fields 505 entering and exiting the device relative to the original or undisturbed field positions 506 of the antenna field from the horn 109 in the absence of the prism 401.

[0036] The antenna fields emanating from the feed horn are not as highly collimated as the antenna fields from the laser (due to the much longer wavelength of the microwaves than the shorter wavelength of the laser), but rather these fields expand in a spherical or conical manner between the feed horn 109 and the reflector 103. Due to this difference between laser and microwave, the reflector re-pointing device 201 can include corrections to allow for the conical emanation of energy from the horn, unlike a simple planar beam shifter for optical purposes. For example, the reflector re-pointing device 201 can have a non-planar surface (particularly the bottom prism surface 402b and / or the top prism surface 402a) of non-zero optical power to correct for the field curvature and axial position of the effective phase center of the output field out of the re-pointing device 201.

[0037] The core operation of the prism 401 is to laterally shift the field compared to the position of the horn 109. This can be implemented in any suitable manner, some examples of which are shown and described in the embodiments of FIGS. 5(a) through 5(f) as various configurations of the reflector re-pointing device 201.

[0038] With reference to FIG. 5(a), the simplest option is to configure the microwave prism 401 as an optical beam shifter or parallel plate prism 401a formed of a uniform high dielectric constant. The prism 401 is held at a prescribed angle relative to the horn antenna 109, more particularly the first surface 402a and / or the second surface 402b are angled relative to the plane of the open mouth of the horn 109 and relative to the central longitudinal axis of the horn 109. This can optionally include an anti-reflection layer 403 to support higher performance. However, to produce the maximum lateral shift or offset 507, this embodiment can require the prism to be very thick, with a high field incidence angle (which limits the transmission efficiency), and a large dielectric constant ε. These factors combined make the prism option 401a bulky and unwieldy.

[0039] In FIG. 5(b), another prism 401b includes coupling and anti-reflection layers to more smoothly transition the direction of the signal through the structure with a series of one or more wedges 508. The prism 401b has a central body or central plate 502 that has a parallel shape, like the prism 401a, and one or more wedges 508 are connected (e.g., by adhesive) to or formed integrally with the central body or central plate 502, extending outwardly from the top and / or bottom of the central plate 502. A first set of one or more wedges 508a is arranged at a first side (top) of the body 502, and a second set of one or more wedges 508b is arranged at a second side (bottom) of the body 502.

[0040] The wedges 508 can have any suitable shape. However, in the illustrated embodiment, each wedge 508 is substantially triangular in shape, having a first planar primary surface facing the body 502, a second planar primary surface facing away from the body 502, and a small secondary surface. The bottom surface of the bottom-most wedge of the first set of wedges 508a contacts the top surface 502a of the body 502, and the top surface of each wedge contacts the bottom surface of the adjacent wedge. The top surface of the top-most wedge of the second set of wedges 508b contacts the bottom surface 502b of the body 502, and the bottom surface of each wedge contacts the top surface of the adjacent wedge.

[0041] Each wedge has an acute angle formed between the first and second primary surfaces. In one embodiment, the first set of wedges 508a has a combined angle that can be the same as the angle of offset θ of the bottom surface 402b of the body 502 relative to the plane of the mouth of the horn 109. And the second set of wedges 508b has a combined angle that can be the same as the angle of offset θ of the top surface 402a of the body 502 relative to the plane of the mouth of the horn 109. Thus, the bottom wedge surface of the bottom-most wedge of the lower set of wedges 508b is substantially parallel to the plane of the horn mouth and the top wedge surface of the top-most wedge of the upper set of wedges 508a. Thus, the acute angles of the upper set of wedges 508a are aligned at one side of the body 502 (i.e., the left side in the embodiment of FIG. 5(b)), while the acute angles of the lower set of wedges 508b are aligned at the opposite side of the body 502 (i.e., the right side). In this configuration, the signal emerges substantially parallel to and offset from the original signal axis 506, which can also be parallel to the central horn longitudinal axis.

[0042] In one embodiment, the dielectric constants of the plurality of dielectric layers ε1, ε2, ε3, ε4, and ε5 of each wedge 508 are sequentially higher the further away from the central plate 502, with ε1 being the lowest and ε5 being the highest. That is, the central plate 502 has the highest dielectric constant, and each wedge 508 adjacent to the central plate 502 has a sequentially lower dielectric constant. This design allows for increased transmission efficiency with an increasing number of layers and smaller field incidence angles for each layer, but has little effect on minimizing the size and mass of the design. Thus, each wedge 508 refracts the signal. And each wedge 508 in the bottom set of wedges 508b incrementally increases the angle of the signal relative to the original axis 506. And each wedge 508 in the top set of wedges 508a decreases the angle of the signal relative to the original axis 506 until the signal is substantially parallel to or at a desired angle relative to the original axis 506. An anti-reflective coating 403 can be placed at the top of the top wedges 506a and at the bottom of the bottom wedges 506b.

[0043] Turning to FIG. 5(c), prism 401c is shown with metamaterial and metasurface technology, which can also include a launch array concept. This implementation reduces the mass of prism 401c by reducing the volume of material needed, but correspondingly reduces the operational bandwidth and increases the insertion loss. Unlike the use of bulk dielectrics that define their properties by permittivity and shape, metasurface prisms have one or more layers of metamaterial or metasurface suspended in air by a support structure.

[0044] For this implementation, prism 401c can be constructed from two layers 531, 535 of spatially varying metamaterial or metasurface that changes the direction of the field from horn 109 at two points by introducing a phase gradient in the field of the launch. Metamaterial or metasurface prisms do not rely on refraction within a dielectric region like conventional prisms, and do not include the dielectric regions included in 401a and 401b. Thus, bottom metamaterial or metasurface 531 refracts the signal away from the original signal axis 506 so that the signal travels at an angle relative to the original signal axis 506. And top metamaterial or metasurface 535 refracts the signal back to be parallel with the original signal axis 506. The birefringence causes the signal to be offset from the original signal axis 506 and parallel with the original signal axis 506.

[0045] A gap or spacing between the two layers 531, 535 is needed to allow for the distance for field propagation and to create the lateral offset. The greater the spacing, the greater the lateral offset. The spacing is held by a mechanical structure 533 inside the prism structure that holds the space between layers 531, 535 as an air gap. For example, mechanical structure 533 can be a support or beam, and one or both of layers 531, 535 can be connected to the support at different locations that hold the desired air gap distance between them. This support structure inside the prism is separate in purpose and implementation from structure 407 that holds prism 401 to feed 109, and can be implemented using supports, bolts, clips, or other physical features to hold a fixed spacing between the two layers 531 and 535. The artificial dielectric or metasurface structure that forms layers 531 and 535 requires a periodic change to its structure on the surface of each layer 531 and 535 to establish a phase gradient on the surface and thus manipulate the beam, which limits the available bandwidth of the design. Metamaterial and metasurface designs are generally narrowband and lossy, but can be sufficient for certain applications. The transmission efficiency through the two layers is a key metric for this implementation.

[0046] In Figure 5 (d), a corrugated prism 401d is shown that reduces the thickness of the structure. This in turn reduces the weight, as the support structure 407 and radome 405 can also be smaller. The large height of the prisms shown in 401a and 401b is also reduced by introducing shaped corrugations in the top and bottom surfaces of the prism 401d. The corrugations have a sawtooth shape. Starting from the left, each tooth of the top surface has a straight leading upleg that is substantially parallel to the longitudinal axis of the horn, followed by an angled trailing downleg.

[0047] The prism 401d shows a collapsed version of the prism 401a, but the same approach can be applied to the multi-layer 401b. By collapsing the size and shape of the prism using Fresnel-style corrugations in the top and bottom surfaces 401d, the approximately same beam steering characteristics can be maintained, but the height of the prism is reduced. This will create a dispersion effect that limits the operational bandwidth, but can have less dispersion than the metasurface / metamaterial approach. An anti-reflective coating can be applied to the top and bottom corrugated surfaces of 401d and will follow the shape of the corrugations themselves. The bottom surface refracts the signal to form an angle relative to the original signal axis 506, while the top surface refracts the signal back to be parallel to (and offset from) the original signal axis 506.

[0048] In Figure 5 (e), a graded-index or inhomogeneous prism 401e with full control over the internal permittivity (x, y, z) provides significant benefits in collapsing the functionality into the smallest possible continuous package. The challenge of both the smooth variation (continuous) and the stepped gradient designs is the manufacture of the often complex shapes and structures required to achieve the necessary performance.

[0049] Referring to Figure 5(f), two half-prisms 401f are shown. Since the mass of the prism 401 is a major factor in the design of the redirection device 201, other measures can be taken to reduce the mass of the prism, including prisms in which the area of the dielectric in the interior of the prism is removed when not needed, effectively forming two half-prisms 401f separated from each other by a distance or air gap. In some implementations, the gap can be implemented, a hollow air region can be constructed within an otherwise solid prism, reducing weight but not requiring a separate mounting or support structure like the support 533. The half-prisms 401f can have a triangular shape, with planar or curved surfaces. As shown, the upper half-prism can have an inwardly facing surface curved to be slightly concave, while the lower half-prism can have an inwardly facing surface curved to be slightly convex. The inwardly facing surface of the upper half-prism faces the inwardly facing surface of the lower half-prism and has a shape that matches the inwardly facing surface of the lower half-prism. Matching the profile of the interior surface of the prism to the propagation direction of the field at each angle allows the field to continue straight without refraction at the interface, as if the removed material were still there. This mass reduction method is also useful when the loss tangent of the available dielectric is high compared to air. The bottom surface of the lower half-prism 401f is at an angle θ to the plane of the horn mouth and refracts the signal at an angle to the original signal axis 506. The top surface of the lower half-prism 401f further refracts the signal. The bottom surface of the upper half-prism 401f refracts the signal back to be parallel to the original signal axis 506, and the upper surface of the upper half-prism 401f further refracts the signal to be parallel to and offset from the original signal axis 506. The greater the distance between the upper and lower half-prisms 401f, the greater the achievable lateral offset of the signal from the original signal axis 506.

[0050] Because the fields propagating through the dielectric region do not spread as much as they would if they were propagating through air only, the effective phase center of the field from the device 201 can no longer match the reflector. Even if the lateral position can be correct, the distance of the phase center of the feed distribution to the reflector needs to match the focal length of the reflector to maintain aperture efficiency. Including a non-zero optical gain (through curvature of the surface or internal dielectric gradient) can be used to correct the angular distribution of the field as well as the effective phase center.

[0051] The required size of the prism 401 is determined jointly by the required degree of lateral displacement of the field and the geometry of the reflector. A good prism should be small, lightweight, compact, to minimize cost and simplify installation. However, the size of the prism 401 must be set to intercept all the power from the feed horn and redirect all the energy to the reflector.

[0052] Reference Figure 6For reflectors with a small f / D (focal length 603 to diameter 605) ratio or equivalently a wide illumination cone angle 609, the specific prism 611 implementation of thickness must be large enough in the lateral direction to cover the original radiation pattern cone 631 from the horn at the base of the prism, large enough at the exit of the prism 611 to release energy over the entire surface of the re-centered cone 633, and allow sufficient internal thickness 615 and width 613 to reshape the energy sufficiently to follow the desired path 607. If a thicker 625 prism 621 implementation is required to provide the necessary lateral displacement (generally, further displacement requires a thicker prism to provide more space to propagate), then the prism must also be wider 623 (at least at the output) so that the volume and mass of the prism (generally, approximately) is proportional to the cube of the prism thickness. This leads to the necessary requirement of minimizing the prism thickness while achieving other performance parameters in order to also control the mass.

[0053] The f / D ratio also affects the amount of lateral displacement required to steer the reflector to a given angle. As with many common consumer DTH antennas, a reflector with a low f / D ratio allows for small changes in the effective feed location 109 to produce large shifts in the beam scan angle.

[0054] A reflector with a high f / D would require a smaller prism to displace the aperture field a given distance because the cone angle is small, but would require a larger physical displacement to achieve the same scan angle of the main beam in degrees.

[0055] In one embodiment, the reflector re-pointing device 201 is retrofitted to (and connected to, such as by a fastener mechanism, adhesive, etc.) an existing horn antenna. Thus, it is configured to work with the existing horn antenna and parabolic reflector. The characteristics of the prism 401 are designed to fit the antenna system 101. However, in other embodiments, the horn antenna and parabolic reflector can be designed to work with the device 201, which would involve mounting features 407 ready to easily and precisely mount the device 201, sturdy mounting arms 107 (Figure 1) to support the additional weight of the device 201 without deflection, and an f / D ratio large enough to optimize the mass of the entire system 201.

[0056] For a given pair of satellites, the incumbent satellite 213 and the new target satellite 215 (Figure 2), the correction angle that must be applied by the reflector re-pointing device 201 and the direction in which the offset from the current antenna pointing direction should be applied is based on the angular distance between the two satellites and the location on Earth where the satellites are observed.

[0057] Figure 7The different angles that must be applied on the ground are shown. Since the relatively small diameter reflector 103 used for DTH (typically between 40 and 80 cm) has a fairly wide beam, the resolution of the correction is very coarse. Based on the target installation location of the reflector re-pointing device 201, a chart similar to Figure 7 is consulted and the necessary correction angles and directions are selected. The correction angles and directions are then applied by implementation in the individual prism and mounting design of each combination or by adjustable clamps or mounting arrangements, using a single prism and clamp design for a wider geographic area to appropriately set the scan angle and direction. The prism effectively rotates the correction angle around the central axis of the horn antenna 109 so as to point the resulting beam at the target satellite based on the location of the system 200. The prism or setting selection can be made prior to shipping the device to the end user or the end user can be provided instructions to use a particular numbered or labeled setting depending on their location, i.e. the instructions might read "for your zip code ABC, before mounting on your antenna, rotate the mounting clamp to align the arrow with location D".

[0058] These instructions would apply to the implementation shown in Figures 8(a) and 8(b). The horn antenna 109 is shown mounted with its center at point 811. The prism 401 (shown for illustrative purposes only, but contained within the radome 405 of the device 201) shifts the field of the horn to re-center to point 813 as it exits the prism. A set of detents and alignment markings are provided on the housing or radome material so as to be adjustably aligned by the end user or prior to shipping. The alignment markings allow the user to adjust the mounting structure to set the adjustable position and adjustable orientation of the microwave prism relative to the reflector antenna, specifically relative to the horn feed 109. That is, the mounting structure 407 fixedly attaches the device 201 to the antenna 101, but at a position and orientation defined by the adjustable alignment markings. The alignment features define multiple positions and orientations of the microwave prism relative to the mounting structure, and can be set at the factory based on geographic location. The end user can then determine the appropriate setting based on the geographic location of the installation location, such as by using a Figure 7

[0059] ​Changing the orientation of the prism 401 relative to the central axis of the feed horn 109 changes the angle of the redirected beam relative to the originally installed antenna. For example, the prism can be rotated about the central axis of the feed horn 109 so that the resulting beam is pointed east or west of the original beam direction, as well as adjusting the elevation angle of the beam pointing above the horizon to accurately point to the desired satellite 215. One or more support or fastening members can be provided to move the prism 401. For example, the fastening members can movably connect the prism 401 to the radome 405 or mounting structure 407 so that the prism 401 can change its orientation relative to the feed horn 109.

[0060] Figure 8(c) shows the apparatus 401 aligned with position A, while Figure 8(a) shows the apparatus 401 aligned with position E. Here, note that the signal emerging from the horn is offset by the prism, as shown in Figures 5(a) through 5(f). The alignment member 817 can be connected to the prism 401 so that rotating the alignment member 817 between the various positions also rotates the entire prism 401. When the prism and alignment member 817 are in position E (Figure 8(a)), the phase center 813 of the prism is offset from the phase center 811 of the horn. More specifically, the phase center 813 of the prism is located approximately in the 2 o'clock direction relative to the phase center 811 of the horn. When the prism and alignment member 817 are in position A (Figure 8(c)), the phase center 813 of the prism is in approximately the 4 o'clock direction relative to the phase center 811 of the horn. Thus, the phase center 813 of the prism rotates with the rotation of the alignment, which in turn moves the signal output by the prism. In another embodiment, different positions of the alignment can produce different angles for the prism.

[0061] The prism 401 can take any shape or different orientation relative to the feed horn, as previously described in Figures 4 to 6 The shape and boundaries of the radome are then selected to properly cover the prism.

[0062] After the alignment adjustable alignment member 817, the apparatus is fixedly connected to the horn in any suitable manner. For example, the mounting system 407 can include a snap connector 819 that snaps onto a mounting pole of the antenna, stabilized and oriented by the horn shroud 815. Once installed, the apparatus will now cause the reflector to point its main beam to the new desired satellite 215. The mounting features 407 fixedly hold the apparatus in place to intercept all of the field from the horn 109, which would otherwise reach the reflector 103 and cause the field to be displaced laterally to cause a change in the scan angle of the reflector antenna 101. No further motion or activity is required during proper operation of the antenna 101 and apparatus 201. If it is desired for the antenna to again be redirected to the original incumbent satellite 213, the apparatus 201 can be removed by disassembling the mounting features 819.

[0063] Note that the drawings can illustrate, and the description and claims can use, geometrical or relational terms such as right, left, above, below, up, down, lateral, top, bottom, elongated, parallel, sideways, orthogonal, angled, rectangular, square, annular, circular, axis. These terms are not intended to limit the present disclosure and are generally used to facilitate the description based on the examples shown in the drawings. Moreover, the geometrical or relational terms can not be exact. For example, signals and planes can not be perfectly perpendicular or parallel to each other but can still be considered perpendicular or parallel.

[0064] The foregoing description and accompanying drawings are to be regarded as illustrating just a few of the principles of the present disclosure. The system can be configured in a variety of shapes and sizes and is not intended to be limited by the embodiments. Those of skill in the art will readily appreciate many applications of the principles of the present disclosure. It is contemplated that the present disclosure can be carried out in a variety of ways and that the disclosed examples are only representative of the many applications of the principles of the present disclosure. Accordingly, it is not intended to be limited to the specific examples disclosed or the specific constructions and operations described and shown. Rather, any suitable modification and equivalents should be considered as falling within the scope of the present disclosure.

Claims

1. A reflector antenna repointing device (201) for use with a reflector antenna (200), the reflector antenna (200) comprising a reflector (103) having a reflector axis and a feed horn (109), the reflector antenna repointing device comprising: A microwave prism (401) is configured to receive an input field and provide an output field; Mounting structure (407) configured to connect the microwave prism to the reflector antenna (200) and mount the microwave prism above the feed horn (109); as well as The alignment feature at the mounting structure is configured to set the position and orientation of the microwave prism (401) relative to the reflector antenna (200), wherein the alignment feature defines a lateral displacement of the output field relative to the input field perpendicular to the reflector axis; The reflector antenna repointing device is configured to repoint the input field from the old satellite (213) to the new target satellite (215) without manual fine-tuning.

2. The reflector antenna re-pointing device according to claim 1, wherein, The mounting structure is configured to connect the microwave prism (401) to the mounting arm (107) of the reflector antenna.

3. The reflector antenna repointing device according to claim 1 or claim 2, wherein the microwave prism (401) comprises a parallel plate prism (401a).

4. The reflector antenna repointing device according to claim 3, wherein the parallel plate prism (401a) has a plurality of wedges (508) added to the input and output surfaces of the microwave prism to reduce the incident angle and improve transmission through the reflector antenna repointing device.

5. The reflector antenna repointing device according to claim 1 or claim 2, wherein the microwave prism (401) comprises two (531, 535) or more spatially graded metasurfaces or metamaterials.

6. The reflector antenna repointing device according to claim 1 or 2, wherein the microwave prism has a Fresnel grating.

7. The reflector antenna repointing device according to claim 1 or 2, wherein the microwave prism (401) has a continuous or stepped gradient refractive index structure.

8. The reflector antenna repointing device according to claim 1 or 2, wherein the microwave prism (401) has an upper half-prism and a lower half-prism, wherein, The inner boundaries of the upper and lower prisms are cut to ensure that the input field is incident on the normal at all points on the respective inner boundaries.

9. The reflector antenna repointing device according to claim 1 or 2 further includes an antenna radome (405) enclosing the microwave prism.

10. The reflector antenna repointing device according to claim 1 or 2, wherein, The mounting structure is configured to clamp or snap onto the reflector antenna (200).

11. The reflector antenna repointing device according to claim 1 or 2, wherein, The mounting structure (407) and the microwave prism (401) are customized for specific reflector antenna variants and old-new satellite combinations.

12. The reflector antenna repointing device according to claim 1 or 2, wherein, The alignment feature is adjustable and defines multiple positions and orientations of the microwave prism (401) relative to the mounting structure, and the multiple positions are set at the factory based on geographical location.

13. The reflector antenna repointing device according to claim 12, wherein, The orientation is set by the end user based on geographical location.

14. A reflector antenna (200), comprising: A feed horn (109) is configured to provide an antenna field; as well as The reflector antenna repointing device (201) according to any one of claims 1 to 13; The mounting structure (407) is configured to position the microwave prism (401) relative to the feed horn (109); and The reflector antenna repointing device includes an adjustable alignment feature that defines a plurality of adjustable positions of the microwave prism (401) relative to the feed horn (109), wherein each of the plurality of adjustable positions defines a corresponding shift of the output field relative to the antenna field.

15. The reflector antenna according to claim 14, wherein, The microwave prism (401) is configured to redirect the antenna field from the old satellite (213) to the new target satellite (215) without manual fine-tuning.

16. The reflector antenna according to claim 14 or claim 15, further comprising an antenna cover (405) enclosing the microwave prism (401).

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