Patent Grant
10468773
The present invention relates generally to antennas and feeds for dish antennas. In particular, this invention relates to ring focus dish antennas for use in communications systems. Still more particularly, this invention relates to an integrated antenna feed and a turnstile circular polarizer for use with a ring focus dish antenna.
High gain antennas, used in applications such as satellite communications (SATCOM), or long range line-of-sight (LOS) communications links, require large aperture areas to achieve sufficiently high gains. Two primary methods by which these large aperture areas can be achieved are through an array of small elements (array antenna) or through directing the RF energy to an antenna feed using a large area dish and a subreflector. The reflector may also focus directly to an antenna feed (primary feed reflector) instead of using a subreflector. The reflector can be fabricated in a plurality of ways to achieve the optics desired. Additionally, a large lens can be used to focus energy to an antenna feed.
In parabolic antennas such as satellite dishes, an antenna feed horn (or feedhorn) is a small horn antenna used to direct radio waves between a feedhorn, a subreflector, and a parabolic main reflector dish. The antenna can be transmit only, receive only (half duplex), or it can have both transmit and receive functionality, simultaneously (full duplex). In transmit mode, the feed horn is connected to the transmitter and converts the radio frequency energy from the transmitter to radio waves and feeds them to the rest of the antenna, which focuses them into a beam. In receiving mode, incoming radio waves are gathered and focused by the antenna's main reflector onto the feed horn, which converts the incoming radio waves into detectable radio frequency energy which may be amplified and further processed by the receiver. Transmission mode and receiving mode can occur simultaneously from the same antenna either through frequency division or through time division duplexing. Alternatively, transmission and receiving modes can occur individually.
Ideally, the aperture between the feed horn and subreflector of a ring focus reflector-type antenna is entirely unobstructed. However, in conventional reflector-type antennas, some form of mechanical structure is generally required to support the subreflector relative to the feed horn. However, such support structure, e.g., one or more struts, dielectric, etc., unavoidably shadows, attenuates, or blocks, a portion of the aperture between the feed horn and the subreflector and consequently degrades the performance of the antenna.
Another problem with a conventional antenna feed is that each of the components, e.g., input section, polarizer, feed horn and subreflector, is generally constructed as a separate component. The assembly, testing and fine tuning of such separately manufactured antenna feeds results in significant labor and manufacturing cost, long fabrication and test times, and potential for high variability of antenna performance between units.
Antennas located in space on a satellite are limited in material choices, and most dielectrics are not fit for space applications. Similarly, the use of struts degrades performance and increases the stowed size of the antenna, making it more difficult and expensive to launch.
Accordingly, there exists a need in the art for a high-gain antenna feed that alleviates at least some of these problems with conventional antenna feeds used with ring focus dish reflector-type antenna systems. For example, an antenna feed without dielectric or strut supports would be particularly useful in the SATCOM context.
An embodiment of an integrated antenna feed having an axis with proximal and distal ends for propagating an electromagnetic wave is disclosed. The antenna feed may include a circular waveguide input having a circular opening at the proximal end and extending coaxially toward the distal end. The antenna feed may further include a circular waveguide to wrapped-single-ridged waveguide transition coupled to the circular waveguide input and extending further along the axis toward the distal end and flaring radially outward relative to the axis into four waveguide branches. The antenna feed may further include a polarizer coupled to the four branches of the circular waveguide to wrapped-single-ridged waveguide transition, wherein each of the four branches forms a wrapped-single-ridged waveguide extending from the circular waveguide to wrapped-single-ridged waveguide transition and parallel to the axis further toward the distal end. The antenna feed may further include a wrapped-single-ridged waveguide to coaxial waveguide transition coupled to the polarizer and each of the four branches transitioning into a single coaxial waveguide. The antenna feed may further include a coaxial feed horn coupled to the single coaxial waveguide of the wrapped-single-ridged to coaxial waveguide transition, the single coaxial waveguide disposed between an inner cylindrical support having a smaller diameter and a feed horn bell having a larger and variably increasing diameter opening to free space, the inner cylindrical support extending coaxially from the feed horn still further toward the distal end. The antenna feed may further include a subreflector located at the distal end and supported by the inner cylindrical support.
An embodiment of a turnstile polarizer disposed between a circular waveguide input and coaxial feed horn is disclosed. The polarizer may include two wrapped-single-ridged positive phase-shift waveguides, each positive phase-shift waveguide having first and second ends. The polarizer may further include two wrapped-single-ridged negative phase-shift waveguides having third and fourth ends. The polarizer may further include a first transition in communication with the circular waveguide input and the first ends of the two wrapped-single-ridged positive phase-shift waveguides, the first transition also in communication with the third ends of the two wrapped-single-ridged negative phase-shift waveguides. The polarizer may further include a second transition in communication with the coaxial feed horn and the second ends of the two wrapped-single-ridged positive phase-shift waveguides, the second transition also in communication with the fourth ends of the two wrapped-single-ridged negative phase-shift waveguides.
A first alternative embodiment of an integrated single-piece antenna feed having an axis with proximal and distal ends for propagating an electromagnetic wave is disclosed. The embodiment of an antenna feed may include four ridged rectangular waveguide arms for propagating the electromagnetic wave from the proximal end and extending toward the distal end. The embodiment of an antenna feed may further include a coaxial turnstile waveguide including an outside surface cylindrical conductor and an inner conductor, the inner conductor having a cylindrical subreflector support. The embodiment of an antenna feed may further include a ridged rectangular waveguide to coaxial turnstile waveguide transition coupled to the four ridged rectangular waveguide arms. According to this embodiment, each of the four ridged rectangular waveguide arms transitions into the coaxial turnstile waveguide. The embodiment of an antenna feed may further include a coaxial feed horn coupled to the coaxial turnstile waveguide. The embodiment of an antenna feed may further include a subreflector located at the distal end having an outer rim and supported axially by the cylindrical subreflector support.
A second alternative embodiment of an integrated single-piece antenna feed having an axis with proximal and distal ends for propagating an electromagnetic wave is disclosed. The embodiment of an antenna feed may include a circular waveguide input having a circular opening at the proximal end and extending coaxially toward the distal end. The embodiment of an antenna feed may further include a coaxial feed horn coupled to the circular waveguide. The embodiment of an antenna feed may further include a subreflector located at the distal end having an outer rim. The embodiment of an antenna feed may further include a coaxial post extending axially from the subreflector toward the proximal end and into the circular waveguide input. The embodiment of an antenna feed may further include a plurality of symmetrically oriented struts configured for structurally supporting the subreflector. According to this embodiment, each of the plurality of struts may be connected between the outer rim of the subreflector and the circular waveguide input.
A third alternative embodiment of an integrated single-piece antenna feed having an axis with proximal and distal ends for propagating an electromagnetic wave is disclosed. The embodiment of an antenna feed may include a circular waveguide input having a circular opening at the proximal end and extending coaxially toward the distal end. The embodiment of an antenna feed may further include a feed horn coupled to the circular waveguide. The embodiment of an antenna feed may further include a subreflector located at the distal end having an outer rim. The embodiment of an antenna feed may further include a plurality of symmetrically oriented struts configured for structurally supporting the subreflector. According to this embodiment, each of the plurality of struts may be connected between the outer rim of the subreflector and the circular waveguide input.
A fourth alternative embodiment of an integrated single-piece antenna feed having an axis with proximal and distal ends for propagating an electromagnetic wave is disclosed. The embodiment of an antenna feed may include a wrapped-ridged rectangular waveguide for propagating the electromagnetic wave from the proximal end and extending toward the distal end. The embodiment of an antenna feed may further include a circular waveguide including an outside surface cylindrical conductor and an inner conductor, the inner conductor comprising a cylindrical subreflector support. The embodiment of an antenna feed may further include a wrapped-ridged rectangular waveguide to circular waveguide transition coupled to the wrapped-ridged rectangular waveguide. The embodiment of an antenna feed may further include a feed horn coupled to the wrapped-ridged rectangular waveguide to circular waveguide transition. According to this embodiment, the feed horn may have a circular waveguide input that flares radially outward to form a frusto-conical inner profile. The embodiment of an antenna feed may further include a subreflector located at the distal end having an upper surface. The embodiment of an antenna feed may further include a plurality of struts. According to this embodiment, each of the plurality of struts may be connected to the upper surface of the subreflector and the wrapped-ridged rectangular waveguide.
Additional features and advantages of the invention will be apparent from the detailed description which follows, taken in conjunction with the accompanying drawings, which together illustrate, by way of example, features of embodiments of the present invention.
The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.
The following drawings illustrate exemplary embodiments for carrying out the invention. Like reference numerals refer to like parts in different views or embodiments of the present invention in the drawings.
Embodiments of the present invention include an integrated single-piece antenna feed for use in communications systems such as SATCOM, or long range LOS communications links. The feed may include circular waveguide input, polarizer, coaxial feed horn with subreflector support, and subreflector as a single-piece metal component. This antenna feed may be used in conjunction with a parabolic ring-focus main reflector in a dish antenna system. A particularly useful feature of embodiments of the antenna feed is that the antenna feed is formed of an integrated “single-piece” and is not assembled from its individual components. Integrated embodiments and individual components of the invention described herein may be manufactured using three-dimensional (3D) metal printing, (also known in the industry as direct metal printing (DMP), or additive manufacturing) techniques known to one of ordinary skill in the art.
According to one embodiment, all components of various embodiments of the antenna feed and are printed as an integrated single piece of metal, e.g., aluminum. This integrated manufacturing eliminates a large number of component parts, multiple assembly steps as well as tuning steps during test.
Embodiments of the integrated single-piece antenna feed may support full duplex, i.e., both transmitting (Tx) and receiving (Rx), half duplex, Tx only, or Rx only. Accordingly, the embodiments of an antenna feed disclosed herein do not define transmit or receive functionality, as they are reciprocal and equal at that stage of an antenna system for a given frequency. The determination which Tx/Rx scheme to use for a given antenna systems happens further down the RF chain at the filtering and RF electronics stage (to determine whether duplexing happens in frequency or time, if at all).
One embodiment of the integrated antenna feed disclosed herein may be designed to work at X-band SATCOM frequencies. According to another embodiment, the integrated antenna feed can be scaled to work from low X-band (7 GHz) through E-band (90 GHz).
A parabolic ring-focus reflector follows the parabolic equation:
where the ring offset in the parabola, a, allows for a ring-focus, and the focal length of the antenna, F, is distance from apex of the main reflector to the focal ring.
From a waveguide perspective, integrated antenna feed 200 includes a circular waveguide input 240 having a circular opening 242 at a proximal end 280. The circular waveguide input 240 leads to a circular waveguide to wrapped-single-ridged waveguide transition 260. The circular waveguide to wrapped-single-ridged waveguide transition 260 is disposed between the circular waveguide input 240 and polarizer 230. The polarizer 230 is comprised of a plurality of wrapped-single-ridged waveguide branches as discussed in more detail below. Between the coaxial feed horn 220 and the polarizer is a wrapped-single-ridged waveguide to coaxial waveguide transition 270. The coaxial feed horn 220 includes a center conductor that is also a subreflector support 250 that physically supports the subreflector 210 at the distal end of antenna feed 200.
Ideally, there is free space between the subreflector and feed horn in a ring-focus reflector antenna. Fabricating the subreflector and feed horn as separate components allows the subreflector and feed horn to be physically separated in such a way the RF energy can properly radiate from the feed horn and bounce off the subreflector. A subreflector support is generally necessary: (1) to position the subreflector at the correct location with respect to the feed horn and the main reflector and (2) to physically support the subreflector in that desired location under a variety of shock and vibration conditions.
However, externally mounted electrically conductive supports (not shown) cause blockage to the main radio frequency (RF) path between the subreflector and feed horn, causing significant degradation of antenna performance. Such conventional subreflector supports (not shown) may include struts, dielectric supports, and other methods that use individual or multiple support structures to hold the subreflector in place. All of these conventional subreflector supports tend to degrade antenna system performance. Another drawback with conventional antenna systems is that using separately fabricated components that are assembled together requires precision assembly followed by tuning of the antenna after fabrication to ensure proper positioning of the subreflector. Yet another design consideration is that extra weight may be added to the antenna feed design by the subreflector support, which is undesirable in some antenna applications.
A particularly useful feature of the present invention is that it solves the problem of subreflector support and multi-piece construction by employing a subreflector support 250 extending from the center conductor of the coaxial feed horn 220 to physically support the subreflector 210 with a turnstile polarizer 230. One embodiment of the invention is an integrated antenna feed 200, 400 for use with a main reflector dish 102 in an antenna system 100. The integrated antenna feed 200, 400 may include a subreflector 210 at a distal end 290, supported by a subreflector support 250 extending from a coaxial feed horn 220, a coaxial-to-circular turnstile polarizer 230, and circular waveguide input 240, 440 having a circular opening 242, 442 located at a proximal end 280 of the antenna feed 200, 400. Embodiments of an antenna feed 200, 400 may be fabricated as an integrated metal construct, for example by using three dimensional (3D) metal printing techniques. By using 3D metal printing techniques, separate mounting hardware and related tuning of individual components are both eliminated because the components share structural walls at their interfaces. Additional support structure may be added to strengthen the antenna feed, according to other embodiments. At least one embodiment of an integrated antenna feed may be used in conjunction with a main reflector that has a ring focus, see e.g., 100,
According to one embodiment, the subreflector may be an optimized surface that is radially symmetric about the main axis (see 300,
One embodiment of an antenna waveguide polarizer may be used to synthesize circular polarization by converting a single-mode input from the circular waveguide input 240 into two orthogonal degenerate primary coaxial waveguide transverse electric (TE) modes and phase-shift them 90° with respect to one another. By doing this, both right-hand circular polarization (RHCP) and left-hand circular polarization (LHCP) can be achieved by phase-shifting one mode by positive or negative 90° with respect to the other. Various embodiments of waveguide circular polarizers are contemplated to be within the scope of the present invention, including; septums, dielectric wedges, corrugated waveguide, and other approaches known to those of ordinary skill in the art.
More particularly, embodiments of the antenna feed 200 and 400 disclosed herein employ TE11 mode in the circular waveguide input 240 and TE11 in the coaxial feed horn 220. Both TE11 modes (circular waveguide and coaxial waveguide), have “degenerate modes”, which simply means you can orient the field in more than one orientation in the waveguide and the modes will have the same cutoff frequency, impedance characteristics, and TE numbering designation, but they are orthogonal. For the TE11 mode (circular waveguide and coaxial waveguide) there are two degenerate orthogonal modes.
According to another embodiment, the feed horn may be a coaxial feed horn that transitions to a coaxial turnstile polarizer with four branches of wrapped-single-ridged waveguide. The four branches of wrapped-single-ridged waveguide act as a polarizer to convert a linearly polarized input to a circularly polarized output when transmitting and vice versa when receiving. The four branches of wrapped-single-ridged waveguide may include two pairs of wrapped-single-ridged waveguides, one pair with a +45° phase-shift and one pair with a −45° phase-shift, according to a particular embodiment of the invention.
More particularly, the net 90° phase shift is achieved by matching the slopes of the positive and negative phase shift branches 730P and 730N, where the +45° and −45° happens at only one part of the band, but there is an effectively linear phase relation with frequency. So, the term “+45° phase shift” as used herein is actually +45° at one point or frequency in the frequency band of operation. Likewise the term “−45° phase shift”, similarly, is at one point in the frequency band of operation. The positive phase shift arms 730P have a linear phase-shift relationship over frequency band with some slope ‘+m’. The negative phase shift arms 730N have a linear phase-shift relationship over frequency with a slope of approximately ‘−m’. This leads to an effective phase shift of 90° between the branches 730P and 730N over a wide bandwidth, since the +m slope is cancelled out by the −m slope to achieve a flat phase-shift response over the frequency band.
The +45° phase-shift waveguide branches 730P are opposite one another, and rotated physically 90° about the main axis 300 with respect to the −45° phase-shift waveguide branches 730N. The four waveguide branches (2 pairs of phase-shifting waveguide, 730P and 730N) recombine at a circular waveguide to wrapped-single-ridged waveguide transition 260, according to this particular embodiment.
According to one embodiment, the entire feed may be physically rotated 45° about the center of the coax such that the pairs of phase-shifting waveguide are aligned with the +/−45° axes of the reflector. When fed with a linear Horizontal (H) or Vertical (V) polarized signal (oriented at 0° or 90° with respect to the rotation axis of the reflector) a circular polarization (CP) is achieved, with an input of H being converted into an output of either right hand circular polarization (RHCP) or left hand circular polarization (LHCP) and an input of V being converted into an output of the orthogonal polarization (LHCP or RHCP), depending on the orientation of the positive and negative 45° phase-shift waveguide pair.
The positive and negative 45° phase-shift in the pairs of waveguide branches may be achieved through the use of ridges in either the ceiling/floor (negative phase-shift) or the wall/wall (positive phase-shift) of the waveguide channels. This embodiment replaces use of a conventional polarizer and provides a broad bandwidth overall 90° phase-shift between the branches and synthesizes circular polarization at the coaxial feed horn. According to one embodiment, the waveguide branches are wrapped-single-ridged waveguide, with a single ridge along one wall of the waveguide. This reduces the total width of the waveguide and allows for support structures between the positive and negative 45° phase-shift waveguide pairs.
According to one embodiment, the circular waveguide input allows for an interface that can accept either a V or H linearly polarized signal. To change the polarization received at the input, one simply physically rotates the feed 90°, which changes the RF path through the phase-shifting waveguide branches in a manner that switches the polarization from RHCP to LHCP or LHCP to RHCP.
Referring again to
There are several higher order modes operating within transition 260. But, the key feature of transition 260 is that it converts the TE11 mode from the circular waveguide input 240 into the TE10 mode (the fundamental mode) in wrapped-single ridged waveguides, which are employed in the polarizer 230 (see
In a rectangular or standard ridged waveguide there is only the single fundamental TE10 mode propagating from input 240 to feed horn 220. There are a number of higher order modes appearing in the phase-shifting section of the polarizer 230, but they do not propagate down the waveguide, rather, they couple in an evanescent manner and change the shape of the propagating wave.
At transition 270 there are also a number of higher order modes coupling in an evanescent manner that change the shape of the propagating wave to allow the transition to occur before reaching the feed horn 220. In the coaxial section of the feed horn 220, more particularly right at the throat of the feed horn 220, the mode that is supported is TE11, which is not the fundamental TEM mode for a coaxial waveguide. The fundamental TEM mode is not supported, due to the symmetry imposed by how the feed horn 220 is fed.
The coaxial feed horn 220 shown herein supports a coaxial TE11 mode. In the TE11 mode, the electric field lines are primarily aligned in the same direction, which is optimal for radiation from the coaxial feed horn 220. The coaxial feed horn 220 acts as a transition between the polarizer 230 on the interior of the antenna feed 200, 400, and the free space to the subreflector 210 on the exterior of the antenna feed 200, 400. The four wrapped-single-ridged waveguide branches 730P and 730N (
For this particular embodiment of a negative phase-shift waveguide cavity 630N, there are two shallow rib pairs 650, two medium depth rib pairs 652 and four deep rib pairs 654. The four deep rib pairs 654 are in the central portion of the waveguide 630N and are surrounded by the medium depth rib pairs 652 which in turn are surrounded by the shallow rib pairs 650. Stated another way, the negative phase-shift waveguide cavity 630N is symmetrical in that a wave propagating in either direction from first end to second end through the waveguide branch will be shaped identically. The negative phase-shift sections 630N are also symmetrically disposed about, and parallel to the axis 300 of the integrated antenna feed 200, 400.
The particular spacing and depth of the capacitive rib pairs 650, 652 and 654 determines the total phase-shift of the electromagnetic wave propagating through the negative phase-shift waveguide cavity 630N. The terms “waveguide cavity” and “air volume” are used synonymously herein. In the illustrated embodiment the phase-shift is −45° at a middle region of the band. The same phase-shift may be achieved with more or fewer ribs and depends on the total bandwidth desired for a 90° phase-shift, according to other embodiments of the present invention. In some embodiments of the invention, more rib pairs, e.g., twelve total capacitive rib pairs (not illustrated) on each opposed ceiling 632 and floor 634, may be used to achieve a greater bandwidth performance for a total 90° phase-shift between the positive 630P and negative 630N phase-shift arms. According to some embodiments of the negative phase-shift waveguide cavity 630N, a radius may be added to the internal corners of the individual ribs for improved manufacturability and performance. In the illustrated embodiments, the air volumes 630P and 630N are wrapped (curved around the axis on both floor and ceiling) to conform to an outer cylindrical diameter of the antenna feed 200, 400. The illustrated embodiments of negative phase-shift air volume 630N are also “ridged” in that there is a longitudinal ridge 636 bisecting the ceiling 632.
A wave propagating through the positive phase-shift waveguide branch 630P is bounded by floor 644 and ceiling 642 and opposed walls 648. The floor 644 runs parallel to axis 300 (see, e.g.,
For this particular embodiment of a positive phase-shift waveguide cavity 630P, there are two shallow rib pairs 660, two medium depth rib pairs 662 and four deep rib pairs 664. The four deep rib pairs 664 are in the central portion of the waveguide 730P (air volume 630P within 730P shown in
Again, the particular spacing and depth of the inductive rib pairs 660, 662 and 664 determines the total phase-shift of the wave through the positive phase-shift waveguide branch 630P. In the illustrated embodiment the phase-shift is +45° at a middle region of the band. Again, the same phase-shift may be achieved with more or fewer ribs, and depends on the total bandwidth desired for a 90° phase-shift, according to other embodiments of the present invention. In some versions of the invention, more rib pairs, e.g., twelve total ribs on each opposed side 638, may be used to achieve a greater bandwidth performance for a total 90° phase-shift between the positive phase-shift arms 630P. The longitudinal ridge 646 in the positive phase-shift waveguide branch 630P does not cross through the inductive rib pairs 660, 662 and 664 in the opposed walls 648. A radius may be added to the internal corners of the individual ribs for improved manufacturability and performance, according to other embodiments of the present invention. The positive phase-shift waveguide branch 630P illustrated in
An electromagnetic wave propagating through each of the negative phase shift branches 630N of the polarizer 230 is delayed using a set of capacitive irises formed by the series of capacitive rib pairs 650, 652 and 654 located on the ceiling 632 and floor 634. This electromagnetic wave delay (negative phase-shift) is coupled with the advance of the electromagnetic wave (positive phase-shift) in a positive phase-shift branches 630P using a series of inductive irises formed by the inductive rib pairs 660, 662 and 664 in order to achieve a net 90° phase shift that is broadband enough for the band of interest, e.g., X-band for SATCOM. There are suitable alternative configurations or embodiments of positive and negative phase-shift arms that are not wrapped and have a more rectangular geometry that may be used to achieve the same phase-shifting purpose as those illustrated in
Antenna polarization may be described as the orientation (both amplitude and phase components) of the E-field as it propagates through free space. This particular embodiment of a polarizer 230 synthesizes circular polarization, both right-hand (RHCP) and left-hand (LHCP). Circular polarization looks like a rotating wave that rotates with either right-hand or left-hand. These fields are orthogonal and will not interact with one another in free space. Circular polarization is achieved by adding the linear H and V components together with a 90° phase offset between them.
High Gain Antenna
The main reflector dish 102 focuses energy to its ring focus 104 (hidden by subreflector 210, but see, e.g.,
Main Parabolic Ring-Focus Reflector Dish to Subreflector
Subreflector to Coaxial Feed Horn
Polarizer and Circular Polarization
The embodiments of antenna feeds disclosed above generally employ a coaxial subreflector support. It will be understood there are other methods and structures for supporting a subreflector. Four alternative antenna feed embodiments will now be disclosed that employ additional methods and structure for subreflector support. As with the other embodiments disclosed above, these additional embodiments may all be fabricated as a single structure using additive metal fabrication, or metal 3D printing. Among these alternative antenna feed embodiments, some may include either a circular waveguide turnstile transition into the antenna horn, or feed horn can be directly fed by a circular waveguide.
Referring now to
The subreflector 1010 is axially supported by the coaxial post 1050. In addition to the coaxial post 1010, there are 4 struts 1052 that are located symmetrically about the outer rim 1012 of subreflector 1010 and the coaxial turnstile 1032, that also provide structural support to the subreflector 1010. The cross-sectional geometry of the struts 1052 shown is a trapezoidal cross-section, but they could alternatively be diamond, circular, square, or other geometries according to other embodiment not illustrated. Such alternative cross-sectional shapes are known to those of ordinary skill in the art and thus are not illustrated in the drawings. The trapezoidal shape of the struts 1052 shown in
Each of the struts 1152 may further be connected to the outside surface conductor 1134 of a circular waveguide input 1140.
The features of coaxial feed horn 1120 may be identical to the features of coaxial feed horn 1020 (
According to other embodiments (not illustrated), the tapered coaxial transition region 1170 could be replaced by other transitional features, for example and not by way of limitation, a series of alternating diameter regions, a spline profile region, or geometry changes to the outer circular/coaxial waveguide wall diameter. The embodiment of feed horn 1120 may include a frusto-conical inside profile 1124 with outer circumferential corrugations 1122. The 4 struts 1052 that are located symmetrically about the subreflector 1110 provide the only physical support to the subreflector 1110 and the coaxial post 1150. The particular geometry of the struts 1152 shown in
The third alternative embodiment of an antenna feed 1200 shown in
The particular geometry of the struts 1352 shown in
The embodiment of feed horn 1320 shown in
Having described the various embodiments of an integrated single-piece antenna feed and their various components in reference to the drawing FIGS., some general embodiments will now be disclosed. For example, an embodiment of an integrated single-piece antenna feed 200, 400 having an axis 300 with proximal 280 and distal 290 ends for propagating an electromagnetic wave is disclosed. The antenna feed 200 may include a circular waveguide input 240 having a circular opening 242 at the proximal end 280 that extends coaxially toward the distal end 290. The antenna feed 200 may further include a circular waveguide to wrapped-single-ridged waveguide transition 260 coupled to the circular waveguide input 240 extending further along the axis 300 toward the distal end 290 and flaring radially outward relative to the axis 300 into four waveguide branches. The antenna feed 200, 400 may further include a polarizer 230 coupled to the four branches of the circular waveguide to wrapped-single-ridged waveguide transition 260, wherein each of the four branches forms a wrapped-single-ridged waveguide 730P and 730N extending from the circular waveguide to wrapped-single-ridged waveguide transition 260 and parallel to the axis 300 further toward the distal end 290. The antenna feed 200 may further include a wrapped-single-ridged waveguide to coaxial waveguide transition 270 coupled to the polarizer 230 wherein each of the four branches 730P and 730N transitions into a single coaxial waveguide. The single coaxial waveguide may be located at the throat of the coaxial feed horn 220, according to one embodiment of the present invention. The antenna feed 200 may further include a coaxial feed horn 220 coupled to the single coaxial waveguide of the wrapped-single-ridged to coaxial waveguide transition 270, the single coaxial waveguide disposed between an inner conductor of the coaxial feed horn 220 that is also a cylindrical subreflector support 250 having a smaller diameter and an outer horn conductor 370, or feed horn bell, having a larger and variably increasing diameter opening to free space. The cylindrical subreflector support 250 extends coaxially from the coaxial feed horn 220 still further toward the distal end 290. The antenna feed 200, 400 may further include a subreflector 210 located at the distal end 290 and supported by the cylindrical subreflector support 250.
According to another embodiment of the integrated single-piece antenna feed 200, 400, the circular waveguide input may further include a flange 450 disposed around the circular opening 442 at the proximal end 280. The flange 450 may further include a plurality of mounting holes 460 suitable for mounting the integrated single-piece antenna feed 400 to a main reflector 102 of an antenna system 100.
According to yet another embodiment of the integrated single-piece antenna feed 200, 400, the power of an electromagnetic signal propagating from the circular waveguide input 240 is split equally into all four of the branches 730P and 730N of the polarizer 230. According to still another embodiment of the integrated single-piece antenna feed 200, 400, each of the four branches 730P and 730N of the polarizer 230 is equally-spaced around and parallel to the axis 300.
According to still yet another embodiment of the integrated single-piece antenna feed 200, 400, two of the four branches of the polarizer 230 are positive phase-shift waveguide branches 730P, each having a +45° phase-shift and disposed opposite one another relative to the axis 300. According to this same embodiment, the two remaining of the four branches of the polarizer 230 are negative phase-shift waveguide branches 730N, each have a −45° phase-shift. According to this same embodiment, when all four branches 730P and 730N are recombined at the coaxial feed horn 220, recombined power of a wave propagating through the polarizer 230 produces a necessary 90° phase-shift between two equal amplitude linear components of the wave necessary to synthesize right-hand circular polarization (RHCP) and left-hand circular polarization (LHCP).
According to another embodiment of the integrated single-piece antenna feed 200, each of the positive phase-shift waveguide branches 730P comprises a waveguide having a floor 644 closer to the axis 300, a ceiling 642 further from the axis 300 and two opposed walls 648, each wall 648 extending from floor 644 to ceiling 642. The embodiment of the integrated antenna feed 200, 400 may further include a plurality of floor 644 to ceiling 642 rib pairs 660, 662, 664 extending from the opposed walls 648 toward each other for achieving a +45° phase-shift in an electromagnetic wave propagating through the positive phase-shift waveguide branch 730P. According to yet another embodiment of the integrated single-piece antenna feed 200, 400, the plurality of floor 644 to ceiling 642 rib pairs 660, 662, 664 extending from the opposed walls 648 comprises eight rib pairs 660, 662, 664.
According to yet another embodiment of the integrated single-piece antenna feed 200, 400, each of the negative phase-shift waveguide branches 730N comprises a waveguide having a floor 634 closer to the axis 300, a ceiling 632 further from the axis 300 and two opposed walls 638, each of the walls 638 extending from the floor 634 to the ceiling 632. The embodiment of the integrated single-piece antenna feed 200 may further include a plurality of wall 638 to opposed wall 638 rib pairs 650, 652, 654 extending toward each other from the ceiling 632 and the floor 634 configured for achieving a −45° phase-shift in an electromagnetic wave propagating through the negative phase-shift waveguide branch 730N. According to still another embodiment of the integrated single-piece antenna feed 200, 400, the plurality of wall 638 to opposed wall 638 rib pairs 650, 652, 654 extending from the ceiling 632 and the floor 634 comprises eight rib pairs 650, 652, 654.
According to another embodiment of the integrated single-piece antenna feed 200, 400, each of the four branches 730P and 730N of the polarizer 230 comprises a waveguide having a floor 634, 644 extending between the proximal 280 and distal 290 ends and parallel to the axis 300, a ceiling 632, 642 extending between the proximal 280 and distal 290 ends. According to this embodiment, the ceiling 632, 642 may also extend parallel to, and further away from, the axis 300 than the floor 634, 644. This embodiment may further include two opposed walls 638, 648 extending from the floor 634, 644 to the ceiling 632, 642. This embodiment may further include a ridge 636, 646 extending perpendicularly from the ceiling 632, 642 toward the axis 300, effectively bisecting the ceiling 632, 642. According to this embodiment of the integrated single-piece antenna feed 200, 400, the ridge 636, 646 may also extend between the proximal 280 and distal ends 290 parallel to the axis 300.
According to another embodiment of the integrated single-piece antenna feed 200, 400, the modes of electromagnetic wave transmission propagating through the circular waveguide input 240, 440 comprise two orthogonal TE11 modes rotated 90° apart from each other. According to yet another embodiment of the integrated single-piece antenna feed 200, 400, the only mode of electromagnetic wave transmission propagating through the polarizer 230 comprises TE10 mode. According to still another embodiment of the integrated single-piece antenna feed 200, 400, the only mode of electromagnetic wave transmission propagating through a throat of the coaxial feed horn 220 comprises TE11 mode.
According to another embodiment of the integrated single-piece antenna feed 200, 400, the subreflector 210 comprises a circularly symmetric optimized subreflector 210. According to yet another embodiment of the integrated single-piece antenna feed 200, 400, the cylindrical subreflector support 250 comprises a center conductor 250 of the coaxial feed horn 220.
According to another embodiment of the integrated single-piece antenna feed 200, 400, the four wrapped-single-ridged waveguide branches 730P and 730N of the polarizer 230 comprise internal ribs 650, 652, 654, 660, 662 and 664 for generating a circularly polarized output wave from a linearly polarized input wave. According to yet another embodiment of the integrated single-piece antenna feed 200, 400, the antenna feed is formed of a single-piece of metal that cannot be disassembled into its component parts. According to yet another embodiment of the integrated single-piece antenna feed 200, 400, the antenna feed 200, 400 may be manufactured as a single-piece of aluminum using three-dimensional additive metal printing techniques.
According to still another embodiment of the integrated single-piece antenna feed 400, the circular waveguide input 440 may be mounted to an apex 106 of a ring-focus main reflector 102 having a focal length, F, for generating a ring focus 104 within open space between the bell 370 of the coaxial feed horn 220 and the subreflector 210.
An embodiment of a turnstile polarizer 230 disposed between an embodiment of a circular waveguide input 240, 440 and an embodiment of a coaxial feed horn 220 is disclosed. The embodiment of a polarizer 230 may include two wrapped-single-ridged positive phase-shift waveguides 730P. Each positive phase-shift waveguide 730P may have a first and a second end. The embodiment of a polarizer 230 may further include two wrapped-single-ridged negative phase-shift waveguides 730N, each negative phase-shift waveguide 730N having opposite ends (which may be referenced as third and fourth ends in the claims). The embodiment of a polarizer 230 may further include a first transition 260 in communication with the circular waveguide input 240, 440 and the first ends of the two wrapped-single-ridged positive phase-shift waveguides 730P, the first transition 260 also in communication with the third ends of the two wrapped-single-ridged negative phase-shift waveguides 730N. The embodiment of a polarizer 230 may further include a second transition 270 in communication with the coaxial feed horn 230 and the second ends of the two wrapped-single-ridged positive phase-shift waveguides 730P, the second transition 270 also in communication with the fourth ends of the two wrapped-single-ridged negative phase-shift waveguides 730N.
A first alternative embodiment of an integrated single-piece antenna feed having an axis with proximal and distal ends for propagating an electromagnetic wave is disclosed, see for example, and not by way of limitation antenna feed 1000,
Another first alternative embodiment of an integrated single-piece antenna feed may further include a circular waveguide input having a circular opening at the proximal end and extending coaxially toward the distal end. The first alternative embodiment may further include a circular waveguide to ridged waveguide transition coupled to the circular waveguide input extending further along the axis toward the distal end and flaring radially outward relative to the axis into the four ridged rectangular waveguide arms.
According to another first alternative embodiment of an integrated single-piece antenna feed, the coaxial feed horn may further include a plurality of outer circumferential corrugations. Examples of such outer circumferential corrugations may be seen at 1022 (
Yet another first alternative embodiment of an integrated single-piece antenna feed may further include a plurality of symmetrically oriented struts configured for structurally supporting the subreflector. According to this embodiment, each of the plurality of struts may be connected between the outer rim of the subreflector and the outside surface cylindrical conductor of the coaxial turnstile waveguide. According to still another embodiment of the integrated single-piece antenna feed, the plurality of symmetrically oriented struts may include four struts spaced exactly, or about, 90° apart from each other about the axis. The term “about 90°” means “90° plus or minus 10°” as used herein. It will be understood that by symmetrically spacing the struts around the antenna feed the structural support provided by the struts will be maximized. However, it will also be understood that asymmetrical spacing may also achieve suitable structural support for the subreflector. Accordingly, any strut spacing arrangement, symmetrical or asymmetrical, that achieves the goal of physically supporting the subreflector relative to the other features of the antenna feed will be within the scope of the present invention. According to still another embodiment of the integrated single-piece antenna feed, each of the struts may have a trapezoidal cross-section. According to still another embodiment, the antenna feed may be manufactured as a single-piece of metal using three-dimensional additive metal printing techniques.
A second alternative embodiment of an integrated single-piece antenna feed having an axis with proximal and distal ends for propagating an electromagnetic wave is disclosed, see for example, and not by way of limitation, antenna feed 1100 as shown in
According to another second alternative embodiment of an integrated single-piece antenna feed, the coaxial post may further include a tapered portion located coaxially within the circular waveguide input. According to yet another second alternative embodiment of the integrated single-piece antenna feed, the tapered portion located coaxially within the circular waveguide input forms an impedance transition between the circular waveguide input TE11 mode to the coaxial waveguide TE11 mode.
According to yet another second alternative embodiment of an integrated single-piece antenna feed, the coaxial feed horn may further include an inner surface having a frusto-conical profile. According to still another second alternative embodiment of the integrated single-piece antenna feed, the coaxial feed horn may further include an outer surface having a plurality of outer circumferential corrugations.
According to still another second alternative embodiment of an integrated single-piece antenna feed, the plurality of symmetrically oriented struts may include four struts spaced exactly, or about, 90° apart from each other about the axis. According to another second alternative embodiment of the integrated single-piece antenna feed, each of the struts may have a cross-sectional shape selected from the group consisting of: trapezoidal, diamond, triangular, circular, oval and square.
A third alternative embodiment of an integrated single-piece antenna feed having an axis with proximal and distal ends for propagating an electromagnetic wave is disclosed, see for example, and not by way of limitation, antenna feed 1200 as shown in
According to another third alternative embodiment of an integrated single-piece antenna feed, the feed horn may further include an inner surface having a frusto-conical profile. According to yet another third alternative embodiment of an integrated single-piece antenna feed, the feed horn may further include an outer surface having a plurality of outer circumferential corrugations. According to still another third alternative embodiment of an integrated single-piece antenna feed, the plurality of symmetrically oriented struts may be four struts spaced exactly, or about, 90° apart from each other about the axis. According to still yet another third alternative embodiment of an integrated single-piece antenna feed, each of the plurality of struts may have any suitable cross-sectional shape, including but not limited to trapezoidal, diamond, triangular, circular, oval and square.
A fourth alternative embodiment of an integrated single-piece antenna feed having an axis with proximal and distal ends for propagating an electromagnetic wave is disclosed, see for example and not by way of limitation, antenna feed 1300 shown in
According to another fourth alternative embodiment of an integrated single-piece antenna feed, the plurality of struts may be four symmetrically oriented struts spaced exactly, or about, 90° apart from each other about the axis. According to yet another fourth alternative embodiment of an integrated single-piece antenna feed, each of the plurality of struts may have any suitable cross-sectional shape, including but not limited to trapezoidal, diamond, triangular, circular, oval and square.
In understanding the scope of the present invention, the term “configured” as used herein to describe a component, section or part of a device includes hardware and/or software that is constructed and/or programmed to carry out the desired function. In understanding the scope of the present invention, the term “comprising” and its derivatives, as used herein, are intended to be open ended terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and/or steps. The foregoing also applies to words having similar meanings such as the terms, “including”, “having” and their derivatives. Also, the terms “part,” “section,” “portion,” “member” or “element” when used in the singular can have the dual meaning of a single part or a plurality of parts. As used herein to describe the present invention, the following directional terms “top, bottom, forward, rearward, above, downward, vertical, horizontal, below and transverse” as well as any other similar directional terms refer to those directions of an embodiment of an integrated single-piece antenna feed 200, 400, as oriented in a given FIG. The terms “air volume” 630P, 630N and “waveguide cavity” 630P, 630N are used synonymously herein in reference to the interior space of its associated “waveguide branch” 730P, 730N. Finally, terms of degree such as “substantially”, “about” and “approximately” as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed.
It will further be understood that the present invention may suitably comprise, consist of, or consist essentially of the component parts, method steps and limitations disclosed herein. However, the invention illustratively disclosed herein suitably may be practiced in the absence of any element which is not specifically disclosed herein.
While the foregoing advantages of the present invention are manifested in the detailed description and illustrated embodiments of the invention, a variety of changes can be made to the configuration, design and construction of the invention to achieve those advantages. Hence, reference herein to specific details of the structure and function of the present invention is by way of example only and not by way of limitation.
This US continuation-in-part patent application claims benefit and priority to international patent application No. PCT/US2017/056805, filed on Oct. 16, 2017, pending, which in turn claims benefit and priority to U.S. continuation patent application Ser. No. 15/679,137, filed on Aug. 16, 2017, titled: INTEGRATED SINGLE-PIECE ANTENNA FEED AND CIRCULAR POLARIZER, issued as U.S. Pat. No. 9,960,495 on May 1, 2018, which in turn claims benefit and priority to U.S. non-provisional patent application Ser. No. 15/445,866, filed on Feb. 28, 2017, titled “INTEGRATED SINGLE-PIECE ANTENNA FEED”, issued as U.S. Pat. No. 9,742,069 on Aug. 22, 2017, which in turn claims benefit and priority to U.S. provisional patent application No. 62/409,277 filed on Oct. 17, 2016, titled “INTEGRATED SINGLE-PIECE ANTENNA FEED”, the contents of all of which are incorporated by reference as if fully set forth herein.
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| F.I. Sheftman, “Experimental Study of Subreflector Support Structures in a Cassegrainian Antenna”, Technical Report 416, Sep. 23, 1966, Lincoln Laboratory, Massachusetts Institute of Technology, Lexington, MA. |
| Number | Date | Country | |
|---|---|---|---|
| 20180294573 A1 | Oct 2018 | US |
| Number | Date | Country | |
|---|---|---|---|
| 62409277 | Oct 2016 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15445866 | Feb 2017 | US |
| Child | 15679137 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15679137 | Aug 2017 | US |
| Child | 15968463 | US |
