Low Swap Aperture for Ultra Wideband Direction Finding

Abstract

A wideband direction finding (WBDF) aperture uses a limited number of ultra-wideband endfire antenna elements that can cover a wide frequency bandwidth. By arranging variable size antenna elements in a specific pattern, the WBDF aperture enables direction finding capability covering an ultra-wide frequency band. The pattern arrangement of variable size elements provides signal discrimination capability limiting ambiguity in signal arrival angle. This small form factor design allows the WBDF aperture to be mounted on the surface of a missile, projectile, or small UAS wing or fuselage. The WBDF aperture provides a combination of different size antenna elements arranged in a specific pattern combined with direction finding and signal tracking to provide unambiguous relative azimuth and elevation angles of a target.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. patent application Ser. No. 17 / 242,347, filed Apr. 28, 2002, and is related to U.S. Patent No. 9,614,275, entitled "Methods and Apparatus for Wide Bandwidth Antenna with Enhanced Connection," assigned to Raytheon Company (USA), each of which is incorporated herein by reference in its entirety. [Background technology]

[0002] Most radar antenna apertures capable of direction finding (monopulse, interferometer, etc.) operate over a specific, limited frequency band, so multiple apertures are needed to cover a wide frequency band. Conventional systems may use multiple apertures to cover such a wide frequency band.

[0003] Missiles and unmanned aircraft systems (UAS) may have limited weight and space to mount antennas. Every increase in weight and / or structure may have a direct negative impact on drag and range. Multiple apertures may directly reduce range.

[0004] Thus, there remains a need for systems and related methods that can overcome these limitations and provide new solutions for lightweight, small form factor antenna design that enables wide frequency range and robust performance. Summary of the Invention

[0005] One embodiment of the inventive concepts disclosed herein may relate to a wideband direction finding aperture that includes a single planar array having at least four or more antenna elements, one antenna element having a first size and another antenna element having a second size smaller than the first size, with each of the antenna elements operating in tandem and configured for wide frequency bandwidth signal reception to enable DF (direction finding) of targets.

[0006] Additional embodiments of the inventive concepts disclosed herein may relate to a wideband direction finding system. The system includes a single planar array having four or more antenna elements configured for wide frequency bandwidth signal reception with each of the antenna elements operating in tandem. The antenna elements may be oriented in a pattern relative to the array center point that allows for resolution of ambiguities during signal reception.

[0007] For control, the system may include a vehicle controller operatively coupled to each of the antenna elements and the aircraft functions, the vehicle controller may be coupled to a tangible non-transitory memory configured to communicate with the vehicle controller, the tangible non-transitory memory having instructions stored therein that, responsive to execution by the vehicle controller, cause the vehicle controller to perform each function of the system.

[0008] In the function, the system may receive a composite signal from a single planar array and determine whether at least one measurement is an unrealistic measurement based on at least one of an azimuth angle or an elevation angle associated with at least one measurement from the composite signal. The vehicle controller may discard the at least one unrealistic measurement as an ambiguity and process the composite signal to determine an azimuth angle and an elevation angle of the target. The vehicle controller may then command an aircraft function to perform at least one vehicle function in response to the azimuth angle and the elevation angle.

[0009] Additional embodiments of the inventive concepts disclosed herein may relate to a wideband direction finder for an aircraft. The direction finder may include a single planar array having at least four antenna elements, the antenna elements configured to receive signals and generate a composite signal, and operatively associated with the aircraft. The antenna elements may be substantially non-overlapping and adjacent to at least one other antenna element, at least one of the antenna elements being smaller in size. The direction finder may include a vehicle controller operatively coupled to each of the antenna elements and the aircraft functions, and a tangible non-transitory memory configured to communicate with the vehicle controller, the tangible non-transitory memory having instructions stored therein that, in response to execution by the vehicle controller, cause the vehicle controller to perform each function of the direction finder.

[0010] In the function, the vehicle controller may determine whether at least one measurement from the composite signal is an unrealistic measurement based on at least one of the azimuth angle or the elevation angle, discard the at least one unrealistic measurement as an ambiguity, and process the composite signal to determine an azimuth angle or an elevation angle of the target. The vehicle controller may then command an aircraft function to perform at least one aircraft function in response to the azimuth angle and the elevation angle.

[0011] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the inventive concepts and, together with the general description, serve to explain the principles of the inventive concepts disclosed herein.

[0012] Implementations of the inventive concepts disclosed herein may be better understood upon consideration of the following detailed description. Such description refers to the accompanying drawings, which are not necessarily to scale and in which some features may be exaggerated, some features omitted, or depicted diagrammatically for clarity. Like reference numbers in the drawings may represent and refer to the same or similar elements, features, or functions. In the drawings: [Brief description of the drawings]

[0013] [Figure 1] FIG. 2 is a diagram of one orientation of a wideband direction finding aperture in accordance with an embodiment of the inventive concepts disclosed herein. [Figure 2A] FIG. 2 is a diagram of an individual antenna element according to an embodiment of the inventive concepts disclosed herein. [Figure 2B] FIG. 2 is a diagram of an individual antenna element according to an embodiment of the inventive concepts disclosed herein. [Diagram 3] FIG. 2 is an exemplary element coordinate separation diagram of an embodiment of the inventive concepts disclosed herein. [Figure 4] FIG. 2 is an exemplary aperture bandwidth diagram of one embodiment of the inventive concepts disclosed herein. [Diagram 5] FIG. 1 is a diagram of a wideband direction finding system according to one embodiment of the inventive concepts disclosed herein. [Figure 6] 1A and 1B are graphs of an exemplary flight profile and target angles according to one embodiment of the inventive concepts disclosed herein. [Figure 7A] 1 is a graph of exemplary azimuth and elevation performance versus time in accordance with one embodiment of the inventive concepts disclosed herein. [Figure 7B] 1 is a graph of exemplary azimuth and elevation performance versus time in accordance with one embodiment of the inventive concepts disclosed herein. [Figure 8] 1 is a graph of an example angular error associated with one embodiment of the inventive concepts disclosed herein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Before describing in detail at least one embodiment of the inventive concept disclosed herein, it should be understood that the inventive concept is not limited in its application to the details of construction and the arrangement of components or steps or methodologies set forth in the following description or illustrated in the drawings. In the following detailed description of the embodiments of the inventive concept, numerous specific details are set forth in order to provide a more thorough understanding of the inventive concept. However, it will be apparent to those skilled in the art that the present disclosure may be practiced without these specific details. In other instances, well-known features may not be described in detail in order to avoid unnecessarily complicating the present disclosure. The inventive concept disclosed herein may be capable of other embodiments or may be practiced or carried out in various ways. It should also be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting.

[0015] As used herein, letters following a reference number are intended to refer to embodiments of features or elements that are similar, but not necessarily identical, to the preceding element or feature having the same reference number (e.g., 1, 1a, 1b). Such shorthand notations are used for convenience only and should not be construed as limiting in any way the inventive concepts disclosed herein, unless expressly stated to the contrary.

[0016] As used herein, the term "approximately" in claim language and specification language may refer to a range of values ​​of ±20 percent (+ / - 20%) of the claimed value. For example, "approximately 100" may refer to and be claimed as a range of 80 to 120.

[0017] Furthermore, unless expressly stated to the contrary, "or" refers to an inclusive or, not an exclusive or. For example, a condition A or B is satisfied by any one of: A being true (or present) and B being false (or not present); A being false (not present) or B being true (or present); and both A and B being true (or present).

[0018] Additionally, "a" or "one" are employed to describe elements and components of embodiments of the inventive concepts. This is done merely for convenience and to give a general sense of the inventive concepts, so that "a" and "one" are intended to include one or at least one, and the singular forms include the plural forms unless otherwise clearly intended.

[0019] Finally, as used herein, any reference to "one embodiment" or "some embodiments" means that a particular element, feature, structure, or feature described in connection with an embodiment is included in at least one embodiment of the inventive concepts disclosed herein. The phrase "in some embodiments" appearing in various places in this specification do not necessarily all refer to the same embodiments, and embodiments of the disclosed inventive concepts may include one or more of the features explicitly described or inherently present in this specification, or any combination of subcombinations of two or more such features, as well as any other features that may not necessarily be explicitly described or inherently present in this disclosure.

[0020] overview In general, embodiments of the inventive concepts disclosed herein relate to a wideband direction finding (WBDF) aperture that uses a limited number of ultra-wideband endfire antenna elements capable of covering a wide frequency bandwidth. By arranging variable sized antenna elements in a specific pattern, the WBDF aperture provides direction finding capability that enables correlation interferometry and covers an ultra-wide frequency band. The pattern of variable sized elements provides signal discrimination capability that limits ambiguity in signal arrival angle. This small form factor design allows the WBDF aperture to be mounted on the surface of a missile, projectile, or small UAS wing or fuselage. The WBDF aperture provides a combination of different sized antenna elements arranged in a specific pattern combined with correlation interferometry and signal tracking to provide unambiguous relative azimuth and elevation of a target. [Table 1]

[0021] Figure 1 WBDF aperture 1, a diagram of one orientation 100 of a wideband direction finding aperture in accordance with an embodiment of the inventive concepts disclosed herein is shown. In general, a WBDF (wideband direction finding aperture) 120 may include a planar array including four exemplary elements 122, 124, 126, 128 configured to operatively couple with an aircraft 130. For the orientation, the WBDF aperture 120 may be mounted on the underside of the aircraft 130 where the WBDF aperture 120 may be in a position to image potential ground targets.

[0022] The WBDF aperture 120 may provide an array configuration with a unique offset layout that provides direction finding (DF) performance while minimizing one or more ambiguities over a wide band of operating frequencies. The WBDF aperture 120 may include multiple apertures configured to cover a wide spectrum of a desired frequency band. In one embodiment, the WBDF aperture 120 may include multiple planar arrays of sufficient depth to enable advanced functionality through regularly spaced arrays (e.g., constant spacing between individual elements). The WBDF aperture 120 may provide an arrangement of conformal endfire antennas oriented in a specific pattern that enables direction finding by correlation interferometry.

[0023] In one embodiment, the aircraft 130 may include a projectile, manned or unmanned aerial vehicle, or spacecraft to which the WBDF aperture 120 is operatively coupled. In one embodiment, the WBDF aperture 120 may be coupled to a weapon system or multi-role platform that enables both kinetic kill and electronic surveillance and attack. Some aircraft 130 may employ multiple sensor systems to support various functions where the WBDF aperture 120 may be one of many on-board sensors.

[0024] In one embodiment, each of the aircraft 130 and planar arrays 122-128 may be oriented along a y-axis 162 that is generally parallel to the direction of flight 172, a z-axis 166 that is generally parallel to the aircraft weight vector, and an x-axis 164 that is generally perpendicular to each of the y-axis 162 and z-axis 166.

[0025] As used herein, the forward direction 150 may be parallel to the flight direction 172 of the aircraft 130, while the aft direction 152 may be opposite to the flight direction 172. Similar to the wings of an airplane, the left direction 154 and the right direction 156 may be opposite to the x-axis 164. Finally, the upward direction 158 and the downward direction 160 may be oppositely oriented along the z-axis 166, with the downward direction 160 being parallel to the weight vector of the aircraft. Here, the forward direction 150, the upward direction 158, and the left direction 154 may follow the right-hand rule.

[0026] In one embodiment of the inventive concepts disclosed herein, the WBDF aperture 120 may be configured (e.g., length, width, depth, connectivity) for insertion within an aperture cavity installed on an aircraft. The size of some aperture cavities may be variable to minimize the overall aircraft size weight and power SWaP, and the aperture cavities may be restricted to a planar or conformal orientation that can accommodate the limited size. The WBDF aperture 120 may be specially sized to fit within an aperture cavity of one or more different aircraft 130. In one embodiment, the WBDF aperture 120 may be specially sized for insertion within an aperture cavity of a projectile.

[0027] In one embodiment, the WBDF aperture 120 may be oriented parallel to a horizontal plane defined by a y-axis 162 and an x-axis 164, respectively. Here, the WBDF aperture 120 may be oriented toward a downward direction 160 such that each of the beams 112-118 can image targets that are physically below (below 160) and in front 162 of the WBDF aperture 120.

[0028] For further orientation, the WBDF aperture 120 may have an array center point 104 that coincides with the z-axis 166 of the planar array. The array center point 104 may be useful for defining the relative positions of each of the individual elements 122-128 as their relative distance in the horizontal plane from the array center point 104.

[0029] In one embodiment of the inventive concepts disclosed herein, each of the individual elements 122-128 may be configured for wide frequency bandwidth signal reception to enable wideband correlated phase interferometric direction finding of a target. During signal reception, ambiguities may exist in the received signal, which may cause errors in positioning of the target. In one embodiment, the WBDF aperture 120 may be configured to enable the aircraft signal processor to limit one or more ambiguities associated with signal reception.

[0030] In one embodiment of the inventive concepts disclosed herein, each antenna element of the planar array may be mounted adjacent to another antenna element of the planar array without overlapping. In one exemplary embodiment, an individual element may be positioned within the WBDF aperture 120 directly adjacent to one side of another individual element. Another exemplary embodiment may include a small spacing between one individual element and the next. Smaller spacing (e.g., between elements) may also be desired as a smaller overall size of the WBDF aperture 120 may be desired. In one embodiment, the array length 106 may be approximately 5.67 inches along the y-axis 162, while the array width 108 may be approximately 4.15 inches along the x-axis 164. In one embodiment, a single planar array may be approximately 4.7 to 6.7 inches along the y-axis and approximately 3.1 to 5.1 inches along the x-axis.

[0031] In one embodiment, the WBDF aperture 120 may be oriented approximately planar with the horizontal plane. As previously mentioned, a forward field of view within approximately 90 degrees of the y-axis in azimuth combined with a vertical downward field of view within approximately + / - 90 degrees below the z-axis to image targets on the Earth's surface may enable the WBDF aperture 120 to image the Earth's surface targets.

[0032] In one embodiment, the WBDF aperture 120 may be configured to be planar so as to seamlessly mount to the underside of a particular aircraft 130. For example, an embodiment of the WBDF aperture 120 mounted to an aircraft wing or fuselage may be approximately planar in shape to match the exterior plane of the aircraft. Some embodiments may also include curved versions of the WBDF aperture 120 to fit the exterior contour of the aircraft 130. For example, a bullet with an outside diameter of 24 inches may maintain a particular exterior curvature. The WBDF aperture 120 may be conformally shaped to fit the particular exterior curvature.

[0033] In one embodiment, the WBDF aperture 120 may include a first antenna element 122 having a first element size (A) configured to receive signals in a first segment of a wide frequency bandwidth via a first element beam pattern 112. The first antenna element has a first element center point 142.

[0034] In one embodiment, the WBDF aperture 120 may include a second antenna element 124 having a first element size (A), which may be configured for signal reception of a second segment of the wide frequency bandwidth via the second element beam pattern 114, and which has a second element center point 144. Each center point of each antenna element may be approximately centered between the length (y-axis) and width (z-axis) of the individual antenna element.

[0035] In one embodiment, the WBDF aperture 120 may include a third antenna element 126 having a first element size (A), which may be configured for signal reception of a third segment of the wide frequency bandwidth via a third element beam pattern 116, and which has a third element center point 146.

[0036] In one embodiment, the WBDF aperture 120 may include a fourth antenna element 128 having a second element size (B) approximately half the first element size (A), configured for signal reception in a fourth segment of the wide frequency bandwidth via a fourth element beam pattern 118, the fourth antenna element 128 having a fourth element center point 148. In one embodiment, the first and second element sizes may be rectangular.

[0037] As contemplated herein, the size and location of each antenna element 122-128 may be adjusted to remain within the scope of the inventive concepts herein, however, one constant herein may be a number of inexpensive, desirably low power individual antenna elements closely spaced to form the WBDF aperture 120.

[0038] Figure 2 Individual elements 2A and 2B, diagrams of an individual antenna element 300 are shown in accordance with embodiments of the inventive concepts disclosed herein. An exemplary individual antenna element (shown here as first antenna element 122) may perform an individual element function and, when combined with additional element functions of multiple elements, may provide the overall function of the WBDF aperture 120.

[0039] In one embodiment of the inventive concepts disclosed herein, each antenna element of the planar array may be a directional instantaneous wide bandwidth planar antenna including an elongated dielectric feed aligned with a y-axis. In one embodiment, each of the individual elements 122-128 may be similar to the antenna elements disclosed in U.S. Pat. No. 9,614,275, but sized to fit within the WBDF aperture 120. Each of the individual antenna elements may be individually powered and configured to operably couple to the aircraft via a cable. In one embodiment, the cable may be a coaxial type cable for connection of the individual elements. The antenna element 122 may include a cover 134 and be coupled to the aircraft 130 via a cable connection 132. In some embodiments, the antenna element 122 may include an aperture 136 associated with the elongated dielectric feed to provide for transmission and reception of radar energy.

[0040] In one embodiment of the inventive concepts disclosed herein, the WBDF aperture 120 may provide wide bandwidth, highly directional, linearly polarized light in a shallow conformal package. The WBDF aperture 120 may provide a wide instantaneous frequency bandwidth corresponding to a highly directional focused beam with approximately 25 dB front-to-back ratio at higher frequencies within the wide bandwidth. The WBDF aperture 120 may enable desirable exploitable gain for precision target signature (PTS) radar performance when used with a rear-looking communications antenna (not shown).

[0041] In one embodiment, the first size may be approximately 2.8 inches (approximately 2.3 to 3.3 inches) along the y-axis 162 and approximately 1.4 inches (0.9 to 1.9 inches) along the x-axis 164, and the second size may be approximately 1.4 inches (0.9 to 1.9 inches) along the y-axis 162 and 0.7 inches (0.2 to 1.2 inches) along the x-axis 164. In some embodiments, therefore, each individual antenna element and WBDF aperture 120 may be maintained at a depth along the z-axis of less than approximately 0.25 inches, and in some embodiments 0.15 inches. With the additional cover 134 of approximately 0.050 inches, one exemplary overall thickness may be 0.20 inches.

[0042] In one embodiment, the antenna elements 122 may be scaled to achieve higher or lower frequencies to increase the available bandwidth. For example, smaller sized elements may enable higher frequency potential, while larger sized individual elements may enable lower frequencies. In some embodiments, the WBDF aperture 120 may be insensitive to manufacturing tolerances and material variations.

[0043] At lower frequencies, larger spacing between each of the individual elements 122 may be beneficial if the elements are of sufficient size (A, B smaller, larger) to limit the spacing, whereas at higher frequencies, smaller element spacing may be desired. The physical size limitations of the cavity into which the wideband DF aperture 120 fits may be a determining factor in the overall size of the WBDF aperture 120. In one embodiment, smaller elements may allow for smaller center-to-center spacing along each of the x-axis 164 and y-axis 162, enabling higher frequency performance and capability.

[0044] In one embodiment of the inventive concepts disclosed herein, the WBDF aperture 120 may be configured for a forward field of view having an azimuth potential 222 within approximately + / - 180 degrees of the forward y-axis 162 and an elevation potential 220 approximately + / - 90 degrees below the z-axis 166. In some embodiments, the elevation potential 220 may be substantially greater than the 180 degrees shown, depending on the aircraft configuration, aircraft size, and available radar penetration of the aircraft configuration.

[0045] Figure 3. Placement Referring now to FIG. 3, a diagram of an exemplary element coordinate separation 300 of an embodiment of the inventive concepts disclosed herein is shown. Each individual element 122-128 may be slightly offset from the other elements to reduce ambiguity in the estimated direction of arrival based on the relative phase of the received signal at each element. These precise signals may enable the overall ability of the WBDF aperture 120 to achieve high certainty of target location. Offsetting the center location of each of the elements relative to the array center point 104 may serve to reduce ambiguity across the entire frequency bandwidth.

[0046] Exemplary distances from the center point 104 may be represented in the following table: [Table 2]

[0047] In one embodiment, the first element center point 142 may be oriented at a forward distance and a second right distance from the array center point 104. In one embodiment, the forward distance may be approximately 1.39 inches and the second right distance may be approximately 0.65 inches.

[0048] In an additional embodiment, the second element midpoint 144 may be oriented at a second back distance and a first right distance from the array midpoint 104. In one embodiment, the second back distance may be approximately 1.43 inches and the second right distance may be approximately 0.41 inches.

[0049] In another embodiment, the third element center point 146 may be oriented at a first distance back and a distance to the left from the array center point 104. In one embodiment, the left distance may be approximately 1.29 inches and the first distance back may be approximately 1.15 inches.

[0050] In one embodiment, the fourth element midpoint 146 may be oriented approximately a first distance back and a third distance to the right from the array midpoint 104. In one embodiment, the third distance to the right may be approximately 1.66 inches.

[0051] Here, the first rear distance may be smaller than the second rear distance, and the first right distance may be smaller than the second right distance which is smaller than the third right distance.

[0052] In one embodiment, the front distance can be approximately 1.0 to 2.0 inches, the first rear distance can be approximately 0.7 to 1.7 inches, the second rear distance can be approximately 1.0 to 2.0 inches, the left distance can be approximately 0.8 to 1.8 inches, the first right distance can be approximately 0.1 to 1.1 inches, the second right distance can be approximately 0.1 to 1.1 inches, and the third right distance can be approximately 1.1 to 2.1 inches.

[0053] In one embodiment, the four antenna elements may be oriented in a pattern with respect to the array center point 104. The pattern orientation and spacing may allow for resolution of signal reception ambiguities. In one embodiment, the pattern may include one antenna element oriented forward of the center point 104, one or more antenna elements oriented rearward of the center point 104, one antenna element oriented to the left of the center point 104, and one or more antenna elements oriented to the right of the center point 104.

[0054] Figure 4 Aperture bandwidth 4, a diagram of an exemplary aperture bandwidth 400 of one embodiment of the inventive concepts disclosed herein is shown. In one embodiment, the WBDF aperture 120 may segment the wide bandwidth of the array functionality into individual segments for each of the individual antenna elements 122-128. A first element frequency segment 422, a second element frequency segment 424, a third element frequency segment 426, and a fourth element frequency segment 428 may correspond to each of the individual antenna elements. For example, the first antenna element 122 may be assigned the first frequency segment 422, and the second antenna element 124 may be assigned the second segment 424.

[0055] In another embodiment, each frequency segment may be assigned to an individual antenna element based on the element's relative position from the center point 104. For example, a particular frequency segment (e.g., 3) may be the frequency segment for which the WBDF aperture 120 may be specifically targeted. In this manner, an operator may tune a desired frequency to a desired antenna element and therefore the overall aperture performance.

[0056] In one embodiment of the inventive concepts disclosed herein, each of the first segment 422 through the fourth segment 428 of the wide frequency bandwidth is approximately three to five (3-5) GHz wide. For example, the first antenna element 122 may be configured to cover the width of the exemplary frequency segment 422 from frequency a to frequency d. Similarly, the second antenna element 124 may be configured to cover the second segment 424 from frequency c to frequency f. Additionally, the size of one segment of the wide frequency band may be inversely proportional to the size of the second element.

[0057] In one embodiment, one of the first to fourth segments of the wide frequency bandwidth may include a set of frequencies, and the fractional bandwidth of the set of frequencies is greater than 1. For example, the fractional bandwidth may be defined as follows:

number

[0058] where fMax 404 (frequency I) may be the single highest operating frequency and fMin 402 (frequency A) may be the single lowest operating frequency.

[0059] In an exemplary embodiment, the wide frequency bandwidth may extend from fMin 401 to fMax 404 depending on the user's specifications. For example, one exemplary wide bandwidth may extend from C-band (4 GHz) to Ka-band (40 GHz), while another exemplary wide frequency bandwidth may extend from L-band (1 GHz) to Ku-band (18 GHz). These non-limiting examples may help illustrate that the wide frequency bandwidth may be tailored based on the user's needs and overall aperture size.

[0060] In one embodiment, the WBDF aperture 120 employing a planar array may be either active, passive, or semi-active to function appropriately with the aircraft to which it is coupled. For example, an aircraft 130 pointed at an active emitter may function passively, while a UAS may require it to function actively for ground mapping.

[0061] Figure 5 System 5, there is shown a diagram of a wideband direction finding system 500 in accordance with one embodiment of the inventive concepts disclosed herein. In operation, the system 500 may employ the WBDF aperture 120 to perform one or more functions.

[0062] In one embodiment of the inventive concepts disclosed herein, the system 500 may include a WBDF aperture 120 in which each of the individual antenna elements may be operatively coupled to the aircraft 130 via a cable connection 132 .

[0063] In an embodiment, the system 500 may include downconversion, digitization, and feature extraction 512-518 via downconverters individually coupled to each of the individual antenna elements 122-128. A direction finding (DF) processor 520 may function to combine each of the individual signals and communicate the combined signal to a vehicle controller 522. The vehicle controller 522 may be operatively coupled to each of the elements of the planar array and to vehicle functions 524.

[0064] For control, the tangible non-transitory memory 526 may be configured to communicate with the vehicle controller 522, and the tangible non-transitory memory 526 has stored therein instructions that, in response to execution by the vehicle controller 522, cause the vehicle controller 522 to perform the functions of the system 500.

[0065] In function, the vehicle controller 522 may receive a composite signal from a planar array in the WBDF aperture 120 and determine whether at least one measurement is an unrealistic measurement based on an azimuth angle and an elevation angle associated with at least one measurement from the composite signal, where the vehicle controller 522 may operate to resolve ambiguities associated with the received signal, such that the vehicle controller 522 may discard the unrealistic measurement as an ambiguity.

[0066] In one embodiment, the vehicle controller 522 may also process the received signals using correlative phase interferometric direction finding to determine the azimuth and elevation angles of the target and command the vehicle function 524 to perform at least one vehicle function in response to the azimuth and elevation angles.

[0067] In one embodiment, the vehicle functions may include autopilot commands to fly the aircraft 130, a camera function to perform one or more imaging shots via a separate system, direction for one or more additional functions associated with the vehicle, and a semi-active radar function to change the radar mode of the WBDF aperture 120.

[0068] In one embodiment, the measurements may include an azimuth measurement combined with an elevation measurement, and the vehicle controller 522 analyzes each of the azimuth and elevation measurements in a lookup table in memory 526 to determine the ambiguity. Another embodiment may include the vehicle controller 522 functioning to discard the first and second measurements and use a third or possibly fourth measurement to determine the azimuth and elevation angles.

[0069] Figure 6 Flight profile 6A and 6B, there are shown graphs of an exemplary flight profile 600 in accordance with one embodiment of the inventive concepts disclosed herein. The exemplary flight 600 of the aircraft 130 may include a 400 second flight time spanning a range of 120,000 feet from a launch point 602 to a ground target 604.

[0070] For example, at time 200 with a range of approximately 60,000 feet, the azimuth angle is near zero (the vehicle's y-axis points toward the target), the elevation angle is approximately +10, the aircraft 130 may be pitching up slightly (e.g., the y-axis of the aircraft 130 points above the target), and the altitude of the aircraft 130 is approximately 10,000 feet.

[0071] For example, at time 0 at launch point 602 when the aircraft 130 has just been launched on an exemplary flight profile, the elevation angle of the target (assumed to be fixed) relative to the y-axis 162 may be at its highest point +30 (e.g., 30 degrees below the aircraft's flight direction 172).

[0072] 6 may detail a single example to help illuminate DF capabilities in flight paths that provide several angular diversity, flight times, ranges, altitudes, etc. that are not limited to similar use cases. The WBDF aperture 120 may be directly applied to a small UAV flying slow and level at a constant altitude, or a bullet flying at supersonic speeds, or anything in between, as well as many other options.

[0073] Figure 7 Azimuth and elevation angles 7A and 7B, an example azimuth and elevation graph 700 over time is shown associated with one embodiment of the inventive concepts disclosed herein. An example sample time slice 606 may represent one sample of measurements taken by the WBDF aperture 120.

[0074] FIG. 7A may show azimuth angles over time, while FIG. 7B may show elevation angles over time. Each detection by the WBDF aperture 120 may have an associated azimuth and elevation pair. While a particular azimuth or elevation angle may be possible when considered individually, due to projection into three-dimensional Cartesian coordinates, the pair of angles may be considered unrealistic in spherical coordinates. FIGS. 7A and 7B may show the measured angles individually, discarding measurements that are considered unrealistic as measurement pairs. Each graph may represent an angle relative to (or measured from) the forward direction 150 along the y-axis (e.g., boresight) of the planar array, and at each particular time instant, a pair of measurements may be available to the vehicle controller 522 or additional system analysis.

[0075] The truth curve may represent the actual azimuth and elevation angles of the target, and the discarded measurements may indicate those unrealistic measurements that fall outside a predetermined error range. These azimuth and elevation pairs cause returns other than approximately below and in front of the aircraft 130 to be labeled as unrealistic and discarded.

[0076] 7A, for example, in sample time slice 606 at time 170, three azimuth measurements are each approximately −1 degree in azimuth, while two unrealistic measurements are +90 and −90 degrees to the left and right of the boresight. Two additional unrealistic measurements are +180 and −180 degrees, respectively, from the boresight (e.g., at the 6 o'clock position for a planar array), further within the range of unrealistic measurements.

[0077] 7B, at the same time slice 606, the elevation angle relative to the y-axis may be shown as in FIG. 6. Here, the aircraft 130 may be flying a particular flight profile in which the pitch of the aircraft 130 may go up and down as shown by the truth curve, so that elevation angle measurements outside the error range may be discarded as unrealistic. The shown measurements of elevation angles that are 5, 4, 3, and 2 may be considered valid, while the additional ambiguities at 0, +6, and +7 are removed as unrealistic. Most of the ambiguities may be erroneous returns from above the aircraft 130, rather than the desired line of sight below the aircraft 130.

[0078] Fig. 8 Angle error 8, there is shown an example angular error 800 diagram of one embodiment of the inventive concepts disclosed herein. FIG 8 may show the resulting angular accuracy performance as a measure of SNR.

[0079] conclusion As can be appreciated from the above discussion, embodiments of the inventive concepts disclosed herein may provide novel solutions for lightweight, small form factor antenna design enabling wide frequency range and robust performance.

[0080] It should be understood that embodiments of methods according to the inventive concepts disclosed herein may include one or more of the steps described herein. Moreover, such steps may be performed in any desired order, and two or more steps may be performed simultaneously with one another. Two or more of the steps disclosed herein may be combined into a single step, and in some embodiments, one or more of the steps may be performed as two or more sub-steps. Furthermore, other steps or sub-steps may be performed in addition to, or as an alternative to, one or more of the steps disclosed herein.

[0081] From the foregoing description, it is apparent that the inventive concepts disclosed herein are well adapted to carry out the objects and attain the advantages set forth herein as well as those inherent therein. While presently preferred embodiments of the inventive concepts disclosed herein have been described for purposes of this disclosure, it will be understood that numerous modifications may be made which will be readily suggested to those skilled in the art and which are accomplished within the broad scope and applicability of the inventive concepts disclosed and claimed herein.

Claims

1. An array having at least four antenna elements, an array center point, an x-axis, a y-axis, and a z-axis, the at least four antenna elements being endfire antenna elements having a beam pattern oriented along the y-axis, the at least four antenna elements comprising: a first antenna element of a first size having a first element center point; a second antenna element of the first size having a second element center point; a third antenna element of the first size having a third element center point; a fourth antenna element of a second size having a fourth element center point, the second size being smaller than the first size; The array is configured for wide frequency bandwidth signal reception to enable direction finding of a target, the at least four antenna elements are oriented in a pattern, the pattern configured to limit at least one ambiguity associated with the signal reception, the pattern comprising: the first element center point oriented at a forward distance and a second rightward distance from the array center point; the second element center point oriented a second distance back and a first distance to the right from the array center point; the third element center point oriented at a first distance back and left from the array center point; the fourth element center point oriented at the first rear distance and a third right distance from the array center point, wherein the first rear distance is smaller than the second rear distance, the front distance is larger than the first rear distance and smaller than the second rear distance, the first right distance is smaller than the second right distance, the second right distance is smaller than the third right distance, and the third right distance is larger than the left distance, the array center point is aligned with the x-axis, the y-axis, and the z-axis, and front and rear are in opposite directions along the y-axis and left and right are in opposite directions along the x-axis. Wideband direction finding aperture.

2. A wideband direction finding aperture as described in claim 1, wherein the first antenna element and the second antenna element overlap the y-axis and the third antenna element overlaps the x-axis.

3. 2) configured for insertion within an aperture cavity mounted on the aircraft; 3) configured for operative coupling with the aircraft via a cable; and 4) shaped to be one of planar or conformal with the aperture cavity, wherein the y-axis is parallel to a direction of flight of the aircraft.

4. 2. The wideband direction finding aperture of claim 1, wherein said array is planar and aligned parallel to a plane defined by said y-axis and said x-axis.

5. The wideband direction finding aperture of claim 1, wherein the first size and the second size are rectangular.

6. 2. The wideband direction finding aperture of claim 1, wherein each antenna element of the at least four antenna elements is mounted adjacent to but not overlapping another antenna element of the array and configured to provide a field of view within 90 degrees in azimuth of the y-axis and 90 degrees in elevation of the z-axis.

7. 10. The wideband direction finding aperture of claim 1, wherein the array is one of active, passive or semi-active.

8. 2. The wideband direction finding aperture of claim 1, wherein the first antenna element is further configured for the signal reception in a first segment of the wide frequency bandwidth, the second antenna element is further configured for the signal reception in a second segment of the wide frequency bandwidth, the third antenna element is further configured for the signal reception in a third segment of the wide frequency bandwidth, and the fourth antenna element is further configured for the signal reception in a fourth segment of the wide frequency bandwidth.

9. 9. The wideband direction finding aperture of claim 8, wherein each of the first through fourth segments of the wide frequency bandwidth is between 3 and 5 GHz wide, and one of the first through fourth segments of the wide frequency bandwidth includes a set of frequencies where a fractional bandwidth of the set of frequencies is greater than one.

10. The wideband direction finding aperture of claim 3 , wherein the air vehicle further comprises one of a projectile, a manned or unmanned aerial vehicle, or a spacecraft.

11. 10. The wideband direction finding aperture of claim 1, wherein each antenna element of said array further comprises a depth along said z-axis of less than 0.25 inches.

12. 2. The wideband direction finding aperture of claim 1, wherein the front distance is between 1.0 and 2.0 inches, the first rear distance is between 0.7 and 1.7 inches, the second rear distance is between 1.0 and 2.0 inches, the left distance is between 0.8 and 1.8 inches, the first right distance is between 0.1 and 1.1 inches, the second right distance is between 0.1 and 1.1 inches, and the third right distance is between 1.1 and 2.1 inches.

13. 2. The wideband direction finding aperture of claim 1, wherein the first size is 2.3 to 3.3 inches along the y-axis and 0.9 to 1.9 inches along the x-axis, the second size is 0.9 to 1.9 inches along the y-axis and 0.2 to 1.2 inches along the x-axis, and the array is 4.7 to 6.7 inches along the y-axis and 3.1 to 5.1 inches along the x-axis.

14. 1. A wideband direction finding aperture including an array having at least four antenna elements, an array center point, an x-axis, a y-axis, and a z-axis, the at least four antenna elements being endfire antenna elements having a beam pattern oriented along the y-axis, the at least four antenna elements comprising: a first antenna element of a first size having a first element center point; a second antenna element of the first size having a second element center point; a third antenna element of the first size having a third element center point; a fourth antenna element of a second size having a fourth element center point, the second size being smaller than the first size; The array is configured for wide frequency bandwidth signal reception to enable direction finding of a target, the at least four antenna elements being oriented in a pattern relative to the array center point, the pattern being configured to limit at least one ambiguity associated with the signal reception, the pattern comprising: the first element center point oriented at a forward distance and a second rightward distance from the array center point; the second element center point oriented a second distance back and a first distance to the right from the array center point; the third element center point oriented at a first distance back and left from the array center point; the fourth element center point oriented at the first rear distance and a third right distance from the array center point, wherein the first rear distance is smaller than the second rear distance, the front distance is larger than the first rear distance and smaller than the second rear distance, the first right distance is smaller than the second right distance, the second right distance is smaller than the third right distance, and the third right distance is larger than the left distance, the array center point is aligned with the x-axis, the y-axis, and the z-axis, and front and rear are in opposite directions along the y-axis and left and right are in opposite directions along the x-axis. the wideband direction finding aperture; and a vehicle controller operatively coupled to each of the at least four antenna elements; a tangible non-transitory memory configured to communicate with the vehicle controller, the vehicle controller storing, in the tangible non-transitory memory, in response to execution by the vehicle controller: receiving a composite signal from the array; determining whether at least one measurement from the composite signal is an unrealistic measurement based on at least one of an azimuth angle or an elevation angle associated with the at least one measurement from the composite signal; discarding said at least one unrealistic measurement as said ambiguity; processing the combined signal to determine the azimuth and elevation angles of the target; the tangible non-transitory memory having instructions stored thereon to perform at least one vehicle function in response to the azimuth and elevation angles of the target; A system for wideband direction finding, including:

15. 15. The wideband direction finding system of claim 14, further comprising a downconverter and a digitizer configured to extract at least one feature from the composite signal, and a direction finding processor operatively coupled to each of the downconverter and the vehicle controller.

16. 15. The wideband direction finding system of claim 14, wherein the vehicle functions include one of autopilot commands, a camera function, or pointing for a semi-active radar function.

17. 15. The wideband direction finding system of claim 14, wherein the at least one measurement further includes an azimuth measurement combined with an elevation measurement, and the vehicle controller is configured to analyze each of the azimuth and elevation measurements to determine the ambiguity in the signal reception.

18. 15. The wideband direction finding system of claim 14, wherein the vehicle controller is further configured to discard a first measurement and at least one second measurement as the ambiguity during signal reception.

19. 1. A wideband direction finder for an aircraft, comprising:

1. A wideband direction finding array operatively associated with the aircraft, the array including at least four antenna elements, an array center point, an x-axis, a y-axis, and a z-axis, the at least four antenna elements being endfire antenna elements having a beam pattern oriented along the y-axis, the at least four antenna elements comprising: a first antenna element of a first size having a first element center point; a second antenna element of the first size having a second element center point; a third antenna element of the first size having a third element center point; a fourth antenna element of a second size having a fourth element center point, the second size being smaller than the first size; The array is configured for wide frequency bandwidth signal reception to enable direction finding of targets and generate a composite signal, the at least four antenna elements are non-overlapping and adjacent to at least one other antenna element, the at least four antenna elements are oriented in a pattern relative to the array center point, the pattern configured to limit at least one ambiguity associated with the signal reception, the pattern comprising: the first element center point oriented at a forward distance and a second rightward distance from the array center point; the second element center point oriented a second distance back and a first distance to the right from the array center point; the third element center point oriented at a first distance back and left from the array center point; the fourth element center point oriented at the first rear distance and a third right distance from the array center point, wherein the first rear distance is smaller than the second rear distance, the front distance is larger than the first rear distance and smaller than the second rear distance, the first right distance is smaller than the second right distance, the second right distance is smaller than the third right distance, and the third right distance is larger than the left distance, the array center point is aligned with the x-axis, the y-axis, and the z-axis, and front and rear are in opposite directions along the y-axis and left and right are in opposite directions along the x-axis. the wideband direction finding array; and a vehicle controller operatively coupled to each of the at least four antenna elements; a tangible non-transitory memory configured to communicate with the vehicle controller, the vehicle controller storing, in the tangible non-transitory memory, in response to execution by the vehicle controller: determining whether at least one measurement from the composite signal is an unrealistic measurement based on at least one of an azimuth angle or an elevation angle; Discarding the at least one unrealistic measurement as ambiguity; processing the combined signal to determine the azimuth and elevation angles of the target; the tangible non-transitory memory having instructions stored thereon to perform at least one vehicle function in response to the azimuth and elevation angles of the target; a wideband direction finder for the aircraft.

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