Patent Application
20240396228
This disclosure relates to two-dimensional (2D) phased-array radar. More specifically, the disclosure relates to, among other things, the shape and configuration of 2D phased-array antenna panels.
Unlike mechanically steerable parabolic dish radars, phased-array radars employ an antenna module that remains stationary. The module comprises a grid of fixed antenna elements, each of which are capable of transmitting and receiving a signal. Also, unlike mechanically steerable parabolic dish radar, a phased-array radar can generate multiple beams simultaneously, and steer them electronically much faster than mechanically steerable parabolic dish radar. As such, a phased-array radar can more accurately control how, when and where to direct radar scans and sense multiple objects simultaneously.
Phased-array radars are often used for detecting, identifying, tracking and cataloging objects orbiting the earth. It has been reported that there are over a million objects, some of which are classified as space debris, orbiting the earth. Many, if not most, of these objects have a diameter that is less than 10 cm. In some instances, the objects are as small as 1-2 cm in cross-section. In order to detect, identify, track and catalog orbiting objects that are smaller and smaller in size, the operating frequencies of phased-array radars employed for this purpose can get relatively high, such as frequencies in the S band (2-t14 GHz).
Phased-array radar employed for the aforementioned purpose typically have a large grid of antenna elements spaced apart from each other on a 2D antenna board or panel, where multiple 2D antenna panels are arranged together to form a larger, single 2D antenna module.
While
The spacing between antenna elements affects the gain, as a 2nd order effect, and natural width of the main beam of the radar away. Within some bounds, decreasing element spacing decreases array gain and increases the grating lobe free field of view. Increasing element spacing increases array gain while decreasing the grating lobe free field of view. Grating lobes appear away (in angle) from the main beam, and they typically do not manifest until a certain look angle is realized. For example, a particular antenna element spacing D might not result in the generation of any grating lobes when the look angle is at boresight (e.g., 0°), but it might result in the generation of grating lobes at useful or important look angles, such as look angles beyond 45° from boresight. Thus, determining antenna element spacing creates somewhat of a tradeoff between gain and field of view.
As a rule of thumb, antenna element spacing of λ/2 gives a maximum field of view, and is a special case of the equation D=λ/(1+sin θ), which gives the maximum antenna spacing for avoiding grating lobes for a field of view of θ degrees. The symbol λ represents wavelength, which is inversely proportional to frequency. From the equation, it is clear that D decreases as frequency increases (i.e., as wavelength decreases). In order to capture smaller and smaller objects, frequency can become higher and higher, and thus distance D can become smaller and smaller. For a given wavelength, the smallest resolvable target is roughly λ/5.
While distances between adjacent antenna elements become smaller and smaller, it is particularly relevant to the present disclosure that this distance be the same for all adjacent antenna elements across the entire 2D antenna module. This is true for adjacent antenna elements located on the same antenna panel as it is for adjacent antenna elements located on different but adjacent antenna panels. However, in conventional phased-array antenna module configurations, such as the phased-array antenna module configuration illustrated in
When the antenna element spacing d′ is greater than the antenna element spacing d, as described above, the power level or gain associated with the main beam is reduced and the gain associated with the side lobes, e.g., grating lobes increases. The disadvantages of this are described above. It is possible to compensate mathematically for sub-optimal side lobe structures using a “pattern synthesis” technique, which involves, among other things, applying a weighting factor to these antenna elements. However, the processing can be complex, time consuming and costly.
In view of the explanation above, a less complex yet effective solution is needed to address the problems associated with the distance d′ between the antenna elements located along the edge of one antenna panel and the antenna elements located along the edge of an adjacent antenna panel being different than (e.g., greater than) the distance d between adjacent antenna elements located on the same antenna panel.
The present disclosure addresses the aforementioned problem by providing 2D antenna panels having edges that are contoured, i.e., non-linear, as described in greater detail below. It will be understood that for performance purposes and manufacturing purposes all edges of each antenna panel may be contoured, but particularly those edges that border the edge of an adjacent antenna panel. The contoured edges result in several advantages.
According to the exemplary embodiments described herein below, at least a first advantage associated with the contoured edges is that the antenna elements located along the edge of a given antenna panel are positioned, relative to the antenna elements located along a corresponding edge of an adjacent antenna panel, such that the distance d′ between each antenna element along the edge of the given antenna panel and a corresponding antenna element along the corresponding edge of the adjacent antenna panel is equal to the distance d between antenna elements located on the same antenna panel. This, in turn, mitigates the problems described above associated with the distance d′ being different a different distance than the distance d.
According to the exemplary embodiments described herein below, a second advantage is that the contoured edges provide sufficient area on the underside of the antenna panel and below each antenna element, particularly those antenna elements located along the antenna panel edges, to accommodate the radio frequency (RF) circuitry associated with each antenna element. In conventional configurations, when the antenna element spacing d′ is equal to the antenna element spacing d, the area on the underside of the antenna panel and, more particularly, under the antenna elements located along the edges of the antenna panel, is limited and thus unable to accommodate all of the necessary RF circuitry. Thus, the RF circuitry may need to be located elsewhere and connected to the antenna elements on the antenna panel via cabling which increases manufacturing costs and introduces noise, phase errors and signal losses to the transmit and receive signals that are fed to and received from the antenna elements. In contrast, according to the exemplary embodiments described herein, the RF circuitry associated with each antenna element on a given antenna panel may be located on and integrated into the underside of the antenna panel and connected to the corresponding antenna element through a multilayer board design that requires no cabling. Thus, the exemplary embodiments described herein below also reduce manufacturing costs and achieve higher performance by minimizing the aforementioned noise and signal losses introduced in conventional designs.
A first aspect of the present disclosure, in accordance with exemplary and other embodiments, is directed to a two-dimensional phased-array radar module. The phased-array radar module comprises a plurality of antenna panels. Each of the plurality of antenna panels comprises a plurality of antenna elements, wherein a first distance between each of the plurality of antenna elements, on each of the plurality of antenna panels, and all adjacent antenna elements on the same antenna panel is the same distance. Each of the plurality of antenna panels also comprises a contoured edge that is configured such that the positioning of the contoured edge of a first one of the plurality of antenna panels adjacent to the contoured edge of a second one of the plurality of antenna panels causes each antenna element along the contoured edge of the first one of the plurality of antenna panels to be separated by a second distance from a corresponding antenna element along the adjacent edge of the second one of the plurality of antenna panels, wherein the second distance equals the first distance.
A second aspect of the present disclosure, in accordance with exemplary and other embodiments, is directed to a two-dimensional (2D) antenna panel configured to be combined with a plurality of like 2D antenna panels to form a 2D phased-array antenna module. The 2D antenna panel comprises a plurality of antenna elements, wherein a first distance between each of the plurality of antenna elements and all adjacent antenna elements is the same distance. The 2D antenna panel also comprises a plurality of contoured edges configured such that a positioning of each of the plurality of contoured edges adjacent to a contoured edge of another one of the plurality of like 2D antenna panels causes each antenna element along each of the plurality of contoured edges of the 2D antenna panel to be separated by a second distance from a corresponding antenna element along the adjacent edge of the another one of the plurality of like 2D antenna panels, wherein the second distance equals the first distance.
Generally, this disclosure describes a two-dimensional (2D) phased-array radar module and, more specifically, the 2D antenna panels that make up the radar module. As those skilled in the art of phased-array radar will appreciate, the configurations described herein are exemplary, and that other embodiments are possible and within the intended scope of the disclosure as described herein and claimed. The disclosure is now described in greater detail with references to the figures.
Various terminology as used herein can imply direct or indirect, full or partial, temporary or permanent, action or inaction. For example, when an element or component is referred to as being “on,” “connected” or “coupled” to another element or component, the element or component may be directly on, connected or coupled to the other element or component, with or without intervening elements or components, including indirect or direct variants. In contrast, when an element or component is referred to as being “directly connected,” “directly coupled,” or “directly connected to” another element or component, then there are no intervening elements or components present.
Various terminology as used herein includes various singular forms preceded by “a,” “an” and “the,” which are intended to include various plural forms as well, unless specific context clearly indicates otherwise. Other terms such as “comprises,” “comprising,” “includes” and “including,” and variations thereof, specify a presence of certain features, elements, components, and the like, but do not preclude the presence or addition of one or more other features, elements, components or the like.
As used herein, the term “or” is intended to mean an inclusive “or” rather than an exclusive “or.” That is, unless specified otherwise, or clear from context, “X employs A or B” is intended to mean any of a set of natural inclusive permutations. That is, if X employs A; X employs B; or X employs both A and B, then “X employs A or B” is satisfied under any of the foregoing instances.
Furthermore, relative terms, such as, for example, “below,” “lower,” “under,” “bottom,” “above,” “upper,” and “top” may be used herein to describe one element or component's relationship to another element or component, particularly as presented in the set of accompanying, illustrative drawings. However, such relative terms are intended to encompass different orientations and relative positions in addition to those depicted and described. For example, if a component is described and illustrated as being on an “under” side of something, such as an antenna panel, that component may be described and illustrated as being on an “upper” side when the antenna panel is turned over. Therefore, as stated, various relative terms, such as those mentioned above, as well as others, may encompass different orientations and positions, unless clearly described otherwise.
Terms such as “about” or “substantially” refers to a possible variation from a nominal value/term as those skilled in the art would understand it. Such variation is always included in any given value/term provided herein, whether or not such variation is specifically referred thereto.
Although the terms first, second, etc. can be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not necessarily be limited by such terms, for example, to a specific sequence or order. These terms are used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer, or section discussed below could be termed a second element, component, region, layer, or section without departing from various teachings of this disclosure.
Features described with respect to certain embodiments can be combined and sub-combined in and/or with various other embodiments. Also, different aspects and/or elements of embodiments, as disclosed herein, can be combined and sub-combined in a similar manner as well. Further, some embodiments, whether individually and/or collectively, can be components of a larger system, wherein other procedures can take precedence over and/or otherwise modify their application. Additionally, a number of steps can be required before, after, and/or concurrently with embodiments, as disclosed herein. Note that any and/or all methods and/or processes, at least as disclosed herein, can be at least partially performed via at least one entity in any manner.
As shown in each of
Of particular importance to the exemplary embodiments described herein is the contoured edges of the plurality of antenna panels 310. The contoured edges are more easily visible in the enlarge illustration of
Other contours are conceivable and within the scope of some embodiments. That is, any contoured antenna panel edging that achieves the intended benefits described in detail herein below would fall within the scope of some embodiments. Thus, a contoured edge with a sawtooth appearance or a contoured edge with a square wave appearance may fall within the scope of some embodiments. However, the sinewave-shaped edge can make it easier to integrate electronics with the panel and combine panels.
The contoured edges allow for an edge around antenna elements arranged in hexagonal or triangular patterns. This pattern allows for more better performing, e.g., more accurate, radar over a square-grid pattern. Having the contoured edges allows for generally rectangular or square panels, but for the edges having a contour. Such an arrangement may case the manufacturing process and allow for larger panels, which improves quality and reduces cost. It is also simpler to manufacture panels in this shape. A straight line bisecting the panel would result in a non-optimal hexagonal- or parallelogram-shaped configuration. A straight line could be drawn through the panel(s), but that would result in a suboptimal diamond shape. Therefore, the contoured edges are important for maintaining a beneficial shape.
As summarized above, by contouring the edges as illustrated, the antenna elements located along the edge of a given antenna panel and the antenna elements located along a corresponding edge of an adjacent antenna panel may be positioned relative to each other, for example, closer to each other, such that the distance d′ between the antenna elements of the given antenna panel and the antenna elements of the adjacent antenna panel is equal to the distance d between adjacent antenna elements located on the same antenna panel.
The contoured edges described above provide a number of significant advantages over conventional configurations. The first advantage is directly related to the relative positioning of the antenna elements such that the distance d′ between each of the antenna elements along the edge of a given antenna panel and the corresponding antenna elements along the edge of an adjacent antenna panel is the same distance as the distance d between adjacent antenna elements on the same antenna panel. When the distances d′ and d, as defined above, are the same distance, the received radar signals can be processed more quickly, more efficiently and more accurately. In contrast, when the distance d′ does not equal the distance d, the power level or gain associated with the main beam and any side lobes will vary. When, more specifically, the distance d′ is greater than the distance d, the power level or gain associated with the main beam is reduced and the gain associated with any side lobes is increased. As those skilled in the art will appreciate, reducing the power level or gain of the main beam can reduce the level of the received radar signals, making it more difficult to detect, identify and track an intended object. On the other hand, increasing the power level of any side lobes that are generated could result in unwanted radar signals at certain desirable look angles. To correct the undesirable effects associated with d′ and d not being the same distance, it may be possible to compensate by employing mathematically complex processing techniques, as mentioned above, which increase processing time, increase processing complexity and offer less accurate results. In short, a consistent array shape results in better beamforming and therefore stronger received signals/higher SNR. The contoured edges as describe herein eliminate or at least minimize the need to employ such complex techniques.
A second advantage of the contoured edges described above relates to the ability to integrate the RF circuitry associated with each antenna element into the underside of a multilayer antenna panel. As explained above, the need to detect, identify and track smaller and smaller objects has resulted in the utilization of radar signals having smaller wavelengths, which translates into a decrease in distance D between antenna elements on each of the antenna panels, according to the general equation D=λ/(1+sin θ). As D decreases, that is, as the distance between antenna elements decreases, and more antenna elements are placed on a given antenna panel, there is less room available on the antenna panel for the RF circuitry needed to condition the transmit and receive signals. Of course, one alternative is to move some or all of the RF circuitry off the antenna panel; however, this is not an ideal solution. Doing so may drive up manufacturing costs and it would most result in signal strength losses and phase errors due to the fact that the transmit and receive signals would have to be routed via cabling to and from the antenna elements. Thus, being able to accommodate the RF circuitry for all of the antenna elements into the antenna panel is a significant advantage.
In the example of
It should be noted that the antenna panel 600 has a border 650. The purpose of the border is to create a continuous ground plane to shield the RF circuitry on the underside of the antenna panel from the RF emissions being transmitted and received by the antenna elements on the top or upper side of the antenna panel. The border can comprise any material suitable to serve this purpose. I can also be important for the operation of the antenna array for all ground planes to have the same potential panel-to-panel.
A subframe can be included to connect the various panels, and having a generally square or rectangularly shaped panel can simplify the subframe design, and improves the ability to maintain a continuous ground plane. The subframe can allow borders 650 to electrically couple, thereby forming a continuous ground plane to shield the sensitive circuitry.
It is important to reiterate that the contoured edges of the antenna panels make it possible to integrate the RF circuitry for each antenna element, and the corporate-feed networks into the antenna panel. This is particularly the case for the RF circuitry associated with the antenna elements located along the edges of each antenna panel. As can be seen in
In the exemplary embodiment illustrated in
As is clear from
Layers L3 and L5 instantiate the corporate-feed networks. As explained, these layers distribute the transmit signal and combine the receive signals to and from the plurality of antenna elements, e.g., all 64 antenna elements. This is accomplished using impedance-matched stripline connections buried between the aforementioned alternating ground plane layers. Incorporating the corporate-feed networks into the antenna panel, in and of itself, provides substantial cost savings from a manufacturing perspective. It also reduces design complexity compared to a design that externally combines the antenna elements using, e.g., a separate 64-way combiner/divider module and associated coaxial cabling. Using external cabling to combine antenna elements could also compromise the phase stability of the system over temperature variations, and thus result in phase errors affecting beam formation and pointing accuracy. External cabling could have other problems, including substantially increased cost, PCB material may suffer phase issues over temperature. It is also common to get phase-matched cables, whereas PCB traces can be length-matched.
As stated, the multilayer board design for the antenna panels is important for several reasons. It keeps the per-element costs low enough to make the design realizable and still achieve the highest performance by eliminating cabling running from the antenna panel to functionally similar elements located off the antenna panel. Furthermore, the design is more compact and allows the configuration to the λ/2, requirement described above, as wavelengths get smaller (i.e., frequencies get higher), and the distance between antenna elements get smaller.
Various corresponding structures, materials, acts, and equivalents of any means or step plus function elements in various claims below are intended to include any such structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. Various embodiments were chosen and described in order to best explain various principles of this disclosure and various practical applications thereof, and to enable others of ordinary skill in a pertinent art to understand this disclosure for various embodiments with various modifications as are suited to a particular use contemplated.
This detailed description above has been presented for various purposes of illustration and description, but is not intended to be fully exhaustive and/or limited to this disclosure in various forms disclosed. Many modifications and variations in techniques and structures will be apparent to those of ordinary skill in an art without departing from a scope and spirit of this disclosure as set forth in various claims that follow. Accordingly, such modifications and variations are contemplated as being a part of this disclosure. A scope of this disclosure is defined by various claims, which include known equivalents and unforeseeable equivalents at a time of filing of this disclosure.
| Number | Date | Country | |
|---|---|---|---|
| 63464739 | May 2023 | US |
