The current application relates to phased array antennas for use in communication systems and in particular to arrangements and tiling of sub-array groupings of array elements.
Phase array antenna can be used in a variety of different wireless communication networks, and they can be used to enable steering of the transmission or reception in both the azimuth and elevation planes. Steering transmission and reception allows for an antenna array to direct the transmission or reception resources towards a particular location, which can increase the effective connection resources available to serve a given node. In mobile networks, that is networks designed to provide service to mobile devices, there is increased interest in beam steering as it allows for better concentration of connectivity resources to the locations that need them. A relatively large array is required in order to achieve desirable directivity. In conventional phased array design there is one phase shifter, delay line and/or amplitude control per array element. This increases both the cost and complexity of manufacture of the array. In order to reduce system complexity there is a need to reduce the amount of control circuitry. Sub-array antenna designs are used to group a small amount of array elements together and use only one phase shifter or delay line to drive the group of array elements. However using sub-arrays can result in grating lobes as well as reduce the array's steerability.
It is desirable to have an additional, alternative and/or improved phased array antenna design for communication systems.
In accordance with the present disclosure there is provided phased array antenna comprising: a plurality of rectangular sub-arrays of individual array elements, the plurality of rectangular sub-arrays tiled to reduce periodicity of phase centers of the plurality of sub-arrays.
In a further embodiment of the phased array antenna, the array elements in respective rectangular sub-arrays are connected to a common phase shifter.
In a further embodiment of the phased array antenna, each of the plurality of rectangular sub-arrays have respective major axis and minor axis.
In a further embodiment of the phased array antenna, a subset of the plurality of rectangular sub-arrays are tiled with major axes arranged perpendicular to the major axes of other rectangular sub-arrays.
In a further embodiment of the phased array antenna, the rectangular sub-arrays are tiled to provide a greater number of phase center locations along an axis of the phased array antenna.
In a further embodiment of the phased array antenna, the phase centers of the rectangular sub-arrays are located within respective rectangular sub-arrays.
In a further embodiment of the phased array antenna, each of the rectangular sub-arrays comprise 8 individual array elements.
In a further embodiment of the phased array antenna, the rectangular sub-arrays comprise 4×2 rectangles of individual array elements.
In a further embodiment of the phased array antenna, the rectangular sub-arrays further comprise 8×1 rectangles of individual array elements.
In a further embodiment of the phased array antenna, there is a greater number of 4×2 rectangular sub-arrays than 8×1 rectangular sub-arrays.
In a further embodiment of the phased array antenna, each sub-array is associated with an amplitude weighting.
In a further embodiment of the phased array antenna, the sub-arrays are assigned the amplitude weightings to provide an approximation of a column weighting.
In a further embodiment of the phased array antenna, two or more individual array elements within respective rectangular sub-arrays are associated with different amplitude weightings.
In a further embodiment of the phased array antenna, the amplitude weightings are Chebyshev weightings.
In a further embodiment of the phased array antenna, a frequency used by the phase array antenna is in a range of about 71-86 GHz.
In a further embodiment of the phased array antenna, spacing between individual antenna elements is approximately equal to λ0/2, where λ0 is a wavelength in free space at a particular operating frequency of the phase array antenna.
In a further embodiment of the phased array antenna, there are 1024 individual antenna elements.
In a further embodiment of the phased array antenna, the array elements in respective rectangular sub-arrays are connected to a common delay line.
In a further embodiment of the phased array antenna, the individual array elements, across the plurality of rectangular sub-arrays, are arranged in a regular grid pattern.
In a further embodiment of the phased array antenna, the each sub-array in the phased array antenna is a rectangular sub-array.
In accordance with the present disclosure there is further provided a phased array antenna comprising: a plurality phased array antenna components each of the phased array antenna components comprising a plurality of rectangular sub-arrays of individual array elements, the plurality of rectangular sub-arrays tiled to reduce periodicity of phase centers of the plurality of sub-arrays.
Embodiments are described herein with reference to the appended drawings, in which:
Although phased arrays can be used in many different network implementations, including in third and fourth generation (3G/4G) mobile networks, such as those supporting the Long Term Evolution (LTE) networking standards defined by the Third Generation Partnership Project (3GPP), the following discussion will be directed to the application of phase array in next generation wireless networks, such as fifth generation wireless networks (5G). This should not be viewed as limiting the scope of applicability of phase array antennas.
In order to provide the performance desired for next generation wireless networks such as 5G, networks may include phased array antennas in transmitters and receivers to allow transmission beams to be steered and to allow receivers to be directed in both an azimuth plane as well as an elevation plane. Although the specific field of view (FOV) that can be scanned by the phased array will vary depending upon the particular requirements, generally, the design objective is to allow a main beam to be steered over +/−30° in both the azimuth and elevation plane. The antenna design described further below utilizes a plurality of rectangular sub-arrays of individual array elements. It will be understood that each sub-array has a phase center. The sub-arrays are arranged to reduce periodicity of the phase center locations. Rather than using a regular grid tiling of the rectangular sub-arrays, which results in highly periodic phase center locations, the current antenna designs introduce randomness, or pseudo-randomness, into the tiling of the rectangular sub-arrays. The random tiling of the regular shaped sub-arrays introduces aperiodicity into the phase center locations. The arrangements described allow a reduction in the number of control circuits required because each sub-array is served by a single control circuit rather than each individual array element requiring its own control circuit. The reduction in the control circuitry as well as the relatively simple sub-array tiling pattern may provide a cost reduction, simplify a design process and/or simplify the manufacture of the antenna.
Although an antenna array, such as antenna array 200, with phase shifters for each individual array element can provide desired performance, the numerous phase shifters and associated circuitry for controlling each array element adds additional cost and may complicate the manufacturability of the antenna. It is possible to group together a number of array elements, such as rows or columns of the array elements, and provide a single phase shifter or delay line for each grouping. While such a technique reduces the number of phase shifters or delay lines required, it also impacts the performance of the antenna array. Grouping together the array elements may decrease FOV of the array. Additionally, the grouping of the array elements may also increase side lobe levels and creating one or more grating lobes when steered.
In order to reduce the number of control circuits required for a phased array, individual array elements can be grouped together into to sub-arrays and the sub-arrays driven as if it were an array element. For example, if the phased array uses sub-arrays that group together 8 individual array elements, the number of control circuits will be reduced by ⅞. The sub-arrays each have an associated phase center, and for a regular tiling of rectangular sub-arrays with inter-element spacing of λ0/2, the distance between the locations of two phase centers will be greater than λ0 at a particular operating frequency. The relatively large distance between the phase centers of the sub-arrays will result in grating lobes appearing during steering of the radiated beam. Although it is possible to use complex design and manufacturing techniques, such as random tiling of irregular polyomino-shaped sub-arrays, to reduce the grating lobes produced by the sub-arrays, such techniques may be difficult to design and manufacture which in turn may be costly in both money and time. An irregular polyomino shape is a non-rectangular shape formed by joining three or more equal squares along edges. As described further herein, the reduction in the number of control circuits used in a phased array is due to the use of sub-arrays. While the use of irregular polyomino based tilings achieves a reduction in the amount of control circuitry, it offsets this with a corresponding increase in design and manufacturing complexity. In the following an array that makes use of rectangular arrays is described that has an equivalent reduction in the number of control circuits, allows for a simpler feed structure due to the regular shape of the sub-arrays, and maintains acceptable side lobe levels by introducing randomness into the tiling pattern which results in a reduction of the periodicity of the phase centers of the sub-arrays. It will be understood by those skilled in the art that this could also be described as making use of a sub-array tiling that increases the aperiodicity of the phase centers of the sub-arrays.
As depicted in
The sub-arrays 506 are depicted as each grouping together 8 individual array elements 504; however, other numbers of array elements may be grouped together into sub-arrays. The greater the number of array elements grouped together in a single sub-array, the fewer sub-arrays will be required to cover the entire grid 502 of the array elements. Each sub-array is driven by a respective control circuit and as such, grouping more array elements together in a single sub-array result in fewer control circuits. However, the larger sub-arrays will result in fewer phase centers and greater distances between them, possibly resulting in inferior performance with respect to side lobe levels as well as steerability of the array. Accordingly, the number of array elements grouped together in an individual sub-array may be considered a trade-off between performance and reduction in control circuit complexity. In the phased array antenna embodiments described herein, a grouping together of 8 array elements per sub-array are described which may provide an acceptable balance between performance and circuit complexity. However, if a greater reduction of circuit complexity is desirable, larger sub-arrays may be used. Similarly, if greater performance is desirable with respect to side lobe levels and/or steerability, smaller sub-arrays may be used.
Each of the plurality of sub-arrays 506 has an associated phase center 516. The phase centers 516 are depicted as being generally located at the geometric center of the sub-arrays. However, as will be understood by those skilled in the art, the particular location of a phase center of an individual sub-array need not be located in the geometric center of the sub-array if the array elements and the sub-array are designed to move the phase center. While the particular location of the phase centers may be varied, a major factor in the location is the geometry of the sub-array. Accordingly, for clarity of the description, the phase centers are assumed to be located at the geometric centers of the rectangular sub-arrays.
The sub-arrays 506 are tiled on the grid 502 of the array elements such that there are no voids in the tiling pattern. Each of the array elements 504 are a part of a single sub-array, and are fed and controlled by the feed and control circuitry associated with the sub-array. The sub-arrays 506 are arranged in such a manner as to reduce a periodicity in the location of the phase centers. As depicted in
The sub-arrays 506 are tiled in order to increase an aperiodicity of the phase center locations 516. Such an increase in the aperiodicity in phase center location may decreases a distance between some phase centers and provides improved side lobe level performance. That is, by increasing the aperiodicity of the phase centers, grating lobes may be reduced. Further, the increased aperiodicity may also increase a vertical and horizontal density of phase centers. As depicted in FIG. 5, there are more phase center locations having distinct horizontal locations than if the array element grid were tiled with rectangular tiles all arranged in the same direction. As depicted, the 32 sub-arrays 504 are arranged so that each of the phase centers 516 are arranged along one of 14 vertical axes 518. This is a large increase in comparison to the result from regularly arranged tilings of vertically arranged sub-arrays of 4×2 array elements which would align the phase centers on 8 vertical axes. Similarly, the number of horizontal axes 520 along which the phase centers are arranged is increased compared to a regularly arranged tiling of vertically arranged sub-arrays. In particular, there are 13 horizontal axes 520 along which the phase centers 516 are arranged. The increased density of phase center locations along the vertical and horizontal axes may provide improved directionality of the phased array.
The phased array antenna 500 depicted in
The phased array antenna depicted in
Side lobe levels may be adjusted to improve antenna performance. One such technique is to use amplitude tapering based on Chebyshev weightings to further smooth the side lobe levels so that the maximum side lobe level will be reduced. Such amplitude tapering improves side lobe levels at the expense of the antenna's efficiency. The Chebyshev weightings may be applied at the sub-array level.
The above phased array antenna calculations have assumed that the phase shifters of each sub-array operate at the signal frequency, which in the above description is 86 GHz. However, in practice an antenna may need to operate at a range of frequencies, and the operation of the phase shifter may not cover the entire operating bandwidth. Such real-world limitations may result in different responses of the phased array antenna at the different frequencies.
The above description provides various specific implementations for a phased array antenna. The specific embodiments have been simulated for reception and transmission in the approximately 71 GHz-86 GHz frequency range It will be appreciated that the same technique of tiling rectangular sub-array groupings of individual array elements may be applied to phased array for communication networks operated at other frequency ranges. Further, although specific tiling patterns are depicted, it is possible to provide alternate tiling patterns of rectangular sub-arrays that reduce the periodicity of the phase centers while still providing a complete tiling pattern of the sub-arrays that completely covers all of the array elements in the grid without overlap.
The present disclosure provided, for the purposes of explanation, numerous specific embodiments, implementations, examples and details in order to provide a thorough understanding of the invention. It is apparent, however, that the embodiments may be practiced without all of the specific details or with an equivalent arrangement. In other instances, some well-known structures and devices are shown in block diagram form, or omitted, in order to avoid unnecessarily obscuring the embodiments of the invention. The description should in no way be limited to the illustrative implementations, drawings, and techniques illustrated, including the exemplary designs and implementations illustrated and described herein, but may be modified within the scope of the appended claims along with their full scope of equivalents.
While several embodiments have been provided in the present disclosure, it should be understood that the disclosed systems and components might be embodied in many other specific forms without departing from the spirit or scope of the present disclosure. The present examples are to be considered as illustrative and not restrictive, and the intention is not to be limited to the details given herein. For example, the various elements or components may be combined or integrated in another system or certain features may be omitted, or not implemented.