Patent Grant
7053832
Broadband antennas, in general, are known. To a lesser extent, multiband antennas are known, in general. Typically, an array formed of broad band or multiband antennas cannot provide high gain efficiently, i.e., in terms of the volume consumed by the array itself.
The need for increased wireless communication system capacity continues to grow at a significant rate. To satisfy this need, some wireless service providers hope to use the higher frequency PCS band to provide the additional capacity. Hence, new antennas must be added to existing antenna towers or new antenna towers erected.
Unfortunately, most communities resist placing additional antennas on existing towers and/or erecting new antenna towers.
The invention, in part, is a recognition that an antenna for an additional wireless communication band can, in effect, be added to a tower (whose antenna quota has already been filled) by replacing a single band antenna with a multiband, e.g., dual-band antenna. This is especially advantageous if the ratios of the gain to the volume-consumed for the multiband antenna are at least comparable to the ratio of the antenna being replaced.
The invention, also in part, is a recognition that a multiband antenna can achieve ratios of gain to volume-consumed that are comparable to single band antennas if the radiating elements serving the different bands are nestled together, albeit in different array planes, and can achieve good performance if the radiating elements are arranged to so as to not induce cross-band interference.
Accordingly, an embodiment of the invention provides a multiple band antenna that includes a first radiating element that radiates at a first band, at least one second radiating element that radiates at a second band, and a frame to hold the radiating elements. The frame disposes the first and second radiating elements in different planes. Consequently, cross-band interference may be substantially avoided. The first band, e.g., may be lower than the second band.
Another embodiment of the invention provides an antenna arrangement that includes an array of antenna structures. Each antenna structure includes the first radiating element, the one or more second radiating elements and the frame to hold the radiating elements.
Another embodiment of the invention provides a multiple band array antenna that includes a first array of radiating elements in a first plane and a second array of radiating elements in a second plane. The first plane overlays the second plane. As a result, individual radiating elements in the first array are substantially interspersed with individual radiating elements in the second array. But the first array and the second array are arranged so that individual radiating elements in the first array substantially do not overlap individual radiating elements in the second array.
The invention may be embodied in other forms without departing from its spirit and essential characteristics. The described embodiments are to be considered only non-limiting examples of the invention. The scope of the invention is to be measured by the appended claims. All changes which come within the meaning and equivalency of the claims are to be embraced within their scope.
The accompanying drawings are: intended to depict example embodiments of the invention and should not be interpreted to limit the scope thereof; and not to be considered as drawn to scale unless explicitly noted.
The cross element 101 includes a right arm 102 and a left arm 104 that together define a horizontal span 106, plus a top arm 108 and a bottom arm 110 that together define a vertical span 112. The cross element 101 is analogous to a two-dimensional Cartesian plane in which the right arm 102 corresponds to the positive X-axis while the top arm 108 corresponds to the positive Y-axis. As such, the cross element 101 can be understood to define first through fourth quadrants 121, 122, 123, and 124, respectively. The cross 101 is located in a first plane and the elements 131–134 are located in a different second plane, spaced sufficiently far apart to significantly reduce interference.
The bottom conductive layer 156 corresponds to the patterned conductive runs 146 in
The square radiating elements 131–134 are positioned in a plane lying a predetermined distance above the plane of the top conductive layer 152 of the PCB 150. The plane of the cross element 101 is positioned a second predetermined distance, greater than the first predetermined distance, above the layer 152 of the PCB 150. Alternatively, the cross element 101 could be located closer to the PCB 150 than the square elements 131–134. In general, the distance of a radiating element to the feeder network is determined according to the bandwidth over which the radiating element radiates.
In operation, the electromagnetic signals provided to the feed inputs P1–P10 of the feeder network 140 cause the feeder network 140 to excite the slot radiators 144. The electromagnetic radiation from the slot radiators 144 couples electromagnetically with the structure 100 aligned over it such that the structure 100 radiates electromagnetically. There are no galvanic couplings between the feeding network and the associated cross-shaped radiating elements and squared-shaped radiating elements. The electromagnetic radiation of the structure 100 produces a beam shape that is highly amenable to beam forming and beam steering. In addition, the beam formed by the structure 100 exhibits a very good efficiency ratio both in terms of input to output power, and output power to volume consumed by the structure.
As is well known, once the shape of the radiating arrangement is determined, e.g., the structure 100, an ordinary (or lesser) amount of experimentation is required to determine an appropriate feeder network. An example of commercially available software that can determine an appropriate corresponding feeder network (and also model appropriate dimensions and spacing of a radiating arrangement) is the ADVANCED DESIGN SYSTEM brand of modeling software made available by AGILENT TECHNOLOGIES INC.
The structure 100 of
The cross element can be a low frequency radiator while the small squares are high frequency radiators. Generally, the frequency of the cross, FC, is about ½ the frequency of the squares, FS, i.e., FC≈½ FS.
Alternatively, elements 131 and 132 can be designed and energized to radiate at a second frequency, f2, (relative to the first frequency, f1, of the element 110). And elements 133 and 134 can be designed and energized to radiate at a third frequency, f3. This produces a tri-band structure. The relative relationships can be f1<f2 and f1<f3.
More generally in the alternative, the elements 131–134 can be designed and energized to each radiate at a different frequency. It is noted that incorporating such a five-band structure into an array can be more difficult to implement than the dual-band structure or the tri-band structure because it is more difficult for elements energized with the same frequency to be adjacent. In other words, it is more difficult to achieve acceptable C2C distances between elements energized with the same frequency signals for an array of five-band structures.
The cross-shaped radiating element can radiate or receive two polarizations. The first one of the polarizations is parallel to a first one of the arms of the cross. The second one of the polarizations is parallel to a second one of the arms of the cross.
The polarization of the electromagnetic radiation from or received by the squares can be +/−45°, i.e., parallel to a diagonal line that bisects the squares that are in opposite quadrants of the cross element to which the squares are aligned. In other words, the line bisecting the first and third quadrant represents the line to which a first polarization of the squares is parallel. The line bisecting the second and fourth quadrants represents a line to which the second polarization of the squares is parallel. Alternatively, the feeder network can be adapted to horizontally and vertically polarize radiation from the squares instead of inducing +/−45° polarization.
Such polarization permits a single antenna to act as multiple antennas, which, e.g., can be beneficial in terms of diversity. For example, where the cross-shaped radiating element exhibits dual polarization and the squares also exhibit dual polarization, such nestled radiating elements act as four separate antennas.
To maintain the cross element 201 in a plane above and parallel to the plane of the square radiating elements 231–234, a frame 250 is provided. The frame 250 has legs 252 that are substantially perpendicular to the planes of the cross element 201 and the square radiating element 231–234.
In addition, the frame 350 has a cross-shaped receptacle 356 that is rimmed so that the cross element 201 fits snugly into the recess. Similarly, the frame 350 has four rimmed receptacles 358 arranged so that the square radiating elements 331–334 fit snugly in the recesses, respectively. The radiating elements can be held in the receptacles by, e.g., a friction fit.
The frame 350 includes legs 354 that establish the predetermined spacing between the PCB, e.g., 150, and the plane of the square radiating elements 331. The legs 352 establish the proper spacing between the plane of the cross element 201 and the square radiating elements 331–334.
Both the frames 250 and 350 should be made of non-conductive material, e.g., plastic. Such a plastic frame can be injection molded. An advantage of the angled legs 352 of the frame 350 relative to the perpendicular legs 252 of the frame 250 is that the angled legs 352 can be easier to form from the perspective of doing the injection molding.
The arrangement of
The structure 400A includes a radiating element 431A and a radiating element 433B that are aligned with the first and fourth quadrants of the cross element 401A. Similarly, the structure 400B includes rectangular, e.g., square, radiating elements 432B and 433B that are aligned with the second and third quadrants of the cross element 401B.
The radiating crosses 401A and 401B are located in substantially the same plane. The radiating squares 431A, 434A, 432B and 433B are located in substantially the same plane, which is below the plane of the radiating crosses 401A and 401B. The radiating crosses 401A and 401B are elevated above the PCB 158 by non-conductive posts 446. The square radiating elements 431A, 434A, 432B and 433B are elevated above the PCB 158 by non-conductive posts 448. The use of such non-conductive posts is an alternative to the plastic frames 250 and 350. In a situation in which ease of installation of the radiating elements and minimization of the cost of the spacing materials is important, the non-conductive frame approach, e.g., 250 or 350, would be preferable to the use of the posts 446 and 448.
The radiating arrangement of
The building block of
An example of sizes and spacing for the building block depicted in
Continuing the example, the center-to-center (“C2C”) distance between the square 431A and the square 432B, as well as between the square 434A and square 433B can be 78 mm, which corresponds to 0.5λ in the PCS band. The C2C distance between the squares 431A and 434A, as well as between the squares 432B and 433B, is 105 mm, which corresponds to 0.67λ in the PCS band. The squares 431A, 434A, 432B and 433B have sides that are 55 mm, which corresponds to 0.35λ in the PCS band.
Further continuing the example, each of the spans (namely from the left arm to the right arm, and from the top arm to the bottom arm) of the crosses 401A and 401B is 130 mm. At its most narrow part, an arm of a cross is 13 mm wide. At its widest part, i.e., at the ends of the arms, the arms are 32 mm wide. From the center of the crosses, the arms widen out at an angle of approximately 30°. The C2C distance between the crosses 41A and 41B is 190 mm which corresponds to 0.54λ in the cellular band.
Further continuing the example, from the center of the upper squares 431A and 432B to the top wall 436 is 64 mm, which corresponds to 0.41λ in the PCS band. From the center of each of the squares 431A, 434A, 432B and 433B to the center wall is 39 mm, which corresponds to 0.25λ in the PCS band. The center of the lower squares 434A and 433B to the bottom wall 438 is correspondingly the same, namely 64 mm, which corresponds to 0.41λ in the PCS band. From the center of the squares 431A and 434A to the left wall 442, and from the center of the squares 432B and 433B to the right wall 440, is 150 mm, which corresponds to 0.96λ in the cellular band. From the top wall 436 to the bottom wall 438 is 216 mm.
Further continuing the example, the left and right walls 442 and 440 are 4.72 inches in width, i.e., from the side edge touching the PCB to the opposite side edge. The height of the center wall 444 is 55 mm, which corresponds to 0.35λ in the PCS band. The left and right walls 442 and 440 are inclined at an angle of 68° with respect to the portion of the plane of the PCB 158 that is on the opposite of the walls relative to where the radiating elements are located. The width of the top wall 436 and the bottom wall 438 (again, partially shown in
The plane of the PCB 158 can be, e.g., vertical. Alternatively, the plane of the PCB 158 can be inclined to about 5° relative to vertical in order to achieve mechanical down lift.
As to the building block 600, optional square radiating elements can be aligned with the second and third quadrants of the first cross 601A and the first and fourth quadrants of the second cross 601B. If a radiating element is added to the second quadrant of the first cross 601A, then a corresponding radiating element should be added to the first quadrant of the cross 601B. Similarly, if a radiating element is added to the third quadrant of the cross 601A, then a radiating element should be added to the fourth quadrant of the second cross 601B, etc.
In general, for the structures of
In the array 864, a row corresponds to a building block 800. For example, the array 864 is 9×1, i.e., nine rows by one column.
Also present in the array 864 are unpopulated crosses 860. An unpopulated cross substantially has no radiating elements aligned with its quadrants. Each building block 800 has two unpopulated crosses 860 associated with it. The first such unpopulated cross sits adjacent to the element 831B along a line that bisects the radiating elements 831B and 833C. Similarly, the second radiating element sits adjacent to the radiating element 832A along a line that bisects the elements 832A and 834A. The building block 800 and its associated unpopulated crosses 860 can be considered a macro building block 862. There are nine macro building blocks 862 depicted in the array 864.
The array 916 has nearly the same arrangement of unpopulated crosses as the array 864, except that an additional two unpopulated 860 are included at the bottom of the array 916. In addition, each pair of horizontally-adjacent crosses 860 has a populated cross 901C located between them. The cross 901C has the same rotational orientation as the crosses 901A and 901B. Radiating elements 905C, 906C, 907C and 908C are aligned with the first through fourth quadrants of the cross 901C. A macro-block 912 in
Beam formation and steering for each of the arrays 864, 916 and 1038 for the higher frequency of the square radiating element is controlled by keeping the frequency and amplitude the same but varying the phase of the signals fed to the respective square radiating elements. For example, in
The array 916 has square radiating elements whose C2C distance is greater than, e.g., the square elements of the array 864. Hence, the array 916 has a reduced ability to steer relative to the array 864.
Other embodiments of an array antenna according to invention are depicted in
The cross shapes of
As an alternative configuration for the higher frequency radiating elements, e.g., 131–134, instead of squares, the radiating elements could be crosses, e.g., rectangular crosses or bow tie crosses.
Other shapes for the lower frequency element could be used, e.g., a three-pointed star (where a cross corresponds to a four-pointed star), a five or more pointed star, a counter clockwise or clockwise swastika, etc.
As an alternative to the five layer PCB of
The invention may be embodied in other forms without departing from its spirit and essential characteristics. The described embodiments are to be considered only non-limiting examples of the invention. The scope of the invention is to be measured by the appended claims. All changes which come within the meaning and equivalency of the claims are to be embraced within their scope.
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| Number | Date | Country | |
|---|---|---|---|
| 20040004579 A1 | Jan 2004 | US |
