CA2540216A1 - Tri-polar antenna array element - Google Patents
Tri-polar antenna array element Download PDFInfo
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- CA2540216A1 CA2540216A1 CA 2540216 CA2540216A CA2540216A1 CA 2540216 A1 CA2540216 A1 CA 2540216A1 CA 2540216 CA2540216 CA 2540216 CA 2540216 A CA2540216 A CA 2540216A CA 2540216 A1 CA2540216 A1 CA 2540216A1
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- Prior art keywords
- tri
- antenna element
- element according
- polar antenna
- polar
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q21/00—Antenna arrays or systems
- H01Q21/06—Arrays of individually energised antenna units similarly polarised and spaced apart
- H01Q21/061—Two dimensional planar arrays
- H01Q21/065—Patch antenna array
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q1/00—Details of, or arrangements associated with, antennas
- H01Q1/12—Supports; Mounting means
- H01Q1/22—Supports; Mounting means by structural association with other equipment or articles
- H01Q1/24—Supports; Mounting means by structural association with other equipment or articles with receiving set
- H01Q1/241—Supports; Mounting means by structural association with other equipment or articles with receiving set used in mobile communications, e.g. GSM
- H01Q1/246—Supports; Mounting means by structural association with other equipment or articles with receiving set used in mobile communications, e.g. GSM specially adapted for base stations
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q13/00—Waveguide horns or mouths; Slot antennas; Leaky-waveguide antennas; Equivalent structures causing radiation along the transmission path of a guided wave
- H01Q13/10—Resonant slot antennas
- H01Q13/106—Microstrip slot antennas
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q13/00—Waveguide horns or mouths; Slot antennas; Leaky-waveguide antennas; Equivalent structures causing radiation along the transmission path of a guided wave
- H01Q13/10—Resonant slot antennas
- H01Q13/18—Resonant slot antennas the slot being backed by, or formed in boundary wall of, a resonant cavity ; Open cavity antennas
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q21/00—Antenna arrays or systems
- H01Q21/0006—Particular feeding systems
- H01Q21/0075—Stripline fed arrays
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q9/00—Electrically-short antennas having dimensions not more than twice the operating wavelength and consisting of conductive active radiating elements
- H01Q9/04—Resonant antennas
- H01Q9/0407—Substantially flat resonant element parallel to ground plane, e.g. patch antenna
- H01Q9/0428—Substantially flat resonant element parallel to ground plane, e.g. patch antenna radiating a circular polarised wave
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q9/00—Electrically-short antennas having dimensions not more than twice the operating wavelength and consisting of conductive active radiating elements
- H01Q9/04—Resonant antennas
- H01Q9/0407—Substantially flat resonant element parallel to ground plane, e.g. patch antenna
- H01Q9/045—Substantially flat resonant element parallel to ground plane, e.g. patch antenna with particular feeding means
- H01Q9/0457—Substantially flat resonant element parallel to ground plane, e.g. patch antenna with particular feeding means electromagnetically coupled to the feed line
Description
Shapiro Cohen No.: 1763P04CA01 TRI-POLAR ANTENNA ARRAY ELEMENT
FIELD OF THE INVENTION
The present invention relates to antenna elements and in particular to beamformed antenna elements.
BACKGROUND TO THE INVENTION
In beamformed or steerable antenna systems, such as may be used in base stations for cellular telephone networks, an antenna may be comprised of an array of identical antenna elements mutually spatially arranged in a grid of m by n elements in either a planar or surface conformal arrangement.
As transmission and user bandwidths and capacities increase in order to meet user demand, the number of signals that must be radiated will also increase.
Typically, such increase is achieved by installing more transmitters. With the increase in the number of transmitters, one solution is to add a correspondingly higher number of antennas.
However, with the advent of modern beamforming antenna arrays, the addition of another antenna is no longer a trivial task, as the array comprises a monolithic structure for which a suitable footprint must be obtained.
Unfortunately the demand for transmission and user bandwidth tends to concentrate in highly urban areas where physical space is often at a premium. As a result, many Shapiro Cohen No.: 1763P04CA01 site managers now rent available footprint space according to the number of antennas.
An initial solution was to combine multiple transmitters to a common antenna. Unfortunately, it is generally accepted as a rule of thumb that combining a transmitter to an antenna uses 3dB of the transmitted power for each combination. Thus, to combine 4 transmitters to a single antenna imposes a 6 dB power loss. To combine 8 transmitters to a single antenna imposes a staggering 9 dB
loss.
Some efficiency was obtained with the development of the dual polarized antenna, where the polarizations are orthogonally oriented at 90 to one another. The component antenna elements generally have one port per polarization and a transmitter can be connected to the port without any combination losses.
Even with the introduction of dual polarized antennas, capacity is still outstripping the number of antennas available, so further economy is required in order to avoid the combination power loss problem.
Some antenna designers have introduced so-called quadrature-polarized antenna elements, but upon investigation, these prove to be simply packs of two dual-polarized antenna elements, which have been so packaged because lease rates for base station sites are generally by the antenna so that an economy can sometimes be realized when dealing with less observant leasing managers.
Thus, while economies are therefore achievable in terms of cost, as a practical matter, such dual packs of
FIELD OF THE INVENTION
The present invention relates to antenna elements and in particular to beamformed antenna elements.
BACKGROUND TO THE INVENTION
In beamformed or steerable antenna systems, such as may be used in base stations for cellular telephone networks, an antenna may be comprised of an array of identical antenna elements mutually spatially arranged in a grid of m by n elements in either a planar or surface conformal arrangement.
As transmission and user bandwidths and capacities increase in order to meet user demand, the number of signals that must be radiated will also increase.
Typically, such increase is achieved by installing more transmitters. With the increase in the number of transmitters, one solution is to add a correspondingly higher number of antennas.
However, with the advent of modern beamforming antenna arrays, the addition of another antenna is no longer a trivial task, as the array comprises a monolithic structure for which a suitable footprint must be obtained.
Unfortunately the demand for transmission and user bandwidth tends to concentrate in highly urban areas where physical space is often at a premium. As a result, many Shapiro Cohen No.: 1763P04CA01 site managers now rent available footprint space according to the number of antennas.
An initial solution was to combine multiple transmitters to a common antenna. Unfortunately, it is generally accepted as a rule of thumb that combining a transmitter to an antenna uses 3dB of the transmitted power for each combination. Thus, to combine 4 transmitters to a single antenna imposes a 6 dB power loss. To combine 8 transmitters to a single antenna imposes a staggering 9 dB
loss.
Some efficiency was obtained with the development of the dual polarized antenna, where the polarizations are orthogonally oriented at 90 to one another. The component antenna elements generally have one port per polarization and a transmitter can be connected to the port without any combination losses.
Even with the introduction of dual polarized antennas, capacity is still outstripping the number of antennas available, so further economy is required in order to avoid the combination power loss problem.
Some antenna designers have introduced so-called quadrature-polarized antenna elements, but upon investigation, these prove to be simply packs of two dual-polarized antenna elements, which have been so packaged because lease rates for base station sites are generally by the antenna so that an economy can sometimes be realized when dealing with less observant leasing managers.
Thus, while economies are therefore achievable in terms of cost, as a practical matter, such dual packs of
2 Shapiro Cohen No.: 1763P04CA01 dual-polarized elements occupy effectively the same physical footprint as a pair of discrete dual-polarized elements and do not resolve the combination power loss problem so that there is no economy in terms of footprint and thus physical resources.
SUMMARY OF THE INVENTION
Accordingly, it is desirable to provide a multiply-polarized antenna element for use in a beamforming antenna array that maximizes use of available footprint.
It is further desirable to provide a multiply-polarized antenna element configuration that is compact so as to facilitate other antenna design constraints.
The present invention accomplishes these aims by providing a tri-polar antenna element that effectively utilizes the space traditionally occupied by a dual polarized antenna element configuration.
In beamformed antenna arrays, the spacing between the centres of adjacent rows and/or columns imposes a performance constraint. For example, those skilled in the relevant art will understand that exceeding array spacing threshold maxima may introduce grating lobes in the radiated signal, which is generally undesirable. As an exemplary rule of thumb, array elements may be restricted to no more than 0.5 wavelength spacing.
We have found that in a typical array, particularly one in which the signal is steered off centre and a narrow beam is used, one could use the de facto 0.5 wavelength spacing in the azimuthal plane but increase the
SUMMARY OF THE INVENTION
Accordingly, it is desirable to provide a multiply-polarized antenna element for use in a beamforming antenna array that maximizes use of available footprint.
It is further desirable to provide a multiply-polarized antenna element configuration that is compact so as to facilitate other antenna design constraints.
The present invention accomplishes these aims by providing a tri-polar antenna element that effectively utilizes the space traditionally occupied by a dual polarized antenna element configuration.
In beamformed antenna arrays, the spacing between the centres of adjacent rows and/or columns imposes a performance constraint. For example, those skilled in the relevant art will understand that exceeding array spacing threshold maxima may introduce grating lobes in the radiated signal, which is generally undesirable. As an exemplary rule of thumb, array elements may be restricted to no more than 0.5 wavelength spacing.
We have found that in a typical array, particularly one in which the signal is steered off centre and a narrow beam is used, one could use the de facto 0.5 wavelength spacing in the azimuthal plane but increase the
3 Shapiro Cohen No.: 1763P04CA01 spacing in the elevation plane to 0.8 wavelength spacing.
The greater wavelength spacing in the elevation plane is generally considered acceptable because typically the narrow beamwidth and low skew angle of the beam provides assistance so that the undesirable grating lobes cannot form, and is usually taken into account and used in laying out beamformed dual polarization antenna arrays, such as for the patch radiator, discussed below.
Leaving aside the performance implications, it is generally desirable to optimize the array element spacing so as to produce an antenna array with the smallest physical footprint consistent with the required radiation pattern.
The present invention takes advantage of hitherto unused space in dual-polarized antenna elements, namely the additional 0.3 wavelength spacing between elements corresponding to the elevation plane.
A single polarization (nominally vertically oriented) antenna element occupies this spacing with the result that a tri-polar antenna array may occupy the same physical footprint as a comparable doubly-polarized array.
According to a broad aspect of an embodiment of the present invention, there is disclosed a tri-polarized antenna element of an antenna array, comprising a tri-polar antenna element for use in a beamforming antenna array comprising a plurality of mutually spaced apart antenna elements in azimuthal and elevation directions, the antenna element comprising:
The greater wavelength spacing in the elevation plane is generally considered acceptable because typically the narrow beamwidth and low skew angle of the beam provides assistance so that the undesirable grating lobes cannot form, and is usually taken into account and used in laying out beamformed dual polarization antenna arrays, such as for the patch radiator, discussed below.
Leaving aside the performance implications, it is generally desirable to optimize the array element spacing so as to produce an antenna array with the smallest physical footprint consistent with the required radiation pattern.
The present invention takes advantage of hitherto unused space in dual-polarized antenna elements, namely the additional 0.3 wavelength spacing between elements corresponding to the elevation plane.
A single polarization (nominally vertically oriented) antenna element occupies this spacing with the result that a tri-polar antenna array may occupy the same physical footprint as a comparable doubly-polarized array.
According to a broad aspect of an embodiment of the present invention, there is disclosed a tri-polarized antenna element of an antenna array, comprising a tri-polar antenna element for use in a beamforming antenna array comprising a plurality of mutually spaced apart antenna elements in azimuthal and elevation directions, the antenna element comprising:
4 Shapiro Cohen No.: 1763P04CA01 (a) a pair of slots oriented mutually orthogonally to one another and defining a first plane thereby incorporating the azimuthal and elevation directions;
(b) a dual feed network extending along a second plane parallel to the first plane and subimposed thereunder;
(c) a dual polarization patch radiator extending along a third plane parallel to the first plane;
(d) a linear slot extending in a direction bisecting the azimuthal and elevation directions along a fourth plane coplanar with the first plane and adjacent thereto along the elevation direction;
(e) a linear feed network extending along a fifth plane coplanar with the second plane and adjacent thereto along the elevation direction; and wherein the array elements are sufficiently proximate so as to avoid the formation of grating lobes in a radiated signal.
Figure 1 shows a passive array antenna system;
Figure 2 is a cross-section of a composite polarization antenna element of the invention;
Shapiro Cohen No.: 1763P04CA01 Figure 3 is a partially exploded view of the element of Figure 2;
Figure 4 shows a patch radiator;
Figure 5 shows a linear slot;
Figure 6 shows a crossed slot structure;
Figure 7 shows a linear slot feed network structure;
Figure 8 shows a crossed slot feed network structure; and Figure 9 shows an air bridge structure.
Figure 1 shows the primary elements of a typical passive array antenna system comprising a plurality of multiply-polarized antenna elements 100. Each port corresponding to a polarization of an antenna element is connected to a plurality of first beamforming networks 110 used to shape the beam in a first radiating plane, which may be the azimuthal plane or the elevation plane.
In accordance with the above-described generally accepted rule of thumb, the array spacing of elements corresponding to the azimuthal plane is on the order of 0.5 wavelength, while the array spacing of elements corresponding to the elevation plane is on the order 0.8 wavelength.
The combined ports 120 of the first beamforming networks 110 are connected to input ports 130 of a second Shapiro Cohen No.: 1763P04CA01 beamforming network 140 used to shape the beam in a second radiating plane orthogonal to the first radiating plane.
Thus, the two sets of beamforming networks 110, 140 are capable of forming a composite three dimensional radiating pattern. The output 150 of the second beamforming network 140 passes to the output port 160 of the antenna, which is connected to the input of a base station system (not shown).
Figure 2 shows a composite polarization antenna element in cross-section. In the exemplary design, the antenna element comprises a cavity backed, slot fed tri-polarized patched element. Such an element comprises the components that one of ordinary skill in the relevant art might use to implement a cavity-backed slot fed dual polarized patched element as is known in the art, namely, in order from the back of the radiating element to the front, a cavity structure 210, a dual feed network 230, a pair of slots 240, linear slot 250 and a patch radiator 270 on a substrate 260.
The cavity structure 210 is a sheet metal structure that ensures that all of the radiated energy emerges out of the front of the antenna element. The general arrangement of the cavity structure 210 is shown in exploded view in Figure 3. It comprises a shallow 5-sided brass box 210 which may be, for exemplary purposes only, approximately 10 mm deep and may be manufactured using a variety of different materials such as would appeal to one having ordinary skill in this art, taking into account the choice and relative merits of each.
Shapiro Cohen No.: 1763P04CA01 The exemplary depth of 10 mm ensure that the array element may achieve an adequate bandwidth for the application, in this case, the PCS frequency band of approximately 1900 MHz. However, those having ordinary skill in this art will readily recognize that the depth of the cavity structure 210 may be adjusted to accommodate other applications and/or operating frequency bands.
As shown in Figure 4, the patch radiator 270 comprises patch element 410, printed on a supporting board structure 400 mounted over antenna elements via mounting holes 420, and may be manufactured using a variety of materials such as foam, sheet or composite dielectric materials.
The dual feed network 230 is largely to provide the necessary fields to drive the patch radiator 270 by exciting the right field structure on the patch radiator 270. The dual feed network 230 is connected to the external beamforming elements by coaxial tube assemblies 280.
The slots 240 are used in dual polarization elements in order to minimize any mutual coupling between adjacent antenna elements. Preferably, the slots 240 are set out in a crossed slot configuration to minimize its footprint. The general arrangement of the crossed slot structure is shown in Figure 6. It comprises a crossed slot pair 610 printed on a low loss substrate 600 and is used to provide radiation in two orthogonal planes. The choice of substrate is well known to those having ordinary skill in this art. In the case of an exemplary cellular Shapiro Cohen No.: 1763P04CA01 base station antenna system, these are the +45 and -45 planes.
As is known to those having ordinary skill in this art, the dual feed network 230 and the slots 240 are mounted on opposite sides of a double sided printed circuit board 220 supported by the cavity structure 210, with the dual feed network 230 on the surface inside the cavity structure 210 and the slots 240 facing toward the patch radiator 270.
The general arrangement of the crossed slot feed network structure 870 is shown in Figure 8, and comprises a pair of substantially identical (but reversed in orientation) tuning fork feed networks 810 with matching sections 820. The fork feed networks 810 and matching sections 820 may be approximately mirrored. This mirroring would be approximate as only the large features would be mirrored; small features could be adjusted to suit the matching between the two feed networks. Because the two feed networks will cross over, cross coupling at the points of intersection is minimized by tapering the lines in this region, as shown in detail 830. A fine printed line 840 is used for one feed and a ceramic chip zero ohm resistor 850 is used to bridge the line for the other feed over it while ensuring conductive isolation between them. Those having ordinary skill in the art will readily recognize that according to the designer's preference, a conventional air bridge structure, such as is shown in Figure 9 could also be used in place of the zero ohm resistor 850. In the illustrated exemplary embodiment of Figure 8, a consistent structure is used for each of the crossovers, although it Shapiro Cohen No.: 1763P04CA01 will be recognized by those having ordinary skill in this art that other arrangements may be used generally or in specific instances as warranted. However, the nature of the implementation of the crossovers will affect the precise detail of the design of the corresponding matching network 870. In any event, coaxial transitions are provided for both polarizations.
The patch radiator 270 is the active or radiating part of the antenna element. Preferably, the patch radiator is silkscreened onto a substrate such as polycarbonate using a highly conductive ink, such as a silver-loaded ink, or other suitable conductive inks.
Alternatively, the patch radiator could be printed onto a suspended substrate, which could be made from Mylar , Kevlar or Kapton .
In a crossed slot fed dual polarized antenna element, patch radiator 270 is frequently provided to boost the radiated energy, which may have become attenuated or degraded as a result of the cross-coupling between the two polarizations.
Frequently, because of the layout constraints of such devices, the additional 0.3 wavelength spacing in the elevation plane is used up in the layout of the patch radiator 270 on the substrate.
A radome 295 (shown in Figure 2) is provided over the element for environmental protection.
To control mutual coupling between the various elements and between element assemblies when mounted into Shapiro Cohen No.: 1763P04CA01 an array, a plurality of field suppression fingers 290 (shown in Figure 3) are built into the cavity structure 210 and are also used to support the patch radiator 270. The fingers 290 are provided on four of the sides of the cavity structure 210 to control and limit the mutual coupling between elements. Those having ordinary skill in this art will readily recognize that other manufacturing methods may be feasible and well known and may be implemented without departing from the spirit and scope of the present invention.
To implement the third vertically polarized antenna element, that portion of the printed circuit board 220 that corresponds to the additional 0.3 wavelength spacing in the elevation plane is available for use and is occupied by a linear slot feed network structure 750 (shown in Figure 7)adjacent to the dual feed network 230 and a corresponding linear dumbbell slot structure 550 on low-loss substrate 500(shown in Figure 5) adjacent to the crossed slot structure 610 on low-loss substrate 600(shown in Figure 6).
The general arrangement of the linear slot feed network structure is shown in Figure 7. It comprises a 50 ohm line 710 exciting the slot together with a single section matching network 720 and a coaxial transition 730, all printed on the low loss substrate 700, which is common with the dual sided printed circuit board 220.
Because it is not dual polarized, it has been found that no patch radiator would typically be called for, with the result that no accommodation need be made in the layout of the patch radiator 270 for the dual polarized Shapiro Cohen No.: 1763P04CA01 antenna element across the additional 0.3 wavelength spacing in the elevation plane.
Because the polarization on the dual polarized antenna element is typically +45 and -45 and the third polarization of the present invention is vertically polarized, there is in fact some cross coupling between the signal for the third polarization and those for the dual polarities of the dual polarized antenna element. However, it appears that because any single user is concerned with only one polarization, the cross-coupling problem can be easily dealt with using sector design considerations known to those having ordinary skill in the relevant art.
Because, with the saving of on average 0.5 antennas, one would expect to achieve an overall 1.77 dB
improvement in the available power output using the inventive tri-polar antenna element structure.
Other embodiments consistent with the present invention will become apparent from consideration of the specification and the practice of the invention disclosed therein.
Accordingly, the specification and the embodiments are to be considered exemplary only, with a true scope and spirit of the invention being disclosed by the following claims.
(b) a dual feed network extending along a second plane parallel to the first plane and subimposed thereunder;
(c) a dual polarization patch radiator extending along a third plane parallel to the first plane;
(d) a linear slot extending in a direction bisecting the azimuthal and elevation directions along a fourth plane coplanar with the first plane and adjacent thereto along the elevation direction;
(e) a linear feed network extending along a fifth plane coplanar with the second plane and adjacent thereto along the elevation direction; and wherein the array elements are sufficiently proximate so as to avoid the formation of grating lobes in a radiated signal.
Figure 1 shows a passive array antenna system;
Figure 2 is a cross-section of a composite polarization antenna element of the invention;
Shapiro Cohen No.: 1763P04CA01 Figure 3 is a partially exploded view of the element of Figure 2;
Figure 4 shows a patch radiator;
Figure 5 shows a linear slot;
Figure 6 shows a crossed slot structure;
Figure 7 shows a linear slot feed network structure;
Figure 8 shows a crossed slot feed network structure; and Figure 9 shows an air bridge structure.
Figure 1 shows the primary elements of a typical passive array antenna system comprising a plurality of multiply-polarized antenna elements 100. Each port corresponding to a polarization of an antenna element is connected to a plurality of first beamforming networks 110 used to shape the beam in a first radiating plane, which may be the azimuthal plane or the elevation plane.
In accordance with the above-described generally accepted rule of thumb, the array spacing of elements corresponding to the azimuthal plane is on the order of 0.5 wavelength, while the array spacing of elements corresponding to the elevation plane is on the order 0.8 wavelength.
The combined ports 120 of the first beamforming networks 110 are connected to input ports 130 of a second Shapiro Cohen No.: 1763P04CA01 beamforming network 140 used to shape the beam in a second radiating plane orthogonal to the first radiating plane.
Thus, the two sets of beamforming networks 110, 140 are capable of forming a composite three dimensional radiating pattern. The output 150 of the second beamforming network 140 passes to the output port 160 of the antenna, which is connected to the input of a base station system (not shown).
Figure 2 shows a composite polarization antenna element in cross-section. In the exemplary design, the antenna element comprises a cavity backed, slot fed tri-polarized patched element. Such an element comprises the components that one of ordinary skill in the relevant art might use to implement a cavity-backed slot fed dual polarized patched element as is known in the art, namely, in order from the back of the radiating element to the front, a cavity structure 210, a dual feed network 230, a pair of slots 240, linear slot 250 and a patch radiator 270 on a substrate 260.
The cavity structure 210 is a sheet metal structure that ensures that all of the radiated energy emerges out of the front of the antenna element. The general arrangement of the cavity structure 210 is shown in exploded view in Figure 3. It comprises a shallow 5-sided brass box 210 which may be, for exemplary purposes only, approximately 10 mm deep and may be manufactured using a variety of different materials such as would appeal to one having ordinary skill in this art, taking into account the choice and relative merits of each.
Shapiro Cohen No.: 1763P04CA01 The exemplary depth of 10 mm ensure that the array element may achieve an adequate bandwidth for the application, in this case, the PCS frequency band of approximately 1900 MHz. However, those having ordinary skill in this art will readily recognize that the depth of the cavity structure 210 may be adjusted to accommodate other applications and/or operating frequency bands.
As shown in Figure 4, the patch radiator 270 comprises patch element 410, printed on a supporting board structure 400 mounted over antenna elements via mounting holes 420, and may be manufactured using a variety of materials such as foam, sheet or composite dielectric materials.
The dual feed network 230 is largely to provide the necessary fields to drive the patch radiator 270 by exciting the right field structure on the patch radiator 270. The dual feed network 230 is connected to the external beamforming elements by coaxial tube assemblies 280.
The slots 240 are used in dual polarization elements in order to minimize any mutual coupling between adjacent antenna elements. Preferably, the slots 240 are set out in a crossed slot configuration to minimize its footprint. The general arrangement of the crossed slot structure is shown in Figure 6. It comprises a crossed slot pair 610 printed on a low loss substrate 600 and is used to provide radiation in two orthogonal planes. The choice of substrate is well known to those having ordinary skill in this art. In the case of an exemplary cellular Shapiro Cohen No.: 1763P04CA01 base station antenna system, these are the +45 and -45 planes.
As is known to those having ordinary skill in this art, the dual feed network 230 and the slots 240 are mounted on opposite sides of a double sided printed circuit board 220 supported by the cavity structure 210, with the dual feed network 230 on the surface inside the cavity structure 210 and the slots 240 facing toward the patch radiator 270.
The general arrangement of the crossed slot feed network structure 870 is shown in Figure 8, and comprises a pair of substantially identical (but reversed in orientation) tuning fork feed networks 810 with matching sections 820. The fork feed networks 810 and matching sections 820 may be approximately mirrored. This mirroring would be approximate as only the large features would be mirrored; small features could be adjusted to suit the matching between the two feed networks. Because the two feed networks will cross over, cross coupling at the points of intersection is minimized by tapering the lines in this region, as shown in detail 830. A fine printed line 840 is used for one feed and a ceramic chip zero ohm resistor 850 is used to bridge the line for the other feed over it while ensuring conductive isolation between them. Those having ordinary skill in the art will readily recognize that according to the designer's preference, a conventional air bridge structure, such as is shown in Figure 9 could also be used in place of the zero ohm resistor 850. In the illustrated exemplary embodiment of Figure 8, a consistent structure is used for each of the crossovers, although it Shapiro Cohen No.: 1763P04CA01 will be recognized by those having ordinary skill in this art that other arrangements may be used generally or in specific instances as warranted. However, the nature of the implementation of the crossovers will affect the precise detail of the design of the corresponding matching network 870. In any event, coaxial transitions are provided for both polarizations.
The patch radiator 270 is the active or radiating part of the antenna element. Preferably, the patch radiator is silkscreened onto a substrate such as polycarbonate using a highly conductive ink, such as a silver-loaded ink, or other suitable conductive inks.
Alternatively, the patch radiator could be printed onto a suspended substrate, which could be made from Mylar , Kevlar or Kapton .
In a crossed slot fed dual polarized antenna element, patch radiator 270 is frequently provided to boost the radiated energy, which may have become attenuated or degraded as a result of the cross-coupling between the two polarizations.
Frequently, because of the layout constraints of such devices, the additional 0.3 wavelength spacing in the elevation plane is used up in the layout of the patch radiator 270 on the substrate.
A radome 295 (shown in Figure 2) is provided over the element for environmental protection.
To control mutual coupling between the various elements and between element assemblies when mounted into Shapiro Cohen No.: 1763P04CA01 an array, a plurality of field suppression fingers 290 (shown in Figure 3) are built into the cavity structure 210 and are also used to support the patch radiator 270. The fingers 290 are provided on four of the sides of the cavity structure 210 to control and limit the mutual coupling between elements. Those having ordinary skill in this art will readily recognize that other manufacturing methods may be feasible and well known and may be implemented without departing from the spirit and scope of the present invention.
To implement the third vertically polarized antenna element, that portion of the printed circuit board 220 that corresponds to the additional 0.3 wavelength spacing in the elevation plane is available for use and is occupied by a linear slot feed network structure 750 (shown in Figure 7)adjacent to the dual feed network 230 and a corresponding linear dumbbell slot structure 550 on low-loss substrate 500(shown in Figure 5) adjacent to the crossed slot structure 610 on low-loss substrate 600(shown in Figure 6).
The general arrangement of the linear slot feed network structure is shown in Figure 7. It comprises a 50 ohm line 710 exciting the slot together with a single section matching network 720 and a coaxial transition 730, all printed on the low loss substrate 700, which is common with the dual sided printed circuit board 220.
Because it is not dual polarized, it has been found that no patch radiator would typically be called for, with the result that no accommodation need be made in the layout of the patch radiator 270 for the dual polarized Shapiro Cohen No.: 1763P04CA01 antenna element across the additional 0.3 wavelength spacing in the elevation plane.
Because the polarization on the dual polarized antenna element is typically +45 and -45 and the third polarization of the present invention is vertically polarized, there is in fact some cross coupling between the signal for the third polarization and those for the dual polarities of the dual polarized antenna element. However, it appears that because any single user is concerned with only one polarization, the cross-coupling problem can be easily dealt with using sector design considerations known to those having ordinary skill in the relevant art.
Because, with the saving of on average 0.5 antennas, one would expect to achieve an overall 1.77 dB
improvement in the available power output using the inventive tri-polar antenna element structure.
Other embodiments consistent with the present invention will become apparent from consideration of the specification and the practice of the invention disclosed therein.
Accordingly, the specification and the embodiments are to be considered exemplary only, with a true scope and spirit of the invention being disclosed by the following claims.
Claims (25)
EXCLUSIVE PROPERTY OR PRIVILEGE IS CLAIMED ARE:
WE CLAIM:
1. A tri-polar antenna element for use in a beamforming antenna array comprising a plurality of mutually spaced apart antenna elements in azimuthal and elevation directions, the antenna element comprising:
(a) a pair of slots oriented mutually orthogonally to one another and defining a first plane thereby incorporating the azimuthal and elevation directions;
(b) a dual feed network extending along a second plane parallel to the first plane and subimposed thereunder;
(c) a dual polarization patch radiator extending along a third plane parallel to the first plane;
(d) a linear slot extending in a direction bisecting the azimuthal and elevation directions along a fourth plane coplanar with the first plane and adjacent thereto along the elevation direction;
(e) a linear feed network extending along a fifth plane coplanar with the second plane and adjacent thereto along the elevation direction; and wherein the array elements are sufficiently proximate so as to avoid the formation of grating lobes in a radiated signal.
(a) a pair of slots oriented mutually orthogonally to one another and defining a first plane thereby incorporating the azimuthal and elevation directions;
(b) a dual feed network extending along a second plane parallel to the first plane and subimposed thereunder;
(c) a dual polarization patch radiator extending along a third plane parallel to the first plane;
(d) a linear slot extending in a direction bisecting the azimuthal and elevation directions along a fourth plane coplanar with the first plane and adjacent thereto along the elevation direction;
(e) a linear feed network extending along a fifth plane coplanar with the second plane and adjacent thereto along the elevation direction; and wherein the array elements are sufficiently proximate so as to avoid the formation of grating lobes in a radiated signal.
2. A tri-polar antenna element according to claim 1, wherein one of the slots extends in a direction oriented at +45° relative to the elevation direction and the other slot extends in a direction oriented at -45° relative to the elevation direction.
3. A tri-polar antenna element according to claim 1, wherein the spacing between array elements extending in the azimuthal direction is less than substantially 0.5 of the operating wavelength of the antenna array.
4. A tri-polar antenna element according to claim 1, wherein the spacing between array elements extending in the elevation direction is less than substantially 0.8 of the operating wavelength of the antenna array.
5. A tri-polar antenna element according to claim 1, wherein a beam generated by the antenna array is steered off centre.
6. A tri-polar antenna element according to claim 5, wherein the antenna array generates a narrow beam.
7. A tri-polar antenna element according to claim 1, wherein the slots are disposed on a first surface of a planar substrate and the feed networks are disposed on a second surface of the substrate.
8. A tri-polar antenna element according to claim 7, wherein the linear slot comprises a dumbbell slot disposed on the first surface of the substrate.
9. A tri-polar antenna element according to claim 7, wherein the substrate is a printed circuit board.
10. A tri-polar antenna element according to claim 7, wherein the substrate is supported by a cavity structure.
11. A tri-polar antenna element according to claim 10, wherein the substrate is supported by fingers provided on the cavity structure.
12. A tri-polar antenna element according to claim 10, wherein the feed networks are disposed on the surface of the substrate facing the cavity structure.
13. A tri-polar antenna element according to claim 12, wherein the patch radiator is supported by the cavity structure proximate to the surface of the substrate facing away from the cavity structure.
14. A tri-polar antenna element according to claim 13, wherein the patch radiator is supported by fingers provided on the cavity structure.
15. A tri-polar antenna element according to claim 1, wherein the pair of slots intersect one another.
16. A tri-polar antenna element according to claim 1, wherein the dual feed network comprises first and second tuning fork feed networks.
17. A tri-polar antenna element according to claim 16, wherein the second tuning fork feed network is substantially a mirror image of the first tuning fork feed network.
18. A tri-polar antenna element according to claim 17, wherein the first and second tuning fork feed networks overlap at an overlap location.
19. A tri-polar antenna element according to claim 18, wherein a width of the first and second tuning fork feed networks are tapered proximate to the overlap location.
20. A tri-polar antenna element according to claim 18, wherein the first tuning fork feed network bridges the second tuning fork feed network at the overlap location.
21. A tri-polar antenna element according to claim 20, wherein the first tuning fork feed network is spaced apart from the second tuning fork feed network at the overlap location.
22. A tri-polar antenna element according to claim 21, wherein the first tuning fork feed network comprises a zero ohm resistor at the overlap location.
23. A tri-polar antenna element according to claim 21, wherein the first tuning fork feed network comprises an air bridge at the overlap location.
24. A tri-polar antenna element according to claim 1, wherein the patch radiator is annular.
25. A tri-polar antenna element according to claim 1, further comprising a radome disposed thereover.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2540216 CA2540216A1 (en) | 2006-03-17 | 2006-03-17 | Tri-polar antenna array element |
| PCT/CA2007/000386 WO2007106976A1 (en) | 2006-03-17 | 2007-03-09 | Tri-polar antenna array element |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2540216 CA2540216A1 (en) | 2006-03-17 | 2006-03-17 | Tri-polar antenna array element |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2540216A1 true CA2540216A1 (en) | 2007-09-17 |
Family
ID=38520884
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2540216 Abandoned CA2540216A1 (en) | 2006-03-17 | 2006-03-17 | Tri-polar antenna array element |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA2540216A1 (en) |
| WO (1) | WO2007106976A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3910735A1 (en) * | 2020-05-11 | 2021-11-17 | Nokia Solutions and Networks Oy | An antenna arrangement |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20100295750A1 (en) * | 2007-10-09 | 2010-11-25 | Agency For Science, Technology And Research | Antenna for diversity applications |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5241321A (en) * | 1992-05-15 | 1993-08-31 | Space Systems/Loral, Inc. | Dual frequency circularly polarized microwave antenna |
| US6297774B1 (en) * | 1997-03-12 | 2001-10-02 | Hsin- Hsien Chung | Low cost high performance portable phased array antenna system for satellite communication |
| KR100207600B1 (en) * | 1997-03-31 | 1999-07-15 | 윤종용 | Cavity-backed microstrip dipole antenna array |
-
2006
- 2006-03-17 CA CA 2540216 patent/CA2540216A1/en not_active Abandoned
-
2007
- 2007-03-09 WO PCT/CA2007/000386 patent/WO2007106976A1/en active Application Filing
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3910735A1 (en) * | 2020-05-11 | 2021-11-17 | Nokia Solutions and Networks Oy | An antenna arrangement |
| US11695218B2 (en) | 2020-05-11 | 2023-07-04 | Nokia Solutions And Networks Oy | Antenna arrangement |
Also Published As
| Publication number | Publication date |
|---|---|
| WO2007106976A1 (en) | 2007-09-27 |
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