CA2540220A1 - Split-sector array - Google Patents
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- CA2540220A1 CA2540220A1 CA002540220A CA2540220A CA2540220A1 CA 2540220 A1 CA2540220 A1 CA 2540220A1 CA 002540220 A CA002540220 A CA 002540220A CA 2540220 A CA2540220 A CA 2540220A CA 2540220 A1 CA2540220 A1 CA 2540220A1
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- 239000011159 matrix material Substances 0.000 claims description 10
- 239000000470 constituent Substances 0.000 claims description 3
- 238000013461 design Methods 0.000 description 10
- 238000003491 array Methods 0.000 description 4
- 238000013459 approach Methods 0.000 description 3
- 230000001413 cellular effect Effects 0.000 description 3
- 230000010363 phase shift Effects 0.000 description 3
- 230000035945 sensitivity Effects 0.000 description 3
- 230000008901 benefit Effects 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 230000009977 dual effect Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000010287 polarization Effects 0.000 description 2
- 230000002238 attenuated effect Effects 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 230000003278 mimic effect Effects 0.000 description 1
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Classifications
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- 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
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q21/00—Antenna arrays or systems
- H01Q21/29—Combinations of different interacting antenna units for giving a desired directional characteristic
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
- H01Q3/26—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
- H01Q3/26—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture
- H01Q3/30—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture varying the relative phase between the radiating elements of an array
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Description
Shapiro Cohen No.: 1763P06CA01 SPLIT-SECTOR ARRAY
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.
One method of achieving such increase is by high-order sectorization. To further improve spectrum efficiency of cellular systems, many cellular networks apply a sectorization concept in which an omni-directional antenna, traditionally placed in the centre of a cell, has been replaced by a plurality N of directional antennas.
Thus, for the same area, the number of cells, and consequently, the number of subscribers within the network, has been increased by a factor of N.
Shapiro Cohen No.: 1763P06CA01 The use of directional or sector antennas has thus further reduced the amount of interference in the network and has resulted in more spectrally efficient networks. A sector is generally wedge-shaped, with N
sectors generally extending outward from the traditional centre of a cell. Each sector may now be considered a distinct cell, with its antenna extending from an extremity thereof.
A traditional means of increasing network capacity, known as cell splitting, is to reduce the coverage of existing sites and to introduce a new site in the newly created coverage holes. Cell splitting is very expensive for an operator, since new locations for the tower and equipment for the new site, such as high rise buildings, have to be located and leased. In many dense urban environments, where increased network capacity is required, it is no longer possible to find suitable new site locations.
In a network employing sectorization, this may be achieved by replacing a sector antenna with a split-sector antenna that generates a plurality of beam coverage areas that in combination mimic the beam coverage area of the replaced antenna, but do so in a plurality of sub-sectors.
Because resources can be re-used between sectors, the introduction of sub-sectors effectively increases the subscriber bandwidth of the network.
Typically, such increase is achieved by installing more transmitters. Each additional antenna must be associated with a corresponding antenna.
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.
One method of achieving such increase is by high-order sectorization. To further improve spectrum efficiency of cellular systems, many cellular networks apply a sectorization concept in which an omni-directional antenna, traditionally placed in the centre of a cell, has been replaced by a plurality N of directional antennas.
Thus, for the same area, the number of cells, and consequently, the number of subscribers within the network, has been increased by a factor of N.
Shapiro Cohen No.: 1763P06CA01 The use of directional or sector antennas has thus further reduced the amount of interference in the network and has resulted in more spectrally efficient networks. A sector is generally wedge-shaped, with N
sectors generally extending outward from the traditional centre of a cell. Each sector may now be considered a distinct cell, with its antenna extending from an extremity thereof.
A traditional means of increasing network capacity, known as cell splitting, is to reduce the coverage of existing sites and to introduce a new site in the newly created coverage holes. Cell splitting is very expensive for an operator, since new locations for the tower and equipment for the new site, such as high rise buildings, have to be located and leased. In many dense urban environments, where increased network capacity is required, it is no longer possible to find suitable new site locations.
In a network employing sectorization, this may be achieved by replacing a sector antenna with a split-sector antenna that generates a plurality of beam coverage areas that in combination mimic the beam coverage area of the replaced antenna, but do so in a plurality of sub-sectors.
Because resources can be re-used between sectors, the introduction of sub-sectors effectively increases the subscriber bandwidth of the network.
Typically, such increase is achieved by installing more transmitters. Each additional antenna must be associated with a corresponding antenna.
2 Shapiro Cohen No.: 1763P06CA01 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.
Thus, another approach is to add additional 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 site managers now rent available footprint space according to the number of antennas.
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.
loss.
Thus, another approach is to add additional 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 site managers now rent available footprint space according to the number of antennas.
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.
3 Shapiro Cohen No.: 1763P06CA01 Another approach has been to reorganize the antenna array elements to form two antennas in place of one. For example, where one formerly had an 8 column by 12 row antenna array, one could simply allocate half of the columns to a first 4 column by 12 row antenna array and the remaining elements to a second 4 column by 12 row antenna array. Clearly, however, the trade-off of such a solution is reduced flexibility or sensitivity in the beam formed by such reduced complexity antenna arrays.
For example, those having ordinary skill in this art will recognize that the relationship between the column weights and the azimuth beam shape of the antenna is simply a Fourier transform. Just as in the audio realm, the greater the number of samples, that is, the greater the number of rows and/or columns, the more accurate one may be in the beam design.
SUMMARY OF THE INVENTION
Accordingly, it is desirable to provide a plurality of signals to a beamforming antenna array in a manner that maximizes use of available footprint without limiting the beam design.
It is further desirable to combine a plurality of signals at an antenna array without substantially adding to the amount of antenna array elements or reducing the sensitivity of the beam design.
The present invention accomplishes these aims by providing to a split-sector antenna array a plurality of signals that are allocated to the plurality of array elements in a manner that combining losses are restricted
For example, those having ordinary skill in this art will recognize that the relationship between the column weights and the azimuth beam shape of the antenna is simply a Fourier transform. Just as in the audio realm, the greater the number of samples, that is, the greater the number of rows and/or columns, the more accurate one may be in the beam design.
SUMMARY OF THE INVENTION
Accordingly, it is desirable to provide a plurality of signals to a beamforming antenna array in a manner that maximizes use of available footprint without limiting the beam design.
It is further desirable to combine a plurality of signals at an antenna array without substantially adding to the amount of antenna array elements or reducing the sensitivity of the beam design.
The present invention accomplishes these aims by providing to a split-sector antenna array a plurality of signals that are allocated to the plurality of array elements in a manner that combining losses are restricted
4 Shapiro Cohen No.: 1763P06CA01 to those rows or columns that contribute minimally to the beamformed coverage area. In so doing, the combining losses are restricted to low power rows or columns and are effectively attenuated. Nevertheless, the plurality of antenna elements may be effectively organized into two antenna arrays, each having more sensitivity than would be obtainable simply by dividing or allocating the antenna elements among the desired number of antennas.
Some configurations involve the use of a Butler matrix to feed a signal into a plurality of columns or rows that contribute a significant amount of power to the beamformed coverage area. The Butler matrix effectively eliminates combining loss, but this option is available only if the columns and rows are effectively of equal amplitude and mutually orthogonal.
According to a broad aspect of an embodiment of the present invention, there is disclosed an antenna array comprising a plurality of antenna elements for use in association with a plurality of beamformed antenna patterns each having a significant proportion of its radiated power concentrated in a subset of its constituent elements, wherein corresponding elemental powers of each of the plurality of patterns in the subset are combined together in a first manner while the remaining elemental powers of each of the plurality of patterns are combined in a second manner with the corresponding elemental powers of each of the other of the plurality of patterns, wherein a loss of total radiated power due to combining in the first manner of the elemental powers of each of the plurality of patterns in the subset is less than a loss of total Shapiro Cohen No.: 1763P06CA01 radiated power due to combining in the second manner of all of the elemental powers of each of the plurality of patterns.
In a beamformed antenna array, an array of antenna elements are varied in amplitude and phase in order to create a beam coverage area that is shaped to a desired contour. Such arrays could be one- or two-dimensional. In the latter situation, not infrequently, the beam-forming is done on a row-wise or column-wise basis.
In practice, the amplitude of the signal to be radiated by the beamforming antenna may be adjusted by splitting the available power among a plurality of (sets of) columns or rows of elements. For convenience, this is typically done on a pair-wise basis. Thus, there may be multiple layers of power-splitting (usually log2 n layers, where n is the number of rows or columns available) and the amplitude of each row or column will be in proportion to the amount of power ultimately provided to it.
The phase delay associated with each row or column may be adjusted by progressively introducing judiciously chosen delay elements along the power supply lines corresponding to each row or column so that the phase delay of each row or column will be in proportion to the total delay imparted to it.
Both the power-splitting and the introduction of delay are effectively lossless, in contrast to the significant losses that accumulate when signals are combined into a column or row.
Shapiro Cohen No.: 1763P06CA01 Those having ordinary skill in this art will readily recognize that the order by which the power-splitting takes place remains at the discretion of the antenna designer, although, for consistency purposes, typically adjacent columns have been grouped together.
It has been observed that for some beamformed coverage patterns designed for use in higher order split-sectorization as discussed previously, that is, for the two (in this case) beam patterns to be used in place of an original sector beam pattern, a significant proportion of the power has been drawn primarily from a small number of the rows and/or columns available to it.
For example, consider Table 1 below, which represents the elemental powers from an initial eight column antenna beam design being considered. The Table shows that for that exemplary design for an 8-column antenna array, fully 80% of the radiated power is concentrated in two beam columns, designated d and e, while miniscule amounts of power are allocated to beam columns b and g and only slightly greater amounts of power.
Column a b C d e F g h Weighting -20 -25 -14 -4 -4 -14 -25 -20 (dB) % Power 1 0.3 4 40 40 4 0.3 1 Table 1 Shapiro Cohen No.: 1763P06CA01 Figure 1 is an illustration of the beamformer for the split-sector array using the weights of table 1. The elements are numbered a through h, with d and e being the centermost columns containing the majority of the radiated power between the two beams. The signals for the two beams enter through the sector 1 and sector 2 ports respectively, and are divided out as shown, using the weights described in table 1, to excite the elements a through h.
Another interesting observation for those exemplary higher order sectorization beam patterns through sector splitting was that with the desired skew of the antenna array, there was approximately a 75 phase slope between adjacent columns. Accordingly, the exemplary beams were close to being orthogonal beams.
Those having ordinary skill in the relevant art will readily recognize that one of the features of an orthogonal beam is that the sum of the powers is constant and that they are one of the only types of beams that can be produced without loss in theory, in the absence of the effect of the element pattern.
As such, the exemplary beam designs for the two central beams were very close to being orthogonal (75 phase shift rather than 90 ) and had most of their powers centred in the middle two beams, which were largely equivalent in power.
Those having ordinary skill in this art will readily recognize that a Butler matrix has a known limitation in that it could only produce orthogonal beams.
Shapiro Cohen No.: 1763P06CA01 This means that if a 2x2 Butler matrix was applied to the centre two columns, a pair of orthogonal beams (in relation to those two columns) would be generated. The advantage of so doing is that a different signal could be injected into each of the two input ports of the Butler matrix, namely the signals injected into one port will form the first of the two beams, and the second will form the second of the two beams without any combining loss.
By appropriately coupling off some of a first signal and allocating the phase and amplitude in the conventional fashion for six weights, one could get eight ports for the first signal and, if done similarly, for the second signal. The outlying columns would be combined and following the above-described rule, would suffer approximately 3 dB of loss upon being so combined.
However, because the six ports where there is this combining loss only accounts for 20% of the power, the total power loss from combining is only 50% of 20% of the total power, or 10% of the total power. Those having ordinary skill in this art will readily recognize that this is equivalent to a 0.5 dB loss and thus a considerable improvement over the conventional way of combining two signals in one antenna, which results in a 3 dB loss.
As indicated, the only trade-off for achieving such an improvement in the access power is that the central columns need to be close to orthogonal beams so that one may use a "pseudo-Butler" matrix (in that only the two columns are so treated), which is a very cost-effective trade-off. In effect, one is able to effectively save an antenna and its constituent antenna elements. This savings Shapiro Cohen No.: 1763P06CA01 could be realized by reducing the cost of implementing the split sectorization in terms of antenna elements, or by increasing the accuracy of the beam pattern designs (in the exemplary situation for the split-sector patterns) by applying a greater number of antenna elements to each beam pattern design.
In order to deal with this trade-off, one will presumably fine tune the shape of the beam pattern, because the central two beams in this example will have 90 phase shift (as a result of the processing by the pseudo-Butler matrix) rather than the desired 75 phase shift, but this can be done by altering the power and phase relationships of the outlying beams in a manner well-known to those having ordinary skill in the relevant art.
Those having ordinary skill in this art will readily recognize that if one is prepared to compromise slightly on the accuracy of the beam design, one could dispense with the pseudo-Butler matrix entirely. That is to say, for beam designs in which the power was again concentrated in a small number of elements, but those predominant beams did not share a near orthogonal relationship, by slightly reducing the number of columns, one could again achieve savings in terms of overall signal degradation due to combining losses.
Consider for example, the si~uation where the two beam patterns had for example weights as set out below in Tables 2 and 3. (The numbers shown are approximations used for illustiatiTfe purposes.) Shapiro Cohen No.: 1763P06CA01 Column a B c d e f g h Beam Left -20 -1.4 - - -14 -20 Weighting 3.5 3.5 (dB) % Power 1 4 45 45 4 _ Table 2 Column al B2 c3 d4 e5 f6 g7 h8 Beam -20 -14 - - -14 -20 Right 3.5 3.5 Weighting (dB) % Pcwer _ 4 45 45 4 Table 3 Again, in both Table 2 and Table 3, the majority of 1:-he power in this case 90% of the power is carifined to two columns. In this example the four outer columns are fed directly by their appropriate beamforming r~e warks with no loss associated. The central four columns, however are fed with power from both beamforming networks. In this case knowledge of the relative weights from each beamforming ne:_work enables optimisation of the pawer c:ombining ratios both within the individual beamforming networks and at the Shapiro Cohen No.: 1763P06CA01 combining point to significantly reduce power loss compared wi-:"h :~he s=Lridelv prac:~iced 3dB power combining me'.hods. For the weights shown the use of 11dB combiners for columns c and f together with 7 dB combiners for columns d and e reduces the combing loss from 3 dB to 0.7 dB (-45% to -14%
of available power). Once this principle is understood the skilled practitioner of the art will be able to determine the optimal combining ratios for any required power distribution.
Figure 2 is an illustration of the beamformer for the split-sector array using the weights of Tables 2 and 3.
The elements are numbered a through h, with c, d, e and f being the centermost columns containing the majority of the radiated power between the two beams. The signals for the two beams enter through the sector 1 and sector 2 ports respectively, and are divided out as shown using the weights described in Tables 2 and 3 , to excite elements a through h.
The description of this invention has relied on the use of column weighting to provide an example of the invention. However, the skilled practitioner in the art will recognize that the same approach could be applied to row weighting with significant benefit.
Other embodiments consistent with the present invention will become apparent from consideration of the specification and the practice of the invention disclosed therein.
Shapiro Cohen No.: 1763P06CA01 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.
Some configurations involve the use of a Butler matrix to feed a signal into a plurality of columns or rows that contribute a significant amount of power to the beamformed coverage area. The Butler matrix effectively eliminates combining loss, but this option is available only if the columns and rows are effectively of equal amplitude and mutually orthogonal.
According to a broad aspect of an embodiment of the present invention, there is disclosed an antenna array comprising a plurality of antenna elements for use in association with a plurality of beamformed antenna patterns each having a significant proportion of its radiated power concentrated in a subset of its constituent elements, wherein corresponding elemental powers of each of the plurality of patterns in the subset are combined together in a first manner while the remaining elemental powers of each of the plurality of patterns are combined in a second manner with the corresponding elemental powers of each of the other of the plurality of patterns, wherein a loss of total radiated power due to combining in the first manner of the elemental powers of each of the plurality of patterns in the subset is less than a loss of total Shapiro Cohen No.: 1763P06CA01 radiated power due to combining in the second manner of all of the elemental powers of each of the plurality of patterns.
In a beamformed antenna array, an array of antenna elements are varied in amplitude and phase in order to create a beam coverage area that is shaped to a desired contour. Such arrays could be one- or two-dimensional. In the latter situation, not infrequently, the beam-forming is done on a row-wise or column-wise basis.
In practice, the amplitude of the signal to be radiated by the beamforming antenna may be adjusted by splitting the available power among a plurality of (sets of) columns or rows of elements. For convenience, this is typically done on a pair-wise basis. Thus, there may be multiple layers of power-splitting (usually log2 n layers, where n is the number of rows or columns available) and the amplitude of each row or column will be in proportion to the amount of power ultimately provided to it.
The phase delay associated with each row or column may be adjusted by progressively introducing judiciously chosen delay elements along the power supply lines corresponding to each row or column so that the phase delay of each row or column will be in proportion to the total delay imparted to it.
Both the power-splitting and the introduction of delay are effectively lossless, in contrast to the significant losses that accumulate when signals are combined into a column or row.
Shapiro Cohen No.: 1763P06CA01 Those having ordinary skill in this art will readily recognize that the order by which the power-splitting takes place remains at the discretion of the antenna designer, although, for consistency purposes, typically adjacent columns have been grouped together.
It has been observed that for some beamformed coverage patterns designed for use in higher order split-sectorization as discussed previously, that is, for the two (in this case) beam patterns to be used in place of an original sector beam pattern, a significant proportion of the power has been drawn primarily from a small number of the rows and/or columns available to it.
For example, consider Table 1 below, which represents the elemental powers from an initial eight column antenna beam design being considered. The Table shows that for that exemplary design for an 8-column antenna array, fully 80% of the radiated power is concentrated in two beam columns, designated d and e, while miniscule amounts of power are allocated to beam columns b and g and only slightly greater amounts of power.
Column a b C d e F g h Weighting -20 -25 -14 -4 -4 -14 -25 -20 (dB) % Power 1 0.3 4 40 40 4 0.3 1 Table 1 Shapiro Cohen No.: 1763P06CA01 Figure 1 is an illustration of the beamformer for the split-sector array using the weights of table 1. The elements are numbered a through h, with d and e being the centermost columns containing the majority of the radiated power between the two beams. The signals for the two beams enter through the sector 1 and sector 2 ports respectively, and are divided out as shown, using the weights described in table 1, to excite the elements a through h.
Another interesting observation for those exemplary higher order sectorization beam patterns through sector splitting was that with the desired skew of the antenna array, there was approximately a 75 phase slope between adjacent columns. Accordingly, the exemplary beams were close to being orthogonal beams.
Those having ordinary skill in the relevant art will readily recognize that one of the features of an orthogonal beam is that the sum of the powers is constant and that they are one of the only types of beams that can be produced without loss in theory, in the absence of the effect of the element pattern.
As such, the exemplary beam designs for the two central beams were very close to being orthogonal (75 phase shift rather than 90 ) and had most of their powers centred in the middle two beams, which were largely equivalent in power.
Those having ordinary skill in this art will readily recognize that a Butler matrix has a known limitation in that it could only produce orthogonal beams.
Shapiro Cohen No.: 1763P06CA01 This means that if a 2x2 Butler matrix was applied to the centre two columns, a pair of orthogonal beams (in relation to those two columns) would be generated. The advantage of so doing is that a different signal could be injected into each of the two input ports of the Butler matrix, namely the signals injected into one port will form the first of the two beams, and the second will form the second of the two beams without any combining loss.
By appropriately coupling off some of a first signal and allocating the phase and amplitude in the conventional fashion for six weights, one could get eight ports for the first signal and, if done similarly, for the second signal. The outlying columns would be combined and following the above-described rule, would suffer approximately 3 dB of loss upon being so combined.
However, because the six ports where there is this combining loss only accounts for 20% of the power, the total power loss from combining is only 50% of 20% of the total power, or 10% of the total power. Those having ordinary skill in this art will readily recognize that this is equivalent to a 0.5 dB loss and thus a considerable improvement over the conventional way of combining two signals in one antenna, which results in a 3 dB loss.
As indicated, the only trade-off for achieving such an improvement in the access power is that the central columns need to be close to orthogonal beams so that one may use a "pseudo-Butler" matrix (in that only the two columns are so treated), which is a very cost-effective trade-off. In effect, one is able to effectively save an antenna and its constituent antenna elements. This savings Shapiro Cohen No.: 1763P06CA01 could be realized by reducing the cost of implementing the split sectorization in terms of antenna elements, or by increasing the accuracy of the beam pattern designs (in the exemplary situation for the split-sector patterns) by applying a greater number of antenna elements to each beam pattern design.
In order to deal with this trade-off, one will presumably fine tune the shape of the beam pattern, because the central two beams in this example will have 90 phase shift (as a result of the processing by the pseudo-Butler matrix) rather than the desired 75 phase shift, but this can be done by altering the power and phase relationships of the outlying beams in a manner well-known to those having ordinary skill in the relevant art.
Those having ordinary skill in this art will readily recognize that if one is prepared to compromise slightly on the accuracy of the beam design, one could dispense with the pseudo-Butler matrix entirely. That is to say, for beam designs in which the power was again concentrated in a small number of elements, but those predominant beams did not share a near orthogonal relationship, by slightly reducing the number of columns, one could again achieve savings in terms of overall signal degradation due to combining losses.
Consider for example, the si~uation where the two beam patterns had for example weights as set out below in Tables 2 and 3. (The numbers shown are approximations used for illustiatiTfe purposes.) Shapiro Cohen No.: 1763P06CA01 Column a B c d e f g h Beam Left -20 -1.4 - - -14 -20 Weighting 3.5 3.5 (dB) % Power 1 4 45 45 4 _ Table 2 Column al B2 c3 d4 e5 f6 g7 h8 Beam -20 -14 - - -14 -20 Right 3.5 3.5 Weighting (dB) % Pcwer _ 4 45 45 4 Table 3 Again, in both Table 2 and Table 3, the majority of 1:-he power in this case 90% of the power is carifined to two columns. In this example the four outer columns are fed directly by their appropriate beamforming r~e warks with no loss associated. The central four columns, however are fed with power from both beamforming networks. In this case knowledge of the relative weights from each beamforming ne:_work enables optimisation of the pawer c:ombining ratios both within the individual beamforming networks and at the Shapiro Cohen No.: 1763P06CA01 combining point to significantly reduce power loss compared wi-:"h :~he s=Lridelv prac:~iced 3dB power combining me'.hods. For the weights shown the use of 11dB combiners for columns c and f together with 7 dB combiners for columns d and e reduces the combing loss from 3 dB to 0.7 dB (-45% to -14%
of available power). Once this principle is understood the skilled practitioner of the art will be able to determine the optimal combining ratios for any required power distribution.
Figure 2 is an illustration of the beamformer for the split-sector array using the weights of Tables 2 and 3.
The elements are numbered a through h, with c, d, e and f being the centermost columns containing the majority of the radiated power between the two beams. The signals for the two beams enter through the sector 1 and sector 2 ports respectively, and are divided out as shown using the weights described in Tables 2 and 3 , to excite elements a through h.
The description of this invention has relied on the use of column weighting to provide an example of the invention. However, the skilled practitioner in the art will recognize that the same approach could be applied to row weighting with significant benefit.
Other embodiments consistent with the present invention will become apparent from consideration of the specification and the practice of the invention disclosed therein.
Shapiro Cohen No.: 1763P06CA01 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 (15)
EXCLUSIVE PROPERTY OR PRIVILEGE IS CLAIMED ARE:
WE CLAIM:
1. An antenna array comprising a plurality of antenna elements for use in association with a plurality of beamformed antenna patterns each having a significant proportion of its radiated power concentrated in a subset of its constituent elements, wherein corresponding elemental powers of each of the plurality of patterns in the subset are combined together in a first manner while the remaining elemental powers of each of the plurality of patterns are combined with the corresponding elemental powers of each of the other of the plurality of patterns in a second manner, wherein a loss of total radiated power due to combining in the first manner of the elemental powers of each of the plurality of patterns in the subset is less than a loss of total radiated power due to combining in the second manner of all of the elemental powers of each of the plurality of patterns.
2. An antenna array according to claim 1, wherein the proportion is greater than 70%.
3. An antenna array according to claim 1, wherein the proportion is at least 80%.
4. An antenna array according to claim 1, wherein the number of elements in the subset is an exponent of 2.
5. An antenna array according to claim 1, wherein, for a number of elements in the subset that is an exponent of 2, the beams generated by the array are substantially mutually orthogonal.
6. An antenna array according to claim 5, wherein the substantially mutually orthogonal beams are generated for each of the plurality of patterns by a pseudo-Butler matrix of the same order as the exponent of 2.
7. An antenna array according to claim 6, wherein weighting coefficients of the elements other than the substantially mutually orthogonal beams are adjusted to compensate for any deviation between the elements generated by the pseudo-Butler matrix and a desired value for weighting coefficients of the substantially mutually orthogonal beams.
8. An antenna array according to claim 5, wherein the number of substantially mutually orthogonal beams is 2.
9. An antenna array according to claim 1, wherein a number of beams comprising each of the plurality of patterns exceeds a total number of antenna elements in the array divided by the number of the plurality of beam patterns.
10. An antenna array according to claim 1, wherein the antenna elements are organized in columns.
11. An antenna array according to claim 10, wherein the antenna elements are organized in 8 columns.
12. An antenna array according to claim 11, wherein each of the plurality of patterns comprises 8 columns.
13. An antenna array according to claim 11, wherein each of the plurality of patterns comprises 5 columns.
14. An antenna array according to claim 11, wherein each of the plurality of patterns comprises 6 columns.
15. An antenna array according to claim 11, wherein each of the columns comprises 12 elements.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002540220A CA2540220A1 (en) | 2006-03-17 | 2006-03-17 | Split-sector array |
| PCT/CA2007/000422 WO2007106984A1 (en) | 2006-03-17 | 2007-03-16 | Method and apparatus for reducing combining losses in a multi-beam antenna array |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002540220A CA2540220A1 (en) | 2006-03-17 | 2006-03-17 | Split-sector array |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2540220A1 true CA2540220A1 (en) | 2007-09-17 |
Family
ID=38520888
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002540220A Abandoned CA2540220A1 (en) | 2006-03-17 | 2006-03-17 | Split-sector array |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA2540220A1 (en) |
| WO (1) | WO2007106984A1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20100120441A1 (en) * | 2007-03-22 | 2010-05-13 | Telefonaktiebolaget Lm Ericsson | Increasing a sectorization order in a first sector of an antenna array |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1676338B1 (en) * | 2003-10-23 | 2017-12-06 | Telecom Italia S.p.A. | Antenna system and method for configuring a radiating pattern |
| US7664533B2 (en) * | 2003-11-10 | 2010-02-16 | Telefonaktiebolaget Lm Ericsson (Publ) | Method and apparatus for a multi-beam antenna system |
-
2006
- 2006-03-17 CA CA002540220A patent/CA2540220A1/en not_active Abandoned
-
2007
- 2007-03-16 WO PCT/CA2007/000422 patent/WO2007106984A1/en active Application Filing
Also Published As
| Publication number | Publication date |
|---|---|
| WO2007106984A1 (en) | 2007-09-27 |
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