Patent Publication Number: US-8988308-B2

Title: Wireless communication node with antenna arrangement for dual band reception and transmission

Description:
This application claims the benefit of U.S. Provisional Patent Application No. 61/694,397 filed on Aug. 29, 2012; this application is also a continuation of International Patent Application No. PCT/EP2012/069524, filed on Oct. 3, 2012, which designates the U.S. The above identified applications are incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     This disclosure relates to a node in a wireless communication network, where the node comprises an antenna arrangement. The antenna arrangement in turn comprises at least one antenna column, where each antenna column comprises a first set of subarrays and a second set of subarrays. Each set of subarrays comprises at least two subarrays, and each subarray in turn comprises at least one antenna element. The first set of subarrays comprises antenna elements having a first polarization and the second set of subarrays comprises antenna elements having a second polarization, where the first polarization and the second polarization are mutually orthogonal. 
     BACKGROUND 
     In a wireless communication networks, there are communication nodes, for example base stations. The base stations normally comprise sector-covering antenna arrangements. Such an antenna arrangement comprises a number of antenna ports corresponding to branches for uplink and downlink, where downlink denotes transmission, TX, from the base station to other nodes such as mobile terminals, and uplink denotes reception, RX, to the base station from other nodes such as mobile terminals. A downlink branch is thus a TX branch and an uplink branch is thus an RX branch. 
     Normally a typical system configuration may comprise two TX branches in the form of transmission channels and two RX branches in the form of reception channels, but system configurations with two TX branches and four RX branches are more attractive since the additional two RX branches provide large uplink improvements for a relatively small cost and volume increase. However, two additional antenna ports are required in the antenna arrangement. 
     An even more complex antenna arrangement is required when two TX and four RX branches on a frequency band shall be combined with two TX and four RX branches from another frequency band. 
     The most common configuration existing today for such a dual-band antenna arrangement, with two TX branches and four RX branches, is a dual-column antenna with individual tilt for all antenna ports and frequencies. This can be accomplished by placing diplexers after the antenna elements and having individual phase shifters for each frequency band and polarization. 
     Existing solutions for such a dual-band antenna arrangement, with two TX branches and four RX branches, based on compact dual column antennas, thus require one diplexer per antenna subarray and polarization. For example, a standard antenna may feature 4-9 subarrays and two polarizations per antenna column. This means that dual column antenna contains 16-36 diplexers and 8 phase shifters. It is a problem to be able to fit all these components without adding a significant volume increase of the antenna, especially for bands with a small frequency separation. 
     There is thus a need for a less complicated dual-band antenna arrangement in a node, where the antenna arrangement in its least complicated form has two transmission channels and four reception channels. In a typical case, the antenna arrangement has four transmission channels and eight reception channels. 
     SUMMARY 
     It is one object of some embodiments to provide a dual-band antenna arrangement in a node, where the antenna arrangement at least has two transmission channels and four reception channels, and where the dual-band antenna arrangement is less complicated than what is previously known. 
     The object is obtained, in some embodiments, by means of a node in a wireless communication network, where the node comprises an antenna arrangement. The antenna arrangement in turn comprises at least one antenna column, where each antenna column comprises a first set of subarrays and a second set of subarrays. Each set of subarrays comprises at least two subarrays, and each subarray in turn comprises at least one antenna element. The first set of subarrays comprises antenna elements having a first polarization and the second set of subarrays comprises antenna elements having a second polarization, where the first polarization and the second polarization are mutually orthogonal. Each first set of subarrays is connected to a corresponding first filter device via a first corresponding phase altering device, and each second set of subarrays is connected to a corresponding second filter device via a second corresponding phase altering device. Each filter device has a respective combined port connected to the corresponding phase altering device and being associated with signals at a first frequency band and signals at a second frequency band. These frequency bands are spectrally separated from each other. Each filter device further has a respective first filter port and a respective second filter port. Each filter device is arranged to separate signals at the first frequency band and signals at the second frequency band between the respective combined port and the respective filter ports such that each first filter port is arranged for transmission and reception of signals at one frequency band, and each second filter port is arranged for reception of signals at the other frequency band. 
     According to an example, the node comprises a first antenna column and a second antenna column which are physically separated from each other. 
     According to another example, for each antenna column, the first filter ports are connected to different transmission channels. 
     According to another example, there is a first transmission channel and a second transmission channel. The first transmission channel is associated with the first polarization and the second transmission channel is associated with the second polarization. 
     According to another example, for each antenna column, the first filter ports are connected to different reception channels and the second filter ports are connected to different reception channels. 
     More examples are disclosed in the dependent claims. 
     A number of advantages are obtained by means of the embodiments. Mainly a less complicated dual-band antenna arrangement is obtained, where the antenna arrangement in its least complicated form has two transmission channels and four reception channels. In a typical case, the antenna arrangement has four transmission channels and eight reception channels. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments will now be described more in detail with reference to the appended drawings, where: 
         FIG. 1  shows a schematic side view of a node in a wireless communication network. 
         FIG. 2  shows a schematic view of an antenna arrangement according to some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIG. 1 , there is a node  1  in a wireless communication network, the node comprising an antenna arrangement  60 . 
     With reference to  FIG. 2 , the antenna arrangement  60  comprises a first antenna column  2  and a second antenna column  3 . The antenna columns  2 ,  3  are physically separated from each other by a distance d in an azimuth direction A and have respective main extensions in an elevation direction E, where the azimuth direction A and the elevation direction E are mutually orthogonal. The antenna columns  2 ,  3  are arranged to radiate and/or receive signals by means of antenna radiation lobes  79 ,  80  in a well-known manner, as schematically indicated with dash-dotted lines in  FIG. 1 . 
     Each antenna column  2 ,  3  comprises a corresponding first set of subarrays  4 ;  6  and a corresponding second set of subarrays  5 ;  7 . Each set of subarrays  4 ,  5 ,  6 ,  7  is indicated with a dash-dotted line. 
     The first set of subarrays  4  of the first antenna column  2  comprises four sub-arrays  4   a ,  4   b ,  4   c ,  4   d  and the second set of subarrays  5  of the first antenna column  2  comprises four further sub-arrays  5   a ,  5   b ,  5   c ,  5   d . Each subarray of the first set of subarrays  4  of the first antenna column  2  comprises two antenna elements  8 ,  9 ;  10 ,  11 ;  12 ,  13 ;  14 ,  15  having a first polarization P1. Furthermore, each subarray of the second set of subarrays  5  of the first antenna column  2  comprises two corresponding antenna elements  16 ,  17 ;  18 ,  19 ;  20 ,  21 ;  22 ,  23  having a second polarization P2, where the first polarization P1 and the second polarization P2 are mutually orthogonal. 
     In the same way, the first set of subarrays  6  of the second antenna column  3  comprises four sub-arrays  6   a ,  6   b ,  6   c ,  6   d  and the second set of subarrays  7  of the second antenna column  3  comprises four further sub-arrays  7   a ,  7   b ,  7   c ,  7   d . Each subarray of the first set of subarrays  6  of the second antenna column  3  comprises two antenna elements  24 ,  25 ;  26 ,  27 ;  28 ,  29 ;  30 ,  31  having the first polarization P1. Furthermore, each subarray of the second set of subarrays  7  of the second antenna column  3  comprises two corresponding antenna elements  32 ,  33 ;  34 ,  35 ;  36 ,  37 ;  38 ,  39  having the second polarization P2. Each sub-array  4   a ,  4   b ,  4   c ,  4   d ;  5   a ,  5   b ,  5   c ,  5   d ;  6   a ,  6   b ,  6   c ,  6   d ,  7   a ,  7   b ,  7   c ,  7   d  is indicated with a dashed line. 
     According to some embodiments, the first set of subarrays  4  of the first antenna column  2  is connected to a first diplexer  40  via a first phase shifter  42 , the first phase shifter  42  thus having four antenna side ports  61 , indicated schematically with a dashed line, connected to the first set of subarrays  4  of the first antenna column  2 , and one diplexer side port  62  connected to a combined port  48  of the first diplexer  40 . The first diplexer  40  in turn further comprises a first filter port  52  and a second filter port  53 . 
     In the same way, the second set of subarrays  5  of the first antenna column  2  is connected to a second diplexer  41  via a second shifter  43 , the second phase shifter  43  thus having four antenna side ports  63 , indicated schematically with a dashed line, connected to the first set of subarrays  5  of the first antenna column  2 , and one diplexer side port  64  connected to a combined port  49  of the second diplexer  41 . The second diplexer  41  in turn further comprises a first filter port  54  and a second filter port  55 . 
     The second antenna column  3  comprises a corresponding arrangement which will be described more briefly. The second antenna column  3  comprises a third diplexer  44 , having a combined port  50 , a first filter port  56  and a second filter port  57 , the second antenna column  3  further comprising a fourth diplexer  45  having a combined port  51 , a first filter port  58  and a second filter port  59 . The combined ports  50 ,  51  are connected to corresponding third and fourth phase shifters  46 ,  47  via corresponding diplexer side ports  65 ,  67  at the phase shifters  46 ,  47 . Each of the third and fourth phase shifter  46 ,  47  is further connected to corresponding subarrays  6   a ,  6   b ,  6   c ,  6   d ;  7   a ,  7   b ,  7   c ,  7   d  via corresponding four antenna side ports  66 ,  68 , indicated schematically with dashed lines. 
     The combined ports  48 ,  49 ,  50 ,  51  of the diplexers  40 ,  41 ;  44 ,  45  are associated with signals at a first frequency band f 1  and signals at a second frequency band f 2 , where the frequency bands f 1 , f 2  are spectrally separated from each other. More in detail, the combined ports  48 ,  49 ,  50 ,  51  of the diplexers  40 ,  41 ;  44 ,  45  are arranged for reception and transmission of signals at the first frequency band f 1  and the second frequency band f 2 . 
     The diplexers  40 ,  41 ;  44 ,  45  are in a known way arranged to separate signals at the first frequency band f 1  and signals at the second frequency band f 2  between the respective combined port  48 ,  49 ,  50 ,  51  and the respective filter ports  52 ,  53 ,  54 ,  55 ;  56 ,  57 ,  58 ,  59  such that each first filter port  52 ,  54 ;  56 ,  58  is arranged for transmission and reception of signals at one frequency band f 1 , f 2 , and each second filter port  53 ,  55 ;  57 ,  59  is arranged for reception of signals at the other frequency band f 2 , f 1 . As an example, if each first filter port  52 ,  54 ;  56 ,  58  is arranged for transmission and reception of signals at the first frequency band f 1 , each second filter port  53 ,  55 ;  57 ,  59  is arranged for reception of signals at the second frequency band f 2 . 
     The filter ports  52 ,  53 ;  54 ,  55 ;  56 ,  57 ;  58 ,  59  also constitute antenna ports, since these ports  52 ,  53 ;  54 ,  55 ;  56 ,  57 ;  58 ,  59  are an interface to the antenna columns  2 ,  3 . 
     Since the phase shifters  42 ,  43 ;  46 ,  47  are positioned between the diplexers  40 ,  41 ;  44 ,  45  and the antenna elements  8 ,  9 ;  10 ,  11 ;  12 ,  13 ;  14 ,  15 ;  16 ,  17 ;  18 ,  19 ;  20 ,  21 ;  22 ,  23 ;  24 ,  25 ;  26 ,  27 ;  28 ,  29 ;  30 ,  31 ;  32 ,  33 ;  34 ,  35 ;  36 ,  37 ;  38 ,  39 , only four diplexers and four phase shifters are needed in this example instead of 16-32 diplexers and 8 phase shifters, as mentioned initially. 
     The first filter ports  52 ,  54 ;  56 ,  58  are connected to a first transceiver device  69  via a corresponding first branch  71 , third branch  73 , fifth branch  75  and seventh branch  77 . In the same way, the second filter ports  53 ,  55 ;  57 ,  59  are connected to a second transceiver device  70  via a corresponding second branch  72 , fourth branch  74 , sixth branch  76  and eighth branch  78 . The first transceiver device  69  is arranged for reception and transmission at the first frequency band f 1 , and the second transceiver device  70  is arranged for reception and transmission at the second frequency band f 2 . 
     The first filter ports  52 ,  54 ;  56 ,  58  are further arranged for both transmission and reception. Each one of the first branch  71  and the fifth branch  75  is connected to a first transmission channel TX1 and to a first reception channel RX1. Furthermore, each one of the third branch  73  and the seventh branch  77  is connected to a second transmission channel TX2 and to a second reception channel RX2. 
     In this way, the first branch  71  is connected to the first transmission channel TX1 and to the first reception channel RX1 at the first frequency band f 1  and the third branch  73  is connected to the second transmission channel TX2 and to the second reception channel RX2 at the first frequency band f 1 . Furthermore, the fifth branch  75  is connected to the first transmission channel TX1 and to the first reception channel RX1 at the second frequency band f 2 , and the seventh branch  77  is connected to the second transmission channel TX2 and to the second reception channel RX2 at the second frequency band f 2 . 
     The second filter ports  53 ,  55 ;  57 ,  59  are arranged for reception. Each one of the second branch  72  and the sixth branch  76  is connected to a third reception channel RX3, and each one of the fourth branch  74  and the eighth branch  78  is connected to a fourth reception channel RX4. 
     In this way, the second branch  72  is connected to the third reception channel RX3 at the second frequency band f 2  and the fourth branch  74  is connected to the fourth reception channel RX4 at the second frequency band f 2 . Furthermore, the sixth branch  75  is connected to the third reception channel RX3 at the first frequency band f 1 , and the eighth branch  78  is connected to the fourth reception channel RX4 at the first frequency band f 1 . 
     This means that as a total there are two transmission channels TX1, TX2 and four reception channels RX1, RX2, RX3, RX4. By means of the diplexers  40 ,  41 ,  44 ,  45 , reception of two different frequency bands f 1 , f 2  is possible for each set of subarrays  4 ,  5 ,  6 ,  7 . For each antenna column  2 ,  3 , the two sets of subarrays  4 ,  5 ,  6 ,  7  receive on different reception channels RX1, RX3; RX2, RX4 which enables polarization diversity. This is however not necessary for the present invention, but constitutes an advantageous configuration. It is, however, necessary that, for each diplexer  40 ,  41 ,  44 ,  45 , one filter port  52 ,  54 ,  56 ,  58  is connected to both a reception channel and a transmission channel of one frequency band, and that the other filter port  53 ,  55 ,  57 ,  59  is connected to a reception channel of another frequency band. 
     By placing the two transmission channels TX1, TX2 for the first frequency band f 1  on the first antenna column  2  and the two transmission channels TX1, TX2 for the second frequency band f 2  on the second antenna column  3 , individual tilt is achieved on downlink, which is important for limiting downlink interference between cells. 
     The additional third reception channel RX3 and fourth reception channel RX4 of the first frequency band f 1  will get the same tilt as the transmission channels TX1, TX2 for second frequency band f 2 , and vice versa. This has a limited system impact regarding the total reception performance assuming that the tilt settings between the first frequency band f 1  and the second frequency band f 2  are not completely different. 
     The present invention is not limited to the above, but may vary within the scope of the appended claims. For example, it is conceivable that there only is one antenna column. In the least complicated form of the present invention, each antenna column comprises at least two subarrays, where each subarray comprises one antenna element. 
     The polarizations may have any directions, but should always be orthogonal. 
     When terms like orthogonal and parallel are used, these terms are not to be interpreted as mathematically exact, but within what is practically obtainable. 
     The first antenna elements  8 ,  16  and the second antenna elements  9 ,  17  of the first subarrays  4   a ,  5   a  of the first antenna column  2  are shown as separate antenna elements, but are practically often combined into two respective dual polarized antenna elements that share the same physical location, for example in the form of a cross. In the same way, in all opposing sets of subarrays  4   a ,  5   a ;  4   b ;  5   b ;  4   c ,  5   c ;  4   d ;  5   d ;  6   a ,  7   a ;  6   b ,  7   b ;  6   c ,  7   c ;  6   d ,  7   d  the antenna elements may form dual polarized antenna elements, each dual polarized antenna element  4   a ,  4   b ,  4   c ,  4   d ;  5   a ,  5   b ,  5   c ,  5   d  being arranged for transmission and reception of the first polarization P1 and the second polarization P2. 
     The polarizations P1, P2 are shown to be perpendicular to the schematically indicated antenna elements  8 ,  9 ;  10 ,  11 ;  12 ,  13 ;  14 ,  15 ;  16 ,  17 ;  18 ,  19 ;  20 ,  21 ;  22 ,  23 ;  24 ,  25 ;  26 ,  27 ;  28 ,  29 ;  30 ,  31 ;  32 ,  33 ;  34 ,  35 ;  36 ,  37 ;  38 ,  39 , which is the case for antenna elements in the form of slots, but this is only by way of example. For dipole antenna elements, the polarizations P1, P2 are parallel to the antenna elements, and for patch antenna elements, the polarization runs in a direction along the patch in dependence of its feeding. 
     In the above, the term branch  71 ,  72 ,  73 ,  74 ,  75 ,  76 ,  77 ,  78  may comprise several signal connections. The transmission channels TX and reception channels TX may be regarded as transmission branches and reception branches corresponding to said signal connections. 
     The phase shifters  42 ,  43 ;  46 ,  47  may be constituted by any suitable phase altering devices, and the diplexers  40 ,  41 ;  44 ,  45  may be constituted by any suitable filter devices. 
     Generally, the antenna arrangement  60  comprises at least one antenna column  2 ,  3 , each antenna column  2 ,  3  comprising a first set of subarrays  4 ;  6  and a second set of subarrays  5 ;  7 . Each set of subarrays  4 ,  5 ;  6 ,  7  comprises at least two subarrays  4   a ,  4   b ,  4   c ,  4   d ;  5   a ,  5   b ,  5   c ,  5   d ;  6   a ,  6   b ,  6   c ,  6   d ;  7   a ,  7   b ,  7   c ,  7   d , and each subarray  4   a ,  4   b ,  4   c ,  4   d ;  5   a ,  5   b ,  5   c ,  5   d ;  6   a ,  6   b ,  6   c ,  6   d ;  7   a ,  7   b ,  7   c ,  7   d  in turn comprises at least one antenna element  8 ,  9 ;  10 ,  11 ;  12 ,  13 ;  14 ,  15 ;  16 ,  17 ;  18 ,  19 ;  20 ,  21 ;  22 ,  23 ;  24 ,  25 ;  26 ,  27 ;  28 ,  29 ;  30 ,  31 ;  32 ,  33 ;  34 ,  35 ;  36 ,  37 ;  38 ,  39 . The first set of subarrays  4 ;  6  comprises antenna elements  8 ,  9 ;  10 ,  11 ;  12 ,  13 ;  14 ,  15 ;  24 ,  25 ;  26 ,  27 ;  28 ,  29 ;  30 ,  31  having the first polarization P1, and the second set of subarrays  5 ;  7  comprises antenna elements  16 ,  17 ;  18 ,  19 ;  20 ,  21 ;  22 ,  23 ;  32 ,  33 ;  34 ,  35 ;  36 ,  37 ;  38 ,  39  having the second polarization P2. 
     Each first set of subarrays  4 ;  6  is connected to a corresponding first filter device  40 ,  44  via a first corresponding phase altering device  42 ,  46 , and each second set of subarrays  5 ;  7  is connected to a corresponding second filter device  41 ,  45  via a second corresponding phase altering device  43 ,  47 . Each filter device  40 ,  41 ;  44 ,  45  has a respective combined port  48 ,  49 ,  50 ,  51  connected to the corresponding phase altering device  42 ,  43 ;  46 ,  47  and is associated with signals at the first frequency band f 1  and signals at the second frequency band f 2 . Each filter device  40 ,  41 ;  44 ,  45  further has a respective first filter port  52 ,  54 ;  56 ,  58  and a respective second filter port  53 ,  55 ;  57 ,  59 . Each filter device  40 ,  41 ;  44 ,  45  is arranged to separate signals at the first frequency band f 1  and signals at the second frequency band f 2  between the respective combined port  48 ,  49 ,  50 ,  51  and the respective filter ports  52 ,  53 ,  54 ,  55 ;  56 ,  57 ,  58 ,  59 , such that each first filter port  52 ,  54 ;  56 ,  58  is arranged for transmission and reception of signals at one frequency band and each second filter port  53 ,  55 ;  57 ,  59  is arranged for reception of signals at the other frequency band.