Abstract:
A method is provided of identifying an antenna, by the steps of: providing the antenna with an identifying radiofrequency identification RFID circuit, connecting one end of a cable to the antenna, connecting the other end of the cable to a remote unit, sending a trigger signal to the RFID circuit, receiving by the remote unit via the cable a response signal from the RFID circuit, and decoding the response signal so as to identify the antenna.

Description:
FIELD OF THE INVENTION  
       [0001]    The present invention relates to telecommunications, in particular to wireless telecommunications. 
       DESCRIPTION OF THE RELATED ART 
       [0002]    In deploying mobile phone base stations at a site, a ground-based unit usually needs to be connected to tower- or mast-mounted antennas by transmission lines such as coaxial cables. Correct connection between input/output ports of the ground-based unit and the antennas is crucial to successful operation of the base station, but connections are often mixed up. If such incorrect connections occur, an engineer must make a repeat visit to the site to deal with the problem. In order to see which cable is connected to which antenna, the engineer must usually climb the tower or use lifting equipment such as a crane. Furthermore, the base station is unusable until the antennas are correctly connected. 
         [0003]    The known approach to avoiding incorrect connection is to colour code, or label, the cables and corresponding antennas. These approaches have disadvantages. 
       SUMMARY OF THE INVENTION  
       [0004]    The present invention is defined n the independent claims, to which the reader is now referred. Preferred features are laid out in the dependent claims. 
         [0005]    An example of the present invention is a method of identifying an antenna by the steps of: providing the antenna with an identifying radiofrequency identification RFID circuit, connecting one end of a cable to the antenna, connecting the other end of the cable to a remote unit, sending a trigger signal to the RFID circuit, receiving by the remote unit via the cable a response signal from the RFID circuit, and decoding the received response signal so as to identify the antenna. 
         [0006]    This approach allows remote identification from the ground of elevated antennas. The remote unit can be a base unit, for example at ground level. This remote identification is particularly useful if an incorrect connection has occurred. 
         [0007]    The existing cable connection to an antenna is made use of. Other connections such as data busses or optical fibre links are not required. 
         [0008]    By communicating with RF-ID tags in antennas via cables, the antennas can be distinguished, for example, during installation and when in use. This aids correct installation and operation of a base station. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    Embodiments of the present invention will now be described by way of example and with reference to the drawings, in which: 
           [0010]      FIG. 1  is a diagram illustrating a base station for wireless telecommunications according to a first embodiment of the invention, 
           [0011]      FIG. 2  is a diagram illustrating how, in the base station shown in  FIG. 1 , an antenna is connected to a transceiver on the ground, 
           [0012]      FIG. 3  is a schematic cross-sectional partial view illustrating an RF-ID tag within the antenna shown in  FIG. 2 , 
           [0013]      FIG. 4  is a diagram illustrating connection of a test apparatus to the antenna so as to read the RF-ID tag, 
           [0014]      FIG. 5  is a diagram illustrating a second embodiment having an add-on RF-ID tag connected between an antenna and coaxial cable. 
       
    
    
       [0015]    The drawings are not to scale but are schematic representations. 
       DETAILED DESCRIPTION  
       [0016]    An example base station and its antenna are first described. Then an example method of reading the RFID tag in the antenna is explained. After that, some alternative examples are considered. 
       The Base Station 
       [0017]    As shown in  FIG. 1 , an example base station  2 , which happens to be of Universal Mobile Telecommunications System (UMTS) type, consists of a control module  4  including control circuitry  6  and an interface  8  to the public phone network (not shown). The control module is connected to transceivers  10 , themselves each connected to a corresponding antenna assembly  12 . 
         [0018]    A cell (not shown), also referred to as a sector, is the radio-coverage area served by a corresponding antenna assembly  12  of the base station  2 . The base station typically has three cells, each covered by one of three antenna assemblies  12  that are directional, angled at 120 degrees to each other in azimuth. Each antenna assembly  12  consists of two antennas  14 , each of which is, for example, polarized in a single direction orthogonal to that of the other antenna  14  in the same antenna assembly  12 , so as to make use of so-called antenna diversity. Each antenna includes an RF-ID circuit  35  explained in more detail below. 
         [0019]    Each transceiver  10  includes a test apparatus  11  described in more detail below. 
         [0020]    As will be seen in  FIG. 1 , there are six cables  16  between the antennas  14  and transceivers  10  in the base station  2 . 
         [0021]    As shown figuratively in  FIG. 2 , the transceivers  10  are located at ground level, whereas the antennas  14  are located at elevated positions, typically 10 to 30 metres above ground, such as on high buildings or towers, such as on a mounting post  18  at the top of a tower (not shown). Each cable  16  is a coaxial cable. 
       Antennas 
       [0022]    An RF-ID tag is coupled to the input port of the antenna, for use in identification of the antenna. 
         [0023]    Referring to  FIG. 3 , the antenna  14  includes a housing, a part  18  of which is shown in the Figure. That part  18  of the housing includes an input/output port  20 , to which an end connector  22  of the coaxial cable  16  is connected. The coaxial cable  16  includes an inner conductor  24 , an outer conductor  26  and a dielectric material  28  in between. The outer conductor  26  contacts the part  18  of the housing. The inner conductor  24  is connected to a stripline conductor  30  which includes a connecting portion  32  having a recess  33  to fit an end  34  of the inner conductor  24  for good electrical connection. 
         [0024]    A radio frequency identification, RF-ID, circuit  35  consists of a known RF-ID tag  36  and a directional coupler  38 , by which the tag  36  is coupled to the stripline conductor  30 . In this example embodiment inductive coupling is used. 
         [0025]    Dependent upon the type of RF-ID tag, coupling of the tag to the transmission line, such as stripline, within the antenna can be done by inductive coupling, capacitive coupling, resistive coupling or a combination thereof. 
         [0026]    In this embodiment, the RF-ID tag  36  is of a passive nature, of known type, as used, for example in known warehouse inventory systems. The RF-ID tag responds to a trigger signal sent up to the antenna via the coaxial cable  16  to send a response signal down via the coaxial cable  16 . The response signal includes identification in the form of an antenna identification number. The response signal also includes information about the antenna, namely frequency range, gain, and polarisation, which can be used to monitor the operation of the base station. 
         [0027]    In some other embodiments, the RF-ID tag  36  is of an active nature, making use of direct current, DC, power supplied by the coaxial cable  16 . 
       Reading the Tag 
       [0028]    As shown in  FIG. 1 , a test apparatus  11  in a transceiver  10  sends a radio frequency trigger signal to the antenna  14  connected via a coaxial cable  16  to the transceiver  10 . The trigger signal is at a different frequency to both the transmit band and the receive band of the transceiver  10  so as to ensure that the trigger signal does not get radiated by the antenna nor get treated as a received signal. This ensures compliance with requirements regarding such unwanted emissions. 
         [0029]    This trigger signal triggers the response signal from the RF-ID tag  36 . The tag  36  is coupled by the directional coupler  38  such that there is no substantial impairment to normal antenna operation. As mentioned previously, the response signal includes an antenna identification number which can be considered as an individual signature identifying the antenna. 
         [0030]    A response signal is, of course, an identifier that the coaxial cable  16  is properly connected between a transceiver and antenna. 
         [0031]    Normally response signals will includes the identification number of the antenna to which a transceiver is expected to be connected. However if an “incorrect” antenna is identified, remedial action is taken. For example, during installation of the base station  2 , the installation technician on the ground can identify which antenna  14  is connected to which coaxial cable  16 . This aids correct connection of antennas to transceivers. 
         [0032]    Secondly, after installation such that the base station is powered up and in operation, triggering the RF tag provides useful information for maintenance purposes. For example the failure to receive a response signal could indicate that an antenna to which the trigger signal is sent is not properly connected. Correct responses from some antennas but not others could help to pin-point where in the base station a faulty component lies. In consequence, so-called base station down-time, during which repairs are effected, can be reduced. 
         [0033]    The RF-ID tags enable antennas to be identified from the ground. 
       Alternative Test Apparatus for Use During Base Station Installation 
       [0034]    In installing a base station, coaxial cables connected to antennas are identified by a human installer on the ground so as to work out to which transceiver each coaxial cable should be connected. To do this, as shown in  FIG. 4 , the installer connects a handheld tester unit  11 ′ to the end of the coaxial cable  16 ′ distal from the antenna  14 ′. The handheld tester unit  11 ′ includes a test signal generator  60 , a reply signal decoder  62  and a visual display screen  64 . The test signal generator  60  generates a trigger signal. The trigger signal is sent up the coaxial cable  16 ′ and it is that signal to which the RF-ID circuit  35 ′in the antenna  14 ′ responds. The response signal is decoded in a decoder  62  to provide an antenna identification number that is displayed on the screen  64 . 
       Other Embodiments 
       [0035]    As shown on  FIG. 5 , as an alternative to having the RF-ID circuit within the antenna housing, the RF-ID circuit  35 ″ is placed in an add-on unit  40 . 
         [0036]    The add-on unit  40  comprises a threaded cylindrical outer conductor  42  having a cylindrical outer shoulder  44  portion, which, when fitted, abuts the female connector end  45  of the coaxial cable  16 ″. 
         [0037]    The add-on unit  40  also includes an inner conductor element  46  held in position relative to the outer conductor  42  by a dielectric material  48 . The inner conductor element  46  includes a base portion  50  and a top portion  54 . The base portion  50  includes a cylindrical recess  52  shaped to fit over, and electrically connect with, the end of the inner conductor  32 ′ of the coaxial cable  16 ′. The top portion  54  is a cylindrical conductor. 
         [0038]    In use, the top portion  54  is connected to a stripline conductor  30 ′ which includes a connection portion  32 ′ having a recess  33 ′ to fit said top portion  54  with good electrical connection. 
         [0039]    As shown in  FIG. 5 , the antenna  14 ′ includes a housing, part  18 ′ of which is shown that includes an input/output port  20 ′ threaded and shaped for cooperative inter-engagement with a cylindrical inner shoulder portion  56  of the add-on unit  40 . 
         [0040]    The RF-ID circuit  35 ″ consists of an RF-ID tag  36 ′ of known type and a coupler such as a directional coupler  38 ′ by which the tag  36 ′ is coupled to the top portion  54  of the inner conductor element  46 . 
         [0041]    In some other, otherwise similar, embodiments (not shown) other types of cable are used in place of stripline, for example waveguide or coaxial cable. The stripline conductor  30 ,  30 ′ can be replaced by a coaxial inner conductor. 
         [0042]    In some embodiments, the trigger signal may be in the transmit band and/or receive band of the antenna rather than outside these bands. 
         [0043]    In some embodiments, the base station is a CDMA2000 base station or another type of base station for wireless telecommunications. Base stations can be of various standards and frequency bands. 
         [0044]    In some embodiments, the antennas are dual-band antennas with connectors in each band. In some embodiments, a single, dual polarised, antenna is used in each cell so as to exploit antenna diversity. 
         [0045]    In some embodiments, the antenna is intelligent, and other intelligent elements in the system include apparatus to remotely identify antennas having RF-ID tags, and then address control signals to those antennas. This enables automatic discovery and configuration processes in intelligent systems, including monitoring of antenna operation to determine whether an antenna is operating correctly. 
         [0046]    In some embodiments, rather than the cable being a coaxial cable or stripline, the cable can by some other type of transmission line or waveguide. 
       General 
       [0047]    The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.