Abstract:
The invention concerns a telecommunications mast installation ( 10 ), typically a base station in a cellular telephone network, which includes a mast ( 14 ) supporting a telecommunications antenna ( 16 ). A foundation structure ( 12 ) supports the mast. The foundation structure is in the form of an enclosed chamber ( 24 ) situated at least partially underground and defining an internal space which is accessible to personnel and which accommodates electronic equipment associated with operation of the antenna. For aesthetic and security reasons, it is preferred that the chamber ( 24 ) be competely underground.

Description:
[0001]    THIS invention relates to a telecommunications mast installation.  
           [0002]    The invention is particularly concerned with a telecommunications mast installation in which a telecommunications mast supports one or more elevated antennas. The mast itself may be of monopole, lattice or other construction and may be made of steel or other materials. A typical example where the invention finds application is in the base station installations of cellular telephone networks.  
           [0003]    Commonly a cellular telephone network base station installation includes a fenced or otherwise externally secured area in which are located an antenna-supporting mast supported on its own foundation and an exposed building alongside the mast which houses necessary electronic and other equipment, associated with the operation of the antenna including, for example, radio transmission and reception equipment.  
           [0004]    It is recognised that base station installations of the type described above are extremely unsightly. In an attempt to address this problem, antenna-supporting masts have in the past been disguised as trees. Although this goes some way to addressing the problem, it still does not address the unsightliness of the external fencing and the building which accommodates the antenna-related equipment.  
         SUMMARY OF THE INVENTION  
         [0005]    According to the present invention there is provided a telecommunications mast installation comprising a mast supporting a telecommunications antenna and a foundation structure supporting the mast, the foundation structure being in the form of an enclosed chamber situated at least partially, and preferably fully, underground and defining an internal space which is accessible to personnel and which accommodates electronic equipment associated with operation of the antenna.  
           [0006]    In the preferred embodiments, the mast has a foot at its lower end which is supported on a base of the chamber, the base acting as a structural foundation for the mast. Typically in such embodiments, the foot of the mast is received by a seat in or on the base, the seat restraining lateral movements of the foot of the mast at the base. The seat may be in the form of a recess in the base. Typically also, the chamber includes lateral support means to restrain lateral movements of the mast at a position above the base. The chamber will preferably have a roof, at or slightly below ground level, with an opening therein through which the mast passes. There may be a sleeve about a lower end of the mast, the sleeve being received by the seat and passing through the opening in the roof.  
           [0007]    In alternative, less preferred embodiments, the mast has a foot at its lower end which is connected rigidly to a roof of the chamber.  
           [0008]    In either type of embodiment, it will be understood that the chamber forms an integrated structure which supports the mast and that the construction thereof will be in accordance with accepted civil engineering principles bearing in mind firstly the expected vertical and lateral loading the requirement that there should be no flooding of the chamber in view of the equipment accommodated therein. With the latter requirement in mind it is preferred that external access to the chamber, for example for personnel should be via openings above ground level, as described below.  
           [0009]    The installation may include ventilation or air conditioning means for the interior of the chamber. In one version of the invention ventilation or air conditioning means are housed in a cubicle mounted on a roof of the chamber above ground level and communicating with the interior of the chamber. In other versions, the ventilation means may comprise a ventilation circuit which includes an air intake at an elevated position on the mast, an air exhaust at an elevated position on the mast, air intake ducting leading from the intake to the interior of the chamber and air exhaust ducting leading from the interior of the chamber to the air exhaust. In such versions it is preferred that the air exhaust be located towards the top of the mast and include an air extractor. It is also preferred that the mast be a hollow monopole mast with the air intake and air exhaust ducting is concealed in the interior of the mast.  
           [0010]    Personnel access to the interior of the chamber is required for equipment maintenance or installation or other purposes. The invention envisages an arrangement in which there is an entrance cubicle on a roof the chamber above ground and a personnel access passage leading from the entrance cubicle to the interior of the chamber. The invention also envisages an alternative arrangement in which the mast is a hollow monopole mast which extends into the chamber and which has personnel access openings into the mast above ground and within the chamber, the personnel access openings and the interior of the mast providing a personnel access passage to the chamber.  
           [0011]    The chamber will typically be of concrete, and possibly be at least partially of precast construction, although other materials and combinations or materials are within the scope of the invention.  
           [0012]    The mast may carry one or more transverse, electric light-supporting arms each at an elevated position with electrical supply cables for the or each arm extending along the mast. This configuration would be particularly useful in situations where the chamber is located underground in an area alongside a road or between opposing lanes of a road.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    The invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings in which:  
         [0014]    [0014]FIG. 1 shows, in partly cut away front view, an telecommunications mast installation in accordance a first embodiment of the invention;  
         [0015]    [0015]FIG. 2 shows the installation of FIG. 1 in a three dimensional, partly cut away view;  
         [0016]    [0016]FIG. 3 shows a view similar to that of FIG. 1 of another embodiment of the invention; and  
         [0017]    [0017]FIG. 4 shows a view similar to that of FIG. 2 of the embodiment of FIG. 3. 
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0018]    With reference to FIGS. 1 and 2 of the drawings, a telecommunications mast installation in accordance with a first embodiment of the invention is generally indicated by reference numeral  10 . The installation  10  comprises a foundation structure  12  which is beneath ground level indicated by reference numeral  18  and a mast  14  mounted on and supported by the structure  12 . The mast  14  extends vertically upwardly and an antenna  16  is mounted to the top of the mast.  
         [0019]    The structure  12  forms a hollow chamber. It includes a base  20  of reinforced concrete vvhich will typically have been cast in situ, although it may be a precast component. The chamber also includes a round cylindrical shell  22  supported on the base  20  and securely connected to the base to form an integral structure. The shell  22  is conveniently in the form of a precast structure, or is formed of precast components. The chamber formed within the shell is designated with the reference numeral  24 .  
         [0020]    A roof  26  formed by a roof slab spans across and is supported by the shell  22 . The roof  26  is securely connected to the shell and, together with the shell and base  20 , forms a rigid, three dimensional, composite foundation for the mast  14 .  
         [0021]    A vertical sleeve  32  extends snugly through a hole in the roof  26  and is itself snugly located about a lower end of the mast  14 . The lower end of the sleeve, coinciding with the lower extremity or foot of the mast  14 , is snugly received in a recessed seat  30  provided for that purpose in the base  20 . With this arrangement, vertical loading on the mast is transferred to the base  20  which serves as a structural foundation for the mast. In addition, the seat restrains lateral movements of the mast at the level of the base.  
         [0022]    The roof  26 , acting via an upper portion of the sleeve  32 , laterally restrains the mast  14  at a position spaced from and directly above the seat  30 . The structure  12  accordingly provides secure vertical and lateral support for the mast. It will however be understood that there is no rigid, moment-transferring connection between the mast and structure  12 .  
         [0023]    In other embodiments, not shown, the sleeve  32  may be omitted. In this case, the foot of the mast is received directly in the recessed seat  30 , and is laterally restrained thereby at the level of the base, and the roof  26  applies direct lateral restraint to the mast above the base.  
         [0024]    The interior of the chamber  24  accommodates electronic and other equipment  35  associated with the operation of the antenna  16  carried by the mast. A cubicle  36  exposed above ground level on the roof  26  provides an entrance to the chamber  24  to allow personnel access to the equipment accommodated within the chamber via a hatch  37  on the cubicle or via a door (not shown) in a side of the cubicle. In either event, it will be understood that the cubicle communicates with the chamber through an opening extending through the roof.  
         [0025]    In an alternative arrangement where the mast  14  is a hollow monopole, typically of steel, there may be a door or hatch in the wall of the pole above the upper end of the sleeve  32  and a corresponding door or hatch through the lower end of the mast and sleeve inside the chamber  24 , with the doors or hatches and the interior of the mast itself providing personnel access to the interior of the chamber. This arrangement does away with the need for an exposed, upstanding structure, i.e. the cubicle  36 , on the roof.  
         [0026]    The chamber  24  should be ventilated or air conditioned for the sake of the electronic equipment  35  and personnel working in the chamber  24 . In FIGS. 1 and 2 necessary air conditioning or ventilation components are housed in a further, ventilated cubicle  38  located in an exposed position on the roof  26 .  
         [0027]    In the embodiment of FIGS. 3 and 4, the shell  22  is rectangular in shape rather than round cylindrical as in the first embodiment. Another difference between this embodiment and that of FIGS. 1 and 2 is the manner in which chamber ventilation is provided. An air intake  40  is provided in the wall of the monopole mast  14  at a level just above the sleeve  32 . Inside the mast air intake ducting (not visible) is provided to take air to a vent  42  in the chamber. An inlet  44  in the chamber is connected via exhaust ducting in the mast  14  to an exhaust at the top of the mast. The exhaust includes is served by an air extractor  46 , typically a rotary air-driven extractor of conventional type, such as that marketed under the trade name “Whirlybird”. Alternatively, the extractor may be an electrically powered suction fan or the like. It will be appreciated that there is accordingly a ventilation circuit in which ventilating air is drawn into the chamber via the intake  40 , concealed intake ducting and vent  42  and is withdrawn from the chamber to the exhaust via the inlet  44  and concealed exhaust ducting.  
         [0028]    In the absence of a personnel access cubicle on the roof  26  in the embodiment of FIGS. 3 and 4, it will be understood that personnel access in this will typically be via the mast itself, as described above.  
         [0029]    In both embodiments described above the mast  14  supports transverse, light-supporting arms  50  at an elevated position. The lights  52  which are supported may, for instance, be street lights. Electricity supply cabling for the lights will typically be taken to the light fittings in concealed manner through the interior of the mast. In practice, electrical power, either mains or independently generated, will have to be supplied to the chamber  24  and equipment  35  therein, as well as air conditioning equipment if provided, and it will accordingly be a simple matter to route power from the main supply to the light fittings  52  on the arms  50 .  
         [0030]    The facility, to support street lighting renders installations as described above eminently suitable for location alongside roads. This is exemplified in FIG. 3, in which the opposing lanes of a highway are designated with the numeral  52  and the installation of the invention is located in the island or strip between those lanes. There may of course be only a single arm supporting a single light fitting.  
         [0031]    It will also be understood that the antenna  16  is connected in conventional fashion to the associated equipment in the chamber by conductors extending internally along the mast  14 .  
         [0032]    The installations described above have a number of advantages compared to conventional cellular telephone network base station installations as mentioned above. One important advantage is the fact that the installations are not visually intrusive because, even with an embodiment of the kind seen in FIGS. 1 and 2, the structure  12  is predominantly below ground and hence is largely invisible. The fact that the chamber is below ground also makes it possible to provide a telecommunications mast right next to a road or, as described above, in the inter-lane strip of a highway. In this regard it will be understood that it will be possible to position installations according to the invention in other locations where conventional installations would be unacceptable, for instance in building or sports complexes.  
         [0033]    From a security point of view vulnerable electronic and other equipment associated with the operation of the antenna supported by the mast is securely positioned underground within the installation  12 , obviating the need for above-ground security fencing or the like.  
         [0034]    Yet further, the three dimensional composite foundation structure  12  securely and conveniently supports the mast  14 .  
         [0035]    Yet another advantage arises from the subterranean location of the chamber  24 . Thermal inertia and the shielding effect of the soil surrounding the chamber will, it is believed, facilitate the maintenance of a suitably cool enivronment by ventilation or air conditioning of the chamber.  
         [0036]    In another, less preferred embodiment of the invention, not illustrated, the foot of the mast  14  is secured rigidly to the roof slab of the chamber. Although quite feasible, and may in fact be desirable in the case of, for instance, mast of lattice construction, this is considered less desirable than the embodiments described above because it would necessitate a foundation structure, and in particular roof slab structure, robust enough to take force moments transmitted to it by the mast. This is avoided in arrangements such as those illustrated in the drawings, where the mast is supported by, but not rigidly connected to the foundation structure, with the foundation structure providing lateral restraint at the level of the base and roof and the soil surrounding the foundation structure providing the necessary passive resistance.