Abstract:
Alignment monitoring systems for directional and omni-directional antennas that are mounted to the antennas and which include solar sensors that are mounted with enclosing housings such that solar imaging across the surface of one or more sensing elements is used to determine a current alignment of the antennas in at least in one of headings, or azimuths of the antennas, or tilt angles thereof relative to a horizontal plane, and wherein signals generated by the sensing elements are communicated to data processing units.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to the field of directional alignment and alignment monitoring systems for directional and planar pattern omni-directional antennas of all types and particularly to those used in communications. Alignment of directional antennas is important in competitive industries with customers expecting uninterrupted cellular phone service and other communication and data services. 
         [0003]    2. Description of the Related Art 
         [0004]    Several types of metrological equipment are currently used to align directional antennas. These include conventional construction tools such as levels and transits plus location aides positioned at a distance from the antennas at known headings or locations, determined by such devices including compasses and surveying equipment or satellite global positioning systems (GPS), which can be used to site the antennas using lasers, transits and other optical equipment available to a ground observer. All these methods, however, require a technician, or teams of technicians, to climb to the height of the antennas, which are normally mounted a high elevations on towers or poles, to physically and actively align the antennas and measure their position directly by hand. No devices are currently known that can be remotely controlled to monitor antenna alignment after installation. 
         [0005]    Hands on alignment of antennas is a significant cost to the owners of directional and omni-directional antennas and accurate alignment information is crucial when relating to overall radio frequency (RF) system design and function. Currently, there is no all inclusive method to double check the audits of antenna alignments made by tower crews. Further, each time a storm hits an area or customers complain about poor service, a crew of technicians must climb a tower or pole to manually check the alignment of the antenna. The measurements are complex and made in a difficult environment high above the ground. If a mistake is made, there is no way to verify the alignment directly. The only method available is to make a survey or study of the area the antenna is supposed to be covering using radio test equipment and comparing measured signal strengths to expected values. This method is indirect as factors other than alignment may affect signal strength. 
         [0006]    Several articles and/papers that will provide reference and technical background relating to the present invention are: “The Impacts of Antenna Azimuth and Tilt Installation Accuracy on UMTS Network Performance” by Esmael Dinan, Ph.D. and Aleksey A. Kurochkin (January 2006), “Impact of Mechanical Antenna Downtilt on Performance of WCDMA Cellular Network” by Jamo Niemela and Jukka Lempiainen, and “Coded aperture camera imaging concept” by Jean in&#39;t Zand (1996). These articles are intended to be part of the specification to provide definitions and explanations for the technical terminology used to describe the invention. Accordingly, the three articles are hereby incorporated by reference within the specification of the present application for patent. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention is directed to directional alignment and alignment monitoring systems for directional or omni-directional antennas based on solar position alone or in combination with electronic level sensing. The invention uses sensors that mount to the antennas that are to be aligned and/or monitored and which communicate with a central data collection or processing unit. The sensors are directly mounted to antennas so as to frequently monitor their position to thereby ensure long term alignment and making it possible for the owners of the antennas to check antenna alignments and track the history of the alignments on an on going basis without having to send technicians to an antenna site to climb an antenna pole or tower to manually check the alignment. 
         [0008]    The sensors are specifically design to monitor solar positioning during periods of day light in order to accurately determine the tilt angle of an antenna, that is the angle below a horizontal plane, and heading or azimuth, the direction of the antennas energy signals. In accordance with a first embodiment of the invention, a sensor is fixedly mounted to an antenna and includes a mask housing which entirely encloses at least one solar sensing element, such as a CCD, in order to prevent light to pass there through. To monitor solar positioning, predetermined patterns of small openings are made through a side wall of the housing such that patterns of light images will be directed onto a surface of the at least one CCD. An output signal from the at least one CCD is connected to, or is otherwise communicated to, a data processing unit where the signals received are used together with known positional location of the antenna, the time of day and the day of the year, in order to calculate the alignment data for the antenna. This information may be continuously updated and forwarded to personnel monitoring the condition of the antenna. 
         [0009]    In another embodiment of the invention, the sensor mounted to the antenna includes at least one solar sensing element, such as a phototransistor, that is mounted within an enclosing housing that prevents light from entering but that includes at least one elongated open slit there through which is specifically configured to allow light to pass to at least one phototransistor where the detected light is used to generate signals that are communicated to the data processing unit. In some variations of this embodiment, a plurality of phototransistors may be spaced in predetermine relationships to receive solar energy at different times of day or at different angles or to receive solar energy passing through different slits. 
         [0010]    In yet a further embodiment of the invention, a plurality of solar sensors, such as phototransistors, are placed within an enclosing housing having at least a portion of the walls transparent to permit solar light to be used to create shadow images as the light shines on a shadow creating member or post within the housing thereby casting shadow images on one or more of the phototransistors. The detected pattern of shadow images may be used to determine solar positioning by a data processor that is in communication with the solar sensors. In a preferred variation, the phototransistors are arranged in a circular pattern with the shadow creating member positioned at the center of the circle. In the current embodiment, the housing may also include a refracting lens to direct and/or concentrate light relative to the shadow creating member and the phototransistors. Further in this embodiment as well as the previous embodiments, one or more conventional electronic level detectors or accelerometers may be mounted to or adjacent the housing to measure the current tilt level of the antenna to which the sensor device is secured such that signals with respect to the tilt angle may be sent to the data processing unit. 
         [0011]    The present invention frequently checks the alignment of an antenna automatically. No personnel must climb a tower or pole to physically take measurements to align an antenna and no personnel need be in the area of the antenna to check alignment. Alignment is checked independently of signal strength, which can eliminate a source of antenna malfunction when attempting to solve a service problem. No extra cost is incurred to make frequent measurements using the invention, as all the measurements are made automatically. The invention may also be programmed to automatically alert the antenna owners to an out of alignment condition, relieving the antenna owners of maintaining a scheduled check of alignment. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    A better understanding of the invention will be had with reference to the accompanying drawings wherein; 
           [0013]      FIG. 1  is an illustrational view of a plurality of alignment sensors of the present invention mounted on an array of three directional antennas; 
           [0014]      FIG. 2  is an illustrational view showing the antennas of  FIG. 1  mounted to a tower and showing a connection between the alignment sensors for the antennas and a central data collection and processing unit; 
           [0015]      FIG. 3  is a perspective view of a first embodiment of solar alignment sensor in accordance with the invention wherein the sensor includes a coded apertured mask with one horizontal CCD mounted within the mask housing; 
           [0016]      FIG. 4  is a view of the coded aperture mask sensor of  FIG. 3  showing three vertical CCDs mounted within the mask housing; 
           [0017]      FIG. 5  is a perspective view of a second embodiment of solar alignment sensor that includes a slit body housing with phototransistors mounted therein; 
           [0018]      FIG. 6  is a perspective view of a variation of the solar sensor of  FIG. 5 ; 
           [0019]      FIG. 7  is a perspective cross sectional view of one of the slit body sensors of  FIGS. 5 and 6  showing the internal phototransistors; 
           [0020]      FIG. 8  is a perspective view of a third embodiment of solar alignment sensor in accordance with the teachings of the present invention showing a lens housing mounted over a center post positioned centrally of a ring of phototransistors mounted therein; 
           [0021]      FIG. 9  is a perspective overhead view of the center post solar sensor with the ring of phototransistors of  FIG. 8 ; and 
           [0022]      FIG. 10  is an enlarged perspective view of the solar sensor of  FIG. 8  showing a refracting lens housing. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0023]    This invention can be configured in several ways depending on the deployment environment. The basic system as shown in  FIG. 1  consists of sensors  10  which mount to antennas  12  to be aligned plus a central data collection and processing unit  13 , see  FIG. 2 . Each sensor  10  is mounted to an aligned directional antenna  12 , with a known geometric relationship to the directional characteristic of the antenna. This can be a single or multiple segment antenna, as long as there is a common structure that can be used to define alignment of all the segments. 
         [0024]    Antennas are typically mounted on some type of adjustable bracket  14 , see  FIGS. 3 ,  4  and  8  allowing adjustment in azimuth or heading and downward tilt angle, the angle below horizontal along the antenna&#39;s center of energy heading direction. The antennas are also mounted on a tall pole  16  or tower, or on a building or billboard (not shown) overlooking a coverage area. In the embodiment shown, a plurality of antennas are shown mounted to spaced vertically extending pole segments  24  that are carried by support arms  25  that are generally equally spaced outwardly from an upper portion of the tower  16 . The number of pole segments may vary with the general idea being that the number of antennas mounted to the tower is sufficient to provide signal coverage through an area of 360° relative to the tower. 
         [0025]    Each of the brackets  14  shown includes a pair of clamp members  20  and  21  that are mounted in opposing relationship to one another on opposite sides of one of the pole segments  24  and are secured to one another by adjustable bolts  27 . The number of brackets for mounting each antenna may vary from one to any number, however, as shown, two brackets are used to mount the antennas to the pole segments. Each bracket also includes a generally u-shaped member  28  that is secured to the backplane  29  of one of the antennas and which is pivotally connected at spaced points  30  to upper portions of a frame member  31  that is pivotally connected at  33  to spaced lower portions of a second frame member  34  that is pivotally adjustable at points  35  to the clamp member  21 . Appropriate fasteners, not shown, are used at each of the pivot points to lock the two frame members in an adjusted position relative to one another in order to retain the mounted antenna in a predetermined and properly aligned position relative to the service area surrounding the tower. By adjusting the angled relationship between the frame portions of each bracket and the clamping members, an appropriate tilt angle may be obtained. 
         [0026]    The sensors  10  are also mounted to the backplanes  29  of the antennas by generally L-shaped brackets  36 . As shown in  FIG. 3 , a first sensor  10 A is shown mounted on a leg  37  of bracket  36  so as to be positioned at a known and precise relationship to the direction of radiation pattern of the antenna to which it is mounted. 
         [0027]    Collection of data can be done at each sensor or at a remote central location. The preferred method is to have one data collection unit  13  for each site having multiple antennas, with the data collection unit accessible at the base of the tower or in an easily accessible control cabinet or room (not shown). Cables  17  or wireless data transmission devices (not shown) connect the sensors to the data collection unit  13 . Data reduction and processing can also be done at each sensor  10  as opposed to a remote location of the data collection unit shown in the drawing figures. It is also possible to have the data processing unit include a portable device, such as a standard computer  15 , as shown in  FIG. 2 . In this manner, the collected data may be transferred to the computer or a disk through a direct connection to the sensors or by connection to the data collection unit  13  during a site visit. Information from the data collection unit, the sensors or the computer may also be conveyed over the internet. Software to process the data can be located either on the end users&#39; computer system or on a central internet connected server. Files containing sensor data can be then sent to the server over the internet for processing, and alignment results sent back to the end user. This method allows the software used to process the data to remain in possession of the supplier of the system so that a fee may be collected for each alignment check performed by the end user. 
         [0028]    As shown, the alignment sensors are designed to be permanently installed atop of, or otherwise secured relative to, the directional antennas. The sensors can be made using one or a combination of the several ways described herein. The first category of alignment monitoring sensor  10 A uses the sun to determine both azimuth and inclination. This is accomplished in one of two main ways. The first way, as shown in  FIG. 3  uses a charge coupled device (CCD) as a solar sensor  18  mounted behind a coded aperture or shadow mask  19 . The mask is shown in  FIGS. 3 and 4  as being partially transparent or translucent for purposes showing the interior CCD, however, the mask will be opaque except for a pattern of small holes provided therein. The mask has a set of very small holes  38  arranged so that light from the sun will project through the holes forming changing patterns of images onto the CCD during certain times of the day. As the earth rotates, the images move in a very precise direction and speed across the CCD. The CCD and coded aperture mask are precisely mounted with respect to the antenna direction, and the relative position of the sun images versus time and date give precise information of both azimuth and elevation (level) of the sensor  10 A and therefore the antenna. The shadow mask is designed to have the holes  38  spaced so that any direction that the sun shines through to make an image on the CCD can be distinguished from all others. The top of the sensor  10 A is covered by a roof or cover  40  to keep out weather. As previously noted, the bracket  37  interfaces with a part of the antenna at a known precise relationship to the direction of the radiation pattern of the antenna. 
         [0029]    The sensor coded aperture mask  19  and CCD  18  can be arranged in several ways, the preferred orientation is with the coded aperture mask  19  in a cylindrical arrangement with a vertical axis “A” and the CCD  18  centered on this axis in a horizontal plane below the shadow mask. The CCD  18  and mask  19  will be arranged to view the sun from about 10 to 60 degrees above the horizontal, and 360 degrees around in azimuth. Alternate versions of this sensor can use the same cylindrical mask with one or more CCD&#39;s  18  arranged either vertically as shown in  FIG. 4  or at an angle between horizontal and vertical looking up (not shown). This is more complex, but can give a more consistent image of the sun for the change in elevation. Also, the shadow mask  19  can be made planar with the CCD behind it either perpendicular or parallel, or at a compromise angle between facing up towards the mask. This type of mask would have to be oriented toward the rising or setting sun directions, as the field of view in azimuth is somewhat restricted compared to the 360 degree view from the cylindrical mask. In addition to the foregoing, a set of several evenly angularly spaced sensors  10 A could be varied so as to may be used to form a 360 degree view sensor as described. 
         [0030]    Another variation on the all solar permanently installed alignment monitoring sensor  10 B uses a phototransistors or group of phototransistors  42  as solar sensors mounted within a housing  43 , see  FIG. 7 , to sense the sun when it comes into alignment with a set of slits  44 , see  FIG. 5 , in the walls of the housing. The slits  44  are arranged across the possible yearly sun angles for the deployed location of the sensor  10 B during the morning and or afternoon. At least one slit for each morning or afternoon is used, or at least two either morning and/or afternoon. Each slit is angled so that the sun crosses it at nearly right angles, within about 30 degrees, each day, and the slits have a wide enough view angle to encompass the variation in sun position from winter to summer. Approximately 90 degrees field of view in the cross sun direction was found to be sufficient for this purpose. The housing  43  prevents light from reaching the phototransistors except through the slits. The housing shape can be hollow cylindrical with a vertical axis “B”, as shown, or of some other configuration. 
         [0031]    One phototransistor per slit can be used, or multiple slits can illuminate the same phototransistors, as the times each slit will be illuminated are spaced far enough to not be mistaken. Also, several phototransistors can be aligned below each slit, as is shown in  FIG. 7 , so that they will be sequentially illuminated as the sun sweeps past each day. This has the advantage of making several measurements per day. The phototransistors can be mounted to a central vertical circuit board  47  or mounted remotely, and connected to the sensor body by fiber optic cables, not shown. The cables would be mounted with their polished ends oriented and placed where the sensors are shown in  FIG. 7  to gather the light from the sun when it comes into alignment with each slit. Again, a single sensor is enough for several slits, or each slit can be equipped with a single fiber optic for conveying light to a phototransistors. Plastic molded light conductors, not shown, may also be employed to create a wider angle of light acceptance for the phototransistors either directly or through a fiber optic cable. The threshold value on the phototransistors is set high enough that only direct solar alignment through the slits will activate the sensing circuit. 
         [0032]    The housing  43  is mounted atop each antenna to be monitored to be adjustable around the vertical axis, by being secured to an L-shaped bracket, such as  36 , as previously described. For this type of sensor, a method of relating the view position of the sensor back to the azimuth direction of the antenna is required. The preferred method is to mount the sensor  10 B on the leg  37  of the bracket  36  with the surface of the leg being exactly horizontal when the antenna is correctly leveled, with a central bolt or pin, not shown, about which the sensor can rotate about the vertical axis “B”. To retain the housing in a proper position, a set of equally spaced holes, not shown, are provided on the leg  37  of the sensor mounting bracket  36  into which one or more pins, not shown, on the bottom of the sensor can selectively engage. This forces the sensor to be in one of a number of accepted clocking positions with respect to the antenna. A magnet carried by the mounting bracket  36  may be sensed by one of a circular array of hall effect switches, or reed switches, not shown, arranged around the base of the sensor. Alternately, a fixed pin, not shown, on the mounting bracket  36  can be configured to penetrate one of an array of equally spaced holes, not shown, in the sensor housing  43  base where is it sensed by one of a circular array of optical switches or inductive proximity switches, not shown. 
         [0033]    These arrayed sensors relate the azimuth position of the sensor to the position of the antenna. In some instances an engraved degree wheel, not shown, on the bracket  36  can be used as an indicator by a pointer fixed to the sensor housing  43  and the position noted and inputted to the central data collection and processing unit  13 . The sensor body is aligned in azimuth to point the slits  44  toward the intended solar track or transverse. For example, a sensor using both morning and afternoon slits would have the slits aligned so that a plane midway between the slits views or faces exactly south. Morning alone slits  44  must be pointed roughly south east, and afternoon alone slits  44 ′ pointed roughly southwest, depending on latitude. These view directions are to allow installation where the structure of the antenna tower  16  or other support may block some views of the sun. The sensor  10 B will not work in a location that is shaded from a direct view of the sun. Measuring of the time of the solar transverse of each slit relative to the known direction of the slits and date, time and location gives precise pointing information of the sensor, in tilt (2 axes) and heading. This is done by comparison of the actual solar transverse time to the expected time from a solar transverse equation and converting the vector to the correct position in the central data collection and processing unit  13 . 
         [0034]    A third embodiment of a permanently installed solar alignment monitoring sensor  10 C is shown in  FIGS. 8-10  that uses a combination solar sensor for determining azimuth (heading) and electronic level sensors  52  for determining elevation. The sensor  10 C is mounted on the horizontal leg  37  of the L-shaped bracket  36  so as to be fixed with respect to the antenna  12 . This sensor uses a ring  54  of solar sensors such as phototransistors  42  mounted to the top surface of a horizontally mounted circuit board  55  with a round shadow post  56  mounted vertically in the center of the ring of sensors. 
         [0035]    The sun will cast a shadow of the post  56  across the ring of sensors or phototransistors, allowing them to sense the sun azimuth position. This can be done using wide acceptance angle sensors directly, or by placing a cover  60  over the ring of sensors  54  with the cover including a refracting lens  62  positioned above the sensors which accepts sunlight at lower sun angles and refracts the lower incidence sun rays downward into the sensors at a proper acceptance angle. Also, the upward angle can be increased by the same method. 
         [0036]    An example of a combination sealed cover and refracting lens  60  is shown in  FIGS. 8-10 . This combination cover may be made of clear plastic that forms the lens  62  with a lower part  65  of the sealed cover being opaque (not shown) to reduce unwanted sun illumination of the sensors  42 . In some of the drawing figures, the cover  60  is shown is dotted line so that the ring of sensors is clearly visible. Further, the lower part  65  is not shown opaque in order to permit visualization of the ring of phototransistors. The number of phototransistors  42 , and angular spacing versus the thickness of the shadow post  56  can be selected to create an alternating one sensor shaded, then two. This makes the sun azimuth angle able to be instantly determined using half of the sensor spacing angle. For example, if thirty-six sensors are used with a post that occludes 15 degrees of the arc at the sensor placement radius, the sensor will be able to give an azimuth reading accurate to 5 degrees as soon as the sun is visible to the sensors. Upon the shadow edge crossing one of the phototransistors, the angular precision increases to the practical limit given by the accuracy of sensor threshold setting plus time keeping and geographic location of the sensor  10 C. 
         [0037]    Level sensing in the current embodiment may be handled instantly by either a pair of electronic level sensors using a pendulum (not shown) or by a pair of solid state accelerometers  52 . In either case, the instruments are placed orthogonally with one axis aligned with down tilt angle of the antenna. It should be noted that the electronic lever sensors  52  may be of any convention structure such that level readings may be transmitted directly or indirectly to the data collection and processing unit  13 . 
         [0038]    The sensor  10 C has two distinct advantages to the sensor  10 B discussed above. First, it can be installed in any azimuth orientation, making alignment to the antenna much simpler, as it will be fixed to the antenna in one orientation regardless of the antenna&#39;s installed direction (N, S, E or W). Second, the level information is available to the installed real time, and may be used to assist with antenna alignment during installation regardless of weather conditions. Level information from all the sensors gives information in two axes, down tilt, along the antenna&#39;s preferential radiation direction, and roll, perpendicular to the antenna&#39;s preferential radiation direction. Down tilt is the most important parameter to an antenna&#39;s performance, but roll information is also important, because the antenna&#39;s mapped radiation pattern assumes that the antenna is mounted level in roll. 
         [0039]    It should be noted that the sensors  10 A and  10 B describe herein could also be fitted with electronic level sensors to gain the advantages stated above. It should also be noted that other solar sensing devices may be used with or in place of the CCD devices and phototransistors mentioned in the described embodiments. 
         [0040]    The foregoing description of the present invention has been presented to illustrate the principles of the invention and not to limit the invention to the particular embodiments illustrated. It is intended that the scope of the invention be defined by all of the embodiments encompassed within the following claims and their equivalents.