Patent Publication Number: US-6987487-B2

Title: Antenna system

Description:
This is a continuation of application Ser. No. 09/788,790, filed Feb. 19, 2001, entitled Antenna System, and currently pending. Now U.S. Pat. No. 6,573,875. 
    
    
     BACKGROUND OF THE INVENTION 
     In many passive antenna assemblies, it is often desired to be able to adjust a radiation pattern of the antenna assembly after the antenna assembly has been installed on a tower. The need may arise due to a number of factors, including new construction, which may create obstacles, vegetation growth, or other changes in the surrounding environment. It may also be desired to alter the radiation pattern due to performance studies or to alter the shape of the area the antenna covers. 
     There are various ways that the radiation pattern may be altered. One method is to physically change the location of the antenna assembly. Once the assembly has been installed on a tower, however, this becomes difficult. It is also possible to change the azimuth and elevation of the individual antennas, but such a method is expensive when applied to several antennas. Also, the mechanical device required to adjust the azimuth and elevation may interfere with the mechanical antenna mount. 
     Another method that has been utilized to adjust the radiation pattern of a number of antennas grouped onto one antenna assembly is to alter the phase angle of the individual antennas. By altering the phase angle of the individual antennas, a main beam (which causes the radiation pattern) is tilted relative to the surface of the earth. The antennas are grouped into a first group, a second group, and a third group. All three groups are disposed along a panel of the antenna assembly. A phase adjuster is disposed between two of the antenna groups, such that an adjustment of the phase adjuster changes the radiation pattern. The phase adjuster comprises a conductor coupled with a transmission line to create a capacitor. The conductor is rotatable and moves along the transmission line, changing the location of the capacitor on the transmission line. The transmission line is coupled to an antenna which has a phase angle. The phase angle is dependant partially on the location of the capacitor. Thus, by changing the location of the capacitor, the phase angle is changed. The phase adjuster may be coupled to a plurality of antennas and acts to adjust the phase angle of all of them. 
     The phase adjusters currently in use, however, have numerous drawbacks. First, the conductor is often made of brass which is expensive to etch and cut. Therefore, the conductor is usually cut in a rectangular shape. The path of the transmission line, however, is arcuate. The conductor does not cover the entire width at the capacitor, which decreases the effectiveness of the capacitance. 
     Another problem with current phase adjusters is the coupling of a power divider to the phase adjuster. The antenna assembly receives power from one source. Each of the three groups of antennas, however, has different power requirements. Thus, power dividers must be connected to the assembly. Currently, a power divider may be a series of cables having different impedances. Using a variety of cables makes manufacturing difficult since the cables have to be soldered together. Also, since manual work is required, the chances of an error occurring is increased. Another method of dividing the power is to create a power divider on a PC board and then cable the power divider to the phase adjuster. Although this decreases some costs, it still requires the extensive use of cabling, which is a disadvantage. 
     A third problem is caused by the use of cable lines having different lengths to connect an antenna to the appropriate output from the phase adjuster. Each antenna has a different default phase angle when the phase adjuster is set to zero. The default phase angle is a function of the cable length coupled with the length of the transmission line. To achieve the differing default phase angles, cables of varying lengths are attached to different antennas. Although this only creates a slight increase in manufacturing costs since cables of varying lengths must be purchased, it greatly increases the likelihood of error during installation. In numerous antenna assemblies, the cable lengths only differ by an inch or less. During assembly, if a cable is not properly marked, it may be difficult for the person doing the assembly to tell the difference between the different sizes of cable. 
     To move the phase adjuster, an actuator is located on a side of the panel and may include a small knob or rotatable disc for manually changing the phase adjuster. Thus, whenever the radiation pattern needs to be adjusted, a person must climb the tower and up the side of the panel to the phase adjuster. This is a difficult and time consuming process. Also, it is only possible to move the actuator manually, requiring the exertion of physical labor. In addition, it is a dangerous activity since the antennas are located on a tower and it is possible for a person to fall or otherwise become injured in the climbing process. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings. 
         FIG. 1  is a schematic of an antenna assembly of the present invention. 
         FIG. 2  is a schematic view of a phase adjuster assembly according to one embodiment of the present invention. 
         FIG. 3  is perspective side view of a panel and the phase adjuster assembly according to one embodiment of the present invention. 
         FIG. 4  is an enlarged view of section B shown in FIG.  3 . 
         FIG. 5  is an enlarged view of section A shown in FIG.  3 . 
         FIG. 6   a  is a front view of a bushing mount according to one embodiment of the present invention. 
         FIG. 6   b  is an end view of a bushing mount according to one embodiment of the present invention. 
         FIG. 6   c  is a side view of a bushing mount according to one embodiment of the present invention. 
         FIG. 7  is an exploded perspective view of an actuator rod according to one embodiment of the present invention. 
         FIG. 8  is a perspective view of a compression nut according to one embodiment of the present invention. 
         FIG. 8A  is a perspective view of an actuator rod and an electrical actuator having a ground-based controller according to one embodiment of the present invention. 
         FIG. 9  is a perspective view of an actuator rod and an electrical actuator according to one embodiment of the present invention. 
       While the invention is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
     
    
    
     DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
       FIG. 1  is a side view of an antenna assembly  100  of the present invention. The antenna assembly  100  is comprised of a plurality of antennas  110 ,  120 ,  130 ,  140 ,  150  disposed along a panel  160 . The antennas  110 ,  120 ,  130 ,  140 ,  150  are grouped into a first group  170 , a second group  180 , and a third group  190 . The first antenna  110  and the fifth antenna  150  are in the first group  170 . The second antenna  120  and the fourth antenna  140  are in the second group  180  and the third antenna  130  is in the third group  190 . 
     To adjust the radiation pattern, the vertical electromagnetic beam of the antenna assembly  100  must be adjusted. This is accomplished by adjusting the phase angle of the first group  170  relative to the second group  180 . The first group  170 , however, must be adjusted by an amount different than the amount of the second group  180 . To accomplish this, a first phase adjuster  200  is attached to the first group  170 , and a second phase adjuster  210  is attached to the second group  180 . The adjustment amount of the second group  180  is often a function of the amount of adjustment of the first group  170 . To ensure that the first and second groups  170 ,  180  are adjusted in the correct ratio, the second adjuster  210  may be connected to the first adjuster  200 , such that an adjustment of the first adjuster causes an adjustment of the second adjuster. More particularly, the second phase adjuster  210  may be connected to the first phase adjuster  200 , such that an adjustment of the first phase adjuster  200  for a predetermined distance causes the second phase adjuster  210  to move proportional to the distance. 
       FIG. 2  depicts a schematic view of a first and second phase adjusters  200 ,  210  respectively, adapted to adjust the vertical beam or vertical beam downtilt angle. The first phase adjuster  200  is coupled to the first antenna group  170 , and the second phase adjuster  210  is coupled to the second antenna group  180 . Each of the plurality of antennas  110 ,  120 ,  130 ,  140 ,  150  has a different phase angle. By adjusting the phase angles of the plurality of antennas  110 ,  120 ,  130 ,  140 ,  150 , or at least of the first and second groups  170 ,  180  of antennas, the vertical beam of the antenna assembly  100  is adjusted. 
     The first and second phase adjusters  200 ,  210  operate in the same fashion. For simplicity, the description will be described in more detail regarding the first phase adjuster  200 . To adjust the phase angle, a conductive wiper  220  slides over a first arcuate portion  230  of a first transmission line  240 . One end of the first transmission line  240  is coupled to the first antenna  110 , while the other end of the first transmission line  240  is coupled to the fifth antenna  150 . The conductive wiper  220  in connection with the first arcuate portion  230  acts as a capacitor. To the antennas  110 ,  150 , the capacitor is seen as a short circuit at high frequencies. The length of the first transmission line  240  up to the point of the short circuit affects the phase angle of the antenna. As the conductive wiper  220  slides over the first arcuate portion  230 , the location of the short circuit changes, changing the length of the first transmission line  240  and, thus, the phase angle of the two antennas  110 ,  150 . Since the antennas  110 ,  150  are located at opposite ends of the first transmission line  240 , the movement of the short circuit lengthens one transmission line as seen by one antenna while shortening the transmission line as seen by the other antenna. In other words, the transmission line has a finite length. The finite length of the transmission line is divided into a first effective length and a second effective length. The first effective length is from the first antenna  110  to the location of the wiper  220  on the transmission line  240 . The second effective length is measured from the fifth antenna  150  to the location of the wiper  220  on the transmission line  240 . As the wiper  220  is adjusted towards the fifth antenna  150 , the first effective length is lengthened while the second effective length is shortened. As the wiper  220  is adjusted towards the first antenna  110 , the first effective length is shortened while the second effective length is lengthened. 
     In this particular embodiment, the conductive wiper  220  is a first rotatable PC board  250  with a metallic side. The first transmission line  240  is mounted on a separate fixed PC board  260 . The fixed PC board  260  and first rotatable PC board  250  act as a dielectric between the capacitor. In prior art systems, an air dielectric was sometimes used. If the conductive wiper changes its spacing relative to the first arcuate portion  230 , however, the capacitor&#39;s capacitance is altered, thus, changing the impedance match of the phase shifter. If the two sections touch, the capacitance is destroyed, which adversely affects the performance of the antenna even more. Other systems use a sheet dielectric to separate the conductive wiper from the transmission line which have to be mounted using standoffs and point fasteners. The sheet, however, tends to attenuate the capacitive effect. By using the PC boards as the dielectric, the conductive wiper cannot touch the transmission line nor are the capacitive effects attenuated. Also, the manufacturing costs for making the PC board are much lower than having to mount the sheet dielectric. 
     The first rotatable PC board  250  is pivotally connected to the fixed PC board  260  at a joint  270 , which acts as the pivot point for the first rotatable PC board  250 . At another end, a joint  280 , the first rotatable PC board  250  is slidably mounted in a first slot  255 . A mechanical actuator (to be described) including an actuator rod  500  and a main arm  500   a  moves the first rotatable PC board  250  in an arcuate path over the first arcuate portion  230 , thus changing the phase angle of the antennas  110 ,  150  as discussed above. 
     To increase the capacitive effects, an end  290  of the first rotatable PC board  250  that glides over the first arcuate portion  230  may be curved. The radius of curvature of the end  290  of the first rotatable PC board  250  is the same as the radius of curvature of the first arcuate portion  230 . Also, both the first rotatable PC board  250  and the first arcuate portion  230  have the same center point located at the joint  270 . By completely aligning with the arcuate portion  230 , the capacitance is increased, increasing the effectiveness of the first phase adjuster  200 . 
     The first transmission line  240  is electrically connected to an input  300  for receiving power. The first rotatable PC board  250  is also electrically connected to the input  300 . The first transmission line  240  is coupled to the first antenna  110  (shown in  FIG. 1 ) at a first output  310 , and also to the fifth antenna  150  (shown in  FIG. 1 ) at a fifth output  320 . Each of the antennas  110 ,  150  has a default phase angle when the capacitor is set to zero, which is marked on FIG.  2 . The default phase angle of antenna  110  is a function of the length of the first transmission line  240  and a cable line (not shown) connecting the first transmission line  240  to the antenna  110 . The first transmission line  240  includes a first path  330  leading from the first arcuate portion  230  to the first output  310 . The length of the first path  330  is determined by the default phase angle of the first antenna  110 . The first transmission line  240  also has a second path  340  connecting the first arcuate portion  230  to the fifth output  320 . The length of the second path  340  is determined by the default angle of the fifth antenna  150 . By varying the length of the first path  330  and the fifth path  340 , the same length cables can be used during installation to connect the antennas to the output, which makes installation easier. 
     The second phase adjuster  210  acts in the same way as the first phase adjuster  200 . A second rotatable PC board  350  is mounted on the fixed PC board  260  and is electrically coupled to the input  300 . The second rotatable PC board  350  is rotatable around a joint  355 , which is also where the second rotatable PC board  350  is connected to the fixed PC board  260 . A second transmission line  360  having a second arcuate portion  370 , a first path  380 , and a second path  390  is also electrically connected to the input  300 . The second rotatable PC board  350  glides over the second arcuate portion  370  to create the capacitor. The second rotatable PC board  350  is moved by mechanical actuator comprising actuator rod  500  and main arm  500   a.  Main arm  500   a  is connected through a linkage to be described to the board  350  at a joint  395  located in a second slot  405  in the fixed PC board  260 . The first path  380  of the second transmission line  360  is connected to a second output  400 , which is coupled to the second antenna  120  (FIG.  1 ), while the second path  390  of the second transmission line  360  is connected to a fourth output  410 , which is coupled to the fourth antenna  140 . As with the first phase adjuster  200 , the lengths of the first and second paths  380 ,  390  are adjusted to create the proper default phase angle. 
     Also connected to the input  300  is a third transmission line  420 , which is coupled to a third output  430 , which is connected to the third antenna  130 . The third transmission line  420  is of a length to create the proper default phase angle. Since all of the individual paths  330 ,  340 ,  380 ,  390 ,  420  of the various transmission lines  240 ,  360 ,  420  are adjusted to create the proper default phase angle, the same length cable can be used to connect the antennas  110 ,  120 ,  130 ,  140 ,  150  to their respective outputs  310 ,  400 ,  430 ,  410 ,  320 . This not only makes manufacturing easier, it also eliminates the possibility of error during installation of connecting the wrong length cable to the output. 
     The input  300  is connected to a conductive strip  440  which acts as a power divider and bleeds off power to the first and second phase adjusters  200 ,  210  and the third transmission line  420 . The conductive strip  440  has an established impedance. The impedance of the strip  440  is a function of the width of the strip  440 . By changing the width of the conductive strip  440 , the impedance and, thus, the power is changed. In the present invention, the conductive strip  440  branches into a first strip  450 , a second strip  460 , and a third strip  470 . The first strip  450  transfers power from the conductive strip  440  to the first phase adjuster  200 . The second strip  460  transfers power from the conductive strip  440  to the second phase adjuster  210 , and the third strip  470  transfers power from the conductive strip  440  to the third transmission line  420 . The width of each of the first, second, and third strips  450 ,  460 ,  470  is manufactured to draw the correct amount of power from the conductive strip (or power divider)  440 . By using a power divider on the fixed PC board  260 , excess cables are eliminated, which decreases cost and also increases the reliability of the antenna assembly  100 . In another embodiment of the present invention, a conductive strip can be included to divide power on the first and second transmission lines  240 ,  360  along the arcuate portions  230 ,  370 . 
     It is sometimes desirable to lock the first and second phase adjusters in a permanent position. In current systems, a phase adjuster was locked into position at the time of manufacture since the phase adjuster does not include markings or the like. In one embodiment of the present invention, however, the fixed PC board  260  includes a first set of markers  480   a  over the first slot  255  and a second set of markers  480   b  over the second slot  405 . The sets of markers  485   a,    485   b  provide a user with a method for viewing the phase angle settings of the first and second phase adjusters  200 ,  210 . A locking mechanism  485  is included to lock the first and second phase adjusters  250 ,  350  in a set position. In one embodiment, a series of through holes  490   a,    490   b  may also be included on the fixed PC board  260  and align with through holes  495   a,    495   b  on the first and second rotatable PC boards  250 ,  350 . A screw (not shown) may be used to lock the first or second first rotatable PC board  250 ,  350  to the fixed PC board  260 . The use of markings and a lock system is a great improvement because the fixed PC board  260  can be assembled to the first and second phase adjusters  200 ,  210  without knowing if the phase angles need to be locked. Thus, this device may be manufactured prior to a purchase order being received. Once a purchase order is made, the markings and lock system can be used to lock the first and second phase adjusters  200 ,  210  in place, if so desired. 
     Turning now to  FIGS. 2-4 ,  FIG. 2  depicts a front side of the fixed PC board  260 .  FIG. 3  depicts a perspective view of a side of the panel  160  of the antenna assembly  100  and a back side of the fixed PC board  260 .  FIG. 4  is an enlarged detail of FIG.  3 . In  FIGS. 3 and 4 , two similar PC boards  260 ,  261  are shown, each having a pair of first and second phase adjusters  200 ,  210 . Both pairs operate in the same fashion, and are only illustrated to demonstrate that a plurality of PC boards  260 ,  261  may be mounted on a single panel, both being coupled to the same mechanical actuator (rod  500  and main arm  500   a ). As discussed above, the first phase adjuster  200  comprises the fixed PC board  260  with the first arcuate slot  255  cut through and the first rotatable PC board or wiper  250  ( FIG. 2 ) on the other side of the fixed PC board  260 . The second phase adjuster  210  comprises the fixed PC board  260 , the second rotatable PC board or wiper  350  (FIG.  2 ), and the second arcuate slot  485 . To cause the first and second rotatable PC boards  250 ,  350  to rotate, the main arm  500   a  is coupled to the rotatable PC boards  250 ,  350 . 
     In one embodiment, the mechanical actuator comprises an actuator rod  500 , main arm  500   a  and a linkage comprising a first arm  510 , and a second arm  520 . The main arm  500   a  is connected to one end of the first arm  510  at a pivot point  511 . The other end of the first arm  510  is connected to the fixed PC board  260  and the first rotatable PC board  250  at the joint  270 . A cross-section of this joint  270  would show there are three layers all connected, the first rotatable PC board  250 , the fixed PC board  260 , and the first arm  510 . Since the fixed PC board  260  is stationary, the first arm  510  and the first rotatable PC board  250  also remain fixed at the joint  270 . The joint  280  connects the first rotatable PC board  250  to the first arm  510  through the first slot  255  on the fixed PC board  260 . 
     The second arm  520  is connected to the second rotatable PC board  350  through the second slot  405  at the joint  395 . Thus, a movement of the second arm  520  causes the second rotatable PC board  350  to move along the second slot  405 . The second arm  520  is also rotatably connected at a joint  522  to approximately midway between joint  270  and joint  280  on the first arm  510 . Thus, as the first arm  510  is moved, the second arm  520  also moves. Since the second arm  520  is linked to the first arm  510  at the midpoint, as the joint  512  of the first arm  510  moves a predetermined distance, the joint  395  of the second arm  520  moves approximately half the predetermined distance. In other embodiments, the second arm  520  may be attached at different locations over the first arm  510 , depending upon the desired ratio of movement between the first and second phase adjusters  200 ,  210 . 
       FIG. 5  illustrates a grasping end  505  of the actuator rod  500  that extends out past a bottom  530  of the panel  160 . The grasping end  505  of the actuator rod  500  is mounted on the bottom  530  of the panel  160 . By extending the actuator rod  500  out through the bottom  530  of the panel  160 , a person manually adjusting the mechanism only has to pull or push on the actuator rod  500 , instead of having to rotate a small knob or disc located on the side of the panel  160 , as done in the prior art. Also included on the grasping end  505  of the actuator rod  500  are markings  535  to indicate the amount of adjustment made by a person adjusting the mechanism, and a knob  536  is shown covering a threaded end  538  of the actuator rod  500 . The markings  535  have a direct relationship to the vertical downtilt angle of the beam. For example, a zero marking on the rod correlates to a zero degree downtilt angle. Since the markings  535  are not detented, a user may adjust the downtilt angle as much or as little as needed. The downtilt angle need not be moved in degree or half degree increments. The knob  536  screws onto the threaded end  538  and enables the user to easily grasp the actuator rod  500  for movement purposes. 
     The actuator rod  500  is mounted onto the bottom  530  of the panel  160  by a bushing mount  540 . The bushing mount  540  is best illustrated in  FIGS. 6   a-   6   c.  The bushing mount  540  comprises a pair of brackets  550   a,    550   b  which are attached to the panel  160 . In the embodiment shown, the brackets  550   a,    550   b  are attached via a pair of screws  560   a,    560   b  (shown in FIG.  5 ). It is also contemplated, however, that other methods, such as rivets, adhesive heat staking, welding, and brazing, may be utilized. 
     The bushing mount  540  also has a cylindrical portion  560  adapted to receive the actuator rod  500 . The cylindrical portion  560  of the bushing mount  540  allows the actuator rod  500  to be slid up and down, enabling movement. To prevent the actuator rod  500  from rotating within the cylindrical portion  560 , however, a flat section  570  ( FIG. 6   b ) is included on the inner wall of the cylindrical portion  560 . One end of the cylindrical portion  560  includes a threaded portion  565  which will be described in more detail below. 
     As mentioned above, the grasping end  505  of the actuator rod  500  includes markings  535 . The bushing mount  540  includes an indicator window  590  on opposite sides of the cylindrical portion  560  to enable a user to see the markings  535  (seen in  FIG. 6   c ). Also, in one embodiment, the bushing mount  540  may be clear plastic so that all of the markings  535  are visible to the user. 
     As shown in  FIGS. 7 and 8 , a compression nut  595  is also slid over the actuator rod  500 . The compression nut  595  includes three parts, a threaded nut  600 , a plastic gripper  610 , and a ferrule  620 . The threaded nut  600  of the compression nut  595  screws over the threaded portion  565  of the bushing mount  540  and acts to lock the actuator rod  500  in place. When the threaded nut  600  is being screwed over the threaded portion  565  of the bushing mount  540 , the plastic gripper  610  and the ferrule  620  are sandwiched against the bushing mount  540 . The ferrule acts as a seal against the bushing mount  540 . The plastic gripper  610  contains a slit  625 , which decreases in width as the threaded nut  600  is tightened against the bushing mount  540 . This causes the compression nut  595  to grip the bushing mount  540 , and lock the actuator rod  500  in place. 
     Although it is useful to have a manual actuator, it may be more desirable to have an electrical actuator that may be controlled from the ground or even remotely, for example, from a control room  630  (FIG.  8 A). In  FIG. 9 , converting the manual actuator described above into an electrical actuator  660  is illustrated. The electrical actuator  660  comprises a piston (not shown) and a threaded barrel  670 . To convert the manual actuator, the compression nut  595  and the knob  536  must first be removed. Then, a lock nut  650  is threaded onto the bushing mount  540 . The threaded end  538  of the actuator rod  500  is threaded into the piston. The barrel  670  of the electrical actuator  660  is then pushed up towards the threaded portion  565  of the bushing mount  540  and threaded. Once both the piston and the threaded barrel are completely threaded onto the actuator rod  500 , the lock nut  650  is tightened, locking the bushing mount  540  to the threaded barrel  670 . 
     The electrical actuator  660  may be a step motor in a fixed position relative to the panel  160 . The step motor rotates, driving a screw or shaft in a linear motion. The screw or shaft is coupled to the actuator rod  500  and, thus, moves the actuator rod  500  up and down, depending on the rotation of the step motor. It is also contemplated that the electrical actuator  660  may include a receiver  700  adapted to receive adjustment signals from a remote source  702 . A sensor  704  adapted to sense the position of the actuator rod  500  may also be included. A transponder  706  may also be included to return a signal to the remote location or to a signal box which indicates the amount of adjustment made. 
     The present invention may, thus, be easily converted from a manual actuator to an electrical actuator depending on the needs and wishes of the user. The actuator, thus provides flexibility in use, allowing a user to purchase a manual actuator and then upgrade to an electrical actuator at a later date. The advantages to this are many. The user may not initially wish to expend the money to pay for an electrical actuator if there is rarely a need to adjust the vertical beam. As that need changes, however, the user may purchase the electrical actuator and easily convert the actuator. 
     While the present invention has been described with reference to one or more particular embodiments, those skilled in the art will recognize that many changes may be made thereto without departing from the spirit and scope of the present invention. Each of these embodiments and obvious variations thereof is contemplated as falling within the spirit and scope of the claimed invention, which is set forth in the following claims.