Antenna positioner for portable satellite terminal

Abstract

A motorized antenna positioning mechanism in a portable microwave communication unit for use as a ground station in a satellite communication system. The antenna positioner has compact and low profile azimuth wire drive mechanics, azimuth and polarization angle sensors that are not affected by slippage and backlash, and an elevation drive mechanism which neutralizes the pressure on the motor axis due to the weight of the parabolic antenna.

1 . An azimuth drive and sensor for a satellite terminal, comprising: 
 a driving pulley;    a motor connected to said driving pulley, said motor operative to drive said driving pulley;    a rotatable platform for mounting an antenna, wherein said rotatable platform is rotatable about an axis;    a flexible wire engaged with said rotatable platform and said driving pulley such that rotation of said driving pulley causes rotation of said platform;    a rotary potentiometer having two dielectric layers, a first one of said dielectric layers having a circular conductive trace and a second one of said dielectric layers having a circular resistive trace, said circular traces being adjacent to one another and separated by a spacer layer, said circular traces being concentric about said axis and lying in a plane perpendicular to said axis, wherein said potentiometer is fixed relative to rotation of said platform;    a plunger attached to said rotatable platform, said plunger positioned such that it traces a circular path when said platform is rotated about said axis and such that said plunger contacts said rotary potentiometer at a point of contact and connects said circular traces together at said point of contact; and    a circuit connected to said potentiometer which generates an output voltage proportional to an angular position of said plunger which angular position indicates an azimuthal angle of an antenna.    
   
   
       2 . An azimuth drive according to  claim 1 , wherein said driving pulley has a groove extending about its circumference and wherein flexible cable is engaged with said groove for a 300 degree winding angle around the drive pulley.  
   
   
       3 . An azimuth drive according to  claim 1 , wherein said rotatable platform has a first guiding channel and a first termination point and a second guiding channel and a second termination point, said termination points for connecting respective ends of said flexible cable, and each of said guiding channels for engaging a portions of said flexible cable proximate a respective one of said ends.  
   
   
       4 . An azimuth drive according to  claim 3 , wherein said flexible cable is engaged with said first guiding channel for a 200 degree winding angle around said rotatable platform and wherein said flexible cable is engaged with said second guiding channel for a 200 degree winding angle around said rotatable platform.  
   
   
       5 . An azimuth drive according to  claim 1 , wherein said flexible cable is aircraft grade type cable strand 7×19.  
   
   
       6 . An azimuth drive according to  claim 3 , wherein said termination points include springs for tensioning said flexible cable.  
   
   
       7 . An azimuth drive according to  claim 1 , wherein said flexible cable is crossed between said driving pulley and said rotatable platform.  
   
   
       8 . An azimuth drive according to  claim 1 , wherein said circuit comprises an analog to digital converter that converts said second voltage from analog form to digital form.  
   
   
       9 . An azimuth drive according to  claim 8 , wherein said analog to digital converter is a 10-bit analog to digital converter.  
   
   
       10 . An azimuth drive according to  claim 1 , wherein said drive unit, said pulley, and said rotational platform form part of a baseplate, said baseplate being an approximately planar upper surface of a baseband housing, said baseband housing containing components required to process data between said satellite terminal and a computer.  
   
   
       11 . An azimuth drive according to  claim 1 , wherein said plunger is spring loaded.  
   
   
       12 . An azimuth drive according to  claim 1 , wherein said motor is a step motor.  
   
   
       13 . An azimuth drive according to  claim 1 , wherein said motor is connected to said driving pulley by a gear reduction box.  
   
   
       14 . An azimuth drive according to  claim 2 , wherein said groove is an undersized groove relative to a diameter of said flexible cable.  
   
   
       15 . An azimuth angle sensor for a satellite terminal, comprising: 
 a platform for mounting an antenna, said platform rotatable about an axis,    a rotary potentiometer having two dielectric layers, a first one of said dielectric layers having a circular conductive trace and a second one of said dielectric layers having a circular resistive trace, said circular traces being adjacent one another and separated by a spacer layer, said circular traces being concentric about said axis and lying in a plane perpendicular to said axis, wherein said potentiometer is fixed relative to rotation of said platform;    a plunger attached to said platform, said plunger positioned such that it traces a circular path when said platform is rotated about said axis and such that said plunger contacts said rotary potentiometer at a point of contact and connects said circular traces together at said point of contact;    a circuit connected to said potentiometer which generates an output voltage proportional to an angular position of said plunger, which angular position indicates an azimuthal angle of an antenna.    
   
   
       16 . The angle sensor of  claim 15 , wherein said plunger is spring loaded.  
   
   
       17 . The angle sensor of  claim 15 , wherein said potentiometer and said rotatable platform are mounted on a baseband housing of said satellite terminal.  
   
   
       18 . The angle sensor of  claim 15 , wherein said circuit includes an analog-to-digital converter that is part of said circuit, that converts said second voltage from analog to digital form.  
   
   
       19 . The angle sensor of  claim 15 , wherein said rotary potentiometer, said platform and said circuit form part of a baseplate, said baseplate being an approximately planar upper surface of a baseband housing, said baseband housing containing components required to process data between said satellite terminal and a computer.  
   
   
       20 . An elevation drive mechanism for changing an angle of elevation of an antenna of a satellite terminal, wherein when said angle of elevation is changed said antenna is pivoted about a first axis, said elevation drive mechanism comprising: 
 an elevation motor assembly having a housing, a motor and a motor axle, said motor assembly pivotable about a second axis;    a threaded elevation rod having a longitudinal axis, said elevation rod coupled to said motor axle such that rotation of said motor axle causes rotation of said elevation rod;    a bearing supported by said housing, said bearing engaged with said elevation rod such that said elevation rod may rotate about said longitudinal axis relative to said housing;    a threaded nut, said threaded nut pivotally mounted to said antenna so as to permit said threaded nut to pivot about a third axis, said nut threadably engaged with said elevation rod such that rotation of said elevation rod about said longitudinal axis causes said threaded nut to move longitudinally along said elevation rod causing a change in said angle of elevation;    wherein a force applied longitudinally along said elevation rod is transferred through said bearing to said housing; and    wherein said first axis, said second axis and said third axis are parallel to one another.    
   
   
       21 . An elevation drive mechanism according to  claim 20 , wherein said elevation rod is coupled to said motor axle by a coupler.  
   
   
       22 . An elevation drive mechanism according to  claim 20 , wherein said force is caused by one of gravity and wind.  
   
   
       23 . An elevation drive mechanism according to  claim 20 , further comprising a manual override to permit manual rotation of said elevation rod.  
   
   
       24 . An elevation drive mechanism according to  claim 20 , wherein said elevation rod is in press-fitted engagement with said bearing.  
   
   
       25 . An elevation drive mechanism according to  claim 20 , wherein said bearing is a ball bearing.  
   
   
       26 . A feed assembly and polarization angle sensor for a satellite terminal, comprising: 
 a fixed part;    a feed mounted to said fixed part;    a rotatable part connected to said fixed part, said rotatable part rotatable about an axis relative to said fixed part;    a Transmit/Receive separator and a receiver mounted to said rotatable part such that said Transmit/Receive separator and said receiver rotate about said axis with said rotatable part;    a rotary potentiometer attached to said fixed part, said potentiometer having two dielectric layers, a first one of said dielectric layers having a circular conductive trace and a second one of said dielectric layers having a circular resistive trace, said circular traces being adjacent to one another and separated by a spacer layer, and said circular traces being concentric about said axis and fixed relative to rotation of said rotatable part;    a plunger attached to said rotatable part such that said plunger traces a circular path as said rotatable part rotates about said axis, said plunger positioned such that it contacts said rotary potentiometer at a point of contact and connects said circular traces together at said point of contact;    a circuit connected to said potentiometer which generates an output voltage which corresponds to an angular position of said plunger which angular position indicates a polarization angle of an antenna;    wherein said feed is aligned so as to receive a signal along said axis, and said Transmit/Receive separator and said receiver are aligned so as to receive a signal from said feed.    
   
   
       27 . A feed assembly and polarization angle sensor according to  claim 26 , further comprising a motor, said motor operatively connected to said rotatable part such that activation of said motor causes rotation of said rotatable part about said axis.  
   
   
       28 . A feed assembly and polarization angle sensor according to  claim 26 , wherein said feed assembly and polarisation angle sensor is mounted to a boom of a satellite terminal antenna.  
   
   
       29 . A feed assembly and polarization angle sensor according to  claim 28 , further comprising a gear on said rotatable part wherein said gear rotates with said rotatable part and wherein said gear is operatively connected to said motor such that activation of said motor causes rotation of said rotatable part about said axis.  
   
   
       30 . A feed assembly and polarization angle sensor according to  claim 26 , further comprising a manual override to manually rotate said rotatable part.  
   
   
       31 . A feed assembly and polarization angle sensor according to  claim 26 , wherein said feed is a cross-polarization compensated feed.  
   
   
       32 . A feed assembly and polarization angle sensor according to  claim 26 , wherein said plunger is spring loaded.  
   
   
       33 . A feed assembly and polarization angle sensor according to  claim 26 , wherein is said circuit includes an Analog-to-Digital Converter that converts said second voltage from analog to digital form.