Accelerated satellite acquisition scheme

Abstract

A user terminal includes a reconfigurable phased array antenna having a plurality of antenna elements. The user terminal is operable for: broadening a field of regard of the reconfigurable phased array antenna; receiving signals from a plurality of satellites within the field of regard using the reconfigurable phased array antenna; determining one or more attributes of the received signals for each of the satellites; and selecting one of the plurality of satellites for communication based on the attributes of the received signals. After the satellite has been selected, the user terminal is configured for: switching to a directional mode for the reconfigurable phased array antenna; establishing the communication with the selected satellite using the reconfigurable phased array antenna; and tracking the selected satellite. Ephemeris data broadcast by the satellites is used by the user terminal to track the satellites and to perform handovers between satellites.

What is claimed is: 
     
         1 . A method of establishing communication with a satellite, comprising:
 providing a user terminal ( 104 ) including a reconfigurable phased array antenna ( 214 ) having a plurality of antenna elements ( 300 ), wherein the user terminal ( 104 ) is operable for:   broadening ( 604 ) a field of regard of the reconfigurable phased array antenna ( 214 );   receiving ( 606 ) signals from a plurality of satellites ( 102 ) within the field of regard using the reconfigurable phased array antenna ( 214 );   determining ( 608 ) one or more attributes of the received signals for each of the satellites ( 102 ); and   selecting ( 608 ) one of the plurality of satellites ( 102 ) for communication based on the attributes of the received signals.   
     
     
         2 . The method of  claim 1 , wherein the attributes comprise signal strength, signal quality, or proximity to other signals. 
     
     
         3 . The method of  claim 1 , wherein broadening ( 604 ) the field of regard includes at least one of:
 using ( 604 ) a lesser number than a total number of the plurality of antenna elements ( 300 ) of the reconfigurable phased array antenna ( 214 ); and   using ( 604 ) a spoiled beam by changing at least one of a phase and amplitude for one or more of the plurality of antenna elements ( 300 ) of the reconfigurable phased array antenna ( 214 ) to spread a beam width.   
     
     
         4 . The method of  claim 3 , wherein using ( 604 ) a lesser number than a total number of the plurality of antenna elements ( 300 ) further comprises one of:
 selecting ( 604 ) one antenna element ( 300 ) from the plurality of antenna elements ( 300 ) of the reconfigurable phased array antenna ( 214 ); and   selecting ( 604 ) a sub-array of two or more antenna elements ( 300 ) from the plurality of antenna elements ( 300 ) of the reconfigurable phased array antenna ( 214 ).   
     
     
         5 . The method of  claim 3 , wherein the spoiled beam is generated by introducing a phase difference that alters a coherence of the received signals at the reconfigurable phased array antenna ( 214 ). 
     
     
         6 . The method of  claim 1 , wherein, after the satellite ( 102 ) has been selected, the user terminal ( 104 ) is operable for:
 switching ( 612 ) to a directional mode for the reconfigurable phased array antenna ( 214 );   establishing ( 612 ) the communication with the selected satellite ( 102 ) using the reconfigurable phased array antenna ( 214 ); and   tracking ( 614 ) the selected satellite ( 102 ).   
     
     
         7 . The method of  claim 6 , wherein tracking ( 614 ) the selected satellite ( 102 ) comprises determining ( 614 ) an initial pointing vector comprised of an azimuth and elevation and an initial tracking vector comprised of a flight path for the reconfigurable phased array antenna ( 214 ) based on ephemeris data for the satellites ( 102 ) relative to a current terrestrial or airborne location of the user terminal ( 104 ). 
     
     
         8 . The method of  claim 1 , wherein the reconfigurable phased array antenna ( 214 ) is stationary prior to selecting the field of regard. 
     
     
         9 . The method of  claim 1 , wherein the reconfigurable phased array antenna ( 214 ) is slewed to establish an initial pointing vector comprised of an azimuth and elevation prior to selecting the field of regard, but the reconfigurable phased array antenna ( 214 ) is not slewed once the field of regard is selected. 
     
     
         10 . An apparatus for establishing communication with a satellite ( 102 ), comprising:
 a user terminal ( 104 ) including a reconfigurable phased array antenna ( 214 ) having a plurality of antenna elements ( 300 ), wherein the user terminal ( 104 ) is operable for:   broadening ( 604 ) a field of regard of the reconfigurable phased array antenna ( 214 );   receiving ( 606 ) signals from a plurality of satellites ( 102 ) within the field of regard using the reconfigurable phased array antenna ( 214 );   determining ( 608 ) one or more attributes of the received signals for each of the satellites ( 102 ); and   selecting ( 608 ) one of the plurality of satellites ( 102 ) for communication based on the determined attributes of the received signals.   
     
     
         11 . The apparatus of  claim 10 , wherein the attributes comprise signal strength, signal quality, or proximity to other signals. 
     
     
         12 . The apparatus of  claim 10 , wherein broadening ( 604 ) the field of regard includes at least one of:
 using ( 604 ) a lesser number than a total number of the plurality of antenna elements ( 300 ) of the reconfigurable phased array antenna ( 214 ); and   using ( 604 ) a spoiled beam by changing at least one of a phase and amplitude for one or more of the plurality of antenna elements ( 300 ) of the reconfigurable phased array antenna ( 214 ) to spread a beam width.   
     
     
         13 . The apparatus of  claim 12 , wherein using ( 604 ) a lesser number than a total number of the plurality of antenna elements ( 300 ) further comprises one of:
 selecting ( 604 ) one antenna element ( 300 ) from the plurality of antenna elements ( 300 ) of the reconfigurable phased array antenna ( 214 ); and   selecting ( 604 ) a sub-array of two or more antenna elements ( 300 ) from the plurality of antenna elements ( 300 ) of the reconfigurable phased array antenna ( 214 ).   
     
     
         14 . The apparatus of  claim 12 , wherein the spoiled beam is generated by introducing a phase difference that alters a coherence of the received signals at the reconfigurable phased array antenna ( 214 ). 
     
     
         15 . The apparatus of  claim 10 , wherein, after the satellite ( 102 ) has been selected, the user terminal ( 104 ) is operable for:
 switching ( 612 ) to a directional mode for the reconfigurable phased array antenna ( 214 );   establishing ( 612 ) the communication with the selected satellite ( 102 ) using the reconfigurable phased array antenna ( 214 ); and   tracking ( 612 ) the selected satellite ( 102 ).   
     
     
         16 . The apparatus of  claim 15 , wherein tracking the selected satellite ( 102 ) comprises determining an initial pointing vector comprised of an azimuth and elevation and an initial tracking vector comprised of a flight path for the reconfigurable phased array antenna ( 214 ) based on ephemeris data for the satellites ( 102 ) relative to a current terrestrial or airborne location of the user terminal ( 104 ). 
     
     
         17 . The apparatus of  claim 10 , wherein the reconfigurable phased array antenna ( 214 ) is stationary prior to selecting the field of regard. 
     
     
         18 . The apparatus of  claim 10 , wherein the reconfigurable phased array antenna ( 214 ) is slewed to establish an initial pointing vector comprised of an azimuth and elevation prior to selecting the field of regard, but the reconfigurable phased array antenna ( 214 ) is not slewed once the field of regard is selected. 
     
     
         19 . An apparatus for establishing communication with a signal source ( 102 ), comprising:
 a reconfigurable phased array antenna ( 214 ) having a plurality of antenna elements ( 300 ), wherein:   a field of regard of the reconfigurable phased array antenna ( 214 ) is broadened ( 604 ) prior to receiving ( 606 ) signals from the signal source ( 102 );   the reconfigurable phased array antenna ( 214 ) is switched ( 612 ) to a directional mode when establishing ( 612 ) communications with the signal source ( 102 ) and tracking ( 612 ) the signal source ( 102 ).   
     
     
         20 . The apparatus of  claim 19 , wherein the field of regard is broadened ( 604 ) by at least one of:
 using ( 604 ) a lesser number than a total number of the plurality of antenna elements ( 300 ) of the reconfigurable phased array antenna ( 214 ); and   using ( 604 ) a spoiled beam by changing at least one of a phase and amplitude for one or more of the plurality of antenna elements ( 300 ) of the reconfigurable phased array antenna ( 214 ) to spread a beam width.   
     
     
         21 . The apparatus of  claim 20 , wherein using ( 604 ) a lesser number than a total number of the plurality of antenna elements ( 300 ) further comprises one of:
 selecting ( 604 ) one antenna element ( 300 ) from the plurality of antenna elements ( 300 ) of the reconfigurable phased array antenna ( 214 ); and   selecting ( 604 ) a sub-array of two or more antenna elements ( 300 ) from the plurality of antenna elements ( 300 ) of the reconfigurable phased array antenna ( 214 ).   
     
     
         22 . The apparatus of  claim 20 , wherein the spoiled beam is generated by introducing a phase difference that alters a coherence of the received signals at the reconfigurable phased array antenna ( 214 ). 
     
     
         23 . The apparatus of  claim 19 , wherein tracking the signal source ( 102 ) comprises determining an initial pointing vector comprised of an azimuth and elevation and an initial tracking vector comprised of a flight path for the reconfigurable phased array antenna ( 214 ) based on ephemeris data for the signal source ( 102 ) relative to a current terrestrial or airborne location of a user terminal ( 104 ). 
     
     
         24 . The apparatus of  claim 19 , wherein the reconfigurable phased array antenna ( 214 ) is stationary prior to selecting the field of regard. 
     
     
         25 . The apparatus of  claim 19 , wherein the reconfigurable phased array antenna ( 214 ) is slewed to establish an initial pointing vector comprised of an azimuth and elevation prior to selecting the field of regard, but the reconfigurable phased array antenna ( 214 ) is not slewed once the field of regard is selected.