Tunable matching network for antenna systems

Abstract

A communication system is provided, including an antenna, a matching network coupled to the antenna, a controller configured to control the matching network, and a look-up table coupled to the controller. The look-up table includes characterization data according to frequency bands and conditions. The controller is configured to refer to the look-up table to determine optimum impedance for a frequency band selected under a condition detected during a time interval, and adjust the matching network to provide the optimum impedance.

What is claimed is: 
     
         1 . A communication system comprising:
 an antenna;   a matching network coupled to the antenna;   a controller configured to control the matching network; and   a look-up table coupled to the controller, the look-up table including characterization data according to frequency bands and conditions,   
       wherein
 the controller is configured to refer to the look-up table to determine optimum impedance for a frequency band selected and under a condition detected during a time interval, and adjust the matching network to provide the optimum impedance. 
 
     
     
         2 . The communication system of  claim 1 , wherein
 the matching network comprises a plurality of first cells coupled to a plurality of switches, respectively, wherein   each of the plurality of first cells comprises one or more components.   
     
     
         3 . The communication system of  claim 2 , wherein
 the controller is configured to adjust the matching network by turning on one or more of the plurality of switches to provide the optimum impedance for the frequency band and the condition, based on one or more of the plurality of first cells coupled respectively to the one or more of the plurality of switches that are turned on.   
     
     
         4 . The communication system of  claim 2 , wherein the matching network further comprises:
 a plurality of second cells coupled to the plurality of switches, respectively, wherein each of the plurality of second cells comprises one or more components.   
     
     
         5 . The communication system of  claim 4 , wherein
 the controller is configured to adjust the matching network by turning on one or more of the plurality of switches to provide the optimum impedance for the band and the condition, based on one or more of the plurality of first cells coupled respectively to the one or more of the plurality of switches that are turned on and one or more of the plurality of second cells coupled respectively to the one or more of the plurality of switches that are turned on.   
     
     
         6 . The communication system of  claim 2 , wherein the matching network further comprises:
 a third cell comprising one or more components, the third cell having a first end portion coupled to a first port of the matching network and a second end portion coupled to a second port of the matching network, wherein   the third cell is in operation to provide the optimum impedance for a nominal condition and a nominal band, and the controller is configured to turn on one or more of the plurality of switches to adjust the optimum impedance when the condition, the band or both of the above changes.   
     
     
         7 . The communication system of  claim 1 , further comprising:
 one or more sensors that detect the condition during the time interval, wherein   the controller receives information on the condition from the one or more sensors and uses the information upon referring to the look-up table.   
     
     
         8 . The communication system of  claim 1 , wherein
 the conditions include environments of the communication system including free space, presence of a head, a hand, laps, wood, metal, or other interference-causing objects, with different positions and angles.   
     
     
         9 . The communication system of  claim 4 , wherein
 the plurality of first cells are coupled on one side of the plurality of switches, respectively, and the plurality of second cells are coupled on the other side of the plurality of switches, respectively, wherein   each of the first and second cells comprises one or more capacitors.   
     
     
         10 . The communication system of  claim 1 , wherein
 the matching network comprises a plurality of cells and a plurality of switches coupled to the plurality of cells, wherein each cell comprises one or more components, and wherein   the controller is configured to adjust the matching network by turning on one or more of the plurality of switches to provide the optimum impedance for the frequency band and the condition, based on components values of one or more of the plurality of cells coupled to the one or more of the plurality of switches that are turned on, the component values being adjusted by considering parasitics effects to provide a linear behavior in an impedance-versus-state figure.   
     
     
         11 . The communication system of  claim 1 , wherein
 the matching network comprises a plurality of cells and a plurality of switches coupled to the plurality of cells, wherein each cell comprises one or more capacitors, one or more inductors, or a combination of one or more capacitors and one or more inductors.   
     
     
         12 . The communication system of  claim 1 , wherein
 the matching network comprises a plurality of cell, a plurality of switches coupled to the plurality of cells, and a phase shifter coupled to the plurality of switches and the plurality of cells, and wherein   the controller is configured to adjust the matching network by turning on one or more of the plurality of switches; and   the phase shifter is configured to adjust impedance values provided by one or more of the plurality of cells coupled to the one or more of the plurality of switches that are turned on.   
     
     
         13 . The communication system of  claim 12 , wherein
 the phase shifter is configured to have a composite right and left hand (CRLH) structure to adjust the impedance values to simultaneously provide two or more optimum impedances for two or more frequency bands, respectively.   
     
     
         14 . A method for impedance matching of a communication system including an antenna and a matching network, comprising:
 obtaining data associated with antenna characteristics for frequency bands and conditions;   storing the data in a look-up table according to the frequency bands and the conditions; and   adjusting the matching network with reference to the data in the look-up table to provide optimum impedance for a frequency band selected and under a condition detected during a time interval.   
     
     
         15 . The method of  claim 14 , further comprising:
 configuring the matching network to include a plurality of cells and a plurality of switches to provide a plurality of impedance states, each impedance state providing optimum impedance for a frequency band and a condition, wherein   the storing the data in the look-up table comprises storing the plurality of impedance states according to the frequency bands and the conditions.   
     
     
         16 . The method of  claim 15 , wherein
 the adjusting the matching network comprises turning on one or more of the plurality of switches coupled to one or more of the plurality of cells corresponding to the impedance state providing the optimum impedance for the frequency band and the condition during the time interval.   
     
     
         17 . The method of  claim 15 , wherein
 each of the plurality of cells comprises one or more capacitors, one or mode inductors, or a combination of one or more capacitors and one or more inductors.   
     
     
         18 . The method of  claim 14 , further comprising:
 detecting the condition during the time interval by using one or more sensors, wherein   the adjusting the matching network comprises referring to the look-up table by using information on the condition to provide the optimum impedance for the frequency band and the condition during the time interval.   
     
     
         19 . The method of  claim 14 , further comprising:
 configuring the matching network to include a plurality of first cells, a plurality of second cells, and a plurality of switches coupled respectively to the plurality of first cells on one side and respectively to the plurality of second cells on the other side, and wherein   each of the first and second cells comprises one or more capacitors.   
     
     
         20 . The method of  claim 15 , further comprising
 obtaining parasitic values associated with a package for frequency bands and conditions;   adjusting the plurality of impedance states by considering the parasitic values to provide a linear behavior in an impedance-versus-state figure.   
     
     
         21 . The method of  claim 14 , further comprising
 configuring the matching network to include a plurality of cell, a plurality of switches coupled to the plurality of cells, and a phase shifter coupled to the plurality of switches and the plurality of cells, wherein   the adjusting the matching network comprises turning on one or more of the plurality of switches, and wherein   the phase shifter is configured to adjust impedance values provided by one or more of the plurality of cells coupled to the one or more of the plurality of switches that are turned on.   
     
     
         22 . The method of  claim 21 , wherein
 the phase shifter is configured to have a composite right and left hand (CRLH) structure to adjust the impedance values to simultaneously provide two or more optimum impedances for two or more frequency bands, respectively.   
     
     
         23 . A matching network for an antenna system, comprising:
 a plurality of switches; and   a plurality of cells coupled to the plurality of switches, wherein   the plurality of cells are configured to provide a plurality of impedance values, each impedance value is optimized for a frequency band under a condition, and   one or more of the plurality of switches are controlled to turn on depending on the frequency band selected and the condition detected to engage one or more of the plurality of cells providing the optimum impedance value for the frequency band and the condition.