Abstract:
The instant disclosure provides an antenna system with a generically small ground plane and a generic antenna radiating module, wherein the system further includes a matching circuit and a tunable capacitor each bring integrated with the ground plane and antenna in a novel configuration which provides improved antenna performance across multiple antenna resonances.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation in part (CIP) of U.S. Ser. No. 14/286,974, filed May 23, 2014; 
     which claims benefit of U.S. Provisional Ser. No. 61/826,493, filed May 23, 2012; 
     the contents of each of which are hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to antenna systems; and more particularly, to such antenna systems configured for with a novel frequency tuning and matching architecture. 
     2. Description of the Related Art 
     Active antennas are currently used in a wide variety of applications and are configured to performs various functions, including: (i) altering the radiation pattern; (ii) varying an electrical length of radiating elements; (iii) varying antenna impedance; (iv) shifting the antenna resonance; (v) compensating for antenna loading conditions (ex: device against the head and/or hand); (vi) increasing isolation in between antennas in MIMO systems; and (vii) decreasing the correlation coefficient within antennas, phase shifters and other complex features. 
     Of concern in the instant disclosure is the need to vary the antenna resonance and provide a corresponding match for a particular ground plane size and electromagnetic environment using commercially available components. 
     Working within newer LTE bands, including the frequencies around 700 MHz, the antenna design process is complicated due to the physical space permitted for the antenna being significantly less than the physical space needed for a conductor. Thus, the antenna is generally required to be electrically small. This results in difficulties to achieve a resonance and then the required matching to comply with the required bandwidth. 
     There is a significant need to develop improved antenna systems and related schemes for obtaining resonance and matching with small ground plane sizes. 
     SUMMARY OF THE INVENTION 
     The instant disclosure provides an antenna system with a generically small ground plane and a generic antenna radiating module, wherein the system further includes a matching circuit and a tunable capacitor each bring integrated with the ground plane and antenna in a novel configuration which provides improved antenna performance across multiple antenna resonances. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1  (A-C) show an antenna system with a novel configuration for achieving frequency tuning and matching across multiple antenna resonances. 
         FIG. 2  shows a matching circuit for use in one or more embodiments. 
         FIG. 3  shows a bifurcated transmission line configured as a switchable bypass in accordance with certain embodiments. 
         FIG. 4  shows a frequency spectrum with respect to the antenna system in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, for purpose of illustration and not limitation, detailed descriptions are provided for enabling those having skill in the art to make and use the inventive embodiments. 
       FIGS. 1  (A-C) show an antenna system with a novel configuration for achieving frequency tuning and matching across multiple antenna resonances. 
     The antenna system  100  comprises a substrate  106 , such as a circuit board substrate, extending about a longitudinal axis L′ to define a length thereof, and having a width perpendicular to the longitudinal axis. In an example, the length and width of the substrate can each be about 50 mm. The substrate  106  is further characterized wherein on a top surface of the substrate is disposed each of: a ground plane conductor  101 , and an antenna module  102 ; the antenna module being disposed adjacent to the ground plane conductor and spaced apart therefrom to form a longitudinal gap  105  therebetween. The ground plane conductor  101  comprises a channel  109  extending inwardly from a side of the ground conductor that is adjacent to the antenna module. A feed conductor  110  extends longitudinally about the top surface of the substrate from the antenna module to a terminus of the channel, the feed conductor being isolated from the ground plane conductor via a channel gap  111  surrounding the feed conductor. A ground connection element  112  traverses the longitudinal gap from the ground plane conductor to a ground connection of the antenna module. The ground connection is not shown, the ground connection is disposed between a bottom surface of the antenna module and the top surface of the circuit board, but is widely known in the art, and typically would include a contact pad between the antenna and circuit board. The antenna module is configured to couple with the ground plane conductor via the ground connection element. A matching circuit  108  is coupled to each of said feed conductor and said ground plane conductor  101 . A tunable capacitor  107  is coupled to each of said feed conductor and said ground plane conductor  101 . 
     In an embodiment, the ground plane conductor  101  comprises a pair of longitudinal ground conductors  201   a ;  201   b , respectively, separated by the channel  109 , wherein the longitudinal ground conductors and the feed conductor collectively form a coplanar waveguide  104 . 
     In a preferred embodiment, the tunable capacitor  107  is disposed between the matching circuit and the antenna module  102 . 
     As illustrated in  FIG. 2 , the matching circuit  108  can comprise any matching circuit configuration within the knowledge in the art. For example, in an embodiment the matching circuit can comprise one or more lumped components LC 1 ; LC 3  configured in series. In another embodiment, the matching circuit can comprise one or more lumped components LC 2 ; LC 4  configured in shunt. Any combination of series and shunt components may be similarly implemented. The lumped components may comprise resistors, capacitors, or inductors. Other components can be similarly implemented. 
     In another embodiment, as illustrated in  FIG. 3 , the antenna system further comprises a bifurcated transmission line  300 . 
     In the bifurcated transmission line, the feed conductor  110  is configured with a first end  306  and a second end  307  each disposed arbitrarily along a longitudinal portion of the feed conductor that is captured within the channel  109 . The feed conductor is bifurcated at the first end  306  to form a first feed segment  301  and a second feed segment  302 . The first and second feed segments are combined at the second end  307 . A longitudinal ground strip  303  is disposed longitudinally between the first and second feed segments. A first radiofrequency (RF) switch  304  is disposed at the first end of the feed conductor, and a second RF switch  305  is disposed at the second end of the feed conductor. Each of the tunable capacitor  107  and the matching circuit  108  are coupled to the first feed segment  301  between the first and second RF switches. The second feed segment is configured as a switchable bypass. 
     In an embodiment, a first of the longitudinal ground conductors  201   a , the first feed segment  301 , and the longitudinal ground strip  303  collectively form a first coplanar waveguide disposed between the first and second RF switches. 
     In another embodiment, a second of the longitudinal ground conductors  201   b , the second feed segment  302 , and the longitudinal ground strip  303  collectively form a second coplanar waveguide disposed between the first and second RF switches. 
     In this regard, the antenna system may be configured with a pair of coplanar waveguides disposed between the first and second RF switches along the transmission line. 
     In preliminary experimentation, an antenna system was configured in accordance with the above descriptions using a substrate having dimensions of 50 mm×50 mm. For simplicity, the antenna described in commonly owned international PCT publication WO/WO2014058926A1, published Apr. 17, 2014, titled “LOW COST ULTRA-WIDEBAND LTE ANTENNA” was integrated with the system; the contents of which are hereby incorporated by reference. The resulting spectrum as illustrated in  FIG. 4  was obtained using standard testing instrumentation. 
     
       
         
               
             
               
               
             
           
               
                   
               
               
                 Reference Signs List 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 longitudinal axis (L’) 
               
               
                   
                 antenna system (100) 
               
               
                   
                 ground plane conductor (101) 
               
               
                   
                 antenna module (102) 
               
               
                   
                 center pin (103) 
               
               
                   
                 coplanar waveguide (104) 
               
               
                   
                 longitudinal gap (105) 
               
               
                   
                 substrate (106) 
               
               
                   
                 tunable capacitor (107) 
               
               
                   
                 matching circuit (108) 
               
               
                   
                 channel (109) 
               
               
                   
                 feed conductor (110) 
               
               
                   
                 channel gap (111) 
               
               
                   
                 ground connection element (112) 
               
               
                   
                 longitudinal ground conductors (201a; 201b) 
               
               
                   
                 Lumped components (LC 1 -LC 4 ) 
               
               
                   
                 bifurcated transmission line (300) 
               
               
                   
                 first feed segment (301) 
               
               
                   
                 second feed segment (302) 
               
               
                   
                 longitudinal ground strip (303) 
               
               
                   
                 first radiofrequency (RF) switch (304) 
               
               
                   
                 first radiofrequency (RF) switch (305) 
               
               
                   
                 first end of feed conductor (306) 
               
               
                   
                 second end of feed conductor (307)