Patent Publication Number: US-6992627-B1

Title: Single and multiband quarter wave resonator

Description:
This application claims the benefit of priority pursuant to 35 USC §119(e)(1) from the provisional patent application filed pursuant to 35 USC §111(b): as Ser. No. 60/157,945 on Oct. 6, 2000. 
   This is a continuation-in-part of application Ser. No. 09/382,179 filed on Aug. 24, 1999, now U.S. Pat. No. 6,239,765 the benefit of priority from which is hereby claimed pursuant to the provisions of 35 USC §120. 

   FIELD OF THE INVENTION 
   The present invention relates to an antenna assembly for a wireless communication device, such as a cellular telephone. Particularly, the present invention relates to compact antenna assemblies including a GPS-frequency quarter wave resonator and a single or multiple band quarter wave resonator of associated wireless communication devices. 
   BACKGROUND OF THE INVENTION 
   Known wireless communications devices such as hand-held cell phones and data modems (LANs) typically are equipped with an external wire antenna (whip), which may be fixed or telescoping. Such antennas are inconvenient and susceptible to damage or breakage. The overall size of the wire antenna is relatively large in order to provide optimum signal characteristics. Furthermore, a dedicated mounting means and location for the wire antenna are required to be fixed relatively early in the engineering process. 
   Several other antenna assemblies are known, including: 
   Quarter Wave Straight Wire Antenna 
   This is a ¼ wavelength external antenna element, which operates as one side of a half-wave dipole. The other side of the dipole is provided by the ground traces of the transceiver&#39;s printed wiring board (PWB). The external ¼ wave element may be installed permanently at the top of the transceiver housing or may be threaded into place. The ¼ wave element may also be telescopically received into the transceiver housing to minimize size. The ¼ wave straight wire adds from 3–6 inches to the overall length of an operating transceiver. 
   Coiled Quarter Wave Wire Antenna 
   An antenna having an external small diameter coil that exhibits ¼ wave resonance, and which is fed against the ground traces of the transceiver&#39;s PWB to form an asymmetric dipole. The coil may be contained in a molded member protruding from the top of the transceiver housing. A telescoping ¼ wave straight wire may also pass through the coil, such that the wire and coil are both connected when the wire is extended, and just the coil is connected when the wire is telescoped down. The transceiver overall length is typically increased by ¾–1 inch by the coil. 
   Planar Inverted F Antenna (PIFA) 
   An antenna having an external conducting plate which exhibits ¼ wave resonance, and which is fed against the ground traces of the PWB of a transceiver to form an asymmetric dipole. The plate is usually installed on the back panel or side panel of a transceiver and adds to the overall volume of the device. 
   Patch 
   An antenna including a planar dielectric material having a resonant structure on one major surface of the dielectric and a second ground plane structure disposed on the opposite major surface. A conductive post may electrically couple (through the dielectric) the resonant structure to a coaxial feedline. 
   GPS 
   GPS antennas for portable or mobile equipment generally have the form of a microstrip patch or a quadrifilar helix. The microstrip patch may be installed internally in some wireless communications devices, and size for 1575 MHz is typically reduced by dielectric loading, which also increases costs and weight. The quadrifilar helix is of substantial size, and is mounted externally, where it is subject to damage. The manufacturing cost of either the patch or quadrifilar helix is greater than for an antenna according to the present invention. 
   Additionally, there have been numerous efforts in the past to provide an antenna inside a portable radio communication device. Such efforts have sought at least to reduce the need to have an external whip antenna because of the inconvenience of handling and carrying such a unit with the external antenna extended. 
   SUMMARY OF THE INVENTION 
   In view of the above-mentioned limitations of the prior art antennas, it is an object of the present invention to provide an antenna for use with a portable wireless communications device. 
   It is another object of the invention to provide an antenna unit which is lightweight, compact, highly reliable, and efficiently produced. 
   The present invention replaces the external wire antenna of a wireless communication device with a printed dielectric substrate element which is disposed within the housing of a wireless device and closely-spaced to the printed wiring board (PWB) and antenna feedpoint of the wireless device. Electrical connection to the wireless device&#39;s PWB may be achieved through automated production equipment, resulting in cost effective assembly and production. Electrical performance of the internal (embedded) antenna in wireless systems is nominally equal to that of a conventional wire antenna. 
   It is an object of the present invention to provide an antenna assembly which can resolve the above shortcomings of conventional antennas. Additional objects of the present invention include: the elimination of the external antenna and its attendant faults such as susceptibility to breakage and impact on overall length of the transceiver; the provision of an internal antenna that can easily fit inside the housing of a wireless transceiver such as a cell phone, with minimal impact on its length and volume; the provision of a cost effective antenna for a wireless transceiver, having electrical performance comparable to existing antenna types; and, the reduction in SAR (specific absorption rate) of the antenna assembly, as the antenna exhibits reduced transmit field strength in the direction of the user&#39;s ear for hand held transceivers such as a cellular telephone, when compared to the field strength associated with an external wire type antenna system. 
   In a preferred embodiment, the resonator devices may exhibit resonant frequency ranges within the GPS, 860–990 Mhz, and 1710–1880 Mhz frequency ranges. Alternatively, the resonator devices may operate at the GPS and a single band, such as 860–990 MHz or 1710–1880 MHz ranges. 
   It is an object of the present invention to provide a GPS (Global Positioning System) antenna quarter wave resonator and single or multiband antenna quarter waves resonator for wireless communications frequencies that are co-located on a common second conductor to form an asymmetrical dipole dual or multiband antenna system with separate feed for the GPS antenna portion. The common second conductor may be supplied by the PWB of a wireless communication device such as a cell phone. The GPS and wireless band resonators may be formed as printed circuits on a dielectric substrate using known circuit board fabrication processes and techniques, resulting in a low cost antenna suitable for high volume manufacturing. 
   The present invention provides an antenna assembly including a first conductive trace element disposed upon the resonator element. The resonant frequency range of the trace may be selected to exhibit ¼ wave resonance. In the preferred embodiment the first printed circuit element is rectangular having a thickness in the range 0.010–0.125 inches. Alternatively, the conductive trace may be printed on any number of conventional dielectric materials having a low to moderate dielectric loss such as plastics and fiberglass. Furthermore, the compact size of the resonator element may conform to available volume in the housing of a wireless transceiver such as a cellular telephone. The antenna assembly may be excited or fed with 50 ohm impedance, which is a known convenient impedance level found at the receiver input/transmitter output of a typical wireless transceiver. 
   The combined antenna system allows a GPS-based mobile station locating system to be incorporated with wireless devices such as cell phones. The non-GPS portion of the antenna system may be configured to operate over cell phone bands of interest, such as 824–894 MHz/1850–1990 MHz or 880–960 MHz/1750–1880 MHz. 
   The above and other objects and advantageous features of the present invention will be made apparent from the following description with reference to the accompanying drawings, in which like reference characters designate the same or similar parts throughout the drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above set forth and other features of the invention are made more apparent in the following Detailed Description of Preferred Embodiments when read in conjunction with the attached drawings, wherein: 
       FIG. 1  illustrates a perspective view of a wireless communications device utilizing an antenna assembly according to the present invention; 
       FIG. 2 . is a first side elevational view of the resonator element of the antenna assembly of  FIG. 1 ; 
       FIG. 3  is a second side elevational view of the resonator element of the antenna assembly of  FIG. 1 ; 
       FIG. 4  illustrates a perspective view of a wireless communications device utilizing another embodiment of an antenna assembly according to the present invention; 
       FIG. 5  illustrates a side elevational view of a multiple-band resonator element according to the present invention; and 
       FIG. 6  illustrates yet another view of a wireless communications device utilizing an antenna assembly according to the present invention. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 1  illustrates an antenna assembly  12  being disposed within a wireless communications device  10 , such as a cellular telephone or PDA device. The antenna assembly  12  includes a resonator element  14  having a pair of opposed surfaces  16 ,  18  and a ground plane element  20 . The ground plane element  20  may be the internal ground plane of a printed wiring board (PWB) of the communications device  10 . Ground plane element  20  includes a dimension of approximately ¼ wavelength or greater. In preferred embodiments, the antenna assembly  12  can be implemented to transmit and receive on desired frequencies, including analog or digital U.S. or European cell phone bands, PCS cell phone bands, 2.4 GHz BLUETOOTH™ bands, or other frequency bands as would be obvious to one skilled in the art. 
   The antenna assembly  12 , disposed near the upper portion of the device  10  (away from the user&#39;s hand during operation), is received and incorporated within the housing  22  of the device  10 . Although the antenna assembly  12  can be installed in locations within or external to the housing  22 , it is presently preferred that it be disposed within the housing  22 . Wireless communication device  10  contains electrical apparatus, such as a receiver and/or transmitter, herein referred for convenience together as a transceiver component  24 . 
   As illustrated in the  FIGS. 1 and 2 , the resonator element  14  may be disposed in substantially perpendicular relationship to the ground plane element  20 . A first conductor trace  26  is disposed upon a surface  16  of the resonator element  14 , and second conductor traces  28   a,b,c  are disposed upon the opposite surface  18  of the resonator element  14 . The lower edge of each of the outer second conductor traces  28   a,c  is within approximately 1–4 mm (vertical distance) from the ground plane  20 . The outer second conductor traces  28   a,c  are coupled to the signal ground proximate connection region  32 . The central second conductor trace  28   b  is operatively coupled to the transceiver signal input/output componentry  24  via connection  30 . 
   The first and second conductor traces  26 ,  28  of the antenna assembly  12  are disposed upon respective first and second surfaces  16 ,  18  of the resonator element  14 , which may be a printed wiring board (PWB)  40  or similar materials capable of supporting the conductor traces. Both the first and second conductor traces  26 ,  28  may be disposed upon the substrate  40  using known circuit fabrication techniques, such as surface printing, photolithography, and etching processes. The dimensions of the resonator element  14  may be varied to conform to a portion of the housing  22 . Those skilled in the arts will appreciate that the design and selection of either the first or second planar elements  22 , 24  with reference to a particular wireless communication device may result in such complex shapes. 
   Referring to  FIGS. 2 and 3 , a particular GPS resonator device  14  is disclosed. Resonator device  14  includes a substrate  40 , such as a double sided printed wiring board having a relative dielectric constant in the range 2–10. The substrate  40  may be of Duroid or glass fiber, or known dielectric printed circuit board material. The substrate element  40  may be a dielectric PC board having a thickness between 0.005″ to 0.125″ thick. A flexible PCB substrate may also be practicable.  FIG. 2  illustrates the resonator device  14  disposed in substantially perpendicular relationship to the ground plane element  20 , such as the internal ground plane of the wireless communications device  10 , and being fed directly from the signal lines on the PCB at connection regions  30  and  32 . An alternative antenna  12  feed approach is disclosed in  FIG. 3 , where the resonator device  14  is coupled to a coax feedline  70  and a separate conductive plate element of approximately 1 wavelength or greater dimension such as the ground plane  20  of the wireless device  10 . The center conductor of the coax line  70  is coupled at connection  30  to the central second conductor trace  28   b , while the shield conductors of the coax line  70  are coupled to the second conductor traces  28   a,c  and the separate ground conductor element  20 . 
   Conductor elements  26 , 28  of the resonator device  14  preferably have thicknesses in the range 0.0005–0.01 inches. The first conductor trace element  26  is an electrical quarter wave resonator for 1575 MHz. The second conductor trace elements  28  form a feed network. Electrical connection between conductor trace elements  26  and central second conductor trace  28   b  is via capacitive coupling. Conductor element  28   b  is connected to the RF port of the wireless device at connection  30 . 
   Referring now to  FIG. 4 , a second embodiment of the present invention is disclosed to include a second antenna  54  having a dielectric substrate  56  and disposed within a wireless communications device at an end opposite to the first resonator element  14 . The antenna assembly  54  is likewise incorporated within the handset of a communications device  10 . The second printed antenna  54  may include a single- or multiple-band wave resonator disposed relative to the ground plane  20  at an angle of 0–90 degrees. The ground plane  20  is preferably the ground traces of the PWB of a wireless communications device  10 . Referring particularly to  FIG. 5 , the second resonator element  54  may include a multiple-band resonator as disclosed in the assignees&#39;s U.S. patent application Ser. No. 09/382,179, herein incorporated by reference in its entirety.  FIG. 5  depicts a tri-band antenna assembly  54  functioning across a cellular band (880–960 MHz.), a PCS band (1710–1880 MHz.) and the BLUETOOTH™ band (2.4–2.5 GHz). Cellular and PCS band operation is effected through first conductor trace  140 . BLUETOOTH™ band operation is effected through conductor trace  142 .  FIG. 5  illustrates an alternative feed approach, wherein the antenna assembly  54  is fed via coax signal lines  70 . In this embodiment, the conductor trace  140  is coupled to the shield conductor of the coax  70  at region  144  and to the separate conductive panel  20 . Center conductor of coax  70  (to signal generating circuitry  24 ) is coupled to the antenna element  54  via feedpoint  146 . Conductor trace  142  is coupled to the shield conductor of the other coax  70  at region  148  and to the separate conductive panel  20 . As described with reference to the earlier embodiments, the separate conductive panel  20  may be the internal ground plane of the printed wiring board of the wireless device. Conductor trace  142  is also coupled to the center conductor of coax  70  at feedpoint  150 . 
     FIG. 6  illustrates a perspective view of a third embodiment of a GPS and wireless frequency band antenna  14 ,  54 . A GPS quarter wave resonator  14  is fed by microstrip transmission line  60  disposed upon a dielectric substrate element  62  opposite a ground plane  64 . A single or multiband quarter wave resonator  54  for a wireless communications band or bands may be utilized on dielectric substrate  56 . The dielectric substrates  40 ,  56 ,  62  may be mechanically connected for structural integrity. 
   Although the invention has been described in connection with particular embodiments thereof other embodiments, applications, and modifications thereof which will be obvious to those skilled in the relevant arts are included within the spirit and scope of the invention.