Patent Publication Number: US-7710332-B2

Title: Mobile communications device with a compact-sized three-dimensional antenna

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to a mobile communications device, and more particularly to a mobile communications device with a compact-sized three-dimensional antenna. 
   2. Description of the Related Art 
   Internal antennas are increasingly popular and widely used in mobile communications devices (e.g. cellular phones). Recently, planner inverted F antennas (PIFAs) and monopole antennas have become available. 
   A planner inverted F antenna is required to be spaced apart from a circuit board of a mobile communications device at a predetermined vertical distance, and no electronic components are allowed between the planner inverted F antenna and the circuit board. However, the allotted antenna area and predetermined vertical distance are limited by the dimensions of the mobile communications device which is generally compact. As a result, the performance of the antenna measured in frequency width, radiation efficiency, and gain is hindered. 
   Similar with PIFAs, a monopole antenna is required to be spaced apart from a circuit board of a mobile communications device at a predetermined distance. However, the predetermined distance is horizontal, and also no electronic components are allowed between the monopole antenna and the circuit board. That is, a clearance zone is required between the monopole antenna and the circuit board to avoid negative disturbances to the monopole antenna. Generally, the clearance zone required by a monopole antenna exceeds 15 mm, a significantly large space when considering compact communication devices. 
   BRIEF SUMMARY OF THE INVENTION 
   The invention provides a monopole antenna requiring only a 6.8 mm clearance zone from the circuit board, thus eliminating clearance zone space, which can be used for arrangement of other electronic components in a mobile communications device or further device shrinkage. 
   The mobile communications device in accordance with an exemplary embodiment of the invention includes a circuit board and a monopole antenna. The monopole antenna includes a feed part electrically connected to the circuit board and directed away from the circuit board at an acute angle, a connecting part extending from the feed part in a direction substantially perpendicular to the circuit board, a first radiating part extending from the connecting part, and a second radiating part also extending from the connecting part. 
   The above-mentioned mobile communications device can be modified in various ways. In another exemplary embodiment of the invention, for example, the acute angle is about thirty degrees. 
   In another exemplary embodiment of the invention, as another example, the second radiating part includes a first strip substantially parallel to the first radiating part. 
   In another exemplary embodiment of the invention, the first radiating part is about 1 mm from the first strip of the second radiating part. 
   In another exemplary embodiment of the invention, the first radiating part is wider than the first strip of the second radiating part. 
   In another exemplary embodiment of the invention, the first radiating part is about 2 mm in width. 
   In another exemplary embodiment of the invention, the first strip of the second radiating part is about 0.8 mm in width. 
   In another exemplary embodiment of the invention, the second radiating part further includes a second strip extending from the first strip toward the feed part. 
   In another exemplary embodiment of the invention, the second strip of the second radiating part runs substantially parallel to the first radiating part. 
   In another exemplary embodiment of the invention, the mobile communications device further includes a mount with the monopole antenna affixed thereto. 
   In another exemplary embodiment of the invention, the mount is made of plastic. 
   In another exemplary embodiment of the invention, the monopole antenna is affixed to the mount by ultrasonic heat staking. 
   In another exemplary embodiment of the invention, the monopole antenna is disposed at a bottom of the communications device. 
   In another exemplary embodiment of the invention, the circuit board is about 6.8 mm from an edge of the circuit board of the communications device. 
   In another exemplary embodiment of the invention, the mobile communications device further includes a screw affixing the feed part of the monopole antenna to the circuit board. 
   In another exemplary embodiment of the invention, the monopole antenna is made of phosphor bronze. 
   The monopole antenna is capable of operating at a frequency of 824-894 MHz, 880-960 MHz, 1710-1880 MHz, and 1850-1990 MHz. Following experimentation, the monopole antenna of the invention requires only a 6.8 mm clearance zone from the circuit board, thus eliminating clearance zone space, which can be used for arrangement of other electronic components in the mobile communications device or further device shrinkage. 
   Furthermore, the monopole antenna made of phosphor bronze shows stable operating performance and is inexpensive. In addition, the monopole antenna is affixed to the plastic mount by ultrasonic heat staking, thus effectively simplifying the structure of the mobile communications device. 
   The feed part of the monopole antenna is firmly connected to the circuit board by a screw, which is easy and fast during assembly. Furthermore, such a connection is reliable. Even when the mobile communications device impacts the ground, the monopole antenna does not separate from the circuit board. 
   Meanwhile, the positioning of the monopole antenna, disposed at the bottom of the mobile communications device, is distant from the receiver, thus significantly reducing specific absorption rate (SAR) in the human body. 
   A detailed description is given in the following embodiments with reference to the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
       FIG. 1  depicts the rear of a mobile communications device in accordance with the invention; 
       FIG. 2  is a perspective exploded diagram of the mobile communications device of  FIG. 1 ; 
       FIG. 3A  depicts the monopole antenna of  FIG. 2 , observed from the x-direction; 
       FIG. 3B  depicts the monopole antenna of  FIG. 2 , observed from the y-direction; and 
       FIG. 3C  depicts the monopole antenna of  FIG. 2 , observed from the z-direction. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims. 
   Referring to  FIGS. 1 and 2 , a mobile communications device  20  (e.g. a cellular phone) includes a circuit board  22 , a monopole antenna  26 , and a mount  24 . The circuit board  22  has a plurality of electronic components  221  and  223  mounted thereon and is spaced apart from the bottom edge  202  of the communications device  20  at a distance D 1  in the horizontal direction (y-direction). Thus, a clearance zone  206  is formed between the circuit board  22  and the bottom edge  202  of the communications device  20  for receiving the mount  24 . In this embodiment, the monopole antenna  26  is made of phosphor bronze and the mount  24  is made of plastic. The monopole antenna  26  is affixed to the mount  26  by ultrasonic heat staking. 
   The monopole antenna  26  includes a feed part  261 , a connecting part  262  extending from the feed part  261 , a first radiating part  263  extending from the feed part  261 , and a second radiating part  264  also extending from the feed part  261 . All parts of the monopole antenna  26  are described in detail in the following: 
   The feed part  261  of the monopole antenna  26  is electrically connected to the feed point (not shown) of the circuit board  22  and affixed by a screw  28 . Referring to  FIG. 3A , the feed part  261  is directed away from the circuit board  22  which is situated in a plane, at an angle θ 1 . In this embodiment, θ 1  is about thirty degrees. 
   The connecting part  262  connects the feed part  261 , the first radiating part  263 , and the second radiating part  264 . Note that the connecting part  262  runs substantially perpendicular to the circuit board  22 . 
   The first radiating part  263  handles high frequency signals of 1710-1880 MHz and 1850-1990 MHz. Referring to  FIG. 3B , the width D 2  of the first radiating part  263  is about 2 mm. 
   The second radiating part  264  is longer than the first radiating part  263  for handling low frequency signals of 824-894 MHz and 880-960 MHz. The second radiating part  264  includes a first strip  2642  extending substantially parallel to the first radiating part  263  from the connecting part  262 , and a second strip  2644  extending substantially parallel to the first radiating part  263  from the first strip  2642  toward the feed part  261  as shown in  FIG. 3C . The distance D 2  between the first radiating part  263  and the first strip  2642  of the second radiating part  264  is very small in order to generate a coupling effect therebetween for promoting the radiation efficiency. In this embodiment, D 2 =1 mm. The width W 1  of the first radiating part  263  exceeds the width W 2  of the first strip  2642  of the second radiating part  264 . In this embodiment, W 1 =2 mm and W 2 =0.8 mm. 
   The invention provides a compact-sized three-dimensional monopole antenna capable of operating at frequencies of 824-894 MHz, 880-960 MHz, 1710-1880 MHz, and 1850-1990 MHz. Following experimentation, the monopole antenna requires only 6.8 mm clearance zone from the circuit board, thus eliminating clearance zone space, which can be used for arrangement of other electronic components in the mobile communications device or further device shrinkage. 
   Furthermore, the monopole antenna  26  made of phosphor bronze shows stable operating performance and is inexpensive. In addition, the monopole antenna  26  is affixed to the plastic mount  24  by ultrasonic heat staking, thus effectively simplifying the structure of the mobile communications device  20 . 
   The feed part  261  of the monopole antenna  26  is firmly connected to the circuit board  22  by a screw  28 , which is easy and fast during assembly. Furthermore, such a connection is reliable. Even when the mobile communications device  20  impacts the ground, the monopole antenna  26  does not separate from the circuit board  22 . 
   Meanwhile, the positioning of the monopole antenna  26 , disposed at the bottom of the mobile communications device  20 , is distant from the receiver (not shown), thus significantly reducing specific absorption rate (SAR) in the human body. 
   While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.