Patent Publication Number: US-2015061954-A1

Title: Antenna  assembly

Description:
FIELD 
     The subject matter herein generally relates to an antenna assembly. 
     BACKGROUND 
     Antennas are usually assembled in a wireless communication device to send and/or receive signals. 
     Antennas are usually assembled in a wireless communication device to send and/or receive signals. Commonly, frequencies of the antennas are broadened by adding an additional antenna based on a main antenna. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Implementations of the present technology will now be described, by way of example only, with reference to the attached figures. 
         FIG. 1  is an isometric view of an embodiment of an antenna assembly. 
         FIG. 2  is a circuit diagram of a matching unit of the antenna assembly of  FIG. 1 . 
         FIG. 3  is a diagram showing return loss (RL) measurements of the antenna assembly of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     It will be appreciated that for simplicity and clarity of illustration, where appropriate, reference numerals have been repeated among the different figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein can be practiced without these specific details. In other instances, methods, procedures and components have not been described in detail so as not to obscure the related relevant feature being described. Also, the description is not to be considered as limiting the scope of the embodiments described herein. The drawings are not necessarily to scale and the proportions of certain parts have been exaggerated to better illustrate details and features of the present disclosure. 
     Several definitions that apply throughout this disclosure will now be presented. 
     The term “substantially” is defined to be essentially conforming to the particular dimension, shape or other word that substantially modifies, such that the component need not be exact. For example, substantially cylindrical means that the object resembles a cylinder, but can have one or more deviations from a true cylinder. The term “comprising,” when utilized, means “including, but not necessarily limited to”; it specifically indicates open-ended inclusion or membership in the so-described combination, group, series and the like. 
       FIG. 1  illustrates an embodiment of an antenna assembly  100 . The antenna assembly  100  includes a base board  11 . A ground plane  13  is positioned on the base board  11  and is configured to provide a ground for the antenna assembly  100 . An antenna  15  is formed by removing a portion of the ground plane  13  to define a slot antenna. A matching unit  17  is shown that is electronically connected to the antenna  15  and is configured to match an impedance of the antenna  15  for adjusting a bandwidth of the antenna  15 . 
     The base board  11  is a substantially flat board and can be made of a dielectric material, such as an epoxy resin glass fiber. The base board  11  includes a first surface  111  and a second surface  112  parallel with, and opposite to, the first surface  111 . The first surface  111  can be a top surface of the base board  11 . The second surface  112  can be a bottom surface of the base board  11 . 
     The ground plane  13  can be formed by a conductive foil, such as copper foil, and can be plated on the first surface  111 . That is, the first surface  111  is covered with the ground plane  13 . In the embodiment, there is no conductive foil plated on a portion of the first surface  111  (for example, a corner of the first surface  111 ) to expose a portion of the first surface  111 . 
     The antenna  15  is defined by removing a portion of the conductive foil to expose the dielectric material of the base board  10 . 
       FIG. 2  illustrates that the matching unit  17  has a radio frequency (RF) output terminal  171 . The RF output terminal  171  is positioned on the ground plane  13  and is configured to feed signal for the antenna  15 . 
     The matching unit  17  further includes a switch module  172 , a first inductor L 1 , a second inductor L 2 , and an adjustable capacitor C. The switch module  172  includes a first switch S 1  and a second switch S 2 . The first switch S 1  and the second switch S 2  can be mechanical switches, electronic switches or chips. An end of the first switch S 1  is electronically connected to the RF output terminal  171 . Another end of the first switch S 1  is electronically connected to an end of the first inductor L 1 . An end of the second switch S 2  is electronically connected to the RF output terminal  171 . Another end of the second switch S 2  is electronically connected to an end of the second inductor L 2 . Another end of the first inductor L 1  and another end of the second inductor L 2  are electronically connected together and are both electronically connected to the antenna  15  and an end of the adjustable capacitor C. Another end of the adjustable capacitor C is grounded. 
     In the embodiment, an inductance of the first inductor L 1  is about 1.8 nH, an inductance of the second inductor L 2  is about 8 nH, a capacitance of the adjustable capacitor C is about 2 pF to 4.5 pF. 
     When the first switch S 1  is turned on and the second switch S 2  is turned off, the first inductor L 1  and the adjustable capacitor C are selected to be electronically connected to the RF output terminal  171  by the turned-on first switch S 1 . Signal output by the RF output terminal  171  is transmitted to the antenna  15  by the first inductor L 1  and the adjustable capacitor C. When the first switch S 1  is turned off and the second switch S 2  is turned on, the second inductor L 2  and the adjustable capacitor C are selected to be electronically connected to the RF output terminal  171  by the turned-on second switch S 2 . Signal output by the RF output terminal  171  is transmitted to the antenna  15  by the second inductor L 2  and the adjustable capacitor C. 
     When the first inductor L 1  or the second inductor L 2  is selected, the adjustable capacitor C can be adjusted to match with the first inductor L 1  or the second inductor L 2  for matching an impedance of the antenna  15  to broaden a bandwidth of the antenna  15  in a high-frequency band. When the first switch S 1  is turned on and the second switch S 2  is turned off to select the first inductor L 1  and the adjustable capacitor C, a capacitance of the adjustable capacitor C can be adjusted to a first value (for example, 3.5 Pf), and the antenna  15  can be adjusted to a dual-frequency mode from a single-frequency mode to obtain a first bandwidth. When the first switch S 1  is turned off and the second switch S 2  is turned on to select the second inductor L 2  and the adjustable capacitor C, a capacitance of the adjustable capacitor C can be gradually increased from a second value, and a central frequency of the antenna  15  can be moved to a low-frequency range to obtain a second bandwidth. In this embodiment, the capacitance of the adjustable capacitor C is gradually increased from 3.3 Pf to 3.7 Pf and 4.5 Pf. 
     When the first switch S 1  is turned off and the second switch S 2  is turned on to select the second inductor L 2  and the adjustable capacitor C, a capacitance of the adjustable capacitor C can be gradually decreased from the second value, and the central frequency of the antenna  15  can be moved to a high-frequency range to obtain a third bandwidth. In this embodiment, the capacitance of the adjustable capacitor C is gradually decreased from 3.3 Pf to 2.9 Pf, 2.6 Pf, 2.35 Pf, and 2 Pf. 
       FIG. 3  illustrates a diagram showing a return loss measurement of the antenna assembly  100 . Curve  1  represents a working frequency of the antenna assembly  100  when the antenna assembly  100  has no matching unit  17 . Curve  2  represents a working frequency of the antenna assembly  100  when the antenna assembly  100  has the matching unit  17 . Curve  3  represents a working frequency of the antenna assembly  100  when the first inductor L 1  is selected and the capacitance of the adjustable capacitor C is adjusted to the first value, and the antenna assembly  100  has the first bandwidth BW M . Curve  4  represents a working frequency of the antenna assembly  100  when the second inductor L 2  is selected and the capacitance of the adjustable capacitor C is gradually increased from the second value, and the antenna assembly  100  has the second bandwidth BW L . Curve  5  represents a working frequency of the antenna assembly  100  when the second inductor L 2  is selected and the capacitance of the adjustable capacitor C is gradually decreased from the second value, and the antenna assembly  100  has the third bandwidth BW H . 
     As shown in  FIG. 3 , after the matching unit  17  is used in the antenna assembly  100 , the antenna assembly  100  can obtain the first bandwidth BW M , the second bandwidth BW L , or the third bandwidth BW H  by selecting the first inductor L 1  or the second inductor L 2  and adjusting a capacitance of the adjustable capacitor C, thereby broadening a bandwidth of the antenna assembly  100 . 
     In other embodiments, the first inductor L 1  can be replaced by a plurality of inductors that the sum of the inductances of the plurality of inductors is equal to the inductance of the first inductor L 1 . The second inductor L 2  can be replaced by a plurality of inductors that the sum of the inductances of the plurality of inductors is equal to the inductance of the second inductor L 2 . 
     The embodiments shown and described above are only examples. Therefore, many such details are neither shown nor described. Even though numerous characteristics and advantages of the present technology have been set forth in the foregoing description, together with details of the structure and function of the present disclosure, the disclosure is illustrative only, and changes may be made in the detail, especially in matters of shape, size and arrangement of the parts within the principles of the present disclosure up to, and including the full extent established by the broad general meaning of the terms used in the claims. It will therefore be appreciated that the embodiments described above may be modified within the scope of the claims.