Patent Publication Number: US-8994596-B2

Title: Multi-band antenna

Description:
This application claims the benefit of Taiwan application Serial No. 100127804, filed Aug. 4, 2011, the subject matter of which is incorporated herein by reference. 
     BACKGROUND PLANE 
     1. Technical 
     The application relates in general to a multi-band inverted-F antenna. 
     2. Description of the Related Art 
     To satisfy mobility requirement, wireless communication products are directed towards miniaturization and lightweight. The interior of a wireless communication device has limited space available for antenna. For a hidden antenna, antenna size and function have much to do with the consumer&#39;s acceptance of the product. 
     Inverted-F antenna is a popular hidden antenna, which can be hidden in a mobile phone, a personal digital assistant (PDA), or a notebook computer. Conventional inverted-F antenna mainly includes: a main radiation part, a signal feeding circuit and a short-circuit line connected to ground plane. However, conventional inverted-F antenna still has many issues to resolve, for example narrow bandwidth, and complicated and easily-deformed structure. 
     SUMMARY OF THE APPLICATION 
     The application is directed to an inverted-F antenna with a miniaturized structure. Dual oscillation frequencies are achieved by two main radiation parts. Via coupling effect of a slot, and a metal radiation part extended from ground plane, a third resonance band is formed. 
     According to an exemplary embodiment of the present application, a multi-band inverted-F antenna including a ground plane, a signal feeding circuit, a first main radiation part, a second main radiation part, and a third main radiation part is provided. The signal feeding circuit, electrically isolated from the ground plane, receives/transmits wireless signals. The first main radiation part, physically and electrically connected to the signal feeding circuit, generates a first band operation mode for the inverted-F antenna. The second main radiation part, physically and electrically connected to the signal feeding circuit, generates a second band operation mode for the inverted-F antenna. The third main radiation part is extended from the ground plane and is electrically isolated from the signal feeding circuit, the first main radiation part and the second main radiation part. The third main radiation part generates a third band operation mode for the inverted-F antenna via a signal coupling between the first and the third main radiation parts and/or a signal coupling between the second and the third main radiation parts. 
     The above and other contents of the application will become better understood with regard to the following detailed description of the preferred but non-limiting embodiment (s). The following description is made with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1 and 2  respectively show a plan view and a stereoscopic view of an inverted-F antenna according to an embodiment of the application; 
         FIGS. 3A and 3B  respectively show a front view and a top view of an inverted-F antenna according to another embodiment of the application; 
         FIGS. 4A and 4B  respectively show a left side view and a right side view of the inverted-F antenna in  FIGS. 3A and 3B ; 
         FIGS. 5A and 5B  respectively show stereoscopic views of the inverted-F antenna in  FIGS. 3A and 3B ; 
         FIG. 6  shows a VSWR experiment diagram of the inverted-F antenna according to the above two embodiments of the application; 
         FIGS. 7A˜7D ,  FIGS. 8A˜8D  and  FIGS. 9A˜9D  show radiation patterns of total gain polarization (horizontal polarization and vertical polarization) of the inverted-F antennas according to the above two embodiments of the application. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS OF THE APPLICATION 
     In embodiments of the application, dual oscillation frequencies are achieved by two main radiation parts. Via coupling effect of a slot, and a metal radiation part extended from ground plane, a third resonance band is formed and bandwidth is thus increased. 
     Referring to  FIGS. 1 and 2 , a plan view and a stereoscopic view of an inverted-F antenna according to an embodiment of the application are respectively shown. As indicated in  FIGS. 1 and 2 , an inverted-F antenna  10  of the embodiment of the application includes main radiation parts  11 ˜ 13 , a low-band impedance match  14 , a slot  15 , a short-circuit line  16 , a ground plane  17  and a signal feeding circuit  18 . 
     The inverted-F antenna  10  of the embodiment of the application in  FIG. 1  includes two printed circuit boards (PCB)  10 A and  10 B. The main radiation parts  11 ˜ 13 , the low-band impedance match  14  and the short-circuit line  16  are on the PCB  10 A. The slot  15 , the ground plane  17  and the signal feeding circuit  18  are on the PCB  10 B. 
     As indicated in  FIG. 2 , the PCB  10 A is vertically inserted into the PCB  10 B. That is, after assembly, the PCB  10 A and the PCB  10 B form an L-shaped structure. Thus, overall height of the inverted-F antenna  10  is reduced without affecting its radiation efficiency. 
     The main radiation part  11  is as a main radiation part for a first band of the inverted-F antenna  10 . The main radiation part  11  is for generating a first frequency band operation mode. The first frequency band is normally a low-frequency band, exemplarily but not restrictively, between 824 MHz˜960 MHz. The first frequency band may be adjusted through adjustment in the dimension of the main radiation part  11 . The main radiation part  11  is physically and electrically connected to the signal feeding circuit  18  for receiving/transmitting wireless signals. In the present embodiment of the application, the main radiation part  11  has a meander extended towards the signal feeding circuit  18 , and the size of the main radiation part  11  is effectively reduced. 
     The main radiation part  12  is used as a main radiation part for a second frequency band of the inverted-F antenna  10 . The second frequency band is normally a medium frequency band, exemplarily but not restrictively, between 1710 MHz˜18xx MHz. In the present embodiment of the application, the main radiation part  12  is adjacent to the meander of the main radiation part  11 . The main radiation part  12  generates a second frequency band operation mode for the inverted-F antenna. The second frequency band may be adjusted through adjustment in the dimension of the main radiation part  12 . The main radiation part  12  is physically and electrically connected to the signal feeding circuit  18  for receiving/transmitting wireless signals. 
     The main radiation part  13  is as a main radiation part for a third frequency band of the inverted-F antenna  10 . The third frequency band is normally a high-frequency band, exemplarily but not restrictively, between 18xx MHz˜2170 MHz. The main radiation part  13  generates a third frequency band operation mode for the inverted-F antenna. The third frequency band may be adjusted through adjustment in the dimension of the main radiation part  13 . The main radiation part  13  is extended from the ground plane  17  and adjacent to the main radiation part  11  and the main radiation part  12 . The main radiation part  13  is electrically isolated from the signal feeding circuit  18 , the main radiation part  11  and the second main radiation part  12 . However, via signal coupling paths P 1  and P 2 , the main radiation part  13  may be used as a high-frequency band main radiation part of the inverted-F antenna  10 . The signal coupling path P 1  is formed between the main radiation part  11  and the main radiation part  13 , for signal coupling between the main radiation part  11  and the main radiation part  13 . The signal coupling path P 2  is formed between the main radiation part  12  and the main radiation part  13  for signal coupling between the main radiation part  12  and the main radiation part  13 . In other words, a slot is formed between the main radiation part  11  and the main radiation part  13 , and another slot is formed between the main radiation part  12  and the main radiation part  13 . The third frequency band may be adjusted through adjustment in the dimension of the main radiation part  13 . Via the main radiation part  13 , the bandwidth of the inverted-F antenna  10  of the embodiment of the application is increased. 
     The low-frequency band impedance match  14  is extended from the main radiation part  11  and is used for impedance match. In the present embodiment of the application, the low-frequency band impedance match  14  is optional and is extended away from the meander of the main radiation part  11 . 
     The slot  15 , formed on the PCB  10 B, is formed between the main radiation part  13 , the ground plane  17  and the signal feeding circuit  18 . The slot  15  is for high-frequency impedance match. 
     The short-circuit line  16  is used as short-circuit of the inverted-F antenna  10  and also used for adjusting impedance match. In the present embodiment of the application, the short-circuit line  16  is electrically connected to the meander of the main radiation part  11 , which is adjacent to the short-circuit line  16 . 
     The ground plane  17  is used as a ground plane for the inverted-F antenna  10 . The inverted-F antenna  10  is electrically connected to the ground plane  17  through the short-circuit line  16 . The signal feeding circuit  18  feeds wireless signals to the main radiation parts  11  and  12 , and receives wireless signals received by the main radiation parts  11  and  12 . 
     The inverted-F antenna of the embodiment of the application includes printed circuit boards, so the inverted-F antenna has a robust structure and does not deform easily. For compatible with a lot of wireless systems, the inverted-F antenna of the embodiment of the application may adjust its oscillation frequency to achieve a suitable frequency bandwidth. 
     Besides, the dimension of the inverted-F antenna of the embodiment of the application may be reduced to be about 0.16 λ. 
     Referring to  FIGS. 3A and 3B , a front view and a top view of an inverted-F antenna  20  according to another embodiment of the application are respectively shown. As indicated in  FIGS. 3A and 3B , the inverted-F antenna  20  of the application includes: main radiation parts  21 ˜ 23 , low-frequency band impedance match  24 , a slot  25 , a short-circuit line  26 , a ground plane  27 , a signal feeding circuit  28  and a pin  29 . In  FIGS. 3A and 3B , slashed regions denote hollowed regions. 
     Operations and functions of the main radiation parts  21 ˜ 23 , the low-frequency band impedance match  24 , the slot  25 , the short-circuit line  26 , the ground plane  27  and the signal feeding circuit  28  of the inverted-F antenna  20  are the same or similar with that of the inverted-F antenna  10 , and the details are not repeated here. To improve impedance match, the main radiation part  23  further includes an impedance match  23 A. The impedance match  23 A is extended from the main radiation part  23  and is for impedance matching for the third band. Via the pin  29 , the inverted-F antenna  20  of the application may be inserted into circuit board (not illustrated) of wireless communication devices. 
     A part or a totality of the inverted-F antenna  20  of the application may be formed by metal pieces (for example iron pieces) to reduce cost. For example, the main radiation parts  21 ˜ 23 , the impedance match  23 A, the low-band impedance match  24 , the short-circuit line  26  and the pin  29  are on an iron piece, while the slot  25 , the ground plane  27  and the signal feeding circuit  28  are on another iron piece. The two iron pieces may form an L shape. 
       FIGS. 4A and 4B  respectively show a left side view and a right side view of the inverted-F antenna  20  of the application.  FIGS. 5A and 5B  respectively show two stereoscopic views of the inverted-F antenna  20 . As indicated in  FIGS. 4A ,  4 B,  5 A and  5 B, the appearance of the inverted-F antenna  20  of the application is L-shaped, so that the overall height of the L inverted-F antenna  20  is reduced without affecting its radiation efficiency. 
     To compatible with different wireless communication systems, the inverted-F antenna  20  of the application may adjust its oscillation frequency for a suitable bandwidth. 
       FIG. 6  shows a voltage standing wave ratio (VSWR) experiment diagram of the inverted-F antenna according the above two embodiments of the application. Compared with a reference line (VSWR=3), the inverted-F antenna of the two embodiments of the application may effectively support bands between 824 MHz˜960 MHz, between 1700 MHz˜18XX MHz and between 18XX MHz˜2170 MHz. As indicated in  FIG. 6 , the inverted-F antenna of the embodiments of the application is almost an excellent multi-band antenna. 
     Referring to  FIGS. 7A˜7D , gain polarization radiation patterns on the XY plane of the inverted-F antenna according to the embodiments of the application are shown.  FIGS. 7A˜7D  respectively show radiation patterns of total gain polarization of the inverted-F antenna operated at 824 MHz, 960 MHz, 1710 MHz and 2170 MH. 
     Referring to  FIGS. 8A˜8D , gain polarization radiation patterns on the XZ plane of the inverted-F antenna according to the embodiments of the application are shown.  FIGS. 8A˜8D  respectively show gain polarization radiation patterns of the inverted-F antenna operated at 824 MHz, 960 MHz, 1710 MHz and 2170 MHz. 
     Referring to  FIGS. 9A˜9D , gain polarization radiation patterns on the YZ plane of the inverted-F antenna according to the embodiments of the application are shown.  FIGS. 9A˜9D  respectively show gain polarization radiation patterns of the inverted-F antenna operated at 824 MHz, 960 MHz, 1710 MHz and 2170 MHz. 
     As indicated in  FIGS. 7A˜9D , the inverted-F antenna of the embodiments of the application have excellent gain polarization radiation patterns, which indicate excellent radiation efficiency. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed embodiments. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalents.