Patent Publication Number: US-2010117920-A1

Title: Multiband antenna device

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a multiband antenna device and, more particularly, to a multiband antenna device using a switch to control a conducting state between two antennas to receive signals in different frequency bands. 
     2. Description of the Related Art 
     Conventional wireless devices have different kinds of wireless communication applications, such as a global system for mobile communications (GSM), wideband code division multiple access (W-CDMA), wireless fidelity (Wi-Fi), bluetooth, a global positioning system (GPS), digital video broadcasting (DVB) and so on. Therefore, if the above application techniques are integrated in a same communication device, the performance of each wireless communication application may be not well, or considering the performance, the size of the wireless device has to increase. Thus, the performance and the size can not be considered at the same time. 
     Considering multiband wireless communication applications, the antenna design of the conventional wireless devices is to design an antenna for a frequency band, which not only causes a complex circuit design, but also causes a large circuit area. Thus, the volume of the wireless device can not decrease easily. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention provides a multiband antenna device. The multiband antenna device utilizes a switch to control a conducting state between two antennas. Thus, different antennas can receive signals in different frequency bands, respectively, and the volume of a design circuit can be reduced. Furthermore, reflecting energy of the signals feeding in the antennas can be reduced by adjusting the impedance values of the antennas to make reception and transmission of the antennas achieve an optimized state. 
     In the invention, the multiband antenna device includes a first antenna, a second antenna, and a switch. The first antenna has a first terminal and a second terminal, and the first terminal is a feed-in point of signals. The second antenna has a first terminal and a second terminal, and the second terminal of the first antenna and the first terminal of the second antenna are connected by the switch. The switch is used to control a conducting state between the first antenna and the second antenna. 
     When the switch turns off, the first antenna is not conducted to the second antenna, which represents that the multiband antenna device may only receive and transmit the signals by the first antenna. At that moment, the wavelength of the signals received and transmitted by the multiband antenna device is equal to a length λ 1  of the first antenna. The receiving and transmitting frequency is a first frequency f 1  equal to f 1 =ν/λ 1 , and the ν is a velocity of electromagnetic waves. 
     When the switch turns on, the first antenna is conducted to the second antenna. It represents that multiband antenna device may receive and transmit the signals by both the first antenna and the second antenna. At that moment, the wavelength of the signals received and transmitted by the multiband antenna device is equal to the sum of the length λ 1  of the first antenna and a length λ 2  of the second antenna, that is, λ 1 +λ 2 . The receiving and transmitting frequency is a second frequency f 2  equal to f 2 =ν/(λ 1 +λ 2 ), and the ν is the velocity of the electromagnetic waves. 
     In the invention, the multiband antenna device utilizes a switch to control  5  the conducting state between the two antennas to receive signals in different frequency bands. With increase of the number of the antenna and the switch, the antenna device of the invention can receive signals in more frequency bands. 
     In the invention, the switch includes a controller and a diode. The diode is connected with the first antenna and the second antenna, respectively, and the controller is used to control the conducting state of the diode. The controller may be a programmable logic circuit (PLC), and a software program may be written into the controller to control the diode. 
     In the invention, the reflecting energy of the signals feeding in the antennas can be reduced by adjusting the impedance values of the antennas to make signal reception and transmission of the multiband antenna device achieve an optimized effect. 
     Compared with the conventional technology, the invention has the following advantages. 
     A single antenna device is used to receive multiband signals to reduce the volume of the antenna device. 
     The reflecting energy of feed-in signals can be reduced by adjusting the impedance values of the antennas to make the signal reception and transmission achieve an optimized effect. 
     These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a schematic diagram of a multiband antenna device according to a first embodiment of the invention; 
         FIG. 1B  is a schematic diagram of a multiband antenna device according to a second embodiment of the invention; and 
         FIG. 1C  is a schematic diagram of a multiband antenna device according to a third embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     As shown in  FIG. 1A ,  FIG. 1A  is a schematic diagram of a multiband antenna device according to a first embodiment of the invention. A multiband antenna device  1  includes a first antenna  11 , a second antenna  12 , and a first switch  14 . 
     The first antenna  11  has a first terminal  111  and a second terminal  112 , and the first terminal  111  is a feed-in point. The second antenna  12  also has a first terminal  121  and a second terminal  122 . The first switch  14  includes a first controller  141  and a first diode  142 . 
     In the first switch  14 , two terminals of the first diode  142  are connected with the second terminal  112  of the first antenna  11  and the first terminal  121  of the second antenna  12 , respectively, and the first controller  141  controls conduction of the first diode  142 . The first controller  141  may be a programmable logic circuit (PLC), and it may control via a software program. 
     The multiband antenna device  1  of the embodiment utilizes an on state and an off state of the first switch  14  to adjust a receiving and transmitting frequency band of the multiband antenna device  1 . In the multiband antenna device  1  of the embodiment, the transmitting velocity of electromagnetic waves is ν, the length of the first antenna  11  is λ 1 , and the length of the second antenna  12  is λ 2 . 
     When the first switch  14  turns off, the first antenna  11  is not conducted to the second antenna  12 . It represents that the multiband antenna device  1  can only receive and transmit signals by the first antenna  11 . At that moment, the wavelength of the signals received and transmitted by the multiband antenna device  1  is equal to the length λ 1  of the first antenna  11 . The receiving and transmitting frequency is a first frequency f 1  equal to f 1 =ν/λ 1 , and the ν is the velocity of the electromagnetic waves. 
     When the first switch  14  turns on, the first antenna  11  is conducted to the second antenna  12 . It represents that the multiband antenna device  1  can receive and transmit the signals by the first antenna  11  and the second antenna  12 . At that moment, the wavelength of the signals received and transmitted by the multiband antenna device  1  is equal to the sum of the length λ 1  of the first antenna  11  and the length λ 2  of the second antenna  12 , that is, λ 1 +λ 2 . The receiving and transmitting frequency is a second frequency f 2  equal to f 2 =ν/(λ 1 +λ 2 ), and the ν is the velocity of the electromagnetic waves. 
     In the embodiment, the first antenna  11  and the second antenna  12  are integrated in a same antenna device, and the on state and the off state of the first switch  14  are used to control the conducting state between the two antennas to receive signals in two different frequency bands. 
     In other embodiments, a plurality of antennas may also be integrated in a same antenna device in a serial mode, and a plurality of switches may be used to cooperate with the antennas to control the conduction of the antennas to receive signals in different frequency bands. 
     As shown in  FIG. 1B ,  FIG. 1B  is a schematic diagram of a multiband antenna device  1  according to a second embodiment of the invention. The multiband antenna device  1  includes a first antenna  11 , a second antenna  12 , a third antenna  15 , a first switch  14 , and a second switch  16 . The structures, the elements and the functions of the first antenna  11 , the second antenna  12 , and the first switch  14  are described as in the first embodiment. Therefore, they are not described for a concise purpose. The third antenna  15  and the second switch  16  are described herein. 
     The third antenna  15  has a first terminal  151  and a second terminal  152 . The second switch  16  includes a second controller  161  and a second diode  162 . 
     In the second controller  16 , two terminals of the second diode  162  are connected with the second terminal  122  of the second antenna  12  and the first terminal  151  of the third antenna  15 , respectively, and the second controller  161  controls the conduction of the second diode  162 . The second controller  161  may be a programmable logic circuit (PLC), and a software program may be loaded to perform a program control. 
     In the multiband antenna device  1  of the embodiment, the transmitting velocity of the electromagnetic waves is ν, the length of the first antenna  11  is λ 1 , the length of the second antenna  12  is λ 2 , and the length of the third antenna  15  is λ 3 . 
     When the first switch  14  turns off, the first antenna  11  is not conducted to the second antenna  12 . It represents that the multiband antenna device  1  can only receive and transmit signals by the first antenna  11 . At that moment, the wavelength of the signals received and transmitted by the multiband antenna device  1  is equal to the length λ 1  of the first antenna  11 . The receiving and transmitting frequency is a first frequency f 1  equal to f 1 =ν/λ 1 , and the ν is the velocity of electromagnetic waves. 
     When the first switch  14  turns on and the second switch  16  turns off, the second antenna  12  is not conducted to the third antenna  15 . It represents that the multiband antenna device  1  can receive and transmit the signals by the first antenna  11  and the second antenna  12 . At that moment, the wavelength of the signals received and transmitted by the multiband antenna device  1  is equal to the sum of the length of the first antenna  11  and the length of the second antenna  12 , that is, λ 1 +λ 2 . The receiving and transmitting frequency is a second frequency f 2  equal to f 2 =ν/(λ 1 +λ 2 ), and the ν is the velocity of the electromagnetic waves. 
     When the first switch  14  and the second switch  16  both turn on, the second antenna  12  is conducted to the first antenna  11  and the third antenna  15 , respectively. It represents that the multiband antenna device  1  can receive and transmit the signals by the first antenna  11 , the second antenna  12 , and the third antenna  15 . At that moment, the wavelength of the signals received and transmitted by the multiband antenna device  1  is equal to the sum of the length of the first antenna  11 , the length of the second antenna  12  and the length of the third antenna  15 , that is, λ 1 +λ 2 +λ 3 . The receiving and transmitting frequency is a third frequency f 3  equal to f 3 =ν/(λ 1 +λ 2 +λ 3 ), and the ν is the velocity of the electromagnetic waves. 
     In the embodiment, the first antenna  11 , the second antenna  12  and the third antenna  15  are integrated in a same antenna device, and the on state and the off state of the first switch  14  and the second switch  16  are used to control the conducting states of the three antennas to receive signals in three different frequency bands, respectively. 
     As shown in  FIG. 1C ,  FIG. 1C  is a schematic diagram of a multiband antenna device  1  according to a third embodiment of the invention. The multiband antenna device  1  includes a first antenna  11 , a second antenna  12 , a third antenna  15 , a first switch  14 , and a second switch  16 . 
     The structures, the elements and the functions of the first antenna  11 , the second antenna  12 , and the third antenna  15  are described as in the second embodiment. Therefore, they are not described for a concise purpose. The first switch  14  and the second switch  16  are described herein. 
     The first switch  14  includes a first controller  141   a  and a first diode  142 . The second switch  16  has a second diode  162 . 
     The second diode  162  of the second switch  16  is connected with the second terminal  122  of the second antenna  12  and the first terminal  151  of the third antenna  15 , and it is also connected with the first controller  141   a.  The first diode  142  of the first switch  14  is connected with the second terminal  112  of the first antenna  11  and the first terminal  121  of the second antenna  12 . The first controller  141  a can control the conduction of the first diode  142  and the second diode  162 , respectively. The first controller  141   a  may be a programmable logic circuit (PLC), and a software program may be loaded to control the conduction of the first diode  142  and the second diode  162 , respectively. 
     In the multiband antenna device  1  of the embodiment, the velocity of the electromagnetic waves is ν, the length of the first antenna  11  is λ 1 , the length of the second antenna  12  is λ 2 , and the length of the third antenna  15  is λ 3 . 
     When the first switch  14  controls the first diode  142  to turn off, the first antenna  11  is not conducted to the second antenna  12 . It represents that the multiband antenna device can only receive and transmit signals by the first antenna  11 . At that moment, the wavelength of the signals received and transmitted by the multiband antenna device  1  is equal to the length λ 1  of the first antenna  11 . The receiving and transmitting frequency is a first frequency f 1  equal to f 1 =ν/λ 1 , and the ν is the velocity of the electromagnetic waves. 
     When the first switch  14  controls the first diode  142  to turn on and controls the second diode  162  to turn off, the second antenna  12  is not conducted to the third antenna  15 . It represents that the multiband antenna device can only receive and transmit the signals by the first antenna  11  and the second antenna  12 . At that moment, the wavelength of the signals received and transmitted by the multiband antenna device  1  is equal to the sum of the length of the first antenna  11  and the second antenna  12 , that is, λ 1 +λ 2 . The receiving and transmitting frequency is a second frequency f 2  equal to f 2 =ν/(λ 1 +λ 2 ), and the ν is the velocity of the electromagnetic waves. 
     When the first switch  14  controls the first diode  142  and the second diode  162  to turn on, the second antenna  12  is conducted to the first antenna  11  and the third antenna  15 , respectively. It represents that the multiband antenna device  1  can receive and transmit the signals by the first antenna  11 , the second antenna  12 , and the third antenna  15 . At that moment, the wavelength of the signals received and transmitted by the multiband antenna device  1  is equal to the sum of the lengths of the first antenna  11 , the second antenna  12  and the third antenna  15 , that is, λ 1 +λ 2 +λ 3 . The receiving and transmitting frequency is a third frequency f 3  equal to f 3 =ν/(λ 1 +λ 2 +λ 3 ), and the ν is the velocity of the electromagnetic waves. 
     In the embodiment, the first antenna  11 , the second antenna  12  and the third antenna  15  are integrated in a same antenna device, and the on state and the off state of the first switch  14  and the second switch  16  are used to control the conduction of the three antennas to receive signals in three different frequency bands, respectively. Furthermore, in the embodiment, the first controller is used to control two diodes, respectively. Compared with the second embodiment, in the embodiment, a controller is omitted. 
     As shown in  FIG. 1C , the impedance values of the antennas of the multiband antenna device  1  can be adjusted by adjusting the lengths, the widths or the materials of the antennas. The adjustment of the impedance values is used to increase the feed-in energy of the signals and to decrease the reflecting energy to achieve an optimized receiving and transmitting effect of the multiband antenna device. Thus, the receiving and transmitting performance of the multiband antenna device  1  can achieve an optimization. 
     Therefore, in the invention, a single antenna device can provide multiband signals, and the volume of the design circuit can be reduced at the same time. In addition, in the invention, the impedance values of the antennas can be adjusted to make the multiband antenna device achieve the optimized single receiving and transmitting performance. Thus, the feed-in signals can increase, and the reflecting energy can decrease. 
     Although the present invention has been described in considerable detail with reference to certain preferred embodiments thereof, the disclosure is not for limiting the scope of the invention. Persons having ordinary skill in the art may make various modifications and changes without departing from the scope and spirit of the invention. Therefore, the scope of the appended claims should not be limited to the description of the preferred embodiments described above.