Patent Publication Number: US-9905912-B2

Title: Antenna module

Description:
RELATED APPLICATIONS 
     This application claims priority to Taiwan Application Serial Number 104140521, filed Dec. 3, 2015, which is herein incorporated by reference. 
     BACKGROUND 
     Technical Field 
     The present invention relates to an antenna technology. More particularly, the present invention relates to a multi-frequency antenna module. 
     Description of Related Art 
     Recently, as wireless communication technology develops, electronic products in the market, such as notebooks, tablet computers, etc., transmit information by widely using the wireless communication technology. 
     However, as communication requirements increase, if an antenna in an electronic product is desired to be designed as a multi-frequency antenna, the antenna is likely to have a bandwidth deficiency problem at a low frequency and is hardly to cover the LTE 700 frequency band. 
     Therefore, those skilled in the art have been endeavoring to solve the bandwidth deficiency problem of the multi-frequency antenna at the low frequency. 
     SUMMARY 
     In order to improve a bandwidth of a multi-frequency antenna at a low frequency, the present disclosure provides an antenna module that includes a parasitic unit and a first antenna unit. The parasitic unit includes a parasitic radiation portion and a second parasitic radiation portion. The second parasitic radiation portion is electrically connected to the first parasitic radiation portion. The first parasitic radiation portion and the second parasitic radiation portion surround a central area of the parasitic unit. The first antenna unit includes a feeding terminal, a ground terminal and a first radiation portion. The ground terminal is electrically connected to a ground portion. The feeding terminal is configured to transmit and receive a first antenna signal. The first radiation portion is configured to collaborate with the parasitic unit to generate a first resonant mode of the antenna module. The first resonant mode includes a central frequency, a frequency twice of the central frequency and a frequency three times of the central frequency. 
     In sum, the present disclosure can generate the resonant modes to cover many types of frequency bands by a double open-loop structure formed by the antenna unit and the parasitic unit, and have broadband characteristic. Moreover, the antenna module of the present disclosure is applicable to the multi-input multi-output (MIMO) system with good isolation. 
     It is to be understood that both the foregoing general description and the following detailed description are by examples, and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be more fully understood by reading the following detailed description of the embodiment, with reference made to the accompanying drawings as follows: 
         FIG. 1  is a schematic diagram of an antenna module according to an embodiment of the present disclosure; 
         FIG. 2A  is a schematic diagram of a parasitic unit of an antenna module according to an embodiment of the present disclosure; 
         FIG. 2B  is a schematic diagram of an antenna unit of an antenna module according to an embodiment of the present disclosure; 
         FIG. 3  is a schematic diagram of an antenna module according to an embodiment of the present disclosure; 
         FIG. 4A  is a schematic diagram showing a relationship between voltage standing wave ratio (VSWR) and frequency of an antenna module according to an embodiment of the present disclosure; 
         FIG. 4B  is a schematic diagram showing a relationship between antenna gain and frequency of an antenna module according to an embodiment of the present disclosure; 
         FIG. 5  is a schematic diagram of an antenna module applied to a multi-input multi-output (MIMO) system according to an embodiment of the present disclosure; 
         FIG. 6  is a schematic diagram showing a relationship between isolation and frequency of an antenna module applied to a MIMO system according to an embodiment of the present disclosure; and 
         FIG. 7  is a schematic diagram of an antenna module according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the present embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” or “includes” and/or “including” or “has” and/or “having” when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof. 
     In this document, the term “coupled” may also be termed as “electrically coupled,” and the term “connected” may be termed as “electrically connected.” “Coupled” and “connected” may also be used to indicate that two or more elements cooperate or interact with each other. 
     Unless otherwise indicated, all numbers expressing quantities, conditions, and the like in the instant disclosure and claims are to be understood as modified in all instances by the term “about.” The term “about” refers, for example, to numerical values covering a range of plus or minus 20% of the numerical value. The term “about” preferably refers to numerical values covering range of plus or minus 10% (or most preferably, 5%) of the numerical value. The modifier “about” used in combination with a quantity is inclusive of the stated value. 
     Reference is made to  FIG. 1 .  FIG. 1  is a schematic diagram of an antenna module  100  according to an embodiment of the present disclosure. As shown in  FIG. 1 , the antenna module  100  includes a parasitic unit  110  and an antenna unit  120 . The parasitic unit  110  and the antenna unit  120  form a double open-loop structure. 
     In order to describe the parasitic unit  110 , reference is made to  FIG. 2A . The parasitic unit  110  includes a first parasitic radiation portion  112  and a second parasitic radiation portion  114 , in which the first parasitic radiation portion  112  is electrically connected to the second parasitic radiation portion  114 . An area surrounded by the first parasitic radiation portion  112  and the second parasitic radiation portion  114  is a central area  116  of the first parasitic unit  112 . 
     In order to describe the antenna unit  120 , reference is made to  FIG. 2B . The antenna unit  120  includes a feeding terminal  121 , a ground terminal  122 , a first radiation portion  123  and a connecting portion  127 . The antenna unit  120  may be divided into a connecting portion  127  and a main body. The connecting portion  127  is disposed on a second surface of a substrate (e.g., a printed circuit board (PCB)), and is electrically connected to the main body on a first surface of the substrate. The feeding terminal  121  is configured to transmit and receive a first antenna signal. The ground terminal  122  is electrically connected to a ground portion  140 . The ground portion  140  may be electrically connected to a ground of a system to which the antenna module  100  is applied, and the size of the ground portion  140  is determined in accordance with the system. In an embodiment, the first radiation portion  123  includes a first protruding portion  126 . The first protruding portion  126  is disposed in the central area  116  of the parasitic unit  110 , a slot G 1  is disposed between the first parasitic radiation portion  112  and the first protruding portion  126 , and a slot G 2  is disposed between the second parasitic radiation portion  114  and the first protruding portion  126  (as shown in  FIG. 1 ). 
     The first radiation portion  123  forms a monopole antenna, and is configured to collaborate with the parasitic unit  110  to generate a first resonant mode of the antenna module  100 . Specifically, the parasitic unit  110  is electrically connected to the ground of the system to which the antenna module  100  is applied by a terminal T 1 . A positive terminal of a signal transmission line  130  is electrically coupled to the feeding terminal  121 , and a negative terminal signal of the transmission line  130  is electrically coupled to the ground terminal  122 . A signal is sent to the feeding terminal  121  through the positive terminal of the signal transmission line  130 , passes through the first radiation portion  123 , and is coupled with the parasitic unit  110  (including the first parasitic radiation portion  112  and the second parasitic radiation portion  114 ) through the slot G 1  and the slot G 2 , so as to generate the first resonant mode. Frequency bands covered by the first resonant mode include a central frequency, a frequency twice of the central frequency and a frequency three times of the central frequency. In an embodiment, the central frequency is about 704-906 MHz, the frequency twice of the central frequency is about 1700 MHz, and the frequency three times of the central frequency is about 2400 MHz. As shown in  FIG. 4A , a frequency band  4111  stands for 704-906 MHz, a frequency band  4112  stands for 1700 MHz, and a frequency band  4113  stands for 2400 MHz. The antenna module  100  can achieve only one resonant mode at a low frequency, i.e., the first resonant mode. Moreover, a user can adjust an impedance bandwidth of the antenna module  100  at the first resonant mode by designing a length and/or a width of a portion  1261  (included in the first protruding portion  126 ). 
     In an embodiment, a bandwidth of the frequency twice of the central frequency at the first resonant mode is about 1425 MHz-2170 MHz, which includes 1.5 GHz long term evolution (LTE) B11 and B21 frequency bands. A bandwidth of the frequency three times of the central frequency at the first resonant mode is about 2500 MHz-2700 MHz, which includes the LTE B7 frequency band. 
     In practice, the connecting portion  127  of the antenna unit  120  disposed on the second surface of the substrate may be electrically connected to the main body disposed on the first surface of the substrate through a via. As shown in  FIG. 1 , a projection area of the connecting portion  27  projected on the first surface of the substrate overlaps with a portion of the first parasitic radiation portion  112 . Due to isolation by thickness (e.g., 4 mm) of the substrate, the connecting portion  127  is electrically isolated from the parasitic unit  110 . The signal transmission line  130  may be a coaxial transmission line (e.g., a 50 ohm coaxial transmission line). However, the present disclosure is not limited thereto. 
     In an embodiment, the antenna module  100  is applicable to a mobile electronic device. For example, the electronic device may be a notebook, a cell phone, a tablet computer, a game machine, a translation machine, or any electronic device. However, the present disclosure is not limited thereto. The size of the antenna module  100  may be designed to a length of 75 mm, a width of 12 mm or 10 mm, and a thickness of 0.4 mm. 
     As a result, the antenna module  100  of the present disclosure can generate resonant modes that cover multi-frequencies through the design of the antenna unit  120  and the parasitic unit  110 , and have broadband characteristic. Moreover, compared to the prior art, the antenna module  100  of the present disclosure does not need to set up an extending antenna path along a perpendicular (e.g., Z axis) direction, thus reducing antenna volume, further reducing the volume of the electronic device to which the antenna module  100  is applied. 
     In an embodiment, as shown in  FIGS. 1 and 2B , the antenna unit  120  further includes a second radiation portion  124  and a second protruding portion  128 . The second radiation portion  124  is electrically connected to the feeding terminal  121  and forms a monopole antenna. The second protruding portion  128  is electrically connected to the second radiation portion  124 . A slot G 3  is disposed between the second protruding portion  128  and the first parasitic radiation portion  112 . 
     The second protruding portion  128  is configured to collaborate with the parasitic unit  110  to generate a second resonant mode of the antenna module  100 . Specifically, a signal is sent to the feeding terminal  121  through the positive terminal of the signal transmission line  130 , passes through the second radiation portion  124  and the second protruding portion  128 , and is coupled with the parasitic unit  110  (including the first and second parasitic radiation portions  112  and  114 ) through the slot G 3 , so as to generate the second resonant mode. In an embodiment, a frequency band covered by the second resonant mode is about 1400 MHz, as shown by a frequency band  412  in  FIG. 4A . Moreover, the user can adjust an impedance bandwidth of the second resonant mode by designing lengths and/or widths of the second protruding portion  128  and a portion  1121  (included in the first parasitic radiation portion  112 ). 
     In an embodiment, as shown in  FIGS. 1 and 2B , the slot G 4  is disposed in the second radiation portion  124 . The second radiation portion  124  is configured to generate a third resonant mode of the antenna module  100 . In an embodiment, a frequency band covered by the third resonant mode is about 2050 MHz, as shown by a frequency band  413  in  FIG. 4A . Moreover, the user can adjust an impedance bandwidth of the third resonant mode by designing a length and/or a width of the slot G 4 . 
     In an embodiment, as shown in  FIGS. 1 and 2B , the second radiation portion  124  includes a third protruding portion  125  that is electrically connected to the feeding terminal  121 . A slot G 5  is disposed in the third protruding portion  125 . The third protruding portion  125  is configured to generate a fourth resonant mode of the antenna module  100 . In an embodiment, a frequency band covered by the fourth resonant mode is about 2200 MHz, as shown by a frequency band  414  in  FIG. 4A . Moreover, the user can adjust an impedance bandwidth of the fourth resonant mode by designing a length and/or a width of the slot G 5 . 
     In an embodiment, as shown in  FIGS. 1 and 2B , a slot G 6  is disposed in the third protruding portion  125 . The third protruding portion  125  is configured to generate a fifth resonant mode of the antenna module  100 . In an embodiment, a frequency band covered by the fifth resonant mode is about 2600 MHz, as shown by a frequency band  415  in  FIG. 4A . Moreover, the user can adjust en impedance bandwidth of the fifth resonant mode by designing a length and/or a width of the slot G 6 . 
     For example, in the embodiment shown in  FIG. 1 , the frequency bands of the first resonant mode to the fifth resonant mode generated by the antenna module  100  cover the LTE 700 frequency band, the global system for mobile communications (GSM) 850 frequency band, the extended GSM 900 frequency band, the LTE 1500 frequency band, the digital cellular system (DCS) 1800 frequency band, the PCS 1900 frequency band, the universal mobile telecommunications system (UMTS) 2100 frequency band and the LTE 2500 frequency band. In other words, the antenna module  100  of the present disclosure covers many different types of frequency bands, and the user can adjust impedance bandwidths of the first resonant mode to the fifth resonant mode by designing lengths and/or widths of the slots G 1 -G 6 . 
     In another embodiment, the aforementioned parasitic unit may be designed as different shapes, and the relative position to the antenna unit may be changed according to actual requirements. Reference is made to  FIG. 3 . An antenna module  300  is approximately the same as the antenna module  100 , and the following description only focuses on the differences therebetween. 
     The antenna module  300  includes a parasitic unit  310  and an antenna unit  120 . The parasitic unit  310  includes a first parasitic radiation portion  312  and a second parasitic radiation portion  314 . The first parasitic radiation portion  312  is electrically connected to the second parasitic radiation portion  314 . An area surrounded by the first parasitic radiation portion  312  and second parasitic radiation portion  314  is a central area  316 . A first protruding portion  326  of the first radiation portion  123  is adjacent to the second parasitic radiation portion  314 , and a slot G 7  is disposed between the second parasitic radiation portion  314  and the first protruding portion  326 . 
     Similarly, a signal is sent to the feeding terminal  121  through the positive terminal of the signal transmission line  130 , passes through the first radiation portion  123 , and is coupled with the parasitic unit  310  (including the first parasitic radiation portion  312  and the second parasitic radiation portion  314 ) through the slot G 1 , so as to generate a first resonant mode. Description about a second resonant mode to a fifth resonant mode of the antenna module  300  is similar to the above description, and are not repeated herein. The size of the antenna module  100  may be designed to a length of 75 mm, a width of 12 mm, and a thickness of 0.4 mm. 
     Reference is made to  FIGS. 4A and 4B .  FIG. 4A  is a schematic diagram showing a relationship between voltage standing wave ratio (VSWR) and frequency of an antenna module according to an embodiment of the present disclosure. As shown in  FIG. 4A , a horizontal axis indicates frequency, and a longitudinal axis indicates VSWR, in which frequency F 1  is about 704 MHz, frequency F 2  is about 960 MHz, frequency F 3  is about 1425 MHz, frequency F 4  is about 1710 MHz, frequency F 5  is about 2170 MHz, frequency F 6  is about 2500 MHz, and frequency F 7  is about 2700 MHz.  FIG. 4B  is a schematic diagram showing a relationship between antenna gain (unit: dB) and frequency of an antenna module according to an embodiment of the present disclosure. Curves  410  and  440  stand for the antenna module  100  with length of 75 mm, width of 12 mm and thickness of 0.4 mm. Curves  420  and  450  stand for the antenna module  300  with length of 75 mm, width of 12 mm, and thickness of 0.4 mm. Curves  430  and  460  stand for the antenna module  100  with length of 75 mm, width of 10 mm, and thickness of 0.4 mm. As shown in  FIG. 4B , the antenna gain of the curve  460  is slightly smaller than the antenna gain of the curves  440  and  450  in a low frequency ranging 894 MHz-960 MHz, but other frequency bands have good antenna gains. 
     In an embodiment, the antenna modules  100  and  300  may be applicable to a multi-input multi-output (MIMO) communication system, and is disposed in a mobile electronic device. For example, the antenna module may be disposed in a tablet computer. As shown in  FIG. 5 , a first antenna module  510 , a second antenna module  520 , a third antenna module  531  and a fourth antenna module  532  may commonly share a ground  540  of the system. In a mobile electronic device with two antenna modules, the antenna modules may be placed at the positions of the first antenna module  510  and the second antenna module  520  those of the first antenna module  510  and third antenna module  531 , or those of first antenna module  510  and the fourth antenna module  532 . In a situation that the antenna modules at the first antenna module  510  and the third antenna module  531  and a situation that the antenna modules at the first antenna module  510  and the fourth antenna module  532 , the first antenna module  510  is spaced from the third antenna module  531  (or the fourth antenna module  532 ) at least at a distance d 1  (e.g., 75 mm). In an embodiment, an electronic device with size of more than 12 inches uses an arrangement of the first antenna module  510  and the second antenna module  520 , and an electronic device with size of less than 12 inches uses an arrangement of the first antenna module  510  and the third antenna module  531  (or an arrangement of the first antenna module  510  and the fourth antenna module  532 ). However the present disclosure is not limited thereto. 
     Reference is made to  FIG. 6 .  FIG. 6  is a schematic diagram showing a relationship between isolation and frequency of an antenna module applied to a MIMO system according to an embodiment of the present disclosure. As shown in  FIG. 6 , a horizontal axis indicates frequency, a longitudinal axis indicates isolation (unit: dB), in which frequency F 1  is about 704 MHz, frequency F 2  is about 960 MHz, frequency F 3  is about 1425 MHz, frequency F 4  is about 1710 MHz, frequency F 5  is about 2170 MHz, frequency F 6  is about   2500 MHz and frequency F 7  is about 2700 MHz. A curve  61  stands for the first antenna module  510  and the second antenna module  520 , a curve  620  stands for the first antenna module  510  and the third antenna module  531 , and a curve  630  stands for the first antenna module  510  and the fourth antenna module  532 . From  FIG. 6 , curves  610 - 630  can achieve an isolation effect that is less than 13 dB, and an envelope correlation coefficient (ECC) are less than 0.3, and therefore the interference between the antenna modules of the present disclosure is reduced. 
     In another embodiment, as shown in  FIG. 7 , an antenna module  700  is applied to a notebook, and the size of the antenna module  700  is designed to a length of 106 mm, a width of 16 mm and a thickness of 2.8 mm. The antenna module  700  includes a parasitic unit  710 , an antenna unit  720  and an antenna unit  730 . The parasitic unit  710  and the antenna unit  720  are respectively similar to the aforementioned parasitic units  110  and  310  and the antenna unit  120 , and thus are not described again herein. A main body of the antenna unit  730  is spaced from a main body of the antenna unit  720  at least at a distance d 2  (e.g., 13 mm), and the main body of the antenna unit  730  and the main body of the antenna unit  720  commonly share a ground portion  740 . 
     A ground terminal  732  of the antenna unit  730  is electrically connected to the ground portion  740 , and a feeding terminal  731  of the antenna unit  730  is configured to transmit and receive a second antenna signal. In an embodiment, the antenna unit  730  is configured to generate a sixth resonant mode that covers the wireless fidelity (Wi-Fi) frequency band. As a result, different antenna units may be integrated into the antenna module  700  of the present disclosure antenna to further reduce the antenna volume in the electronic device, and then to reduce the volume of the electronic device. 
     Through the above embodiments, the present disclosure can generate the resonant modes to cover many types of frequency bands by the double open-loop structure formed by the antenna unit and the parasitic unit, and have broadband characteristic. Moreover, the antenna module of the present disclosure can be applied to the MIMO system with good isolation. 
     Although the present invention has been described in considerable detail with reference to certain embodiments thereof, other embodiments are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims.