Patent Publication Number: US-11038254-B2

Title: Mobile device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority of Taiwan Patent Application No. 108127855 filed on Aug. 6, 2019, the entirety of which is incorporated by reference herein. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The disclosure generally relates to a mobile device, and more particularly, it relates to a mobile device and an antenna structure therein. 
     Description of the Related Art 
     With the advancements being made in mobile communication technology, mobile devices such as portable computers, mobile phones, multimedia players, and other hybrid functional portable electronic devices have become more common. To satisfy user demand, mobile devices can usually perform wireless communication functions. Some devices cover a large wireless communication area; these include mobile phones using 2G, 3G, and LTE (Long Term Evolution) systems and using frequency bands of 700 MHz, 850 MHz, 900 MHz, 1800 MHz, 1900 MHz, 2100 MHz, 2300 MHz, 2500 MHz, and 2700 MHz. Some devices cover a small wireless communication area; these include mobile phones using Wi-Fi and Bluetooth systems and using frequency bands of 2.4 GHz, 5.2 GHz, and 5.8 GHz. 
     Antennas are indispensable elements for wireless communication. If an antenna for signal reception and transmission has insufficient bandwidth, it will degrade the communication quality of the relative mobile device. Accordingly, it has become a critical challenge for antenna designers to design a wideband antenna element that is small in size. 
     BRIEF SUMMARY OF THE INVENTION 
     In an exemplary embodiment, the disclosure is directed to a mobile device which includes a common ground element, a connection element, a first radiation element, a second radiation element, a third radiation element, a fourth radiation element, and a dielectric substrate. The common ground element is coupled to a ground voltage. The first radiation element has a first feeding point. The first radiation element is coupled through the connection element to the common ground element. The second radiation element is coupled to the first feeding point. The second radiation element is at least partially surrounded by the first radiation element. The third radiation element has a second feeding point. The fourth radiation element is disposed adjacent to the third radiation element. The fourth radiation element is coupled to the common ground element. An antenna structure is formed by the common ground element, the connection element, the first radiation element, the second radiation element, the third radiation element, and the fourth radiation element. The antenna structure is disposed on the dielectric substrate. 
     In some embodiments, the common ground element substantially has a straight-line shape. 
     In some embodiments, the common ground element has a first side and a second side which are opposite to each other. The connection element, the first radiation element, and the second radiation element are disposed adjacent to the first side of the common ground element. The third radiation element and the fourth radiation element are disposed adjacent to the second side of the common ground element. 
     In some embodiments, the first radiation element substantially has an inverted U-shape defining a notch region. The second radiation element is disposed inside the notch region. 
     In some embodiments, the fourth radiation element is separate from the third radiation element. A coupling gap is formed between the third radiation element and the fourth radiation element. 
     In some embodiments, the antenna structure covers a first frequency band, a second frequency band, a third frequency band, and a fourth frequency band. The first frequency band is from 1710 MHz to 2170 MHz. The second frequency band is from 2300 MHz to 2700 MHz. The third frequency band is from 2400 MHz to 2500 MHz. The fourth frequency band is from 5150 MHz to 5850 MHz. 
     In some embodiments, the first radiation element is excited to generate the first frequency band. The length of the first radiation element is substantially equal to 0.25 wavelength of the first frequency band. 
     In some embodiments, the second radiation element is excited to generate the second frequency band. The length of the second radiation element is substantially equal to 0.25 wavelength of the second frequency band. 
     In some embodiments, the fourth radiation element and the common ground element are excited to generate the third frequency band. The total length of the fourth radiation element and the common ground element is substantially equal to 0.25 wavelength of the third frequency band. 
     In some embodiments, the third radiation element is excited to generate the fourth frequency band. The length of the third radiation element is substantially equal to 0.25 wavelength of the fourth frequency band. 
    
    
     
       BRIEF DESCRIPTION OF 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  is a top view of a mobile device according to an embodiment of the invention; 
         FIG. 2  is a diagram of return loss of an antenna structure of a mobile device according to an embodiment of the invention; 
         FIG. 3  is a diagram of return loss of an antenna structure of a mobile device according to an embodiment of the invention; 
         FIG. 4  is a diagram of radiation efficiency of an antenna structure of a mobile device according to an embodiment of the invention; 
         FIG. 5  is a diagram of radiation efficiency of an antenna structure of a mobile device according to an embodiment of the invention; 
         FIG. 6  is a diagram of isolation of an antenna structure of a mobile device according to an embodiment of the invention; and 
         FIG. 7  is a perspective view of a mobile device according to another embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In order to illustrate the purposes, features and advantages of the invention, the embodiments and figures of the invention are shown in detail as follows. 
     Certain terms are used throughout the description and following claims to refer to particular components. As one skilled in the art will appreciate, manufacturers may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function. In the following description and in the claims, the terms “include” and “comprise” are used in an open-ended fashion, and thus should be interpreted to mean “include, but not limited to . . . ”. The term “substantially” means the value is within an acceptable error range. One skilled in the art can solve the technical problem within a predetermined error range and achieve the proposed technical performance. Also, the term “couple” is intended to mean either an indirect or direct electrical connection. Accordingly, if one device is coupled to another device, that connection may be through a direct electrical connection, or through an indirect electrical connection via other devices and connections. 
       FIG. 1  is a top view of a mobile device  100  according to an embodiment of the invention. For example, the mobile device  100  may be a smart phone, a tablet computer, or a notebook computer. As shown in  FIG. 1 , the mobile device  100  at least includes a common ground element  110 , a connection element  120 , a first radiation element  130 , a second radiation element  140 , a third radiation element  150 , a fourth radiation element  160 , and a dielectric substrate  170 . The common ground element  110 , the connection element  120 , the first radiation element  130 , the second radiation element  140 , the third radiation element  150 , and the fourth radiation element  160  may be made of metal materials, such as copper, silver, aluminum, iron, or their alloys. The dielectric substrate  170  may be an FR4 (Flame Retardant 4) substrate, a PCB (Printed Circuit Board), or an FCB (Flexible Circuit Board). It should be understood that the mobile device  100  may further include other components, such as a display device, a speaker, a touch control module, a power supply module, and a housing, although they are not displayed in  FIG. 1 . 
     The common ground element  110  may substantially have a straight-line shape. The common ground element  110  has a first end  111  and a second end  112 . The first end  111  of the common ground element  110  is coupled to a ground voltage VSS. For example, the ground voltage VSS may be provided by a system ground plane (not shown) of the mobile device  100 . Specifically, the common ground element  110  has a first side  115  and a second side  116  which are opposite to each other. The connection element  120 , the first radiation element  130 , and the second radiation element  140  are all disposed adjacent to the first side  115  (e.g., the left side) of the common ground element  110 . The third radiation element  150  and the fourth radiation element  160  are both disposed adjacent to the second side  116  (e.g., the right side) of the common ground element  110 . It should be noted that both the first radiation element  130  and the fourth radiation element  160  are coupled through the common ground element  110  to the ground voltage VSS. 
     The connection element  120  may substantially have a rectangular shape or a square shape. The first radiation element  130  may substantially have an inverted U-shape defining a notch region  135 . The notch region  135  may substantially have a rectangular shape. The whole second radiation element  140  may be disposed inside the notch region  135  of the first radiation element  130 . The first radiation element  130  has a first feeding point FP 1 . The first feeding point FP 1  may be coupled to a first signal source  191 . Specifically, the first radiation element  130  has a first end  131  and a second end  132 . The first feeding point FP 1  is positioned at the first end  131  of the first radiation element  130 . The second end  132  of the first radiation element  130  is an open end. In addition, a bending portion  136  of the first radiation element  130  may be coupled through the connection element  120  to the second end  112  of the common ground element  110 . 
     The second radiation element  140  may substantially have a C-shape. The second radiation element  140  is at least partially surrounded by the first radiation element  130 . Specifically, the second radiation element  140  has a first end  141  and a second end  142 . The first end  141  of the second radiation element  140  is coupled to the first feeding point FP 1  and the first end  131  of the first radiation element  130 . The second end  142  of the second radiation element  140  is an open end. In addition, the second end  142  of the second radiation element  140  is adjacent to the bending portion  136  of the first radiation element  130 . It should be noted that the term “adjacent” or “close” over the disclosure means that the distance (spacing) between two corresponding elements is smaller than a predetermined distance (e.g., 5 mm or shorter), but usually does not mean that the two corresponding elements directly touch each other (i.e., the aforementioned distance/spacing therebetween is reduced to 0). 
     The third radiation element  150  may substantially have a straight-line shape, and it may be substantially perpendicular to the common ground element  110 . The third radiation element  150  has a second feeding point FP 2 . The second feeding point FP 2  may be coupled to a second signal source  192 . Specifically, the third radiation element  150  has a first end  151  and a second end  152 . The second feeding point FP 2  is positioned at the first end  151  of the third radiation element  150 . The second end  152  of the third radiation element  150  is an open end, which extends away from the common ground element  110 . 
     The fourth radiation element may substantially have an inverted C-shape, and it may be at least partially perpendicular to the common ground element  110  and is at least partially parallel to the third radiation element  150 . The fourth radiation element  160  is adjacent to the third radiation element  150  and is separate from the third radiation element  150 . A coupling gap GC 1  is formed between the third radiation element  150  and the fourth radiation element  160 . Specifically, the fourth radiation element  160  has a first end  161  and a second end  162 . The first end  161  of the fourth radiation element  160  is coupled to the second end  112  of the common ground element  110 . The second end  162  of the fourth radiation element  160  is an open end, which extends toward the common ground element  110 . 
     In some embodiments, an antenna structure is formed by the common ground element  110 , the connection element  120 , the first radiation element  130 , the second radiation element  140 , the third radiation element  150 , and the fourth radiation element  160 . Such an antenna structure is planar and is disposed on a surface of the dielectric substrate  170 . 
       FIG. 2  is a diagram of return loss of the antenna structure of the mobile device  100  according to an embodiment of the invention. The horizontal axis represents the operation frequency (MHz), and the vertical axis represents the return loss (dB). According to the measurement of  FIG. 2 , when being excited by the first signal source  191 , the antenna structure of the mobile device  100  can cover a first frequency band FB 1  and a second frequency band FB 2 . The first frequency band FB 1  may be from 1710 MHz to 2170 MHz. The second frequency band FB 2  may be from 2300 MHz to 2700 MHz. Therefore, the antenna structure of the mobile device  100  can support at least the dual-band MIMO (Multi-Input and Multi-Output) operations of WWAN (Wireless Wide Area Network). 
       FIG. 3  is a diagram of return loss of the antenna structure of the mobile device  100  according to an embodiment of the invention. The horizontal axis represents the operation frequency (MHz), and the vertical axis represents the return loss (dB). According to the measurement of  FIG. 3 , when being excited by the second signal source  192 , the antenna structure of the mobile device  100  can cover a third frequency band FB 3  and a fourth frequency band FB 4 . The third frequency band FB 3  may be from 2400 MHz to 2500 MHz. The fourth frequency band FB 4  may be from 5150 MHz to 5850 MHz. Therefore, the antenna structure of the mobile device  100  can support at least the dual-band operations of WLAN (Wireless Local Area Network) 2.4 GHz/5 GHz. 
     In some embodiments, the operation principles of the antenna structure of the mobile device  100  are described as follows. The first radiation element  130  is excited to generate the first frequency band FB 1 . The second radiation element  140  is excited to generate the second frequency band FB 2 . The fourth radiation element  160  and the common ground element  110  are excited to generate the third frequency band FB 3 . The third radiation element  150  is excited to generate the fourth frequency band FB 4 . According to practical measurements, the common ground element  110  is used as a grounding resonant path of the third frequency band FB 3 , and it is also configured to fine-tune the impedance matching of the first frequency band FB 1  and the second frequency band FB 2 . Therefore, the incorporation of the common ground element  110  helps to minimize the total size of the antenna structure of the mobile device  100 . 
       FIG. 4  is a diagram of radiation efficiency of the antenna structure of the mobile device  100  according to an embodiment of the invention. The horizontal axis represents the operation frequency (MHz), and the vertical axis represents the radiation efficiency (dB). According to the measurement of  FIG. 4 , the radiation efficiency of the antenna structure of the mobile device  100  can reach −4 dB within the first frequency band FB 1  and the second frequency band FB 2 , and it can meet the requirement of practical application of general WWAN communication. 
       FIG. 5  is a diagram of radiation efficiency of the antenna structure of the mobile device  100  according to an embodiment of the invention. The horizontal axis represents the operation frequency (MHz), and the vertical axis represents the radiation efficiency (dB). According to the measurement of  FIG. 5 , the radiation efficiency of the antenna structure of the mobile device  100  can reach −3.5 dB within the third frequency band FB 3  and the fourth frequency band FB 4 , and it can meet the requirement of practical application of general WLAN communication. 
       FIG. 6  is a diagram of isolation of the antenna structure of the mobile device  100  according to an embodiment of the invention. The horizontal axis represents the operation frequency (MHz), and the vertical axis represents the isolation (dB). According to the measurement of  FIG. 6 , when being fed by both the first signal source  191  and the second signal source  192 , the antenna structure of the mobile device  100  has isolation which reaches at least 8 dB within the first frequency band FB 1 , the second frequency band FB 2 , the third frequency band FB 3 , and the fourth frequency band FB 4 . It means that the first signal source  191  and the second signal source  192  do not tend to interfere with each other, thereby improving the whole radiation performance of the antenna structure of the mobile device  100 . 
     In some embodiments, the element sizes of the mobile device  100  are described as follows. The length of the first radiation element  130  (i.e., the length from the first end  131  to the second end  132 ) may be substantially equal to 0.25 wavelength (λ/4) of the first frequency band FB 1  of the antenna structure of the mobile device  100 . The length of the second radiation element  140  (i.e., the length from the first end  141  to the second end  142 ) may be substantially equal to 0.25 wavelength (λ/4) of the second frequency band FB 2  of the antenna structure of the mobile device  100 . The length of the third radiation element  150  (i.e., the length from the first end  151  to the second end  152 ) may be substantially equal to 0.25 wavelength (λ/4) of the fourth frequency band FB 4  of the antenna structure of the mobile device  100 . The total length of the fourth radiation element  160  and the common ground element  110  (i.e., the total length from the first end  111  through the second end  112  and the first end  161  to the second end  162 ) may be substantially equal to 0.25 wavelength (λ/4) of the third frequency band FB 3  of the antenna structure of the mobile device  100 . The distance D 1  between the first radiation element  130  and the common ground element  110  (or the length of the connection element  120 ) may be from 2 mm to 3 mm. The width of the coupling gap GC 1  (or the distance between the third radiation element  150  and the fourth radiation element  160 ) may be shorter than or equal to 2 mm. The total length LT of the antenna structure of the mobile device  100  may be shorter than or equal to 30 mm. The total length WT of the antenna structure of the mobile device  100  may be shorter than or equal to 8 mm. The ranges of the above element sizes are calculated and obtained according to many experimental results, and they help to optimize the operation bandwidth and impedance matching of the antenna structure of the mobile device  100 . 
       FIG. 7  is a perspective view of a mobile device  100  according to another embodiment of the invention. In the embodiment of  FIG. 7 , the mobile device  100  is a notebook computer which includes an upper cover  710 , a base  720 , and a hinge element  730 . The hinge element  730  is connected between the upper cover  710  and the base  720 , so that the notebook computer can operate while open or closed. Specifically, the base  720  has an edge  721 , and the aforementioned antenna structure may be disposed inside the base  720  and in a first position  751  or a second positioned  752  adjacent to the edge  721 . If the mobile device  100  has a metal housing, antenna windows may be opened and formed on the upper cover  710  and the base  720 , and thus the electromagnetic waves of the aforementioned antenna structure can be transmitted through the corresponding antenna windows. Other features of the mobile device  700  of  FIG. 7  are similar to those of the mobile device  100  of  FIG. 1 . Accordingly, the two embodiments can achieve similar levels of performance. 
     The invention proposes a novel mobile device and a novel antenna structure for covering both WWAN and WLAN operation frequency bands. By incorporating a design with a common ground element, the total area of the proposed wideband antenna structure of the invention is significantly reduced by 50% in comparison to conventional designs (the total length of a conventional integrated WWAN and WLAN antenna can reach 65 mm or longer). In conclusion, invention has the advantages of being small in size and having a wide bandwidth and a low manufacturing cost, and therefore it is suitable for application in a variety of mobile communication devices with narrow borders. 
     Note that the above element sizes, element shapes, and frequency ranges are not limitations of the invention. An antenna designer can fine-tune these settings or values according to different requirements. It should be understood that the mobile device and antenna structure of the invention are not limited to the configurations of  FIGS. 1-7 . The invention may merely include any one or more features of any one or more embodiments of  FIGS. 1-7 . In other words, not all of the features displayed in the figures should be implemented in the mobile device and antenna structure of the invention. 
     Use of ordinal terms such as “first”, “second”, “third”, etc., in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having the same name (but for use of the ordinal term) to distinguish the claim elements. 
     While the invention has been described by way of example and in terms of the preferred embodiments, it should be understood that the invention is not limited to the disclosed embodiments. On 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.