Patent Publication Number: US-11398679-B2

Title: Antenna structure

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority of Taiwan Patent Application No. 109141722 filed on Nov. 27, 2020, the entirety of which is incorporated by reference herein. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The disclosure generally relates to an antenna structure, and more particularly, it relates to a wideband antenna structure. 
     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 used for signal reception and transmission has insufficient bandwidth, it will negatively affect the communication quality of the mobile device. Accordingly, it has become a critical challenge for antenna designers to design a small-size, wideband antenna element. 
     BRIEF SUMMARY OF THE INVENTION 
     In an exemplary embodiment, the disclosure is directed to an antenna structure that includes a first radiation element, a second radiation element, a third radiation element, a fourth radiation element, a fifth radiation element, and a nonconductive support element. The first radiation element has a feeding point. The second radiation element is coupled to the feeding point. The third radiation element has a grounding point. The fourth radiation element is coupled to the third radiation element. The fourth radiation element is adjacent to the first radiation element and the second radiation element. The fifth radiation element is coupled to the third radiation element and the fourth radiation element. The first radiation element, the second radiation element, the third radiation element, the fourth radiation element, and the fifth radiation element are disposed on the nonconductive support element. 
     In some embodiments, the antenna structure covers a first frequency band, a second frequency band, and a third frequency band. The first frequency band is from 728 MHz to 960 MHz. The second frequency band is from 1805 MHz to 2200 MHz. The third frequency band is from 2300 MHz to 2690 MHz. 
     In some embodiments, the first radiation element substantially has a U-shape. 
     In some embodiments, the first radiation element is a variable-width structure and includes a first widening portion and a second widening portion. 
     In some embodiments, the length of the first radiation element is from 0.1 to 0.2 wavelength of the highest frequency of the first frequency band. 
     In some embodiments, the second radiation element substantially has a straight-line shape. 
     In some embodiments, the length of the second radiation element is from 0.05 to 0.2 wavelength of the highest frequency of the third frequency band. 
     In some embodiments, the third radiation element substantially has an L-shape. 
     In some embodiments, the fourth radiation element is a meandering structure. 
     In some embodiments, a first coupling gap is formed between the fourth radiation element and the first radiation element. The width of the first coupling gap is from 0.1 mm to 1 mm. 
     In some embodiments, a second coupling gap is formed between the fourth radiation element and the second radiation element. The width of the second coupling gap is from 0.1 mm to 1 mm. 
     In some embodiments, the total length of the third radiation element and the fourth radiation element is from 0.1 to 0.2 wavelength of the lowest frequency of the first frequency band. 
     In some embodiments, the fifth radiation element substantially has an L-shape. 
     In some embodiments, the total length of the third radiation element and the fifth radiation element is from 0.1 to 0.3 wavelength of the lowest frequency of the second frequency band. 
     In some embodiments, the antenna structure further includes a sixth radiation element coupled to the feeding point. The sixth radiation element is substantially perpendicular to the first radiation element and the second radiation element. 
     In some embodiments, the sixth radiation element substantially has a straight-line shape. 
     In some embodiments, the antenna structure further includes a seventh radiation element coupled to a first connection point on the fourth radiation element. The seventh radiation element is adjacent to the first widening portion and the second widening portion of the first radiation element. 
     In some embodiments, the seventh radiation element substantially has an L-shape. 
     In some embodiments, the antenna structure further includes an eighth radiation element coupled to a second connection point on the fourth radiation element. The eighth radiation element is substantially perpendicular to the fourth radiation element. 
     In some embodiments, the first radiation element, the second radiation element, the third radiation element, the fourth radiation element, and the fifth radiation element are disposed on the nonconductive support element by using LDS (Laser Direct Structuring) technology. 
    
    
     
       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 perspective view of an antenna structure according to an embodiment of the invention; 
         FIG. 2  is a diagram of return loss of an antenna structure according to an embodiment of the invention; and 
         FIG. 3  is a diagram of radiation efficiency of an antenna structure according to an 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 below. 
     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. 
     The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. 
     Furthermore, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly. 
       FIG. 1  is a perspective view of an antenna structure  100  according to an embodiment of the invention. The antenna structure  100  may be applied to a mobile device, such as a joystick, a smartphone, a tablet computer, or a notebook computer. In the embodiment of  FIG. 1 , the antenna structure  100  at least includes a first radiation element  110 , a second radiation element  120 , a third radiation element  130 , a fourth radiation element  140 , a fifth radiation element  150 , and a nonconductive support element  190 . The first radiation element  110 , the second radiation element  120 , the third radiation element  130 , the fourth radiation element  140 , and the fifth radiation element  150  may all be made of metal materials, such as silver, copper, aluminum, iron, or their alloys. 
     The nonconductive support element  190  may be a 3D (Three-Dimensional) structure with a first surface E 1 , a second surface E 2 , a third surface E 3 , and a fourth surface E 4 . For example, the second surface E 2  and the fourth surface E 4  may be next to each other, and they may both be substantially perpendicular to the first surface E 1 . In addition, the third surface E 3  may be connected between the first surface E 1  and the second surface E 2 . The third surface E 3  may be neither parallel nor perpendicular to the first surface E 1  and the second surface E 2 . The first radiation element  110 , the second radiation element  120 , the third radiation element  130 , the fourth radiation element  140 , and the fifth radiation element  150  are distributed over the first surface E 1 , the second surface E 2 , the third surface E 3 , and the fourth surface E 4  of the nonconductive support element  190 . In some embodiments, the nonconductive support element  190  further has an opening  195 , which may be substantially circular. A variety of electronic elements may pass through the opening  195 . For example, the aforementioned electronic element may be a metal connection element or a circuit element. However, the invention is not limited thereto. In alternative embodiments, the opening  195  may be filled or removed from the nonconductive support element  190 . In some embodiments, the first radiation element  110 , the second radiation element  120 , the third radiation element  130 , the fourth radiation element  140 , and the fifth radiation element  150  are all disposed on the nonconductive support element  190  by using LDS (Laser Direct Structuring) technology. 
     The first radiation element  110  may substantially have a U-shape, which may extend from the first surface E 1  through the fourth surface E 4  onto the second surface E 2  of the nonconductive support element  190 . Specifically, the first radiation element  110  has a first end  111  and a second end  112 . A feeding point FP is positioned at the first end  111  of the first radiation element  110 . The second end  112  of the first radiation element  110  is an open end. The feeding point FP may be further coupled to a signal source (not shown). For example, the aforementioned signal source may be an RF (Radio Frequency) module for exciting the antenna structure  100 . In some embodiments, the first radiation element  110  is a variable-width structure, and includes a first widening portion  114  and a second widening portion  115  which are coupled to each other. However, the invention is not limited thereto. In alternative embodiments, adjustments may be made so that the first radiation element  110  is an equal-width structure. 
     The second radiation element  120  may substantially have a straight-line shape, which may be disposed on the first surface E 1  of the nonconductive support element  190 . Specifically, the second radiation element  120  has a first end  121  and a second end  122 . The first end  121  of the second radiation element  120  is coupled to the feeding point FP. The second end  122  of the second radiation element  120  is an open end. The second end  122  of the second radiation element  120  and the second end  112  of the first radiation element  110  may substantially extend in the same direction. 
     The third radiation element  130  may substantially have an L-shape, which may extend from the first surface E 1  onto the third surface E 3  of the nonconductive support element  190 . Specifically, the third radiation element  130  has a first end  131  and a second end  132 . A grounding point GP is positioned at the first end  131  of the third radiation element  130 . The grounding point GP may be further coupled to a system ground plane (not shown) of the antenna structure  100 . 
     The fourth radiation element  140  may be a meandering structure, which may extend from the third surface E 3  through the first surface E 1  onto the fourth surface E 4 . Specifically, the fourth radiation element  140  has a first end  141  and a second end  142 . The first end  141  of the fourth radiation element  140  is coupled to the second end  132  of the third radiation element  130 . The second end  142  of the fourth radiation element  140  is an open end. The fourth radiation element  140  is adjacent to the first radiation element  110  and the second radiation element  120 . It should be noted that the term “adjacent” or “close” over the disclosure means that the distance (spacing) between two corresponding elements is shorter than a predetermined distance (e.g., 5 mm or shorter), but often it does not mean that the two corresponding elements are touching each other directly (i.e., the aforementioned distance/spacing therebetween is reduced to 0). In some embodiments, a first coupling gap GC 1  is formed between the fourth radiation element  140  and the first radiation element  110 , and a second coupling gap GC 2  is formed between the fourth radiation element  140  and the second radiation element  120 . 
     The fifth radiation element  150  may substantially have an L-shape, which may extend from the third surface E 3  onto the second surface E 2  of the nonconductive support element  190 . Specifically, the fifth radiation element  150  has a first end  151  and a second end  152 . The first end  151  of the fifth radiation element  150  is coupled to the second end  132  of the third radiation element  130  and the first end  141  of the fourth radiation element  140 . The second end  152  of the fifth radiation element  150  is an open end, which is adjacent to the second end  112  of the first radiation element  110 . The second end  152  of the fifth radiation element  150  and the second end  122  of the second radiation element  120  may substantially extend in opposite directions. 
     In some embodiments, the antenna structure  100  further includes a sixth radiation element  160 . The sixth radiation element  160  may substantially have a straight-line shape, which may be disposed on the first surface E 1  of the nonconductive support element  190 . Specifically, the sixth radiation element  160  has a first end  161  and a second end  162 . The first end  161  of the sixth radiation element  160  is coupled to the feeding point FP. The second end  162  of the sixth radiation element  160  is an open end. The sixth radiation element  160  may be substantially perpendicular to the first radiation element  110  and the second radiation element  120 . It should be understood that the sixth radiation element  160  is an optional element, which is removable from the antenna structure  100  in other embodiments. 
     In some embodiments, the antenna structure  100  further includes a seventh radiation element  170 . The seventh radiation element  170  may substantially have an L-shape, which may be disposed on the fourth surface E 4  of the nonconductive support element  190 . Specifically, the seventh radiation element  170  has a first end  171  and a second end  172 . The first end  171  of the seventh radiation element  170  is coupled to a first connection point CP 1  on the fourth radiation element  140 . The second end  172  of the seventh radiation element  170  is an open end, which is adjacent to the first widening portion  114  and the second widening portion  115  of the first radiation element  110 . It should be understood that the seventh radiation element  170  is an optional element, which is removable from the antenna structure  100  in other embodiments. 
     In some embodiments, the antenna structure  100  further includes an eighth radiation element  180 . The eighth radiation element  180  may substantially have a straight-line shape, which may be disposed on the fourth surface E 4  of the nonconductive support element  190 . Specifically, the eighth radiation element  180  has a first end  181  and a second end  182 . The first end  181  of the eighth radiation element  180  is coupled to a second connection point CP 2  on the fourth radiation element  140 . The second end  182  of the eighth radiation element  180  is an open end. The second connection point CP 2  is different from the first connection point CP 1 . The eighth radiation element  180  may be substantially perpendicular to the fourth radiation element  140 . It should be understood that the eighth radiation element  180  is an optional element, which is removable from the antenna structure  100  in other embodiments. 
       FIG. 2  is a diagram of return loss of the antenna structure  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 , the antenna structure  100  can cover a first frequency band FB 1 , a second frequency band FB 2 , and a third frequency band FB 3 . For example, the first frequency band FB 1  may be from 728 MHz to 960 MHz, the second frequency band FB 2  may be from 1805 MHz to 2200 MHz, and the third frequency band FB 3  may be from 2300 MHz to 2690 MHz. Accordingly, the antenna structure  100  can support at least the wideband operations of Wi-Fi 2.4 GHz, LTE (Long Term Evolution), and 5G (5 th  Generation Mobile Networks) communication of the next generation. 
     With respect to the antenna theory, the third radiation element  130  and the fourth radiation element  140  are excited by the first radiation element  110  using a coupling mechanism, thereby forming the aforementioned first frequency band FB 1 . The third radiation element  130  and the fifth radiation element  150  are excited by the first radiation element  110  and the fourth radiation element  140  using a coupling mechanism, thereby forming the aforementioned second frequency band FB 2 . The second radiation element  120  is independently excited, thereby forming the aforementioned third frequency band FB 3 . It should be understood that the double-frequency effect of the excitations of the first radiation element  110 , the third radiation element  130 , and the fourth radiation element  140  also contributes to the generation of the second frequency band FB 2  and the third frequency band FB 3 . According to practical measurements, the incorporation of the sixth radiation element  160  helps to fine-tune the impedance matching of the second frequency band FB 2 , and the incorporation of the seventh radiation element  170  and the eighth radiation element  180  helps to fine-tune the impedance matching of the first frequency band FB 1 . In addition, the first widening portion  114  and the second widening portion  115  of the first radiation element  110  can increase the operation bandwidth of the first frequency band FB 1 . 
       FIG. 3  is a diagram of radiation efficiency of the antenna structure  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. 3 , the radiation efficiency of the antenna structure  100  is higher than −9 dB within the first frequency band FB 1 , the second frequency band FB 2 , and the third frequency band FB 3  as mentioned above, and it can meet the requirements of practical application of general mobile communication devices. 
     In some embodiments, the element sizes and element parameters of the antenna structure  100  are described as follows. The length L 1  of the first radiation element  110  may be from 0.1 to 0.2 wavelength (0.1λ˜0.2λ) of the highest frequency of the first frequency band FB 1  of the antenna structure  100 ; e.g., about 0.17 wavelength (0.17λ). The length L 2  of the second radiation element  120  may be from 0.05 to 0.2 wavelength (0.05λ˜0.2λ) of the highest frequency of the third frequency band FB 3  of the antenna structure  100 ; e.g., about 0.15 wavelength (0.15λ). The total length L 3  of the third radiation element  130  and the fourth radiation element  140  may be from 0.1 to 0.2 wavelength (0.1λ˜0.2λ) of the lowest frequency of the first frequency band FB 1  of the antenna structure  100 ; e.g., about 0.15 wavelength (0.15λ). The total length L 4  of the third radiation element  130  and the fifth radiation element  150  may be from 0.1 to 0.3 wavelength (0.1λ˜0.3λ) of the lowest frequency of the second frequency band FB 2  of the antenna structure  100 ; e.g., about 0.2 wavelength (0.2λ). The length L 5  of the sixth radiation element  160  may be from 5 mm to 9 mm; e.g., about 7 mm. The length L 6  of the seventh radiation element  170  may be from 8 mm to 12 mm; e.g., about 10 mm. The length L 7  of the eighth radiation element  180  may be from 4 mm to 6 mm; e.g., about 5 mm. The width of the first coupling gap GC 1  may be from 0.1 mm to 1 mm; e.g., about 0.5 mm. The width of the second coupling gap GC 2  may be from 0.1 mm to 1 mm; e.g., about 0.5 mm. The distance D 1  between the feeding point FP and the grounding point GP may be from 1 mm to 2 mm; e.g., about 1.5 mm. The total length LT of the antenna structure  100  may be about 28 mm, and the total width WT of the antenna structure  100  may be about 14 mm. The above ranges of element sizes and element parameters are calculated and obtained according to many experiment results, and they help to optimize the operation bandwidth and the impedance matching of the antenna structure  100 . 
     In alternative embodiments, the antenna structure  100  is adjacent to an NFC (Near-Field Communication) antenna  199  (which is another independent antenna, and is not a portion of the antenna structure  100 ). According to practical measurements, if the NFC antenna  199  is disposed inside a non-metal region next to the fourth radiation element  140 , it does not negatively affect the radiation performance of the antenna structure  100  so much. Therefore, the design of the antenna structure  100  can help to minimize the total antenna size. 
     The invention proposes a novel antenna structure. In comparison to the conventional technology, the invention has at least the advantages of small size, wide bandwidth, low manufacturing cost, and adapting to different use environments, and therefore it is suitable for application in a variety of mobile communication devices. 
     Note that the above element sizes, element shapes, element parameters, 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 antenna structure of the invention is not limited to the configurations of  FIGS. 1-3 . The invention may merely include any one or more features of any one or more embodiments of  FIGS. 1-3 . In other words, not all of the features displayed in the figures should be implemented in the 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.