Patent Publication Number: US-10763594-B1

Title: Antenna system

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority of Taiwan Patent Application No. 108104352 filed on Feb. 11, 2019, the entirety of which is incorporated by reference herein. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The disclosure generally relates to an antenna system, and more particularly, to an antenna system for generating different radiation patterns. 
     Description of the Related Art 
     Antenna arrays have high directivity and high gain, and they are widely used in the fields of military technology, radar detection, life detection, and health monitoring. However, if a conventional antenna array has an adjustable radiation pattern, it should use many antenna arrays and may occupy a large design space. It has become a critical challenge for current engineers to design a small-size antenna system and an antenna array thereof. 
     BRIEF SUMMARY OF THE INVENTION 
     In an exemplary embodiment, the invention is directed to an antenna system including a power divider, a first antenna array, a second antenna array, a third antenna array, a delay device, a first switch element, and a second switch element. The power divider has a first output port, a second output port, and a third output port. The first antenna array is coupled to the first output port. The second antenna array is coupled to the second output port. The third antenna array is coupled to the third output port. The first switch element determines whether to couple the first output port to the delay device according to a first control signal. The second switch element determines whether to couple the third output port to a ground voltage according to a second control signal. 
     In some embodiments, the delay phase of the delay device is substantially equal to 180 degrees. 
     In some embodiments, the first antenna array has a first feeding point. The first control signal includes a first control voltage, a second control voltage, and a third control voltage. 
     In some embodiments, the first switch element includes a first diode, a second diode, and a third diode. The first diode has an anode coupled to the first output port, and a cathode coupled to the first feeding point. The second diode has an anode coupled to the first node, and a cathode coupled to the first output port. The third diode has an anode coupled to a second node, and a cathode coupled to the first feeding point. The delay device is coupled between the first node and the second node. 
     In some embodiments, the first diode, the second diode, and the third diode are three PIN diodes controlled by the first control voltage, the second control voltage, and the third control voltage. 
     In some embodiments, the first switch element further includes a first inductor, a second inductor, and a third inductor. The first inductor is coupled between the first output port and the first control node. The first control node is arranged for receiving the first control voltage. The second inductor is coupled between the first node and a second control node. The second control node is arranged for receiving the second control voltage. The third inductor is coupled between the second node and a third control node. The third control node is arranged for receiving the third control voltage. 
     In some embodiments, the third antenna array has a third feeding point. The second control signal includes a fourth control voltage. 
     In some embodiments, the second switch element includes a fourth diode. The fourth diode has an anode coupled to the third output port and the third feeding point, and a cathode coupled to the ground voltage. 
     In some embodiments, the fourth diode is a PIN diode controlled by the fourth control voltage. 
     In some embodiments, the second switch element further includes a fourth inductor and a capacitor. The fourth inductor is coupled between the third output port and a fourth control node. The fourth control node is arranged for receiving the fourth control voltage. The capacitor is coupled between the fourth control node and the ground voltage. 
     In some embodiments, when the antenna system operates in a first mode, the first diode is turned on, and the second diode, the third diode, and the fourth diode are turned off, such that the antenna system generates a first radiation pattern including a single main beam. 
     In some embodiments, when the antenna system operates in a second mode, the first diode is turned off, and the second diode, the third diode, and the fourth diode are turned on, such that the antenna system generates a second radiation pattern including two different main beams. 
     In some embodiments, the central operation frequency of the antenna system is substantially equal to 24 GHz. 
     In some embodiments, each of the first antenna array, the second antenna array, and the third antenna array includes a first radiation element, a second radiation element, a third radiation element, a fourth radiation element, a fifth radiation element, a first connection element, a second connection element, a third connection element, and a fourth connection element. The first connection element is coupled between the first radiation element and the second radiation element. The second connection element is coupled between the second radiation element and the third radiation element. The third connection element is coupled between the third radiation element and the fourth radiation element. The fourth connection element is coupled between the fourth radiation element and the fifth radiation element. 
     In some embodiments, the first radiation element, the second radiation element, the third radiation element, the fourth radiation element, the fifth radiation element, the first connection element, the second connection element, the third connection element, and the fourth connection element are arranged in the same straight line. 
     In some embodiments, the length of each of the first radiation element, the second radiation element, the third radiation element, the fourth radiation element, and the fifth radiation element is substantially equal to 0.5 wavelength of the central operation frequency. 
     In some embodiments, the length of each of the first connection element, the second connection element, the third connection element, and the fourth connection element is substantially equal to 0.5 wavelength of the central operation frequency. 
    
    
     
       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. 1A  is a diagram of an antenna system according to an embodiment of the invention; 
         FIG. 1B  is a diagram of an antenna system according to another embodiment of the invention; 
         FIG. 2  is a diagram of a first switch element according to an embodiment of the invention; 
         FIG. 3  is a diagram of a second switch element according to an embodiment of the invention; 
         FIG. 4  is a diagram of an antenna array according to an embodiment of the invention; 
         FIG. 5A  is a diagram of a practical layout of an antenna system according to an embodiment of the invention; 
         FIG. 5B  is a diagram of a practical layout of an antenna system according to another embodiment of the invention; 
         FIG. 6A  is a radiation pattern of an antenna system operating in a first mode according to an embodiment of the invention; and 
         FIG. 6B  is a radiation pattern of an antenna system operating in a second mode according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In order to illustrate the foregoing and other purposes, features and advantages of the invention, the embodiments and figures of the invention will be described 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. 1A  is a diagram of an antenna system  100  according to an embodiment of the invention. The antenna system  100  may be applicable to a communication device, such as a vehicle radar or a home security device, but it is not limited thereto. In the embodiment of  FIG. 1A , the antenna system  100  includes a power divider  110 , a first antenna array  120 , a second antenna array  130 , a third antenna array  140 , a delay device  150 , a first switch element  160 , and a second switch element  170 . It should be understood that the antenna system  100  may further include other components, such as a processor, a controller, a voltage generator, and/or a battery module, although they are not displayed in  FIG. 1A . 
     The power divider  110  has a first output port P 1 , a second output port P 2 , and a third output port P 3 . The power divider  110  is configured to receive an input signal SIN and then divide the input signal SIN into a first output signal SOUT 1 , a second output signal SOUT 2 , and a third output signal SOUT 3 . Specifically, the first output port P 1 , the second output port P 2 , and the third output port P 3  of the power divider  110  are arranged for outputting the first output signal SOUT 1 , the second output signal SOUT 2 , and the third output signal SOUT 3 , respectively. The first output signal SOUT 1 , the second output signal SOUT 2 , and the third output signal SOUT 3  may have the same power, which may be substantially equal to ⅓ times the power of the input signal SIN. 
     The first antenna array  120 , the second antenna array  130 , and the third antenna array  140  are all excited by the power divider  110 . Specifically, the first antenna array  120  has a first feeding point FP 1  coupled to the first output port P 1  of the power divider  110 , the second antenna array  130  has a second feeding point FP 2  coupled to the second output port P 2  of the power divider  110 , and the third antenna array  140  has a third feeding point FP 3  coupled to the third output port P 3  of the power divider  110 . The total sizes of the first antenna array  120 , the second antenna array  130 , and the third antenna array  140  and the types of antenna elements are not limited in the invention. For example, each of first antenna array  120 , the second antenna array  130 , and the third antenna array  140  may be a 1×1, 1×2, 1×5, 1×7, or 1×9 antenna array, but it is not limited thereto. 
     The delay device  150  may be a phase delay line. The delay device  150  is configured to selectively adjust a feeding phase of the first antenna array  120 . In some embodiments, a delay phase of the delay device  150  is substantially equal to 180 degrees. In alternative embodiments, the delay phase of the delay device  150  is substantially equal to 45, 90, 135, 225 or 270 degrees. The first switch element  160  determines whether to couple the first output port P 1  and the first feeding point FP 1  to the delay device  150  according to a first control signal SC 1 . The second switch element  170  determines whether to couple the second output port P 2  and the second feeding point FP 2  to a ground voltage VSS according to a second control signal SC 2 . For example, the first control signal SC 1  and the second control signal SC 2  may be generated by a processor of the antenna system  100  according to a user&#39;s input, environmental information or computer instructions (not shown). 
     In some embodiments, the antenna system  100  operates in a first mode and a second mode, which correspond to different radiation patterns. When the antenna system  100  operates in the first mode, the first output port P 1  of the power divider  110  is directly coupled to the first feeding point FP 1  of the first antenna array  120  (without communicating through the delay device  150 ) by using the first switch element  160 , and the second output port P 2  of the power divider  110  and the second feeding point FP 2  of the second antenna array  130  are not coupled to the ground voltage VSS by using the second switch element  170 , such that the antenna system  100  can generate a first radiation pattern. Conversely, when the antenna system  100  operates in the second mode, the first output port P 1  of the power divider  110  is coupled through the delay device  150  to the first feeding point FP 1  of the first antenna array  120  by using the first switch element  160 , and the second output port P 2  of the power divider  110  and the second feeding point FP 2  of the second antenna array  130  are coupled to the ground voltage VSS by using the second switch element  170 , such that the antenna system  100  can generate a second radiation pattern. The second radiation pattern may be different from the first radiation pattern. With such a design, the invention uses a single antenna system, which can generate an adjustable radiation pattern without increasing additional antenna area, so as to meet a variety of requirements of practical applications. 
       FIG. 1B  is a diagram of an antenna system  180  according to another embodiment of the invention.  FIG. 1B  is similar to  FIG. 1A . In the embodiment of  FIG. 1B , the position of the second switch element  170  is changed, and the second output port P 2  of the power divider  110  is directly coupled to the second feeding point FP 2  of the second antenna array  130 . The antenna system  180  also operates in a first mode and a second mode. When the antenna system  180  operates in the first mode, the first output port P 1  of the power divider  110  is directly coupled to the first feeding point FP 1  of the first antenna array  120  (without communicating through the delay device  150 ) by using the first switch element  160 , and the third output port P 3  of the power divider  110  and the third feeding point FP 3  of the third antenna array  140  are not coupled to the ground voltage VSS by using the second switch element  170 , such that the antenna system  180  can generate a first radiation pattern. Conversely, when the antenna system  180  operates in the second mode, the first output port P 1  of the power divider  110  is coupled through the delay device  150  to the first feeding point FP 1  of the first antenna array  120  by using the first switch element  160 , and the third output port P 3  of the power divider  110  and the third feeding point FP 3  of the third antenna array  140  are coupled to the ground voltage VSS by using the second switch element  170 , such that the antenna system  180  can generate a second radiation pattern. Other features of the antenna system  180  of  FIG. 1B  are similar to those of the antenna system  100  of  FIG. 1A . Accordingly, the two embodiments can achieve similar levels of performance. 
     The following embodiments will introduce the circuitry and structure of the proposed switch element and antenna array. It should be understood that these figures and descriptions are merely exemplary, rather than limitations of the invention. 
       FIG. 2  is a diagram of the first switch element  160  according to an embodiment of the invention. In the embodiment of  FIG. 2 , the first switch element  160  at least includes a first diode D 1 , a second diode D 2 , and a third diode D 3 . Specifically, the first control signal SC 1  includes a first control voltage VC 1 , a second control voltage VC 2 , and a third control voltage VC 3 . The first diode D 1 , the second diode D 2 , and the third diode D 3  may be three PIN diodes controlled by the first control voltage VC 1 , the second control voltage VC 2 , and the third control voltage VC 3 . The first diode D 1  has an anode coupled to the first output port P 1 , and a cathode coupled to the first feeding point FP 1 . The second diode D 2  has an anode coupled to the first node N 1 , and a cathode coupled to the first output port P 1 . The third diode D 3  has an anode coupled to a second node N 2 , and a cathode coupled to the first feeding point FP 1 . The delay device  150  has a first terminal coupled to the first node N 1 , and a second terminal coupled to the second node N 2 . By controlling the first diode D 1 , the second diode D 2 , and the third diode D 3 , the first output port P 1  of the power divider  110  is selectively coupled through the delay device  150  to the first feeding point FP 1  of the first antenna array  120 . 
     In some embodiments, the first switch element  160  further includes a first inductor L 1 , a second inductor L 2 , and a third inductor L 3 . The first inductor L 1  is coupled between the first output port P 1  and the first control node NC 1 . The first control node NC 1  is arranged for receiving the first control voltage VC 1 . The second inductor L 2  is coupled between the first node N 1  and a second control node NC 2 . The second control node NC 2  is arranged for receiving the second control voltage VC 2 . The third inductor L 3  is coupled between the second node N 2  and a third control node NC 3 . The third control node NC 3  is arranged for receiving the third control voltage VC 3 . The first inductor L 1 , the second inductor L 2 , and the third inductor L 3  are configured to filter out high-frequency noise. For example, the inductance of each of the first inductor L 1 , the second inductor L 2 , and the third inductor L 3  may be greater than 10 nH. In some embodiments, any of the first inductor L 1 , the second inductor L 2 , and the third inductor L 3  is implemented with a microstrip line, such as a fan-shape transmission line, whose length may be substantially equal to 0.25 wavelength (λ/4) of a central operation frequency of the antenna system  100  (or  180 ). 
       FIG. 3  is a diagram of the second switch element  170  according to an embodiment of the invention. In the embodiment of  FIG. 3 , the second switch element  170  at least includes a fourth diode D 4 . Specifically, the second control signal SC 2  includes a fourth control voltage VC 4 . The fourth diode D 4  may be a PIN diode controlled by the fourth control voltage VC 4 . If it is applied to the antenna system  100  of  FIG. 1A , the fourth diode D 4  has an anode coupled to the second output port P 2  and the second feeding point FP 2 , and a cathode coupled to the ground voltage VSS. By controlling the fourth diode D 4 , the second output port P 2  of the power divider  110  is selectively coupled to the ground voltage VSS. If the second output port P 2  of the power divider  110  is directly coupled to the ground voltage VSS, the second feeding point FP 2  of the second antenna array  130  will not receive the feeding energy from the power divider  110 , that is, the second antenna array  130  will be disabled. 
     On the other hand, if it is applied to the antenna system  180  of  FIG. 1B , the fourth diode D 4  has an anode coupled to the third output port P 3  and the third feeding point FP 3 , and a cathode coupled to the ground voltage VSS. By controlling the fourth diode D 4 , the third output port P 3  of the power divider  110  is selectively coupled to the ground voltage VSS. If the third output port P 3  of the power divider  110  is directly coupled to the ground voltage VSS, the third feeding point FP 3  of the third antenna array  140  will not receive the feeding energy from the power divider  110 , that is, the third antenna array  140  will be disabled. 
     In some embodiments, the second switch element  170  further includes a fourth inductor L 4  and a capacitor C 1 . If it is applied to the antenna system  100  of  FIG. 1A , the fourth inductor L 4  is coupled between the second output port P 2  (or the second feeding point FP 2 ) and a fourth control node NC 4 . The fourth control node NC 4  is arranged for receiving the fourth control voltage VC 4 . If it is applied to the antenna system  180  of  FIG. 1B , the fourth inductor L 4  is coupled between the third output port P 3  (or the third feeding point FP 3 ) and the fourth control node NC 4 . The capacitor C 1  is coupled between the fourth control node NC 4  and the ground voltage VSS. The fourth inductor L 4  is configured to filter out high-frequency noise. For example, the inductance of the fourth inductor L 4  may be greater than 5 nH. The capacitor C 1  is configured to filter out low-frequency noise. For example, the capacitance of the capacitor C 1  may be greater than 10 pF. In some embodiments, the fourth inductor L 4  is implemented with another microstrip line, such as another fan-shape transmission line, whose length may be substantially equal to 0.25 wavelength (λ/4) of the central operation frequency of the antenna system  100  (or  180 ). 
     It should be understood that the first inductor L 1 , the second inductor L 2 , the third inductor L 3 , the fourth inductor L 4 , and the capacitor C 1  are optional elements, and they are omitted in other embodiments. The omitted inductor or capacitor may be replaced with a transmission line or a short-circuited path. 
     In some embodiments, the relative settings of the first mode and the second mode of the antenna system  100  (or  180 ) are described in Table I and Table II. 
     
       
         
           
               
             
               
                 TABLE I 
               
             
            
               
                   
               
               
                 Relationship between States of Diodes and Modes of Antenna System 
               
            
           
           
               
               
               
            
               
                   
                 First Mode 
                 Second Mode 
               
               
                   
               
               
                 First Diode D1 
                 Turned ON 
                 Turned OFF 
               
               
                 Second Diode D2 
                 Turned OFF 
                 Turned ON 
               
               
                 Third Diode D3 
                 Turned OFF 
                 Turned ON 
               
               
                 Fourth Diode D4 
                 Turned OFF 
                 Turned ON 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE II 
               
             
            
               
                   
               
               
                 Relationship between Levels of  
               
               
                 Control Voltages and Modes of Antenna System 
               
            
           
           
               
               
               
            
               
                   
                 First Mode 
                 Second Mode 
               
               
                   
               
               
                 First Control Voltage VC1 
                 High Logic Level 
                 Low Logic Level 
               
               
                 Second Control Voltage VC2 
                 Low Logic Level 
                 High Logic Level 
               
               
                 Third Control Voltage VC3 
                 Low Logic Level 
                 High Logic Level 
               
               
                 Fourth Control Voltage VC4 
                 Low Logic Level 
                 High Logic Level 
               
               
                   
               
            
           
         
       
     
     Specifically, when the antenna system  100  (or  180 ) operates in the first mode, the first diode D 1  is turned on, but the second diode D 2 , the third diode D 3  and the fourth diode D 4  are turned off. In the first mode, the first antenna array  120 , the second antenna array  130 , and the third antenna array  140  are all enabled (the feeding phase of the first antenna array  120  is not delayed), and therefore the antenna system  100  (or  180 ) can generate a first radiation pattern including relatively centralized main beams. Conversely, when the antenna system operates in the second mode, the first diode D 1  is turned off, but the second diode D 2 , the third diode D 3 , and the fourth diode D 4  are turned on. In the second mode, if it is applied to the antenna system  100  of  FIG. 1A , the first antenna array  120  and the third antenna array  140  are both enabled (the feeding phase of the first antenna array  120  is delayed for 180 degrees), and only the second antenna array  130  is disabled. On the other hand, in the second mode, if it is applied to the antenna system  180  of  FIG. 1B , the first antenna array  120  and the second antenna array  130  are both enabled (the feeding phase of the first antenna array  120  is delayed for 180 degrees), and only the third antenna array  140  is disabled. Each of the antenna systems  100  and  180  operating in the second mode can generate a second radiation pattern including relatively disperse main beams. 
       FIG. 4  is a diagram of the first antenna array  120  according to an embodiment of the invention. It should be noted that the first antenna array  120 , the second antenna array  130 , and the third antenna array  140  have the same symmetrical structures, and  FIG. 4  merely describes the first antenna array  120  as an example. In the embodiment of  FIG. 4 , each of the first antenna array  120 , the second antenna array  130 , and the third antenna array  140  includes a first radiation element  121 , a second radiation element  122 , a third radiation element  123 , a fourth radiation element  124 , a fifth radiation element  125 , a first connection element  126 , a second connection element  127 , a third connection element  128 , and a fourth connection element  129 . In some embodiments, each of the first radiation element  121 , the second radiation element  122 , the third radiation element  123 , the fourth radiation element  124 , and the fifth radiation element  125  substantially has a rectangular shape, and each of the first connection element  126 , the second connection element  127 , the third connection element  128 , and the fourth connection element  129  substantially has a straight-line shape. The first radiation element  121  is coupled to a corresponding one of the first feeding point FP 1 , the second feeding point FP 2 , and the third feeding point FP 3 . The fifth radiation element  125  has an open end. The first connection element  126  is coupled between the first radiation element  121  and the second radiation element  122 . The second connection element  127  is coupled between the second radiation element  122  and the third radiation element  123 . The third connection element  128  is coupled between the third radiation element  123  and the fourth radiation element  124 . The fourth connection element  129  is coupled between the fourth radiation element  124  and the fifth radiation element  125 . Generally, the first radiation element  121 , the second radiation element  122 , the third radiation element  123 , the fourth radiation element  124 , the fifth radiation element  125 , the first connection element  126 , the second connection element  127 , the third connection element  128 , and the fourth connection element  129  are all arranged in the same straight line, thereby forming a 1×5 antenna array. 
     In some embodiments, a central operation frequency of the first antenna array  120 , the second antenna array  130 , and the third antenna array  140  of the antenna system  100  (or  180 ) is substantially equal to 24 GHz. The element sizes of the antenna system  100  (or  180 ) may be as follows. The length E 1  of the first radiation element  121 , the length E 2  of the second radiation element  122 , the length E 3  of the third radiation element  123 , the length E 4  of the fourth radiation element  124 , and the length E 5  of the fifth radiation element  125  may be the same, and they may all be substantially equal to 0.5 wavelength (λ/2) of the central operation frequency of the antenna system  100  (or  180 ). The length E 6  of the first connection element  126 , the length E 7  of the second connection element  127 , the length E 8  of the third connection element  128 , and the length E 9  of the fourth connection element  129  may be the same, and they may all be substantially equal to 0.5 wavelength (λ/2) of the central operation frequency of the antenna system  100  (or  180 ). The width W 3  of the third radiation element  123  may be greater than the width W 2  of the second radiation element  122  and the width W 4  of the fourth radiation element  124 . The width W 2  of the second radiation element  122  and the width W 4  of the fourth radiation element  124  are both greater than the width W 1  of the first radiation element  121  and the width W 5  of the fifth radiation element  125  (i.e., W 3 &gt;W 2 =W 4 &gt;W 1 =W 5 ). The above ranges of element sizes are calculated and obtained according to many experiment results, and they help to optimize the operation bandwidth and impedance matching of the first antenna array  120 , the second antenna array  130 , and the third antenna array  140 . 
       FIG. 5A  is a diagram of a practical layout of an antenna system  500  according to an embodiment of the invention. In the embodiment of  FIG. 5A , the antenna system  500  includes a power divider  510 , a first antenna array  520 , a second antenna array  530 , a third antenna array  540 , a delay device  550 , a first switch element  560 , and a second switch element  570 , and their structures and functions have been described in the embodiment of  FIG. 1A . The aforementioned elements of the antenna system  500  may all be disposed on an upper surface of a dielectric substrate  505 , and a ground plane may be disposed on a lower surface of the dielectric substrate  505  (not shown). A dielectric constant of the dielectric substrate  505  may be about 3.85. The thickness of the dielectric substrate  505  (i.e., the distance between the upper surface and the lower surface) may be about 10 mil. Other features of the antenna system  500  of  FIG. 5A  are similar to those of the antenna system  100  of  FIG. 1A . Accordingly, the two embodiments can achieve similar levels of performance. 
       FIG. 5B  is a diagram of a practical layout of an antenna system  580  according to another embodiment of the invention. In the embodiment of  FIG. 5B , the antenna system  580  also includes a power divider  510 , a first antenna array  520 , a second antenna array  530 , a third antenna array  540 , a delay device  550 , a first switch element  560 , and a second switch element  570 , and their structures and functions have been described in the embodiment of  FIG. 1B . It should be noted that the first antenna array  520 , the second antenna array  530 , and the third antenna array  540  of  FIG. 5B  are aligned with each other. The distance DF 1  between the first antenna array  520  and the second antenna array  530  may be substantially equal to the distance DF 2  between the second antenna array  530  and the third antenna array  540 . For example, each of the distance DF 1  and the distance DF 2  may be substantially equal to 0.5 wavelength (λ/2) of the central operation frequency of the antenna system  580 . In addition, the antenna system  580  may further include a bending transmission line  585  coupled to the second antenna array  530 . The bending transmission line  585  is configured to equalize the effective feeding lengths of the first antenna array  520 , the second antenna array  530 , and the third antenna array  540 . Other features of the antenna system  580  of  FIG. 5B  are similar to those of the antenna system  180  of  FIG. 1B . Accordingly, the two embodiments can achieve similar levels of performance. 
       FIG. 6A  is a radiation pattern of the antenna system  580  operating in the first mode according to an embodiment of the invention (which may be measured on the YZ-plane). According to the measurement of  FIG. 6A , in the first mode, the first radiation pattern of the antenna system  580  merely includes a single main beam  610 , so as to provide relatively high antenna gain.  FIG. 6B  is a radiation pattern of the antenna system  580  operating in the second mode according to an embodiment of the invention (which may be measured on the YZ-plane). According to the measurement of  FIG. 6B , in the second mode, the second radiation pattern of the antenna system  580  includes two different main beams  620  and  630 , so as to provide relatively large beam widths. It should be understood that another antenna system  500  has a similar measurement result to that of  FIG. 6A  and  FIG. 6B  and is not illustrated again herein. 
     The invention proposes a novel antenna system including a plurality of antenna arrays and a plurality of switch elements, which are integrated with each other so as to save the design space of the antenna system. Generally, the invention has at least the advantages of adjustable radiation pattern, small size, high gain, low complexity, and low manufacturing cost, and therefore it is suitable for application in a variety of communication devices. 
     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 to meet different requirements. It should be understood that the antenna system of the invention is not limited to the configurations of  FIGS. 1-6 . The invention may include any one or more features of any one or more embodiments of  FIGS. 1-6 . In other words, not all of the features displayed in the figures should be implemented in the antenna system 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. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the invention. It is intended that the standard and examples be considered as exemplary only, with the true scope of the disclosed embodiments being indicated by the following claims and their equivalents.