Abstract:
A micro-strip antenna includes an L-shaped coupler, a set of micro-strip antennas, and an L-shaped band-stop filter. The set of micro-strip antennas includes at least one rectangular micro-strip antenna unit and a micro-strip line. The rectangular micro-strip antenna unit is coupled to the micro-strip line. The micro-strip line is coupled to the first end of the coupler. The band-stop filter is disposed along a corner of the rectangular micro-strip antenna unit, and is disposed between the antenna unit and the coupler without being physically connected to the antenna unit and the coupler. The width, length, and position of the L-shaped band-stop filter can be determined for the specific band-stop frequency and to optimize its coupling extent with the L-shaped coupler.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a micro-strip antenna, and more particularly, to a micro-strip antenna with an L-shaped band-stop filter. 
         [0003]    2. Description of the Prior Art 
         [0004]    In 1953, the concept of utilizing micro-strip line antennas to transmit radio frequency signals was developed but not widely used because the micro-strip line antennas still had various defects. When a Printed Circuit Board (PCB), microwave techniques, and many kinds of low-attenuating media materials were developed, the use of micro-strip antennas became more practical. The advantages of micro-strip antennas include light-weight, small size, low cost, easy-production, and ease of attachment to any surface that is integrated with a monolithic microwave integrated circuit. In recent years, as mobile communication and personal communication became popular and well developed, micro-strip antennas have been frequently used. 
         [0005]    In general, cellular phone size needs to be small; therefore available space for a micro-strip antenna is limited and increases design complexity. Since the design of the micro-strip antenna determines the communication quality of the cellular phone, the increased complexity for making a small micro-strip antenna has become a big challenge to the designer of the micro-strip antenna. 
         [0006]    U.S. Pat. No. 4,180,817 provides a structure with micro-strip antennas connected in series and in parallel. However, such a structure forms a long current path, which will generate parasitic low frequency resonance. Thus, an additional band-stop filter is needed for suppressing this parasitic low frequency resonance. In U.S. Pat. Nos. 6,856,290, 7,009,564, 7,109,929, and 7,138,949, different band-stop filters are provided to improve the quality of micro-strip antennas. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention provides a micro-strip antenna with an L-shaped band-stop filter. The micro-strip antenna comprises a first L-shaped coupler, a first micro-strip antenna row, and a first L-shaped band-stop filter. The first L-shaped coupler has a first end and a second end, where the second end of the first L-shaped coupler is for transmitting or receiving a signal. The first micro-strip antenna row comprises at least a first rectangular micro-strip antenna unit and a micro-strip line, where the first rectangular micro-strip antenna unit is coupled to the first micro-strip line, and the first micro-strip line is coupled to the first end of the first L-shaped coupler. The first L-shaped band-stop filter is disposed between the first rectangular micro-strip antenna unit and the first L-shaped coupler at a predetermined distance, at a corner of the first rectangular micro-strip antenna unit closest to the first L-shaped coupler. 
         [0008]    The present invention further provides a micro-strip antenna with an L-shaped band-stop filter. The micro-strip antenna comprises a first T-shaped coupler, a first micro-strip antenna row, a second micro-strip antenna row, a first L-shaped band-stop filter, and a second L-shaped band-stop filter. The first T-shaped coupler includes a first end, a second end, and a third end, where the third end of the first T-shaped coupler is for transmitting or receiving a signal. The first micro-strip antenna row comprises at least a first rectangular micro-strip antenna unit and a first micro-strip line, where the first rectangular micro-strip antenna unit is coupled to the first micro-strip line, and the first micro-strip line is coupled to the first end of the first T-shaped coupler. The second micro-strip antenna row comprises at least a second rectangular micro-strip antenna unit and a second micro-strip line, where the second rectangular micro-strip antenna unit is coupled to the second micro-strip line, and the second micro-strip line is coupled to the second end of the first T-shaped coupler. The first L-shaped band-stop filter is disposed between the first rectangular micro-strip antenna unit and the first T-shaped coupler at a first predetermined distance, at a corner of the first rectangular micro-strip antenna unit closest to the first T-shaped coupler. The second L-shaped band-stop filter is disposed between the second rectangular micro-strip antenna unit and the first T-shaped coupler at a second predetermined distance, at a corner of the second rectangular micro-strip antenna unit closest to the first T-shaped coupler. 
         [0009]    The present invention further provides a micro-strip antenna with an L-shaped band-stop filter. The micro-strip antenna comprises M-stage T-shaped couplers, each T-shaped coupler comprising a first end, a second end, and a third end. A number of the K th -stage T-shaped couplers is 2 K , and the third end of each K th -stage T-shaped coupler is coupled to the first end or the second end of a corresponding (K−1) th -stage T-shaped coupler, and the third end of the 0 th -stage T-shaped coupler is for transmitting or receiving a signal. The micro-strip antenna further comprises 2 M  first micro-strip antenna rows, 2 M  second micro-strip antenna rows, 2 M  first L-shaped band-stop filters, and 2 M  second L-shaped band-stop filters. Each first micro-strip antenna row comprises N first micro-strip lines. Each first rectangular antenna unit is coupled to a corresponding first micro-strip line and one of the N first micro-strip lines is coupled to the first end of a corresponding M th -stage T-shaped coupler. Each first micro-strip antenna row also comprises N first rectangular antenna units. Each first rectangular antenna unit is coupled to a corresponding first micro-strip line. Each second micro-strip antenna row comprises N second micro-strip lines and one of the N second micro-strip lines is coupled to the second end of a corresponding M th -stage T-shaped coupler. Each second micro-strip antenna row also comprises N second rectangular antenna units, each second rectangular antenna unit being coupled to a corresponding second micro-strip line. Each first L-shaped band-stop filter is disposed between the first rectangular micro-strip antenna unit and the first end of the M th -stage T-shaped coupler at a first predetermined distance, along a corner of one of the first rectangular micro-strip antenna units closest to a corresponding M th -stage T-shaped coupler. Each second L-shaped band-stop filter is disposed between the first rectangular micro-strip antenna unit and the first end of the M th -stage T-shaped coupler at a second predetermined distance, along a corner of one of the second rectangular micro-strip antenna units closest to a corresponding M th -stage T-shaped coupler. 
         [0010]    These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a diagram illustrating a micro-strip antenna with an L-shaped band-stop filter according to a first embodiment of the present invention. 
           [0012]      FIG. 2  is a diagram illustrating a micro-strip antenna with an L-shaped band-stop filter according to a second embodiment of the present invention. 
           [0013]      FIG. 3  is a diagram illustrating a micro-strip antenna with an L-shaped band-stop filter according to a third embodiment of the present invention. 
           [0014]      FIG. 4  is a diagram illustrating a micro-strip antenna with an L-shaped band-stop filter according to a fourth embodiment of the present invention. 
           [0015]      FIG. 5  is a diagram illustrating a micro-strip antenna with an L-shaped band-stop filter according to a fifth embodiment of the present invention. 
           [0016]      FIG. 6  is a diagram illustrating the micro-strip antenna of the present invention. 
           [0017]      FIG. 7  is a diagram illustrating measurement of a radiation pattern of the micro-strip antenna of the present invention at 5.8 GHz. 
           [0018]      FIG. 8  is a diagram illustrating measurement of a reflection loss of the micro-strip antenna of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    Please refer to  FIG. 1 .  FIG. 1  is a diagram illustrating a micro-strip antenna  100  with an L-shaped band-stop filter according to a first embodiment of the present invention. As shown in  FIG. 1 , the micro-strip antenna  100  comprises an L-shaped coupler  110 , a micro-strip antenna row  120 , and an L-shaped band-stop filter  130 . The L-shaped coupler  110  comprises a first end and a second end. The first end of the L-shaped coupler  110  is coupled to the micro-strip antenna row  120 . The second end of the L-shaped coupler  110  is for receiving or transmitting a signal. The micro-strip antenna row  120  comprises at least one rectangular micro-strip antenna unit  122  and a micro-strip line  121 . The micro-strip line  121  is coupled between the first end of the L-shaped coupler  110  and the rectangular micro-strip antenna unit  122 . The L-shaped band-stop filter  130  is disposed at a corner of the rectangular micro-strip antenna unit  122  that is closest to the L-shaped coupler  110 . The L-shaped band-stop filter  130  is disposed at a distance from the L-shaped coupler  110 . The L-shaped band-stop filter  130  is disposed at a distance from the rectangular micro-strip antenna unit  122 . The L-shaped band-stop filter  130  is not physically connected to the L-shaped band-stop filter  130  or the rectangular micro-strip antenna unit  122 . 
         [0020]    The L-shaped band-stop filter  130  is designed in the structure of the L-shaped coupler to suppress the parasitic low frequency resonant state. The length D of the L-shaped band-stop filter  130  is equal to N multiplied by a half wavelength of a frequency stopped by the L-shaped band-stop filter  130 , where N is an integer. The L-shaped band-stop filter  130  does not affect impedance matching between the L-shaped coupler and the antenna, nor does it affect the radiation character of the antenna array. The L-shaped band-stop filter  130  can be integrated into the structure of the antenna without requiring additional layout space. The length D of the L-shaped band-stop filter  130  can be adjusted according to length of the feeding line. Additionally, the width and position of the L-shaped band-stop filter  130  can be adjusted to best fit the L-shaped coupler  110 . 
         [0021]    Please refer to  FIG. 2 .  FIG. 2  is a diagram illustrating a micro-strip antenna  200  with an L-shaped band-stop filter according to a second embodiment of the present invention. As shown in  FIG. 2 , the micro-strip antenna  200  comprises an L-shaped coupler  210 , a micro-strip antenna row  220 , an L-shaped band-stop filter  230 , and a T-shaped coupler  20 . The micro-strip antenna also includes the components in  FIG. 1  (an L-shaped coupler  110 , a micro-strip antenna row  120 , and an L-shaped band-stop filter  130 ). The T-shaped coupler  20  comprises a first end, a second end, and a third end. The first end of the T-shaped coupler  20  is coupled to the L-shaped coupler  110 , the second end of the T-shaped coupler  20  is coupled to the L-shaped coupler  210 , and the third end of the T-shaped coupler  20  is for receiving or transmitting a signal. Components mentioned in  FIG. 1  will not be described again because the components are the same. The second end of the L-shaped coupler  110  is coupled to the first end of the T-shaped coupler  20 . The L-shaped coupler  210  comprises a first end and a second end. The first end of the L-shaped coupler  210  is coupled to the micro-strip antenna row  220 . The second end of the L-shaped coupler  210  is coupled to the second end of the T-shaped coupler  20 . The micro-strip antenna row  220  comprises at least one rectangular micro-strip antenna unit  222  and a micro-strip line  221 . The micro-strip antenna row can further comprise a plurality of rectangular micro-strip antenna unit coupled in series, however, as shown in  FIG. 2 . The micro-strip line  221  is coupled between the first end of the L-shaped coupler  210  and the rectangular micro-strip antenna unit  222 . The L-shaped band-stop filter  230  is disposed at a corner of the rectangular micro-strip antenna unit  222  closest to the L-shaped coupler  210 . The L-shaped band-stop filter  230  is disposed at a distance from the rectangular micro-strip antenna unit  222 . The L-shaped band-stop filter  230  is disposed at a distance from the L-shaped coupler  210 . 
         [0022]    The L-shaped band-stop filter  230  is designed in the structure of the L-shaped coupler to suppress the parasitic low frequency resonant state. The length D of the L-shaped band-stop filter  230  is equal to N multiplied by a half wavelength of a frequency stopped by the L-shaped band-stop filter  230 , where N is an integer. The L-shaped band-stop filter  230  does not affect the impedance match between the L-shaped coupler and the antenna, nor does it affect the radiation character of the antenna array. The L-shaped band-stop filter  230  can be integrated in the structure of the antenna without requiring additional layout space. The length D of the L-shaped band-stop filter  230  can be adjusted according to length of the feeding line. 
         [0023]    Please refer to  FIG. 3 .  FIG. 3  is a diagram illustrating a micro-strip antenna  300  with an L-shaped band-stop filter according to a third embodiment of the present invention. As shown in  FIG. 3 , the micro-strip  300  further comprises a T-shaped coupler  310 , two micro-strip antenna rows  320  and  340 , and two L-shaped band-stop filters  331  and  332 , and a T-shaped coupler  30 . The micro-strip  300  also comprises the L-shaped coupler  110 , the micro-strip antenna row  120 , and the L-shaped band-stop filter  130  shown in  FIG. 1 . The T-shaped coupler  30  comprises a first end, a second end, and a third end. The first end of the T-shaped coupler  30  is coupled to the L-shaped coupler  110 . The second end of the T-shaped coupler  30  is coupled to the third end of the T-shaped coupler  310 . The third end of the T-shaped coupler  30  is for receiving or transmitting a signal. Components mentioned in  FIG. 1  will not be described again because the components are the same. The T-shaped coupler  310  comprises a first end, a second end, and a third end. The first end of the T-shaped coupler  310  is coupled to the micro-strip antenna row  320 . The second end of the T-shaped coupler  310  is coupled to the micro-strip antenna row  340 . The third end of the T-shaped coupler  310  is coupled to the second end of the T-shaped coupler  30 . The micro-strip antenna row  320  comprises at least one rectangular micro-strip antenna unit  322  and a micro-strip line  321 . The micro-strip antenna row can further comprise a plurality of rectangular micro-strip antenna units coupled in series as shown in  FIG. 3 . The micro-strip line  321  is coupled between the second end of the T-shaped coupler  310  and the rectangular micro-strip antenna unit  342 . The L-shaped band-stop filter  331  is disposed at a corner of the rectangular micro-strip antenna unit  322  closest to the T-shaped coupler  310 . The L-shaped band-stop filter  331  is disposed at a distance from the rectangular micro-strip antenna unit  342 . The L-shaped band-stop filter  331  is disposed at a distance from the T-shaped coupler  310 . 
         [0024]    The L-shaped band-stop filters  331  and  332  are designed in the structure of the T-shaped coupler  310  to suppress a parasitic low frequency resonant state. The length D of the L-shaped band-stop filters  331  and  332  are equal to N multiplied by a half wavelength of a frequency stopped by the L-shaped band-stop filters  331  and  332 , where N is an integer. The L-shaped band-stop filters  331  and  332  do not affect the impedance match between the T-shaped coupler  310  and the antenna, and also do not affect the radiation character of the antenna array. The L-shaped band-stop filters  331  and  332  can be integrated in the structure of the antenna without requiring additional layout space. The length D of the L-shaped band-stop filters  331  and  332  can be adjusted according to length of the feeding line. 
         [0025]    Please refer to  FIG. 4 .  FIG. 4  is a diagram illustrating a micro-strip antenna  400  with an L-shaped band-stop filter according to a fourth embodiment of the present invention. As shown in  FIG. 4 , the micro-strip  400  comprises a T-shaped coupler  310 , two micro-strip antenna rows  320  and  340 , and two L-shaped band-stop filters  331  and  332 . The T-shaped coupler  310  comprises a first end, a second end, and a third end. The first end of the T-shaped coupler  310  is coupled to the micro-strip antenna  320 . The second end of the T-shaped coupler  310  is coupled to the micro-strip antenna row  340 . The third end of the T-shaped coupler  310  is for receiving or transmitting a signal. The micro-strip antenna row  320  comprises at least one rectangular micro-strip antenna unit  322  and a micro-strip line  321 . The micro-strip antenna row can further comprise a plurality of rectangular micro-strip antenna units coupled in series as shown in  FIG. 4 . The micro-strip line  321  is coupled between the first end of the T-shaped coupler  310  and the rectangular micro-strip antenna unit  342 . The L-shaped band-stop filter  332  is disposed at a corner of the rectangular micro-strip antenna unit  322  closest to the T-shaped coupler  310 . The L-shaped band-stop filter  331  is disposed at a distance from the rectangular micro-strip antenna unit  342 . The L-shaped band-stop filter  332  is disposed at a distance from the T-shaped coupler  310 . 
         [0026]    The L-shaped band-stop filters  331  and  332  are designed in the structure of the T-shaped coupler  310  to suppress a parasitic low frequency resonant state. The length D of the L-shaped band-stop filters  331  and  332  are equal to N multiplied by a half wavelength of a frequency stopped by the L-shaped band-stop filters  331  and  332 , where N is an integer. The L-shaped band-stop filters  331  and  332  do not affect the impedance match between the T-shaped coupler  310  and the antenna, and also do not affect the radiation character of the antenna array. The L-shaped band-stop filters  331  and  332  can be integrated in the structure of the antenna without requiring additional layout space. The length D of the L-shaped band-stop filters  331  and  332  can be adjusted according to length of the feeding line. 
         [0027]    Please refer to  FIG. 5 .  FIG. 5  is a diagram illustrating a micro-strip antenna  500  with an L-shaped band-stop filter according to a fifth embodiment of the present invention. As shown in  FIG. 5 , the micro-strip antenna  500  comprises two micro-strip antennas  400  coupled through the T-shaped coupler  50  that receive or transmit signals using the same feeding line. The description of the micro-strip antenna  400  is omitted because it is already mentioned above. The fifth embodiment shows that the present invention comprises a plurality of parallel-connected rows of serial-connected micro-strip antenna units as well as a plurality of series-connected micro-strip antenna units. A micro-strip antenna constructed by a micro-strip antenna array is formed. The micro-strip antenna  500  has reduced noise because of the addition of the L-shaped band-stop filter of the present invention. 
         [0028]    Please refer to  FIG. 6 .  FIG. 6  is a diagram illustrating the micro-strip antenna  600  of the present invention. As shown in  FIG. 6 , the micro-strip antenna  600  comprises two micro-strip antenna rows  611  and  612 , a pair of L-shaped band-stop filters  613 , and a T-shaped coupler  614 . The micro-strip antenna row  611  comprises two rectangular micro-strip antenna units  6111  and  6113 , and two micro-strip lines  6112  and  6114 . The lengths of the rectangular micro-strip antenna units  6111  and  6113  are both equal to 12.5 millimeters, and the widths of the rectangular micro-strip antenna units  6111  and  6113  are both equal to 12.5 millimeters. In this embodiment, the rectangular micro-strip antenna units  6111  and  6113  can be any rectangular form. The length of the micro-strip line  6112  is 4 millimeters. The width of the micro-strip line  6112  is 0.7 millimeters. The length of the micro-strip line  6114  is 1.5 millimeters. The width of the micro-strip line  6114  is 0.7 millimeters. The micro-strip line  6114  is coupled to the rectangular micro-strip antenna unit  6113 . The micro-strip antenna row  612  comprises two rectangular micro-strip antenna units  6121  and  6123 , and two micro-strip lines  6122  and  6124 . The lengths of the rectangular micro-strip antenna units  6121  and  6123  are both equal to 12.5 millimeters, and the widths of the rectangular micro-strip antenna units  6121  and  6123  are both equal to 12.5 millimeters. In this embodiment, the rectangular micro-strip antenna units  6121  and  6123  can be any rectangular form. The length of the micro-strip line  6122  is 4 millimeters. The width of the micro-strip line  6122  is 0.7 millimeters. The length of the micro-strip line  6124  is 1.5 millimeters. The width of the micro-strip line  6124  is 0.7 millimeters. The micro-strip line  6124  is coupled to the rectangular micro-strip antenna unit  6123 . The distance between the micro-strip antenna units  6111  and  6121  is 4 millimeters. The distance between the micro-strip antenna units  6113  and  6123  is 4 millimeters. The L-shaped band-stop filter  6137  comprises a first vertical unit  6131 , a third isosceles triangle  6132 , and a third horizontal unit  6133 . The width of the first vertical unit  6131  is 0.3 millimeters. The length of the first vertical unit  6131  is 8.2 millimeters. The isosceles triangle  6132  is coupled between the first vertical unit  6131  and the third horizontal unit  6133 . The base of the isosceles triangle  6132  is 0.3 millimeters. The height of the isosceles triangle  6132  is 0.3 millimeters. The width of the third horizontal unit  6133  is 0.3 millimeters. The length of the third horizontal unit  6133  is 7.15 millimeters. The distance between the third horizontal unit  6133  and the micro-strip line  6114  is 0.3 millimeters. The distance between the third horizontal unit  6133  and the first horizontal unit  6142  of the T-shaped coupler  614  is 0.3 millimeters. The L-shaped band-stop filter  6138  comprises a second vertical unit  6134 , a fourth isosceles triangle  6135 , and a fourth horizontal unit  6136 . The width of the second vertical unit  6134  is 0.3 millimeters. The length of the second vertical unit  6134  is 8.2 millimeters. The isosceles triangle  6135  is coupled between the second vertical unit  6134  and the fourth horizontal unit  6136 . The base of the fourth isosceles triangle  6135  is 0.3 millimeters. The height of the fourth isosceles triangle  6135  is 0.3 millimeters. The width of the fourth horizontal unit  6136  is 0.3 millimeters. The length of the fourth horizontal unit  6136  is 7.15 millimeters. The distance between the fourth horizontal unit  6136  and the fourth micro-strip line  6124  is 0.3 millimeters. The distance between the fourth horizontal unit  6136  and the second horizontal unit  6145  of the T-shaped coupler  614  is 0.3 millimeters. The T-shaped coupler  614  comprises a first isosceles triangle  6141 , a first horizontal unit  6142 , a first right triangle  6143 , a second right triangle  6144 , a second horizontal unit  6145 , a second isosceles triangle  6146 , and a trunk  6147 . The first isosceles triangle  6141  is coupled to the second micro-strip line  6114 . The base of the first isosceles triangle  6141  is 0.7 millimeters. The height of the first isosceles triangle  6141  is 0.7 millimeters. The first horizontal unit  6142  is coupled to the first isosceles triangle  6141 . The width of the first horizontal unit  6142  is 0.7 millimeters. The length of the first horizontal unit  6142  is 6.4 millimeters. The first right triangle  6143  is coupled to the first horizontal unit  6142 . The base of the first right triangle  6143  is 0.7 millimeters. The height of the first right triangle  6143  is 1.5 millimeters. The second right triangle  6144  is coupled to the second horizontal unit  6145 . The base of the second right triangle  6144  is 0.7 millimeters. The height of the second right triangle  6144  is 1.5 millimeters. The second horizontal unit  6145  is coupled to the second isosceles triangle  6146 . The width of the second horizontal unit  6145  is 0.7 millimeters. The length of the second horizontal unit  6145  is 6.4 millimeters. The second isosceles triangle  6146  is coupled to the micro-strip line  6124 . The base of the second isosceles triangle  6146  is 0.7 millimeters. The height of the second isosceles triangle  6146  is 0.7 millimeters. The trunk  6147  is coupled to the first right triangle  6143  and the second right triangle  6144 . The width of the trunk  6147  is 3 millimeters. The length of the trunk  6147  is 2.9 millimeters. The trunk  6147  is for transmitting or receiving the signal. 
         [0029]    The micro-strip antenna  600  is made up of 2 rows of 2 serial-connected micro-strip antenna units, i.e. 4 rectangular micro-strip units  6111 ,  6113 ,  6121 , and  6123 . All of the rectangular micro-strip units  6111 ,  6113 ,  6121 , and  6123  have a resonant frequency of 5.8 GHz. The impedances of the micro-strip lines  6112  and  6122  are 100 ohms. The micro-strip units  6111  and  6113  are coupled through the micro-strip line  6112 . The micro-strip units  6121  and  6123  are coupled through the micro-strip line  6122 . The input impedances of the micro-strip antenna rows  611  and  612  are 100 ohms. The input impedance of the trunk  6147  is 50 ohms. The trunk  6147  serves as the feeding line. The T-shaped coupler  614  serves as the power distributor and distributes the signals to the micro-strip rows  611  and  612 . The structure of the micro-strip antenna  600  causes 0 phase difference in each micro-strip antenna unit. Therefore, the array factor generates constructive interference in the direction of θ=ψ=0°, which is the same direction as the maximum gain of a single micro-strip antenna. Consequently, the total gain of the micro-strip antenna  600  is raised. Compared to the micro-strip antenna in the prior art, the feeding structure of the micro-strip antenna  600  is omni-directional and uses less layout space. The length of the feeding line affects parasitic frequency and omni-directionality of the antenna. The up/down movements of the four rectangular micro-strip units affect the feeding-in phase of the antenna component and the omni-directionality of the antenna. In this embodiment, the phase difference is 0. The left/right movement of the feeding line affects the impedance match of the antenna. Furthermore, the corner of the feeding line is designed to have an appropriate angle for avoiding electric charge accumulation and mismatching effect. 
         [0030]    The substrate of the micro-strip antenna  600  adopts material having permittivity of ∈r=4.2, width of 1.6 millimeters, tanδ=0.022, and metal width of 35 micrometers. The total layout space of the micro-strip antenna  600  is 34.1×29 square millimeters. The size of the ground of the micro-strip antenna  600  is 40×40 square millimeters. The metal layer in the back of the substrate of the micro-strip antenna  600  can be shorted to ground. 
         [0031]    Please refer to  FIG. 7 .  FIG. 7  is a diagram illustrating the measurement of the radiation pattern of the micro-strip antenna  600  at 5.8 GHz. The XY plane and the YZ plane are both broadside radiation patterns. The maximum gain of the micro-strip antenna  600  is 9.92 dB isotropic (dBi). 
         [0032]    Please refer to  FIG. 8 .  FIG. 8  is a diagram illustrating measurement of the reflection loss of the micro-strip antenna  600 . The dashed line designates the micro-strip antenna  600  without L-shaped band-stop filters. The solid line designates the micro-strip antenna  600  with L-shaped band-stop filters. When the micro-strip antenna  600  has no L-shaped band-stop filters, parasitic resonance is generated at a frequency between 5.15 GHz˜5.28 GHz. The L-shaped band-stop filter effectively suppresses the parasitic resonance without affecting the original resonant frequency of the antenna. The reflection loss of the micro-strip antenna  600  is lower than −10 dB at a receiving and transmitting frequency between 5.7˜5.95 GHz. 
         [0033]    Compared to a structure that only has a parallel-connected array or a structure that only has a serial-connected array, the structure of the micro-strip antenna  600  (2×2 array) reduces the length of the feeding line and also meets the demand of 0 phase difference between antenna components. The L-shaped band-stop filter filters out the noise from non-operating frequencies, and does not increase layout space, or affect the radiation of the micro-strip antenna at the frequency of 5.8 GHz. 
         [0034]    Additionally, the receiving and the transmitting frequency of the micro-strip antenna of the present invention can be set to be between 5.7˜5.95 GHz. 
         [0035]    Additionally, the structure of the micro-strip antenna of the present invention can be formed by a metal layer attached to a dielectric substrate. The metal ground is further attached on the opposite side of the dielectric substrate. The size of the metal ground must be bigger than or equal to the structure of the micro-strip antenna of the present invention. 
         [0036]    Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention.