Patent Publication Number: US-9905929-B2

Title: Microstrip antenna transceiver

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention provides a microstrip antenna transceiver which is capable of switching polarizations. 
     2. Description of the Prior Art 
     Satellite communication has advantages of huge coverage and no interference caused by ground environments, and is widely used in military applications, detection and commercial communications services such as satellite navigation, a satellite voice broadcast system or a satellite television broadcast system. Nowadays, many electronic devices, such as smart phones, tablet personal computers, and so on can receive satellite signals via an external antenna. In general, the frequency of satellite signals ranges from 1.466 GHz to 1.472 GHz and two orthogonal signals are provided within the band at the same time, wherein one of the orthogonal signals is a left-handed polarized signal and the other is a right-handed polarized signal. Therefore, a left-handed polarized antenna module and a right-handed polarized antenna module are required to receive the two orthogonal signals. However, practically, an electronic device does not handle the two orthogonal signals at the same time and only selects one. Moreover, two independent antenna modules occupy much space and increase the cost, so the left-handed polarized antenna module and the right-handed polarized antenna module are preferably combined to one antenna module. 
     A conventional antenna transceiver comprises two switch elements, a hybrid circuit and a patch antenna. The hybrid circuit comprises two input transmission ports and two output transmission ports. When the two switch elements are not conducted simultaneously (i.e., only one switch element is turned on at a time) and control a signal received to enter the hybrid circuit via only one of the input transmission ports, the hybrid circuit equally partitions the signal into two transmission signals with a phase difference of 90 degrees, and then transmits the two transmission signals to the patch antenna through the two output transmission ports, respectively. Then, the patch antenna generates a vertically polarized signal and a horizontally polarized signal and radiates the vertically polarized signal and the horizontally polarized signal to the air. Since the phases of the two transmission signals have a 90-degree phase difference, a left-handed polarized antenna pattern or a right-handed polarized antenna pattern can be formed. Two feed-in points of the patch antenna are connected to two output transmission ports respectively; therefore, vertically polarized and horizontally polarized electromagnetic fields are generated after the two transmission signals equally partitioned from the signal enter the patch antenna. Besides, since the patch antenna is vertically and horizontally symmetric, energy of the vertically polarized signal and the horizontally polarized signal are not mutually affected. 
     As seen above, the conventional antenna transceiver has high isolation for two orthogonal signals. However, the length and width of the hybrid circuit need to be ¼ wavelength in order to perform the hybrid circuit, so that the hybrid circuit requires large plate area and the cost is increased for the present satellite signals of low frequency. Therefore, how to reduce the cost of the antenna and handle the two orthogonal signals at the same time becomes a goal in the industry. 
     SUMMARY OF THE INVENTION 
     The present invention is related to a microstrip antenna transceiver, and more particularly, to a microstrip antenna transceiver which is capable of switching polarizations. 
     An embodiment of the present invention discloses a microstrip antenna transceiver with switchable polarizations, comprising a substrate comprising a first surface and a second surface; a first switch element disposed on the first surface of the substrate; a second switch element disposed on the first surface of the substrate; and an antenna module disposed on the second surface of the substrate comprising a radiation patch comprising a first pattern slot wherein a size and a displacement of the first pattern slot are related to a reflection phase of the first switch element and a reflection phase of the second switch element in order to generate a right-handed polarized signal or a left-handed polarized signal; a vertical polarization feed-in point; and a horizontal polarization feed-in point wherein the vertical polarization feed-in point and the horizontal polarization feed-in point are symmetric with respect to a symmetrical axis; a first microstrip line is electrically connected between the vertical polarization feed-in point and the first switch element; and a second microstrip line is electrically connected between the horizontal polarization feed-in point and the second switch element. 
     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 
         FIG. 1A  is a schematic diagram illustrating a top view of a front surface of a microstrip antenna transceiver according to an embodiment of the present invention. 
         FIG. 1B  is a schematic diagram illustrating a top view of a back surface of the microstrip antenna transceiver shown in  FIG. 1A . 
         FIG. 1C  is a cross-sectional view diagram of the microstrip antenna transceiver  10  taken along a cross-sectional line A-A′ in  FIG. 1A . 
         FIG. 2  is a schematic diagram illustrating antenna resonance simulation results of the microstrip antenna transceiver shown in  FIG. 1A  when the reflection phase of the switch elements is 180 degrees, 135 degrees, 90 degrees, 45 degrees, 0 degrees, −45 degrees, −90 degrees, and −135 degrees. 
         FIG. 3  to  FIG. 10  are schematic diagrams illustrating antenna pattern characteristic simulation results for the microstrip antenna transceiver shown in  FIG. 1A  operated at 1.469 GHz when the reflection phase of the switch elements is 180 degrees, 135 degrees, 90 degrees, 45 degrees, 0 degrees, −45 degrees, −90 degrees, and −135 degrees. 
         FIG. 11  is a schematic diagram illustrating a top view of a front surface of a microstrip antenna transceiver according to an embodiment of the present invention. 
         FIG. 12  is a schematic diagram illustrating a top view of a front surface of a microstrip antenna transceiver according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1A  is a schematic diagram illustrating a top view of a front surface of a microstrip antenna transceiver  10  according to an embodiment of the present invention.  FIG. 1B  is a schematic diagram illustrating a top view of a back surface of the microstrip antenna transceiver  10 .  FIG. 1C  is a cross-sectional view diagram of the microstrip antenna transceiver  10  taken along a cross-sectional line A-A′ in  FIG. 1A . The microstrip antenna transceiver  10  comprises a substrate  100 , a metal grounding plate  110 , an antenna module  120 , switch elements  136 ,  138 , microstrip lines  146  and  148 . The switch elements  136 ,  138  are disposed on one side of the substrate  100 , and the metal grounding plate  110  and the antenna module  120  are disposed on the other side of the substrate  100 . The metal grounding plate  110  is disposed between the antenna module  120  and the substrate  100 . The antenna module  120  comprises a dielectric layer  122 , a radiation patch  124 , a vertical polarization feed-in point  126  and a horizontal polarization feed-in point  128 . The dielectric layer  122  is utilized to electrically isolate the metal grounding plate  110  from the radiation patch  124 . The radiation patch  124  is the main radiating body by which electromagnetic waves resonate along a vertical direction X or a horizontal direction Y, such that a vertically polarized signal SV or a horizontally polarized signal SH radiates. The shape of the radiation patch  124  of the antenna module  120  is substantially conforming to a hexagon symmetric with respect to a symmetrical axis XS, and more precisely, is a quadrilateral with two opposite corners chamfered to form cutting corners CH 1  and CH 2  for controlling energy transformation between the vertically polarized signal SV and the horizontally polarized signal SH of the antenna module  120 . The radiation patch  124  comprises pattern slots SL 1 , SL 2  for adjusting the phase difference between the vertically polarized signal SV and the horizontally polarized signal SH to produce a right-handed polarized signal or a left-handed polarized signal. The pattern slots SL 1 , SL 2  are symmetric with respect to the symmetrical axis XS, and are disposed on the opposite sides of a line connecting the vertical polarization feed-in point  126  to the horizontal polarization feed-in point  128 , respectively. 
     The vertical polarization feed-in point  126  and the horizontal polarization feed-in point  128  are symmetric with respect to the symmetrical axis XS. The microstrip line  146  is electrically connected between the vertical polarization feed-in point  126  and the switch element  136  through an opening  106  of the substrate  100 , and thus transmits or receives the vertically polarized signal SV with the antenna module  120  controlled by the switch element  136 . The microstrip line  148  is electrically connected between the horizontal polarization feed-in point  128  and the switch element  138  through an opening  108  of the substrate  100 , and thus transmits or receives the horizontally polarized signal SH with the antenna module  120  controlled by the switch element  138 . The lengths of the microstrip lines  146 ,  148  are substantially the shortest distance from the substrate  100  to the vertical polarization feed-in point  126  or the horizontal polarization feed-in point  128 . Moreover, distances L 1 , L 2  of the microstrip lines  146 ,  148  from the switch elements  136 ,  138  to the openings  106 ,  108  are approximately zero—namely, the microstrip lines  146 ,  148  merely electrically connects one element to another without changing signal phase, thereby providing a relative small sized microstrip antenna transceiver  10 , reducing energy loss of the microstrip lines  146 ,  148 , improving antenna gain, and avoiding noise. 
     Briefly, the microstrip antenna transceiver  10  transmits or receives signals of different polarizations (i.e. left-handed polarized signals and right-handed polarized signals) by controlling the switch elements  136 ,  138 , such that the microstrip antenna transceiver  10  can handle signals of different polarizations by switching in order to save costs and in order to handle signals of different polarizations with the same one antenna transceiver. 
     Take a signal T to be transmitted for example. When the switch element  136  is conducted but the switch element  138  is off (i.e. the switch element  138  is not turned on), the signal T enters the microstrip antenna transceiver  10  from the switch element  136  and is fed to the vertical polarization feed-in point  126  via the microstrip line  146  so as to generate the vertically polarized signal SV in the antenna module  120  and radiate the vertically polarized signal SV to the air. However, since the radiation patch  124  has the cutting corners CH 1 , CH 2 , part of the signal T would be converted and be transmitted to the horizontal polarization feed-in point  128 , then reach the switch element  138  in the off status by way of the microstrip line  148 , then bounce back to the horizontal polarization feed-in point  128 , and finally be sent to the antenna module  120  to generate the horizontally polarized signal SH and to radiate the horizontally polarized signal SH to the air. Then, this produces a phase difference between the horizontally polarized signal SH and the vertically polarized signal SV, because the signal transmission paths are different, and because the phase changes when signals come across the pattern slots SL 1 , SL 2 . It is worth noting that, by adjusting the cutting corners CH 1 , CH 2  of the radiation patch  124  or the displacements  126 D,  128 D of the vertical polarization feed-in point  126  and the horizontal polarization feed-in point  128  with respect to a center C of the radiation patch  124 , the magnitude of the vertically polarized signal SV is substantially equal to that of the horizontally polarized signal SH; in addition, by adjusting sizes SL 1 _L, SL 1 _W, SL 2 _L, SL 2 _W of the pattern slots SL 1 , SL 2  and displacements SL 1 _D, SL 2 _D of the geometric centers of the pattern slots SL 1 , SL 2  with respect to the center C according to reflection phases of the switch element  136 ,  138 , the vertically polarized signal SV leads the horizontally polarized signal SH by 90 degrees (i.e., one quarter of a wavelength), such that the left-handed polarized antenna pattern can be created. In such a situation, the sizes SL 1 _L, SL 1 _W, SL 2 _L, SL 2 _W of the pattern slots SL 1 , SL 2  and the displacements SL 1 _D, SL 2 _D are related to the reflection phases of the switch element  136 ,  138 . 
     Similarly, when the switch element  138  is conducted but the switch element  136  is off, the signal T enters the microstrip antenna transceiver  10  from the switch element  138  and is fed to the horizontal polarization feed-in point  128  via the microstrip line  148  so as to generate the horizontally polarized signal SH in the antenna module  120  and radiate the horizontally polarized signal SH to the air. However, since the radiation patch  124  has the cutting corners CH 1 , CH 2 , part of the signal T would be converted and be transmitted to the vertical polarization feed-in point  126 , then reach the switch element  136  in the off status by way of the microstrip line  146 , then bounce back to the vertical polarization feed-in point  126 , and finally be sent to the antenna module  120  to generate the vertically polarized signal SV and to radiate the vertically polarized signal SV to the air. Then, this produces a phase difference between the vertically polarized signal SV and the horizontally polarized signal SH, because the signal transmission paths are different, and because the phase changes when signals come across the pattern slots SL 1 , SL 2 . By adjusting the cutting corners CH 1 , CH 2  of the radiation patch  124  or the displacements  126 D,  128 D of the vertical polarization feed-in point  126  and the horizontal polarization feed-in point  128  with respect to the center C, the magnitude of the vertically polarized signal SV is substantially equal to that of the horizontally polarized signal SH; in addition, by adjusting the sizes SL 1 _L, SL 1 _W, SL 2 _L, SL 2 _W of the pattern slots SL 1 , SL 2  and the displacements SL 1 _D, SL 2 _D of the geometric centers of the pattern slots SL 1 , SL 2  with respect to the center C according to the reflection phases of the switch element  136 ,  138 , the vertically polarized signal SV lags the horizontally polarized signal SH by 90 degrees, such that the right-handed polarized antenna pattern can be created. 
     As set forth above, the feed-in points for signals in the microstrip antenna transceiver  10  of the present invention can be appropriately modified to handle the signals of different polarizations. Moreover, as a receiver, the microstrip antenna transceiver  10  can also transmit the left-handed polarized signal or the right-handed polarized signal received from the antenna module  120  to a backend circuit module (which is not illustrated in  FIG. 1A  to  FIG. 1C ) by controlling the switch element  136  and the switch element  138  to perform signal processing. Besides, in comparison with the radiation operations, the switch element  136  and the switch element  138  need to rotate 180 degrees to conform the signal transmission directions when the receiving operations are executed. 
     Please note that the microstrip antenna transceiver  10  is an exemplary embodiment of the invention, and those skilled in the art can make alternations and modifications accordingly. For example, according to the reflection phases of the switch elements  136 ,  138  (e.g., from −180 degrees to 180 degrees), the microstrip antenna transceiver  10  is properly designed to obtain the desired electromagnetic field solution. Please refer to Table 1, Table 2 and  FIG. 2  to  FIG. 10 .  FIG. 2  is a schematic diagram illustrating antenna resonance simulation results of the microstrip antenna transceiver  10  when the reflection phase of the switch elements  136 ,  138  is 180 degrees, 135 degrees, 90 degrees, 45 degrees, 0 degrees, −45 degrees, −90 degrees, and −135 degrees.  FIG. 3  to  FIG. 10  are schematic diagrams illustrating antenna pattern characteristic simulation results for the microstrip antenna transceiver  10  operated at 1.469 GHz when the reflection phase of the switch elements  136 ,  138  is 180 degrees, 135 degrees, 90 degrees, 45 degrees, 0 degrees, −45 degrees, −90 degrees, and −135 degrees. In  FIG. 3  to  FIG. 10 , common polarization radiation pattern of the microstrip antenna transceiver  10  at 0° cut plane is presented by thick solid line, common polarization radiation pattern of the microstrip antenna transceiver  10  at 90° cut plane is presented by thick dashed line, cross polarization radiation pattern of the microstrip antenna transceiver  10  at 0° cut plane is presented by thin solid line, and cross polarization radiation pattern of the microstrip antenna transceiver  10  at 90° cut plane is presented by thin dashed line. Table 1 is an antenna characteristic table for the microstrip antenna transceiver  10  with different sizes and different reflection phases of the switch elements  136 ,  138  shown in  FIG. 3  to  FIG. 6 . Table 2 is an antenna characteristic table for the microstrip antenna transceiver  10  with different sizes and different reflection phases of the switch elements  136 ,  138  shown in  FIG. 7  to  FIG. 10 . As can be seen from  FIG. 2 , Table 1 and Table 2, when the reflection phase of the switch elements  136 ,  138  in the off status is 180 degrees, 135 degrees, 90 degrees, 45 degrees, 0 degrees, −45 degrees, −90 degrees, and −135 degrees, the maximum value of return loss (S 11 ) of the microstrip antenna transceiver  10  operated in a range of 1.466 GHz to 1.472 GHz is −21.0 dB, −25.0 dB, −21.2 dB, −22.4 dB, −22.9 dB, −27.7 dB, −24.6 dB and −17.3 dB, respectively. Moreover, the microstrip antenna transceiver  10  can meet the requirements for antenna gain and common polarization to cross polarization (Co/Cx) value, and produce circularly polarized signals of axial ratio approximating 1. In other words, instead of adjusting the antenna dimensions, the phase shift between the vertically polarized signal SV and the horizontally polarized signal SH can be changed to obtain the required electromagnetic field solution by adjusting the sizes SL 1 _L, SL 1 _W, SL 2 _L, SL 2 _W and the displacements SL 1 _D, SL 2 _D of the pattern slots SL 1 , SL 2  according to the reflection phases of the switch element  136 ,  138 . 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 the reflection phase (degree) 
                 180 
                 135 
                 90 
                 45 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 the size SL1_W (mm) 
                 1.90 
                 1.97 
                 2.39 
                 2.22 
               
               
                 the size SL1_L (mm) 
                 22.0 
                 19.0 
                 22.1 
                 24.2 
               
               
                 the displacements 
                 11.2 
                 13.0 
                 33.5 
                 18.5 
               
               
                 SL1_D (mm) 
               
               
                 the size SL2_W (mm) 
                 2.27 
                 2.31 
                 2.36 
                 2.10 
               
               
                 the size SL2_L (mm) 
                 8.00 
                 8.50 
                 7.29 
                 7.15 
               
               
                 the displacements 
                 26.6 
                 30.8 
                 33.2 
                 23.8 
               
               
                 SL2_D (mm) 
               
               
                 return loss (dB) 
                 −21.0 
                 −25.0 
                 −21.2 
                 −22.4 
               
               
                 polarization 
                 left-handed 
                 left-handed 
                 left-handed 
                 right-handed 
               
               
                   
                 polarization 
                 polarization 
                 polarization 
                 polarization 
               
               
                 maximum gain (dBi) 
                 6.88 
                 6.91 
                 6.93 
                 6.75 
               
               
                 common polarization 
                 29 
                 28 
                 31 
                 28 
               
               
                 to cross polarization 
               
               
                 (Co/Cx) value (dB) 
               
               
                 front-to-back ratio 
                 14 
                 14 
                 14 
                 14 
               
               
                 (dB) 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 the reflection phase (degree) 
                 0 
                 −45 
                 −90 
                 −135 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 the size SL1_W (mm) 
                 2.40 
                 1.97 
                 2.25 
                 2.16 
               
               
                 the size SL1_L (mm) 
                 23.5 
                 21.9 
                 21.0 
                 28.8 
               
               
                 the displacements 
                 15.3 
                 13.2 
                 14.6 
                 6.86 
               
               
                 SL1_D (mm) 
               
               
                 the size SL2_W (mm) 
                 2.74 
                 4.72 
                 4.52 
                 2.54 
               
               
                 the size SL2_L (mm) 
                 12.6 
                 13.1 
                 11.8 
                 9.06 
               
               
                 the displacements 
                 26.6 
                 28.7 
                 29.1 
                 27.4 
               
               
                 SL2_D (mm) 
               
               
                 return loss (dB) 
                 −22.9 
                 −27.7 
                 −24.6 
                 −17.3 
               
               
                 polarization 
                 right-handed 
                 right-handed 
                 right-handed 
                 left-handed 
               
               
                   
                 polarization 
                 polarization 
                 polarization 
                 polarization 
               
               
                 maximum gain (dBi) 
                 6.82 
                 6.82 
                 6.73 
                 6.57 
               
               
                 common polarization 
                 24 
                 29 
                 18 
                 19 
               
               
                 to cross polarization 
               
               
                 (Co/Cx) value (dB) 
               
               
                 front-to-back ratio 
                 14 
                 14 
                 14 
                 15 
               
               
                 (dB) 
               
               
                   
               
            
           
         
       
     
     The switch elements  136 ,  138  can be selected from transistors or diode elements, but not limited herein. The switch element  136  is disposed along the vertical direction X and the switch element  138  is disposed on the horizontal direction Y, but not limited thereto. The lengths of the microstrip lines  146 ,  148  remain constant even if the reflection phases of the switch elements  136 ,  138  differ. The distances L 1 , L 2  of the microstrip lines  146 ,  148  from the switch elements  136 ,  138  to the openings  106 ,  108  are approximately zero, and hence the microstrip lines  146 ,  148  merely electrically connects one element to another without changing signal phase, thereby providing a relative small sized microstrip antenna transceiver  10 , reducing energy loss of the microstrip lines  146 ,  148 , improving antenna gain, and avoiding noise. However, the present invention is not limited to this and the lengths of the microstrip lines  146 ,  148  may be adjusted according to different design requirements. 
     Besides, the pattern slots SL 1 , SL 2  of the radiation patch  124  have a shape substantially conforming to an L-shaped structure, but not limited thereto. For example,  FIG. 11  and  FIG. 12  are schematic diagrams illustrating top views of front surfaces of microstrip antenna transceivers  11  and  12  according to embodiments of the present invention. Pattern slots SL_a, SL_b of the microstrip antenna transceivers  11 ,  12  have shapes substantially conforming to a cross-shaped structure and a stepwise structure, respectively. To maintain resonance frequency and to ensure resonance of radiation patches  124   a  and  124   b  of the microstrip antenna transceivers  11  and  12 , the pattern slot SL_a and SL_b are closed pattern and never cut the radiation patches  124   a  and  124   b  into pieces. For the vertically polarized signal SV resonating along the vertical direction X, the pattern slot can be extended along the horizontal direction Y; for the horizontally polarized signal SH resonating along the horizontal direction Y, the pattern slot can be extended along the vertical direction X. Consequently, the pattern slot can be symmetric with respect to the symmetrical axis XS. The pattern slots SL_a and SL_b can replace the pattern slots SL 1 , SL 2  shown in  FIG. 1A . Alternatively, the pattern slots SL_a and SL_b can be added into the radiation patch  124  shown in  FIG. 1A , such that the radiation patch  124  comprises a plurality of pattern slots. 
     To sum up, the microstrip antenna transceiver of the present invention can transmit (or receive) signals of different polarizations in different time and is cost effective by controlling the switch elements and by adjusting the cutting corners of the radiation patch, the displacements of the feed-in points or the sizes and the displacements of the pattern slots. Furthermore, the lengths of the microstrip lines are shortened to minimize the dimensions of the microstrip antenna transceiver, thereby providing a relative small sized microstrip antenna transceiver, reducing energy loss of the microstrip lines, improving antenna gain, and avoiding noise. 
     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. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.