Abstract:
A wideband planar dipole antenna comprises a substrate and two antenna bodies. Metal conductor is printed on the single surface/double surfaces of the substrate to form the antenna bodies. With a dipole antenna architecture, the antenna bodies are manufactured as loop structures similar to concentric circles. The loop structures can be of rectangular or circular shapes. Loops of metal conductors with different lengths resonate to obtain similar but different frequencies. Each path of every antenna body can be finally connected with a metal conductor sheet capable of changing to any shape. Every path can interfere with adjacent paths to achieve the wideband effect. An asymmetric mechanism can be added in one of the antenna bodies. Besides letting the antenna have the resonance effect of the symmetric part, the loop path at the signal source can also be increased to enhance the receiving performance of the antenna.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a wideband planar dipole antenna and, more particularly, to a single-surface/double-surface wideband planar dipole antenna that is manufactured by using a symmetric or asymmetric mechanism.  
         [0003]     2. Description of Related art  
         [0004]     Digital TV broadcasting systems have developed very quickly in recent years. In order to receive all programs in the UHF band, a digital TV UHF antenna with the operational frequency from 470 MHz to 860 MHz is usually required. Existent antennas used in the UHF band are commonly yagi antennas or rod antennas, both of which are illustrated below.  
         [0005]     A yagi antenna is composed of many antennas at different lengths, and achieves the wideband effect by combining different resonance frequencies. This kind of antenna has a better receiving performance when installed outdoors. The yagi antenna, however, is bulky and heavy, and is therefore not suitable to the applications of indoor digital TV systems. A rod antenna is based on the principle of monopole antenna. The length of this kind of antenna is designed to be a quarter of the wavelength (λ/4). Commercially, a rod antenna is spirally wound to shorten its effective length, and a ground plane is finally added at the base of the antenna to finish a rod antenna with a minimized size. This kind of antenna has a slightly inferior receiving performance, and is less convenient in use. The above two kinds of antennas have a high manufacturing cost, and is too large in size.  
         [0006]     In consideration of the above drawbacks of existent digital TV antennas, i.e., bulky size, inconvenient portability and high cost, the present invention aims to provide a wideband planar dipole antenna to solve the above problems in the prior art.  
       SUMMARY OF THE INVENTION  
       [0007]     An object of the present invention is to provide a wideband planar dipole antenna having the characteristics of small size, light weight, easy manufacturing, and low cost. Moreover, the wideband planar dipole antenna can adhere to the surface of any object without affecting the appearance and structure of the object. The wideband planar dipole antenna can also be designed to be an indoor UHF antenna that brings much convenience for digital TV.  
         [0008]     Another object of the present invention is to provide a wideband planar dipole antenna, wherein an asymmetric mechanism can be added in an antenna body to enhance the receiving performance of antenna.  
         [0009]     To achieve the above objects, the present invention provides a wideband planar dipole antenna, which comprises a substrate, a first antenna body and a second antenna body. The first antenna body is used as the signal source, and the second antenna body is used as the ground. The first antenna body is located on one side of the substrate, made of a metal conductor, and printed on the substrate in a multi-loop routing way to be used as a radiation area. The first antenna body also has a metal conductor with an arbitrary polygon shape to let a part or all of multiple loops in the first antenna body be connected together. The second antenna body is located on the substrate and adjacent to the first antenna body. The second antenna body is made of a metal conductor, and is printed on the substrate in a multi-loop routing way to be used as a radiation area. The second antenna body also has a metal conductor with an arbitrary polygon shape to let a part or all of multiple loops in the second antenna body be connected together, thereby forming a single-surface wideband planar dipole antenna. Besides, two feed lines can also penetrate the substrate and connect part of the multiple loops in the first and second antenna bodies that are printed on two surfaces of the substrate to form a double-surface wideband planar dipole antenna. By manufacturing a rectangular structure similar to concentric circles, loops of metal conductors with different lengths resonate to obtain similar but different frequencies. Each path of every antenna body can be connected with a metal conductor sheet capable of changing to any shape. In this way, in addition to producing the original resonance phenomenon, every path can interfere with adjacent paths to achieve the wideband effect. Moreover, an asymmetric mechanism can also be added in one of the antenna bodies. Besides letting the antenna have the resonance effect of the symmetric part, the loop path at the signal source can also be extra increased to enhance the receiving performance of the antenna, minimize the total return loss of the antenna. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawing, in which:  
         [0011]      FIG. 1  is a diagram of the antenna architecture according to a first embodiment of the present invention;  
         [0012]      FIG. 2  is a diagram of the experimental data according to the first embodiment of the present invention;  
         [0013]      FIG. 3  is a diagram of the antenna architecture according to a second embodiment of the present invention;  
         [0014]      FIG. 4  is a diagram of the experimental data according to the second embodiment of the present invention;  
         [0015]      FIG. 5  is a diagram of the antenna architecture according to a third embodiment of the present invention;  
         [0016]      FIG. 6  is a diagram of the experimental data according to the third embodiment of the present invention;  
         [0017]      FIG. 7  is a diagram of the antenna architecture according to a fourth embodiment of the present invention;  
         [0018]      FIG. 8  is a diagram of the experimental data according to the fourth embodiment of the present invention;  
         [0019]      FIG. 9  is a diagram of the antenna architecture according to a fifth embodiment of the present invention;  
         [0020]      FIG. 10  is a top view of the antenna architecture according to the fifth embodiment of the present invention;  
         [0021]      FIG. 11  is a bottom view of the antenna architecture according to the fifth embodiment of the present invention; and  
         [0022]      FIG. 12  is a diagram of the experimental data according to the fifth embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0023]     In a wideband planar dipole antenna of the present invention, metal conductor such as copper foil can be printed on one surface or double surfaces of the substrate to form an antenna. The produced usable frequency range is primary between 470 MHz and 860 MHz. The wideband planar dipole antenna of the present invention makes use of the basic architecture of a printed planar dipole antenna. It is only necessary to form the designed pattern on a single surface or double surfaces of the substrate and use loops of metal conductors with different lengths to resonate at different frequencies so as to achieve the wideband effect. Moreover, an asymmetric mechanism can be added in the antenna pattern to enhance the receiving performance of the antenna. The substrate can be selected among media of appropriate thickness and dielectric constant such as glass, ceramic and silicon. Different materials have different performances. In all embodiments of the present invention, an FR4 Printed Circuit Board (PCB) is selected as the medium of the substrate, and the thickness is properly adjusted according to different demands.  
         [0024]      FIG. 1  shows a wideband planar dipole antenna according to the first embodiment of the present invention. As shown in  FIG. 1 , the wideband planar dipole antenna comprises a substrate  1  and dipole antenna bodies  21  and  22 . Copper foil is printed on the upper surface of the substrate  1  to form the dipole antenna bodies  21  and  22 . The antenna bodies  21  and  22  are two mutually symmetric patterns. The antenna body  21  is the ground, while the antenna body  22  is the signal source. Each of the antenna bodies  21  and  22  is composed of three-loop copper foils  210 ,  211  and  212  and a quadrilateral copper foil  213 . The loop copper foil  210  is the outmost perimeter of the antenna bodies  21  and  22 , surrounds a rectangle with an appropriate size, and is finally connected to the quadrilateral copper foil  213 . Its surrounding length is the longest of all the loop copper foils. The loop copper foil  210  is used to resonate at the lowest frequency in the designed frequency band. At an appropriate spacing, the loop copper foil  211  surrounds a rectangle inside the loop copper foil  210 , and is finally connected to the quadrilateral copper foil  213 . Its surrounding length is slightly shorter than that of the loop copper foil  210 . Again at an appropriate spacing, the loop copper foil  212  surrounds a rectangle inside the loop copper foil  211 , and is finally connected to the quadrilateral copper foil  213 . Its surrounding length is slightly shorter than that of the loop copper foil  211 . The antenna bodies  21  and  22  are symmetric to each other. The first embodiment of the present invention makes use of the three-loop copper foils  210 ,  211  and  212  and the quadrilateral copper foil  213  located at the center to combine their resonance effects, forming an antenna having a 200 MHz-bandwidth at the UHF band. Measured data of the return loss (S 11 ) in  FIG. 2  shows that the frequency range with the S 11  below −10 dB is the preferred usage range of the present invention.  
         [0025]     The second embodiment of the present invention differs from the first embodiment in that the number of loop copper foils is increased to enlarge the bandwidth of the antenna. As shown in  FIG. 3 , the wideband planar dipole antenna comprises a substrate  1  and dipole antenna bodies  31  and  32 . Copper foil is printed on the upper surface of the substrate  1  to form the dipole antenna bodies  31  and  32 . The antenna bodies  31  and  32  are two mutually symmetric patterns. The antenna body  31  is the ground, while the antenna body  32  is the signal source. Each of the antenna bodies  31  and  32  is composed of nine loop copper foils  310 ,  311 ,  312 ,  313 ,  314 ,  315 ,  316 ,  317  and  318  and a polygonal copper foil  319 . The loop copper foil  310  is the outmost perimeter of the antenna bodies  31  and  32 , surrounds a rectangle with an appropriate size, and is finally connected to the polygonal copper foil  319 . Its surrounding length is the longest of all the loop copper foils. The loop copper foil  310  is used to resonate at the lowest frequency in the designed frequency band. At an appropriate spacing, the loop copper foil  311  surrounds a rectangle inside the loop copper foil  310 , and is finally connected to the polygonal copper foil  319 . Its surrounding length is slightly shorter than that of the loop copper foil  310 . Reasoning by analogy, at respectively appropriate spacing, the loop copper foil  312  surrounds a rectangle inside the loop copper foil  311 , the loop copper foil  313  surrounds a rectangle inside the loop copper foil  312 , the loop copper foil  314  surrounds a rectangle inside the loop copper foil  313 , the loop copper foil  315  surrounds a rectangle inside the loop copper foil  314 , the loop copper foil  316  surrounds a rectangle inside the loop copper foil  315 , the loop copper foil  317  surrounds a rectangle inside the loop copper foil  316 , the loop copper foil  318  surrounds a rectangle inside the loop copper foil  317 , and they all are finally connected to the polygonal copper foil  319 . The surrounding lengths of the loop copper foils  310 ,  311 ,  312 ,  313 ,  314 ,  315 ,  316 ,  317  and  318  diminish gradually, with the loop copper foil  310  having the longest length and the loop copper foil  318  having the shortest length. The antenna bodies  31  and  32  are symmetric to each other.  
         [0026]     The second embodiment of the present invention makes use of the nine-loop copper foils  310 ˜ 318  and the polygonal copper foil  319  located at the center to combine their resonance effects, forming an antenna having a 380 MHz-bandwidth at the UHF band. The obtained antenna is a very wide-band antenna with a center frequency of 655 MHz and a 58% bandwidth ratio. Measured data of the return loss (S 11 ) in  FIG. 4  shows that the frequency range with the S 11  below −10 dB is the preferred usage range of the present invention.  
         [0027]     The third embodiment of the present invention differs from the above embodiments in that an asymmetric mechanism is added in the signal source with respect to the ground to enhance the receiving performance of the whole antenna. As shown in  FIG. 5 , the wideband planar dipole antenna comprises a substrate  1 , a first antenna body  41  and a second antenna body  42 . Copper foil is printed on the upper surface of the substrate  1  to form the first and second antenna bodies  41  and  42 . The first antenna body  41  is the signal source, while the second antenna body  42  is the ground. Each of the first and second antenna bodies  41  and  42  is composed of nine-loop copper foils  410 ,  411 ,  412 ,  413 ,  414 ,  415 ,  416 ,  417  and  418  and a polygonal copper foil  419 . In addition to having the same pattern as the second embodiment, the third embodiment also has an asymmetric mechanism (called an extra loop copper foil  430 ) added in the first antenna body  41  (signal source) with respect to the second antenna body (ground). Besides letting the antenna have the resonance effect of the symmetric part, the extra loop copper foil  430  also has the function of extra increasing the loop path of the signal source to enhance the receiving effect of the antenna, minimizing the total return loss of the antenna. Measured data of the return loss (S 11 ) in  FIG. 6  shows that the frequency range with the S 11  below −10 dB is the preferred usage range of the present invention. As compared to the measured data of the second embodiment ( FIG. 4 ), the third embodiment has the effect of minimizing the return loss in the resonance frequency band.  
         [0028]      FIG. 7  shows a wideband planar dipole antenna according to the fourth embodiment of the present invention. As shown in  FIG. 7 , the fourth embodiment integrates the multiple loop copper foil structure adopted in the above three embodiment and the asymmetric mechanism to manufacture a digital TV receiving antenna applicable in the UHF band. The wideband planar dipole antenna comprises a substrate  1 , a first antenna body  51  and a second antenna body  52 . Copper foil is printed on the upper surface of the substrate  1  to form the first and second antenna bodies  51  and  52 . The first antenna body  51  is used as the signal source, while the antenna body  52  is used as the ground. Each of the first and second antenna bodies  51  and  52  is composed of eight loop copper foils  510 ,  511 ,  512 ,  513 ,  514 ,  515 ,  516  and  517  and a polygonal copper foil  518 . The loop copper foil  510  is the outmost perimeter of the first and second antenna bodies  51  and  52 , surrounds a rectangle with an appropriate size, and is finally connected to the polygonal copper foil  518 . Its surrounding length is the longest of all the loop copper foils. The loop copper foil  510  is used to resonate at the lowest frequency in the designed frequency band. At an appropriate spacing, the loop copper foil  511  surrounds a rectangle inside the loop copper foil  510 , and is finally connected to the polygonal copper foil  518 . Its surrounding length is slightly shorter than that of the loop copper foil  510 . Reasoning by analogy, at respectively appropriate spacing, the loop copper foil  512  surrounds a rectangle inside the loop copper foil  511 , the loop copper foil  513  surrounds a rectangle inside the loop copper foil  512 , the loop copper foil  514  surrounds a rectangle inside the loop copper foil  513 , the loop copper foil  515  surrounds a rectangle inside the loop copper foil  514 , the loop copper foil  516  surrounds a rectangle inside the loop copper foil  515 , the loop copper foil  517  surrounds a rectangle inside the loop copper foil  516 , and they all are finally connected to the polygonal copper foil  518 . The surrounding lengths of the loop copper foils  510 ,  511 ,  512 ,  513 ,  514 ,  515 ,  516  and  517  diminish gradually, with the loop copper foil  510  having the longest length and the loop copper foil  517  having the shortest length.  
         [0029]     In addition to having the pattern symmetric to the second antenna body  52 , the first antenna body  51  (signal source) also has the extra loop copper foil  530  in the third embodiment. The antenna of the fourth embodiment of the present invention has a return loss below −10 dB between 465 MHz and 880 MHz, and is a very wide band antenna with a center frequency of 672.5 MHz and a 61.7% bandwidth ratio. Measured data of the return loss (S 11 ) in  FIG. 8  shows that the frequency range with the S 11  below −10 dB is the preferred usage range of the present invention.  
         [0030]      FIG. 9  is a diagram of the antenna architecture according to a fifth embodiment of the present invention.  FIG. 10  is a top view of the antenna architecture according to the fifth embodiment of the present invention.  FIG. 11  is a bottom view of the antenna architecture according to the fifth embodiment of the present invention. As shown in  FIGS. 9, 10  and  11 , the fifth embodiment is characterized in that multiple loop copper foils are used to manufacture a digital TV receiving antenna applicable in the UHF band by utilizing a double-surface routing mechanism. The wideband planar dipole antenna comprises a substrate  1 , a first antenna body  61  and a second antenna body  62 . Copper foil is printed on the surfaces of the substrate  1  to form the first and second antenna bodies  61  and  62 . The first antenna body  61  is used as the signal source, while the antenna body  62  is used as the ground. Each of the first and second antenna bodies  61  and  62  is composed of nine loop copper foils  610 ,  611 ,  612 ,  613 ,  614 ,  615 ,  616 ,  617  and  618  and a polygonal copper foil  619 . The loop copper foil  610  is the outmost perimeter of the first antenna body  61 , surrounds a rectangle with an appropriate size on the front surface of the antenna, and is finally connected to the polygonal copper foil  619 . Its surrounding length is the longest of all the loop copper foils. The loop copper foil  610  is used to resonate at the lowest frequency in the designed frequency band. At an appropriate spacing, the loop copper foil  611  surrounds a rectangle inside the loop copper foil  610  on the back surface of the antenna, and is finally connected to the polygonal copper foil  619 . The loop copper foil  611  uses two feed lines to penetrate and connect the front and back surfaces of the substrate  1 . Its surrounding length is slightly shorter than that of the loop copper foil  610 . Reasoning by analogy, at respectively appropriate spacing, the loop copper foil  612  surrounds a rectangle inside the loop copper foil  611  on the front surface of the substrate  1 , the loop copper foil  613  surrounds a rectangle inside the loop copper foil  612  on the back surface of the substrate  1 , the loop copper foil  614  surrounds a rectangle inside the loop copper foil  613  on the front surface of the substrate  1 , the loop copper foil  615  surrounds a rectangle inside the loop copper foil  614  on the back surface of the substrate  1 , the loop copper foil  616  surrounds a rectangle inside the loop copper foil  615  on the front surface of the substrate  1 , the loop copper foil  617  surrounds a rectangle inside the loop copper foil  616  on the back surface of the substrate  1 , the loop copper foil  618  surrounds a rectangle inside the loop copper foil  617  on the front surface of the substrate  1 , and they all are finally connected to the polygonal copper foil  619 . The routing is alternately distributed on the front and back surfaces of the substrate  1  at appropriate spacing. The surrounding lengths of the loop copper foils  610 ,  611 ,  612 ,  613 ,  614 ,  615 ,  616 ,  617  and  618  diminish gradually, with the loop copper foil  610  having the longest length and the loop copper foil  618  having the shortest length. The loop copper foils on the back surface can be connected with the loop copper foils on the front surface using feed lines. In addition to having the pattern symmetric to the second antenna body  62 , the first antenna body  61  (signal source) also has the extra loop copper foil  630  in the third embodiment. The antenna of the fifth embodiment of the present invention has a return loss below −10 dB between 468 MHz and 958 MHz, and is a very wide band antenna with a center frequency of 713 MHz and a 68.9% bandwidth ratio. Measured data of the return loss (S 11 ) in  FIG. 12  shows that the frequency range with the S 11  below −10 dB is the preferred usage range of the present invention.  
         [0031]     Although the present invention has been described with reference to the preferred embodiment thereof, it will be understood that the invention is not limited to the details thereof. Various substitutions and modifications have been suggested in the foregoing description, and other will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be embraced within the scope of the invention as defined in the appended claims.