Patent Publication Number: US-7898483-B2

Title: Digital TV antenna

Description:
RELATED APPLICATIONS 
     This application claims priority to Taiwan Application Serial Number 97129120, filed Jul. 31, 2008, which is herein incorporated by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to an antenna apparatus, and especially to an antenna apparatus for receiving digital TV signals. 
     BACKGROUND OF THE INVENTION 
     The key development in communication technology has been the transfer from wired to wireless communication, especially in the field of propagating digital TV signals. The signal propagates through the air in the form of electromagnetic waves, where the bridge of the signals between the wireless unit and the air is an antenna. That is to say, wireless communication units need antennas to transmit or receive electromagnetic waves, and they are therefore essential components of wireless communication units. 
     The typical antenna used in the digital TV field is helical antenna. Although the structure of the helical antenna is simple, the bandwidth and the radiation efficiency of the helical antenna are not enough for the propagating digital TV signal. 
     Therefore, an improved antenna is desired to overcome the above-mentioned shortcomings of existing antennas. 
     SUMMARY OF THE INVENTION 
     Therefore, the main purpose of the present invention is to provide a digital TV antenna with a wide bandwidth and high radiation efficiency. 
     In accordance with the foregoing purpose, the present invention discloses a digital TV antenna located in a substrate. The substrate has a first surface and a second surface opposite to the first surface. The digital TV antenna includes a grounding plane, a first radiation conductor, a second radiation conductor and a third radiation conductor. The grounding plane located in the first surface. The grounding place has a main grounding plane with a grounding terminal and an extended grounding plane extending from the main grounding plane. The first radiation conductor located in the first surface. The first radiation conductor with a feeding terminal has a first side and a second side opposite to the first side. The first radiation conductor couples with the grounding plane. A predetermined distance exists between the first side and the extended grounding plane. A second radiation conductor located in the second surface couples with the first radiation conductor. Partial second radiation conductor crosses the first side for a first distance to cover the first radiation conductor to form an overlapping region. A third radiation conductor located in the second surface couples with the second radiation conductor. Partial third radiation conductor crosses the second side for a second distance to cover the first radiation conductor to form an overlapping region. 
     In an embodiment, the first distance is at least 1 mm. The second distance is at least 0.2 mm. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a schematic perspective diagram of a digital TV antenna according to an embodiment. 
         FIG. 2  is a schematic diagram of a first radiation conductor and a grounding plane according to the first embodiment. 
         FIG. 3  is a schematic diagram of a first radiation conductor and a grounding plane according to the second embodiment. 
         FIG. 4  is a schematic diagram of a first radiation conductor and a grounding plane according to the third embodiment. 
         FIG. 5  is a schematic diagram of a second radiation conductor and a third radiation conductor according to the first embodiment. 
         FIG. 6  is a schematic diagram of a second radiation conductor and a third radiation conductor according to the second embodiment. 
         FIG. 7  is a schematic diagram of a second radiation conductor and a third radiation conductor according to the third embodiment. 
         FIG. 8  is a cross-section view along AA′ line in the  FIG. 1 . 
         FIG. 9  is a test chart of return loss for the Digital TV antenna of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  is a schematic perspective diagram of a digital TV antenna according to an embodiment. The digital TV antenna  100  is located on the first surface  120   a  and the second surface  120   b  opposite to the first surface  120   a  of a dielectric substrate  120 . The digital TV antenna receives frequencies in the range from 470 MHz to 870 MHz. 
     The digital TV antenna  100  includes three radiation conductors and a grounding plane  108 . The three radiation conductors are the first radiation conductor  102 , the second radiation conductor  104  and the third radiation conductor  106 . The first radiation conductor  102  and the grounding plane  108  are located in the first surface  120   a  of the substrate  120 . The second radiation conductor  104  and the third radiation conductor  106  locate in the second surface  120   b  of the substrate  120 . It is noticed that a perspective substrate is illustrated in the  FIG. 1  so as to present the second radiation conductor  104  and the third radiation conductor  106  partially overlap the first radiation conductor  102 . One end of the first radiation conductor  102  connects with couples a first extended metal arm  110 . One end of the third radiation conductor connects with a second extended metal arm  112 . 
       FIG. 2  is a schematic diagram of a first radiation conductor and a grounding plane according to the first embodiment. The first radiation conductor  102  and the grounding plane  108  are located in the first surface  120   a  of the substrate  120 . 
     The grounding plane  108  includes a main grounding plane  1081  and an extended grounding plane  1082  extending from the main grounding plane  1081 . A grounding terminal  1083  is in the main grounding plane  1081 . The extended grounding plane  1082  has a bended appearance. In an embodiment, the extended grounding plane  1082  includes a first extended segment  10821 , a second extended segment  10822  and a third extended segment  10823 . The three extended segments have a reversed “U” appearance. In other embodiments, different appearances of the three extended segments also can be used in the present invention. 
     The first radiation conductor  102  includes a main radiation segment  1021  and a connecting segment  1022 . The main radiation segment  1021  and the first extended segment  10821  are arranged in parallel to each other and a predetermined distance d 1  exists between them. In an embodiment, the predetermined distance d 1  is 0.8 mm. In other embodiments, the predetermined distance is changeable based on the antenna design. A feeding terminal  1024  is located in a side of the main radiation segment  1021 . In an embodiment, a step metal arm  1025  is extended from a side of the main radiation segment  1021  near the main grounding plane  1081  to make the feeding terminal  1024  and the grounding terminal  1083  be close. The connecting segment  1022  and the second extended segment  10822  are arranged in parallel to each other. A through hole  1023  passing through the substrate  120  is formed in the connecting segment  1022 . The first radiation conductor  102  and the second radiation conductor  104  are connected together through the through hole  1023 . In an embodiment, a metal arm  1026  whose arm width is 0.8 mm is extended from a side of the main radiation segment  1021  to connect with the connecting segment  1022 . The operation frequency and wavelength of an antenna are related to the length and the area of this antenna. Therefore, the bandwidth of the antenna is designated by changing the length or area of the metal arm  1026 . 
       FIG. 3  and  FIG. 4  illustrate different structures for the metal arm  1026 . In  FIG. 3 , the main radiation segment  1021  is a rectangular metal plate. The feeding terminal  1024  located in a side of the main radiation segment  1021  near the main grounding plane  1081 . In other words, the step metal arm  1025  is not needed in this embodiment. It is noticed that the embodiment does not limit the appearance of the metal arm  1026  and the main radiation segment  1021  in practice. The connecting segment  1022  connects with a first extended metal arm  110 . This first extended metal arm  110  is an extension antenna. The length of the extension antenna is less than 130 mm. In an embodiment, the feeding terminal  1024  and the grounding terminal  1083  connect with a coaxial cable (not shown in the figure). The feeding terminal  1024  connects with the inner copper core of the coaxial cable. The grounding terminal  1083  connects with copper screen of the coaxial cable. 
       FIG. 5  is a schematic diagram of a second radiation conductor and a third radiation conductor according to the first embodiment. The second radiation conductor  104  and the third radiation conductor  106  located in the second surface  120   b  of the substrate  120 . 
     The second radiation conductor  104  includes a main radiation segment  1041  and a connecting segment  1042 . The main radiation segment  1041  has a strip appearance. The connecting segment  1042  is extended from a side of the main radiation segment  1041  and is arranged in the side. A predetermined distance d 2  exists between the connecting segment  1042  and the side. In an embodiment, the predetermined distance d 2  is 1.5 mm. The embodiment does not limit the predetermined distance d 2  in practice. A through hole  1023  passing through the substrate  120  is formed in the connecting segment  1042 . The first radiation conductor  102  and the second radiation conductor  104  are connected together through the through hole  1023 . The operation frequency and wavelength of an antenna are related to the length and the area of this antenna. Therefore, a bump  1044  is added in a side, such as the side near the third radiation conductor, of the main radiation segment  1041  to change its area to adjust the operation frequency and wavelength. It is noticed that the embodiment does not limit the added location of the bump  1044  in practice. For example, in  FIG. 6 , the bump  1044  is added in a side of the main radiation segment  1041  opposite to the side near the third radiation conductor. In other embodiment, no bump is added in the second radiation conductor  104  as illustrated in the  FIG. 7 . 
     The third radiation conductor  106  includes a main radiation segment  1061  and a connecting segment  1062 . The main radiation segment  1061  has a strip appearance. The main radiation segment  1061  is arranged to and connects with a side of the second radiation conductor  104 . The connecting segment  1062  connects a side of the main radiation segment  1061 . The connecting segments  1062  and  1042  are arranged in parallel to each other and a predetermined distance d 3  exists between them. In an embodiment, the predetermined distance d 3  is 1.3 mm. The embodiment does not limit the predetermined distance d 3  in practice. The connecting segment  1062  connects with a second extended metal arm  112 . This first extended metal arm  112  is an extension antenna. The length of the extension antenna  112  is less than 130 mm. The operation frequency and wavelength of an antenna are related to the length and the area of this antenna. Therefore, a bump  1066  is added in a side of the main radiation segment  1061  to change its area to adjust the operation frequency and wavelength. It is noticed that the embodiment does not limit the added location of the bump  1066  in practice. For example, in  FIG. 6 , the bump  1066  is added in a side of the main radiation segment  1061  near the second radiation conductor  104 . In other embodiment, no bump is added in the third radiation conductor  106  as illustrated in the  FIG. 7 . 
       FIG. 8  is a cross-section view along AA′ line in the  FIG. 1 . According to the present invention, the second radiation conductor  104  in the second surface  102   b  partially overlaps a side of the first radiation conductor  102  near the grounding plane  108  in the first surface  120   a . In an embodiment, the width d 4  of the second radiation conductor  104  overlapping the first radiation conductor  102  is larger than 0.6 mm, and preferred between 0.6 mm˜3.6 mm. Moreover, the third radiation conductor  106  in the second surface  102   b  partially overlaps another side of the first radiation conductor  102  in the first surface  120   a . In an embodiment, the width d 5  of the third radiation conductor  106  overlapping the first radiation conductor  102  is larger than 0.2 mm, and preferred between 0.2 mm˜3.6 mm. The resonant frequency is changeable by adjusting the overlapping area between the second radiation conductor  104  and the first radiation conductor  102  and between the third radiation conductor  106  and the first radiation conductor  102 . 
       FIG. 9  is a test chart of return loss for the Digital TV antenna of the present invention. The return loss is over 6 dB between the range from 470 MHz to 870 MHz. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.