Patent Publication Number: US-8976070-B2

Title: Broadcasting antenna for vehicle and shark fin antenna apparatus having the same

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates, in general, to a broadcasting antenna for a vehicle and a shark fin antenna apparatus having the same, and more particularly to a broadcasting antenna for a vehicle and a shark fin antenna apparatus having the same, which includes a helical radiation unit made up of a plurality of helical radiators and having a coupling feed structure and an extended radiation unit made up of a plurality of top loaders, each of which includes a band stop filtering unit and conductive patterns, thereby improving radiation efficiency and preventing signal interference. 
     2. Description of the Related Art 
     With the development of wireless communication technology, a variety of wireless communication antennas are mounted on vehicles. In the case of a typical broadcasting antenna for a vehicle which operates at an FM/AM broadcasting frequency band, use is made of a monopole, type of retractable antenna whose length is adjusted to an operating frequency by a motor and which is mainly installed on the outside of the vehicle. However, this retractable antenna not only causes damage to an appearance of the vehicle, but also increases noise due to air resistance while traveling. 
     Further, to overcome these problems, a glass antenna, which is mainly installed around a defroster of a vehicle rear window, has an advantage in that it provides a smart appearance to the vehicle and no noise while traveling, but it has a disadvantage in that the manufacturing cost of the vehicle increases due to a royalty. The glass antenna operates like a slot antenna due to a fixed size of the rear window. As such, in the case of a vehicle whose rear window has a size that is unfit for resonance of a broadcasting frequency band, a helical micro-antenna having a length of 200 mm is used as the broadcasting antenna in place of the glass antenna. 
     However, this micro-antenna is installed outside the vehicle, causes damage to an appearance of the vehicle, and generates noise such as wind noise while traveling due to a protruding height, like the retractable antenna. To overcome these problems, the length of the micro-antenna may be reduced. In this case, radiation efficiency is reduced. 
     For this reason, attention has recently been paid to a shark fin antenna apparatus for a vehicle capable of providing a good design in appearance, avoiding an increase in manufacturing cost due to a royalty, and mounting a plurality of antennas at the same time. Furthermore, attention has also been paid to an attempt to mount the broadcasting antenna in the shark fin antenna apparatus. 
     However, when the broadcasting antenna is mounted in the shark fin antenna apparatus, a disc having a ground plane of a 1 meter size is used. In this case, due to a restricted space in which a height of the antenna should be within 70 mm, the broadcasting antenna is formed as a small electrical antenna whose size is smaller than λ/16 of the operating frequency. This small electrical antenna has a problem in that, as its size is reduced, its radiation efficiency is sharply reduced. As such, to obtain desired radiation efficiency within the restricted space, the total physical length of an antenna radiator is increased. In this case, the operating frequency shifted to a relatively low frequency band, so that it is difficult to meet requirements of a specific frequency band, and the appearance of the vehicle is also damaged. Further, since the plurality of antennas operating at different frequency bands coexist within the restricted space, characteristics of the additionally mounted broadcasting antenna and characteristics of the previously mounted antennas are simultaneously deteriorated due to signal inference. 
     Thus, there is an urgent need for technology that relatively improves the radiation efficiency within the restricted space in the shark fin antenna apparatus on which the plurality of antennas and the broadcasting antenna are mounted together, prevents the signal interference, and actually provides high applicability. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention has been made keeping in mind the above problems occurring in the related art, and an object of the present invention is to provide a broadcasting antenna for a vehicle and a shark fin antenna apparatus having the same, in which a helical radiation unit is made up of a plurality of helical radiators and has a coupling feed structure, and in which an extended radiation unit is made up of the plurality of top loaders, which are electrically connected to the ends of the plurality of helical radiators, and each of which includes at least one band stop filtering unit and a plurality of conductive patterns between which the band stop filtering unit is disposed. Thereby, the broadcasting antenna and the shark fin antenna apparatus can be made small within a restricted space, operate at a specific frequency band in spite of an increase in length, improve the radiation efficiency, and prevent the signal interference. 
     In order to achieve the above object, according to an aspect of the present invention, there is provided a broadcasting antenna for a vehicle, which includes a main board on which a feeder circuit and a ground plane are formed. The broadcasting antenna includes: a helical radiation unit which includes a plurality of helical radiators that are electrically connected to the feeder circuit and the ground plane of the main board, that are formed in a first direction, and that are coupled apart from each other by a predetermined interval, and which has a coupling feed structure; and an extended radiation unit which includes a plurality of top loaders that are electrically connected to ends of the plurality of helical radiators respectively, that are formed in a second direction, and that are coupled to each other. The plurality of top loaders each includes at least one band stop filtering unit and a plurality of conductive patterns between which the at least one band stop filtering unit is disposed. 
     According to another aspect of the present invention, there is provided a shark fin antenna apparatus having a broadcasting antenna for a vehicle, which includes a main board on which a feeder circuit and a ground plane are formed and which is formed on the main board. The shark fin antenna apparatus includes: a broadcasting antenna that includes: a helical radiation unit which includes a plurality of helical radiators that are electrically connected to the feeder circuit and the ground plane of the main board, that are formed in a first direction, and that are coupled apart from each other by a predetermined interval, and which has a coupling feed structure; and an extended radiation unit which includes a plurality of top loaders that are electrically connected to ends of the plurality of helical radiators respectively, that are formed in a second direction, and that are coupled to each other, the plurality of top loaders each including at least one band stop filtering unit and a plurality of conductive patterns between the band stop filtering unit is disposed; a mobile communication antenna that is formed in an upward direction of the main board, and is formed in a P shape on one side of a dielectric board, on opposite upper surfaces of which the plurality of top loaders constituting the extended radiation unit of the broadcasting antenna are partly disposed; and a circularly polarized ceramic patch antenna that includes a patch antenna at a predetermined position on the main board on which the broadcasting antenna and the mobile communication antenna are located, and an extended ground that is formed of a metal conductor having the same shape as the patch antenna and is electrically connected with the ground plane. 
     As described above, the present invention provides the broadcasting antenna in which a helical radiation unit is made up of the plurality of helical radiators and has the coupling feed structure, and an extended radiation unit is made up of the plurality of top loaders, which are electrically connected to the ends of the plurality of helical radiators and each of which includes at least one band stop filtering unit and a plurality of conductive patterns between which the band stop filtering unit is disposed. Thereby, the broadcasting antenna can be made small within a restricted space, operate at a specific frequency band in spite of an increase in length, improve the radiation efficiency, and prevent the signal interference. 
     Further, the present invention provides the shark fin antenna apparatus in which: the broadcasting antenna includes the helical radiation unit having the coupling feed structure, and the extended radiation unit made up of the plurality of top loaders that are electrically connected to the ends of the plurality of helical radiators and each include at least one band stop filtering unit and a plurality of conductive patterns between which the band stop filtering unit is disposed, and that can be made small within a restricted space, operate at a specific frequency band in spite of an increase in length, improve the radiation efficiency, and prevent the signal interference; the mobile communication antenna includes the second band stop filtering unit removing the interference signals and the conductive patterns between which the second band stop filtering unit is disposed, and that improves the radiation efficiency; and the circularly polarized ceramic patch antenna includes the extended ground which is formed under a patch antenna, which has a predetermined thickness, which is formed of a metal conductor having the same shape as the patch antenna unit, and which is electrically connected to a ground plane formed on a main board, and whose thickness can be adjusted to control the radiation efficiency at a specific frequency band. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objectives, features, and advantages of the present invention will be more clearly understood from the following detailed description when taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a schematic view showing a configuration of a broadcasting antenna for a vehicle according to an embodiment of the present invention; 
         FIG. 2  shows a configuration of the helical radiation unit of the broadcasting antenna according to the embodiment of the present invention; 
         FIG. 3A  is a schematic view showing a configuration of a normal mode helical antenna that resonates at 98 MHz; 
         FIG. 3B  is a schematic view showing a configuration of a helical antenna that has a coupling feed structure as in the embodiment of the present invention and is designed so as to correspond to  FIG. 3A ; 
         FIG. 3C  is a reflection coefficient when, among a plurality of helical conductors constituting the helical antenna of  FIG. 3B , the helical conductor connected to a ground plane is not present; 
         FIG. 3D  is a reflection coefficient when, among a plurality of helical conductors constituting the helical antenna of  FIG. 3B , the helical conductor connected to a ground plane is present; 
         FIG. 4  is a perspective view showing the extended radiation unit of the broadcasting antenna according to the embodiment of the present invention; 
         FIG. 5  is a schematic view showing a configuration of the extended radiation unit of  FIG. 4 ; 
         FIG. 6  is a schematic plane view showing top loaders installed on the extended radiation unit of  FIG. 5 ; 
         FIG. 7  is an equivalent circuit showing a band stop filtering unit constituting the top loaders of the extended radiation unit of  FIG. 6 ; 
         FIG. 8  is a graph showing a result of comparing radiation efficiencies of the normal mode helical antenna of  FIG. 3A  and the broadcasting antenna according to the embodiment of the present invention at an operating frequency band having the same resonant frequency of 98 MHz; 
         FIG. 9  is a perspective view showing a shark fin antenna apparatus having the broadcasting antenna according to another embodiment of the present invention; 
         FIG. 10  is a side view showing the shark fin antenna apparatus having the broadcasting antenna according to the other embodiment of the present invention; 
         FIG. 11  schematically shows a mobile communication antenna installed on the shark fin antenna apparatus of  FIG. 9  when viewed from the front and rear; 
         FIG. 12  is an equivalent circuit showing a second band stop filtering unit installed on the mobile communication antenna of  FIG. 11 ; 
         FIG. 13  is a schematic view showing a configuration of a circularly polarized ceramic patch antenna installed on the shark fin antenna apparatus of  FIG. 9 ; 
         FIG. 14  is an exploded perspective view showing the circularly polarized ceramic patch antenna of  FIG. 13 ; 
         FIGS. 15 and 16  show antenna characteristics of the mobile communication antenna before and after the other embodiment of the present invention is applied at an operating frequency band of 859 MHz; 
         FIGS. 17 and 18  show antenna characteristics of the mobile communication antenna before and after the other embodiment of the present invention is applied at an operating frequency band of 1920 MHz; and 
         FIGS. 19 and 20  show antenna characteristics of the mobile communication antenna before and after the other embodiment of the present invention is applied at an operating frequency band of 2345 MHz. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A broadcasting antenna for a vehicle and a shark fin antenna apparatus having the same for carrying out the present invention start from the assumption that a feeder circuit and a main board  1  having a ground plane are provided. 
     Reference will now be made in greater detail to exemplary embodiments of the invention with reference to the accompanying drawings. 
       FIG. 1  is a schematic view showing a configuration of a broadcasting antenna for a vehicle according to an embodiment of the present invention. 
     As shown in  FIG. 1 , the broadcasting antenna  100  for a vehicle according to an embodiment of the present invention improves radiation efficiency and prevents signal interference, and includes a helical radiation unit  110  having a plurality of helical radiators  101  and  102 , and an extended radiation unit  120  having a plurality of top loaders  121  and  122 . 
     In detail, the helical radiators  101  and  102  of the helical radiation unit  110  are electrically connected to a feeder circuit and a ground plane of a main board  1 , are formed in an upward direction (first direction) of the main board  1 , and are coupled apart from each other. Thereby, the helical radiation unit  110  has a coupling feed structure. The top loaders  121  and  122  of the extended radiation unit  120  are electrically connected to ends of the helical radiators  101  and  102 , are formed in a lengthwise direction (second direction) of the main board  1 , and are coupled to each other. 
     Here, the helical radiators  101  and  102  are inclined at a predetermined angle in an outward upward direction of the main board  1  to reduce electromagnetic interference from the ground plane of the main board  1 . An angle between the direction (first direction) in which the helical radiators  101  and  102  of the helical radiation unit  110  are formed and the direction (second direction) in which the top loaders  121  and  122  of the extended radiation unit  120  are formed is an acute angle. In the embodiment of the present invention, to prevent the helical radiation unit  110  having the plurality of helical radiators  101  and  102  from deviating from a restricted space, a dielectric board  103  on which the helical radiation unit  110  is formed is preferably inclined with respect to the main board  1  at a predetermined angle in the outward upward direction of the main board  1 . 
     Further, each of the top loaders  121  and  122  of the extended radiation unit  120  includes at least one band stop filtering unit  10  and a plurality of conductive patterns  31  between which the band stop filtering unit  10  is disposed. 
     Here, the at least one band stop filtering unit  10  includes at least one band stop filter  11  to remove interference signals operating at different frequency bands from that of a signal by which the broadcasting antenna  100  according to the embodiment is operated, and impedance matching elements  12  corresponding to the ends of the helical radiators  101  and  102  to which the top loaders  121  and  122  of the extended radiation unit  120  are electrically connected. 
     Further, to prevent the conductive patterns  31  from serving as antenna radiators, the conductive patterns  31  constituting each of the top loaders  121  and  122  are each formed at a shorter length than λ/8 of an operating frequency within a relatively highest one of frequency bands at which the interference signals other than the signal by which the broadcasting antenna is operated operates. 
       FIG. 2  shows a configuration of the helical radiation unit of the broadcasting antenna according to the embodiment of the present invention. 
     As shown in  FIG. 2 , the helical radiation unit  110  includes a first helical radiator  101  having a feeder  111  electrically connected to the feeder circuit of the main board  1 , a second helical radiator  102  having a ground  112  electrically connected to the ground plane of the main board  1 , and a main dielectric board  103  in which the first helical radiator  101  and the second helical radiator  102  are spaced apart from each other by a predetermined interval. 
     Here, each of the first and second helical radiators  101  and  102  includes through-holes  113  passing through the main dielectric board  103  and conductive line patterns  114  formed on opposite surfaces of the main dielectric board  103  so as to have a helical structure. 
     The helical radiation unit of  FIG. 2  will be described in comparison with a normal mode helical antenna with reference to  FIGS. 3A to 3D . 
     First, it is assumed that the helical radiation unit of  FIG. 2  according to the embodiment operates at an FM broadcasting frequency band from 88 MHz to 108 MHz. 
       FIG. 3A  is a schematic view showing a configuration of a normal mode helical antenna that resonates at 98 MHz. 
     As shown in  FIG. 3A , it is assumed that the normal mode helical antenna resonates at 98 MHz that is a central frequency of the FM broadcasting frequency band, and that a single helical conductor to which a feed signal is applied continues to be formed on two cylinders that have a diameter of 15 mm and a height of 60 mm and are disposed at an interval of 1 mm. 
       FIG. 3B  is a schematic view showing a configuration of a helical antenna that has a coupling feed structure as in the embodiment of the present invention, and is designed so as to correspond to  FIG. 3A . 
     The helical antenna having an indirect coupling feed structure corresponding to  FIG. 3A  is configured so that a plurality of helical conductors are electrically connected to the feeder circuit and the ground plane, respectively, and are formed on two respective cylinders which have a diameter of 15 mm and a height of 60 mm and are disposed at an interval of 1 mm so as to occupy the same space as the space for the normal mode helical antenna of  FIG. 3A . Further, a length of the two helical conductors is designed to resonate at 74 MHz that is lower than the central frequency of the FM broadcasting frequency band when the helical conductor connected to the ground plane is not present. 
       FIGS. 3C and 3D  show reflection coefficient graphs when, of the helical conductors for the helical antenna of  FIG. 3B , one connected to the ground plane is present and is not, respectively. 
     As shown in  FIGS. 3C and 3D , it can be found that, when two radiators resonating at 74 MHz are electrically connected and electromagnetically coupled to the feeder circuit and the ground plane, respectively, as in the embodiment of the present invention, they resonate at 98 MHz. 
     In this manner, the helical radiation unit provided to the broadcasting antenna according to the embodiment of the present invention can be designed to operate at a specific frequency band in spite of increasing the length of the antenna within the restricted space, compared to the normal mode helical antenna. 
     Meanwhile, in typical normal mode helical antennas, due to the helical spring structure, the magnetic fields are added, so that the density of the magnetic field is formed so as to be relatively higher than that of the electric field, and thus the radiation efficiency is reduced. For this reason, the broadcasting antenna  100  according to the embodiment of the present invention is configured to increase the intensity of the electric field to prevent the radiation efficiency from being reduced. To this end, the top loaders  121  and  122  of the extended radiation unit  120  are electrically connected to the helical radiators  101  and  102  of the helical radiation unit  110 , having the coupling feed structure, respectively. 
       FIG. 4  is a perspective view showing the extended radiation unit of the broadcasting antenna according to the embodiment of the present invention. 
     As shown in  FIG. 4 , the extended radiation unit  120  includes the first top loader  121  that is electrically connected to the end of the first helical radiator  101  of the helical radiators  101  and  102  of the helical radiation unit  110 , the second top loader  122  that is electrically connected to the end of the second helical radiator  102  of the helical radiation unit  110 , and an extended dielectric board (without a reference numeral) on which the first and second top loaders  121  and  122  are formed. 
     In the broadcasting antenna according to the embodiment of the present invention, first connection patterns  33  are formed on the opposite surfaces of the main dielectric board  103  of the helical radiation unit  110 , respectively, and are electrically connected to the first helical radiator  101  and first top loader  121 . Thereby, a first antenna unit (without a reference numeral) is formed. Second connection patterns  33  are electrically connected to the second helical radiator  102  and the second top loaders  122 . Thereby, a second antenna unit (without a reference numeral) is formed. The first antenna unit and the second antenna unit are coupled, so that the broadcasting antenna operates at a double frequency band according to a coupled amount as described below. 
     In the embodiment of the present invention, a relatively high frequency of two frequencies is designed to fall within the FM broadcasting frequency band of  FIGS. 3A to 3D . The antenna in which the two antenna units are coupled operates at a frequency band that is higher than a frequency corresponding to a length of each antenna unit, as described in  FIGS. 3A to 3D . As such, the broadcasting antenna according to the embodiment of the present invention increases the antenna length at a specific frequency band to improve the bandwidth, and thus improves the radiation efficiency. Further, since AM broadcasting antennas generally operate at a frequency of a long wavelength, it is difficult to tune the frequency in the antenna for a vehicle. However, the broadcasting antenna according to the embodiment of the present invention is designed to receive such a long wavelength frequency. Thus, the broadcasting antenna according to the embodiment of the present invention operates at a double frequency band of an AM broadcasting frequency band from 500 KHz to 1.7 MHz and an FM broadcasting frequency band from 88 MHz to 108 MHz. 
     Hereinafter, the extended radiation unit of  FIG. 4  will be described in greater detail with reference to  FIGS. 5 to 7 . 
       FIG. 5  is a schematic view showing a configuration of the extended radiation unit of  FIG. 4 , and  FIG. 6  is a schematic plane view showing top loaders installed on the extended radiation unit of  FIG. 5 . 
     As shown, in the embodiment of the present invention, the extended dielectric board constituting the extended radiation unit  120  is made up of an extended common dielectric board  123 , on opposite surfaces of which parts of the first and second top loaders  121  and  122  are coupled and formed in the lengthwise direction (second direction) of the main board  1 , and a plurality of extended independent dielectric boards  124 , on first surfaces of which the other parts of the first and second top loaders  121  and  122  continue to be formed in a direction (third direction) opposite to a direction in which the parts of the first and second top loaders  121  and  122  are formed, in order to reduce the entire size of the antenna within a restricted space. 
     Here, a length D by which the first and second top loaders  121  and  122  are coupled on the opposite surfaces of the common dielectric board  123  is adjusted. That is, a coupled amount is adjusted to control the radiation efficiency. 
       FIG. 7  is an equivalent circuit showing a band stop filtering unit constituting the top loaders of the extended radiation unit of  FIG. 6 . 
     The broadcasting antenna  100  according to the embodiment of the present invention is configured to form a band stop filter  11  using at least one LC resonant filter made up of a chip capacitor and a chip inductor in order to reduce the entire size of the antenna within a restricted space, and an impedance matching element  12  using a chip capacitor. 
     Here, when a plurality of interference signals are present, a plurality of band stop filter  11  are formed in series so as to have one-to-one correspondence to an operating frequency of the interference signal operating a different frequency band, and the LC resonant filter may be formed as a single low pass filter that passes only a frequency band of 108 MHz or less so as to be able to pass only the frequency band at which the broadcasting antenna according to the embodiment of the present invention operates. 
       FIG. 8  is a graph showing a result of comparing radiation efficiencies of the normal mode helical antenna of  FIG. 3A  and the broadcasting antenna according to the embodiment of the present invention at an operating frequency band having the same resonant frequency of 98 MHz in terms of an average of insertion losses. 
     As shown, at the operating frequency band of 98 MHz, about −72 dB is improved to about −64 dB, and thus it can be found that the broadcasting antenna having the helical radiation unit made up of the two helical radiators having the coupling feed structure are relatively improved in radiation efficiency compared to the normal mode helical antenna having a single helical conductor. Thus, the radiation efficiency is improved at a relatively high frequency band of the double frequency band at which the first and second antenna units are coupled and operated. 
     In this manner, the broadcasting antenna according to the embodiment of the present invention includes the helical radiation unit that is made up of the plurality of helical radiators and has the coupling feed structure, and the extended radiation unit made up of the plurality of top loaders that are electrically connected to the ends of the plurality of helical radiators, and each includes at least one band stop filtering unit and a plurality of conductive patterns between which the band stop filtering unit is disposed. Thereby, the broadcasting antenna can be made small within a restricted space, operate at a specific frequency band in spite of an increase in length, improve the radiation efficiency, and prevent the signal interference. 
       FIG. 9  is a perspective view showing a shark fin antenna apparatus having the broadcasting antenna according to another embodiment of the present invention, and  FIG. 10  is a side view showing the shark fin antenna apparatus shown in  FIG. 9 . 
     As shown, the shark fin antenna apparatus according to another embodiment of the present invention includes a broadcasting antenna  100  for a vehicle, a mobile communication antenna  200 , and a circularly polarized ceramic patch antenna  300  for the vehicle. 
     In the other embodiment, the broadcasting antenna operates at an AM broadcasting frequency band from 500 KHz to 1.7 MHz and at an FM broadcasting frequency band from 88 MHz to 108 MHz. The mobile communication antenna operates at a cellular frequency band from 824 MHz to 894 MHz and at a US PCS frequency band from 1.850 GHz to 1.990 GHz. The circularly polarized ceramic patch antenna operates at a digital satellite radio frequency band from 2.332 GHz to 2.345 GHz. 
     In detail, the broadcasting antenna  100  includes a helical radiation unit  110  which is made up of a plurality of helical radiators  101  and  102  that are electrically connected to a feeder circuit and a ground plane of a main board  1 , are formed in an upward direction (first direction) of the main board  1 , and are coupled apart from each other and which have a coupling feed structure, and an extended radiation unit  120  which has a plurality of top loaders  121  and  122  that are electrically connected to ends of the helical radiators  101  and  102 , are formed in a lengthwise direction (second direction) of the main board  1 , and are coupled to each other. Each of the top loaders  121  and  122  includes at least one band stop filtering unit  10  and a plurality of conductive patterns  31  between which the band stop filtering unit  10  is disposed. Detailed description of configurations having the same characteristics as the configurations repeated in  FIGS. 1 to 8  will be omitted. 
     In the broadcasting antenna  100  according to the other embodiment of the present invention, the first band stop filtering unit  10  is preferably made up of three band stop filters  11  that are formed in series so as to correspond to the frequency bands at which the mobile communication antenna  200  and the circularly polarized ceramic patch antenna  300  operate in order to remove interference signals. 
     Further, to prevent the conductive patterns  31  from serving as antenna radiators, the conductive patterns  31  constituting each of the top loaders  121  and  122  are each formed at a shorter length than λ/8 of an operating frequency within a relatively highest frequency band of the frequency bands at which the mobile communication antenna  200  and the circularly polarized ceramic patch antenna  300  operate, i.e. for the digital satellite radio frequency band of the circularly polarized ceramic patch antenna  300 . 
     The mobile communication antenna  200  is formed in an upward direction of the main board  1 , includes at least one second band stop filtering unit  20  and a plurality of conductive patterns  32  between which the second band stop filtering unit  20  is disposed on one side of a dielectric board  103 , on opposite upper surfaces of which the top loaders  121  and  122  constituting the extended radiation unit  120  of the broadcasting antenna  100  are partly disposed, and has a P shape. 
     Further, the circularly polarized ceramic patch antenna  300  includes a patch antenna  310  at a predetermined position on the main board  1  on which the broadcasting antenna  100  and the mobile communication antenna  200  are located, and an extended ground  320  that is formed of a metal conductor having the same shape as the patch antenna  310  and is electrically connected with the ground plane. 
     Hereinafter, the shark fin antenna apparatus according to the other embodiment of the present invention will be described in greater detail with reference to  FIGS. 11 to 14 . 
       FIG. 11  schematically shows a mobile communication antenna installed on the shark fin antenna apparatus of  FIG. 9  when viewed from the front and rear.  FIG. 12  is an equivalent circuit showing a second band stop filtering unit installed on the mobile communication antenna of  FIG. 11 . 
     As shown, the mobile communication antenna  200  installed on the shark fin antenna apparatus according to the other embodiment of the present invention is formed in a P-shaped antenna pattern on one side of the dielectric board  103  including the at least one second band stop filtering unit  20  that removes interference signals occurring when the broadcasting antenna  100  operates, and the conductive patterns  32  between which the second band stop filtering unit  20  is disposed, and includes a feeder pattern  201  that is electrically connected with the feeder circuit of the main board  1  on one side of the conductive pattern  32  adjacent to the main board  1  among the conductive patterns  32 , and a ground pattern  202  that is electrically connected to the ground plane of the main board  1 . 
     Here, the band stop filtering unit  20  installed on the mobile communication antenna  200  is designed as a single high pass filter  21  that passes only signals of a frequency band higher than the frequency band at which the broadcasting antenna  100  operates, and uses an LC resonant filter made up of a chip capacitor and a chip inductor in order to reduce the entire size of the antenna within a restricted space. The conductive patterns  32  provided to the mobile communication antenna  200  are each formed at a shorter length than λ/8 of an FM broadcasting operating frequency within a relatively high frequency band of the double frequency band at which the broadcasting antenna  100  operates in order to prevent the conductive patterns  32  from serving as the antenna radiators. 
     In this way, the shark fin antenna apparatus according to the other embodiment of the present invention is provided therein with the mobile communication antenna that includes the second band stop filtering unit removing the interference signals generated by the broadcasting antenna disposed adjacent thereto and the conductive patterns between which the second band stop filtering unit is disposed, and that improves the radiation efficiency. 
       FIG. 13  is a schematic view showing a configuration of a circularly polarized ceramic patch antenna installed on the shark fin antenna apparatus of  FIG. 9 , and  FIG. 14  is an exploded perspective view showing the circularly polarized ceramic patch antenna of  FIG. 13 . 
     As shown, the circularly polarized ceramic patch antenna  300  includes: a patch antenna unit  310  having a dielectric  311  through which a first feeder hole  301  is bored and which is formed of a ceramic, a patch radiator  312  that is formed of a quadrilateral metal thin film, diagonally opposite corners of which are partly chamfered for circular polarization, and that is formed on the dielectric  311 , a main ground  313  through which a second feeder hole  302  is bored at a position corresponding to the first feeder hole  301  so as to be greater in diameter than the feeder hole  301  and which is formed of a metal thin film placed under the dielectric  311 , and a feeder pin  314  that connects the patch radiator  312  and the feeder circuit on the main board  1  through the first and second feeder holes  301  and  302 ; and an extended ground  320 , through which a third feeder hole  321  is bored so as to correspond to the second feeder hole  302 , which is formed under the patch antenna unit  310 , which has a predetermined thickness, which is formed of a metal conductor having a shape which is the same as a shape of the patch antenna unit  310 , and which is electrically connected to a ground plane formed on the main board  1 . 
     In detail, among the components of the patch antenna unit  310 , the patch radiator  312  is formed of a quadrilateral metal thin film, opposite corners of which are partly chamfered to provide the circular polarization, and the main ground  313  is formed of a metal thin film on a bottom surface of the dielectric  311 . The extended feeder  320  has a predetermined thickness, and is formed of a metal conductor having the same shape as the patch antenna unit  310 . Here, the circular polarization formed at the patch radiator  312  of the patch antenna unit  310  is preferably left-hand circular polarization (LHCP) suitable for the reception of digital satellite radio broadcasting in North America. 
     Further, the dielectric  311 , the main ground  313 , and the extended ground  320  have first to third feeder holes  301 ,  302 , and  321 , and the feeder pin  314  for electrical connection with the patch radiator  312  is inserted into the feeder holes. Thus, the feeder pin  340  is electrically connected with the patch radiator  312 . Thereby, a feed signal applied from the feeder circuit formed on the main board  1  is transmitted to the patch radiator  312 . In this case, the second and third feeder holes  302  and  303  formed in the main ground  313  and the extended ground  320  are preferably greater in diameter than the first feeder hole  301  such that the feeder pin  314  having a rod shape can be insulated from the main ground  313  and the extended ground  320 . 
     On the other hand, the extended ground  320  is provided below the patch antenna unit  310 , and interacts with the main ground  313  of the patch antenna unit  310  by forming an electrical connection with the ground plane formed on the main board  1 . Thereby, a null point generated between the patch radiator  312  of the patch antenna unit  310  and the ground plane is reduced. 
     Further, in the other embodiment of the present invention, the dielectric  311  of the patch antenna unit  310  is formed of a ceramic having permittivity of 15 and a height of 4 mm. The dielectric  311  may be formed of one of various ceramics having permittivity between 4.0 and 110. 
     Generally, the permittivity of ceramics covers a very wide range compared to materials used as conventional dielectrics, and the ceramics are very high in stability in terms of being able to resist changes in temperature, and are suitable for making the patch antenna light in weight and small in size. 
     In the other embodiment of the present invention, the main ground  313  of the patch antenna unit  310  is provided across the entire bottom surface of the dielectric  311 . The patch antenna unit  310  includes the rod-shaped feeder pin  314 . The feeder pin  314  is inserted into the feeder holes  301  and  302  formed in the dielectric  311  and the main ground  313 , and is electrically coupled with the patch radiator  312 , so that a desired impedance characteristic can be properly changed by adjusting its position. Here, the diameter of the feeder pin  314  corresponds to the diameter of the first feeder hole  301  formed in the dielectric  311 . 
     In the other embodiment of the present invention, the thickness d of the extended ground  320  formed under the patch antenna unit  310  is adjusted, so that the radiation efficiency of a specific frequency band at which the patch radiator  312  of the patch antenna unit  310  operates can be adjusted. 
     Further, because of a field effect generated between the patch radiator  312  of the patch antenna unit  310  and the ground plane formed on the main board  1 , the extended ground  320  is preferably formed so that the thickness thereof is between 0.03λ and 0.2λ of an operating frequency such that the directivity of a radiation pattern formed in a direction parallel to the ground plane is improved. In the other embodiment of the present invention, the circularly polarized ceramic patch antenna reduces the null point by adjusting the thickness of the extended ground, so that the antenna gain thereof is increased by more than 1 dB. 
     In this manner, the shark fin antenna apparatus according to the other embodiment of the present invention is provided therein with the circularly polarized ceramic patch antenna in which the extended ground is formed under a patch antenna, has a predetermined thickness, is formed of a metal conductor having the same shape as the patch antenna unit, and is electrically connected to a ground plane formed on a main board. The thickness of the extended ground can be adjusted, so that it is possible to adjust the radiation efficiency at a specific frequency band. Thus, the directivity of a radiation pattern formed in a direction parallel to the ground plane is improved, and the null point caused by the field effect is reduced to increase the antenna gain. 
       FIGS. 15 to 20  show results of comparing antenna characteristics before and after the other embodiment of the present invention is applied at operating frequency bands of 859 MHz, 1920 MHz, and 2345 MHz. 
       FIGS. 15 and 16  correspond to the comparison of antenna characteristics of the mobile communication antenna that operates at an operating frequency band of 859 MHz. It can be found that both the radiation pattern biased in a direction of 270° and the radiation efficiency are improved. 
       FIGS. 17 and 18  correspond to the comparison of antenna characteristics of the mobile communication antenna that operates at an operating frequency band of 1920 MHz. It can be found that the null point generated in directions of 0° and 180° is improved. 
       FIGS. 19 and 20  correspond to the comparison of antenna characteristics of the circularly polarized ceramic patch antenna that operates at an operating frequency band of 2345 MHz. It can be found that both the null point generated in the direction of about 0° and the radiation efficiency are improved. 
     As described above, the shark fin antenna apparatus according to the other embodiment of the present invention includes: the broadcasting antenna that includes the helical radiation unit having the coupling feed structure, and the extended radiation unit made up of the plurality of top loaders that are electrically connected to the ends of the plurality of helical radiators and each include at least one band stop filtering unit and a plurality of conductive patterns between which the band stop filtering unit is disposed, and that can be made small within a restricted space, operate at a specific frequency band in spite of an increase in length, improve the radiation efficiency, and prevent the signal interference; the mobile communication antenna that includes the second band stop filtering unit removing the interference signals and the conductive patterns between which the second band stop filtering unit is disposed, and that improves the radiation efficiency; and the circularly polarized ceramic patch antenna in which the extended ground is formed under a patch antenna, has a predetermined thickness, is formed of a metal conductor having the same shape as the patch antenna unit, and is electrically connected to a ground plane formed on a main board, and in which the thickness of the extended ground can be adjusted to control the radiation efficiency at a specific frequency band. 
     While the embodiment of the present invention has been described for illustrative purposes, it is apparent to those skilled in the art that various modifications, additions, and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.