Abstract:
The present invention relates to a multiple band-type antenna and method of producing the same. In the present invention, a connector member formed by cutting a cylindrical metallic rod and a first helical antenna are integral through a connection member. A space forming an impedance transformer is formed at the connection member for thereby widening a band region based on a series inductance effect. A helical antenna and a whip antenna are additionally installed at a center of the dielectric surrounding the inner and outer sides of the first helical antenna and the connection member for thereby enhancing an efficiency of the antenna by overcoming the unbalance problems encountered in the conventional art.

Description:
TECHNICAL FIELD OF THE INVENTION 
   This application is a 371 of PCT/KR02/01212 Jun. 25, 2002. 
   The present invention relates to a multiple bands type antenna and a method for producing the same, and in particular to a multiple bands type antenna and a method for producing the same in which a connector and a helical antenna get integral using a connection member by cutting a cylindrical metal rod, and an impedance transformer is formed in such a manner that a certain space is formed in the connection member. 
   BACKGROUND OF THE INVENTION 
   In a general feeding structure of a conventional small-sized antenna used in wireless communications, a coaxial line is directly brought into contact with an antenna to perform feeding. For monopole antennas, a + part of a coaxial line is brought into contact with an antenna to perform feeding. For dipole antennas, + and − parts of a coaxial line are brought into contact with an antenna to perform feeding. 
   These methods cause an unbalance condition between feeding lines of an antenna, so impedance matching becomes quite difficult. Additionally, a contact point between the antenna and the feeding line frequently varies, so the characteristics of the antenna are not constant, thus reducing the efficiency of the antenna. 
   As depicted in  FIG. 1 , U.S. Pat. No. 4,772,895 circular plateloses an antenna  500  that broadens the frequency response. The antenna  500  includes a feed port  550  having a signal feed portion and a ground portion, a first helical antenna element  520  having opposed ends and exhibiting a first pitch and a second electrical length, one end of the first helical antenna element  520  being coupled to the signal feed portion of the feed port, and a second helical antenna element  540  having opposed ends and exhibiting a second pitch and a second electrical length. 
   The second helical antenna element  540  is coaxially wound around a portion of the first helical antenna element  520 , one end of the second helical antenna element  540  is coupled to the ground portion of the feed port  550 , and the second pitch is equal to approximately ½ of the first pitch and the second electrical length is equal to approximately ⅓ of the first electrical length. 
   The antenna  500  is provided with a cylindrical spacer means  530  that is coaxially situated between the first and second helical antenna elements  520  and  540  to electrically insulate the first and second helical antenna elements  520  and  540 . The spacer means  530  is sufficiently thin such that the first helical antenna element  520  is tightly coupled to the second helical antenna element  540  so as to broaden the frequency response exhibited by the first helical antenna element  520 . 
   In the conventional antenna, the spacer means is situated between the first and second helical antenna elements, and is used to ground the antenna elements. The conventional antenna is problematic in that it cannot overcome the unbalance condition that is a problem in the conventional antenna, thus causing low efficiency, and it is difficult to miniaturize. 
   With respect to the unbalance condition, helical antennas are chiefly classified into normal mode antennas and axial mode antennas. The case where the circularly shaped circumference of the helical antenna is considerably smaller than a wavelength corresponding to a working frequency falls under normal mode. Generally, helical antennas used in wireless communications devices have normal mode. 
   The characteristics of the normal mode helical antenna are that the characteristic impedance is considerably large and the radiation resistance value corresponding to actual radiation power is small. Accordingly, the input impedance value is considerably large in total and considerably different from the output impedance, 50 Ω, so the reflection loss is increased. This is the inherent unbalance condition of the conventional helical antenna that is used as a general wireless communications receiving antenna. 
   As illustrated in  FIG. 2 , U.S. Pat. No. 5,661,495 circular plateloses an antenna device  200  having circuits  230  for transmitting and/or receiving radio signals as well as a chassis  250  and a feeding point providing the electrical coupling of the antenna device to the communication equipment, which includes a hollow helical antenna  210  fixed externally on the chassis  250  and an antenna rod  220  slidable through the helical antenna  210 , the helical antenna being coupled constantly via the feeding point to the circuits  230 . 
   Meanwhile, the bandwidth of the helical antenna  210  is increased, a tuned ground surface is arranged near the feeding point, a direct Galvani electrical contact is not formed, and the ground surface is coupled to the protective earth of a communications device and can catch mirror current. 
   In the conventional antenna device, when the antenna rod is extended from a housing, the antenna rod and the helical antenna are coupled in parallel to the circuits  230 . When the antenna rod  220  is retracted into the chassis  250 , only the helical antenna is coupled to the circuits  230 . 
   Meanwhile, a circuit equivalent to the case where a helical antenna is installed in a general cylindrical structure chiefly consists of a feeding part and the parallel resonance parts of L and C. This conventional helical antenna reduces the length of the conventional monopole antenna but has the same resonant frequency as the conventional monopole antenna. In this case, the Q value is increased due to the parallel resonance of L and C, so a band of frequencies is narrowed. 
   Accordingly, with reference to a graph showing the electrical characteristics of a conventional helical antenna in Voltage Standing Wave Ratios (VSWRs) and a Smith Chart showing impedance measurement data, as shown in  FIGS. 4   a  and  4   b , as the VSWR value is increased and the impedance value is away from the center of the Smith Chart, the reflection loss of the antenna is increased and the bandwidth of the antenna is narrowed. 
   The bandwidths of the conventional antennas having structures shown in  FIGS. 1 and 2  are each defined as a band of frequencies having a VSWR value equal to or less than 2. Accordingly, the conventional antennas each have a VSWR value ranging from 5 to 18 and the impedance value of the Smith Chart is considerably away from a value of 50 Ω situated at the center of the Smith Chart, so it can be appreciated that the reflection loss value of the antenna increases and, therefore, the conventional antennas each have a relatively narrow band of frequencies. 
   Additionally, the conventional antenna is problematic in that the efficiency of the conventional antenna is deteriorated because the unbalance condition that is a problem in the conventional antenna is not overcome. 
   SUMMARY OF THE INVENTION 
   Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a multiple band-type antenna and method of producing the same, which can improve the efficiency of the antenna by overcoming an unbalance condition that is a problem in the conventional antenna, and can immediately cope with frequency variation resulting from various services because the antenna can accommodate various frequencies. 
   In order to accomplish the above object, there is provided a multiple bands type antenna that comprises a connector having threads on its outer surface; a circular plate formed on an upper surface of the connector; a connection member that is formed on an upper surface of the circular plate and has a space forming an impedance transformer; a first helical antenna formed at an end of the connection member wherein said first helical antenna is integrally formed based on a cutting process of a cylindrical metallic rod; a dielectric having a center passing an inner side of the first helical antenna and an outer side of the connection member; and a covering member insert-molded on an outer surface of the first helical antenna. 
   In addition, the present invention provides a method of producing a multiple band-type antenna, comprising the 1st production step of forming a connector by threading a circumferential surface of a cylindrical metallic rod having a certain length and a certain diameter and forming a processed portion machined to be hollow above the connector; the 2nd production step of forming a connection member having a space at a position where the connector and the processed portion are positioned near each other; the 3rd production step of forming a first helical antenna element by forming a helical shape from a position spaced apart from the space of the connection member; the 4th production step of disposing a dielectric element arranged inside the first helical antenna element formed by the 3rd production step, formed to be hollow, and leaked out of the connection member having the space and the first helical antenna element to surround the connection member; and the 5th production step of insert-molding a covering member outside the first helical antenna element. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIGS. 1 and 2  are sectional views showing the structures of conventional antennas; 
       FIG. 3  is a circuit equivalent to the structure in which a helical antenna element is mounted in a cylindrical structure; 
       FIG. 4   a  is a graph showing electrical characteristics measured in VSWRs in the case where a helical antenna element is mounted in a cylindrical fixing means, and  FIG. 4   b  is a Smith Chart showing impedance measurement data in the case where the helical antenna element is mounted in the cylindrical fixing means; 
       FIG. 5   a  is a view showing a method of producing a multiple band-type antenna to which the technology of the present invention is applied, and  FIG. 5   b  is a view showing another method of producing the multiple band-type antenna; 
       FIG. 6  is a perspective view showing the structure of the antenna of the present invention; 
       FIG. 7  is a cross sectional view showing an engaged structure of a connection member and a dielectric that are important elements, of the present invention; 
       FIG. 8  is an equivalent circuit of a structure that a connection member and a first helical antenna are integral in  FIG. 7 ; 
       FIG. 9   a  is a graph that an electrical characteristic of a structure that a connection member and a helical antenna are integral in  FIG. 7  wherein the characteristic is measured based on a VSWR; 
       FIG. 9   b  is a Smith chart showing an impedance measurement data of a structure that a connection member and a first helical antenna are integral; 
       FIGS. 10   a  to  10   d  are sectional views showing antennas in accordance with other embodiments of the present invention; 
       FIG. 11   a  is a graph of a structure that a second helical antenna is installed in a structure that a connection member and a first helical antenna are integral wherein the characteristic is measured based on a VSWR; 
       FIG. 11   b  is a Smith chart showing an impedance measurement data after a second helical antenna is installed in a structure that a connection member and a first helical antenna are integral; 
       FIG. 12   a  is a graph showing an electrical characteristic based on a VSWR measurement after a third helical antenna is installed in a structure that a second helical antenna is installed; and 
       FIG. 12   b  is a Smith chart showing an impedance measurement data after a third helical antenna is installed in a structure that a second helical antenna is installed. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   An embodiment of the present invention will be described in detail with reference to the attached drawings below. 
     FIG. 5   a  is a view showing a method of producing a multiple band-type antenna to which the technology of the present invention is applied. Referring to this drawing, a connector  10  is formed by externally threading the circumferential surface of a cylindrical metallic rod having a certain length and a certain diameter and a workpiece is processed to have a hollow processed portion  12  above the connector  10  through the 1st production step S 1 . A connection member  14  having a space  13  is formed at a position where the hollow processed portion  12  formed through the 1st production step S 1  and the connector  10  are positioned near each other through the 2nd production step S 2 . 
   Meanwhile, a first helical antenna element  15  is formed to have a helical shape from a position spaced apart from the space  13  of the connection member  14  through the 3rd production step S 3 . A dielectric element  20  is formed by being disposed inside the first helical antenna element formed by the 4th production step, formed to be hollow, and leaked out of the connection member  14  having the space  13  and the first helical antenna element  15  to surround the connection member  14 . 
   After the dielectric element  20  is formed, the production of the antenna is completed by the 5th production step of insert-molding a covering member  30  out of the first helical antenna element  15 . 
   As illustrated in  FIG. 5   b , in another method of the present invention, a connector  10  is formed by externally threading the circumferential surface of a cylindrical metallic rod having a certain length and a certain diameter and a workpiece is processed to have a hollow processed portion  12  above the connector  10  through the 1st production step S 1 . A first helical antenna element  15  is formed by fabricating the processed portion  12  to have a helical shape through the 3rd production step S 3 . Thereafter, a connection member  14  having a space  13  is formed at a position near an end of the first helical antenna element  15  integrated with a circular plate  17 . 
   A dielectric element  20  is formed by being disposed inside the first helical antenna element formed by the 3rd production step, formed to be hollow, and leaked out of the connection member  14  having the space  13  and the first helical antenna element  15  to surround the connection member  14 . 
   After the dielectric element  20  is formed, the production of the antenna is completed by the 5th production step of insert-molding a covering member  30  outside the first helical antenna element  15 . 
   In the meantime, for other embodiments of the present invention, there can be employed a multiple band antenna producing method of disposing a second helical antenna element  40  inside a dielectric element  20  formed by a 3rd production step before insert-molding a covering member  30  as shown in  FIG. 10   a , and a multiple band antenna producing method of disposing a whip antenna  50  after insert-molding a covering member  30  as shown in  FIG. 10   b.    
   For other embodiments of the present invention, there can be employed a method of coating the outer surface of a second helical antenna element  40  arranged inside a first helical antenna element  15  with a dielectric element, and a method of arranging a second helical antenna element  40  and arranging a whip antenna  50  after insert-molding a covering member  30  as shown in  FIG. 10   c , or inserting a third helical antenna element  60  into one end of a whip antenna  50  as shown in  FIG. 10   d.    
   Additionally, the assembly time of the antenna may be reduced and the convenience of the production of the antenna may be improved by changing the covering member  30  made by insert-molding to a cap structure. 
   The antenna fabricated by the above-described methods can improve the efficiency of the antenna by overcoming the unbalance condition that is a problem in the conventional antenna, and can immediately cope with the variation of a frequency resulting from various services because the antenna can accommodate various frequencies. 
   Meanwhile, in another method of the present invention, the sequence of the former method in which the 3rd production step S 3  is performed after the 2nd production step S 2  may be changed to a sequence in which the 2nd production step S 2  is performed after the 3rd production step S 3 . The reason for this is that the sequence of production may be determined depending upon the convenience of production. 
   The structure of the multiple band-type antenna produced by the production method of the present invention is described below. 
     FIG. 6  is a perspective view showing the structure of the antenna to which the technology of the present invention is applied. Referring to this drawing, in the multiple band-type antenna  1  to which the technology of the present invention is applied, a disk  17  is integrated with an externally threaded connector  10 , a connection member  14  provided with a space  13  is formed on the upper surface of the circular plate  17 , a first helical antenna element  15  is integrally formed from the upper end of the connection member  14 , and a dielectric element  20  is installed to be inserted into the first helical antenna element  15  and formed to be hollow. 
   As shown in  FIGS. 5 to 7 , a dielectric element  20  is inserted into the first helical antenna element  15 , formed to be hollow, and leaked between the connection member  14  and the base of the first helical antenna element  15  to surround the connection member  14 , and a covering member  30  is insert-molded outside the first helical antenna element  15 . 
   In the meantime, the reason why the dielectric element  20  is formed to leak to a position where the connection member  14  and the first helical antenna element  15  begin and to surround the connection member  14  is to prevent the material of the covering member  30  from entering and filling the space  13  constituting the impedance transformer. 
   In an operation and effect of an antenna according to the present invention having a single band as shown in  FIGS. 5   a  and  5   b , a connector  10  having threads on an outer surface is fixedly installed at a housing, and a circular plate  17  is installed to prevent deflection. 
   In addition, a certain space  13  formed between the first helical antenna  15  and the circular plate  17  in such a manner that a part of the connection member  14  is cut acts as an impedance transformer. 
   Impedance varies depending upon the length of the first helical antenna element  15  and the bandwidth is generally determined by the structure, so the capacitive component of the helical antenna element has wide-band characteristics by the deformation of the feeding part in an early stage of impedance matching. 
   Actually, the increase of a series inductance effect has the same meaning as the decrease of a series capacitance effect occurring between the impedance transformer and the helical antenna that generally occurs in a helical antenna. 
   Accordingly, it can be appreciated that resonance is generated in a space. Results according to the above-described structure are described below. 
   When the resonance circuit of the antenna generates parallel resonance, a Q value (the quality factor of a reactance element or resonance circuit having losses) considerably increases, so bandwidth thereof considerably decreases. 
   However, in the present invention, when the structure is converted into a distributed constant circuit and input impedance viewed at a feeding point is caused to generate series resonance, a desired bandwidth can be achieved over a relatively wide band of frequencies. 
   Meanwhile, the reason why parallel resonance, which is a general characteristic, is transformed to series resonance through the use of an impedance transformer is that the antenna is caused to have a pure resistance value by compensating for an inherent capacitance value of the helical antenna through the use of a structure. 
   In this case, the parallel resonance of C of the parallel resonance part and the impedance transformer and L of the helical antenna element is exhibited by inserting the impedance transformer, which is equivalent to a parallel structure of a small R and a large C, between a feeding part and a parallel resonance part as shown in  FIG. 8 , so a frequency neighboring the center frequency of the dual resonance becomes the frequency of the serial resonance. 
   Accordingly, the frequency and the gain are all improved due to the resonance of the neighboring frequency. This means that the bandwidth is broadened by compensating for the increase of a Q value resulting from the L-C parallel resonance with serial resonance. 
   In the meantime, the series resonance frequency neighboring the center frequency can be flexibly adjusted because the C value of the impedance transformer in the equivalent circuit is adjusted according to the size of the space  13 . The working bandwidth can be adjusted according to a required bandwidth regardless of the matching circuit, and can be adjusted by widening the area of the first helical antenna. 
   Meanwhile, in the antenna having a structure as shown in  FIG. 5 , a contact is formed below the structure by inserting a whip antenna  50  into a first helical antenna  13  to penetrate the central portion thereof, which changes resonance characteristics, thus obtaining the desired frequency and gain. 
   The reason for changing resonance characteristics by inserting the whip antenna  50  into the fixed structure, which forms the space with the first helical antenna  15  inserted therein, is to cause the reduction of the Q value by affecting series resonance characteristics originating in the impedance transformer and parallel resonance characteristics originating in the helical element due to a coupling effect between the whip antenna  50  and the helical antenna because the whip antenna  50  and the helical antenna are simultaneously fed. 
   Gains are compared with one another depending upon the positions of the whip antenna electrically connected to the helical antenna as follows: 
   1. Comparison of gains depending upon frequencies when the whip antenna is extended from the helical antenna 
   
     
       
             
             
             
             
             
           
             
             
             
             
             
           
         
             
                 
                 
             
             
                 
                 
               Conventional 
               Present 
               Gain 
             
             
                 
               Frequency 
               antenna 
               Antenna 
               comparison 
             
             
                 
               (MHz) 
               (dBm) 
               (dBm) 
               (dB) 
             
             
                 
                 
             
           
           
             
                 
             
           
        
         
             
                 
               822 
               −20.64 
               −19.86 
               +0.78 
             
             
                 
               851 
               −21.17 
               −21.15 
               +0.02 
             
             
                 
               867 
               −20.53 
               −20.37 
               +0.16 
             
             
                 
               898 
               −20.87 
               −20.70 
               +0.170 
             
             
                 
                 
             
           
        
       
     
   
   2. Comparison of gains depending upon frequencies when the whip antenna is retracted into the helical antenna 
   
     
       
             
             
             
             
             
           
         
             
                 
                 
             
             
                 
                 
               Conventional 
               Present 
               Gain 
             
             
                 
               Frequency 
               antenna 
               Antenna 
               comparison 
             
             
                 
               (MHz) 
               (dBm) 
               (dBm) 
               (dB) 
             
             
                 
                 
             
           
           
             
                 
               822 
               −19.31 
               −19.22 
               +0.09 
             
             
                 
               851 
               −20.53 
               −20.25 
               +0.28 
             
             
                 
               867 
               −19.56 
               −19.32 
               +0.24 
             
             
                 
               898 
               −19.93 
               −19.93 
               +0.00 
             
             
                 
                 
             
           
        
       
     
   
   Accordingly, the frequency band of the antenna may be extended by changing only a fixed structure but not the antenna and compensating for parallel resonance, which is the general characteristics of monopole and dipole antennas, with series resonance. 
   Actually, the increase of a series inductance effect has the same meaning as the decrease of a series capacitance effect that is generated between the fixed structure and the helical antenna. 
   In the general antenna, as the working frequency band thereof is broadened, the gain thereof decreases, and as the working frequency band thereof. is narrowed, the gain thereof increases. In contrast, the antenna of the present invention is significantly different from the conventional antenna in effect, in that as the frequency band thereof is broadened, the gain thereof increases, and as the frequency band is narrowed, the gain thereof decreases. 
   Meanwhile,  FIG. 10   a  is a sectional view showing another structure of a multiple band-forming antenna according to the present invention, which is formed by disposing a second helical antenna element  40  inside a dielectric element  20  with one end thereof grounded onto a circular plate  17  and the other end made free. The reason why the lower portion of the dielectric element  20  preventing a covering member from entering and filling an inner space are projected outward is that a first helical antenna element  15  and the second helical antenna element  40  are positioned inside while being prevented from coming into contact with each other. 
   In the meantime, an additional coating layer made of dielectric element may be formed around the second helical antenna element  40  disposed inside the first helical antenna element  15 . In this case, the coating layer can reliably prevent the first and second helical antenna elements  15  and  40  from coming into contact with each other. 
   The operation and effect of an antenna in which a dual-band is formed by disposing a second helical antenna element  40  inside a first helical antenna element  15 , as shown in  FIG. 10   b  in accordance with an embodiment of the present invention, are that in the case where the VSWR is two or less, the antenna has a bandwidth of 230 MHz over a band of 800 to 900 MHz and a bandwidth of 250 MHz over a band of 1800 to 1900 MHz, as shown in  FIGS. 11   a  and  11   b.    
   Meanwhile, as illustrated in  FIG. 10   c , in a structure where a second helical antenna element  40  is disposed inside the a first helical antenna element  15  and a whip antenna  50  is disposed to pass through the second helical antenna element  40 , gains are compared with one another depending upon the positions of the whip antenna electrically connected to the helical antenna as follows: 
   1. Comparison of gains depending upon frequencies when the whip antenna is extended from the helical antenna 
   
     
       
             
             
             
             
             
           
             
             
             
             
             
           
         
             
                 
                 
             
             
                 
                 
               Conventional 
               Present 
               Gain 
             
             
                 
               Frequency 
               antenna 
               Antenna 
               comparison 
             
             
                 
               (MHz) 
               (dBm) 
               (dBm) 
               (dB) 
             
             
                 
                 
             
           
           
             
                 
             
           
        
         
             
                 
               890 
               −47.72 
               −46.58 
               +1.14 
             
             
                 
               960 
               −47.69 
               −46.72 
               +0.97 
             
             
                 
               1710 
               −52.37 
               −51.89 
               +0.48 
             
             
                 
               1880 
               −53.17 
               −51.85 
               +1.32 
             
             
                 
                 
             
           
        
       
     
   
   2. Comparison of gains depending upon frequencies when the whip antenna is retracted into the helical antenna 
   
     
       
             
             
             
             
             
           
             
             
             
             
             
           
         
             
                 
                 
             
             
                 
                 
               Conventional 
               Present 
               Gain 
             
             
                 
               Frequency 
               antenna 
               Antenna 
               comparison 
             
             
                 
               (MHz) 
               (dBm) 
               (dBm) 
               (dB) 
             
             
                 
                 
             
           
           
             
                 
             
           
        
         
             
                 
               890 
               −49.69 
               −49.15 
               +0.54 
             
             
                 
               960 
               −50.52 
               −49.80 
               +0.72 
             
             
                 
               1710 
               −54.69 
               −54.34 
               +0.35 
             
             
                 
               1880 
               −56.72 
               −55.22 
               +1.5 
             
             
                 
                 
             
           
        
       
     
   
   Accordingly, it can be appreciated that the antenna having a structure according to an embodiment of the present invention has an improved bandwidth compared with the case where only the first helical antenna element is disposed. The frequency band of the antenna may be extended by changing only a fixed structure but not the antenna and by compensating for parallel resonance, which is the general characteristics of monopole and dipole antennas, with series resonance. 
   The operation and effect of an antenna in which a triple-band is formed by disposing a whip antenna element  60  through the central portion of an insert-molded covering member  30  and positioning a third helical antenna element  60  in an upper portion of-the whip antenna as shown in  FIG. 10   d  in accordance with an embodiment of the present invention are that in the case where the VSWR is two or less, the antenna has a bandwidth of 140 MHz over a band of 800 MHz to 900 MHz and a bandwidth of 700 MHz over a band of 1800 to 1900 MHz and a band of 1885 to 2200 MHz as shown in  FIGS. 12   a  and  12   b.    
   Meanwhile, gains are compared with one another depending upon the positions of the whip antenna electrically connected to the helical antenna as follows: 
   1. Comparison of gains depending upon frequencies when the whip antenna is extended from the helical antenna 
   
     
       
             
             
             
             
             
           
             
             
             
             
             
           
         
             
                 
                 
             
             
                 
                 
               Conventional 
               Present 
               Gain 
             
             
                 
               Frequency 
               Antenna 
               Antenna 
               comparison 
             
             
                 
               (MHz) 
               (dBm) 
               (dBm) 
               (dB) 
             
             
                 
                 
             
           
           
             
                 
             
           
        
         
             
                 
               824 
               −48.19 
               −47.47 
               +0.72 
             
             
                 
               894 
               −47.98 
               −47.47 
               +0.51 
             
             
                 
               1750 
               −53.21 
               −53.08 
               +0.13 
             
             
                 
               1870 
               −53.22 
               −51.75 
               +1.47 
             
             
                 
               1885 
               −59.69 
               −58.75 
               +1.25 
             
             
                 
               2200 
               −59.42 
               −58.35 
               +1.07 
             
             
                 
                 
             
           
        
       
     
   
   Comparison of gains depending upon frequencies when the whip antenna is retracted into the helical antenna 
   
     
       
             
             
             
             
             
           
             
             
             
             
             
           
         
             
                 
                 
             
             
                 
                 
               Conventional 
               Present 
               Gain 
             
             
                 
               Frequency 
               Antenna 
               Antenna 
               comparison 
             
             
                 
               (MHz) 
               (dBm) 
               (dBm) 
               (dB) 
             
             
                 
                 
             
           
           
             
                 
             
           
        
         
             
                 
               824 
               −50.65 
               −50.22 
               +0.43 
             
             
                 
               894 
               −51.05 
               −50.39 
               +0.66 
             
             
                 
               1750 
               −55.46 
               −55.04 
               +0.42 
             
             
                 
               1870 
               −54.92 
               −53.62 
               +1.3 
             
             
                 
               1885 
               −60.18 
               −59.01 
               +1.17 
             
             
                 
               2200 
               −60.07 
               −59.09 
               +0.98 
             
             
                 
                 
             
           
        
       
     
   
   Accordingly, it can be appreciated that the antenna having a structure according to another embodiment of the present invention has an improved bandwidth compared with the general antenna forming a triple band, like antennas forming a single band and a dual band described above. The frequency band of the antenna may be extended by changing only a fixed structure but not the antenna and compensating for a parallel resonance, which is the general characteristics of monopole and dipole antennas, with series resonance. 
   In the meantime, a single band and a dual band-may be generated by adjusting the size and shape of a space using an antenna generating a triple band. The present invention converts parallel resonance into series resonance by changing the space of the structure, so a certain antenna generally and parallelly resonating at its center frequency obtains a working frequency range two to three times greater than the existing one and the gain thereof is improved. 
   According to the multiple bands type antenna and method for producing the same, a connection member  14  having a certain space  13  forming an impedance transformer is integrally formed between integral helical antenna and connector. A dielectric surrounding the inner and outer portions of the helical antenna and connection member is installed. The helical antenna and whip antenna are additionally installed about an inner side of the dielectric. An unbalance problem in the conventional antenna structure is improved in the present invention, and different frequencies are satisfied. The efficiency of antenna is enhanced. It is possible to quickly cope with the movement of a center frequency due to changing service environments of an antenna.