Patent Publication Number: US-6703987-B2

Title: Helical antenna

Description:
TECHNICAL FIELD 
     The present invention is related to a helical antenna, which is provided on a portable radiotelephone, such as a cellular telephone. 
     BACKGROUND ART 
     Cellular telephones have come into widespread use recently, and antennas are provided on these cellular telephones for the transmitting and receiving of telephone calls and data. As this antenna, a helical antenna, which is mounted in a fixed condition to and protrudes only slightly from the casing of the cellular telephone for convenience of carrying, is well known. 
     An example of the constitution of a prior helical antenna such as this is shown in FIG.  12 . 
     The helical antenna  100  shown in this figure is constituted from a coil element  113 , in which a coil portion  113   a  is formed; a top cover portion  110 , which is integrally molded so as to cover this coil element  113 ; and a metal base fixture  112 , to which the bottom end of coil portion  113   a  is connected electrically, and, in addition, to which the bottom end of top cover portion  110  is molded. 
     In the prior helical antenna  100  shown in FIG. 12, coil element  113  comprises an insulative main casing formed in an approximately cylindrical shape, and a helical groove formed in the peripheral surface of the main body. Coil portion  113   a  is formed inside this groove by either depositing or attaching a metallic thin film thereinto. Helical antenna  100  is made by screwing the bottom end of the coil element  113  formed in this manner onto the top part of metal base fixture  112 , and integrally molding top cover portion  110  so as to cover the entire coil element  113  and the top part of metal base fixture  112 . Then, helical antenna  100  is mounted in a fixed condition to the casing of a portable radiotelephone by screwing a screw portion  112   a  formed in the bottom part of metal base fixture  112  into a mounting fixture provided in the casing of the portable radiotelephone. 
     However, the problem with a prior helical antenna  100  was that the number of processes for making coil element  113  were numerous, and it took time to assemble the helical antenna  100 , thus causing costs to rise. Another problem was that because the helical antenna  100  was mounted in a fixed condition to the casing of a portable radio by screwing the helical antenna  100  thereto, special tools were required for mounting, and, in addition, it took time. 
     Accordingly, an object of the present invention is to provide a helical antenna, which can be assembled easily and can reduce costs, and, in addition, can be readily mounted in a fixed condition. 
     DISCLOSURE OF THE INVENTION 
     To solve for the above-mentioned problems, a helical antenna of the present invention comprises a top cover portion, which comprises an approximately cylindrical storing portion, the one end of which is closed, and on which is formed a plurality of coupling members, which extend from the bottom part; a coil portion wound in a coil shape; a coil element comprising a leading portion, which extends from one end of this coil portion; a bobbin, which supports the above-mentioned coil portion of this coil element, and in which a through-hole, through which the above-mentioned leading portion is passed, is formed approximately parallel to the central axis; a holding member, which is mounted to the bottom part of this bobbin, and is positioned on the peripheral surface thereof; and a conductive contact terminal, in which is formed press-fitting members, which are positioned on the inside of the above-mentioned through-hole. The tip of the above-mentioned leading portion, which passes through the inside of the above-mentioned through-hole, is press-fitted inside the above-mentioned press-fitting members of the above-mentioned contact terminal, the above-mentioned top cover portion is fitted by insertion to the above-mentioned bobbin, and the top part of the above-mentioned bobbin, which supports the above-mentioned coil portion, is stored inside the above-mentioned storing portion. 
     Further, in the above-mentioned helical antenna of the present invention, when the above-mentioned coupling members pass through and mate with the power supply fixture disposed in the casing, the holding member of the above-mentioned contact terminal can be electrically connected to the above-mentioned power supply fixture. 
     Furthermore, in the above-mentioned helical antenna of the present invention, the above-mentioned contact terminal comprises the above-mentioned holding member, which is formed by being bent into a U-shape, and press-fitting members comprising approximately parallelly positioned elongated plates formed by rising up from approximately the center portion of this holding member, and raised tabs can be formed on these press-fitting members so that [the contact terminal] does not slip out when inserted into the above-mentioned through-hole. 
     Furthermore, a plurality of ribs is formed on the bottom part of the above-mentioned bobbin, and the above-mentioned coupling members can be arranged between the above-mentioned ribs when the above-mentioned top cover portion is inserted into the above-mentioned bobbin. 
     Furthermore, in the above-mentioned helical antenna of the present invention, when the above-mentioned contact terminal is mounted to the bottom part of the above-mentioned bobbin, the above-mentioned holding member can be positioned inside the grooved portions formed on the surface of the above-mentioned ribs. 
     Furthermore, in the above-mentioned helical antenna of the present invention, the cross-sectional shape of the through-hole formed in the bottom part of the above-mentioned bobbin, into which the above-mentioned press-fitting members are inserted, represents an H shape, and the cross-sectional shape of the through-hole, through which the above-mentioned leading portion is passed in the above-mentioned coil element, represents an I shape, and the bottom end of the above-mentioned leading portion can be folded. 
     According to this present invention, the tip of the leading portion of the coil element, which passes through the inside of the bobbin through-hole, is press-fitted inside the press-fitting members of the contact terminal arranged inside the through-hole, and the top part of the bobbin, which supports the coil portion, is stored inside the storing portion by the top cover portion being fitted in the bobbin by being inserted therein. Thus, assembly of a helical antenna can be performed easily without using special tools, making it possible to reduce costs. 
     Further, by inserting the helical antenna into a power supply fixture disposed in the casing of a portable radiotelephone, coupling members disposed on the top cover portion mate with the power supply fixture, making it possible for the helical antenna to be mounted to the casing [of a portable radiotelephone] in a fixed condition. This enables the helical antenna to be mounted in a fixed condition to the casing [of a portable radiotelephone] easily and in a short period of time. 
     Furthermore, since the contact terminal can be formed by processing sheet metal, the coil element can be formed by processing a wire into a coil shape, and the bobbin and top cover portion can be readily formed by plastic molding, each part can be made easily, enabling the cost of the helical antenna to be reduced. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagram showing a constitution, wherein a helical antenna of an aspect of the embodiment of the present invention is applied to a portable radiotelephone; 
     FIG. 2 is a diagram showing an enlarged view of one portion of the constitution, wherein a helical antenna of an aspect of the embodiment of the present invention is applied to a portable radiotelephone; 
     FIG. 3 is a cross-sectional view showing an enlarged view of one portion of the constitution, wherein a helical antenna of an aspect of the embodiment of the present invention is applied to a portable radiotelephone; 
     FIG. 4 is an exploded assembly diagram of a helical antenna of an aspect of the embodiment of the present invention; 
     FIG.  5 ( a ) is a front view showing the constitution of a helical antenna of an aspect of the embodiment of the present invention; 
     FIG.  5 ( b ) is a bottom view showing the constitution of a helical antenna of an aspect of the embodiment of the present invention; 
     FIG. 6 is a line A—A cross-sectional view showing the constitution of a helical antenna of an aspect of the embodiment of the present invention; 
     FIG.  7 ( a ) is a top view showing the detailed constitution of the bobbin in a helical antenna of an aspect of the embodiment of the present invention; 
     FIG.  7 ( b ) is a front view showing the detailed constitution of the bobbin in a helical antenna of an aspect of the embodiment of the present invention; 
     FIG.  7 ( c ) is a bottom view showing the detailed constitution of the bobbin in a helical antenna of an aspect of the embodiment of the present invention; 
     FIG.  8 ( a ) is a line B—B cross-sectional view, showing the detailed constitution of the bobbin in a helical antenna of an aspect of the embodiment of the present invention; 
     FIG.  8 ( b ) is a line C—C cross-sectional view showing the detailed constitution of the bobbin in a helical antenna of an aspect of the embodiment of the present invention; 
     FIG.  8 ( c ) is a line D—D cross-sectional view showing the detailed constitution of the bobbin in a helical antenna of an aspect of the embodiment of the present invention; 
     FIG.  9 ( a ) is a front view showing the detailed constitution of the contact terminal in a helical antenna of an aspect of the embodiment of the present invention; 
     FIG.  9 ( b ) is a bottom view showing the detailed constitution of the contact terminal in a helical antenna of an aspect of the embodiment of the present invention; 
     FIG.  9 ( c ) is a side view showing the detailed constitution of the contact terminal in a helical antenna of an aspect of the embodiment of the present invention; 
     FIG.  9 ( d ) is a line E—E cross-sectional view showing the detailed constitution of the contact terminal in a helical antenna of an aspect of the embodiment of the present invention; 
     FIG.  9 ( e ) is a partially enlarged view showing the detailed constitution of the contact terminal in a helical antenna of an aspect of the embodiment of the present invention; 
     FIG. 10 is a diagram showing the detailed constitution of the coil element in a helical antenna of an aspect of the embodiment of the present invention; 
     FIG.  11 ( a ) is a front view showing the detailed constitution of the top cover portion in a helical antenna of an aspect of the embodiment of the present invention; 
     FIG.  11 ( b ) is a bottom view showing the detailed constitution of the top cover portion in a helical antenna of an aspect of the embodiment of the present invention; 
     FIG.  11 ( c ) is a line F—F cross-sectional view showing the detailed constitution of the top cover portion in a helical antenna of an aspect of the embodiment of the present invention; 
     FIG.  11 ( d ) is a partially enlarged view showing the detailed constitution of the top cover portion in a helical antenna of an aspect of the embodiment of the present invention; 
     FIG.  12 ( a ) is a half-sectional view showing the detailed an example of a constitution of a prior helical antenna; and 
     FIG.  12 ( b ) is a bottom view showing the detailed an example of a constitution of a prior helical antenna. 
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     A partial cutaway view of a constitution, wherein a helical antenna of an aspect of the embodiment of the present invention is applied to a portable radiotelephone, is shown in FIG. 1, an enlarged view of the cutaway portion is shown in FIG. 2, and a cross-sectional view of the enlarged cutaway portion is shown in FIG.  3 . 
     As shown in these drawings, a ring-shaped portion  3 , which protrudes in a ring shape around a through-hole formed in a radio casing  2 , is formed in the radio casing  2  of a portable radiotelephone  1 , such as a cellular telephone. Then, a power supply fixture  5  of a cylindrical shape is disposed inside the through-hole. A helical antenna  4  related to an aspect of the embodiment of the present invention is mounted by inserting the bottom part [of the helical antenna  4 ] inside this power supply fixture  5 . In other words, when the bottom part of helical antenna  4  is inserted inside power supply fixture  5 , the constitution is such that coupling members  10   a , which are formed so as to extend from the bottom part of helical antenna  4 , mate with the bottom surface of power supply fixture  5 . By forming wedge-shaped portions with sharply tapered tips at the end portions of these coupling members  10   a , step portions, which mate with the top of the wedge-shaped portions, are formed. 
     Furthermore, a contact terminal  11  is arranged around the peripheral surface of the bottom part of helical antenna  4 , and when the bottom part of helical antenna  4  is inserted inside power supply fixture  5 , contact terminal  11  comes in contact electrically with the inner surface of power supply fixture  5 . This enables helical antenna  4  to connect with a transceiving circuit embedded in the radio casing  2 . 
     Further, coupling members  10   a  are integrally formed to the top cover portion  10 , and the top cover portion  10  is fitted to the bobbin  12  by being inserted therein. Coil element  13  is supported inside bobbin  12  as shown in FIG.  3 . Coil element  13  is constituted from a coil portion  13   a  formed by being wound into a coil shape, and a leading portion  13   b  formed by bending and extending the top end of the coil portion  13   a  downward. A folded portion  13   c , which is folded upward, is formed at the tip of this leading portion  13   b , and this folded portion  13   c  is connected electrically by being press-fitted into press-fitting members  11   b  formed in contact terminal  11 . 
     Furthermore, contact terminal  11  comprises a holding member  11   d  formed by being bent into the shape of the letter  4 , and press-fitting members  11   b , which are bent so as to rise up on two sides from approximately the center portion of holding member  11   d . A plurality of raised tabs  11   c , which are raised toward the outside, are formed on press-fitting members  11   b , and when [contact terminal  11 ] is inserted into the below-described cross-sectional H-shaped insertion hole formed in bobbin  12 , the raised tabs  11   c  mate to the inner wall of the insertion hole, preventing the contact terminal  11  from uncoupling from bobbin  12 . Spring portions lie are formed in holding member  11   d  by bending the bent end portions into dogleg shapes. These spring portions  11   e  are constituted so as to form a connection by making contact with the inner surface of power supply fixture  5 . 
     Next, an exploded assembly diagram of a helical antenna  4  related to an aspect of the embodiment of the present invention is shown in FIG.  4 . 
     To assemble helical antenna  4 , first, contact terminal  11  is mounted by inserting it from the bottom end of bobbin  12 . At this time, contact terminal  11  is mounted by being rotated approximately 90° within a horizontal plane from the position shown in FIG.  4 . By so doing, press-fitting members  11   b  are inserted inside a cross-sectional H-shaped insertion hole formed approximately parallel to the central axis of bobbin  12 , and, in addition, holding member  11   d  slides into contact with the inside of rib portions  12   e  formed on the surfaces of second ribs  12   d . Then, coupling members formed on the end of holding member  11   d  mate with notched portions  12   f  formed in the top parts of second ribs  12   d . Also, the raised tabs  11   c  formed on press-fitting members  11   b  mate with the inside wall of the insertion hole. In accordance therewith, contact terminal  11  is mounted in a fixed condition in the bottom part of bobbin  12  such that it cannot come uncoupled. 
     Next, the coil element  13  is readied, and is passed through a through-hole formed approximately in the center of bobbin  12  beginning with the folded portion  13   c  formed at the bottom end of coil element  13 . In this case, because the cross-sectional shape of the through-hole is an I shape, coil element  13  is positioned relative to bobbin  12  as it passes through. Since the through-hole connects to the insertion hole, once folded portion  13   c  passes through to the bottom part of bobbin  12 , folded portion  13   c  is press-fitted between press-fitting members  11   b  of contact terminal  11 , which is mounted to the bottom part [of bobbin  12 ], and sandwiched therebetween so as not to slip out. Coil element  13  is thereby electrically connected to contact terminal  11 . At the same time, coil portion  13   a  is supported by the periphery of a round bar-shaped support portion  12   a . At this time, the bottom end of coil portion  13   a  comes in contact with the top surface of the bobbin base portion  12   b , which has a slightly larger diameter than coil support portion  12   a , and this determines the length of the coil portion  13   a.    
     Next, top cover portion  10  is fitted over bobbin  12  so as to cover bobbin  12  holding coil element  13  thereon. By so doing, the four coupling members  10   a  formed so as to extend from the bottom part of top cover portion  10  pass between first ribs  12   c  and second ribs  12   d  formed on the bottom part of bobbin  12 . Then, the top parts of first ribs  12   c  and second ribs  12   d  are press-fitted to concave portions formed in top cover portion  10 , thereby integrally mounting top cover portion  10  to bobbin  12 . Accordingly, it is possible to assemble helical antenna  4  related to an aspect of the embodiment of the present invention. At the time of this assembly, since assembly jigs and tools are not required, and, in addition, assembly is performed without using adhesives, assembly can be carried out using simple equipment. 
     A helical antenna  4  related to the present invention assembled in this manner is shown in FIGS.  5 ( a ), ( b ) and FIG.  6 . However, FIG.  5 ( a ) is a front view of helical antenna  4  related to the present invention, FIG.  5 ( b ) is a bottom view thereof, and FIG. 6 is a cross-sectional view of helical antenna  4  cut along line A—A in FIG.  5 ( b ). 
     As shown in these drawings, four coupling members  10   a  formed so as to extend from the bottom part of top cover portion  10  are respectively positioned between first ribs  12   c  and second ribs  12   d  formed on the bottom part of bobbin  12 , and holding member  11   d  of contact terminal  11  is positioned inside the grooved portions  12   e  of second ribs  12   d . Then, coupling members  11   f  broadly formed at the tips of holding member  11   d  mate with notched portions  12   f  formed in the top parts of second ribs  12   d.    
     Further, as shown in FIG. 6, leading portion  13   b  of coil element  13 , which passes through the inside of through-hole  12   g  formed approximately parallel to the central axis of bobbin  12 , passes through insertion hole  12   h , which connects to through-hole  12   g . According to this [constitution], folded portion  13   c  formed at the end of leading portion  13   b  is press-fitted between press-fitting members  11   b  formed in contact terminal  11 , which is mounted inside insertion hole  12   h . Furthermore, raised tabs  11   c , which are cut so as to raise up toward the outside from press-fitting members  11   b , are constituted so as to pierce the inner wall of insertion hole  12   h , and this affixes contact terminal  11 , which is mounted from the bottom to the bottom part of bobbin  12 , so that it cannot slip out of bobbin  12 . 
     Next, details of each of the parts, which constitute helical antenna  4  related to the present invention, will be explained. 
     FIG.  7  and FIG. 8 are diagrams showing the detailed constitution of bobbin  12 . FIG.  7 ( a ) is a top view of bobbin  12 , FIG.  7 ( b ) is a front view thereof, and FIG.  7 ( c ) is a bottom view thereof. Furthermore, FIG.  8 ( a ) is a cross-sectional view cut along line B—B of FIG.  7 ( c ), FIG.  8 ( b ) is a cross-sectional view cut along line D—D of FIG.  7 ( c ), FIG.  8 ( c ) is a cross-sectional view cut along line C—C of FIG.  7 ( c ). 
     As shown in these drawings, bobbin  12 , which is made of a synthetic resin, comprises a narrow-diameter, round bar-shaped coil supporting portion  12   a , and a slightly larger diameter cross-sectionally circular bobbin base portion  12   b , which connects to coil supporting portion  12   a . A plurality of ridges  12   k  is formed on the peripheral surface of the top part of this bobbin base portion  12   b . When the top cover portion  10  is attached, these ridges  12   k  make contact [with the top cover portion  10 ] by pressing against the inner surface of the storing portion of the top cover portion  10 . Four ribs arranged in the shape of a cross are formed on the outside surface of bobbin base portion  12   b  except for the top part. These four ribs comprise two first ribs  12   c  and two second ribs  12   d , and first ribs  12   c  and second ribs  12   d , which are formed opposite one another, are arranged approximately orthogonally. And grooved portions  12   e , on which holding member  11   d  of contact terminal  11  is positioned, are formed on the surfaces of second ribs  12   d , and wall portions  12   i  are formed on both sides of these grooved portions  12   e . Further, notched portions  12   f  are formed in the top parts of second ribs  12   d , and protruding portions  12   j  are formed at the top ends of first ribs  12   c  and second ribs  12   d , respectively. These protruding portions  12   j  attach [to the top cover portion  10 ] by fitting into concave portions formed in the top cover portion  10  when the top cover portion  10  is attached. 
     Furthermore, as shown in FIG. 8, a through-hole  12   g  and an insertion hole  12   h  are formed approximately along the central axis of bobbin  12 . As shown in FIG.  7 ( a ), the cross-section of through-hole  12   g  is an elongated rectangle in the shape of the letter I, and [through-hole  12   g ] is formed approximately in the center of coil supporting portion  12   a  and bobbin base portion  12   b . Further, insertion hole  12   h  connects to through-hole  12   g , and, as shown in FIG.  7 ( c ), its cross-section is in the shape of the letter H, and it is formed from approximately the center to the bottom of bobbin base portion  12   b . Press-fitting members  11   b  of contact terminal  11  pass through hole portions corresponding to the two vertical bars, respectively, of the letter H of insertion hole  12   h . Also, a hole portion corresponding to the horizontal bar connecting the two vertical bars of the letter H of insertion hole  12   h  is the hole portion, which extends through-hole  12   g , and leading portion  13   b  of coil element  13 , in which folded portion  13   c  is formed, passes through [this hole portion]. Furthermore, as shown in FIG.  8 ( c ), the bobbin base portion  12   b  is formed by tapering the bottom end so that it becomes narrower, and the constitution is such that penetration space is ensured when coupling member  10   a  is fitted into power supply fixture  5 . 
     Next, FIG. 9 is a diagram showing the detailed constitution of contact terminal  11 . FIG.  9 ( a ) is a front view of contact terminal  11 , FIG.  9 ( b ) is a bottom view thereof, FIG.  9 ( c ) is a side view thereof, FIG.  9 ( d ) is a cross-sectional view cut along line E—E of FIG.  9 ( c ), and FIG.  9 ( e ) is a partially enlarged view of the front view thereof. 
     As shown in these drawings, press-fitting members  11   b , which are formed in an elongated condition, are formed so as to stand facing one another from both sides of approximately the center of holding member  11   d , which is processed metal sheet formed in the shape of the letter U. Two triangular raised tabs  11   c  are formed in these press-fitting members  11   b , respectively, as shown in the figure. The tips of these raised tabs  11   c  are constituted so as to pierce the inner wall of insertion hole  12   h  of bobbin  12 . Further, spring portions  11   e , which have been bent into dogleg shapes, and wide coupling members  11   f  at the ends thereof, are formed in both side members of the U-shaped holding member  11   d . These spring portions  11   e  are the parts, which make electrical contact with the inner surface of power supply fixture  5  when helical antenna  4  is mounted to the radio casing  2 , and coupling members  11   f  are the parts, which mate to the notched portions  12   f  formed in the top parts of second ribs  12   d  of bobbin  12  when contact terminal  11  is attached to the bottom part of bobbin  12 . 
     Next, the detailed constitution of coil element  13  is shown in FIG.  10 . 
     As shown in this figure, coil element  13  is constituted from a coil portion  13   a , which is formed by winding a wire in a helical shape, and a leading portion  13   b , which is formed by bending the top end of the coil portion  13   a  so as to pass through the inside of the coil portion  13   a . Further, a folded portion  13   c  is formed by folding the bottom end of leading portion  13   b . Folded portion  13   c  is the part, which is press-fitted into press-fitting members  11   b  of contact terminal  11 , and is electrically connected to contact terminal  11 . Furthermore, because leading portion  13   b  is constituted so as to pass through the inside of coil portion  13   a , and since leading portion  13   b  and coil portion  13   a  are coupled in a high-frequency condition, coil element  13  exhibits double resonance characteristics. According to this, by mounting helical antenna  4  related to the present invention to a cellular telephone, it becomes possible to operate the cellular telephone at two different frequency bands. 
     Furthermore, when coil element  13  is attached to bobbin  12 , the bottom end of coil portion  13   a  makes contact with the top surface of bobbin base portion  12   b , thus determining the length of coil portion  13   a . This enables resonance frequency irregularities in coil element  13  to be held in check and made uniform. 
     FIG. 11 is a diagram showing the detailed constitution of top cover portion  10 . FIG.  11 ( a ) is a front view of top cover portion  10 , FIG.  11 ( b ) is a bottom view thereof, FIG.  11 ( c ) is a cross-sectional view, which cuts along line F—F of FIG.  11 ( b ), and FIG.  11 ( d ) is an enlarged view of a portion thereof. 
     As shown in these drawings, top cover portion  10  is constituted from a cylindrical cover  10   b , one end of which is closed, forming a sack-shaped storing portion  10   c , and four coupling members  10   a , which extend from the bottom end of cover  10   b . As shown in FIG.  11 ( d ), the coupling members  10   a  are constituted such that wedge-shaped portions  10   d  are formed at the ends [thereof], thereby forming coupling step portions on top of these [wedge-shaped portions  10   d].    
     These four coupling members  10   a  are integrally formed at the bottom end of cover  10   b  when the top cover portion  10  is formed via plastic molding, and slotted portions  10   e  are formed between the coupling members  10   a . First ribs  12   c  and second ribs  12   d  of bobbin  12 , respectively, pass through these slotted portions  10   e  when top cover portion  10  is inserted and affixed to bobbin  12 . Then, the top ends of slotted portions  10   e  constitute concave portions  10   f  formed in the bottom end of cover  10   b , and the protruding portions  12   j  formed in the top ends of first ribs  12   c  and second ribs  12   d  are press-fitted into these concave portions  10   f . Furthermore, by fitting top cover portion  10  to bobbin  12  by insertion, coil supporting portion  12   a , which supports coil portion  13   a , is stored in storing portion  10   c.    
     In the above explanation, helical antenna  4  is treated as a double-resonance antenna, but it can also be used as a single-resonance antenna. Further, the constitution is such that a folded portion  13   c  is formed at the bottom end of leading portion  13   b  of coil element  13 , but folded portion  13   c  does not always need to be provided. 
     In addition, as shown in FIG.  5  and FIG. 6, a helical antenna related to the present invention is assembled by fitting [the components together] without using an adhesive. Thus, when inspecting and verifying the electrical characteristics of helical antenna  4  following assembly, when these electrical characteristics need adjusting, [helical antenna  4 ] can be disassembled and adjustments can be made. Since verification inspections of electrical characteristics can be carried out following assembly, production yields can be improved. 
     Industrial Applicability 
     As explained hereinabove, the present invention is constituted such that the end of the coil element leading portion, which passes through the inside of a bobbin through-hole, is press-fitted inside press-fitting members of a contact terminal disposed inside the through-hole, and, in addition, by fitting the top cover portion to the bobbin by insertion, the top part of the bobbin, which supports the coil portion, is stored inside a storing portion. Accordingly, assembly of a helical antenna can be easily carried out without using special tools, making it possible to reduce costs. 
     Further, by inserting the helical antenna into a power supply fixture disposed in the casing of a portable radiotelephone, it becomes possible for coupling members provided on the top cover portion to mate with the power supply fixture, and for the helical antenna to be mounted in a fixed condition to the casing [of the portable radiotelephone]. This enables a helical antenna to be mounted in a fixed condition to the casing [of the portable radiotelephone] easily and in a short period of time. 
     In addition, since a contact terminal can be formed by processing a metal sheet, a coil element can be formed by processing a wire into a coil shape, and a bobbin and top cover portion can be easily formed via plastic molding, each part can be easily manufactured, enabling the cost of the helical antenna to be lowered.