WO1997004496A1

WO1997004496A1 - A combination of at least one helically wound coil and a carrier therefor for use in a helical antenna, and a method for the manufacture of such combination

Info

Publication number: WO1997004496A1
Application number: PCT/SE1996/000867
Authority: WO
Inventors: Håkan BERGQVIST; Magnus Tannfelt
Original assignee: Allgon Ab
Priority date: 1995-07-14
Filing date: 1996-06-28
Publication date: 1997-02-06
Also published as: SE9502610D0; AU6473196A

Abstract

In helical antenna, the combination of a helically wound coil on a carrier having a helical groove, and a method of manufacture. The helical groove is of a pre-determined pitch. The coil is located in the groove. The carrier may comprise a cylindrical core with one or more external helical grooves. Alternatively, the carrier may be a cylindrical sleeve with an internal helical groove. Still further, the carrier may include grooves both external and internal on the sleeve. The method of manufacture includes the steps of forming a wire into a helical coil, rotating the coil in the direction of its pitch, moving the free end of the coil relative to a carrier having a pre-formed groove, inserting the free end into the pre-formed groove, and then interrupting the rotation of the coil after a pre-determined number of revolutions. The coil is then cut near the first end of the carrier and connected to metallic fittings for subsequent attachment to radio circuitry.

Description

A COMBINATION OF AT LEAST ONE HELICALLY WOUND COIL AND A CARRIER THEREFOR FOR USE IN A HELICAL ANTENNA, AND A METHOD FOR THE MANUFACTURE OF SUCH COMBINATION

BACKGROUND OF THE INVENTION

The present invention concerns helical antennas and more particularly the combination of at least one helically wound coil and a carrier therefor used in such antennas, as well as a method for manufacturing such a combination.

The term carrier used herein is intended to mean a core located within a coil, a sleeve surrounding a coil, or, any other means for stabilizing and/or maintaining the original and intended dimensions of one or more wire coils.

It is known in the art of helical antennas, i.e., antennas having a substantially helically wound wire coil, to wind the coil separately, to join the coil and a fitting adapted for connection of the antenna to a radio apparatus, to introduce a temporary core into the coil and to mould an outer casing around the temporary core and the coil, to remove the temporary core, and, finally, to mould an inner core within the coil.

Evidently, this prior-art method is rather circumstantial in that it involves a large number of steps. Further, it has proven that moulding of the outer casing about the coil may lead to a loss of the intended nominal characteristics of the coil, based on its geometry as originally wound.

US-A-4 725 395 discloses a method of manufacturing an antenna including a pre-formed helically shaped wire coil. The coil is positioned and anchored within a mould. A dielectric material, such as polypropylene, is injected into the mould to fill the interior of the coil. After hardening of the dielectric material, now constituting a core and forming a unit with the coil to maintain its dimensions, the core and coil unit is placed in a second mold and an outer cover is injection molded over the core and coil unit. This prior art method tends to deform the coil in the process, and the process includes too many steps to be really profitable.

EP-A-0593185 describes a wideband antenna arrangement utilizing two antenna coils. In one embodiment the two coils are arranged concentrically, one within the other. In this case, the inner coil has a smaller diameter than the outer coil. In another embodiment the two coils are interwound and have substantially the same diameter. There is no disclosure of a core or other carrier stabilizing one or both coils.

AU Patent 22,843 discloses the use of two or more helices, which may be on a common core and may have equal or different helix diameters. An outer helix may be wound over an inner helix, either directly or separated by layers of dielectric or ferrite material.

SUMMARY OF THE INVENTION

From a productional point of view, it would be desirable to work with highly accurate antenna coils that could be used in several different antenna configurations. It is also desirable to be able to adjust the effective length of a helical coil in order to accurately adapt it to a certain frequency range.

Consequently, it is an object of the invention to provide a new combination of at least one helically wound coil and a carrier therefor for use in a helical antenna, as well as a method for its manufacture.

The present invention is directed to a combination of at least one helically wound coil and a carrier therefor. The carrier is provided with at least one pre-formed helical groove having a pre-determined pitch. The coil is located in the groove and at least one end of the coil is extending beyond a corresponding end of the carrier, or, laterally thereof.

An extending end of the coil enables length adjustment cutting as well as electrical connection of the coil such as to a printed circuit or to a fitting for connection of the antenna to a radio apparatus, such as a mobile telephone.

It is a further object of the present invention to provide a method of manufacturing a combination of at least one helically wound coil and a carrier therefor for use in a helical antenna. The method includes the steps of forming a carrier with at least one helical groove having a pre-determined diameter and a pre¬ determined pitch, and introducing a helical coil having substantially the same diameter and pitch into the at least one groove by relatively rotating the carrier and the coil.

In other words, in the case where the carrier is a core having an external groove, the coil is threaded onto the carrier. In the case where the carrier is a sleeve having an internal groove, the coil is threaded into the carrier. A further possibility exists when the carrier is a sleeve-shaped core having an external groove adapted to receive a first, outer coil, and an internal groove adapted to receive a second, internal coil. The carrier, together with the coil(s), are then to be part of the complete antenna, and will, therefore, be assembled in different ways together with the rest of the antenna components.

This method according to the present invention results in hitherto unseen possibilities of automation of the production of helical antennas. For instance, it will be possible to integrate a coil-forming machine in the production line for a helical antenna by at least partly forming, in the coil-forming machine, a wire to a helical coil having a pre-determined diameter and a pre-determined pitch, and a leading, free end, approaching the free end relative to a carrier having a helical pre-formed groove having a pre-determined diameter and a pre-determined pitch substantially corresponding to the diameter and the pitch of the coil, rotating ready-formed turns of the coil relative to the carrier, allowing the leading, free end to enter the pre-formed groove at a first end of the carrier, interrupting rotating the ready-formed turns after a pre-determined number of revolutions, and cutting the wire at the first end of the carrier. By these steps it is possible to employ a coil-forming machine wherein a wire is fed to a coil-forming apparatus and leaves the apparatus and the machine in the shape of a rotating coil, the leading free end of which is allowed to enter the pre-shaped helical groove of the carrier. Relative approach of the coil and carrier may take place due to the inherent axial growth of the coil as it is gradually formed, by axial movement of the coil after it is finished, or, by axial movement of the carrier towards the coil.

Advantageously, the rotating free end of the coil is allowed to enter the groove as soon as possible after it has been formed, thus providing support for the relatively flexible coil.

Another advantage of the present invention is that the charac¬ teristics and the performance of the antenna, which depend on the geometry of the coil (e.g. wire length, coil and wire diameter, pitch) , can be optimized in the manufacturing process. One way of achieving this is to provide an automated production line for the antenna coils with a closed-loop function, wherein the antenna characteristics are continuously measured after the cutting of the wire and the results of the measurements are fed-back for adjusting, if necessary, parameters (preferably effective electrical length of wire, i.e., the correct coil wire length for receiving and transmitting radio waves) of the coil-forming stage in the automated production line. Feed-back measurements may be performed after a step of connecting the wire to a metallic fitting and may be used for affecting parameters (such as connecting point on wire) of such a production step.

The invention will now be described in more detail, reference being made to the accompanying schematic drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view showing a helical coil and a core therefor, Fig. 2 is a perspective view showing a first step of a process for mechanized assembly of a coil and a core according to Fig. 1,

Fig. 3 is a perspective view showing a subsequent step of a process for mechanized assembly of a coil and a core according to Fig. 1,

Fig. 4 is a perspective view showing two equal helical coils and a core therefor,

Fig. 5 is a perspective view showing two different helical coils and a core therefor,

Fig. 6 is a perspective view showing a helical coil and a longitudinal section through a sleeve therefor,

Fig. 7 is a perspective view showing two different helical coils and a partial longitudinal section through a sleeve therefor,

Fig. 8 is a side-view showing a helical coil mounted on a core and having one end extending beyond an end of the coil,

Fig. 9 is a side-view showing a helical coil mounted on a core and having one end extending laterally from an end of the coil,

Fig. 10 is a side-view showing a helical coil mounted on a core and having one end connected to a metallic fitting, and, Fig. 11 is a flow-chart illustrating the feed-back of signals from antenna performance measurements to the coil- forming machine.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS In Fig. 1 is shown a cylindrical, pre-formed core 11 having at its outer periphery a helical groove 12 having a pre-determined pitch and a pre-determined bottom or inner diameter. The helical groove has an entrance 12a at a first end of the core and an exit 12b at a second end thereof. There is also shown a helically wound coil 13 having a pitch and an inner diameter substantially corresponding to the pitch and the groove bottom diameter, respectively, of the core 11. A first, or, leading end of the coil is denominated 13a and a second, or, trailing end thereof 13b. According to the present invention, a combination of a helically wound coil and a core therefor is obtained by relatively rotating the core 11 and the coil 13 such that the leading end 13a of the coil enters the entrance 12a of the core so that the coil is threaded onto the core.

In Figs. 2 and 3 are schematically shown two steps of an automatized process for mounting a helical coil on a core. A wire is formed to a coil 13 in a coil-forming machine 14 of the kind where ready-formed turns of the coil rotate as they leave the machine. Suck coil-forming machines are well known in the art. The rotational direction is indicated by an arrow A in Fig. 2. A core 11 is held by a core holder 15. The leading free end 13a of the coil is approached relative to the core as indicated by an arrow B. Such approach may be achieved by the axial growth of the coil as it gradually leaves the coil forming machine 14, or, the core holder may move the core towards the coil, or, there may be a combination of such movements.

The rotating free end 13a of the coil is allowed to enter the entrance 12a of the groove 12 and to follow the groove as shown in Fig. 3 where the leading end 13a of the coil is shown to have rotated a bit more than two turns from the entrance. At the time the coil has rotated a pre-determined number of revolutions, the rotation is interrupted and the wire is cut at the entrance 12a of the groove or at some distance therefrom to leave a portion of wire enough for electrically connecting the coil to a radio circuitry. Depending on the manner in which the core and coil combination is to be used, such end portion 13 ' may extend in the longitudinal direction beyond an end of the core as shown in Fig. 8. Alternatively, such end portion 13' ' may extend laterally from an end of the core as shown in Fig. 9. Electrical connection of the coil to a radio circuitry can be achieved as shown in Fig. 10 by fastening mechanically and contacting electrically the wire end 13b to a metallic fitting 110 to be attached to a radio circuit casing. Such fastening and contacting may be performed, e.g., by means of pressing (deforming), or, by connecting the wire end directly to a radio circuitry by means of soldering or by snap-in connection methods.

In Fig. 4 is shown a cylindrical, pre-formed core 21 having at its outer periphery a first helical groove 22 and a second helical groove 23, both being threaded in the same direction and both having substantially the same pre-determined pitch and the same pre-determined bottom or inner diameter. The helical grooves have entrances 22a, 23a, respectively, at a firεt end of the core and exits 22b, 23b, respectively, at a second end thereof, the exit 23b being concealed in Fig. 4. The entrances as well as the exits are circumferentially displaced substantially 180°. There is also shown a first helically wound coil 24 and a second helically wound coil 25, both being wound in the same direction and both having a pitch and an inner diameter substantially corresponding to the pitch and the groove bottoms diameter, respectively, of the grooves 22, 23. A respective first, or, leading end of each coil is denominated 24a, 25a, respectively, and a respective second, or, trailing end thereof is denominated 24b, 25b, respectively. According to the present invention, a combination of two helically wound coils and a common core therefor is obtained by relatively rotating the first coil 24 and the core 21 such that the leading end 24a of the coil enters the entrance 22a of the first helical groove 22 of the core so that the first coil is threaded onto the core, and by relatively rotating the second coil 25 and core 21 such that the leading end 25a of the coil enters the entrance 23a of the second helical groove 23 so that the second coil is threaded onto the core. Such threading of the coils onto the core takes place preferably one after the other, but may take place simultaneously.

In Fig. 5 is shown a cylindrical, pre-formed core 31 having at its outer periphery a first helical groove 32 threaded in a first direction, and a second helical groove 33 threaded in a second direction opposite to the first. The first groove 32 has a first pre-determined pitch and a first pre-determined bottom, or, inner diameter. The second groove 33 has a second pre-determined pitch, that is smaller than the first pitch, and a second pre-determined bottom, or, inner diameter, that is larger than the first diameter. The helical grooves have entrances 32a, 33a, respectively, at a first end of the core and exits 32b, 33b at a second end thereof. The entrances are circumferentially displaced substantially 180°. There is also shown a first helically wound coil 34 wound in said first direction and a second helically wound coil 35 wound in said second direction. The first coil 34 has a pitch and an inner diameter substantially corresponding to the pitch and the groove bottom diameter of the first groove 32. The second coil 35 has a pitch and an inner diameter substantially corresponding to the pitch and the groove bottom diameter of the second groove. A respective first, or, leading end of each coil is denominated 34a, 35a, respectively, and a respective second, or, trailing end thereof is denominated 34b, 35b, respectively. According to the present invention, a combination of two helically wound coils and a common core therefor is obtained by relatively rotating the first coil 34 and the core 31 such that the leading end 34a of the coil enters the entrance 32a of the first helical groove 32 of the core so that the first coil is threaded onto the core, and by relatively rotating the second coil 35 and the core 31 such that the leading end 35a of the coil enters the entrance 33a of the second helical groove 33 so that the second coil is threaded onto the core. Such threading of the coils onto the core takes place preferably one after the other.

In Fig. 6 is shown a pre-formed carrier in the shape of a sleeve

41 having at its inner periphery a helical groove 42. The groove

42 has a pre-determined pitch and a pre-determined bottom, or, outer diameter. The helical groove has an entrance 42a at a first end of the sleeve and an exit 42b at a second end thereof. There is also shown a helically wound coil 43 having a pitch and an inner diameter substantially corresponding to the pitch and the groove bottom diameter of the groove 42. A first, or, leading end of the coil is denominated 43a and a second, or, trailing end thereof is denominated 43b. According to the present invention, a combination of a helically wound coil and a carrier therefor is obtained by relatively rotating the coil 43 and the sleeve 41 such that the leading end 43a of the coil enters the entrance 42a of the helical groove 42 of the sleeve so that the coil is threaded into the sleeve.

In Fig. 7 is shown a pre-formed carrier in the shape of a sleeve 51 having at its outer periphery a first helical groove 52 and at its inner periphery a second helical groove 53, both being threaded in the same direction. The first groove 52 has a first pre-determined pitch and a first pre-determined bottom, or, inner diameter. The second groove 53 has a second pre-determined pitch and a second pre-determined bottom, or, outer diameter. The helical grooves have entrances 52a, 53a, respectively, at a first end of the sleeve and exits 52b, 53b at a second end thereof. The entrances are preferably but not necessarily circumferentially displaced substantially 180°. There is also shown a first helically wound coil 54 and a second helically wound coil 55. The first coil 54 has a pitch and an inner diameter substantially corresponding to the pitch and the groove bottom diameter of the first groove 52. The second coil 55 has a pitch and an outer diameter substantially corresponding to the pitch and the groove bottom diameter of the second groove 53. A respective first, or, leading end of each coil is denominated 54a, 55a, respectively, and a respective second, or, trailing end thereof is denominated 54b, 55b, respectively. According to the present invention, a combination of two helically wound coils and a common carrier therefor is obtained by relatively rotating the first coil 54 and the sleeve 51 such that the leading end 54a of the coil enters the entrance 52a of the first helical groove 52 of the core so that the first coil is threaded onto the core, and by relatively rotating the second coil 55 and the sleeve 51 such that the leading end 55a of the coil enters the entrance 53a of the second helical groove 53 so that the second coil is threaded into the sleeve. Such threading of the coils onto and into the sleeve preferably takes place one after the other, but may take place simultaneously.

It will be understood that the grooves and coils of the embodiment of Fig. 7 may be threaded in opposite directions. It will also be understood that the embodiments of the present invention described with reference to Figs. 4 - 7 may be mechanically manufactured by means of equipment similar to that shown in Fig. 2 and 3 and including one coil forming machine (embodiments according to Figs. 4 and 6) or two coil forming machines (embodiments according to Figs. 5 and 7).

It should also be understood that in the embodiments of the present invention, the core could be rotatable with respect to the coil or a combination of both core and coil may be simultaneously rotatable.

Fig. 11 schematically illustrates how parameters in the coil- forming process, particularly the length of the wire forming the coil, can be continuously adjusted. To the left of the figure can be seen how a wire enters a coil-forming machine. A coil leaves the machine and enters a measuring station where the antenna performance of the coil is measured. The result of the measurement is fed back to the coil-forming machine as an adjusting signal for adjusting, e.g., the length of the wire, i.e., the position where to cut the wire. Approved coils are fed out at the right of the figure, whereas non-approved coils are disposed of (not shown) .

Claims

1. For a helical antenna, the combination of at least one helically wound coil and a carrier therefor, wherein the improvement comprises the carrier including at lest one helical groove having a pre-determined pitch, and a coil located in the groove, at least one end of the coil extending outwardly from said carrier.

2. The combination of claim 1, wherein said at least one end of said coil extends beyond an end of said carrier.

3. The combination of claim 1, wherein said at least one end of said coil extends laterally from said carrier.

4. The combination of claim 1, wherein said carrier is a cylindrical core provided with at least one external helical groove.

5. The combination of claim 1, wherein said carrier is a cylindrical sleeve provided with an internal helical groove.

6. The combination of claim 1, wherein said carrier is a cylindrical sleeve provided with an external helical groove.

7. A method of manufacturing a combination of at least one helically wound coil and a carrier therefor for use in a helical antenna, comprising the steps of forming a carrier with at least one helical groove having a pre-determined diameter and a pre- determined pitch, and introducing a helical coil having substantially the same diameter and pitch into said at least one groove by relatively rotating the carrier and the coil.

8. A method of manufacturing a combination of a helically wound coil and a carrier therefor for use in a helical antenna, comprising the steps of, forming a wire into a helical coil, said coil having a pre¬ determined pitch and a free end,

rotating the ready-formed helical turns of said coil in the direction of its pitch,

moving said free end relative to a carrier having a helical pre-formed groove having said pre-determined pitch,

inserting said free end into said pre-formed groove at a first end of said carrier,

interrupting the rotating of said ready-formed helical turns after a pre-determined number of revolutions, and

cutting said wire near said first end of said carrier.

9. A method according to claim 8, wherein the carrier is a cylindrical core.

10. A method according to claim 8, wherein the carrier is a cylindrical sleeve.

11. A method according to claim 8, wherein the method further comprises the step of connecting by fastening mechanically and contacting electrically said wire to a metallic fitting for subsequent attachment to radio circuitry.

12. A method according to claim 8, further comprising measuring antenna characteristics of said wire after cutting thereof, feeding-back measurement signals to a preceding step of said method, and adjusting parameters of said preceding step in response to said signals in order to optimize antenna performance of the combination of a helically wound coil and a carrier therefor manufactured according to said method.