JPH09102707A - Helical antenna device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize the variance in antenna radiation characteristic despite the deformation of a radiation element caused by the external force. SOLUTION: A lower coil 2c of a radiation element 2 made of a helical conductor wire is connected fixedly to a center conductor 4b of a feeding coaxial connector 4. The element 2 is covered with a heat shrinkable tube 6 in the outer radial direction of an antenna shaft 3. The element 2 and the tube 6 are stored in an antenna cover 5 made of an elastic material. When the external force is applied to the cover 5, the cover 5 is deformed and therefore the element 2 is also deformed. However, a contact or a short-circuiting is never caused between the coils 2a and 2b of the element 2 owing to the tube 6 that is held between both coils 2a and 2b. Furthermore, the change of distance is minimized between both coils.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a helical antenna device, and more particularly to a helical antenna device suitable for portable radios.

[0002]

2. Description of the Related Art A conventional helical antenna device of this type will be described with reference to the sectional view of FIG. 2A shows a steady state of the helical antenna device 1A, and FIG. 2B shows a deformed state.

A helical antenna device 1A has a radiating element 2 formed by winding a metal wire around a spiral coil as a main element. The lower coil 2c at one end of the radiating element 2 is connected and fixed to the central conductor 4b of the coaxial connelter 4. The coaxial connector 4 is a connector for supplying power to the radiating element 2, supplies a high frequency signal from a portable wireless device (not shown) to the radiating element 2, and transmits the high frequency signal received by the radiating element 2 to the above. Supply to portable radios. Radiating element 2
Emits high-frequency signals into and out of space. In the steady state of the antenna device 1A, the antenna axis 3 having the highest antenna gain is in the direction perpendicular to the spiral outer diameter of the radiating element 2 (see FIG. 2A).

The radiating element 2 is entirely covered by an elastic antenna cover 5 made of plastics or the like. The antenna cover 5 protects the radiating element 2 by fixing the cover lower part 5a which is an opening to the flange 4a which is the outer conductor of the connector 4. The antenna cover 5 is temporarily deformed when an external force is applied due to a fall of the portable wireless device, a collision with an obstacle, or the like (see FIG. 2B), but returns to its original shape when the external force is removed. (See FIG. 2A).

When the antenna cover 5 is deformed, the radiating element 2 is also deformed by being pushed by the antenna cover 5, and, for example, the n-th turn coil 2a and the (n + 1) -th turn coil from the other end (tip) of the radiating element 2. Contact with 2b or variation in spacing occurs. Such deformation of the radiating element 2 is caused by the antenna gain / frequency characteristic and the like.
This causes an undesirable variation in the antenna radiation characteristic of A.

In Japanese Utility Model Laid-Open No. 1-126710, in order to prevent the above-mentioned deformation of the radiating element 2, the antenna cover 5 is brought into contact with the outer circumference of the radiating element 2, and a plurality of antenna covers are provided inside the antenna cover 5. A technique is disclosed in which convex shapes are formed at predetermined intervals in the circumferential direction and the convex parts are fitted between the coils of the radiating element 2.

[0007]

In the disclosed helical antenna device, the deformation of the radiating element and the change of the antenna radiation characteristic due to this deformation can be prevented even if an external force is applied, but the antenna cover of the antenna cover is formed by plastic molding or the like. Since it is necessary to form the convex portion on the inner side, there is a problem that a complicated manufacturing process is increased and a manufacturing cost is also increased.

[0008]

A helical antenna device according to the present invention comprises a radiating element in which a conductive wire is spirally formed,
In a helical antenna device provided with a coaxial connector for feeding in which a central conductor is connected to one end of the radiating element, a helical tube that covers the radiating element from an outer diameter direction with respect to the axis of the spiral is provided.

[0009] One of the helical antenna devices can be configured such that the shrinkable tube is a heat shrinkable tube.

One of the helical antenna devices may have a configuration in which the radiating element is housed in an antenna cover formed of an elastic body.

[0011]

Next, the present invention will be described with reference to the drawings. 1A and 1B are cross-sectional views showing an embodiment of a helical antenna device according to the present invention. FIG. 1A is a steady state, FIG. 1B is an enlarged view of part A of FIG. 1A, and FIG. 1C is a deformed state. .

The helical antenna device 1 of FIG. 1 is obtained by covering the radiating element 2 of the helical antenna device 1A of FIG. 2 with a heat-shrinkable tube 6 (see FIG. 1 (a)). The heat shrink tube 6 is a tube made of an insulating plastic such as vinyl chloride, and shrinks when heat is applied. The heat-shrinkable tube 6 after heat-shrinking has flexibility.
Since the other constituent elements of the antenna device 1 are the same as those of the antenna device 1A, these constituent elements will be described below as necessary.

The assembly of the helical antenna device 1 is performed by the following steps. First, the lower coil 2c of the radiating element 2 is connected to the central conductor 4b of the coaxial connector 4. Next, the heat-shrinkable tube 6 is put on the radiating element 2 and pushed to the surface of the flange 4a of the coaxial connector 4, so that the radiating element 2 is heat-shrinkable
Cover with. At this time, since the inner diameter of the heat-shrinkable tube 6 has not yet been contracted, there is a margin with respect to the spiral outer diameter of the radiating element 2. When heat is applied to the heat-shrinkable tube 6 in this state, as shown in FIG.
As shown in (b), the heat-shrinkable tube 6 is heat-shrinked and a part thereof comes into contact with the outer diameter of the radiating element 2 and a part thereof also enters the coil gap. After the heat-shrinkable tube 6 is heat-shrinked, the radiating element 2 and the heat-shrinkable tube 6 are covered with the antenna cover 5, and the helical antenna device 1 is completed.

When an external force is applied laterally to the tip of the helical antenna device 1, the antenna cover 5, the radiating element 2 and the heat-shrinkable tube 6 are bent and deformed as shown in FIG. 1 (c). However, the radiating element 2
Between the coils, for example, the coil 2a of the nth turn and (n +
1) Since the heat-shrinkable tube 6 is sandwiched between the coil 2b of the turn, the coils do not come into contact with each other and short-circuit, and the change in the distance between the coils can be kept to a minimum. Therefore, in this antenna device 1, even if an external force is applied to the antenna cover 5 and the radiating element 2 is deformed together with the cover 5,
Undesirable fluctuations in antenna radiation characteristics such as antenna gain / frequency characteristics can be minimized. In addition,
As described above, the prevention of the variation of the antenna radiation characteristic is achieved by the simple manufacturing process of covering the radiating element 2 with the heat shrinkable tube 6.

[0015]

As described above, according to the present invention, since the radiating element of the helical antenna is covered with the contractible tube from the outer diameter direction of the antenna axis, even if the deformation due to the external force occurs, the variation of the antenna radiation characteristic is minimized. There is an effect that the retaining action can be realized with a simple manufacturing process configuration and an inexpensive cost.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a helical antenna device according to the present invention, where (a) is a steady state, (b) is an enlarged view of part A of (a), and (c) is a deformed state. .

FIG. 2 is a cross-sectional view of a conventional helical antenna device,
(A) is a steady state, (b) is a deformed state.

[Explanation of symbols]

 1, 1A Helical antenna device 2 Radiating element 2a, 2b Coil 2c Lower coil 3 Antenna shaft 4 Coaxial connector 4a Flange 4b Center conductor 5 Antenna cover 5a Cover lower part 6 Heat shrink tube

Claims (3)

[Claims] 1. A radiating element in which a conductive wire is spirally formed,
A helical antenna device comprising: a coaxial connector for power supply, in which a central conductor is connected to one end of the radiating element, wherein the helical antenna has a contractible tube that covers the radiating element from an outer diameter direction with respect to the axis of the spiral. apparatus. 2. The helical antenna device according to claim 1, wherein the shrinkable tube is a heat shrinkable tube. 3. The helical antenna device according to claim 1, wherein the radiating element is housed in an antenna cover formed of an elastic body.