JPH0514040A - Antenna system - Google Patents

Abstract

PURPOSE:To realize the two-resonance whip antenna in which the antenna is resonated at two optional points with high degree of freedom of the length of the whip antenna, excellent radiation characteristic and at less loss with respect to the 2-resonance antenna system for a radio equipment. CONSTITUTION:A coil A2 formed by a rod or strip conductor wound in spiral and a coil B3 with a different number of turns from that of the coil A2 are connected to each other so that the winding directions of the coils A2, B3 differ from each other, one end of a rod conductor 1 is connected to their connecting point 4 and feeding is implemented from the other end of the rod conductor 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna device for a wireless device, and more particularly to a whip antenna device which requires two resonance characteristics.

[0002]

2. Description of the Related Art FIG. 7 shows an example of a conventional two-resonance whip antenna. In the same figure, (a) shows that two resonance characteristics are obtained by an internal matching circuit, and (b) shows that two resonance characteristics are obtained by providing a coil on the whip antenna element. First, FIG. 3A will be described. Number 20 in the figure
Is a whip antenna element, 21 is a radio main body, 22 is a matching circuit, 23 is a two-resonance circuit, and 24 is an antenna output terminal. The matching circuit 22 and the two-resonance circuit 23 enable the whip antenna to obtain the two-resonance characteristics of fh and fl even though it is a single element. With this configuration, there is an advantage that the length of the whip antenna can be determined quite freely, and resonance can be achieved at any two points.

Next, FIG. 1B will be described. In the figure, numeral 25 is a whip antenna element, 26 is a coil,
Reference numeral 27 is a radio body, 28 is a matching circuit, and 29 is an antenna output terminal. In this whip antenna, the coil 26 acts as an inductive element, and the frequency fl at which the coil 26 resonates substantially over the entire length of the whip antenna and the coil 26
Acts as a trap element so as not to pass a current earlier than that, and two resonance characteristics are obtained at a frequency fh which resonates almost up to the coil of the whip antenna. In the antenna of this configuration, the matching circuit does not become complicated and the loss is not so large. Also, since the feeding point impedance is the same at both resonance frequencies, there is little difference in radiation patterns.

[0004]

Among the conventional two-resonance whip antennas described above, the former one shown in FIG. 7 (a) has a complicated circuit inserted from the antenna to the receiver. However, there is a drawback that it is difficult to obtain good radiation characteristics with sufficiently high gain. further,
In this antenna, the impedance at the feeding point is fh and hl
Therefore, there is a drawback in that the current flowing through the housing differs between the two and the radiation pattern changes between fh and fl.

On the other hand, in the latter antenna having the configuration shown in FIG. 7 (b), the resonance frequency is determined almost by the length of the whip antenna. Therefore, in order to obtain the two resonance characteristics, the structural parameters of the whip antenna are restricted. In addition, there is a drawback that the two resonance characteristics can be obtained only at two points within a certain specific range.

That is, in the conventional two-resonance whip antenna, when two resonances are realized in the internal circuit, the loss becomes large and the radiation pattern shape at each resonance point is different. In the case of realizing it by providing a coil, the shape of the antenna is restricted and 2
It had the drawback of not being able to arbitrarily obtain one resonance point.

The present invention has been made in order to solve the above problems, and can resonate at any two points, has a degree of freedom in the length of a whip antenna, and radiates less loss. The purpose is to realize a two-resonance whip antenna with good characteristics.

[0008]

According to the present invention, the above problems can be solved by an antenna having the structure described in the claims. That is, the present invention is
Coil A formed by spirally forming a rod-shaped or strip-shaped conductor
And a coil B having a different number of turns from the coil A.
And the coil B are connected so that the winding directions thereof are opposite to each other, one end of a conductive rod-shaped conductor is connected to the connection point, and power is supplied from the other end of the rod-shaped conductor.

[0009]

Since the antenna device of the present invention has the above-described structure, the rod-shaped conductor (whipped antenna) length and coil A, and the rod-shaped conductor (whipped antenna) length and coil B resonate independently. It operates as a two-resonance antenna. The antenna of this configuration has a high degree of freedom in antenna length and resonance frequency due to its structure, and since it does not require a special matching circuit, there is little loss, and
Since the input impedances are the same at both resonance points, there is little change in the radiation characteristic at each frequency, so that a two-resonance antenna device having good characteristics can be realized.

[0010]

FIG. 1 is a diagram showing an embodiment of the present invention. In the figure, 1 is a rod-shaped antenna element, 2 is a coil A, 3
Is a coil B, 4 is a connection point of the coil A, the coil B and the rod-shaped antenna element, 5 is a feeding point, and 6 is a radio main body. The coil A2 and the coil B3 are the linear antenna element 1
Are wound in opposite directions with the center axis as. Since this antenna has such a structure, the resonance frequency Fl is determined by the current flowing through the rod-shaped antenna element 1 and the coil A2, and the resonance frequency F2 is similarly determined by the current flowing through the rod-shaped antenna element 1 and the coil B3. In particular, the coil A and the coil B are reversely wound to reduce the mutual coupling, so that the coil A and the coil B operate independently even though they are very close to each other.

FIG. 2 is a diagram showing a model for confirming the characteristics of this embodiment. In the figure, 7 is a rod-shaped antenna element, 8 is a coil A, 9 is a coil B, 10 is a feeding point,
Reference numeral 11 represents a radio device main body, 12 represents a matching circuit, the whip antenna length 13 is 105 mm, the length of the coil A is 10 mm, the diameter is 4 mm, the number of turns is 7, and the length of the coil B is 8 mm, the diameter is 4 mm, and the winding is Several times, the radio housing has a height 14 of 130 mm, a width 15 of 55 mm, and a thickness 16 of 24.
mm.

FIG. 3 is a diagram showing the input impedance characteristic of the above model, where (a) is the return loss characteristic,
(B) shows Smith chart characteristics. As is clear from this figure, this antenna clearly shows two resonance characteristics. And fh is 1058MHz and fl is 890
MHz.

FIG. 4 is a diagram showing horizontal / vertical radiation patterns at each resonance point of the above model. In the figure, (a) shows the case of fl: 890 MHz, (b) shows the case of fh: 1058 MHz, the numeral mark 18 represents Eθ, and the numeral mark 19 represents the Eφ component. Thus, it can be seen that the present antenna has a sufficiently high radiation level at both resonance points. The radiation pattern shapes of the two are different in the upper part, but are almost the same in the lower part. This is because the radiation from the antenna is radiation from the current induced in the housing, not the influence of the current flowing from the feeding point.

FIG. 5 shows the relationship between the number of turns of the coils A and B and each resonance frequency in the above embodiment. In the figure,
In (a), the lower coil B is fixed to 9 turns and the number of turns of the upper coil A is changed, and in (b), the upper coil A is fixed to 7 turns and the number of turns of the lower coil B is changed. The resonance frequency when changed is shown. It can be seen that in (a), fh hardly changes, but fl decreases as the number of turns of the upper coil A increases. On the other hand, in (b), it can be seen that fl hardly changes, but fh decreases as the number of turns of the lower coil B increases. That is, the upper coil A has a resonance frequency fl and the lower coil B has a resonance frequency f.
It can be seen that h is set and each can be changed independently.

FIG. 6 is a diagram showing another embodiment of the present invention. In the figure, 1 is a linear antenna element, 2a is a coil A, 3a is a coil B, 4a is a connection point between the coil A and the coil B and a rod-shaped antenna element, 5 is a feeding point, and 6 is a radio apparatus main body.

In the present embodiment, the above-described embodiment is configured such that the axial direction of the rod-shaped antenna element and the central axes of the coils A and B coincide with each other. The difference is that the central axis is configured to be orthogonal to the rod-shaped antenna element.

Even with such a configuration, the rod-shaped antenna element 1 and the coil A2a, and the rod-shaped antenna element 1 and the coil B3a resonate independently of each other, so that a two-resonance antenna having good characteristics as in the above embodiment is obtained. Obtainable.

[0018]

As described above, in the antenna device of the present invention, the coils A and B having different numbers of turns are connected so that the winding directions are opposite to each other, and the whip antenna is connected to the connection point. Because of the structure, the whip antenna length and coil A, and the whip antenna length and coil B
Since the antennas resonate independently of each other, the degree of freedom of the antenna length and resonance frequency is high, and since no special matching circuit is required, there is little loss, and since the input impedance is the same at both resonance points, the radiation characteristics at each frequency There is an advantage that it is possible to obtain a two-resonance antenna device having good characteristics with a small change in.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a model for confirming the characteristics of the example.

FIG. 3 is a diagram showing an input impedance characteristic.

FIG. 4 is a diagram showing horizontal / vertical radiation patterns at resonance points.

FIG. 5 is a diagram showing the relationship between the number of turns of coils A and B and each resonance frequency.

FIG. 6 is a diagram showing another embodiment of the present invention.

FIG. 7 is a diagram showing an example of a conventional two-resonance whip antenna.

[Explanation of symbols]

 1,7 Linear antenna element 2,2a, 8 Coil A 3,3a, 9 Coil B 4 Connection point 5,10 Feed point 6,11 Radio main unit 12 Matching circuit 13 Whip antenna length 14 Height of radio casing 15 Width of wireless device housing 16 Thickness of wireless device housing 17 Eθ component 18 Eφ component

Claims (1)

Claim: What is claimed is: 1. A coil A, which is formed by spirally forming a rod-shaped or strip-shaped conductor, and a coil B having a different number of turns from that of the coil A. An antenna device having a structure in which one end of a conductive rod-shaped conductor is connected to the connection point, and power is supplied from the other end of the rod-shaped conductor.