JPS59172803A - Antenna for small-sized radio equipment - Google Patents

Abstract

PURPOSE:To obtain an antenna having a large antenna gain and a wide receiving frequency band width by providing a shape to an antenna element forming plural number of closed loops passing through a reactance circuit at the same end face of the said element. CONSTITUTION:The antenna includes an antenna element 20 having the element for the 1st loop comprising A-B-E-F and the element for the 2nd loop comprising A-C-D-F connected in parallel with the element for the 1st loop, a variable capacitor 21 functioning as the reactance circuit for the tuning and for setting an output impedance connected in parallel with both the said elements, and a capacitor 22 connected to a connecting point A of both the said elements and the capacitor 21. The antenna element 20 has a shape where two closed loops different from each other in size are formed through the capacitor 21 at the same end face. Thus, a tuning circuit is constituted easily by a desired frequency and since the aperture area of the antenna is increased in addition, the antenna having a large antenna gain and a wide receiving frequency band width is attained in this way.

Description

[Detailed description of the invention] The present invention relates to an antenna for small radio equipment, and more particularly to an antenna for a small radio device.

The present invention relates to an antenna for a portable radio receiver.

2. Description of the Related Art Conventionally, portable radio receivers, particularly individual selective call receivers such as pagers, have been miniaturized so that they are usually carried around by users.

The antennas used in these receivers are often loop antennas that can be built into the receiver, and in order to make the receiver more compact, air-core loop antennas without a magnetic core are used. .

Conventionally, this type of loop antenna, as shown in FIG.
It is connected to both ends of 1 and has a variable configuration. In this antenna, by selecting the values of the variable capacitor 11 and the capacitor 12, a desired output impedance can be obtained at a desired frequency. by the way.

When the frequency to be received becomes higher, the value of the inductance of the antenna element 10 or the capacitance of the variable capacitor 11 and the capacitor 12 must be reduced. However, with this antenna,
There is a limit to reducing the capacitance value, and eventually the inductance value must be reduced. Therefore, in the antenna of FIG. 1, even though there is space in the receiver to realize a large loop antenna.

The drawback was that the maximum dimensions of the antenna were determined by the receiving frequency. Furthermore, in these seven types of loop antennas, the antenna gain is approximately -16 dB as a dipole ratio in the 450 MHz band, and in this region, the antenna gain increases as the aperture area of the antenna increases.

However, in the loop antenna shown in Fig. 1, the dimensions of the antenna are determined by the receiving frequency as described above, so the opening area of the antenna is 1/1/1 of the opening surface of the housing.
It is only used about 6 times.

The disadvantage was that the antenna gain was reduced.

Further, the loop antenna shown in FIG. 1 has a drawback that the Q value is large and the reception frequency bandwidth is narrow.

An object of the present invention is to provide an antenna for a small radio device that can effectively utilize the space of a receiver for a loop antenna, increase the antenna gain, and widen the reception frequency bandwidth. There is a particular thing.

According to the present invention, connected to both ends of the reactance circuit,
A small radio antenna having a conductive element forming a closed loop with the reactance circuit, wherein the conductive element has a shape in which a plurality of closed loops passing through the reactance circuit are formed on the same end surface. A compact radio antenna that can be obtained

Next, the practical side of the present invention will be explained with reference to the drawings.

Referring to FIG. 2, a first embodiment of the present invention.

A first loop element consisting of A-B-E-F and A-C-D-F connected in parallel for the first loop element.
a conductive element (i.e., an antenna element) 20 having a second loop element consisting of a second loop element, and a conductive element (i.e., an antenna element) 20 for tuning and setting output impedance connected in parallel to the first loop element and the second loop element. It includes a variable capacitor 21 which is a glue actance circuit, and a capacitor 22 connected to a connection point A of the first loop element, the second loop element, and the capacitor 21. The antenna element 20 has a shape in which two closed loops of different sizes passing through the variable capacitor 21 are formed on the same end face.

The first loop element has a desired frequency (e.g. 4
501viH7), the inductance L+ is large enough to easily satisfy the resonance condition when the capacitive circuit is loaded.
(for example, 10 nH). The second loop element has an inductance L2 (for example, 5
0 nH). The second loop element has a size that allows the use of two, for example, openings of the receiver housing at the same time. The inductance of the antenna element 20 in which the first loop element and the second loop element are connected in parallel. is calculated as Ll −L2 Lo−Ll +L2, and in the case of r L 1 ′ < L 2, Lok
It becomes Ll. In the antenna element 20, although the aperture area of the antenna is the same as that of the second loop element and is larger, the inductance value is the same as that of the first loop element, and the resonance condition is easily satisfied. The resulting antenna can be realized. In other words, in this embodiment, it is possible to easily configure a tuning circuit at a desired frequency, and since the aperture area of the antenna is increased, it is possible to realize an antenna with a large antenna gain and a wide reception frequency bandwidth. I can do it.

When compared numerically, as shown in Figure 3, the frequency band when the voltage standing wave ratio VSWR is -2 (reflection coefficient - 33) is as shown in Figure 3 (A) for an antenna with a conventional configuration. As shown in FIG. 3(B), as shown in FIG.
Hz) and spreads approximately 6°5 times. Also.

Regarding antenna gain, the conventional configuration antenna has -1
9.6 dB, and -12 dB for the antenna with the configuration of the present invention.9. ．． 4dB gain is increased. That is, it is possible to realize an antenna with a large antenna gain and a wide reception frequency bandwidth.

Referring to FIG. 4, a second embodiment of the present invention is shown.

An antenna element (i.e., a conductive element) 40, a variable capacitor 41 connected in parallel to the antenna element 40, and a connection point G between the antenna element 40 and the variable capacitor 41.
and a capacitor 42 connected to the capacitor 42 . The antenna element 40 has an upper plate 40a, a side plate 40b, a lower plate 40c, and a connecting plate 40d connecting the upper plate 4-Oa and the lower plate 40c at the front. The antenna element 4
0 is.

A first loop passing through the capacitor 41 is formed by G-H- and -L, and a second loop passing through the entire capacitor 41 is formed by G-I-J-L. Also in this example,
Similar to the embodiment shown in FIG. 2, the antenna element 40 has a shape in which two closed loops of different sizes passing through the variable capacitor 41 are formed on the same end surface (front surface). In this embodiment as well, as in the first embodiment, a tuning circuit can be easily configured, and an antenna with a large antenna gain and a large receiving frequency bandwidth can be realized.

As described above, the present invention has the effect of making it possible to effectively utilize the space of the receiver that is left over from the loop antenna, and realizing a compact radio antenna with a large antenna gain and a wide reception frequency band.

Furthermore, in conventional antennas, the value of the UHF band was changed, but according to the present invention, an antenna with a wide frequency band can be realized, so the capacitors 22 and 42 can have a common value, which makes mass production easier. It also has the effect of realizing a good antenna for small radio equipment.

It goes without saying that the present invention also includes modifications to the above-described embodiments. for example.

The number of closed loops passing through the reactance circuit 21 or 41 is 2.
It is not limited.

[Brief explanation of the drawing]

Figure 1 is a front view of a conventional small radio antenna.
Fig. 2 is a front view showing a small radio antenna according to the first embodiment of the present invention, and Figs. 3 (A) and (B) show the frequency-reflection coefficient characteristics of the conventional antenna and the antenna of the present invention, respectively. FIG. 4 is a perspective view showing an antenna for a small radio device according to a second embodiment of the present invention. 10.20 and 40... antenna element (conductive element). 11, , 21 and 41 ・Variable capacitor, 12゜2
2 and 42... capacitor. Sheep 1 Figure 2 Figure 1 Figure 4

Claims (1)

[Claims] 1. In a small radio antenna having a conductive element connected to both ends of a reactance circuit and forming a closed loop with the reactance circuit, the conductive element has a shape in which a plurality of closed loops passing through the reactance circuit are formed on the same end surface. An antenna for a small radio device characterized by having the following characteristics: