JPS63286009A - Two-frequency common use antenna - Google Patents

Abstract

PURPOSE:To design the titled antenna in such a way that it shows nearly the same performance to two frequencies with simple constitution by winding a conductor wire nearly lambda2/4 long to the tip of an antenna element lambda1/2 long around the element in a coil so as to connect the tip of the element to the upper end of the coil. CONSTITUTION:A cylindrical insulator 2 is provided additionally to the outer circumference of the tip of the antenna element 1 lambda1/2 long, the conductor wire lambda2/4 long is wound to the outer circumference to form a coil 3 and the tip of the element 1 and the upper end of the coil 3 are connected, where the relation of lambda1<lambda2 exists. Moreover, a matching circuit 4 is arranged to the other end of the element 1 to realize the matching between the electromagnetic wave impedance at the lower end of the element 1 and the input/output terminal impedance of the device to be connected. Thus, a resonance point is given respectively to two optional frequencies without complicating the constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a dual-wave antenna device n that has resonance points at any two different frequencies and can be used for two frequencies.

(Prior Art) As an antenna used in a device that uses multiple radio waves with significantly different frequencies, such as a wireless communication device using a simultaneous transmission/reception method or a broadband multi-channel wireless communication device, an antenna that resonates with all frequencies is suitable. Although this is considered ideal, there have been no antennas that can meet these requirements.

From this point of view, up until now, the next best option has been to use an antenna that resonates at approximately the center frequency of the desired band, and also to use means to widen the applicable band as much as possible, or to reduce the receiving sensitivity. In order to prioritize the transmission frequency at some cost, it was common to use an antenna that resonated with the transmission frequency.

However, in all of these conventional methods, the antenna efficiency deteriorates significantly at frequencies away from the resonance point, so there is a risk of variations in reception, reliability, or radiated power between channels.

Furthermore, if the transmission frequency deviates significantly from the resonance point of the antenna, there is even a risk that the final stage of the transmitter may be damaged due to the reflected power. It was impossible to process by antenna.

(Objective of the Invention) The present invention was made in view of the above circumstances, and it is possible to provide a resonance point at any two frequencies without complicating the configuration, and it is possible to provide a resonance point at any two frequencies without complicating the configuration. It is an object of the present invention to provide a dual-wave antenna device that can exhibit substantially equivalent performance.

(Summary of the Invention) To achieve this object, the present invention provides a first frequency ft
The wavelength λ, (λ1
〉λi, f+<f2), a conductive wire having a length of about 1/4 is wound around the antenna element in a coil shape,
The present invention is characterized in that the tip of the antenna element and the upper end of the coil are electrically connected.

(Example) Hereinafter, a dual-wave antenna device of the present invention will be described in detail.

Although the lengths of the antenna elements and coils have a wavelength shortening effect, in order to simplify the explanation, this will be ignored in the explanation.

FIG. 1 is an explanatory sectional view showing an embodiment of the present invention.

In the figure, the symbol l is the wavelength λ1 of the first frequency r.
It is an antenna element having a length of 1/2 of
The coil 3 is formed by winding a conducting wire having a length of 1/4 of the second wavelength λ, (f2), which is longer than , and the tip of the antenna element 1 and the upper end of the coil 3 are connected.

Furthermore, a matching circuit 4 is disposed at the other end of the antenna element 1, thereby matching the electromagnetic wave impedance at the lower end of the antenna element 1 with the input/output terminal impedance (50Ω) of a device to which this antenna is to be connected, such as a wireless device. It was configured to achieve consistency.

FIG. 2 shows the Vs w of the antenna having the configuration shown in FIG.
This is a diagram showing an outline of the r< characteristic (voltage standing ratio characteristic), and the antenna has a resonance point of VSWRl, 5 or less at each of two wavelengths λ1 and λ2.

To give a more specific example, for example, the first frequency is f
l=150MH2, second frequency f2=100MII
Z, the length of the antenna element 1 is approximately 100 (cm), and the extension length I21 of the coil 3 is approximately 7 cm.
5 (cm), and as a result, f, = 150MH2 and r
, = xooMoz+:vs w r < was able to obtain an antenna having a resonance point of approximately 1.5 or less.

In addition, as a result of the Gods experiment, the two resonance points frequencies are the length of antenna element 1 and the extension length of coil 3.
This dimension is almost uniquely determined by The difference did not affect the resonant frequency as well.

Furthermore, the interval between the two frequencies f1 and r2 is not limited to the example described above, and can be arbitrarily set.

The frequency ratio fI/f2 between the two can be set to a maximum of 1.5 or more, and the minimum value can be made close to the extent that the two almost match (f, /f, 4.1).

This means that a certain frequency f1 and a lower frequency f2
This means that it is possible to freely select two frequencies and realize an antenna that has resonance points at each frequency, and its design is extremely easy. Also, if the two frequencies are close to each other,
Part of the resonance bands of both devices overlap to form a continuous band, and as a result, it can also be used as a wideband antenna.

FIG. 3 is a diagram showing a specific structure for implementing the present invention, in which the coil winding length is 11. The short antenna element 1a and the tip coil 5 are made separately, and a male screw 6 and a female screw 7 are formed at one end of each, and the two are connected by these screws 6.7. In addition, one side of the male thread 6 extends to the upper end of the insulating cylinder as the central axis of the insulating cylinder, and this tip is connected to the upper end of the coil.

According to this, the coil portion 5 and the antenna element Ia
f by simply exchanging either one of them.

Or, ``Since 2 can be easily changed, it is convenient for production to accommodate various combinations of frequencies.

In the embodiments described below, an insulator or a dielectric material is filled between the coil and the antenna element, but there is no need to limit the invention to this, and an air-core coil may be used. There are various methods, such as drawing a spiral coil around the cylindrical insulator using conductive paint, or shaping RI4 thin film deposited on the periphery and surface of the cylindrical insulator into a helical coil using an etching technique. You can think of transformations.

Furthermore, regarding the material of the antenna element, materials conventionally used for antenna elements, such as a simple metal rod, a metal vibrator, and a spirally wound elastic metal wire to provide flexibility5, can be applied as appropriate. There is absolutely no problem in doing so.

In this way, by winding a wire with a length of 1/4 of the desired wavelength λ8 in a coil shape (coaxially) around the outer circumference of the tip of the antenna element with a length of approximately λ1/2, each wavelength λ1 can be adjusted.
The reason why a resonance point occurs for each of %λ2 is inferred as follows. That is, first, a high-frequency current standing wave is generated in the antenna element having a length of 1/2 of the first wavelength λ1 as shown by the broken line in Fig. 4 (at), while almost no current flows at the tip of the antenna element. Therefore, the presence of the external coil can be ignored.Next, for the second wavelength λ2, as shown by the broken line in fb) in the same figure, the length of the amplifier element is insufficient for λ2/2; A high-frequency current of a certain value flows through the tip, and this flows into the coil. However, since the current flowing in the coil is in the opposite direction to the current flowing in the antenna element l, inductance is generated between the two, and as a result, it acts as a shortened coil, and the
2 can resonate.

The impedance matching circuit added to the other end of the antenna element 1 is for converting the high impedance at the end of the antenna element to the low impedance of a human output such as a wireless communication device, for example 50Ω, and is a four-terminal circuit network. In particular, a circuit equivalent to a matching circuit using the impedance conversion effect of a λ/4 distributed constant circuit is used.

Hereinafter, a matching circuit suitable for the present invention related to - will be briefly explained.

FIG. 5 is a schematic diagram illustrating the impedance conversion effect of the λ/4 distributed constant circuit, and reference numeral 10 indicates a λ/4 long parallel line or a coaxial line of the same length with a characteristic impedance of 70.

If resistance values R and R2 are connected to both ends of this line, lZ,! =ETπ−=πτ−−−・The equation (1) holds, and if 1 is the impedance of the λ/2 long antenna element end, for example, IKΩ, and R2 is the impedance of the input/output end of the radio, for example, 50Ω. , lZ, l= 1ooOX
50 Cape 224 (Ω)...(2) The following formula holds true.

That is, characteristic impedance Z is required to match the two. It is sufficient to use a coaxial line having a length of λ/4 with a resistance of 224Ω.

Note that parallel lines or coaxial lines with a length of λ/4 are large and inconvenient, so it is necessary to construct an equivalent circuit.Since this technology is well known, detailed explanation will be omitted. As a concrete example, if the structure is such that a coil is placed at the center of a cylindrical conductor as shown in Figure 6, it is possible to realize an extremely compact impedance conversion circuit using a λ/4 distributed constant. .

(Effects of the Invention) As explained above, the dual-wave antenna device of the present invention has the following features:
A second frequency f,
A conductive wire having a length of about 1/4 of the wavelength λ, (λ1 × λs, fl > fs) is wound into a coil around the antenna element, and the tip of the antenna element and the upper end of the coil are connected. Since it is configured to be electrically connected, any two can be connected without complicating the configuration.
It is possible to have a resonance point at each of the two frequencies, and it is possible to emit substantially the same performance at two different frequencies.

[Brief explanation of the drawing]

FIG. 1 is an explanatory cross-sectional configuration diagram showing one embodiment of the present invention, and FIG.
The figure is a diagram showing an overview of the VSWR characteristics of the antenna, Figure 3 is a diagram illustrating the specific configuration of the antenna of the present invention, and Figure 4 (a)
(bl is an explanatory diagram of the distribution state of high-frequency current standing waves generated corresponding to each wavelength, Fig. 5 is a schematic diagram illustrating the impedance conversion effect of the λ/4 distributed constant circuit, and Fig. 6 is a diagram illustrating the impedance conversion effect of the λ/4 distributed constant circuit. An explanatory diagram showing a specific example of a matching circuit to be used.

Claims (4)

[Claims] (1) The wavelength λ_1 for the first frequency f_1 is approximately 1
A second frequency f_2 lower than the first frequency f_1 is arranged on the outer periphery of the tip of the antenna element having an electrical length of /2.
By winding a conductive wire with a length of approximately 1/4 of the wavelength λ_2 in a coil shape, and electrically connecting the upper end of the coil to the tip of the antenna element, the first and second frequencies can be adjusted to each of the first and second frequencies. A dual-wave antenna device characterized by having a resonance point. (2) The dual-wave antenna device according to claim 1, characterized in that an insulating material cylinder is positioned between the tip of the antenna element and a coil wound around the outer periphery of the antenna element. (3) An impedance matching circuit is added to the lower end of the antenna element to match the high impedance of the lower end of the antenna element with the input impedance of a device to be connected. 2. The dual-wave antenna device according to item 1 or 2. (4) A patent characterized in that the impedance matching circuit has a configuration in which a coil passes through the conductor cylinder, thereby realizing a circuit equivalent to an impedance conversion circuit using a λ/4 (λ is frequency wavelength) long distributed constant circuit. A dual-wave antenna device according to claim 3.