JPH03252203A - Antenna shared among three waves for automobile with sleeve - Google Patents

Abstract

PURPOSE:To obtain an antenna shared among three waves for automobile which has a small reactive capacity by providing first, second, and third conductive tubular sleeves and specifying the length of each of these sleeves and attaching them in specific positions respectively. CONSTITUTION:A first sleeve 10 is used for mobile station frequency 825MHz and is short-circuited to a linear antenna 2, and its length L1 is set to 1/4 of a guide wavelength lambdag1, and its distance D1 to the ground is set to 1/4 of wavelength 850MHz. A second sleeve 20 is used for base station frequency 890MHz, and its length L2 is set to 1/4 of a guide wavelength lambdag2, and its distance D2 to the sleeve 10 is about lambda1/8 to lambda1/4. The third sleeve is matched to an approximately middle frequency 870MHz of the frequency band of a land mobile radio- telephone wave and has the upper end opened to the antenna 2 and has the lower end short-circuited to the sleeve 20, and its length L3 is set to 1/4 of a guide wavelength lambdag3, and its distance D3 to the sleeve 20 is set to 3/4 of lambda2. A distance D4 from the upper end part of the antenna 2 to the sleeve 30 is set to 3/4 of wavelength 890MHz. Thus, impedance matching is facilitated.

Description

[Detailed description of the invention] [Industrial application field] TECHNICAL FIELD The present invention relates to a three-wave shared antenna for a train.

[Prior Art] Currently, mobile communications are becoming popular, and car telephones are also gradually becoming popular. Automobiles are equipped with AM and FM radio antennas, but if a car phone is to be used, an antenna for the mobile car phone will be added. Recently, there has been a demand for a three-wave antenna that combines antennas used for AM, FM, and car phone radio waves into one.

It has been partially put into practical use by coil loading.

By the way, in order for the three-wave shared antenna to be efficient for AM and FM waves, it is preferable to make the antenna length longer.If the radiation directivity of car phone waves is sharp, the car body may Since sensitivity may drop when tilted, it is required to have relatively broad radiation directivity.

However, in the conventional three-wave antenna for train cars,
In order to increase the length of the antenna, a collinear system is often used.1 It is difficult to have a relatively broad radiation directivity, and the structure of the antenna is complicated.

To overcome this drawback, it is known to add a conductive sleeve to a linear antenna. In other words, the lower end of the sleeve is shorted to the linear antenna, the upper end of the sleeve is open to the linear antenna, the length of the sleeve is set to 1/4 of the pipe wavelength, and the length of the sleeve is set to 1/4 of the pipe wavelength. The length of the upper part is set to 374 wavelengths, which is the wavelength of automobile telephone waves, thereby suppressing the antenna current (current of automobile telephone waves) in the upper part than the sleeve.

Note that the length from the upper end of the sleeve to the ground is set to 172 wavelengths, which is the wavelength of a car telephone wave. By doing so, it has relatively broad radiation directivity and the antenna structure is simple.

[Problems to be Solved by the Invention] The linear antenna with the sleeve added has a very large impedance at the feeding point in telephone waves, and the impedance between this impedance and 50Ω, which is set as the input impedance of the antenna, is very large. It is necessary to perform impedance matching, and there is a problem that this impedance matching is complicated.

Further, in order to perform the impedance matching, for example, a double-structured vibrator is installed coaxially with the above-mentioned linear antenna, and the antenna output is extracted from a point calculated by a Smith chart. In this case, a problem arises in that a reactive capacity occurs in the double-structured pipe portion, and the antenna gain for AM and FM waves decreases due to the reactive capacity.

SUMMARY OF THE INVENTION An object of the present invention is to provide a three-component antenna for an automobile that allows easy impedance matching and has a very small reactive capacity.

[Means for Solving the Problems] The present invention provides a linear antenna with a conductive tubular first sleeve and a second sleeve, the lower end of each sleeve is short-circuited with the linear antenna, and the upper end of each sleeve is short-circuited with the linear antenna. The length of the first sleeve and the second sleeve are set to approximately 1/4 of the service wavelength determined at the low and high frequencies of the car phone frequency band, respectively, and the antenna is opened. from the first current node of the current distribution above the first sleeve at the low frequency of approximately λ/8 towards ground.
The upper end of the first sleeve is set at a position of ~λ/4, and from the first current node of the current distribution above the second sleeve in the high frequency range of the frequency band for mobile phones, toward the ground. The upper end of the second sleeve is finely set at a position of approximately λ/8 to λ/4, and the length from the upper end of the sleeve closest to the ground of the first sleeve and the second sleeve to the ground is set for a car phone. The frequency is set to approximately 174 wavelengths.

In addition, the present invention provides a first sleeve, WS? A third sleeve similar to the first sleeve and the second sleeve is provided at a position above the sleeve, and from the first current node of the current distribution above the third sleeve at a predetermined frequency of the frequency band for mobile phones, Approximately λ/8 to λ/4 toward the ground
The upper end of the third sleeve is set at the position.

[Function] In the present invention, the lower ends of the first sleeve and the second sleeve are short-circuited to the linear antenna, and the upper ends of each sleeve are open to the linear antenna, so that the lengths of the first sleeve and the second sleeve are
It is set to approximately 1/4 of the in-service wavelength determined at the low and high frequencies of the car phone frequency band, respectively, and the beginning of the current distribution above the first sleeve at the low frequency of the car phone frequency band is The upper end of the first sleeve is set at a position approximately λ/8 to λ/4 toward the ground from the current node of
Since the upper end of the second sleeve was set at a position approximately λ/8 to λ/4 toward the ground from the first current node of the current distribution above the sleeve, the upper end of the first sleeve The current in the low range of the frequency band for telephones is suppressed, and the current in the high range of the frequency band for car telephones is suppressed at the upper end of the second sleeve, and the upper end of the first sleeve and the second sleeve is closer to the ground. The length from the part to the ground,
Approximately 1/4 of the middle frequency of the car phone frequency band
Since it is set to the wavelength, the impedance matching means for car telephone waves becomes easy, and since the reactive capacity can be made small, there is little decrease in antenna gain for both car telephone waves, AM, and FM waves.

Furthermore, when the third sleeve is added, the length of the linear antenna can be reduced to about 700 m, so that the reception sensitivity at AM/FM frequencies is further improved.

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

A three-wave automotive antenna with a sleeve 1 includes a linear antenna 2, a first sleeve 10, a second sleeve 2G, and a third sleeve 30, and the sleeves 10, 20, and 30 are tubular and have conductivity. be.

FIG. 2 is an explanatory diagram of the first sleeve IO in the above embodiment.

The first sleeve 10 has a mobile station frequency (82
5MHz), the upper end 11 of the first sleeve 10 is open to the linear antenna 2, and the first sleeve 1
The lower end 12 of the first sleeve IO is short-circuited to the linear antenna 2, and the length Ll of the first sleeve IO is set to 1/4 of the wavelength 1 within the tube. Note that the tube wavelength λ91 is λ, /(2,
3) l/2, input 1 is the wavelength of the mobile station frequency (825 MHz) of the mobile phone, and the distance DI from the upper end ll of the first sleeve 10 to its ground is 850 MHz.
It is one quarter of the wavelength of z.

@l Polyethylene 13 having a dielectric constant of 2.3 is provided between the sleeve 10 and the linear antenna 2. Further, the wire diameter of the linear antenna 2 is 2.01 mm, and the diameter of the first sleeve 1 is 2.01 mm.
The inner diameter of 0 is 4.8 intestinal layers and its outer diameter is 8.0 mm. Note that a dielectric material other than polyethylene may be used, and in this case, when determining the tube wavelength input 91, the input,
It is necessary to change the denominator in parentheses in /(2,3)1/2.

FIG. 3 is an explanatory diagram of the second sleeve 20 in the above embodiment.

The second sleeve 20 has a base station frequency (89
0MH2), the upper end 21 of the second sleeve 20 is open to the linear antenna 2, and the second sleeve 2
0 is short-circuited with the linear antenna 2, and the length L2 of the second sleeve 20 is set to 1/4 of the pipe wavelength input q2. Note that the tube wavelength λ,2 is input2/(2
, 3) I 72, and input 2 is the wavelength of the mobile phone base station frequency (890 MHz).

Further, the distance D2 from the upper end 21 of the second sleeve 20 to the upper end 11 of the first sleeve 1O is determined as follows. In other words, when looking at the ground side from the upper end of the linear antenna 2, the first sleeve 1 is placed at a position approximately 1/8 to 1/4 from the node of the first current at the design frequency of the first sleeve.
A distance D2 is determined so that the upper end 11 of 0 is located,
This distance D2 is determined by experiment.

FIG. 4 is an explanatory diagram of the third sleeve 30 in the above embodiment.

The third sleeve 30 has a frequency (870
MHz), the upper end 31 of the third sleeve 30 is open to the linear antenna 2, the lower end 32 of the WIJ3 sleeve 30 is short-circuited to the linear antenna 2, and the length L3 of the third sleeve 3G is is set to 174, which is the tube wavelength λg3. Note that the in-tube wavelength input 93 is λ3/(2
-3) 1/2, and input 3 is the base station frequency (87
0 Hz), and the upper end 3 of the third sleeve 30
The distance D3 from the upper end 21 of the second sleeve 20 is λ2 (3/4).

Furthermore, a third sleeve 30 is inserted from the upper end of the linear antenna 2.
The distance D4 to the upper end 31 is (3/4) of the wavelength at 890 MHz.

Next, the operation of the above embodiment will be explained.

First, focusing on the first sleeve lO, at the design frequency of the first sleeve, the impedance Zin seen from the upper end 11 of the first sleeve 10 is theoretically infinite, and therefore from the lower end 12 of the first sleeve lO The current flowing through the first sleeve 10 is prevented from flowing into the first sleeve 10. That is, the first sleeve 10
This is equivalent to the fact that the upper conductor and lower conductor of the three-component antenna 1 are separated at the upper end 11 of the antenna.

Regarding the second sleeve 20 and the third sleeve 30,
As in the case of the sleeve 10, the upper conductor and the lower conductor of the three-component antenna l are separated at the sleeve upper end 21.31 at the design frequency of each sleeve 10.20.30. It is.

FIG. 5 shows that in the above embodiment, the frequency of the mobile station is 82
This shows the current distribution when a signal of 5 MHz is input, and FIG. 6 is a diagram showing the radiation pattern at that time.

FIG. 7 shows that in the above embodiment, the base station frequency is 89
This shows the current distribution when a signal of 0 MHz is input, and FIG. 8 is a diagram showing the radiation pattern at that time.

According to the above embodiment, the sleeves io,
20.30 is added to the linear antenna 2, the current amplitude in the upper portion is suppressed by each sleeve 1O120, 30. Moreover, since the length from the upper end of the first sleeve lO to the ground is set to approximately 1/4 wavelength of the approximately middle frequency of the frequency band for car telephones, the three-component common antenna lO
The output impedance is around 50Ω, which makes impedance matching easy. Also, by performing impedance matching, the accompanying reactive capacitance is minimized, and the decrease in the three-component common antenna gain is small, and sidelobes are eliminated. relatively broad radiation directivity can be obtained.

Furthermore, at AM and FM frequencies, the sleeve 10.20
．． 30 has little effect, so set the antenna length to A.
After making the length efficient for M and FM waves, a sleeve suitable for car phone waves can be added.

In the above embodiment, from the first current point of the current distribution at a frequency approximately in the middle of the 5 car phone frequency bands, it is placed at a position of 1/4 toward the ground.

Each upper end 11 of the first sleeve IO1 and second sleeve 20.
21, but each upper end portion 11.2 of the first sleeve lO1 and second sleeve 20 is set at a position approximately λ/8 to λ/4 from the first current node of the current distribution at the above frequency.
It may be set to 1.

FIG. 9 is a diagram showing another embodiment of the present invention, and is a diagram showing an example in which two sleeves are provided.

A three-wave automotive antenna with a sleeve shown in FIG. 9 1a
is a linear antenna 2. , the first sleeve 10a and the second sleeve 10a
It has a sleeve 20a.

The linear antenna 2a, the first sleeve 10a, and the second sleeve 20a are the linear antenna 2. First sleeve 10. It is similar to the second sleeve 20.

However, while the length of the linear antenna 2 is about 700 m1, the length of the linear antenna 2a is about 400 m1.

Further, the distance Dla from the upper end 11a of the first sleeve 10a to the ground is equal to 4 of the wavelength at 850 MHz.
It is 1/1. Further, the upper end portion 21 of the second sleeve 20
Distance D from a to the upper end 11a of the first sleeve 10a
2a is also determined in the same manner as the distance D2. Linear antenna 2
a to the upper end 21.a of the second sleeve 20a. The distance D3a is λ2 (3/4).

Figure 1O shows the current distribution when a signal is input when the frequency of the mobile station is 825 MHz in the embodiment of Figure 9, and Figure 11 shows the radiation pattern at that time. It is.

FIG. 12 shows the current distribution when a signal is input when the base station frequency is 890 MHz in the embodiment shown in FIG. 9, and FIG. 13 shows the radiation pattern at that time. It is.

The embodiment shown in FIG. 9 also has the advantage that impedance matching is easy and the reactive capacitance is very small.

In the above embodiment, the base station frequency is 890 MHz and the mobile station frequency is 825 MHz. However, the frequencies differ depending on the country, and in order to be applicable in each country, the following steps should be taken. ,In other words,
The length of the first sleeve is set to approximately 1/4 of the in-service wavelength determined at the low frequency band of the frequency band for mobile phones, and the length of the second sleeve is set to approximately 1/4 of the channel wavelength determined at the low frequency band of the mobile phone frequency band. It is set to approximately 1/4 of the pipe wavelength determined in , and the current is approximately λ/8 to λ/ from the first node on the first sleeve toward the ground in the low frequency range of the car phone frequency band.
The upper end of the first sleeve is set at position 4, and from the first current node on the second sleeve in the high frequency range of the frequency band for car telephones, approximately λ/8 ~ towards the ground.
Set the upper end of the second sleeve at the λ/4 position, and
Of the sleeve and the second sleeve, the length from the upper end of the sleeve closest to the ground to the ground may be set to approximately 1/4 wavelength of a frequency approximately in the middle of the frequency band for mobile telephones.

In this case, as in the above embodiment, the first sleeve may be located below the second sleeve, or conversely, the first sleeve may be located above the second sleeve.

Furthermore, when the third sleeve is provided above the first sleeve and the second sleeve, the length of the third sleeve is approximately 1/4 of the channel wavelength determined at a frequency approximately in the middle of the frequency band for car telephones. and from the first current node above the third sleeve at a predetermined frequency of the car phone frequency band,
The upper end of the third sleeve may be set at a position approximately λ/8 to λ/4 toward the ground.

Note that the above-mentioned "initial current node on the first sleeve" refers to the upper end when viewed from the upper end 11, lla of the first sleeve 10.10a to the upper end of the linear antenna 2.2a. Section 11 is the current node closest to lla. Also, the “first current node on the second sleeve” is also “the third node”.
``first current node above sleeve'' is also similar to ``first current node above first sleeve''.

[Effects of the Invention] According to the present invention, impedance matching is easy and effective capacity is extremely small.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention. FIG. 2 is an explanatory diagram of the first sleeve 10 in the above embodiment. FIG. 3 is an explanatory diagram of the second sleeve 20 in the above embodiment. FIG. 4 is an explanatory diagram of the third sleeve 30 in the above embodiment. FIG. 5 shows that in the above embodiment, the frequency of the mobile station is 82
This shows the current distribution when a signal of 5 MHz is input, and FIG. 6 is a diagram showing the radiation pattern at that time. FIG. 7 shows that in the above embodiment, the base station frequency is 89
This shows the current distribution when a signal of 0 MHz is input, and FIG. 8 is a diagram showing the radiation pattern at that time. FIG. 9 is a diagram showing another embodiment of the present invention, and is a diagram showing an example in which two sleeves are provided. FIG. 10 shows the current distribution when a signal is input when the frequency of the mobile station is 825 MHz in the embodiment shown in FIG. 9, and FIG. 11 shows the radiation pattern at that time. It is. FIG. 12 shows the current distribution when a signal is input when the base station frequency is 890 MHz in the embodiment shown in FIG. 9, and FIG. 13 shows the radiation pattern at that time. It is. 1.1a...Three liquid common antenna? , 2 &...
... Linear antenna, 10, lOa... First sleeve, 11.21, 31.11a, 21a... Upper end, 12
．． 22.32...Lower end portion, 20.20a...Second sleeve, 30...Third sleeve.

Claims (3)

[Claims] (1) A conductive tubular first sleeve and a second sleeve are provided on the linear antenna, the lower end of each sleeve is short-circuited to the linear antenna, and the upper end of each sleeve is open to the linear antenna. , the length of the first sleeve is set to approximately 1/4 of the in-service wavelength determined at a low frequency of the frequency band for mobile phones, and the length of the second sleeve is set to approximately 1/4 of the in-service wavelength determined at a low frequency of the frequency band for mobile phones. The antenna is set to approximately 1/4 of the in-service wavelength determined in the high frequency band, and is connected to the ground of the linear antenna from the first current node on the first sleeve at the low frequency of the car phone frequency band. At a position of approximately λ/8 to λ/4 toward
The upper end of the first sleeve is set, and at a high frequency of the frequency band for the mobile phone,
The upper end of the second sleeve is set at a position approximately λ/8 to λ/4 from the first current node on the second sleeve toward the ground of the linear antenna, and the first sleeve; With a sleeve, the length from the upper end of the second sleeve closer to the ground to the ground is set to approximately 1/4 wavelength of an approximately intermediate frequency of the frequency band for mobile phones. Three-wave shared antenna for automobiles. (2) The three-wave antenna for a vehicle with a sleeve according to claim (1), wherein the first sleeve is located below or above the second sleeve. (3) In claim (1), a third sleeve is provided on the linear antenna at a position above the upper sleeve of the first sleeve and the second sleeve, and the third sleeve is provided on the linear antenna. The lower end of the sleeve is short-circuited to the linear antenna, the upper end of the third sleeve is open to the linear antenna, and the length of the third sleeve is determined at a frequency approximately in the middle of the frequency band for mobile phones. At the predetermined frequency of the above-mentioned frequency band for car telephones,
A sleeve characterized in that the upper end of the third sleeve is set at a position approximately λ/8 to λ/4 from the first current node above the third sleeve toward the ground of the linear antenna. Three-wave shared antenna for automobiles.