JPH032976Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The invention is used for transmitting/receiving antennas in automobiles such as personal radios and car phones, and is particularly applicable to glass antennas formed on glass surfaces such as window glass. Regarding.

[Conventional technology] Conventionally, personal radios, car phones, etc.
Most UHF band transmitting and receiving antennas use vertical rod antennas.

This vertical rod antenna protrudes from the outside of the car, making it difficult to wash the car, make it easy to store in the garage, and prevent theft.
Disadvantages include breakage accidents, wind noise, and negative effects on vehicle design.

In order to eliminate these drawbacks, it is conceivable to construct a UHF band transmitting/receiving antenna using a glass antenna.

[Problems that the invention aims to solve] However, glass antennas have a safety problem in that the antenna pattern is opaque, which worsens visibility when driving a car.

SUMMARY OF THE INVENTION In view of the above drawbacks of the prior art, it is an object of the present invention to provide a glass antenna that has good visibility and eliminates the need for an impedance converter between the antenna output and the feed line.

[Means for Solving the Problems] The glass antenna according to the present invention includes an antenna element made of a transparent conductor provided on a glass surface, and a length l, a thickness d, a specific resistance ρ, and a theoretical impedance of the antenna element. Z _th and the feed line side impedance Z _p , and the width w of the antenna element is set to w=ρ·l/d(Z _p −Z _th ).

[Example] FIG. 1 shows an example of a glass antenna according to the present invention. This glass antenna is a UHF band transmitting/receiving antenna used for personal radios and car phones.

In FIG. 1, a half-wavelength dipole antenna 12 is provided on the surface of an automobile window glass 10 in a predetermined direction. This half wavelength dipole antenna 1
2 is a pair of band-shaped antenna elements 1 made of a transparent conductor such as iridium tin oxide (ITO).
4.16.

The antenna elements 14 and 16 are fixed to the automobile window glass 10 by pasting or vapor deposition. The half-wave dipole antenna 12 configured in this way has a parallel feed line 18 connected to the center side.
It is connected to a wireless device (not shown) via.

The parallel feed line 18 efficiently transmits high frequency energy. During transmission, the signal energy sent from the radio is transmitted to the wavelength dipole antenna 12.
When received, the radio waves are captured by the half-wavelength dipole antenna 12 and sent to the radio as a high-frequency signal.

By the way, the half-wavelength dipole antenna 12
The transparent conductor that forms A has resistance, so the length l _A
Even if it is approximately λ/2 (λ is one electrical wavelength determined by the conductivity of the glass and other factors), the antenna impedance Z _A changes depending on its width and thickness.

On the other hand, since the input/output rated impedance on the radio device side or the line impedance Z _p of the parallel feed line 18 is determined in advance, the half-wave dipole antenna 12 can be adjusted by appropriately setting the width and thickness of the half-wave dipole antenna 12. It becomes possible to improve the transmission efficiency by matching the impedance between the power supply line side and the feed line side.

That is, if the width of the half-wave dipole antenna 12 is w, the length l _A , the thickness d, and the specific resistance ρ, the DC resistance value R of the half-wave dipole antenna 12 is R=ρ・l _A /w・d... (1).

The antenna logical impedance of the half-wave dipole antenna 12 when ignoring the DC resistance component is
Z _th (assuming that l _A is adjusted so that the imaginary part becomes zero), the antenna impedance Z _A becomes Z _A =R + Z _th (2).

If Z _A = R + Z _th = Z _p (3) holds, where the impedance on the feed line side is Z _p , impedance matching between the antenna and the feed line side can be achieved.

Substituting equation (1) into equation (3), w is determined as w=ρ·l _A /d(Z _p . Z _th ) (3). The width of the half-wave dipole antenna 12 is
If the settings are made according to equation (3), the half-wave dipole antenna 12 and the parallel feed line 18 are matched, and a matching box is not required.

In addition, as shown in FIG. 2, when using the coaxial feed line 20 instead of the parallel feed line 18, the balun 22
(balanced-unbalanced conversion element) is inserted.

Figure 3 shows the glass antenna according to the present invention at λ/4
This is an experimental example applied to a grounded antenna, and the validity of equation (3) will be examined using this λ/4 grounded antenna.

In FIG. 3, a quarter wavelength grounded antenna 30 is provided on the surface of the glass 10 in a predetermined direction. This 1/4 wavelength grounded antenna 30 is made of a transparent conductor such as ITO pasted or vapor-deposited, and is formed into a band shape with length l _A , width w, and thickness d, and has a resistivity ρ. A transparent conductor sheet with ρ/d=2.5Ω is used in the experiment.

A ground plate 32 is provided at the lower end of the glass 10.

The length l _A of the 1/4 wavelength grounded antenna 30 is adjusted in advance so that the imaginary part of the antenna impedance becomes zero.

Figure 4 shows the DC resistance value R of the 1/4 wavelength grounded antenna 30 when w of the 1/4 wavelength grounded antenna 30 is changed, and the DC resistance value R of the 1/4 wavelength grounded antenna 30 when the DC resistance of the 1/4 wavelength grounded antenna 30 is ignored. Antenna impedance obtained by adding antenna logical impedance Z _th
This shows how _ZA changes. here, It is.

Also, FIG. 4 shows a 1/4 wavelength grounded antenna 30.
Also shown is the measured value Z _x of the actual antenna impedance when w is changed.

In Figure 4, there is a difference in the trends between Z _A and Z _x .

However, when the width is w≧8mm, Z _x ≒Z _A.
On the other hand, the input and output impedance of a general λ/4 ground antenna type radio is set to Z _p = 50,
From Figure 4, w for Z _x = 50 is approximately 10 mm, and w≧8
It is in the mm range.

Therefore, if we find w such that Z _p = Z _A from equation (4), we get
Approximately desired antenna impedance can be obtained.

When the value of w is made sufficiently large to bring the antenna impedance close to Z _th , there is almost no loss, but the antenna side becomes 36Ω and the radio equipment side becomes 50Ω, requiring an impedance matching device to be interposed between them.

On the other hand, if w is set to 13 mm in Fig. 4, Z _A ≈ 50 Ω, which results in a slight increase in loss compared to when the value of w is set sufficiently large, but has the advantage of eliminating the need for an impedance matching device. Moreover, the loss is 0.5dB according to the antenna gain measurement results.
It is of a size that does not pose a practical problem.

[Effects of the invention] As explained above, in the glass antenna according to the invention, since the antenna element is formed using a transparent conductor, the visibility through the glass is good, ensuring safe driving, and the antenna impedance and feeder line are By equalizing the side impedance, a matching box can be eliminated, reducing component costs and assembly work.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a half-wavelength dipole antenna according to an embodiment of the present invention, FIG. 2 is a schematic diagram showing a case where the feeder line used in the half-wavelength dipole antenna shown in FIG. 1 is changed, and FIG. is a schematic diagram showing a 1/4 wavelength grounded antenna according to an experimental example of the present invention,
FIG. 4 is a diagram showing the relationship between the width and impedance of the 1/4 wavelength grounded antenna shown in FIG. 3. 10...Automobile window glass, 12...Half wavelength dipole antenna, 30...1/4 wavelength ground antenna.

Claims (1)

[Claims for Utility Model Registration] An antenna element made of a transparent conductor is provided on a glass surface, and the length l, thickness d, specific resistance ρ, theoretical impedance Z _th , and feed line side impedance Z _p of this antenna element are , a glass antenna characterized in that the width w of the antenna element is set to w=ρ·l/d(Z _p −Z _th ).