JPH0373604A - Flat antenna for automobile - Google Patents

Abstract

PURPOSE:To make the length of the antenna for a broad band and for automobile telephone system shorter than that of a conventional rod antenna and to obtain the gain of the degree not imposing hindrance on the practical use by arranging a 3-flat plate antenna nearly in the middle of a cut-hole of a metallic plate and arranging a 3rd flat plate to the same height as that of the metallic plate. CONSTITUTION:A 3-flat plate antenna A is arranged nearly in the middle of a cut-hole 1h of a metallic plate 1 and a 3rd flat plate 30 of the 3-flat plate antenna A is arranged to nearly the same height as that of the metallic plate 1. Moreover, a diameter of the cut-hole 1h is selected to be 3-10 times the diameter of the 3rd flat plate 30 and the metallic plate 1 is substantially the metallic body of an automobile. The 3-flat plate antenna A consists of a 1st flat plate 10, a 2nd flat plate 20 and the 3rd flat plate 30 being nearly circular and arranged in parallel with each other, a cylindrical outer circumferential device 30, a matching short-circuit rod 50 and a feeding connector 70. The antenna is structured to be between a rod antenna and a flat plate antenna, the length is shorter than that of a conventional 1/4 wavelength rod antenna for a broad band for an automobile telephone set and the gain is equal to or more than the gain of the said rod antenna.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a flat antenna for automobiles.

[Prior Art] Conventional wideband antennas for car telephones include rod-shaped antennas and flat antennas.

[Problem to be Solved by the Invention 1] In the above-mentioned rod-shaped antenna, in order to obtain a predetermined sensitivity, the antenna length has to be long, and the antenna comes into contact with garages and roadside trees, and also has to be exposed to wind deflections on expressways. There is a problem with loud noise.

On the other hand, when a flat antenna is completely flat, there are problems in that the gain is small, the directivity is upward, and the sensitivity in the horizontal direction is low.

SUMMARY OF THE INVENTION An object of the present invention is to provide a flat antenna for automobiles that is shorter than conventional rod-shaped antennas for wideband use in automobile telephones, can obtain a gain that does not cause any practical problems, and has high sensitivity in the horizontal direction. It is something to do.

[Means for Solving the Problems] The present invention provides a first flat plate, a second flat plate, and a third flat plate, which are installed parallel to each other in this order, a through hole is provided in the center of the first flat plate, and a core wire extends from the center of the third flat plate. a cylindrical peripheral device that contacts and penetrates the center of the second flat plate, passes through the through hole of the first flat plate without contacting it, and extends from the peripheral edge of the first flat plate toward the second flat plate; A three-plate antenna having a matching short-circuit rod connecting the peripheral edge of the third flat plate with the peripheral edge of the third flat plate is placed approximately in the center of the missing hole in the metal plate, and the third flat plate is placed at approximately the same height as the third flat plate. It is what is placed.

[Function] In the present invention, the three-plate antenna is arranged approximately at the center of the defective hole in the metal plate, and the third flat plate is arranged at approximately the same height as the metal plate, so that it can be used for wideband use in automobile telephones. It is shorter than the conventional rod-shaped antenna, can obtain a gain that does not pose a problem in practical use, and has high sensitivity in the horizontal direction.

Embodiment 1 FIG. 1 (1) is a plan view showing an embodiment of the present invention, and FIG. 1 (2) is a longitudinal cross-sectional view of the above embodiment taken along line II.

In this embodiment, the three flat antennas A are placed approximately in the center of the missing hole 1h of the metal plate l, and the third thousandth plate 30 of the three flat antennas A is placed at approximately the same height as the metal plate l. It is something that exists.

In addition, the diameter of the missing hole 1h is 3 to 3 of the diameter of the third thousandth plate 30.
10 times, and the metal plate l is a metal pode of a car.

FIG. 2 is a front view showing an example of the three-plate antenna A in the above embodiment, and FIGS. 3 and 4 are, respectively,
3 is a left side view and a plan view of a flat antenna A. FIG.

This three-plate antenna A includes a first flat plate 10, a second flat plate 20, and a third flat plate 3, which are approximately circular and arranged parallel to each other.
0, a cylindrical outer circumference 40, a matching shorting rod 50, and a power supply connector 70.

The first flat plate 10 has a through hole 11 in its center portion, and is connected to the outer cover side conductor of the power supply connector 70 . The core wire 71 of the power supply connector 70 is inserted through the through hole 11 .

The second flat plate 20 has a through hole 21 in its center, the radius of which is slightly smaller than that of the first flat plate IO, and the core wire 60 is inserted through the through hole 21 while being in contact with the second flat plate 20. Note that the radius of the second thousandth plate 20 may be greater than or equal to the radius of the first thousandth plate IO.

The third flat plate 30 has one end of the core wire 60 connected to its approximately center, and has approximately the same area as the second thousand plate 20.

The matching shorting rod 50 connects the third flat plate 30 and the first flat plate IO, and is not in contact with the second flat plate 20.

The other end of the core wire 60 is connected to a core wire 71 of a power supply connector 70.

Note that the area of the first flat plate IO may be the same as or larger than the area of the second thousandth plate 20° and the third thousandth plate 30.

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

The above embodiment has a structure intermediate between a rod antenna and a flat plate antenna, and the elevation angle directivity is 20 to 30 degrees, but depending on the situation of the 10th plate 10 (ground plate), it can be lower than that. It is. Further, in the above embodiment, the sensitivity decrease from the maximum radiation direction in the horizontal direction is 5 dB or less. This state is shown in FIG.

In addition, in the above embodiment, the uniformity of horizontal plane orientation is good <(1 d
As shown in FIG. 6, when the SWR is 1.5 and the receiving center frequency is 900 MHz, the band is 180 MHz.

The above embodiment is shorter than the conventional 174-wavelength rod-shaped antenna for wideband use in automobile telephones, and can obtain a gain equal to or greater than that of the rod-shaped antenna.

Note that FIG. 6 shows the characteristics obtained when an experiment was conducted by placing a metal plate of about 380×380u+ under the three-plate antenna A in the above embodiment.

In the above embodiment, the thickness and height of the core wire 60 determine the fundamental tuning frequency. In addition, when the fundamental tuning frequency is kept constant, the first plate lO1, the second thousand plate 20. The larger the area of the third flat plate 30, the lower the height of the entire antenna (the height from the first flat plate 10 to the third flat plate 30). Note that even if the size of the first flat plate 101 and the second thousandth plate 20 is changed, the basic tuning frequency will change.

Also, if the disk shapes of the first thousandth plate 10 and the third thousandth plate 30 are made slightly smaller, and the height of the three flat plate antennas A is determined appropriately,
A resonator is constituted by the first flat plate 10 and the second thousandth plate 20, and a resonator is constituted by the second flat plate 20 and the third thousandth plate 30. A wideband antenna is created.

Further, by providing the matching shorting rod 50 and the cylindrical outer circumferential device 40, return loss can be increased and matching with the power supply line can be improved.

FIG. 7 shows that in the above embodiment, the second flat plate 20 is moved to the third thousandth plate 3 without changing the interval between the first flat plate 10 and the third flat plate 30.
If you shift it toward 0, the sub-resonance point will shift toward higher frequencies,
FIG. 3 is a diagram showing that the bandwidth at this time is 50 MHz or less.

Further, a large metal plate such as a metal body may also be used as the first thousandth plate 10. In this case, the cylindrical outer circumferential device 40 provided on the first flat plate 10 has approximately the same diameter as the third thousandth plate 30. It is necessary to do so.

Furthermore, the power supply connector 70 may be omitted, the outer conductor of the coaxial feeder (power supply line) may be directly connected to the first flat plate 10, and the core wire 71 of the coaxial feeder may be directly connected to the core wire 60.

In the above embodiment, the matching shorting rod 50 is not connected to the second flat plate 20, but the mutual distance between the first flat plate IO, the second flat plate 20, and the third flat plate 30, and each flat plate 1
The matching shorting rod 50 and the second thousandth plate 20 may be connected by adjusting the dimensions such as the radius of the O120, 30.

In addition, in the above embodiment, the first flat plate lO, the second thousandth plate 2
0. Although the third thousandth plate 30 is a perfect circle, it may have a shape other than a perfect circle such as an ellipse or a square.
20.30 may be eccentric to each other.

Note that by providing the cylindrical outer circumferential device 40.

The height of the entire antenna can be reduced. Further, when the matching shorting rod 50 is provided, multiple resonance (bimodal characteristics) is clearly produced, and when the cylindrical outer circumferential device 40 is provided, the return loss becomes large while maintaining the single-modal characteristics. If both the matching short-circuit rod 50 and the cylindrical outer circumferential case 40 are not provided, the band will be narrower, but there is room for use as an antenna for a car phone.

In FIG. 1(2), the missing hole 1h is a missing part of the metal plate 1, and the recessed part is formed by the falling plate 1c and the bottom plate 1.
d, and the falling slope 1c may be made of metal or other material.

The bottom plate 1d may be made of metal or something other than metal, and if it is made of metal, a through hole corresponding to the through hole 11 is provided in the center thereof, and the first flat plate 10 may be omitted. good,
Note that FIG. 1 shows an example in which a coaxial cable (mobile phone cable) 80 is directly connected to the three-plate antenna A without using the power supply connector 70.

In the above embodiment, when a car pode is used as the metal plate 1, a very small portion of it is cut off to form a hole th, and that part is covered with a synthetic resin such as plastic with low radio wave loss. Incidentally, there is a tendency for the top lid of a trunk to be made of plastic, and in this case, by pasting the embodiment shown in FIG. 1 on the inside of the lid, a protrusion-free antenna can be easily realized.

By the way, if an antenna that uses vertical polarization is buried below the metal plane, the directivity will be significantly upward and loss will increase, making it unsuitable as an antenna for radio waves arriving from a horizontal direction. .

However, as in the above embodiment, the triple-tuned three-plate antenna A made up of three flat plates is embedded in the missing hole 1h of the metal plate l, and the diameter of the missing hole 1h is set to the diameter of the three-flat antenna A. If it is set to about 5 times as much, the vertical directivity will not deteriorate, but if the dimensional relationship is appropriately set, the vertical directivity will actually improve.

FIG. 8(1) is a plan view showing another embodiment of the present invention, and FIG. 8(2) is a longitudinal cross-sectional view taken along the line ■-■ in FIG. 8(1).

The embodiment shown in FIG. 8 is basically the same as the embodiment shown in FIG. 1, but differs from the embodiment in FIG. 1 in that a metal plate 2 is provided instead of the metal plate 1. different.

The metal plate 2 is provided with a closed circle slot 2s between the outer circumferential conductor 2a and the central conductor 2b. And the core of coaxial cable 90! i91 is connected to the edge of the central conductor 2b, and the jacket 92 of the coaxial cable 90 is connected to the outer peripheral conductor 2a.
is connected to the edge of the On the other hand, the coaxial cable 80 is the same as in the embodiment shown in FIG.

Further, the coaxial cable 90 is a cable for extracting signals in the FM frequency band and the AM frequency band, and the coaxial cable 80 is for extracting signals in the frequency band for car telephones (900 MHz). Note that the closed circle slot 2S has a size of about 1 m x 0.7 m.

Although the frequency band of the signal taken out by the coaxial cable 90 is lower than the frequency band of the signal taken out by the coaxial cable 80, signals other than the frequency band shown in the above example may be taken out.

In the above embodiment, when receiving with the closed circle slot 2S, the coaxial cable 80 is cut off, and when receiving with the three-plate antenna A, the central conductor 2b surrounded by the closed circle slot 2S is connected to the ground plane. and the outer circumferential conductor.

By the way, the coaxial cable 90 takes out a signal in the FM frequency band and a signal in the AM frequency band, and since the signal in the FM frequency band has a high frequency, most of the current flows through the edge of the center conductor 2b, The center part of 2b is F
Since almost no signal in the M frequency band flows and the central portion of the center conductor 2b has no effect on the FM frequency band, signals in a higher frequency band can be extracted using the coaxial cable 80. In other words, the slot antenna utilizes concentrated current flowing along the conductor gap, and since the area near the center of the central conductor 2b is not affected much, this area can be used as the grounding part of the second antenna. It can be used. Therefore, it is possible to provide a flat automobile antenna in a small area and realize it as a multiband antenna.

FIG. 9 is a bottom view showing another embodiment of the present invention.

The difference between the embodiment shown in FIG. 9 and the embodiment shown in FIG. 8 is that the coaxial cable 8° shown in FIG. 8 is divided into a coaxial cable 80a and a coaxial cable 85; 85 are inductively coupled by coils 83 and 84.

As shown in Figure 9, the coaxial cable is coiled 83.84.
By inductively coupling the coaxial cable 90, the loss of the AM frequency band signal extracted from the coaxial cable 90 is reduced. That is, the signal in the AM frequency band is a capacitive antenna, and electromotive force is generated by the capacitive component from the ground. Therefore, if there is an invalid capacitance component, the pressure will be divided by that invalid capacitance component,
Loss occurs due to the invalid capacitance component, and the coaxial cable 90
The AM frequency band extracted from the bone is reduced.

That is, in the case of the embodiment shown in FIG.
When the outer sheath of 0 and the outer circumferential conductor 2a face each other over a long distance, a large ineffective capacitance is generated between them. Due to this invalid capacity, 90 pieces of coaxial cable are taken out.
Signal components in the MM wavenumber band are greatly reduced.

On the other hand, if the coaxial cable is divided into a coaxial cable 80a and a coaxial cable 85 as shown in FIG. Even if a large capacitance is generated between the outer circumferential conductor 2a and the outer circumferential conductor 2a, that capacitance is cut off. In this case, from the perspective of the AMM waveband signal taken out via the coaxial cable 90, the only capacitance that acts as an ineffective capacitance is the stray capacitance existing between the coupling coils 83 and 84, which is at most several pF or less. , is very small when viewed from the wavelength of the AMM wavenumber band, and the loss in the AMM wavenumber band can be substantially ignored.

Note that the coil 83 and the coil 84 face each other, and the gap formed by them is the closed circle slot 2.
It is preferable to be directly below or above s, in which case the loss is minimized.

Furthermore, in the above embodiment, the closed circle slot 2s has a corner part, but if this corner part is removed and the closed circle slot 2S is constructed with a curved part,
Greater efficiency.

[Effects of the Invention] According to the present invention, it is shorter than the conventional rod-shaped antenna for wide band use for car phones, can obtain a gain that does not cause any practical problems, and has the effect of having high sensitivity in the horizontal direction. .

[Brief explanation of drawings]

FIG. 1 (1) is a plan view showing one embodiment of the present invention, and FIG. 1 (2) is a longitudinal cross-sectional view of the above embodiment taken along line II. FIG. 2 is a front view showing an example of the three-plate antenna in the above embodiment, and FIGS. 3 and 4 respectively show the three-plate antenna.
They are a left side view and a plan view of a flat plate antenna A. FIG. 5 is a diagram showing the directivity in the above embodiment. FIG. 6 is a diagram showing the return loss in the above embodiment. FIG. 7 is a diagram showing the return loss when the height of the second thousand plate 20 is changed in the above embodiment. FIG. 8(1) is a plan view showing another embodiment of the present invention, and FIG. 8(2) is a longitudinal cross-sectional view taken along the line -W in FIG. 8(1). FIG. 9 is a bottom view showing another embodiment of the present invention. 1.2... Metal plate, 1h, 2h... Missing hole. 2a...Central conductor 2S...Closed circle slot, A...3 flat plate antenna. DESCRIPTION OF SYMBOLS 10... First flat plate, 20... Second flat plate, 30... Third flat plate, 40... Cylindrical peripheral device, 50... Matching shorting rod, 60... Core wire.

Claims (6)

[Claims] (1) A first flat plate having a through hole in the center; A third flat plate installed approximately parallel to the first flat plate; A third flat plate installed approximately parallel to the first flat plate; a second flat plate installed between the flat plate and having approximately the same area as the third flat plate; connected to the center of the third flat plate, contacting the second flat plate and passing through the center; A core wire that passes through the through hole of the first flat plate without contacting it; A cylindrical peripheral device extending from the peripheral edge of the first flat plate toward the second flat plate; A peripheral edge of the first flat plate and a peripheral edge of the third flat plate. A three-plate antenna having a matching short-circuiting rod connecting the two is arranged approximately at the center of the defective hole in the predetermined metal plate, and the third flat plate of the three-plate antenna has approximately the same height as the predetermined metal plate. A flat antenna for automobiles characterized by being located at the top of the antenna. (2) The flat antenna for an automobile according to claim (1), wherein the metal plate has a closed circle slot on the outside of the cutout hole. (3) In claim (1) or (2), the distance between the first flat plate and the second flat plate, and the distance between the second flat plate and the third flat plate.
A flat antenna for automobiles that is characterized by producing complex resonance by adjusting the distance between the antenna and the flat plate. (4) The flat antenna for an automobile according to claim (1) or (2), wherein the diameter of the defective hole is 3 to 10 times the diameter of the third flat plate. (5) The flat antenna for an automobile according to claim (1) or (2), wherein the predetermined metal plate is a metal body of an automobile. (6) In claim (2), a coupling element using an induction coil is inserted in the middle of the output cable from the three flat antennas, and this induction coil is installed almost directly above or below the closed circle slot. A flat antenna for automobiles that is characterized by: