JPH06350332A - Small sized transmission/reception stack antenna - Google Patents

Abstract

PURPOSE:To simply form a transmission/reception isolation filter by stacking disk antennas coaxially, mounting a ferroelectric material onto the upper side antenna to decrease the radius of the antenna thereby increasing the isolation between upper and lower antennas. CONSTITUTION:A radius r1 of an upper disk antenna A1 is selected to be smaller than a radius r2 of a lower disk antenna A2, its dielectric base S1 is made of a ferroelectric material and a radiation impedance is reduced by selecting the material with a higher dielectric constant epsilon1 no dielectric base S2 is provided, if possible. Furthermore, the radius r1 is selected as small as possible to part the circumferential parts of the antennas A1, A2 thereby securing at least isolation of 10dB. The reduction in the radiation impedance of the antenna A1 caused resulting therefrom, and then the reduction in the antenna gain is easily compensated by increasing a power amplification gain at an input and an output terminal of a communication equipment connected to the antenna.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small transmission / reception stack antenna suitable for mounting on a moving body such as an automobile or an aircraft, and in particular, two antennas individually used for transmission / reception by two frequencies adjacent to each other are provided. It is a low-profile integrated structure that maintains good isolation.

[0002]

2. Description of the Related Art A transmission / reception stack antenna in which two antennas are integrally combined so as to be able to perform simultaneous communication by transmitting / receiving at individual frequencies, can be mounted on the outer wall surface of a high-speed moving body. In addition, it is suitable to be small and have a low posture.

However, as an antenna that can be mounted on a ground conductor surface such as an outer wall surface of a moving body in a low posture, as shown in FIG. 1, a conductor flat plate having a size of a half wavelength or less, which is slightly separated from the ground conductor surface, is used. Capacitor antennas or patch antennas arranged in parallel, and, as shown in FIG. 2, a part of a parallel conductor plate is bent vertically and short-circuited to a ground conductor,
There is an inverted F antenna fed at an intermediate position of the parallel portion, and further, as shown in FIG. 3, a dielectric material is provided between the conductor disk curved along the outer wall conductor surface of the moving body such as an aircraft and the outer wall conductor surface. An antenna for a mobile body loaded with is known.

An antenna made of such a plate conductor is
As shown in FIG. 4, power is generally fed from the rear surface on the ground conductor side through a coaxial line, and as shown in FIG. 5, a pair of plate-shaped conductors symmetrically arranged with the ground conductor surface as a mirror surface. It can be treated as an omnidirectional radiation in a horizontal plane due to an electromagnetic field generated between them.

[0005]

As shown in FIGS. 6 (a) and 6 (b), in order to enable simultaneous transmission and reception by transmitting and receiving at a low frequency using the low profile antenna as described above. When stacking two antennas on the top and bottom and combining them together, the radiated electromagnetic fields of the two antennas that are placed close to each other interfere with each other, so the transmission and reception antennas cannot be isolated from each other, and the transmission and reception to and from the communication device used. It is necessary to provide a complex filter having a sharp frequency separation characteristic for separation. Especially, the transmission / reception frequency is, for example, 200 MHz.
In the case of very close proximity such as 201 MHz, it is practically impossible to obtain the required isolation between the transmitter and the receiver only by the filter.

The object of the present invention is that even if the transmission and reception frequencies are extremely close to each other, it is not necessary to equip the communication device with a complicated and expensive filter for separating the transmission and reception, and a relatively simple filter is sufficient in total. It is an object of the present invention to provide a small-sized transmission / reception stack antenna suitable for mounting on a moving body, which is configured to obtain necessary isolation between transmission / reception antennas so that transmission / reception can be separated.

That is, in the small-sized transmitting / receiving stack antenna of the present invention, two conductor plates, which are sequentially spaced parallel to each other on the ground conductor plane and are arranged adjacent to each other substantially coaxially in the vertical direction, are individually fed as radiators. By loading a ferroelectric material or a ferromagnetic material on almost the entire surface between the conductor plates to reduce the conductor plate, the electromagnetic field generated at the peripheral edge of the lower conductor plate is attenuated exponentially by at least 10 dB. It is characterized in that the peripheral edge of the conductor disc or the conductor ring on the upper side is located in the region.

[0008]

Therefore, in the small transmission / reception stack antenna according to the present invention, even if both flat plate-shaped transmission / reception antennas are stacked substantially coaxially and are arranged close to each other in a low position, the required isolation can be obtained between them, and it is compared with a communication device. Sufficient transmission / reception separation can be achieved even by using a simple filter.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.
The details will be described. The small transmission / reception stack antenna of the present invention is
Basically, as shown in Fig. 6 (a) and (b), grounding
Common dielectric substrate S on conductor G or individual dielectric substrate
Board S₁And S₂Stack up close to the top or hollow
Flat plate antenna A₁And A₂Coaxial feeder F₁Oh
And F₂Conventional small stacker
The configuration is similar to Tena. In addition, the lower disk-shaped antenna
Na A₂Is an annular antenna A, as shown in FIG.₃
It is also possible to use the upper and lower disc-shaped antennas A ₁Oh
And A₂At the center of the, as shown in Figure 7 (b),
Ki A_FourAnd A_FiveAnd set the radius of the disc part
It can also be reduced.

Regarding the disk-shaped antennas A ₁ and A ₂ which are vertically stacked as shown in FIG. 6B, the radii are r _{1 and} r ₂ and the dielectric substrate S is as shown in FIG. 8A. Assuming that the heights of _{1 and} S ₂ are h ₁ and h ₂ and the permittivities are ε _{1 and} ε ₂ , the vertical electric field generated at the peripheral edge of the disk-shaped antenna is E _{1 and} E ₂ as shown in FIG. 8 (b). _{If 2} , the magnetic field is generated in the circumferential direction orthogonal to the electric field. In this state, the disk-shaped antenna A _1,
Radiation impedance R _1, R ₂ of A ₂ is represented by the following formula (1) A as proportional constant.

[Equation 1] Therefore,

[Equation 2] On the other hand, the sequential capacitances C ₁ and C ₂ between the disk-shaped antennas A _{1 and} A ₂ and the ground conductor G are expressed by the following equation (3).

[Equation 3] Therefore,

[Equation 4] By substituting the relationship of equation (4) into equation (3), the following relationship of equation (5) is obtained.

[Equation 5]

The radiated electric field of the disk-shaped antenna exhibiting the radiation impedance of the above relation is as shown in FIG. 9 (a).
The electric field strength generated in the vertical direction from the peripheral edge of the conductor disk toward the opposing conductor and inwardly decays exponentially as shown in FIG. 9 (b). Therefore, in order to obtain a sufficient isolation between the _two disk-shaped antennas A _{1 and} A ₂ that are stacked vertically and arranged close to each other, in order to obtain a sufficient isolation between the disk-shaped antennas A ₂ and A ₂ , the peripheral area of the larger lower disk-shaped antenna A ₂ is The peripheral edge of the smaller upper disk-shaped antenna A ₁ is located in a region where the electric field strength of the generated radiated electric field is sufficiently attenuated, and it is necessary to avoid the influence of the lower disk-shaped antenna A ₂ as much as possible. .

[0012] To that end, the upper disc-shaped antenna A _1, relative to the lower disc-shaped antenna A _2, together with the smaller radius r _1, the dielectric constant of the dielectric substrate S ₁ in the formula (5) epsilon _It is preferable to increase ₁ relatively as much as possible and reduce the radiation impedance. That is, the dielectric substrate S ₁ in contact with the upper disc-shaped antenna A _1, for example as to constitute a ferroelectric material or a ferromagnetic material such as barium titanate, if the lower disc-shaped antenna A ₂ dielectric The body substrate S ₂ is not provided, and the radius r ₁ of the upper disc-shaped antenna A ₁ is selected to be as small as possible.
The peripheral portions of the upper and lower anteers A _{1 and} A ₂ are separated as much as possible to ensure at least 10 dB of isolation. The resulting upper antenna A ₁
The decrease in the radiation impedance of the antenna, and therefore the decrease in the antenna gain, can be easily compensated by the increase in the power amplification gain at the input / output end of the connected communication device.

Further, although the radiated electric field in the capacitor antenna composed of the conductor disk as shown in FIGS. 8 (a) and 8 (b) exhibits a non-directional directivity in the horizontal plane, it has the symmetrical arrangement shown in FIG. When the ground conductor surface G, which is a symmetrical mirror surface in the virtual antenna pair, has a finite size, such as the outer wall surface of the moving body, the central axis of the directivity pattern in the vertical plane deviates upward from the horizontal direction. In addition, the antenna gain in the horizontal direction actually required for communication is considerably reduced.

In the small-sized transmitting / receiving stack antenna of the present invention, in order to compensate for the decrease in antenna gain due to the fact that the size of the ground conductor G is finite in the actual equipment state as described above, FIG. As shown in (b) and (b), the central axis of the directivity pattern in the vertical plane is made almost equal by bending the peripheral portions of the upper disc-shaped antenna A ₁ and the lower disc-shaped antenna A ₂ inward inward, respectively. It is corrected in the horizontal direction so that the maximum antenna gain is obtained in the horizontal direction in which communication is actually performed.

Next, according to the present invention, as shown in FIGS. 6 (a) and 6 (b), a transmitter / receiver antenna in which a radiator made of a conductor disk is coaxially stacked and a ferroelectric substance is loaded is manufactured, The result of measuring the isolation between transmission and reception will be described.

As shown in FIG. 11, the prototype small transmitting and receiving stack antenna has a lower antenna A ₂ composed of a conductor disk having a diameter of 150 mm arranged parallel to and separated from the ground conductor surface G by 12 to 13 mm, and further 10 mm. 100m apart in parallel
The upper antenna A ₁ made of a conductor disk of m is coaxially arranged,
Upper and lower antennas A _1, loaded with epoxy glass plate having a thickness of 6mm between A ₂ as ferroelectric, separately via a double coaxial feeder F the prototype, is coaxial feed respectively above and below the antenna A _1, A ₂ It is configured as follows.

The results of measuring the isolation between the upper and lower antennas A ₁ and A _{2 of the} prototype transmission / reception stack antenna are shown in FIGS. 12 (a) and 12 (b). Figure 12 (a)
In (b) and (b), when the upper antenna A ₁ and the lower antenna A ₂ are fed, respectively, the characteristic curve 1 shows the frequency characteristic of the isolation viewed from the feeding antenna, and the characteristic curve 2 Is the return loss based on the coupling of the other antenna viewed from the feeding antenna, that is, the frequency characteristic of the return loss,
It shows the matching state on the side of the feeding antenna at the center frequency shown by the vertical dotted line.

According to the measurement results shown in FIGS. 12 (a) and 12 (b), the antenna can be seen from both sides of the upper and lower antennas A ₁ and A ₂ even in a good matching state with respect to the same frequency. Isolation of about 15 dB is obtained only in the system. Therefore, when the transmission / reception frequencies are actually separated from each other, the transmission / reception frequencies are close to each other only by providing a relatively simple transmission / reception separation filter having a separation characteristic that is normally used at the input / output ends of the transceiver. Even if there is, it is possible to ensure a good communication state by performing sufficient transmission / reception separation.

Incidentally, the measurement results shown in FIGS. 12 (a) and 12 (b) for the prototype antenna of the size shown in FIG.
It was designed and measured for 000MHz, but as mentioned at the beginning, when it is used near a frequency of 200MH, the size of the whole stack antenna for transmitting and receiving is reduced to the same level as shown in Fig. 11, for example. Designed to be as small as
It is preferable that the same measurement result as that shown in FIGS. 12 (a) and 12 (b) is obtained.

To this end, a capacitance forming element is loaded by mounting an annular conductor plate as shown in FIG. 7 in place of the conductor disc which constitutes the small-sized transmitting / receiving stack antenna of the present invention, or a conductor disc. It is preferable to greatly reduce the radius of the conductor disc or the conductor ring by, for example, configuring the ferroelectric material loaded on the substrate with ferrite having a particularly large dielectric constant.

[0021]

As is clear from the above description, according to the present invention, the transmitting and receiving antennas composed of small conductor disks are vertically stacked and coaxially arranged close to each other, so that they are suitable for mounting on the outer wall surface of the moving body. Even if the transmission / reception frequencies individually selected for simultaneous communication are extremely close to each other, it is sufficient to use a relatively simple transmission / reception separation filter for the communication device to achieve sufficient transmission / reception separation. As a result, it is possible to secure a sufficient isolation between the transmitting and receiving antennas so that a particularly remarkable effect can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing a schematic configuration of a capacitor (patch) antenna.

FIG. 2 is a perspective view showing a schematic configuration of an inverted F Annate.

FIG. 3 is a cross-sectional view showing a schematic configuration of a mobile unit antenna.

FIG. 4 is a diagram showing a form of back feeding of a capacitor antenna.

FIG. 5 is a diagram showing the operating principle of the capacitor antenna.

6 (a) and 6 (b) are cross-sectional views each showing an example of the basic configuration of the small-sized transceiver stack antenna of the present invention.

7A and 7B are cross-sectional views each showing another example of the same basic configuration.

8 (a) and 8 (b) are a cross-sectional view and a perspective view, respectively, showing the operating principle of the small-sized transceiver stack antenna of the present invention.

9 (a) and 9 (b) are sectional views showing the same manner of operation.

10 (a) and 10 (b) are sectional views respectively showing another mode of the operation.

FIG. 11 is a cross-sectional view showing a schematic configuration of a prototype antenna.

12A and 12B are characteristic curve diagrams showing measurement results of the prototype antenna, respectively.

Claims (4)

[Claims] 1. Two conductor plates, which are spaced apart in parallel on the ground conductor surface and are arranged substantially coaxially in the vertical direction, are individually fed as radiators, and substantially the entire surface between the upper and lower conductor plates is supplied. By loading a ferroelectric material or a ferromagnetic material on the conductor plate to reduce the conductor plate, the conductor plate on the upper side is arranged in a region where the electromagnetic field generated around the periphery of the conductor plate on the lower side is exponentially attenuated by at least 10 dB. A small transceiver stack antenna, characterized in that the periphery of the antenna is located. 2. The small transmission / reception stack antenna according to claim 1, wherein a capacitance forming element is loaded on at least a central portion of the upper conductor plate to reduce the conductor plate. 3. The small transmitting / receiving stack antenna according to claim 1, wherein ferrite is loaded on substantially the entire surface of at least the upper conductor plate to reduce the conductor plate. 4. The small transceiver stack antenna according to claim 1, wherein at least a peripheral portion of the upper conductor plate is bent downward inward.