JP2745877B2 - Flat patch antenna - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
In particular, the present invention relates to a flat patch antenna with an increased bandwidth.

[0002]

2. Description of the Related Art A conventional flat patch antenna is disclosed in, for example, IEICE Technical Report 1987 V
No. 53, pp. 21-24 Kanada, Goto, et al., "Axisymmetric Mode Ring Patch Antenna and Its Feeding Method" are known.

FIG. 4 is a sectional view of a conventional flat plate patch antenna of this kind. In FIG. 4, reference numeral 1 denotes a conductive ground plate serving as an earth plate, and 2 denotes a conductive patch which is disposed in parallel with the ground plate 1 at a predetermined distance and constitutes an antenna element. Reference numeral 3 denotes a power supply shaft connected to the center of the patch 2. The power supply shaft 3 uses the center conductor of the power supply cable 4, and the outer conductor of the power supply cable 4 is connected to the ground plane 1 via the power supply connector 5. . Reference numeral 6 denotes a short pin for connecting the ground plate 1 and the patch 2.

[0004]

However, in such a conventional flat patch antenna, since the feeding cable is terminated on the ground plane side with the antenna having a different impedance, it is difficult to achieve impedance matching between the two. In addition, there is a problem that the return loss is increased and the bandwidth is narrowed. For example, FIG. 5 shows that the distance p between the short pin 6 and the feed shaft 3 and the return loss are −
FIG. 5 is a frequency band characteristic diagram showing a relationship with the relative bandwidth Δf / f at 10 dB. As is clear from FIG.
In the conventional flat patch antenna, the specific bandwidth is only about 7 to 10% even if the return loss is -10 dB. FIG.
FIG. 3 shows a characteristic diagram when the diameter of the patch 2 of the conventional flat patch antenna is 0.51λ (= 162 mm) and the height of the antenna (the interval t between the patch and the ground plane) is 0.04λ (= 13 mm). And its fractional bandwidth is 7.3%.

However, when the flat patch antenna is used as an antenna for an automatic telephone, as shown in FIG. 7, the frequency band is 860 to 940 MHz, and the return loss is-.
In the case of 11.7 dB (VSWR 1.7 of Nippon Telegraph and Telephone), the relative bandwidth needs to be about 8 to 10%. However, the antenna having the characteristics as shown in FIG. 6 has no margin in the bandwidth, and if the usable band changes due to the attachment of water droplets due to rainfall, the antenna may be unusable. For example, FIG. 8 is a characteristic diagram showing the relationship between the return loss and the frequency when a water drop is present above the antenna. As shown in the figure, as the number of water drops increases, the usable frequency shifts to a lower frequency side. For this reason, when the conventional flat patch antenna is used for a mobile phone, there is a possibility that it will be easily deviated from the usage band of the mobile phone due to rainfall, and that a call cannot be made.

When the antenna shown in FIG. 4 is installed outdoors, if water such as rain stays in the power supply shaft 3 and the power supply portion of the power supply cable 4, the power supply portion may be short-circuited. Further, if the flat patch antenna is housed in the closed case 7 as shown in FIG. 9, short-circuiting of the power supply portion due to rain or the like can be prevented. However, when the temperature of the surrounding environment using the closed antenna changes, the inner surface of the case and Condensation may form on the antenna. In such a case, when the water droplet 8 generated by the dew condensation flows into the power supply portion, the power supply portion is short-circuited, and there is a problem that the function as an antenna is impaired.

Further, since the antenna characteristics also change depending on the structure of the antenna case, the method of mounting the vehicle body, and the like, unless the tuning that strictly takes into account such change factors is made, the use of the antenna becomes impossible due to a frequency shift. For this reason,
There is a problem that the degree of freedom in the case structure and the mounting position is small, and the number of steps for mounting and adjusting is increased.

An object of the present invention is to provide a flat patch antenna capable of widening a use bandwidth.

[0009]

The present invention will be described with reference to FIG. 1 showing the configuration of an embodiment. The present invention is directed to a patch 11 which is an antenna element and is separated from the patch 11 by a predetermined distance in parallel. Placed base plate 12 and patch 11
The present invention is applied to a flat patch antenna having a power supply shaft 13 for supplying power to the power supply and a short pin 14 conducting between the patch 11 and the ground plane 12. Then, a part of the base plate 12 is
The above object is achieved by forming a hollow cone (17) having a side as a top and an open bottom, and installing the power supply shaft 13 through the top of the hollow cone 17.

[0010]

The hollow conical portion is formed concentrically with the feed shaft, and the hollow conical portion and the feed shaft constitute a coaxial line having good impedance matching with the antenna. As a result, the return loss decreases, the fractional bandwidth increases, and the bandwidth used by the antenna increases. In the section of the means for solving the above problems and the operation which describe the configuration of the present invention, a diagram of one embodiment is used for easy understanding of the present invention. It is not limited to the form.

[0011]

1 to 3 show an embodiment of the present invention. FIG. 1 is a sectional view and FIG. 2 is a plan view.
1 and 2, the flat patch antenna 10 includes:
A disk-shaped patch 11 serving as an antenna element, a ground plate 12 serving as an earth plate disposed in parallel with the patch 11 at a predetermined interval, a feed shaft 13 for feeding power to the patch 11, and a plurality of conductors which conduct between the patch 11 and the ground plate 12. Short pin 14
Is provided. Then, a conical raised portion 17 is directly formed on the main plate 12 by pressing or the like, and the patch 1
A short feed shaft 13 projects from the top of the raised portion 17 near the lower surface of 1 to the back surface of the raised portion 17. Further, the center conductor of the power supply cable 15 is connected to the protruding end, and the outer conductor of the power supply cable 15 is fixed in the raised portion 17 by the earth band 21.

The hollow conical ridge 17 is formed concentrically with the feed shaft 13, and the ridge 17 and the feed shaft 13 constitute a coaxial line with good impedance matching with the antenna. As a result, the return loss decreases, the fractional bandwidth increases, and the bandwidth used by the antenna can be expanded.

FIG. 3 shows that the thickness of the raised portion 17 is about 0.5 mm or more and the diameter of the patch 11 is 0.51λ (= 162
mm), antenna height (interval t between patch 11 and ground plane 12)
Is a characteristic diagram showing the relationship between the return loss and the frequency of the flat patch antenna 10 when the diameter of the bottom side of the raised portion 17 is set to 0.17λ (= 55 mm) and 0.04λ (13 mm). is there. As is clear from FIG.
The fractional bandwidth at a return loss of -11.7 dB is 1
It was 6.6%, which is more than double that of the conventional antenna, and it was recognized that the bandwidth was greatly expanded.

Therefore, even if the usable frequency band changes as shown in FIG. 8 due to rainfall or the like, the flat patch antenna 10 of this embodiment can be used for a mobile phone, and strict tuning as in the prior art is unnecessary. become. Further, in the flat plate patch antenna 10 of this embodiment, a wider band can be achieved by increasing the interval t between the patch 11 and the ground plane 12. In this case, the broadening ratio can be further increased by the synergistic effect of the hollow conical raised portion 17 and the one obtained from the feed shaft 13.
This has been confirmed by experiment. Further, when the antenna of the present embodiment is used outdoors, even if water such as rain sprinkles on the antenna, the power supply portion is covered by the hollow conical ridge 17, so that the power supply portion is short-circuited by water droplets. Can be prevented beforehand.

Further, the raised portion 1 is formed by utilizing a part of the base plate 12.
By forming 7, the raised portion 17 can be formed at a low cost by a press or the like, and it is possible to cope with mass production. Furthermore, since a space is formed on the back side of the raised portion 17, the power supply unit can be accommodated in this space. That is, since the last train does not protrude to the back side of the main plate 12, the antenna can be easily installed even in a place where the height of the antenna is restricted, and is also suitable for the case where the antenna is housed in a sealed case or the like.

Even when the flat patch antenna 10 of this embodiment is used by being housed in a sealed case as shown in FIG. 9, the inner surface of the case and the surface of the antenna 10 are changed due to a temperature change of the surrounding environment. The condensed water drops as water droplets. Among them, the water droplets near the power supply portion flow down along the inclined surface of the hollow conical raised portion 17. For this reason, it is possible to prevent the power supply unit from being short-circuited by water droplets, and the function of the antenna is not impaired.

In the above embodiment, the shape of the raised portion 17 is not limited to a conical shape, but may be a shape such as a pyramid or a shape whose diameter changes stepwise. Further, the material of the ground plate including the patches and the raised portions may be a metal such as copper or aluminum, or a material obtained by plating a resin surface with a conductor.

[0018]

As described above, according to the present invention, a part of the ground plate is formed in a hollow cone shape with the patch side as the top and the bottom surface is opened, and the power supply shaft passes through the top of the hollow cone. Since it is installed, the hollow conical portion is formed concentrically with the feeding shaft, and the hollow conical portion and the feeding shaft constitute a coaxial line having good impedance matching with the antenna. This allows
The return loss is reduced, the fractional bandwidth is increased, and the bandwidth used by the antenna can be expanded. In addition, when this antenna is used outdoors, even if water such as rain splashes on it, the feeding part is covered by the hollow cone, preventing the feeding part from being short-circuited by water droplets. it can. Further, according to the present invention, a part of the base plate can be formed into a hollow conical shape at low cost by press working or the like, and it can be used for mass production. Furthermore, the power supply unit is accommodated in the hollow conical portion, and can be easily installed in a place where the height of the antenna is limited.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a flat patch antenna according to an embodiment.

FIG. 2 is a plan view of the flat patch antenna shown in FIG.

FIG. 3 is a characteristic diagram illustrating a relationship between a return loss and a frequency of the antenna according to the present embodiment.

FIG. 4 is a sectional view of a conventional flat patch antenna.

FIG. 5 is a frequency band characteristic diagram of a conventional antenna.

FIG. 6 is a characteristic diagram showing the relationship between return loss and frequency in the related art.

FIG. 7 is an NTT-specified VSW which is a band characteristic of an automobile telephone.
It is a characteristic diagram at the time of R = 1.7.

FIG. 8 is a diagram showing a change in characteristics of a flat patch antenna due to rainfall.

FIG. 9 is a cross-sectional view showing a case where a conventional antenna is housed in a sealed case.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 flat patch antenna 11 patch 12 ground plane 13 feed shaft 14 short pin 15 feed cable 17 ridge

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor: Masanori Saito Nissan Motor Co., Ltd., 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture (56) References JP-A-2-270405 (JP, A) Japanese Utility Model 2 -120910 (JP, U)

Claims (1)

(57) [Claims] 1. A patch, which is an antenna element, has a ground plane disposed in parallel with a predetermined distance from the patch, a feed shaft for feeding power to the patch, and a short pin that conducts between the patch and the ground plane. In the flat-plate patch antenna, a part of the ground plane has the patch side as a top and a bottom face is opened.
Into a hollow conical shape, and the power supply shaft is apex of the hollow conical portion.
A flat patch antenna characterized by being installed so as to penetrate a part .