JP3225490B2 - Dielectric antenna - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric antenna used as a component of a vehicle-mounted millimeter-wave radar device, and more particularly to a dielectric antenna optimal for coupling with a nonradiative dielectric line. Things.

[0002]

2. Description of the Related Art An on-vehicle radar device mounted on a vehicle such as a passenger car and used for an alarm device for preventing collisions and collisions has a distance measuring range of several hundred meters to a target such as a preceding vehicle or an oncoming vehicle. In order to avoid radiated radio waves from propagating farther than necessary or to interfere with existing microwave band communication equipment,
A radio wave in the millimeter wave band having a large propagation attenuation of about Hz is suitable. The use of the millimeter wave band is also suitable for reducing the size of the entire radar module, particularly for reducing the size of the antenna.

Conventionally, the above-mentioned millimeter-wave band radar module of about 60 GHz has been configured in the form of a microstrip line. In such a high-frequency band, radiation power from the line increases, and radiation loss increases. When the radar modules of a plurality of systems are arranged close to each other, there is a problem that mutual interference easily occurs and detection accuracy is reduced. In addition, further downsizing of radar module,
There is also a need to reduce the number of parts and thereby reduce costs.

[0004] As a new line format for solving the above-mentioned problems, the IEICE Transactions vol.J73-1, No.
3, pp 87-94 (March 1990), entitled “Millimeter-Wave Integrated Circuits Using Non-Radioelectric Dielectric Lines,” a non-radioactive dielectric line (Non- Ra
diative-Dielectric-waveguide (NRD line) is suitable. This non-radiative dielectric line follows the dielectric rod by inserting a rod-shaped dielectric (dielectric rod) between the parallel conductor plates facing each other with a spacing slightly smaller than the half wavelength of the radio wave in the operating frequency band. Only electromagnetic waves can be propagated. This non-radiative dielectric line is shielded by a parallel conductor plate in the vertical direction of the line, and the propagation of radio waves to leak to the side of the line is also cut off because the distance between the parallel conductor plates is less than half a wavelength. You.

[0005] For this reason, the power radiation from the non-radiative dielectric line is extremely small, and interference between modules in a large number of systems can be avoided. In addition, in such a non-radiative dielectric line, various components such as a directional coupler and a circulator can be easily formed by bringing the lines close to each other or adding ferrite or the like. Circuit elements can be arranged at high density. Furthermore, in such a transmitter / receiver using a non-radiative dielectric line, the tip of the dielectric rod protrudes out of the parallel conductor plate as it is, so that no complicated and large waveguide conversion unit is interposed at all. There is also an advantage that the antenna can be easily formed. For this reason, a transceiver using a non-radiative dielectric line is a conventional microwave IC (MIC).
As a result, the overall size of the module can be reduced, which is comparable to that of the first embodiment.

According to the above-mentioned paper, the transmitter and receiver antennas are, as shown in FIG. 6, a 2.5-mm-wide and 2.25-mm-high tetrafluoroethylene constituting a 60-GHz band nonradiative dielectric line. The dielectric rod 2 made of (TFE) or the like is converted into a tapered dielectric rod while projecting as a dielectric antenna 3 outside the parallel conductor plate. FIG. 6 shows a state in which the upper conductor plate is removed, and reference numeral 1 denotes a lower conductor plate.

[0007]

The above-mentioned paper does not specify whether the dielectric antenna having the structure shown in FIG. 6 is optimal in terms of VSWR and the like.
Therefore, it is an object of the present invention to achieve VS
An object of the present invention is to provide a dielectric antenna having an optimum structure in terms of WR and the like.

[0008]

A dielectric antenna according to the present invention has a portion having a constant width which is extended outside the parallel conductor plate by a constant width larger than the width of a dielectric rod constituting a non-radiative dielectric line. And an external dielectric plate comprising a tapered portion formed in front of the external dielectric plate, and a parallel width extending from the tip of the dielectric rod constituting the non-radiative dielectric line to a portion of the external dielectric plate having a constant width. An internal dielectric plate extending between the conductor plates. According to one aspect of the present invention, a metal horn having a truncated quadrangular pyramid shape in which the end surface on the root side circumscribing the external dielectric plate is enlarged in the distal direction is added.

[0009]

According to the experimental results of the inventor, according to the antenna results, an antenna in which a dielectric rod having a width of about 2.5 mm is protruded out of a parallel conductor plate while being converted into a tapered shape as it is,
The problem that VSWR was too large was confirmed. This is 60 GHz using a dielectric rod with a width of about 2.5 mm.
It is considered that the impedance of the nonradiative dielectric line in the band is too high compared to the impedance of the dielectric antenna having the same width. The width of the dielectric rod of the non-radiative dielectric line is a value set so that the single mode transmission band is maximized. Therefore, if it is attempted to reduce the impedance of the nonradiative dielectric line to about the impedance of free space by increasing the width thereof, the transmission characteristics of the nonradiative dielectric line are expected to deteriorate.

The width of the dielectric rod of about 2.5 mm is determined by inserting the tip of the dielectric rod into a waveguide having a width of about 2.5 mm of the measuring system in order to confirm the characteristics during the assembly of the transceiver. This is a convenient value from the viewpoint that the measurement system and the system to be measured can be easily coupled. This is because the non-radiative dielectric line is similar to a waveguide. Furthermore, when the lateral width of the dielectric rod is increased, there is a problem in that the dimensions of various components such as an isolator increase.

Therefore, according to the present invention, the width of the dielectric rod constituting the non-radiative dielectric line is fixed to a value which optimizes the transmission characteristics of the non-radiative dielectric line, and the external dielectric constituting the antenna is fixed. The width of the plate is set to a large width to obtain a value close to the characteristic impedance of free space,
In order to couple a dielectric rod having a small width to an external dielectric plate having a large width, an internal dielectric plate having a tapered portion is interposed. Thereby, an optimal dielectric antenna having a small VSWR is realized. Hereinafter, the present invention will be described in detail with reference to examples.

[0012]

1 is a plan view showing a dielectric antenna according to one embodiment of the present invention together with a non-radiative dielectric line. Reference numeral 10 denotes a lower conductor plate constituting the non-radiative dielectric line, and 20 denotes a non-radiative dielectric line. This is a dielectric rod made of tetrafluoroethylene, which constitutes the dielectric line. FIG. 1 shows a state in which the upper conductor plate constituting the non-radiative dielectric waveguide is removed, and the end of the upper conductor plate is arranged so as to coincide with the end of the lower conductor plate 10. The dielectric antenna 30 according to this embodiment includes an external dielectric plate 31 made of ethylene tetrafluoride, an internal dielectric plate 32, and a metal horn 33.

The outer dielectric plate 31 is extended outside the upper and lower conductor plates forming the non-radiative dielectric line at a constant width larger than the width of the dielectric rod 20 forming the non-radiative dielectric line. It has a width portion and a tapered portion formed in front of the width portion. Also,
The internal dielectric plate 32 extends between the parallel conductor plates while linearly increasing the width from the tip of the dielectric rod 20 constituting the non-radiative dielectric line to the portion of the external dielectric plate 31 having a constant width. . The metal horn 30 includes an external dielectric plate 31
It has a truncated quadrangular pyramid shape in which the end face on the root side circumscribing the base is enlarged in the tip direction.

When the center frequency is 60 GHz, the preferred width of the dielectric rod constituting the non-radiative dielectric line is
2.35 mm, the spacing between the parallel conductor plates and thus the thickness of the dielectric rod is 2.2 mm. In this case, the optimum shapes of the outer dielectric plate 31 and the inner dielectric plate 32 for minimizing the VSWR were as shown in FIG. That is, the optimum width of the outer dielectric plate 31 is 7.0 mm, which is almost three times the width of the dielectric rod 20, the length of the constant width portion is 10mm, and the length of the tapered portion at the tip is 5mm. Was. The longer the tapered portion of the internal dielectric plate 31 is, the better, but about 10 mm is enough for a sufficiently small VSWR characteristic. The minimum VSWR was obtained when the boundary surface between the outer conductor plate 31 and the inner conductor plate 32 was shifted 1.5 mm ± 0.5 mm from the end of the parallel conductor plate to the inside of the conductor plate.

VS for a dielectric antenna composed only of a dielectric plate having the dimensions shown in FIG. 2 (without adding a metal horn)
The WR was measured. FIG. 4 shows the measurement results. For comparison, the width of the constant width portion of the external dielectric plate was reduced by almost half.
FIG. 5 shows the measurement results of the VSWR when the distance was reduced to 4 mm. Note that the VSWR was also measured for a dielectric antenna having a structure in which the dielectric rod was projected outside the parallel conductive plate without changing the lateral width of the external conductive plate, without changing the horizontal width.
In this case, it was confirmed that the VSWR characteristics were further deteriorated as compared with the case of FIG. From such a series of experimental results, it has been found that the increase in the lateral width of the external dielectric plate is extremely effective in reducing the VSWR.

The metal horn has a truncated pyramid shape as shown in FIG. The width of the opening on the terminal side of the metal horn is b, the height is a, the width of the opening on the tip side is W,
Assuming that the height is H and the length is D, three types of combinations of dimensions of each part as shown in the table on the next page are manufactured,
The characteristics of the dielectric plates were measured in combination. The following can be confirmed from the measurement results.

The addition of these metal horns slightly improves the VSWR in a portion far from the center frequency. The addition of the metal horn improves the antenna gain and suppresses the generation of the side lobe. As the values of b and D are increased, the VSWR at a position distant from the center frequency decreases.
Even if the value of D is about 25 mm, a sufficiently low VSWR is realized. Therefore, the smallest No. By using the metal horn of No. 3, the size of the entire dielectric antenna can be reduced.

[0018]

[0019]

As described in detail above, in the dielectric antenna of the present invention, the width of the dielectric rod constituting the non-radiative dielectric line is set to a value that optimizes the transmission characteristics of the non-radiative dielectric line. It is fixed and the width of the external dielectric plate constituting the antenna is set to a large width to obtain a value close to the characteristic impedance of free space, so that both the non-radiative dielectric line and the dielectric antenna are good. There is an effect that the characteristics can be realized.

Further, by adding a metal horn surrounding the external dielectric plate, there is an advantage that the antenna gain can be improved and interference with other channels due to suppression of the side lobe can be effectively avoided.

[Brief description of the drawings]

FIG. 1 is a plan view showing a dielectric antenna according to one embodiment of the present invention together with a nonradiative dielectric line to be coupled.

FIG. 2 is a plan view for explaining optimum dimensions of the dielectric plate of FIG.

FIG. 3 is a perspective view for explaining the structure of the metal horn of FIG. 1 and dimensions of each part.

FIG. 4 is experimental data showing matching characteristics of the dielectric antenna of the present invention.

FIG. 5 is a plan view showing a configuration of an FM radar module configured by applying the prior art.

FIG. 6 is a plan view showing the structure of a conventional dielectric antenna.

[Explanation of symbols]

10 Lower conductor plate 20 Dielectric rod constituting non-radiative dielectric line with upper and lower conductor plates 30 Dielectric antenna 31 External dielectric plate 32 Internal dielectric plate 33 Metal horn

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-79742 (JP, A) JP-A-50-67057 (JP, A) JP-A-4-32304 (JP, A) JP-A-49-1979 29750 (JP, A) JP-A-56-166605 (JP, A) JP-A-53-55455 (JP, U) JP-A-54-49838 (JP, U) JP-B-39-26874 (JP, B1) (58) Field surveyed (Int.Cl. ⁷ , DB name) H01Q 13/24 H01P 1/16 H01P 3/16 JICST file (JOIS)

Claims (3)

(57) [Claims] 1. A dielectric antenna for radiating radio waves transmitted from a dielectric line composed of a parallel conductor plate and a dielectric rod held therebetween or transmitting received radio waves to the dielectric line. Outside the parallel conductor plate, a portion having a constant width that is extended with a constant width larger than the width of the dielectric rod forming the dielectric line, and a tapered portion formed in front of the portion. A dielectric plate, and an internal dielectric plate extending between the parallel conductor plates while expanding the width from a tip of a dielectric rod constituting the dielectric line to a portion of a constant width of the external dielectric plate. A dielectric antenna, characterized in that: 2. A dielectric antenna for radiating a radio wave transmitted from a dielectric line comprising a parallel conductor plate and a dielectric rod held therebetween or transmitting a received radio wave to the dielectric line. An external dielectric comprising a constant width portion extending outside the parallel conductor plate with a constant width larger than the width of the dielectric rod constituting the dielectric line, and a tapered portion formed in front of the portion. A body plate, an inner dielectric plate extending between the parallel conductor plates while expanding a width from a tip of a dielectric rod constituting the dielectric line to a fixed width portion of the outer dielectric plate, and A dielectric antenna comprising: a metal horn having a truncated quadrangular pyramid shape in which a root-side end surface circumscribing a dielectric plate is enlarged in a tip direction. 3. The dielectric antenna according to claim 2, wherein the end face of the metal horn on the tip side has a substantially square shape.