JPS5897670A - Microwave rangefinder - Google Patents

Abstract

PURPOSE:To protect antennas and to measure distances with high accuracy by thermally shielding the antennas with a heat resistant dielectric material at the thickness integer times the half wavelength of the microwaves to be used. CONSTITUTION:A protecting case 4a is made of a dielectric material such as high temp. resistant ceramics or fused silica. Bar antennas 3d are contained in the case 4, and air is fed therein through an air inlet 5a to cool the inside with the air. The thickness in the bottom part 4'a of the case 4a is selected at integer times the half wavelength of the ratio waves in the part 4'a.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a microwave distance meter, and is suitable for use in high-temperature conditions, such as when targeting a high-temperature object such as a molten metal surface, or when using in a high-temperature atmosphere. The present invention relates to a microwave distance meter that protects the antenna from this high temperature and enables highly accurate and stable measurements.

Conventionally, as a microwave distance needle, those shown in FIGS. 1 to 3 are known. In these figures, 1 is a target such as the above-mentioned molten metal surface, and the microwave emitted from the sensor consisting of an antenna is reflected as shown by 2, returns to the sensor again, and the microwave is emitted. The propagation time is measured and the distance between the sensor and the target 1 is calculated from this. As for the above-mentioned sensor, the one in Figure 1 has a metal horn antenna 3, the one in Figure 2 has a metal horn antenna with a reflector attached, and the one in Figure 3 has a metal horn antenna 3. An antenna 3c is used. Since these antennas 3a to 3c are made of metal, they can be easily cooled, but in conventional use in general high temperature conditions, it is difficult to maintain a sufficient distance from the target. When used for distance measurement such as level fluctuations at short distances, thermal shielding of the antenna becomes a new requirement.

The present invention satisfies the above-mentioned requirements for heat shielding, allows the antenna to be sufficiently protected and usable even when measuring distance to a high-temperature object at a short distance, and further eliminates the need for heat shielding to affect ranging accuracy. The aim is to provide a microwave rangefinder that can perform highly accurate and stable measurements without the need for any equipment.

That is, the microwave distance meter of the present invention is characterized in that the heat-resistant dielectric material that protects the antenna from heat shields the antenna from heat with a thickness that is an integral multiple of the half wavelength of the microwave used. It is.

First, the principle of the present invention will be explained with reference to FIG.

In Figure 4, the electric field component of the radio wave (microwave) radiated from the antenna 3 is Eo1, the reflected electric field component is Er, the electric field component that has progressed into the protective material 4 is E/, and the electric field component of the reflected wave is also the electric field component of the reflected wave. E', E is the electric field component of the radio wave transmitted through the protective material 4, E11 is the composite electric field in the first air layer.
Assuming that the composite magnetic field is Hl, the composite electric field in the protective material layer is 62, the composite magnetic field is the mountain, the composite electric field in the second air layer is E3, and the composite magnetic field is Hl, these are expressed as the following equations.

Tobi=stop 74 oz 1N, e-/46 g
−−−−−−−−(Lil. = 29
．． g-ni-1
-------(2))/'o'''-146s H+=Ni'(I!Ioe -Eve)
−−−−−−−−(3) Nl=φfu1vi6
−−−−− (4)′i≦, −]=n.

μ″+ 1 stone.−74′−(5)4′=2π/p stone,
t − (s) HB = N snow (Zl
eμmg-100, e-μ”) --(7)N,
=rwaM'--(8)"'M@
= Nl e ”” (9) u
s = Ns Zt 6/4” --
CIQN・=↓F=--a Here, f: frequency of radio wave, eo: dielectric constant in air, e
': Permittivity of sickle retainer material 4, M@: Magnetic permeability in air, M':
This is the magnetic permeability of the protective material 4.

When the above equations (1) and (2) are solved, the transmittance T of the radio wave passing through the protective material 4 is expressed as T=l ka@/k,@l snow. From this α◆ formula, we find the condition for making T the size of a moth (T = 1), 11K 4/ = 2' - (S = 1, 2, 3...) - (2
)2, r6°.

Here, A'=2trJτλ, εs=6′/ε0: specific electric rate of maintenance equipment 4, λ: spatial wavelength of radio waves.

Therefore, the optimum thickness of the protective material 4 is a value that is an integral multiple of the half wavelength of the radio wave in the protective material 4. If the thickness of the protective case made of pressure, high heat-resistant ceramics, or dielectric material such as fused silica is determined to match this value, the radio waves radiated from the antenna will proceed toward the target as if there was no protective case. , and the reflected wave also travels in the same way and reaches the antenna again.

Next, an embodiment using a protective case using the upper protection rod 4 will be explained in detail with reference to FIG.
is a dielectric rod antenna (10 (3Hz)), which is suitable for use in narrow spaces due to its small size. 4a is the above-mentioned protective case, which is made of high temperature resistant ceramics or dielectric material such as fused silica.In this protective case 4.0, Above rod antenna 3
d is stored, and the interior is air-cooled by air sent from the air port 5a and discharged from the air outlet &. The thickness of the bottom portion 4'a of the protective case 4 is selected to be an integral multiple of the half wavelength of the radio wave inside the bottom portion 4', for example 8.1 ms, as in the case of the protective material 4 described above. Note that 2 is the microwave path; 1. 6 indicates the molten metal surface serving as a target, and 6 indicates the main body of the microwave distance meter.

In the range finder shown in Fig. 5 above, the microwaves emitted from the antenna 3d are reflected by the hot water fi1g and returned to the antenna 3aK, as indicated by numeral 2, and due to the propagation time of this microwave, the antenna 3d and the hot water surface 1a are connected. However, since the thickness of the bottom portion 4- of the protective case 4a is selected as described above, there is no influence on the propagation of the microwave by the protective case 4a.

The signal processing method of the distance needle main body 6 combined with the antenna may be FM, AM, phase comparison method, etc., but in the embodiment shown in FIG. 5, the measurement results when using the phase comparison method are shown below. It is shown in Figure 6. According to FIG. 6, it can be seen that the measurement results are highly accurate and have no false colors compared to the measurement results shown in FIG. 7 when the protective case is not used.

In the above embodiment, the thickness of the bottom part 6 is 8.1 mm, which corresponds to the case where 鈲 in equation (G) is 1, but this thickness is determined by considering the radio wave transmission characteristics and thermal intensity. So 1, is 2,
3. It should be selected so that...

Furthermore, in the above embodiment, the 10QHz dielectric rod antenna 3d was used as the antenna, but as shown in FIGS. 46.

Furthermore, in the above embodiment, the protective case 4 made of a dielectric material. However, as shown in FIG. 10, a protective case 44 may be used in which the curved surface is made of metal and only the bottom plate 4 is made of a heat-resistant dielectric material having a thickness of d according to the present invention. In FIG. 10, the same reference numerals as in FIG. 5 indicate the same effect.

Since the dielectric rod antenna 3d described above is small, it is most suitable for measuring the mold level in continuous billet casting, but by providing the protective case 4G of the present invention as shown in FIG. The above measurements can be made on the wall. In the figure, 6 is the main body of the microwave distance needle, 7 is the tongue pusher, 8 is the immersion nozzle, 9 is the mold, and 10 is the molten steel.

As described above, the present invention provides a microwave rangefinder in which the antenna is sufficiently protected from high temperatures and which can perform stable measurements with high accuracy.

[Brief explanation of drawings]

1, 2, and 3 are configuration diagrams showing different conventional examples, FIG. 4 is a schematic diagram for explaining the present invention in detail, and FIG. 5 is a diagram showing one embodiment of the present invention. Fig. 6 is a characteristic diagram showing the measurement results of Fig. 5; Fig. 7 is a partial cutaway perspective view;
The figure is a characteristic diagram showing the measurement results when no protective case is used, Figures 8 to 11 each show different examples, Figures 8 and 9 are configuration diagrams, and Figure 10 is a diagram showing the measurement results when no protective case is used. is a perspective view, and FIG. 11 is a configuration diagram. 1: Target, 1.: Water surface, 3: Antenna, 3a: Horn antenna 36: /” Parabolic antenna, 3d
: Rod antenna, 4: Heat-resistant dielectric material, 4. : Protective case, 0: Protective case, 6: Microwave distance meter body. Agent: Tadashi Sato - Figure 1 Figure 2 Figure 3 Figure 6 Figure 7 (7-rv) - Listening @ Negative value (mm) Figure 8 Rod 91〉 111゛−Ichigo

Claims (1)

[Claims] In a rangefinder that measures the distance to be measured based on the propagation time during which microwaves are reflected from a high-temperature target of the object to be measured, heat-resistant dielectric materials that protect the antenna from heat are A microwave distance meter characterized by using a thick one.