JPS62177467A - Microwave distance measuring instrument - Google Patents

Abstract

PURPOSE:To reduce the size and weight of a device by stabilizing modulation width from a microwave oscillator by temperature correction. CONSTITUTION:A microwave with specific modulation width from the microwave oscillator 21 is transmitted from a transmitting antenna 24 to an object 26 to be detected. A reflected wave received by a receiving antenna 27 and a part of a sent wave from a branching filter 23 are inputted to a mixing branching filter 25 and then a beat signal corresponding to the difference in path length between both waves is generated. This heat signal is counted by a counter 28 and an arithmetic processing system 29 measures the distance from the antenna 24 to the object 26. If the operation temperature of the oscillator 21 varies from the specific modulation width, this temperature variation is detected by a temperature sensor 30 and a signal corresponding to the detected temperature is inputted from a converting circuit 31 to a bias voltage arithmetic circuit 32. Then, a specific bias is sent out from a circuit 32 to a modulating bias circuit 22 to recover the modulating width to a specific value. Then, a temperature correcting circuit is provided to eliminate the need for the device of a calibration system, thereby reducing the size and weight of the instrument.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an apparatus for measuring the level of high-temperature Takamatsu dust in an environment such as raw material in a blast furnace or molten steel in a converter.

Prior Art and its Problems] There is a radar device that uses FM (frequency modulation) waves as a device for measuring distance.

When an FM wave is transmitted to a target object and a reflected wave is received from this object, the frequency of the received wave will change depending on the time required for the transmitted wave to travel back and forth to the target object. It shifts. Therefore, when a part of the received wave and the transmitted wave are mixed and detected, a beat signal (beat wave) with a frequency corresponding to the frequency shift is generated, so by counting the wave number of this beat wave, the distance to the object can be determined. is being calculated.

When the measurement distance is d and the number of waves per modulation period of the heat wave is N, the following relational expression holds: d=N-c/4ΔF. However, C is the speed of light, and ΔF is the frequency modulation width of the transmitted wave.

By the way, as is clear from this equation, the output signal of the FM radar is inversely proportional to the frequency modulation width ΔF, so if the transmitter is affected by temperature changes and the modulation width ΔF drifts, this cannot be ignored with respect to the measurement distance. This will cause an error.

In particular, when this measuring device is applied to high-temperature furnaces such as blast furnaces and converters, this measurement error becomes fatal.

Conventionally, a device as shown in FIG. 3 has been used to correct the above-mentioned measurement error.

l is a microwave oscillator, 2 is a microwave oscillator l
3 is a modulation signal generator for frequency modulating the microwave. 4 is a microwave switch, and by this switch 4, the microwave oscillator l
During measurement, the microwaves from the molten steel 5 are guided to a transmitting antenna 6 provided on the molten steel 5, and during calibration, the microwaves are guided to a transmitting antenna 8 for calibration provided at a predetermined distance from the reflective plate 7 for calibration.
guided by. 9 is an antenna that receives the microphone [J wave] from the transmitting antenna 6 reflected by the calibration reflector 7, and lO is an antenna for receiving the microwave from the calibration transmitting antenna 8 reflected by the calibration reflector 7. It is a receiving antenna. Reference numeral 11 denotes a microwave switch which, by switching, supplies the received signal from the receiving antenna 9 during measurement to the mixer 12, and the received signal from the calibration receiving antenna 10 during calibration to the mixer 12.

Reference numeral 13 denotes a directional coupler coupled to the output circuit from the microwave oscillator l, and the microwave obtained by this directional coupler 13 is supplied to the mixer 12. 14
is a reflection-free termination provided on the other end side of the directional coupler I3. The mixer 12 mixes the received signal from the receiving antenna 9 or the calibration receiving antenna 10 with a portion of the microwave from the microwave oscillator l,
This mixed signal is input to the counter 15 after being amplified by the amplifier IO. A modulation signal from the modulation signal generator 3 is also input to this counter 15 .

16 is a clock oscillator for the counter 15; 17 is an arithmetic circuit that processes the count value from the counter 15, and I8 is a filter provided on the output side from the arithmetic circuit 17. Reference numeral 19 denotes a control unit that controls the microwave switch 4°11.

Next, the operation of the apparatus having the above configuration will be briefly explained.

First, the control unit 19 controls the microwave switch 4.1.
1 is changed to the measurement side. Thereby, the microwave from the microwave oscillator 1 is guided to the transmitting antenna 6 and transmitted to the molten steel 5. The microwave reflected by the molten steel 5 is received by the receiving antenna 9. Therefore, the received reflected wave and the microwave from the microwave oscillator I are input to the mixer 12 via the directional coupling WSI 3, but the reflected wave is Since there is a time lag by the path length Q from the antenna 6 to the receiving antenna 9 via the molten steel 5, a beat signal with a frequency corresponding to the path length σ is generated in the mixer 12, and this beep]. The signals are counted by a counter 15, and this counter value is assumed to be X.

Next, the control unit 19 causes the microwave switching W4.1 to
+ can be changed to the calibration side. Thereby, the microwave from the microwave oscillator l is guided to the calibration transmitting antenna 8 and transmitted to the calibration reflector 7. The microwave reflected by this reflection plate 7 is received by the calibration receiving antenna IO. Therefore, compared to the signal from the microwave oscillator l, the reflected wave is temporally shifted by the length of the path from the calibration transmitting antenna 8 to the receiving antenna 10 via the reflector 7. Let Y be the count value obtained from the beat signal generated at this time.

Since the path length is a preset value, there is a relationship of 9=L・(X/Y), and as a result, the molten steel 5
You can know the level of

By providing a separate calibration system in this way, it is possible to accurately measure the molten steel level, but in order to do this, the measuring device must become more complex and larger, and be installed as an industrial meter. It was difficult.

[Object of the Invention] This invention was made to eliminate the above-mentioned problems, and provides a microwave distance measuring device with a simplified configuration by providing a temperature correction circuit and eliminating the need for a calibration system. The purpose is to

[Configuration of the Invention] The microwave ranging device of the present invention transmits frequency-modulated microwaves from an antenna to a surface to be measured, and receives reflected waves from the surface to be measured received by a receiving antenna and the transmitted waves. A microwave that outputs frequency-modulated microwaves with a predetermined bandwidth based on a bias voltage in a distance measuring device that measures the distance to the measured surface from a beat signal obtained by mixing a part of the an output means, a temperature detection means for detecting the temperature of the microwave output means or the temperature of the microwave oscillation means in the microwave output means, and a temperature dependence characteristic of the microwave output means obtained by measurement in advance. The present invention is characterized in that it comprises a bias voltage correction means for correcting the bias so as to correct fluctuations in the frequency band 1-1 due to temperature changes from the microwave output means.

[Embodiment] FIG. 1 shows a block diagram of an embodiment of the microwave distance measuring device of the present invention.

21 is a microwave oscillator, and 22 is a modulation bias circuit, which frequency-modulates the microwave oscillator l according to the output voltage of the modulation bias circuit 22. 23 is a branching filter, which supplies the microwave from the microwave oscillator 2I to a transmitting antenna 24 and a mixing branching filter 25. 2
6 is a detection object whose distance is to be measured; 27 is an antenna that receives reflected microwaves from the transmitting antenna 24 reflected by the detection object 26; the received signal is manually transmitted to the mixing/branching filter 25; be done. In this duplexer 25, the received signal from the receiving antenna 27 and the duplexer 2
3 is mixed with the microwave from the microwave oscillator 21 via the microwave oscillator 21. 28 is a counter that counts the frequency of a single signal generated by mixing the signals, and 29 is an arithmetic processing system for processing the count value by the counter 28.

30 is a temperature detection sensor attached to the side wall of the casing of the oscillator 21 in order to detect the operating temperature of the microwave oscillator 21 described in iii. 3I is a conversion circuit that outputs the detection signal from the temperature detection sensor 30 as a voltage corresponding to the detected temperature, and 32 is a conversion circuit that converts the bias voltage of the modulation bias circuit 22 in order to temperature-correct the output voltage of the modulation bias circuit 22. This is a bias voltage calculation circuit that outputs a predetermined bias voltage corresponding to the output voltage from the conversion circuit 31.

Next, the bias voltage calculation circuit 32 will be explained in detail.

Figure 2 shows 24GI in the microwave oscillator 2■.
It shows the temperature dependence of the oscillation frequency when a 4z band Gunn oscillator is used, and it can be seen that there is a large temperature dependence of about 5 MH2/°C. From this figure, for example, temperature T=27
When scanning the FM bias voltage from V to ■2 at °C, the modulation band of the oscillator is 24.10 to 24.1
5GI-Iz and the modulation width ΔF is 50Ml-1z, but if the temperature 'r rises to 39°C,
The modulation band is F.

~F, and its bandwidth ΔF is approximately 45 MHz.

In this case, the following two methods can be used to correct the bias voltage. The first method is to maintain the modulation bandwidth ΔF at 50 M t (z) by not correcting the minimum voltage VI of the bias voltage but only the maximum voltage 2, and the second method is to , said modulation band 24.10~2
In order to maintain 4.15CI4z, both the voltages V, , V2 are changed to voltages V, , V, according to the temperature dependent characteristics,
This is a method in which not only the modulation width ΔF but also the modulation band is held constant.

Since the composer's correction method is simple, it is an effective method when the S/N ratio of the beat wave is good and mismatch does not become an error factor.On the other hand, the latter method corrects mismatch in the microwave circuit due to frequency drift. Since reflection can also be suppressed, higher accuracy can be obtained compared to the former correction method. In this invention, at least the modulation width ΔF is kept constant.

The bias voltage calculation circuit 32 stores in advance the relationship between the oscillation frequency and the temperature characteristic of the bias voltage obtained through actual measurements so that the bias voltage can be changed according to the relationship described above. A desired bias voltage is output according to stored data.

The operation of the apparatus having the above configuration will be explained below.

Based on the bias voltage from the modulation bias circuit 22,
The microwave oscillator 21 outputs microwaves with a predetermined modulation width ΔF. This microwave is transmitted from the transmitting antenna 24 to the target object 26 via the splitter 23 . The microwave reflected by the object 26 is transmitted to the receiving antenna 27.
and input to the mixer/demultiplexer 25. The microwave oscillation 3
The microwave from the two-wave oscillator 1 is inputted manually through the directional coupling 2313; Compared to the signal, the transmitting antenna 2
4 to the receiving antenna 27 after reflecting off the object 26. Therefore, a beat signal having a frequency corresponding to the path length is generated in the mixer/brancher 25, and this beat signal is counted by the counter 28, and this counter value is determined by the arithmetic processing system 29 from the transmitting antenna to the object 26. It is output as a signal representing distance.

Now, assume that the operating temperature of the microwave oscillator 21 changes due to the atmosphere and the modulation width becomes ΔF°. At this time,
The temperature change is detected by the temperature sensor 30, and a signal corresponding to the detected temperature is input from the conversion circuit 31 to the bias voltage calculation circuit 32. As a result, as described above, a predetermined bias voltage is sent from the bias voltage calculation circuit 32 to the modulation bias circuit 22 so that the modulation width is at least ΔF from the microwave oscillator 21.

As a result, the modulation width from the microwave oscillator 21 is ΔF°
Since it recovers from .DELTA.F to .DELTA.F, it is possible to eliminate measurement errors due to temperature changes in the measurement system after the duplexer 23 described above.

As mentioned above, since the method of correcting the temperature drift caused by the element in the microwave oscillator 21 is adopted, it is possible to use a semiconductor element with a relatively large temperature coefficient, such as a Gunn diode, as the oscillation element. , This makes it possible to configure the device to be small and lightweight.

In the above embodiment, the temperature of the casing of the microwave oscillator 21 was measured, but it may be built into the microwave oscillator 21 to directly measure the temperature of the microwave oscillation element.

[Effects of the Invention] As explained above, in the present invention, the modulation width from the microwave oscillation means is stabilized by temperature correction. Semiconductor elements can be used, which allows the device to be made smaller and lighter.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a microwave distance measuring device of the present invention, FIG. 2 is a diagram showing temperature dependence characteristics of bias voltage versus oscillation frequency, and FIG. 3 is a diagram showing a conventional microwave distance measuring device. It is a block diagram. 21... Microwave oscillator, 2... Modulation bias circuit, 23... Duplexer, 24... Transmission antenna, 2
5... Mixing/branching filter, 26... Target object, 27... Receiving antenna, 28... Counter, 29... Arithmetic processing system, 30... Temperature detection sensor, 31... Conversion circuit,
32...Bias voltage calculation circuit. Patent Applicant Kobe Steel Co., Ltd. Agent Patent Attorney 2 people (including the above) Figure 1 Figure 2 FM bias electric ash (V)

Claims (1)

[Claims] (1) Obtained by transmitting frequency-modulated microwaves from an antenna to the surface to be measured, and mixing the reflected wave from the surface to be measured received by the receiving antenna with a part of the transmitted wave. In a distance measuring device that measures the distance from a beat signal to the surface to be measured, the microwave output means outputs a microwave that is frequency-modulated in a predetermined bandwidth based on a bias voltage, and the temperature of the microwave output means or temperature detection means for detecting the temperature of the microwave oscillation means in the microwave output means; and a modulation band due to temperature changes from the microwave output means based on temperature dependent characteristics of the microwave output means obtained by measurement in advance. A microwave distance measuring device comprising: bias voltage correcting means for correcting the bias so as to correct width fluctuations.