JP2001318142A - Electric wave range finder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric wave range finder for temperature compensation with a simple configuration. SOLUTION: A transmission leakage signal which leaks into a reception circuit 3 instead of advancing from a transmission circuit 1 to an antenna 4 while the transmission circuit 1 is connected to the reception circuit 3 is affected by temperature change, resulting in change of position and intensity of the transmission leakage signal. A reception signal is affected by temperature change. A reference value for position or intensity of the transmission leakage signal is stored in a memory 9 in advance, which is compared with the position or intensity of actually measured transmission leakage signal. Compensation is performed based on the comparing result.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio rangefinder for measuring a distance from a target to a target by measuring a time from transmission to reception of a radio signal, and more particularly to temperature compensation thereof.

[0002]

2. Description of the Related Art Conventionally, in order to realize a radio rangefinder in which a distance measurement value is constant with respect to temperature and a signal detection ability does not change, a time difference measurement circuit whose characteristics do not change even with temperature and a transmission / reception circuit are required. It has been.

In an industrial radio range finder, for example, -20.degree.
Since an accuracy of about 1 millimeter is required in the range from to + 70 ° C., the time difference measurement circuit is required to have a stability of about 10 picoseconds. In order to make this stable time difference measurement circuit, it is necessary to select elements or the like. If the elements are not selected, the gate delay time due to the temperature of the logic IC forming the timing circuit forming the time difference measurement circuit generally changes by about 1 nanosecond due to the temperature change from 25 ° C. to 70 ° C. Therefore, the measurement distance is usually shifted by 100 mm or more.

In order to realize a transmission / reception circuit whose signal detection ability does not change within the above-mentioned temperature range, a temperature compensation circuit for keeping the gain constant is required. If there is no temperature compensation circuit, the gain of the amplifier circuit in the receiving circuit may change more than 1: 2 due to a change in temperature from 25 ° C. to 70 ° C. Even if the signal is a reflection signal from the target, The possibility of being judged as an unnecessary reflected wave increases.

[0005]

As described above, in the conventional radio range finder, in order to realize a highly accurate and stable circuit, selection of circuit elements and a complicated temperature compensation circuit are required. There is a problem that costs increase due to an increase in man-hours.

[0006] On the other hand, when the temperature compensating means is not provided, there is a problem that the measurement distance itself increases and decreases due to a change in temperature, and there is a problem that a signal detection capability is reduced due to a change in amplitude.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a radio range finder capable of performing temperature compensation with a simple configuration and capable of performing measurement without being affected by a change in temperature. Aim.

[0008]

According to one aspect of the present invention, there is provided a transmission circuit, a reception circuit, an antenna connected to a transmission circuit and a reception circuit for transmitting and receiving a radio wave, and transmitting a radio signal. A time difference measurement circuit for measuring a time from reception to reception, and a radio distance meter for measuring a distance from the time to a target, wherein the time difference measurement circuit includes a transmission leakage leaking from the transmission circuit to the reception circuit. Transmission leak signal position measuring means for determining the position of the signal, recording means for recording a position reference value of the position of the transmission leak signal leaking from the transmitting circuit to the receiving circuit, and measurement measured by the transmission leak signal position measuring means Correction means for comparing the value with a position reference value recorded in the recording means, and correcting the position of the received signal based on the result.

The invention according to claim 2 is a transmission circuit,
A reception circuit, a transmission circuit, an antenna connected to the reception circuit for transmitting and receiving radio waves, and a time difference measurement circuit for measuring a time from transmission of the radio signal to reception thereof, and a radio wave for measuring a distance from the time to a target. A distance meter, wherein the time difference measuring circuit is a transmission leakage signal strength measuring means for determining the intensity of a transmission leakage signal leaking from the transmission circuit to the receiving circuit; and the intensity of the transmission leakage signal leaking from the transmission circuit to the receiving circuit. Recording means for recording the intensity reference value of, and the measured value measured by the transmission leakage signal strength measurement means, comparing the intensity reference value recorded in the recording means,
Correction means for correcting the strength of the received signal based on the result.

[0010] Due to the coupling between the transmission circuit and the reception circuit, the transmission leakage signal leaking to the transmission circuit without going from the transmission circuit to the antenna is affected by the temperature change, and the position and intensity of the transmission leakage signal are affected. Changes. In addition, the received signal is also affected by the temperature change, but the effect of the temperature change is caused by a circuit element such as a transmission circuit, a reception circuit, or a time difference measurement circuit. . Therefore, the reference value of the position or strength of the transmission leakage signal is recorded, compared with the measured position or strength of the transmission leakage signal, and correction is performed based on the comparison result, whereby the temperature correction of the reception signal is performed. It can be carried out.

For example, with respect to the correction of the position of the received signal, the deviation of the position of the transmitted signal from the actually measured position of the transmitted signal with respect to the reference value of the position of the transmitted signal is obtained.
This can be done by shifting the position of the received signal.

Further, for example, for correction of the strength of the received signal, the ratio of the measured strength of the transmitted leak signal to the reference value of the strength of the transmitted leak signal is obtained, and the reciprocal of this ratio is calculated by the multiplication means. It can be performed by multiplying the strength. Or, determine the ratio of the measured transmission leakage signal strength to the transmission leakage signal strength reference value, and change the reception signal strength threshold for determining whether or not the reflected wave is from the target according to the ratio. This can be corrected by the following. More specifically, the correction can be made by multiplying the reference threshold value by the above ratio.

[0013] The measurement of the transmission leakage signal can be performed periodically during the measurement. The receiving circuit can have an equivalent sampling circuit, and the observation range can be arbitrarily changed by changing the sampling timing. Therefore, by setting the observation range to a range in which the transmission leakage signal can be observed, it is possible to measure the position of the transmission leakage signal by the transmission leakage signal position measuring means or measure the strength of the transmission leakage signal by the transmission leakage signal strength measuring means. it can.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 5 are views showing an embodiment of a radio rangefinder according to the present invention.

First, the configuration will be described with reference to FIG. 1. This radio rangefinder mainly includes a transmission circuit 1, a coupling circuit 2, an antenna 4, a reception circuit 3, and a time difference measurement circuit 9.
The time difference measurement circuit 9 further includes a timing circuit 5, an envelope detection circuit 6, an A / D conversion circuit 7, an arithmetic circuit 8, and a memory 19. The coupling circuit 2 is connected to the transmission circuit 1, and the coupling circuit 2 is connected to the antenna 4 and the reception circuit 3. The transmission circuit 1 receives the transmission trigger signal Tr1 from the timing circuit 5 and outputs a transmission microwave signal S1. The generated transmission microwave signal S1 is sent to the coupling circuit 2. The transmission microwave signal S1 can be, for example, a pulse wave having a center frequency of about 6 GHz, but it is obvious that a pulse signal of another frequency band can be used. The coupling circuit 2 is composed of a directional coupler, and most of the transmission microwave signal S1 from the transmission circuit 1 is sent to the antenna 4. The radio wave transmitted from the antenna 4 is reflected by the object 11 (for example, a liquid surface), received by the antenna 4, becomes a reception microwave signal S2, and is equally divided into the transmission circuit 1 and the reception circuit 3 in the coupling circuit 2. Transmitted.

The receiving circuit 3 has a sampling circuit. The receiving circuit 3 performs equivalent sampling on the received microwave signal S2 using the reception trigger signal Tr2 output from the timing circuit 5, and converts the signal into a low-frequency reception signal S3.

The reception circuit 3 is connected to an envelope detection circuit 6, and further connected to an A / D conversion circuit 7 and an arithmetic circuit 8. The low-frequency reception signal S3 is converted into an envelope detection reception signal S4 by an envelope detection circuit 6, and further converted into reception signal data D1 by an A / D conversion circuit 7. The arithmetic circuit 8 calculates the distance to the object 11 based on the received signal data D1, and finally outputs the distance to the outside as measured distance data D2. The arithmetic circuit 8 has a CP
U, and performs a temperature compensation process described later. As shown in FIG. 5, the processing functions include a comparison unit 81, a distance measurement unit 82, a threshold setting unit 83, and an observation range setting unit. And a transmission leakage signal position measuring means 85 and a transmission leakage signal strength measuring means 86 as correction means.

A memory 9 as recording means is further connected to the arithmetic circuit 8, and various data are stored in the memory 9. The observation range setting means 84 of the arithmetic circuit 8 outputs a distance setting signal S5 to the timing circuit 5 for determining where to set the observation distance range. The timing circuit 5 outputs a reception trigger signal Tr2 for determining the timing at which the reception circuit 3 performs sampling based on the distance setting signal S5.

When the transmitting microwave pulse signal S1 is output from the transmitting circuit 1, most of the signals are transmitted to the antenna 4 by the coupling circuit 2, but part of the signal is directly transmitted to the receiving circuit without going to the antenna 4. Leaks to 3. This transmission leakage waveform changes with temperature under the influence of the temperature characteristics of the circuit elements in the timing circuit 5, the receiving circuit 3, and the like.
Figure 2 is a graph showing the change, W ₀₁ in FIG. 2 (a) represents the transmission leakage waveform at the normal temperature, W ₀₂ in FIG. 2 (b) represents the transmission leakage waveform at high temperatures. The position and peak value of the transmission leakage waveform change between normal temperature and high temperature. In general, there is a tendency that the peak level of the transmission leakage waveform becomes hot reduced, the temperature change can vary under the measurement environment, transmission leakage waveform at high temperature and the peak level L ₀₁ of the transmission leakage waveform W ₀₁ at normal temperature the peak level L ₀₂ of W _02, may occur difference in about six decibels. Further, in normal temperature at a high temperature, the position P _1, the deviation P ₁₂ of P ₂ of respective transmission leakage waveform occurs. In addition, W _{r1 in} FIG.
Indicates the reception signal waveform at normal temperature, and W _{r2 in} FIG. 2B indicates the reception signal waveform at high temperature. It can be seen that the reception signal waveform also has the same tendency as the transmission leakage waveform. That is, the ratio between the peak level L _r1 of the received signal waveform at normal temperature and the peak level L _r2 of the received signal waveform at high temperature, the peak level L ₀₁ of the transmission leakage waveform W ₀₁ at normal temperature, and the transmission leakage waveform W at high temperature _{02 have} the same ratio of the peak level L ₀₂ . This is the receiving circuit 3
This is because the change in gain due to the change in temperature occurs to the same extent in both the transmission leakage waveform and the reception signal waveform. Also,
Deviation D ₁₂ between the positions of the received signal waveform at the time of the received signal waveform and a high temperature at the time of ordinary temperature, equal to the deviation P ₁₂ between the positions of the transmission leakage waveform in transmission leakage waveform and the high temperature at the time of normal temperature. This causes a position shift mainly due to a logic IC used inside the timing circuit 5.
Of the gate delay time due to temperature, because this affects both the transmission leakage waveform and the reception signal waveform to the same extent.

The memory 19 transmits data at normal temperature as a reference.
Leakage waveform W₀₁Peak level L₁And position P₁Is the reference value
Is recorded in advance. These reference values L₁And P₁
Is the transmission leakage waveform W at the time of measurement._0xPeak level L_xas well as
Position P_xIs compared to Due to this, the temperature change
The change of the gain of the receiving circuit 3 and the measurement position due to the temperature change
The deviation can be compensated. For example, send
Leakage signal position 50mm due to temperature change
If it increases only, the received signal reflected from the object
Subtract 50 mm from the distance calculated from
As a result, an accurate measurement distance can be obtained. Also, transmission omission
A reference peak for which the signal peak level has been recorded in advance.
Level L₁Compared to the received signal level by that ratio.
To compensate for the change in the received signal due to temperature changes.
A change in amplitude can be suppressed. For example, temperature changes
Reduces transmission leakage signal strength by 30%
If there is a little, (100 / (100
−30)) The arithmetic circuit 8 increases the amplitude by only
If you perform the process of expanding the amplitude of the shape, the change in amplitude due to temperature
Can be suppressed and unnecessary without lowering the signal detection capability.
It is possible not to be affected by the reflected wave. Also
Besides compensating for the signal amplitude,
The same can be said by reducing the threshold itself by 30%
Has the effect of When changing this threshold, the memory 19
Is a threshold value TH at normal temperature which is a reference in advance. ₁Is also recorded.

FIG. 3 is a flowchart showing a process for compensating for a shift in the measurement position due to a change in temperature and for compensating a threshold which is a reference for signal detection. In the arithmetic circuit 8, a measurement distance calculation including the temperature compensation processing is performed. Note that the arithmetic calculation in the arithmetic circuit 8 is performed every predetermined time, for example, about once every second. However, if it can be assumed that the temperature change is gradual, the temperature compensation processing It is considered that it is sufficient to perform the processing periodically at every large time interval. Therefore, the processing in FIG. 3 is performed about once a minute. Hereinafter, the processing of FIG. 3 will be described.

First, preparation for distance measurement is performed by the initialization processing, and a transmission leakage signal is detected (step S30).
1). At this time, the distance setting signal S5 is set to perform equivalent sampling on the signal immediately after transmission.
Then, the transmission leakage signal position measuring means 85 and the transmission leakage signal strength measuring means 86 determine the position Px of the transmission leakage signal.
And the peak level Lx are obtained (step S302).
Further, the threshold value setting means 83, using the threshold TH ₁ of these obtained peak level Lx, base peak level L ₁ and the reference of the threshold THx for determining the presence or absence of the object 11 obtained by the following formula (Step S30
3).

[0023]

(Equation 1) Here, the reference peak level L ₁ of the transmission leak signal is
The reference threshold value TH ₁ is set before shipment from the factory and is stored in the memory 9 in advance.

Next, the head of the observation range is set to the minimum range of the distance measurement range by the observation range setting means 84 (step S).
304), and acquire received signal data (step S30).
5). For example, when using this radio rangefinder to measure the level of liquid in a tank, the minimum distance of the distance measurement range is the distance to the highest liquid level inside the tank, and the maximum distance of the distance measurement range is the bottom of the tank. To the distance. These minimum distance and maximum distance are set after the radio rangefinder is installed, and are stored in the memory 9. When equivalent sampling is performed, the observation range is the sweep time of the delay time, but the leading position of the sweep of the delay time can be easily set digitally for the delay sweep circuit in the timing circuit 5. For example, if the width of the observation range is fixed at 1 meter, the sweep width is set to a fixed value of about 6.67 nanoseconds, and the start of the sweep range is set to match the start of the observation range. For example, when the observation range is from 3.5 meters to 4.5 meters, the sweep range of the delay time of the delay sweep circuit is from 23.35 nanoseconds to 30.02 nanoseconds. However, since the signal propagation time actually exists inside the circuit, it is preferable that the value be increased or decreased by the delay time due to the signal propagation time or the like during the above period.

With respect to the received signal data obtained in step S305, it is determined whether there is a level exceeding the threshold value THx using the threshold value THx obtained in step S303 (step S306). In, distance calculation is performed on the received signal obtained therefrom (step S309). If there is no level exceeding the threshold level, it is checked whether or not the current observation range is the maximum distance of the measurement distance range (step S307). If not, the observation range is set to 0.5 m behind (step S307). S308), returning to step S305 to acquire the received signal data, and from step S305 to step S305.
Repeat 308. If the current observation range is the maximum distance of the measurement distance range, the observation range is set to the minimum distance of the distance measurement range (step S304), and step S304 is performed.
To 308 are repeated. Normally, an object such as a liquid surface can be detected before the observation range reaches the maximum distance of the measurement distance range, so that it is possible to avoid repeating these steps indefinitely and proceed to step S309.

Next, it is checked whether or not the measurement distance obtained in step S309 exists in the front of the observation range (step S310). If the measurement distance exists in the front, the head of the observation range is set in the front. It is shifted (step S311). If the obtained distance range does not exist earlier in the observation range, it is checked whether it exists later (step S31).
2) If it exists at the rear, the head of the observation range is shifted backward (step S313). By these processes,
It is set so that the received signal always comes near the center of the observation range.

Next, the measurement distance obtained in step S309, the corrected difference between the reference position P ₁ position Px and the transmission leakage signal of a transmission leakage signal, and correct the measured distance of this. That is, the measurement distance obtained in step S309 is Dx,
Assuming that the correct measurement distance is D'x, correction is performed by the following equation.

[0028]

D′ x = Dx− (Px−P ₁ ) For example, if the position of the transmission leakage signal is −0.2 meters and the reference position of the transmission leakage signal is −0.3 meters, This means that there is a factor that deviates by −0.1 meter from the measured value at the factory, and the measured distance obtained in step S309 is a value that is 0.1 meter larger than the accurate value. If the distance obtained in step S309 is reduced by 0.1 meters, a more accurate measurement value can be obtained.

Next, it is checked whether one minute has elapsed since the observation of the transmission leakage signal (step S315), and if it has elapsed, the position Px and the peak level Lx of the transmission leakage signal are obtained again (step S315). S316), updating from the past value. Furthermore, the peak level Lx obtained in step S316, by using the threshold value TH ₁ peak level L ₁ and the reference of the reference of the transmission leakage signal, the threshold THx for determining the presence or absence of object 11 in equation (1) (Step S317).

When the process in step S317 is completed, the observation range is returned to the range before observing the transmission leakage signal in step S316 (step S318), and the object 11 can be observed again. In the determination processing of step S315, if one minute or more has not elapsed, and step S315
After the observation position is returned to the original position by 318, reception signal data in the observation range is obtained (step S319). From the data obtained in step S319, it is determined whether there is a level exceeding the threshold in the observation range (step S32).
0), if there is a level higher than the target, it is determined that the target object exists within the observation range, and the distance calculation is performed again in step S309. If there is no level exceeding the threshold value in the determination processing in step S320, the head of the observation range is set again to the minimum distance in the measurement distance range in step S304, and the subsequent processing is repeated.

FIG. 4 is a timing chart of the observation range by the processing of FIG. The vertical axis represents the observation range, in other words, the delay time, that is, the time from the transmission trigger signal Tr1 to the output of the reception trigger signal Tr2.

As described above, in the processing of FIG. 3, the detection of the object (steps S304 to S308)
When the presence or absence of an object is determined (step S30)
In step 303, the correction of the threshold value of 6) is performed according to the ratio between the reference value of the transmission leakage signal and the amplitude of the actually measured transmission leakage signal, so that the presence or absence of the target can be determined stably. . In addition, even if the target is lost due to a sudden change in the position of the target after the detection of the target, it is determined whether the target exists in the observation range (step S320). It can be performed reliably. In this case, the transmission leakage signal is periodically observed at a predetermined time interval (for example, once a minute) (steps S315 to S318).
The threshold can be made to follow a change in the characteristics of the receiving circuit due to a change in temperature. Furthermore, the distance obtained from the received signal data of the obtained observation range is corrected to a more accurate value by the difference between the reference value of the position of the transmission leak signal and the position of the transmission leak signal, and as a result, the distance accuracy is high. A radio range finder can be realized.

Further, even when the object is a liquid surface or the measurement environment is in a liquid and the antenna 4 is buried in the liquid, the temperature can be corrected because the transmission leakage signal exists.

[0034]

As described above, according to the present invention,
In order to perform temperature compensation based on the temperature change of the transmission leakage signal leaking from the transmission circuit to the reception circuit, there is no need to pay special attention to the selection of circuit elements, and to eliminate the need for complicated temperature compensation circuits. Temperature compensation can be performed with a simple configuration, and stable measurement not affected by a change in temperature can be performed. In particular, according to the first aspect of the present invention, the deviation of the distance measurement value hardly occurs, and according to the second aspect of the present invention, the signal can be detected stably.

Further, a change in a circuit element due to another factor other than temperature, such as a change with time, can be similarly compensated.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a radio rangefinder of the present invention.

FIG. 2 is a waveform diagram showing a relationship between a transmission leakage signal and a reception signal at (a) normal temperature and (b) high temperature.

FIG. 3 is a flowchart illustrating a measurement distance calculation process including a temperature compensation process of the radio range finder of the present invention.

FIG. 4 is a time chart of a sampling delay time.

FIG. 5 is a functional block diagram of an arithmetic circuit.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 transmission circuit 3 reception circuit 4 antenna 85 transmission leak signal position measuring means (correction means) 86 transmission leak signal strength measuring means (correction means) 9 time difference measurement circuit

Claims (2)

[Claims] A transmitting circuit, a receiving circuit, an antenna connected to the transmitting circuit and the receiving circuit for transmitting and receiving a radio wave, and a time difference measuring circuit for measuring a time from transmitting a radio signal to receiving the radio signal. A radio rangefinder that measures a distance to a target, wherein the time difference measurement circuit includes: a transmission leakage signal position measuring unit that determines a position of a transmission leakage signal leaking from the transmission circuit to the reception circuit; and the reception from the transmission circuit. Recording means for recording a position reference value of the position of the transmission leakage signal leaking to the circuit, and a measurement value measured by the transmission leakage signal position measurement means, comparing the position reference value recorded in the recording means, A radio range finder comprising: a correction unit that corrects a position of a received signal based on a result. 2. A transmitting circuit, a receiving circuit, an antenna connected to the transmitting circuit and the receiving circuit for transmitting and receiving a radio wave, and a time difference measuring circuit for measuring a time from transmitting a radio signal to receiving the radio signal. A radio rangefinder that measures a distance to a target, wherein the time difference measurement circuit includes: a transmission leakage signal strength measuring unit that determines the intensity of a transmission leakage signal leaking from the transmission circuit to the reception circuit; and the reception from the transmission circuit. Recording means for recording an intensity reference value of the intensity of the transmission leakage signal leaking to the circuit, and a measurement value measured by the transmission leakage signal intensity measurement means, and comparing the intensity reference value recorded in the recording means, A correction unit for correcting the strength of the received signal based on the result.