JPS6030905B2 - Radio distance measurement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a radio wave distance measurement method that measures the distance between two points using the propagation delay time of radio waves.

Conventionally, in distance measurement methods using pulse-modulated radio waves (hereinafter simply referred to as pulse methods), measurement accuracy has been limited by the technique of creating narrow pulses.

For example, when a pulse with a time width of lrs is used, the distance resolution is only about 150 degrees. Further, in order to create a narrow pulse exceeding a certain limit, the device becomes complicated and expensive, which is uneconomical. Furthermore, in order to transmit narrow pulses, it is necessary to widen the occupied frequency bandwidth of radio waves, which is disadvantageous in terms of radio wave usage efficiency. Although the pulse method has the advantage of a relatively simple system, it has not been used for highly accurate distance measurement due to the drawbacks mentioned above. In order to improve these shortcomings, a radio distance measurement method has been proposed in which the distance between two points is measured by sending a pulse-modulated radio wave back and forth n times between the two points. There is.

According to such a radio wave distance measurement method, the distance measurement resolution A is A/n, which has the advantage that the error is multiplied by a factor of n.

However, according to this method, distance measurement accuracy can be improved by increasing the number of round trips n of radio waves without significantly reducing the pulse time width, and the configuration of the device is simple and inexpensive. There are advantages. However, in the case of this method, the delay characteristics change economically within the device, and as the delay characteristics change, the delay time of the signal inside the device changes over time, and this is multiplied by n, resulting in a measurement error. is added to the measured value, making the measured data unreliable and not in practical use.

The reason why the delay time characteristics inside the device change over time is because the transmission frequency and reception local oscillation frequency fluctuate, and the delay time of elements inside the device changes due to changes in environmental conditions. SUMMARY OF THE INVENTION An object of the present invention is to provide a radio wave distance measurement method that can correct changes in signal delay characteristics inside the device, which measures distance by making radio waves go back and forth n times.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

First, the measurement principle of the present invention will be explained using FIG. Pulse modulated radio waves generated by a transceiver X are emitted from a transmitting/receiving antenna Y toward a destination whose distance is to be measured. This radio wave is reflected by a reflecting antenna Z placed at the destination, returns to a transmitting/receiving antenna Y, and is received by a transmitting/receiving device X. A radio wave modulated again with the pulse signal detected by this reception is sent out from the antenna Y. When the pulse modulated radio waves are made to travel back and forth n times between antennas Y and Z in this way, the time required for the radio waves to make one round trip between two points is
The total delay time T of the pulse signal due to n round trips is given by the formula '1}. T=nt,
......'1' Now, when modulating a high frequency with a pulse, if a noise voltage component is mixed into the modulation circuit, the rising part of the pulse in the modulation waveform may be shifted forward or backward in time.

This temporal variation is commonly called time jitter, and causes errors in distance measurement using the pulse method. 1
If the time jitter caused by the number of pulses sent is tj, then
The total time jitter Tj caused by sending pulses for n round trips between two points is given by the equation '2'.

Ti=nonti……[2}
The reason why the weight of multiple time jitters is the geometric mean is that the phase of the noise voltage component is random.
As is clear from the formula {l}, '2), the measurement radio waves are 2
By going back and forth between points n times, the propagation delay time increases by n times, but the measurement error only increases by n times. This means that
Although the increase in measurement error is relatively low, it means that the accuracy of propagation delay time measurement, in other words, the resolution of distance measurement, is greatly improved. That is, if the measurement resolution when the radio wave goes back and forth once is A, then when the radio wave goes back and forth n times, the resolution becomes 0 and the error increases by a factor of n. Then, when the propagation speed of the radio wave is Vc, the distance L between two points is given by the formula '3}. L = Cow skin... [3I When measuring the distance L between two points in this way, the delay time of the signal that changes over time inside the device is multiplied by n when the radio waves go back and forth n times, resulting in an error. becomes large, so the high-frequency signal is circulated separately n times inside the device, and the delay time d of the signal inside the rhombus when the high-frequency signal is circulated n times is determined, and the value is calculated from formula '3' as shown in formula ■. Correct distance L between two points by subtracting
′.

L'=(T.Vc-Td)/...[4' or more is the measurement principle of the present invention.

Hereinafter, specific embodiments of the present invention will be explained in detail with reference to the block diagram shown in FIG.

As shown, the output of a clock oscillator 1, which generates a time signal, is applied to a sequence control circuit 2. This sequence control circuit is a circuit that issues command signals according to a predetermined time program and controls all measurement operations in this measuring device. The pulse generating circuit 3 receiving the signal from the sequence control circuit 2 is controlled by this signal to generate a single pulse of a predetermined width, and drives the pulse modulator 5 via the switch 4. The output of this modulator 5 is applied to a high frequency oscillator 6 consisting of a magnetron, which generates a pulse modulated high frequency signal. This high frequency signal is applied to an antenna 9 via a directional coupler 7 and a transmitting/receiving separator 8, and is emitted from this antenna as a radio wave toward a target antenna 10 located at a distance measurement point.
On the other hand, a part of the output of the switch 4 is returned to the sequence control circuit 2, and this circuit generates a start pulse.

This start pulse is applied to the switch 20 and the switch 21, the switch 20 closes, and the switch 21 turns the counter 22 UP.
Touch the input end. This UP input terminal is an input terminal for causing the counter 22 to perform an addition operation. The output of the clock oscillator 1 is applied to one end of the switch 20, and the counter 22 starts counting clock pulses via the switch 20 and the switch 21. The radio waves reaching the antenna 10 are reflected by the reflector and sent back toward the antenna 9.

The high frequency signal generated at the antenna 9 by receiving this radio wave is
The signal is separated by a transmitting/receiving separator 8, passes through a divider 11, is mixed and amplified together with a signal from a frequency converting local oscillator 13 by a frequency converting amplifier 12, is converted to an intermediate frequency, and is sent to an intermediate frequency amplifier 14. The intermediate frequency amplifier 14 is controlled by a temporal sensitivity control circuit 15 so that its gain varies temporally. This is done to remove unnecessary reflected signal components from a short distance, and gates the intermediate frequency amplifier 14 with a delayed pulse corresponding to a preset distance.
It is designed not to pass any signal other than the target pulse modulation signal for measurement. The target pulse signal is amplified by an intermediate frequency amplifier 14, then detected by a detector 16 and converted into a video pulse, and fixed delay circuit 17 for preventing a decrease in accuracy during short distance measurement.
is returned to the switching device 4 through the At this point, switch 4
is controlled by the command signal from the sequence control circuit 2,
Since the signal from the delay circuit 17 is passed to the output side, the video pulse sent from the delay circuit 17 is applied to the pulse modulator 5. As a result, the high frequency oscillator 6 again generates a high frequency signal modulated by this pulse. This high frequency signal is transmitted from the antenna 9 to the antenna 1 as described above.
It is fired towards the river. After repeating the above operation n times, the switch 20 opens according to a command from the sequence control circuit 2, the counter 22 stops counting, and the switch 21 switches to the DOWN input terminal for the subtraction operation of the counter 22. The switch 4 is connected to the pulse generation circuit 3 side, and the switch 1 is connected to the pulse generation circuit 3 side.
1 are respectively switched to the directional coupler 7 side. The above operation is the first stage of the distance measurement operation. Next, a single pulse is generated again from the pulse generating circuit 3 according to a command from the sequence control circuit 2, the switch 20 is closed by the start pulse, and the counter 22 starts counting.

In this case, since the converter 21 is connected to the DOWN input terminal, the counter 22 operates to subtract from the count number in the first stage. Furthermore, since the switch 11 is connected to the directional coupler 7 side, the high frequency signal from the directional coupler 7 is locally fed back into the frequency conversion amplifier 12 . As a result, the pulse signal appearing on the output side of the fixed delay circuit 17 is delayed by the internal delay time of the measuring device. After repeating the above operation for n lines in the same way as in the first stage, the counting operation is stopped by a command from the sequence control circuit 2. As a result, the counter 22 displays on the digital display 23 a value equivalent to the radio wave delay time, which is obtained by subtracting the internal delay time from the measured delay time of the first stage. This display value is applied to the above-mentioned formula {311 times T, and the distance L between the two points is determined from the formula '3}. In addition, 18 is a cathode ray tube monitor, 1
Reference numeral 9 denotes a frequency divider circuit which is controlled by the clock oscillator 1 and provides this monitor external indicator, and these monitor circuits are used for observing the operating conditions of the temporal sensitivity control circuit 15 during initial setting and for monitoring the operation of the measuring device. It will be done.

In this embodiment, the measurement operation at each stage is sequence-controlled according to a predetermined time program as described above, so distance measurement operations performed by sending radio waves back and forth multiple times between two points can be performed reliably and easily. be able to. As described above, the present invention transmits radio waves based on pulse-modulated high-frequency signals n times (n is an integer of 2 or more) between two points whose distance is to be measured.
The total propagation delay time of the radio wave is measured including the signal delay time of the measuring device itself, and n times the signal delay time of the measuring device itself is also measured separately, and based on the difference between these measured values, Since the distance between two points is measured using the same method, it is possible to correct changes in the delay characteristics of the signal that change over time within the device, and the accuracy of distance measurement can be greatly improved.

Furthermore, this method has the advantage that the device configuration is simpler and less expensive than a method that aims to improve measurement accuracy by reducing the time width of the pulse.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the measurement principle of the invention, and FIG. 2 is a block diagram showing an embodiment of the measurement method of the invention. 1...Clock oscillator, 2...Sequence control circuit, 3...Pulse generation circuit, 5...
...Pulse modulator, 6...High frequency oscillator, 7.
... Directional coupler, 8 ... Transmission/reception separator, 9, 10 ... Antenna, 12 ... Frequency conversion amplifier, 14 ... ... Intermediate frequency amplifier, 15
...Temporal sensitivity control circuit, 16...Detector, 17...Fixed delay circuit, 22...Counter, 23...Digital display . Tanokanta Z diagram

Claims (1)

[Claims] 1 In a radio distance measurement method that measures the distance between two points based on the propagation delay time of radio waves caused by a high-frequency signal modulated by pulses, the radio waves are transmitted n times (n times) between the two points whose distance is to be measured.
is an integer of 2 or more).
step measurement and a second step measurement in which the high-frequency signal is directly circulated within the measurement device n times to measure the internal signal delay time of the measurement device, and the measured value at the first step measurement is performed. Based on the difference between
A radio distance measurement method that measures the distance between points.