JPS6355033B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention is a method of determining the straight-line distance between two points by measuring the propagation time in space using radio waves, light, etc., in which a transmitter is installed at each of two points. The present invention also relates to a one-way distance measuring device that measures the propagation time in one direction from a transmitter to a receiver using a set of receivers, and measures the distance between two points.

The principle of the one-way distance measuring device will be explained with reference to a block diagram for explaining the principle in FIG. 1 and a waveform diagram of main parts in FIG.

In FIG. 1, when determining the distance between two points A and B, it is assumed that a transmitter 1 and a receiver 4 for distance measurement are placed on the A point side and the B point side, respectively. and,
A reference signal 8 shown in FIG. 2a obtained from a reference signal source 5 is transmitted from the transmitting antenna 2 at point A via the transmitter 1. On the other hand, the reception antenna 3 at point B receives the reception signal 9 shown in FIG. . This received signal 9 is applied to the time measuring device 6 via the receiver 4, but the reference signal 8 is also applied to the time measuring device 6 at the same time, and the delay time t is determined by comparing both signals 8 and 9. (seconds) is measured. This delay time t (seconds) is converted by the time-distance converter 7 according to equation (1), and the distance between the two points A and B is determined. In other words, the distance l (m) between two points A and B is the speed of light c
(m/sec), it can be obtained using the following equation (1).

l=c×t(m)...(1) However, with the one-way distance measurement method, the distance to be measured is usually a long distance, or when one or both of the transmitting and receiving sides are located on an aircraft, ship, etc. In many cases, the reference signal 8 is a moving body, and therefore, it is often impossible to supply the same reference signal 8 to the transmitting side and the receiving side at the same time as shown in FIG. Therefore, if you try to configure a one-way distance measuring device in such a case,
It is necessary to provide reference signal sources whose frequencies and phases match each other on both the transmitting side and the receiving side, and to create a circuit configuration equivalent to that shown in FIG. 1.

However, in order to obtain high measurement accuracy with this method,
It is necessary to use two sets of reference signal sources with high frequency stability and match the frequencies and phases of both with high accuracy before starting distance measurement. For this reason, such a reference signal source is usually an oscillator controlled by a cesium atomic beam (hereinafter referred to as a cesium oscillator) used as a primary frequency standard, or a rubidium gas cell used as a secondary frequency standard. An oscillator with high frequency stability and absolute frequency accuracy, such as an oscillator controlled by a rubidium oscillator (hereinafter referred to as a rubidium oscillator), is used.

By the way, conventionally, when the transmitting side and the receiving side each have separate reference signal sources as described above, and it is desired to accurately match the frequency and phase of the two, it is necessary to measure the frequency difference and phase difference between the two. Therefore, methods such as finely adjusting one of the frequencies and phases according to the values are taken, but making the frequency difference and the phase difference extremely small requires special equipment and a huge amount of adjustment work time. Moreover, this is an indispensable task for determining the distance measurement accuracy of the unidirectional distance measurement method, and cannot be omitted.

This invention was made in view of the above-mentioned points. Before starting distance measurement, the transmitting side and the receiving side are respectively installed at two points whose distances are known in advance, and the above two reference signals are transmitted in a stationary state. Find the difference between the measured distance and the actual distance caused by the change in measured distance over time caused by the source frequency difference and the phase difference, and correct the measured distance according to this value to increase the true distance. This is a one-way distance measuring device that allows accurate measurement and eliminates the need for adjusting the frequency difference and phase difference as described above. Hereinafter, the present invention will be explained in detail based on the drawings.

FIG. 3 is a block diagram showing the configuration of one embodiment of the present invention.

In FIG. 3, the transmitting side consists of a receiver 11, a rubidium oscillator 12 and a transmitting antenna 13, and the receiving side consists of a receiving antenna 14 and a receiver 1.
5, a time measuring device 16, a time-distance converter 17, a distance display 18, a rubidium oscillator 19, and a distance corrector 20.

Next, the operation of the embodiment shown in FIG. 3 will be explained.

If the frequencies and phases of the rubidium oscillator 12 and the rubidium oscillator 19, which are the reference signal sources on the transmitting side and the receiving side, match completely,
The circuit configuration is equivalent to the principle diagram of the one-way distance measuring device shown in FIG. 1, and its operation is as described above, and the time-distance converter 17 determines the linear distance between A and B. However, normally the frequencies and phases of the two rubidium oscillators 12 and 19 do not match, so in this state A-B
It is not possible to find the distance between.

Therefore, a method is required to compensate for the distance measurement error caused by the frequency difference and phase difference between the rubidium oscillators 12 and 19 on the transmitting and receiving sides. below,
The correction method will be explained.

FIG. 4 is a waveform diagram of the main part of the embodiment shown in FIG. 3 when there is the above-mentioned frequency difference and phase difference, and FIG. 5 is an explanatory diagram of distance measurement in that case.

The signal 31 in FIG. 4a is a transmission signal obtained by the rubidium oscillator 12 on the transmission side, and has a frequency f ₁₂ (Hz),
A sine wave with a period t ₁₂ =1/f ₁₂ (seconds) is assumed. The signal 34 in c in the same figure has a propagation time t corresponding to the propagation path of the signal 31.
(seconds) delayed received signal. The signal 32 in b is a reference signal generated by the rubidium oscillator 19 on the receiving side, and compared to the signal 31 at the zero crossing point of the signal, there is a time delay (phase delay) t _d (seconds) in the initial state.
, and the frequency f ₁₉ (Hz) is slightly higher,
It is assumed that the period t ₁₉ (seconds) is a sine wave whose period is expressed as t ₁₉ =(1/f ₁₂ )−Δt (seconds). In addition, signal 33 in figure b
indicates a sine wave whose frequency is equal to that of the signal 31 and delayed by t _d (seconds) at the same time as the signal 32 in the initial state.

In the one-way distance measuring device described above, even when both the transmitting and receiving sides are stationary and there is no change in the distance between them, the time measured by the time measuring device 16 in FIG.
As time passes, t ₀ (seconds), t ₁ = t ₀ + Δt (seconds), t ₂
=t ₀ +2Δt (seconds)... and the corresponding measurement distance increases. The state of this distance change is as shown by the straight line 41 in FIG.
Assuming that is stable and there is no change in frequency, the transmission,
Regardless of whether the receiver is moving or stationary,
The measurement error due to the frequency difference increases with a constant slope K over time. This constant slope K can be obtained from equation (2) by measuring the increase in measured distance L ₀ (m) at time T ₀ (seconds) in FIG. 5 while the transmitting and receiving sides are stationary.

K=L ₀ /T ₀ ...(2) In Fig. 5, the curve 42 shows the change in the actual distance (actual distance) between the sending and receiving sides, and the time T ₁ (seconds) from the initial state 0. The signal remains stationary at a distance S ₀ (m) up to the point S 0 (m), and then the transmitting side, the receiving side, or both move and the distance changes as shown by a curve 42. Curve 43 shows the change in measured distance using the device of this embodiment at this time, and
Even though the transmitting and receiving sides are stationary up to T ₁ (seconds), due to the measurement error based on the frequency difference mentioned above, the measurement is made at a constant slope from the initial value S ₀ ′ (m) as shown in straight line 41. This indicates that the distance increases and after T ₁ (seconds) has elapsed, the distance shown by the curve 43 is measured by the time-distance converter 17 in FIG. Here, the actual distance S ₀ (m) and the measured distance in the initial state
There is a relationship between S ₀ '(m) and Equation (3), which represents a measurement error caused by the phase difference between the signals 31 and 32 shown in FIG. 4 in their initial states.

S ₀ −S ₀ ′=t _d ×c (m) ...(3) Also, the measured distance S ₁ at the elapsed time T ₁ (seconds)
(m) and the actual distance S ₀ (m) have the relationship shown in equation (4).

S ₀ −S ₁ =L ₁ =t _d ×c−K×T ₁ (m) ……(4) In equation (4), the elapsed time from the initial state 0 is T ₁ (seconds)
The measurement error in includes a measurement error t _d ×c (m) due to the above-mentioned phase difference in the initial state and a measurement error K×T ₁ (m) due to the frequency difference.

Therefore, by determining the measurement error based on the phase difference at the start of measurement and the measurement error based on the frequency difference with respect to the elapsed time, and correcting the measured distance using these values, the actual distance can be determined with high accuracy.

The state of distance measurement at this time will be explained with reference to FIGS. 3 and 5.

As mentioned above, in order to obtain the measurement error based on the frequency difference, time is calculated from the initial state 0 in a stationary state.
The amount of increase L ₀ (m) in the measured distance up to T ₀ (seconds) is measured by the time-distance converter 17, and a constant slope K of increase is determined according to equation (2) and stored in the distance corrector 20. let On the other hand, T ₁ from the distance measurement starting point and the initial state
(seconds) has elapsed, the measurement error L ₁ (m) at this point based on the above phase difference is the distance S ₀ between the transmitting and receiving points determined in advance according to equation (4).
(m) and the distance measured by the time-distance converter 17
Since it is determined by the difference between S ₁ (m), this value L ₁ (m)
is stored in the distance corrector 20. Next, assuming that there is a change in distance between transmission and reception as shown by curve 42 from the starting point of distance measurement at _T1 , time-distance converter 1
7 shows a change in the curve 43 including measurement errors based on the frequency difference and phase difference described above. Therefore, the actual distance at the point (T - T ₁ ) (seconds) elapsed from the distance measurement starting point T ₁
M ₀ (m) is the measured distance M ₁ (m) above.
It is obtained by adding L ₁ (m) and further subtracting the measurement error L(m) shown in equation (5) based on the frequency difference, and the relationship in equation (6) is established.

L=K×(T- _T1 )(m)...(5) _M0 = _M1 + _L1 -L= _M1 +( _S0 - _S1 )-{K×(T-
T ₁ )} ...(6) The above distance correction function is performed according to L ₁ (m) and K stored in the distance corrector 20, and L (m) obtained by calculating equation (5). , L ₁ (m), L on the distance display 18 to the measured distance of the time-distance converter 17
This is done by adding and subtracting (m).
In FIG. 5, a curve 44 is a case where the actual distance curve 42 includes a measurement error based on the frequency difference,
A curve 45 shows the distance indicator 18 when the measured distance is corrected for the measurement error based on the phase difference and the measurement error based on the frequency difference is corrected at time intervals of ΔT (seconds).
It shows that the shorter ΔT (seconds) is, the closer the curve 45 is to the curve 42 that shows the change in actual distance.

In addition, the period t ₁₂ (seconds) of the above signal 31 and Δt,
The relationship of equation (7) holds between k, T ₀ , L ₀ , etc.

K=(Δt/ _t12 )×c= _L0 / _T0 =L/(T- _T1 )
...(7) Here, Δt/t ₁₂ is the frequency f ₁₂ (Hz) and f ₁₉
(Hz), and it is relatively easy to set Δt/t ₁₂ < 10 ^-10 even when using an ordinary rubidium oscillator, which means that even if there is a difference between the two frequencies, This shows that the difference can be made very small.

In addition, in the above embodiment, when explaining the frequency difference and phase difference correction function, the case where the frequency of the signal from the rubidium oscillator 19 is higher than the signal from the rubidium oscillator 12 or the signal from the rubidium oscillator 19 is delayed is explained. Correction can be made in the same manner as above even when the frequency is low or the phase is advanced.

As explained in detail above, the one-way ranging device according to the present invention includes highly stable signal sources with high frequency stability on the transmitting side and the receiving side, and uses the highly stable signal source on the transmitting side for distance measurement. A highly stable signal provided on the transmitting side and the receiving side, which serves as a reference signal source for creating a reference signal, and on the other hand, as a reference signal for measuring the propagation delay time of the ranging reference signal of the highly stable signal source on the receiving side. The measurement error due to the mutual frequency difference and phase difference between the sources was measured in advance, and the rate of change in the measured distance with respect to time caused by the frequency difference when the transmitting and receiving sides were stationary, and the transmitting side caused by the phase difference. Since we have provided a means of correction based on the difference between the actual distance on the receiving side and the measured distance,
Even if the relative distance between the sender and receiver changes,
This has an extremely excellent effect in that highly accurate distance measurement can always be performed using a reference signal with high frequency stability.

[Brief explanation of drawings]

Fig. 1 is a block diagram for explaining the principle of a one-way distance measuring device, Fig. 2 is a waveform diagram of the main part for explaining the operation of Fig. 1, and Fig. 3 is an embodiment of the present invention. FIG. 4 is a waveform diagram of the main part for explaining the operation of the embodiment of FIG. 3, and FIG. 5 is a functional explanatory diagram of distance measurement and distance correction of the embodiment of FIG. 3. . In the figure, 11 is a transmitter, 12 and 19 are rubidium oscillators, 13 is a transmitting antenna, 14 is a receiving antenna, 15 is a receiver, 16 is a time measuring device, 17 is a time-distance converter, 18 is a distance indicator, 20 is a distance corrector.

Claims (1)

[Claims] 1. In a one-way distance measuring device that sends a signal from a transmitting side to a receiving side and measures the distance between the transmitting side and the receiving side based on the time that the signal is transmitted between the two, A highly stable signal source with high frequency stability is provided, the highly stable signal source on the transmitting side is used as a reference signal source for creating a reference signal for distance measurement, and the highly stable signal source on the receiving side is used as the reference signal for distance measurement. As a reference signal source for measuring the propagation delay time of and means for correcting based on the rate of change of the measured distance with respect to time caused by the frequency difference in the state of Unidirectional distance measuring device.