JPS5988670A - Apparatus for measuring unidirectional distance - Google Patents

Abstract

PURPOSE:To calculate a real distance with high accuracy, by a method wherein the change to the time of a distance to be measured generated by the frequency difference of two reference signal sources in a stationary state and the difference of the distance to be measured and an actual distance generated by phase difference are calculated and the distance measured corresponding to the calculated value is corrected. CONSTITUTION:The increment amount L0(m) of a distance to be measured until a time T0(sec) is elapsed from an initial state 0 is measured in a stationary state by a time- distance converter and the constant gradient K=L0/T0 of the increment is calculated to be stored in a distance correction device. The measuring error L1(m) based on the phase difference of a distance measurement start point and a point where T1(sec) is elapsed from the initial state is calculated as the difference of the distance S0(m) between a transmission point and a receiving point and the distance S1(m) measured by the time-distance converter to be stored in the distance correction device. The actual distance M0(m) at the point where (T-T1)(sec) is elapsed from the distance measurement start point T1 is obtained by a method wherein the above mentioned L1(m) is added to the measured distance M1(m) at that time and the measuring error L(m) based on the above mentioned frequency difference is further subtracted from the sum value.

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. 2.

In Figure 1, when finding the distance between two points A and B, A
It is assumed that a transmitter 1 and a receiver 4 for distance measurement are placed on the point side and the point B side, respectively. A reference signal 8 shown in FIG. 2(a) obtained from a reference signal source 5 is transmitted from the transmitting antenna 2 at point A via a transmitter l. on the other hand,
The receiving antenna 3 at point B receives the received signal 9 shown in FIG. 2(b), which is the signal radiated by the transmitting antenna 2 delayed by the propagation time in space between the two points A and B. . 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 (seconds) is determined by comparing both signals 8.9. ) 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. That is, the distance RfL between two points A-B
If (m) is the speed of light c (m7 seconds), then the following (
1) Formula % Formula % (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 transmitter and receiver is a moving object such as an aircraft or a ship. In many cases,
For this reason, it is often impossible to simultaneously supply the same reference signal 8 to the transmitting side and the receiving side as shown in FIG. Therefore, when attempting to configure a one-way distance measuring device in such a case, a reference signal source with the same frequency and phase is provided on both the transmitting side and the receiving side, and a circuit configuration equivalent to that shown in Fig. 1 is created. There is a need.

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 to match the frequencies and phases of both sources with high accuracy before starting distance measurement. For this reason, such reference signal sources usually include an oscillator controlled by a cesium atomic beam (hereinafter referred to as a cesium oscillator) used as a primary frequency standard, or controlled by a rubidium gas cell used as a secondary frequency standard. An oscillator with high frequency stability and absolute frequency accuracy, such as 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 adjusting one frequency and phase by v1M1M according to the values are taken, but making the frequency difference and phase difference extremely small requires special equipment and a huge amount of adjustment work time. Moreover, this is an essential task in 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 frequency difference between the sources and the phase difference, and correct the measured distance according to this value to find the true distance with high accuracy. This is a one-way distance measuring device that 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 an embodiment of the present invention.

In FIG. 3, the sending side sends #! 11, a rubidium oscillator 12 and a transmitting antenna 13, and a receiving antenna 14 on the receiving side. Receiver 15, time measuring device 16
．． Time-distance converter 17° distance indicator 18. It is composed of 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, are completely matched, a circuit equivalent to the principle diagram of the one-way ranging device shown in Fig. 1 is created. The operation is as described above, and the time-distance converter 17
The straight line distance between -B is determined. However, since the frequencies and phases of the two rubidium oscillators 12 and 19 do not normally match, it is not possible to determine the distance between A and B in this state.

Therefore, the transmitter and receiver rubidium oscillators 1
A method of correcting distance measurement errors due to the frequency difference and phase difference of 2.19 is required. The correction method will be explained below.

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. 4(a) is the rubidium oscillator 1 on the transmitting side.
2 is a sine wave with a frequency f12 (Hz) and a period t+ 2 =1/fl 2 (seconds).

A signal 34 in FIG. 3(c) is a received signal obtained by delaying the signal 31 by a propagation time t (seconds) corresponding to the propagation path. Signal 32 in (b)
is a reference signal generated by the rubidium oscillator 19 on the receiving side, which has a time delay (phase delay) td, (seconds) in the initial state compared to the signal 31 at the zero crossing point of the signal, and has a frequency f+9 (H2). is slightly higher, and its period t19 (seconds) is t+9=(1/f+2)−Δ
Let it be a sine wave expressed in t (seconds). Also, the same figure (b)
The signal 33 has the same time td (seconds) as the signal 32 in the initial state.
A delayed sine wave whose frequency is equal to signal 31 is shown.

In the one-way distance measuring device described above, both the sending and receiving sides are stationary, and even if there is no change in the distance between them, the time measured by the time measuring device 16 in FIG. 3 changes over time. Tet
o (seconds), t+=to+Δt(seconds), t2=t0+
2Δt (seconds)..., and the corresponding measurement distance increases. This distance change is as shown by the straight line 41 in Figure 5. Assuming that the rubidium oscillators 12 and 19, which are the reference signal sources on the transmitting and receiving sides, are stable and there is no change in frequency, the movement of the transmitting and receiving sides Alternatively, the measurement error due to the frequency difference increases at a constant slope with respect to time, regardless of the state such as stationary.

In Fig. 5, when the sending and receiving sides are stationary, this constant slope corresponds to the increase L in the measured distance at time To (seconds).
By measuring o (m), it can be obtained using equation (2).

K= L, /To・・・・・・・・・・・・・・・
(2) In Fig. 5, the curve 42 indicates the actual distance between the sending and receiving sides (actual distance 11111
), which shows the change in time Tr (
The signal remains stationary at a distance s0 (m) until 2 seconds), 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 the measured distance by the device of this embodiment at this time.Even though the transmitting and receiving sides are stationary until time T+C seconds), due to the measurement error based on the frequency difference mentioned above, From the initial value S≦(m), the measured distance increases at a constant slope as shown by the straight line 41, and after T1 (seconds) has elapsed, the distance shown by the curve 43 is measured by the time-distance converter 17 in FIG. It represents that. Here, the actual distance MSo (
m) and the measured distance So(m) in the initial state.
), which represents a measurement error caused by the phase difference between the signals 31 and 32 shown in FIG. 4 in their initial states.

So −So = tdx c (m) == (3) Also, the measured distance s1 (m) at the elapsed time T+, C seconds)
and the actual distance #So (m) (1) have the relationship shown in equation (4).

S6-3l =LL =tc+Xc-KXTI
(m)・・・・・・・・・・・・(4) In equation (4), the elapsed time T from the initial state 0.

The measurement error in (seconds) includes the measurement error tdXc(m) caused by the above-mentioned phase difference in the initial state and the measurement error KXTl(m) caused by 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 with 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.

In order to obtain the measurement error based on the frequency difference as described above,
The time-distance converter 17 calculates the amount of increase Lo (m) in the measured distance from the initial state O to the time T0 (seconds) in a stationary state.
The constant slope of increase K is determined according to equation (2) and stored in the distance corrector 2o. On the other hand, if the distance measurement start point is a point T+ (seconds) has elapsed from the initial state, the measurement error L+ (m) based on the above phase difference at this point is determined by the transmission and reception determined in advance according to equation (4). This value L is determined by the difference between the distance mso (m) between points and the distance Sx (m) measured by the time-distance converter 17.
+(m) is stored in the distance corrector 2o. Next, T.
Song from the starting point of distance measurement! Assuming that there is a change in the distance between transmission and reception as shown in 1142, the time-distance converter 17 converts curve 4 including measurement errors based on the frequency difference and phase difference mentioned above.
3 changes are shown. Therefore, from the distance measurement starting point T, (TTI
) (seconds), the actual pressure MMO (m) at the point in time is calculated by adding the above L+ (m) to the measured distance M+ (m) at that time.
Furthermore, it is obtained by subtracting the measurement error L (m) shown in the equation (5) based on the frequency difference in the above two, and the measurement error L (m) is
The relationship of the formula holds true.

t=KX (T-T+)(m) Old, old and old--(5
)Mo=M,+L,-L=M,+(So-3,)(K
X (T-T+) )...Old・dan・(6)In addition,
The above distance correction function is L+ stored in the distance corrector 20.
(m) + K and y of equation (5)! , by adding and subtracting Ll(m) and L(m) on the distance display 18 to the distance measured by the time-distance converter 17, according to L(m) obtained by calculation. In Figure 5,
A curve 44 shows a case where the actual distance curve 42 includes a measurement error based on the above-mentioned frequency difference, and a curve 45 shows a case in which 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 over time ΔT (seconds). Distance indicator 1 when corrected by interval
8, and shows that the shorter ΔT (seconds) is, the closer the curve 45 becomes to the curve 42 showing the change in actual distance.

Note that the period t12 (seconds) of the above signal 31 and Δt,
The relationship of Equation (7) holds true between K, To, Lo, etc.

K=(Δt/l+2)Xc=Lo/T.

=L/(TTI)...Group(7) Here, ΔE/t I 2 is the frequency fl 2
(Hz) and f+9 (Hz), and even when using an ordinary rubidium oscillator, Δt/l
, 2<16-'' is relatively easy, and this shows that even if there is a difference in image frequency, 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. The high stability signal source provided on the transmitting side and the receiving side is used as a reference signal source for creating a reference signal, and on the other hand, the highly stable signal source on the receiving side is used as a reference signal for measuring the delay time in which the reference signal for distance measurement propagates. Measurement errors due to mutual frequency and phase differences between sources are calculated by calculating the rate of change in measured distance over time caused by the frequency difference when the transmitter and receiver are stationary, and the rate of change in measurement distance over time caused by the phase difference between the transmitter and receiver. Since we have provided a means of correction based on the difference between the actual distance and the measured distance, even if the relative distance between the transmitting side and the receiving side changes, highly accurate distance measurement can always be performed using a reference signal with high frequency stability. It has an extremely excellent effect.

[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 main parts 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, 12.19 is a rubidium oscillator,
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
2 is a distance indicator, and 20 is a distance corrector.

Claims (1)

[Claims] 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 the signal is transmitted between the two, each of the transmitting side and the receiving side has a high A highly stable signal source with 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 source for distance measurement. As a reference signal source for measuring the propagation delay time, measurement errors due to mutual frequency differences and phase differences between the highly stable signal sources provided on the transmitting side and the receiving side were measured in advance when the transmitting side and the receiving side were stationary. A one-way device characterized by having means for correcting based on the rate of change of the measured distance with respect to time caused by a frequency difference in the state, and the difference between the actual distance and the measured distance between the transmitting side and the receiving side caused by a phase difference. Ranging device.