JPH1164507A - Range finder method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform a highly precise range measurement by correcting the detected values of the time difference and phase difference between a response signal returned with a delay quantity data added thereto after receiving a question signal and the question signal by use of the delay quantity data. SOLUTION: A question device (a) modulates a signal generated by a pulse generator 1 by a transmitter 2, and transmits it as a question signal St to a response device (b) through an antenna 3. The response device (b) receives the question signal by an antenna 4, modulates it with the natural delay quantity data of the device after removing an unnecessary component by a band-pass filter 5, and transmits the result as a response signal through the antenna 4. The question device (a) receives the response signal followed by amplifying, and then removes an unnecessary component by a band pass filter 7 to provide an output Sr. The time difference and phase difference between St and Sr are detected by a time difference wave detector 8 and a phase wave detector 9, digitized by A/D converters 10, 11, respectively, and inputted to a control circuit 12 together with the correction value by the delay quantity data to calculate the distance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring method using radio waves, and more particularly, to comparing a time difference and / or a phase difference between interrogation signals or response signals with a wavelength of an interrogation signal or response signal frequency, and according to the result, the time difference and / or phase difference is determined. The present invention relates to a method for optimally combining phase differences and correcting using system delay data (fixed values of time and phase delay by control and processing) to enable accurate measurement. According to the present invention, the response device is attached to a moving vehicle, an animal, a human, or the like, and the distance from the interrogation device is measured to grasp the position.

[0002]

2. Description of the Related Art Two methods have been proposed as methods for measuring a distance by detecting a phase difference or a time difference between interrogation signals or response signals using radio waves.

First, in the conventional distance measurement method using phase difference detection, distance measurement can be performed by detecting only the phase difference under the condition that the distance is less than 1/2 wavelength of the interrogation signal or response signal. Since the phase difference is a periodic function of the wavelength of the interrogation signal or the response signal, accurate measurement is difficult only with the phase difference when the distance exceeds 1/2 wavelength.

On the other hand, in the conventional distance measuring method by detecting a time difference, in a method of detecting a time difference between a radio wave inquiry signal and a response signal, a counter measures a delay time difference from signal transmission to signal reception to obtain a distance. ing. However, this counter system can measure with high accuracy when the distance is large, but is an ultra-high-speed expensive counter when the distance is short.
Is required. For example, at a distance of 1 m, the propagation time of a radio wave is 0.0067 μsec. To measure such a short time, a clock frequency of at least 151 MHz is required.
Needless to say, the response time jitter until the response device receives a query and responds is required to be several nsec or less. Of course, since the actual system time delay is usually several μsec, it is substantially impossible to measure. It is possible.

[0005]

However, the prior art as described above has the following problems. (1) It is difficult to measure the entire section from a short distance to a long distance with high accuracy by only one of the methods of detecting the phase difference or the time difference between the interrogation signal and the response signal. (2) Further, the delay amount data of the system has a difference in the absolute value for each response device, which causes a limitation in the distance measurement accuracy.

[0006]

An interrogation signal sent from an interrogation device is received by a response device, and a response signal to which an inherent delay amount data is added for each response device is returned to the interrogation device. The true time difference and the true time difference are corrected by correcting the time difference and the phase difference between the interrogated signal received and transmitted by the interrogator using the delay amount data unique to each of the responders. A distance measuring method by a radio wave having a means for measuring a distance by obtaining a true phase difference, wherein the true time difference is automatically compared with a time value corresponding to one wavelength of an interrogation signal or a response signal frequency, If it is less than the time difference corresponding to one wavelength, the distance is calculated only by the true phase difference, and if it is equal to or greater than the time difference corresponding to one wavelength, one wavelength of the interrogation signal or response signal frequency for the true time difference Equivalent to Integral multiple of the ratio between the two times the half wavelength + means for calculating the distance based on only the true phase difference, and a highly accurate distance over the entire measurement section by optimally combining the time difference and / or the phase difference. It has a distance measurement method that allows calculation.

[0007]

FIG. 1 is a block diagram showing one embodiment of the present invention. FIG. 1 (a) is an inquiry device, FIG. 1 (b)
Shows an embodiment of a response device. The operation will be described below.

The interrogating device modulates the signal generated by the interrogating pulse generating circuit 1 by the transmitter 2 to generate a signal having a frequency f1 and transmits it as St to the responding device from the antenna 3. This is used as an inquiry signal.

The transponder receives the interrogation signal St by the antenna 4, amplifies the signal, and removes unnecessary signal components through a bandpass filter 5. The delay amount data of the signal in the transponder is not zero, and the delay amount data differs for each transponder. In each response device, a read-only memory (RO
M) These actual values are written in 6 and encoded to modulate the response signal and transmitted from the antenna 4 of the transponder.

[0010] After the interrogator receives and amplifies the response signal from the antenna 3, it removes unnecessary signal components with a bandpass filter 7,
The output is defined as Sr.

An interrogator detects a phase difference between St and Sr by a time difference detector 8 and a phase detector 9 between St and Sr. In this case, if the delay amount data of the transponder is set to zero, the true phase difference between St and Sr becomes a sine wave function of the distance. The detected time difference and phase difference outputs are converted into digital signals by the A / D converters 10 and 11, respectively, and input to the control circuit 12 together with the correction value based on the delay amount data to calculate the distance. .

As an actual application example, measurement of an inter-vehicle distance will be described below. For the sake of simplicity, it is assumed that the interrogation device is mounted on one vehicle and the response device is mounted on the other vehicle, and the delay amount data of the system is zero. It is difficult to measure a distance of several meters by measuring the time difference between the interrogation signal and the response signal by radio waves. However, if the measurement is performed by detecting the phase difference, it can be realized more easily than the time difference measurement. For example, if the distance between the interrogator and the responder is R (m), and the reciprocating distance 2R is shorter than the wavelength λf1 (m) of the interrogation signal or response signal frequency f1, the radio wave reciprocates over the distance R. The true time T can be expressed by the following equation. T = 2R [m] / 300 [m / μsec] (μsec) where 2R <λf1 (1) If the signal reciprocates over the distance R, the true phase difference Φ is given by the following equation. Φ = 2π (2R / λf1) (radian) where Φ <2π (2) If R is a short distance of several meters, T is a very small value. Assuming that R = 1m, T = 0.
0067 μsec, and an expensive ultra-high-speed counter is required to measure this value. However, the wavelength λf1 = 1
Using a frequency of 0 m (f1 = 30 MHz), Φ =
2π × 2/10, which facilitates detection. In this method, first, a time difference from a question to a response is detected, and it is determined whether or not the time difference exceeds a time length of a radio wave traveling back and forth over one wavelength of an inquiry signal or response signal frequency. If it is less than an integral multiple, the distance is less than half the wavelength of the interrogation signal or the response signal, and the distance can be calculated only from the true phase difference according to equation (2). If it is an integral multiple or more, it is 1/2 wavelength or more, and the distance R + is an integral multiple of the ratio of the time (Tf1) corresponding to one wavelength of the interrogation signal or response signal frequency to the true time difference × 1/1.
R + = Integer multiple of T / Tf1 × 1 / 2λf1 + Distance calculated by equation (2) (provided that 2R ≧ λf1) (3) By optimally combining the time difference and / or the true phase difference, it is possible to measure with high accuracy over the entire section from a short distance to a long distance.

In the above equations (1) to (3), the delay amount of the system is assumed to be zero. However, in an actual system, there is a delay amount of a time difference and a phase difference for each response device. The method must be specifically described. Here, the detected values of the time difference and the phase difference from the interrogation signal St to the response signal Sr are Tm and Φm, respectively, and the actual system time difference and the phase difference delay amount are Td ′ and Φd ′, respectively. The time and phase delay amount data (fixed values) are Td,
If Φd, the time (fixed value) corresponding to one wavelength of the interrogation signal or the response signal frequency is Tf1, and the comparison standard of the time difference is Tr, the following equation is established. Tm = T + Td ′ Here, if Td ′ = Td, T = Tm−Td ′ = Tm−Td........... The true time difference can be represented by the difference between the detected value of the time difference and the time delay data for each responding device. Next, the comparison standard of the time difference is expressed by the following equation. Tr = Tf1 + Td (fixed value) If the difference is taken to compare Tm and Tr, Td ′ = Td
d, Tm−Tr = T−Tf1 + Td′−Td = T−Tf1 (5). By taking the difference, it is possible to compare the true time difference with the time corresponding to one wavelength of the interrogation signal or response signal frequency. As for the phase difference, assuming that Φd ′ = Φd, Φm = Φ + Φd ′ = Φ + Φd Φ = Φm−Φd ………………………………… (6) The true phase difference can be represented by the difference between the detected value of the phase difference and the phase delay amount data for each response device. Therefore, according to the above equation (5), the distance when Tm−Tr <0 is less than 波長 wavelength of the interrogation signal or response signal frequency, so that the true phase difference is calculated by the equation (2) using the value of the equation (6). Only calculate the distance. Since the distance when Tm−Tr ≧ 0 is equal to or more than 波長 wavelength of the frequency of the interrogation signal or the response signal, Equation (3), that is, T /
Integer multiple of Tf1 × 1 / 2λf1 + Using the value of equation (6) (2)
The distance is calculated using only the true phase difference according to the equation.

[0014] In the case where the specific detected value and delay amount data and the like for the above inter-vehicle distance measurement are as follows, Tm = 3.0
2 μs (detected value of time difference between St and Sr) Td = 3.00 μs (time delay data of response device) Φm = 1.35π (detected value of phase difference between St and Sr) φd = 0.15π (response device Tf1 = 0.03 μs (interrogation signal or response signal frequency: f
1 = 30 MHz) λf1 = 10 m (interrogation signal or response signal frequency: f
1 = 30 MHz) From equation (4), T = 0.02 μs, and from equation (5), Tm
Since −Tr = T−Tf1 = 0.02 μs−0.03 μs <0, the distance is １ ／ of the interrogation signal or response signal frequency.
Less than the wavelength, and from equation (6), Φ = 1.35π-0.
By calculating 15π = 1.20π and substituting it into equation (2), R = 3m can be calculated from 1.20π = 2π (2R / 10), and this value is obtained by calculating T =
This value matches the value R = 3 m calculated by substituting 0.02 μs. Next, only the detected value due to the movement of the vehicle becomes Tm = 3.0.
When 6 μs and Φm are changed to 1.75π, T = 0.06 μs from equation (4) and Tm−Tr =
Since T−Tf1 = 0.06 μs−0.03 μs> 0, the distance is equal to or more than 波長 wavelength of the interrogation signal or the response signal, and the distance based only on the phase difference is Φ = 1.7 from the equation (6).
By calculating 5π−0.15π = 1.60π and substituting it into the expression (2), R = 4m can be calculated from 1.60π = 2π (2R / 10). R + = 0.06 / 0.03 × 1/2 × 10 + 4 = 14 m.

In the above distance measurement, the delay amount Td 'of the time difference and the phase difference in the actual system in the equations (4) to (6),
It is assumed that .PHI.d 'is equal to the delay time data Td and .PHI.d of the time difference and the phase difference of each responder, but in reality, Td' and .PHI.d 'have a jitter (fluctuation) component. Affects the accuracy of measurement. Therefore, taking into account the measurement accuracy of the system, the tolerance of the jitter component for the delay data Td and Φd of the time difference and the phase difference of each responder, the jitter tolerance for the delay data of the time difference, δt = ± (Td′−Td) / Td × 100% (7) Jitter-tolerance of delay amount data of phase difference, δφ = ± (Φd′−Φd) / Φd × 100% (8), and the jitter component of the delay time data of the actually measured time difference and phase difference falls within the allowable range, for example, By setting δt = ± 5% and δφ = ± 7% from equations 7) and (8), Td ′ = 3.00 μs ± 0.15 μs, Φ
If d ′ = 0.15π ± 0.01π, then T
Assuming that d ′ = Td and Φd ′ = Φd, (4) to (6)
It is also possible to perform a distance calculation by an expression. Therefore, it is possible to maintain the accuracy and reliability of the distance measurement by setting the jitter-tolerance of the actually measured value for each system.

[0016]

According to the present invention, the measurement distance is automatically determined according to the wavelength of the interrogation signal or the response signal which is the reference signal for detecting the time difference and the phase difference, and the detected values of the time difference and / or the phase difference are optimally combined to obtain a total. High-precision measurement over a distance can be realized easily and at low cost. Further, it is possible to maintain the accuracy of distance measurement and improve the reliability by setting the jitter tolerance for the delay amount data for each response device for each system.

[Brief description of the drawings]

FIG. 1 is an embodiment according to the present invention, wherein FIG. 1a) is an interrogator and FIG. 1b) is a responder.

[Explanation of symbols]

1. Interrogation pulse generation circuit 2. Transmitter of interrogation device 3.
Interrogator antenna, 4 ... Answerer antenna, 5 ... Answerer bandpass filter, 6 ... Answerer read-only memory (R
OM), 7: Interrogator bandpass filter, 8: Time difference detector, 9: Phase detector, 10, 11: A / D converter, 12
... Control circuit

Claims (2)

[Claims] An interrogation signal transmitted from an interrogation device is received by a response device, and a delay amount data unique to each response device is received.
The response signal with the data added thereto is returned to the interrogator, which is received by the interrogator, and a time delay and phase difference between the transmitted interrogation signal and the received response signal are used to determine the delay inherent in each of the responders. A distance measuring method using a radio wave, comprising means for measuring a distance by obtaining a true time difference and a true phase difference by correcting using quantity data. 2. The method of automatically comparing the true time difference with a time value corresponding to one wavelength of an interrogation signal or response signal frequency,
If it is less than the time difference corresponding to one wavelength, the distance is calculated only by the true phase difference, and if it is equal to or greater than the time difference corresponding to one wavelength, one wavelength of the interrogation signal or response signal frequency for the true time difference Integer multiple of time ratio corresponding to x 1 /
A distance measuring method comprising means for calculating a distance based on only two wavelengths and a true phase difference, and capable of calculating a distance with high accuracy over an entire measurement section by optimally combining a time difference and / or a phase difference.