JP3164206B2 - Time interval measurement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a measuring method using an electric signal in measuring a distance to a moving object under test, and more particularly, to an arbitrary time when a signal under test is received using a code string having a periodicity. The present invention relates to a time interval measurement method suitable for measuring a time difference from transmission, that is, a distance.

[0002]

2. Description of the Related Art Conventionally, as a time interval measuring method for measuring an occurrence time interval between two different timing signals, for example, a method disclosed in Japanese Patent Application Laid-Open No. 5-164796 is known. In this case, when two timing signals are assumed to be a signal A and a signal B, a time is measured from the generation of the signal A to the generation of the signal B over both positive and negative times. FIG. 4 is a block diagram showing an example of the time interval measurement method described in the above publication. In FIG.
The signal 400 and the signal 400 before or after this signal 400
Is measured up to a signal 404 generated in association with.

[0003] In FIG. 4, a delay means 41 is provided with a signal 40.
0 is delayed for a certain period of time to generate a delayed signal 401,
The counting means 42 monitors the delay signal 401 and
The counting is started by detecting the counting start condition such as the rising or falling edge of 1 and then the signal 400 is monitored and the signal 4 is monitored.
The counting is terminated when a counting end condition such as a rising or falling edge of 00 is detected. Similarly, the counting means 43
Monitors the delay signal 401 to detect a count start condition such as a rise or fall of the delay signal 401 and starts counting, and then monitors the signal 404 to count the count end condition such as a rise or fall of the signal 404. The counting is terminated when is detected.

In counting, a clock 405 generated by the reference clock generating circuit 45 during the counting period is counted by counting means 42 and 43.
Is performed by counting. After the counting is completed, the measurement result processing unit 44 calculates the count result 402 from the generation of the delay signal 401 to the input of the signal 400 and the count result 403 from the generation of the delay signal 401 to the input of the signal 404. Read, convert each count value into time, and count
The time difference obtained by subtracting the count result 403 from 2 is output as the measurement result.

[0005]

In this prior art, a measurement result is obtained at the time when the counting means 42 and 43 finish counting. For example, when the distance to the object to be measured is measured by the propagation delay time. However, the timing at which the transmitted signal is received varies according to the distance, and is asynchronous with the time right second. There was an inconvenience that it could not be done.

An object of the present invention is to provide a time interval measuring method capable of measuring the time of reception of a signal under measurement in synchronization with an arbitrary time in measuring the time difference from the time of signal transmission to the time of reception of the signal under measurement. It is an object.

[0007] The resulting delay time difference is
It is an object of the present invention to provide a time interval measurement method capable of measuring at a high resolution using a reference clock transmitted at a low frequency.

[0008]

According to a time interval measuring method of the present invention, a timing signal periodically generated by using a repetitive code sequence (for example, a pseudo random noise code sequence), and the timing signal after the timing signal are generated. In measuring the time difference between the signal to be measured and the signal to be measured periodically generated, the phase difference between the code phase of the repetition code string when the measurement timing signal is arbitrarily set and the code phase when the signal to be measured is generated is calculated. It is characterized in that it is obtained as a measurement result.

Specifically, a transmission code phase coarse measuring means for obtaining a transmission phase of the code sequence of the timing signal at the measurement timing, and a reception for obtaining a reception phase of the code sequence of the signal under measurement at the measurement timing. In order to measure a time difference of one chip (one bit) or less of a code string, a time difference from a measurement timing to a next code string data transient of the timing signal is measured with high resolution. There is provided a transmission code phase measuring means and a reception code phase measuring means for measuring a time difference from a measurement timing to a next code string data transient of the signal under measurement with high resolution.

In addition, the measurement timing is not a timing signal transmission but an arbitrary timing at the time of receiving the signal under measurement, and the measurement timing from the code phase at the time of receiving the signal under measurement to the timing signal transmission at which the phase is transmitted is transmitted. It is characterized by measuring back in time.

The time interval measuring method according to the present invention comprises:
The timing signal code string transmission phase and the signal under test code string reception phase at the measurement timing are measured by the transmission code phase coarse measurement means and the reception code phase coarse measurement means, and the reception phase is subtracted from the transmission phase by the measurement result processing means, Since the time difference is obtained by dividing by the chip frequency of the timing signal at this time, the time difference until the time when the same phase as the phase of the signal sequence under test at the measurement timing is transmitted by the timing signal is measured retroactively. be able to.

Since the time from the measurement timing to the next code string data transient is measured by the transmission code phase precise measurement means and the reception code phase precision measurement means, the time difference is measured to a resolution of one chip length or less. be able to.

[0013]

FIG. 1 is a block diagram showing an embodiment of a phase measurement type time interval measurement system according to the present invention. In FIG. 1, the transmission code phase coarse measuring means 1 comprises:
The transmission phase of the code sequence of the timing signal at the measurement timing is obtained as a result. The transmission code phase precise measuring means 2 measures the time difference from the measurement timing to the next code string data transient of the timing signal with high resolution in order to measure the time difference of one chip length or less of the code string.

The received code phase coarse measuring means 3 obtains, as a result, the received phase of the code sequence of the signal under measurement at the measurement timing. The received code phase precise measuring means 4 measures the time difference from the measurement timing to the next code string data transient of the signal to be measured with high resolution in order to measure the time difference of one code chip length or less. The reference clock generator 5 generates a reference clock signal for counting by the phase precise measuring means 2 and 4.

The measurement result processing means 6 calculates a time difference between a code string transmission phase of the timing signal, a code string reception phase of the signal under test, and a measurement timing from the next code string data transient of the timing signal, and a next measurement based on the measurement timing. The time difference of the signal under test up to the code string data transient is read, and the transmission / reception code phase difference is converted to time and measured.

Next, the operation of the embodiment of the present invention will be described with reference to FIG. The transmission timing signal 100 periodically generated using the repetition code sequence is supplied to the transmission code phase coarse measuring means 1. The transmission code phase coarse measuring means 1 determines the transmission phase 1 of the code sequence of the transmission timing signal 100 at the appearance timing of the measurement timing signal 109.
05 as a result. This transmission code coarse measurement phase 105
Is supplied to the measurement result processing means 6. Further, the transmission code phase coarse measuring means 1 supplies the code sequence data transient timing of the transmission timing signal 100 appearing after the measurement timing signal 109 to the transmission code phase fine measuring means 2 as a transmission trigger signal 101.

The transmission code phase precise measuring means 2 monitors the measurement timing signal 109 and starts counting when a counting start condition such as rising or falling of the signal is satisfied, and thereafter monitors the transmission trigger signal 101 and finishes counting. When the condition is satisfied, the counting ends. The counting is performed by counting the clocks 104 generated by the reference clock generator 5 during the counting period. After the counting is completed, the counting result is supplied to the measurement result processing means 6 as the precise measurement phase 106.

Similarly, after the transmission timing signal 100, the signal under test 102 which periodically occurs in association with the transmission timing signal 100 is supplied to the received code phase coarse measuring means 3. The reception code phase coarse measuring means 3 obtains the reception phase 107 of the code sequence of the signal under measurement 102 as a result at the appearance timing of the measurement timing signal 109. The received code coarse measurement phase 107 is supplied to the measurement result processing means 6. Further, the received code phase coarse measuring means 3 determines the code string data transient timing of the signal under measurement 102 appearing after the measurement timing signal 109 as the reception trigger signal 1.
03 is supplied to the received code phase precise measuring means 4.

The reception code phase precise measuring means 4 monitors the measurement timing signal 109 and starts counting when a counting start condition such as rising or falling of the signal is satisfied, and thereafter monitors the reception trigger signal 103 and finishes counting. When the condition is satisfied, the counting ends. The counting is performed by counting the clocks 104 generated by the reference clock generator 5 during the counting period. After the counting is completed, the counting result is supplied to the measurement result processing means 6 as the precise measurement phase 108.

The measurement result processing means 6 divides the transmission / reception code phase difference obtained by subtracting the reception code coarse measurement phase 107 from the transmission code coarse measurement phase 105 by the data rate of the transmission timing signal 100 to obtain the signal to be measured at the measurement timing. A coarse time difference from the timing at which the reception code phase of 102 is transmitted by the transmission timing signal 100 to the measurement timing is calculated. Also, by subtracting the reception code precise measurement phase from the transmission code precise measurement phase 106 and converting the time into a time, a precision time difference of one code chip length or less at the measurement timing can be obtained. The value obtained by adding the coarse time difference and the fine time difference is the measurement result.

FIG. 2A is a block diagram showing another embodiment of the present invention. In FIG. 2A, the coarse measuring means counts up at the frequency f _TX (chip clock) 202 of the transmission timing signal, and clears the N _TX counter 2 to 0 at the repetition timing 201 of the transmission signal.
N _RX counter 2 which counts up at 1 and frequency f _RX (chip clock) 206 of the signal under measurement (received) and is cleared to 0 at the repetition timing 205 of the received signal
3 and the rising edge of the transmission chip clock subsequent to the measurement timing 218 is detected, and a trigger 204
Trigger output unit 22 for outputting the measurement timing 218
Trigger generator 24 which detects the rising edge of the next receiving chip clock and outputs trigger 208 to the subsequent precision measuring means.
Consists of

Further, the precise measuring means is provided with a measuring timing 218
The frequency (r) slightly shifted from the reference frequency (f _REF ) 209 in synchronization with the rising edge of the next transmission chip clock
f _REF ) 210, and the reference frequency (f _REF ) 2 synchronized with the rise of the receiving chip clock next to the measurement timing 218.
An RX multivibrator 30 that starts oscillating at a frequency (rf _REF ) 214 slightly deviated from 09 and an N _dTX counter that clears 0 at the start of oscillation of the TX multivibrator 26 and counts up at a frequency (rf _REF ) 210 29, an N _dRX counter 32 that is cleared to 0 at the start of oscillation of the RX multivibrator 30 and counts up at a frequency (rf _REF ) 214, and is cleared to 0 at a measurement timing 218 and counts at a reference frequency (f _REF ) 209. and N _O counter 28 for up, rf _REF signal 210 and the reference f _REF from TX multivibrator 26
The slip timing at which the phase of the signal 209 intersects is monitored, the slip timing is extracted, and the _NdTX counter 2
TX comparator 2 for generating a timing for latching the count value 212 of the count value 213 and N _O counter 28 9
7, monitors the slip timing of the phase of the rf _REF signal 214 and the reference f _REF signal 209 from RX multivibrator 30 is crossed, the count value 216 and N _O counter 29 the N _DRX counter 32 extracts the slip timing The RX comparator 31 generates the timing for latching the count value 212 of.

The TX multivibrators 26 and R
As shown in FIG. 2B, the X multivibrator 30 is, for example, a NAND as a multivibrator.
Circuit 51 and delay circuit 5 for delaying its output by τ time
2 can be configured. The oscillation frequency is 1 /
2τ.

Further, the measurement result processing means 33 includes a count value 203 of the N _TX counter 21 and a count value 207 of the N _RX counter 23 latched at the timing of the measurement timing 218, and a count value 212 of the N _O counter 28.
And the count value 213 of the N _dTX counter 29 and the count value 216 of the N _dRX counter 32 are read and subjected to arithmetic processing to obtain a time-converted measurement result.

Next, the operation will be described with reference to FIG. In this embodiment, a time difference between a transmission signal that periodically occurs using a repetition code sequence and a reception signal that periodically occurs in association with the transmission signal after the transmission signal is calculated.
In a method (reception time tag method) that measures the time from the phase of a received code sequence to the time when the phase was transmitted based on the measurement timing (reception time tag method), the resolution of the code sequence phase difference between the transmission signal and the reception signal is determined. It is a further improvement.

As shown in FIG. 3A, in order to calculate the time difference of one chip length (one bit length of the code string) resolution,
The code repetition period is set as the phase amount 2π [rad], and from the time (start) when the same phase as the received signal appears from the phase θ _{RX of the} received signal and the phase θ _{TX of the} transmitted signal at the reception timing (stop timing) to the measurement timing The time difference between the time points (stops) is determined by the phase amount (θ:
θ _TX −θ _RX ). Therefore, the time difference T of one chip length resolution is: T = (1 / f _TX ) · (θ _TX −θ _RX ) (1) f _TX : transmission signal frequency (chip clock frequency) θ _TX : N _TX counter at measurement timing Θ _RX : can be obtained as the count value of the N _RX counter at the measurement timing.

As shown in FIG. 3B, in order to calculate a time difference of resolution equal to or less than one chip length, the phase angle of the transmission signal with respect to one chip clock bit at the measurement timing is set to Δθ _TX and the reception signal is calculated. Assuming that a phase angle with respect to one chip clock bit is Δθ _RX , a time difference ΔT of a transmission signal and a reception signal equal to or less than one chip length is ΔT = (1 / f _TX ) · (1 / 2π) [Δθ _RX −Δθ _TX ] ( 2) can be expressed as

[0028] In FIG. 2, RX comparator 31, N _O counter 28 that is cleared by the measurement timing signal 218
A clock signal 209 for counting up at the reference frequency f _REF and the _NdRX counter 32 cleared to 0 when the RX multivibrator 30 starts oscillating
The N _O counter 28 and N _DRX count values 212 and 216 of the counter 32 at the time of detecting a phase slip of the clock signal 214 which counts up at a frequency rf _REF shifted slightly frequency than _REF respectively N _ORX
And the N _DRX, also, TX comparator 27, the clock signal 2 that counts up N _O counter 28 that is cleared by the measurement timing signal 218 at a reference frequency f _REF
09, upon detecting a phase slip of the clock signal 210 which counts up at a frequency rf _REF shifted slightly frequency N _DTX counter 29 which is cleared by the oscillation start time than the reference frequency f _REF of the TX multivibrator 26 N _O counter 28 and N _DTX counter 29 in
_Let the respective count values 212 and 213 be N _OTX and N _dTX , respectively, the time difference ΔT of one chip length or less represented by the equation (2) is ΔT = (1 / f _REF ) [(N _ORX −N _dRX / r) - a _{(N dRX -N dTX) / r} ] (3) - (N OTX -N dTX / r)] = (1 / f REF) [(N ORX -N OTX).

Here, r is a coefficient for slightly shifting the frequency from the reference frequency f _REF , and r = N / (N + 1)
Expanding equation (3) as follows: ΔT = (1 / f _REF ) [(N _ORX −N _OTX ) − (N _dRX −N _dTX ) −
( _{NdRX- NdTX} ) / N]. That is, the measurement resolution is changed from 1 / f _REF to (1
/ F _REF ) · (1 / N). For example, 1 nse
c resolution required and reference frequency fREF 10 MH
When z is set, N = 100 (rf _REF = 9.909M)
Hz).

The time interval measurement value 217 is (1)
Since it is obtained by adding the equation and the equation (3), if this is T _O , T _O = T + ΔT = (1 / f _TX ) (θ _TX −θ _RX ) + (1 / f _REF ) [(N _{ORX- NOTX} )
− (N _dRX −N _dTX ) / r].

[0031]

According to the present invention, since the time difference between transmission and reception is measured as the phase difference of the transmission signal from the received phase to the time when the phase was transmitted, the measurement timing can be set arbitrarily. Can be. Therefore, when time is added to the measured value, the measured value at an arbitrary reception time based on the measurement timing can be obtained.

[0032]

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a phase measurement time interval measurement method according to the present invention.

FIG. 2 is a block diagram showing another embodiment of the phase measurement type time interval measurement method of the present invention.

FIG. 3 is a diagram for explaining the operation of FIG. 2;

FIG. 4 is a diagram showing a conventional example.

[Explanation of symbols]

DESCRIPTION OF REFERENCE NUMERALS 1 Transmit code phase coarse measuring means 2 Transmit code phase fine measuring means 3 Receive code phase coarse measuring means 4 Receive code phase fine measuring means 5, 25, 45 Reference clock generator 6, 33, 44 Measurement result processing means 21, 23 28, 29, 32, 42, 43 Counter 22, 24 Trigger generator 26, 30 Multivibrator 41, 52 Delay circuit 51 NAND circuit

Claims (4)

(57) [Claims] 1. A method for measuring a time difference between a timing signal generated periodically using a repetitive code string synchronized with a chip clock and a signal under test for generating the periodic repetitive code string signal related to the timing signal. In the time interval measurement method, the code phase of the repetition code sequence of the timing signal and the code phase of the repetition code sequence of the signal under measurement at an arbitrary measurement timing when the signal under measurement is received. A time interval measurement method characterized in that a delay time is measured from a phase difference between the time interval. 2. A method for measuring a time difference between a timing signal periodically generated by using a repetitive code sequence synchronized with a chip clock and a signal to be measured for generating the periodic repetitive code sequence signal related to the timing signal. In the time interval measurement method, the coarse measuring means for measuring the code position of the repetition code string of the timing signal at an arbitrary measurement timing at which the signal under measurement is received, and the phase of one code length or less of the code string. Precise measuring means for measuring, coarse measuring means for measuring a code position of the repeated code string of the signal under measurement, and fine measuring means for measuring a phase of one chip or less of the code string; A time interval measuring method characterized in that a delay time is measured by adding a difference between the phase difference and a phase difference. 3. A first counter for detecting the measurement timing and starting counting, detecting a first rising edge of the transmission chip clock after the measurement timing, and terminating the counting; 3. A second counter for detecting the measurement timing, starting counting, and detecting the first rising edge of the receiving chip clock after the measurement timing and terminating the counting. The time interval measurement method described. 4. The precise measuring means detects a measurement timing and starts counting a clock of a predetermined reference frequency, and detects a first rising of the transmission chip clock after the measurement timing. A second counter which starts counting a clock having a frequency slightly deviated from the predetermined reference frequency, and detects a first rising of the reception chip clock after the measurement timing and deviates slightly from the predetermined reference frequency. A third counter that starts counting clocks of a frequency, and monitors a slip timing at which a phase of the clock of the predetermined reference frequency and a clock of a frequency slightly shifted from the predetermined frequency intersect with each other. Detecting the intersection of the phases of the clocks supplied to the second counter,
A first comparator for generating a timing for latching the count value of the first counter, and detecting the intersection of the phases of the respective clocks supplied to the first counter and the third counter to detect the first and second counters. 3. The time interval measuring method according to claim 2, further comprising a second comparator that generates a timing for latching the count value of the third counter.