JP2002107393A - Instrument for measuring time interval - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measuring instrument for measuring time differences (time intervals) between two signals in a DVD and the like, in which a time measuring circuit is simplified. SOLUTION: A time interval measuring instrument is constituted at least of a means for converting two input signals to digital signals respectively, a means for producing time the difference between the rising edge of one digital signal and the rising edge of the other digital signal which follows a specific clock signal among the converted digital signal. For the clock signal, one of the two signals is substituted on the condition that maximum time difference of the two signals be limited to be a prescribed value. The instrument has a means of converting the time difference produced into voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a time interval measuring device, and more particularly to a measuring device for measuring a time difference (time interval) between two signals in a DVD or the like, or a standard deviation (jitter) based on measured time data. The present invention relates to a measuring instrument which outputs a statistical value of, and has a simplified time measuring circuit.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram showing an example of a conventional time interval measuring device, which has a two-series circuit configuration for inputting two signals and measuring a time difference therebetween.

A signal input terminal Ch for inputting two signals
A and ChB are connected to the buffer amplifiers 110 and 160, respectively. Output signals of the buffer amplifiers 110 and 160 are input to one input terminal of the comparators 130 and 180, and are converted into binary signals that leave only edge information. The other input terminal of the comparators 130 and 180 has a D / A
Binarized trigger levels are input from converters 120 and 170.

The output signals of the comparators 130 and 180 and the reference clock of the clock generation circuit 150 are input to the fraction extraction logic circuit 190. The fraction cut-out logic circuit 190 has a signal input terminal Ch.
An edge to be measured is selected from the input signals input to A and ChB, a fraction below the reference clock is cut out, and fraction pulse signals TX and TY are generated, and a count clock XC is generated.

[0005] Time / voltage (T / V) conversion circuits 200, 3
Numeral 30 denotes a fractional time of the fractional pulse signals TX and TY, and voltages VX and VY (Vs) proportional to the pulse widths Tstart and Tstop.
tart, Vstop). A / D converter 210,
340 converts the voltages VX and VY converted by the time / voltage conversion circuits 200 and 330 into digital data. The count circuit 310 counts the count clock XC.

[0006] The data generation circuit 320 includes the digital data VX and VX converted by the A / D converters 210 and 340.
A desired measurement time TI is calculated and generated based on Y and the count signal of the count circuit 310. This data generation circuit 3
The measurement value data calculated and generated in 20 is stored in the acquisition memory 220.

[0007] The CPU 230 is connected to the acquisition memory 220 via a bus line.
Calculates statistical values from the measured value data stored in the display unit 2 or displays 2 connected via the same bus line.
It is responsible for outputting measured values and statistical calculation results to 40.

[0008] The D / A converter 250 is also connected to the acquisition memory 220 via a bus line, and converts a statistical operation result such as a standard deviation into an analog value and outputs the analog value to the meter 260.

The operation of such a configuration will be described with reference to the flowchart of FIG. Here, as an example, a time difference TI (Time Interval) from a rising edge of a signal input from the signal input terminal ChA and input to the fraction cutout logic circuit 190 to a rising edge of the signal input terminal ChB is measured. Think about doing.

The fraction cutout logic circuit 190 outputs a pulse from a rising edge of the input signal ChA to a rising edge of the reference clock immediately thereafter as a fraction pulse signal TX. On the other hand, for the input of the input signal ChB, similarly, a fraction pulse signal TY having a pulse width from immediately after the input of the rising edge to the rising edge of the reference clock is output.

At the same time, a reference clock up to the rising edge of the reference clock is output as a pulse train signal XC. Assuming that the cycle of the reference clock is To, the number of count pulses of the pulse train signal XC is N (N = 1 in FIG. 6), the pulse width of the fraction pulse signal TX is Tstart, and the pulse width of the fraction pulse signal TY is Tstop, The time difference TI between the measurement times can be obtained by the following equation.

TI = N * To + (Tstart−Tstop)

As described above, according to the present method, the fractional pulse signals TX and TY are converted into the voltages by converting the time pulse widths Tstart and Tstop of the fractional pulse signals TX and TY into voltages Vstart and Vstop. Pulse width Tstar
t and Tstop can be measured with high time resolution.

[0014]

However, since the time interval measuring device in the above-mentioned prior art assumes all signals as input signals, the time difference between the signal input terminals ChA and ChB is based on the reference clock. A function that can measure a very long time difference by using it, that is, a counter that counts a count clock XC and a circuit that outputs fractional pulse signals TX and TY and performs time / voltage conversion on each, but has a function If the time difference is limited to a certain value or less, there is a problem that a part of the digital counter and the time-to-voltage conversion circuit becomes a redundant circuit and cannot perform its original function.

Therefore, assuming an application of a read signal of an optical disk such as a DVD as an input signal, a time difference between the two signals is 40 ns at maximum as described above.
In the case of about (Mhz input frequency is about 25 Mhz), there is a problem to be solved to a circuit configuration that can omit redundant circuits.

[0016]

In order to solve the above-mentioned problems, a time interval measuring device according to the present invention is configured as follows.

(1) Means for converting each of the two signals into a digital signal, and from a rising edge of one of the converted digital signals to a rising edge of the other digital signal in accordance with a predetermined clock signal. A time interval measuring device including a means for generating a time difference between the two signals, and a means for converting the generated time difference into a voltage, wherein a maximum time difference between the two signals is limited to a predetermined value as the clock signal. A time interval measuring device characterized in that one of the two signals is substituted, provided that the signal is a signal. (2) The time according to claim 1, wherein the means for generating the time difference generates a time difference between a rising edge of one digital signal and a rising edge of the other digital signal from the rising edge. Interval measuring instrument. (3) The time interval measuring device according to claim 1, wherein the predetermined value of the maximum time difference is that the frequency of the input signal is around 25 Mhz and the time difference is around 40 ns. (4) A means for inputting two signals and converting each of them into a digital signal, and calculating a time width according to a clock signal immediately after a rising edge of one of the converted digital signals. A second time width calculating means for calculating a time width according to the clock signal immediately after the rising edge of the other digital signal;
A time / voltage converter for converting the time width generated by the first time width calculator and the second time width calculator into a voltage, wherein a minimum of the two signals is On the condition that the time difference is limited to a predetermined value, the first time width calculating means and the second time width calculating means
Wherein the time width calculating means calculates the time difference using the same circuit. (5) The time according to claim 4, wherein the predetermined value of the minimum time difference is determined at a minimum time interval at which the first and second time width measurements can be performed by the time width calculation means of the same circuit. Interval measuring instrument.

As described above, the circuit portions for calculating the time difference under a certain condition are made to overlap with each other.
It is possible to omit a reference clock for taking the timing of each signal, a circuit for counting the reference clock, and the like.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a time interval measuring device according to the present invention will be described with reference to the drawings.

As shown in FIG. 1, the time interval measuring device according to the first embodiment of the present invention has a circuit configuration for inputting two signals and measuring the time difference between the two signals. Signal input terminals ChA and ChB, buffer amplifiers 110 and 160 for amplifying the signals from the signal input terminals ChA and ChB, and a comparator 130 for converting the amplified input signal into a binary signal leaving only edge information. 180 and a D / A converter 12 for providing a binary trigger level to the comparators 130 and 180
When selecting an edge to be measured from 0, 170 and an input signal input from the signal input terminal ChA, a signal input from the signal input terminal ChB is used as a reference clock,
A fraction cutout logic circuit 190 that cuts out a fraction below the substitute signal to generate a fraction pulse signal TX;
A time / voltage (T / V) conversion circuit 200 for converting a fractional time of the fractional pulse signal TX into a voltage VX proportional to the pulse width, and a voltage VX converted by the time / voltage conversion circuit 200 into digital data. A / D converter 2
10, an acquisition memory 220 for storing measured value data created by the A / D converter 210,
A CPU 230 connected to the acquisition memory 220 via a bus line, for calculating a statistical value from the measured value data stored in the memory 220, and for outputting a measured value or a statistical calculation result to the display 240; Statistical calculation results such as standard deviation are converted into analog values and meter 2
And a D / A converter 250 for sending the signal to the D / A converter 60. Among them, the signal from the comparator 160 connected to the signal input terminal ChB is supplied to the clock generation circuit 15.
It is configured to be switched by a switch 140 that switches to 0 and input to the fraction cutout logic circuit 190.

In such a configuration, the signal input terminal C
The hB input signal is used as a reference clock for the fractional cut-out logic circuit 190, and the signal input terminal C
By limiting the frequency of the input signal to the signal input terminal ChB to, for example, 25 Mhz and the time difference between the signals to a maximum of 40 ns with respect to the signal input to the hA, the time / voltage (T / V)
The time difference can be measured within the operation range of the conversion circuit 200. Here, the switch 140 for switching between the clock generation circuit 150 and the input signal ChB is provided.
This is for valuing the time / voltage (T / V) conversion circuit 200, and the time / voltage (T / V) is calculated using a known clock in advance.
By knowing the variable coefficient of the conversion circuit 200, an unknown time difference can be measured.

The operation of the time interval measuring device having such a configuration will be described with reference to FIG. 1 and the flowchart shown in FIG.

From the rising edge of the signal input from the signal input terminal ChA and input to the fractional cut-out logic circuit 190, the signal input terminal Ch
Time difference TI (Time) until the rising edge of B
Interval).

The fraction extraction logic circuit 190 outputs a pulse until the rising edge of the signal at the signal input terminal ChB immediately after the rising edge of the input signal from the signal input terminal ChA enters, as a fraction pulse signal TX.

The pulse width of the fractional pulse signal TX is represented by T
Assuming start, Vstart, which is a voltage conversion output VX obtained by converting the pulse width Tstart into a voltage, can be obtained.
Therefore, the time difference TI between the measured times of the two signals from the signal input terminals ChA and ChB can be obtained by the following equation.

TI = Tstart

As described above, when measuring the time interval between two signals, one of the input signals, in the case of the embodiment, the signal on the signal input terminal ChB side is within a certain frequency range (minimum frequency 25 Mhz, maximum frequency 25 MHz). If the time difference is limited to 40 ns, it is possible to measure the time difference between the two signals (ChA and ChB) by using the signal as a clock even if the conventional measurement circuit is simplified. It becomes. Specifically, since the time / voltage conversion circuit 200 and the like that are made of discrete components can be omitted, the circuit scale can be reduced, for example, the circuit area required in the related art can be reduced to about two-thirds. It becomes possible to do.

Next, a time interval measuring device according to a second embodiment of the present invention will be described with reference to FIGS.

As shown in FIG. 3, the time interval measuring device according to the second embodiment of the present invention has a two-series circuit configuration for inputting two signals and measuring the time difference therebetween. Signal input terminals ChA, Ch for inputting the signals of
B; buffer amplifiers 110 and 160 for amplifying the signals from the signal input terminals ChA and ChB; comparators 130 and 180 for converting the amplified input signal into a binary signal that leaves only edge information;
D / A converters 120 and 170 for providing a binarization trigger level to the signal 180 and signal input terminals ChA and ChB
Time width calculating means and second time width calculating means for selecting an edge to be measured from the input signal inputted from the first section, cutting out a fraction below the reference clock to generate a fraction pulse signal TX, and a count clock XC A fractional cut-out logic circuit 190 for inputting a reference clock of the clock generation circuit 150 for generating the
A time / voltage (T / V) conversion circuit 200 which is a time / voltage conversion means for converting a fractional time of X into a voltage VX proportional to the pulse width, and a voltage VX converted by the time / voltage conversion circuit 200 An A / D converter 210 that converts the data into data; a data generation circuit 320 that calculates the desired measurement time T1 by counting the data of the voltage VX converted into digital data and the count signal from the counter circuit 310; Acquisition memory 220 for storing measured value data created by data generation circuit 320
And a CPU 230 connected to the acquisition memory 220 via a bus line and calculating a statistical value from the measured value data stored in the memory 220 and outputting the measured value and the statistical calculation result to the display 240. And a D / A converter 250 that converts a statistical calculation result such as a standard deviation into an analog value and sends the analog value to the meter 260. As described above, the first time width calculating means and the second time width calculating means are performed by one time calculating means, that is, the signals input from the signal input terminals ChA and ChB are both the same fraction pulse signal TX. And the circuit related to the fractional pulse signal TY (see FIG. 5 of the prior art) is omitted.

The operation of the measuring instrument having such a configuration will be described below with reference to FIG. 3 and a flowchart shown in FIG.

Here, similarly to the above-described embodiment, the time difference TI () from the rising edge of the signal input from the signal input terminal ChA and input to the fractional cut-out logic circuit 190 to the rising edge of the signal input terminal ChB is also used. Consider measuring (TimeInterval).

The fraction cutout logic circuit 190 outputs a pulse from a rising edge of the input signal ChA to a rising edge 3 of the reference clock immediately after the rising edge as the fraction pulse signal TX. On the other hand, the input signal ChB is similarly output as a fractional pulse signal TX having a pulse width from the time immediately after the rising edge is input to the time of the reference clock.

At the same time, the reference clocks up to are output as a pulse train signal XC. Assuming that the cycle of the reference clock is To, the count pulse number of the pulse train signal XC is N (N = 1 in FIG. 4), and the pulse width of the fractional pulse TX from the signal input terminal ChA is Tstar.
t, assuming that the pulse width of the fractional pulse TX from the signal input terminal ChB is Tstop, the time difference TI of the measured time can be obtained by the following equation.

TI = N * To + (Tstart−Tstop)

Thus, the signal input terminals ChA, C
hB from the two input signals into one fractional pulse signal TX
, The time widths Tstart and Tstop are generated, the voltages are converted into the voltages Vstart and Vstop corresponding to the time widths, and the voltage widths are A / D-converted to obtain the time difference TI.

[0036]

As described above, unlike a general-purpose time measuring instrument such as a time internal analyzer, in an application limited to an application with a limited maximum time difference,
By integrating redundant circuits for generating a time difference between the individual signals, for example, a time / voltage conversion circuit and a counter, there is an effect that the entire device can be simplified.

In addition, a circuit having a large circuit scale (area) composed of discrete component circuits such as a time / voltage conversion circuit, which is a circuit element, can be omitted, so that the circuit scale can be reduced. There is also an effect.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a time interval measuring device according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the time interval measuring device having the configuration shown in FIG.

FIG. 3 is a block diagram illustrating a configuration of a time interval measuring device according to a second embodiment of the present invention.

FIG. 4 is a flowchart showing the operation of the time interval measuring device having the configuration shown in FIG. 3;

FIG. 5 is a schematic block diagram of a time interval measuring device according to the prior art.

FIG. 6 is a flowchart showing the operation of the time interval measuring device having the configuration shown in FIG.

[Explanation of symbols]

110; buffer amplifier, 120; D / A converter,
130; comparator, 140; switch, 150; clock generation circuit, 160; buffer amplifier, 190; fractional cut-out logic circuit, 200; time / voltage (TV)
Conversion circuit, 210; A / D converter, 220; acquisition memory, 230; CPU, 240;
50; DA converter; 260; meter; 310; counter circuit

Claims (5)

[Claims] And means for converting each of the two signals into a digital signal and a rising edge of one of the converted digital signals and a rising edge of the other digital signal according to a predetermined clock signal. A time interval measuring device including means for generating a time difference and means for converting the generated time difference into a voltage, wherein the clock signal has a maximum time difference between the two signals limited to a predetermined value. A time interval measuring device, wherein one of the two signals is substituted on the condition that: 2. The apparatus according to claim 1, wherein said means for generating a time difference generates a time difference between a rising edge of one digital signal and a rising edge of the other digital signal from the rising edge. Time interval measuring instrument. 3. The predetermined value of the maximum time difference is such that the frequency of the input signal is about 25 MHz and the time difference is 40 ns.
2. The time interval measuring device according to claim 1, wherein the time interval measuring device is before and after. 4. A means for inputting two signals and converting each to a digital signal, and calculating a time width according to a clock signal immediately after a rising edge of one of the converted digital signals. First time width calculating means, second time width calculating means for calculating a time width according to the clock signal immediately after the rising edge of the other digital signal, the first time width calculating means and the second time A time interval measuring device including a time / voltage converting means for converting a time width generated by the width calculating means into a voltage, wherein a minimum time difference between the two signals is limited to a predetermined value. As a condition, the first time width calculating means and the second time width calculating means calculate a time difference using the same circuit. 5. The system according to claim 4, wherein the predetermined value of the minimum time difference is determined at a minimum time interval at which the first and second time width measurements can be performed by the time width calculation means of the same circuit. Time interval measuring instrument.