JP2011027621A - Clocking circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a clocking circuit which requires no additional clock generating part when both TAC method and clock count method are employed. <P>SOLUTION: The clocking circuit includes a peak detecting circuit (30) which detects a maximum amplitude of input signal and outputs a peak detection trigger, an analogue signal generating part (10) which generates and outputs the analogue signal in which, with the measurement start signal coming from outside as a start point, a voltage value rises in a predetermined pattern as time passes, a pulse generating part (60) which generates a pulse signal with constant interval by repeating such operation as monitoring a voltage value of analogue signal and zero-resetting the voltage value of analogue signal each time a predetermined voltage value is exceeded, time calculation process parts (20, 40, and 50) which calculate time duration until a peak detection trigger is output with the measurement start signal as start point based on the voltage value of analogue signal at such timing as the peak detection trigger is output as well as based on the counting result of pulse signal. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a time measurement circuit used for a pulse radar, a laser rangefinder, and the like, and more particularly to a time measurement circuit using both a TAC (Time to Amplitude Converter) method and a clock count method.

  When measuring a distance to a target with a radar system such as a conventional pulse radar, the TAC method is known as the first method. This TAC system irradiates a pulse from a pulse radar toward a target, and generates an analog signal whose amplitude increases with time. Then, the time is measured by obtaining the amount of change until the pulse reflected or scattered by the target returns to the radar.

  FIG. 5 is an exemplary diagram of an analog voltage generation circuit used in the conventional TAC method. This analog voltage generation circuit includes a current source 111, a capacitor 112, switches 113 and 114, and an output terminal 115. The switch 113 is connected in series between the current source 111 and the capacitor 112. On the other hand, the switch 114 is connected to the capacitor 112 in parallel.

  When the switch 113 is turned on and the switch 114 is turned off, electric charge is supplied from the current source 111 to the capacitor 112, and the voltage between the electrodes of the capacitor 112 increases. Here, when the current source 111 is a constant current source, since a charge is supplied at a constant rate with respect to time, a ramp voltage whose voltage increases at a constant rate with respect to time is output from the output terminal 115. Will be. In the TAC method, the elapsed time can be known from the output voltage.

  As a second method, a clock count method is known. In this clock count method, a pulse is emitted from a pulse radar toward a target, a clock signal is generated, and time is measured by counting the clock until the pulse is fed back by the radar.

  As a third method, a method is also known in which the time for each clock cycle is measured by the clock count method, and the time shorter than the clock cycle is measured by the TAC method. Thus, by using the clock count method and the TAC method in combination, it is possible to perform time measurement with high accuracy at a low cost (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 2000-227483

However, the prior art has the following problems.
FIG. 6 is a configuration diagram of a conventional time measuring circuit using both the TAC method and the clock count method. This time measurement circuit includes an analog signal generation unit 10, a pulse counter 20, a peak detection circuit 30, a calculation unit 40, a signal processing unit 50, an inverter 90, and a clock generation circuit 100. Moreover, the input terminals 1-4 and the output terminal 5 are provided as a terminal.

  In such a conventional time measuring circuit, using the clock pulse output from the clock generation circuit 100 and the inverter 90, the capacitor 16a and the capacitor 16b in the analog signal generator 10 are alternately switched, and the time equal to or shorter than the clock cycle is set. Measurement is performed by the analog signal generator 10. Further, the clock pulse is counted by the pulse counter 20 to measure the time for each clock cycle. And the signal processing part 50 calculates the distance to a target based on both measurement results.

  That is, the clock signal has two roles of controlling the analog signal generation unit 10 and serving as clock cycle distance information by counting with the pulse counter 20. In the case of a conventional circuit, as means for obtaining a clock signal, a means for separately providing a clock generation unit (corresponding to the clock generation circuit 100) or an external clock is taken. As a result, there is a problem that the circuit scale becomes large.

  The present invention has been made to solve the above-described problems. In a time measurement circuit using both the TAC method and the clock count method, it is not necessary to separately provide a clock generation unit or an external clock is provided. The purpose is to obtain an unnecessary time measuring circuit.

  The time measuring circuit according to the present invention detects the maximum value of the amplitude of the input signal and outputs a peak detection trigger, and the voltage value with time elapses from the external measurement start signal. An analog signal generator that generates and outputs an analog signal that rises in a predetermined pattern, and monitors the voltage value of the analog signal output from the analog signal generator, and zeros the voltage value of the analog signal every time the predetermined voltage value is exceeded By repeating the reset operation, a pulse generator that generates pulse signals at regular intervals, the voltage value of the analog signal output from the analog signal generator at the timing when the peak detection trigger is output from the peak detection circuit, and the pulse Based on the counting result of the pulse signal generated from the generator, the peak detection trigger is output starting from the measurement start signal. It is obtained by a time calculation processing unit for calculating a time to.

  According to the time measuring circuit of the present invention, an analog signal whose voltage value rises in a predetermined pattern is monitored, and a pulse signal at a constant interval is generated by repeating an operation of zero reset every time the predetermined voltage value is exceeded. Thus, in the time measuring circuit using both the TAC method and the clock counting method, it is possible to obtain a time measuring circuit that does not require a separate clock generator or does not require an external clock. it can.

It is a block diagram of the time measuring circuit in Embodiment 1 of this invention. It is a timing chart of the main signal waveform output from each part of the time measurement circuit in Embodiment 1 of this invention. It is a block diagram of the time measurement circuit in Embodiment 2 of this invention. It is a timing chart of the main signal waveform output from each part of the time measurement circuit in Embodiment 2 of this invention. It is an illustration figure of the analog voltage generation circuit used with the conventional TAC system. It is a block diagram of the conventional time measuring circuit which used the TAC system and the clock count system together.

  Hereinafter, preferred embodiments of a time measuring circuit of the present invention will be described with reference to the drawings.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram of a time measuring circuit according to the first embodiment of the present invention. The time measurement circuit according to the first embodiment includes an analog signal generation unit 10, a pulse counter 20, a peak detection circuit 30, a calculation unit 40, a signal processing unit 50, a comparator 60, and a reference voltage source 70. Yes. Further, input terminals 1 to 3 and an output terminal 5 are provided as terminals.

  Here, the analog signal generator 10 includes a current source 11, switches 13 to 15, and a capacitor 16. Further, in the analog signal generation unit 10, the electric charge is supplied from the current source 11 to the capacitor 16 only when the switch 13 controlled by the measurement start signal input from the input terminal 1 is turned on and the switches 14 and 15 are turned off. As a result, the voltage between the electrodes rises.

  The calculation unit 40 includes an S / H (sample and hold) circuit 41 and a latch 42. The S / H circuit 41 receives the peak detection trigger output by the peak detection circuit 30 at the maximum value of the input signal, and holds the output voltage of the analog signal generation unit 10 at that time. The latch 42 stores the count value of the pulse counter 20. The signal processing unit 50 obtains a distance from the output value of the S / H circuit 41 and the output value of the latch 42 and outputs the distance to the output terminal 5.

  Next, the operation of the time measuring circuit shown in FIG. 1 will be described. FIG. 2 is a timing chart of main signal waveforms output from each part of the time measuring circuit according to Embodiment 1 of the present invention. Here, it is assumed that the pulse radar is used as a time measurement circuit. At the same time as the pulse is transmitted from the pulse radar, the measurement start signal Vg input from the input terminal 1 changes from Low to High, and continues High for a predetermined time width (see FIG. 2B). ).

Further, before the measurement start signal is input, a reset signal is always input from the input terminal 2 (see FIG. 2A), the voltage between the electrodes of the capacitor 16 is made equal, and the count value of the pulse counter 20 is set. It shall be 0. The current source 11 is a constant current source, and the output of the analog signal generator 10 is a ramp voltage (V _L = at) whose voltage increases in proportion to time with a slope a (see FIG. 2C). The reference voltage source 70 has a voltage value V _c (ground voltage <V _c <power supply voltage), and the comparator 60 compares the lamp voltage V _L with the reference voltage V _c and performs the following operation. (See FIG. 2D).
When V _L ≤ V _c → Outputs Low When V _L > V _c → Outputs High

  As a result of the reset signal being input from the input terminal 2 and the switch 15 being turned on for a certain period of time, the voltage between the electrodes of the capacitor 16 becomes equal, and the comparator 60 outputs Low, so the switch 14 is turned off. . Further, the count value of the pulse counter becomes 0 with the input of the reset signal (see FIG. 2E).

At the same time as the pulse is transmitted from the pulse radar, the measurement start signal becomes High and the switch 13 is turned on. At the same time, the voltage between the electrodes of the capacitor 16 rises with a constant slope a with respect to time (FIG. 2 ( B) and (C)). After time V _c / a, the ramp voltage V _L becomes equal to the reference voltage V _c, and immediately after that, the comparator 60 outputs High (see FIG. 2D).

At this moment, the output of the pulse counter becomes 1 (see FIG. 2E), and the voltage between the electrodes of the capacitor 16 becomes the same value. As a result, the output of the comparator 60 becomes Low (FIG. 2D). reference). Thus, the comparator 60 repeats the operation of equalizing the voltage between the electrodes of the capacitor 16 at the moment when the ramp voltage V _L becomes higher than the reference voltage V _c , and outputs pulses at a constant interval ( (See FIG. 2D). On the other hand, the pulse counter 20 counts the number of times that the comparator 60 has output High (see FIG. 2E).

Now, the measurement start signal time becomes High in _{T1 (2V c / a <T1} <3V c / a) only the time, the pulse reflected from the target is fed back to the pulse radar, is input to the input terminal 3 (See FIG. 2F). In this case, the peak detection circuit 30 outputs a trigger at the maximum input value, and this trigger is input to the S / H circuit 41 and the latch 42 of the calculation unit 40. Since the S / H circuit 41 holds the output voltage of the analog signal generation unit 10 at the time when the trigger is input, the output voltage V1 of the S / H circuit 41 becomes a (T12−V _c / a) ( (See FIG. 2G). In the example shown in FIG. 2, the output of the latch 42 is 2 (see FIG. 2H).

The signal processing unit 50 solves the following equation from the output voltage of the S / H circuit 41 in the calculation unit 40 and the output value of the latch 42 to obtain a time T until the emitted pulse returns to the radar. The distance L from the radar to the target is calculated. Here, C is the speed of light.
T = ((Latch output × (V _c / a)) + S / H circuit 41 output voltage) / a
L = (C × T) / 2a

  In this way, it is possible to generate a signal having the same function as the clock signal by resetting the capacity in the analog signal generation unit 10 using the comparator 60 and counting the number of resets. Become. In the conventional circuit, it is necessary to provide a separate clock generation unit or to input an external clock signal. Such a clock generation unit is composed of circuits such as a vibrator, an oscillator, and a frequency divider. On the other hand, according to the present invention, by adding a single comparator to the analog signal generator, the same effect as the conventional one can be obtained, so that the circuit can be reduced in scale.

  As described above, according to the first embodiment, an analog signal whose voltage value rises in a predetermined pattern is monitored, and by repeating the operation of resetting to zero every time the predetermined voltage value is exceeded, a pulse signal at a constant interval is obtained. It is possible to generate a signal having the same function as the clock signal. As a result, the clock generation circuit becomes unnecessary, and the time measurement circuit can be reduced in size and price.

Embodiment 2. FIG.
FIG. 3 is a configuration diagram of a time measuring circuit according to the second embodiment of the present invention. The time measurement circuit of the second embodiment includes an analog signal generation unit 10, a pulse counter 20, a peak detection circuit 30, a calculation unit 40, a signal processing unit 50, two comparators 60a and 60b, a reference voltage source 70, and a calculation unit. 80 and an inverter 90. Further, input terminals 1 to 3 and an output terminal 5 are provided as terminals.

  Compared with the configuration of FIG. 1 in the first embodiment, the configuration of FIG. 3 in the second embodiment further includes an arithmetic unit 80 and an inverter 90, and includes two comparators. The internal configuration of the analog signal generator 10 is different. Therefore, the following description will focus on such a different configuration.

  The analog signal generation unit 10 according to the second embodiment includes a current source 11, switches 12, 13, 14a, 14b, 15a, 15b, and capacitors 16a, 16b. As described above, in the time measurement circuit according to the second embodiment, the two capacitors 16 a and 16 b are provided in the analog signal generation unit 10. The two capacitors 16 a and 16 b are switched and connected to the current source 11 via the switch 13 by switching the switch 12.

  Further, in the analog signal generator 10, the switch 12 is switched only when the switch 13 controlled by the measurement start signal input from the input terminal 1 is turned on and the switches 14a, 14b, 15a, and 15b are turned off. Accordingly, electric charge is supplied from the current source 11 to either the capacitor 16a or the capacitor 16b, and the voltage between the electrodes rises.

  The outputs of the capacitors 16a and 16b are connected to the comparators 60a and 60b, respectively. The outputs of the comparators 60a and 60b are connected to the calculation unit 80, and the voltage stored in the capacitors 16a and 16b is controlled by the output from the calculation unit 80. Here, the arithmetic unit 80 includes two 1-bit pulse counters 81 a and 81 and an exclusive OR element 82.

  FIG. 4 is a timing chart of main signal waveforms output from each part of the time measuring circuit according to the second embodiment of the present invention. Therefore, the operation of the time measuring circuit of FIG. 3 in the second embodiment will be described with reference to the timing chart of FIG.

At the same time as the pulse is transmitted from the pulse radar, the measurement start signal becomes High (see FIG. 4B), and at the same time as the switch 13 is turned on, the voltage between the electrodes of the capacitor 16a has a constant slope with respect to time. It rises at a (see FIG. 4C). Thereafter, the voltage between the electrodes of the capacitor 16a is a comparator 60a with reaches _{V c} and outputs a comparison trigger (see FIG. 4 (D)).

At that moment, the output of the 1-bit pulse counter 81a becomes “High” (see FIG. 4E), and the exclusive OR element 82 receives the High from the output “High” of the 1-bit pulse counter 81a and the output “Low” of the 1-bit pulse counter 81b. Is output. Since the output of the calculation unit 80 becomes High (see FIG. 4I), the switch 14a is turned on, the voltage between the electrodes of the capacitor 16a becomes equal, the switch 14b is turned off, and the electrode between the electrodes between the capacitors 16b is turned off. The voltage rises with a constant slope a with respect to time (see FIG. 4F). Comparator 60b with the voltage between the electrodes of the capacitor 16b reaches _{V c} and outputs a comparison trigger (see FIG. 4 (G)).

At that moment, the output of the 1-bit pulse counter 81b becomes High (see FIG. 4H), and the output of the exclusive OR element 82 also becomes Low. Since the output of the arithmetic unit 80 is Low (see FIG. 4 (I)), the switch 14b is turned on, the voltage between the electrodes of the capacitor 16b becomes equal, and the switch 14a is turned off, so that the electrode between the capacitors 16a. Increases at a constant slope a with respect to time (see FIG. 4C). In this way, the capacitors 16a and 16b are alternately charged and discharged, and the comparators 60a and 60b monitor the voltages of the connected capacitors 16a and 16b, respectively, and when they reach the preset voltage V _c , Reset the voltage between the electrodes.

  The calculation unit 80 performs an operation of generating a control signal for alternately switching the capacitance from the comparator output (see FIG. 4I). The operations of the peak detection circuit 30 and the calculation unit 40 after the pulse reflected from the target is returned to the pulse radar and the subsequent processing of the signal processing unit 50 are the same as those in FIG. 1 (FIG. 4 (J)). To (M)).

  By using the circuit configuration shown in FIGS. 3 and 4, it is possible to eliminate the influence of the discharge time when resetting the interelectrode voltage of the capacitor 16 in FIG. 1 in an actual circuit. For this reason, it is possible to prevent the measurement accuracy from being deteriorated immediately after resetting, and it becomes unnecessary to provide a separate clock generation unit or to input an external clock signal, so that the circuit can be reduced in scale.

  As described above, according to the second embodiment, an analog signal whose voltage value rises in a predetermined pattern is monitored, and by repeating the operation of resetting to zero every time the predetermined voltage value is exceeded, a pulse signal at a constant interval is obtained. Can be generated. As a result, as in the first embodiment, the clock generation circuit is unnecessary, and the time measurement circuit can be reduced in size and price.

  Further, in the second embodiment, two comparators and two capacitors are provided, and an arithmetic unit that generates a control signal for alternately switching the capacitors from the respective comparator outputs is provided. In other words, there are substantially two systems including an analog signal generator, a comparator, and a pulse counter, and each system can be operated alternately. As a result, as in the first embodiment, it is possible to eliminate the influence of the discharge time when resetting the interelectrode voltage of one capacitor, and it is possible to prevent deterioration in measurement accuracy immediately after resetting. .

  In the above-described embodiment, the case where the time measurement circuit of the present invention is incorporated in a pulse radar has been described. However, the time measuring circuit of the present invention is not limited to the pulse radar and can be used by being incorporated in an arbitrary electronic device such as another measuring device.

  In the above-described embodiment, the case where an analog signal that rises with time has been described as an example of a ramp voltage circuit using a current source and a capacitor as the analog signal generator. However, in order to output an analog signal that rises with time, a sine wave or a triangular wave can be used instead of the ramp waveform.

  1 to 3 input terminals, 5 output terminals, 10 analog signal generator, 11 current source, 12, 13, 14, 14a, 14b, 15, 15a, 15b switch, 16, 16a, 16b capacity, 20 pulse counter, 30 peak Detection circuit, 40 calculation unit, 41 sample and hold circuit, 42 latch, 50 signal processing unit, 60, 60a, 60b comparator (pulse generation unit), 70 reference voltage source, 80 calculation unit, 81a, 81b 1-bit pulse counter , 82 Exclusive OR element, 90 Inverter.

Claims (3)

A peak detection circuit that detects the maximum amplitude of the input signal and outputs a peak detection trigger;
An analog signal generator that generates and outputs an analog signal whose voltage value rises in a predetermined pattern as time elapses, starting from a measurement start signal from the outside,
By monitoring the voltage value of the analog signal output from the analog signal generator and repeating the operation of resetting the voltage value of the analog signal to zero every time a predetermined voltage value is exceeded, a pulse signal is generated at regular intervals. A pulse generator;
Based on the voltage value of the analog signal output from the analog signal generator at the timing when the peak detection trigger is output from the peak detection circuit, and the count result of the pulse signal generated from the pulse generator A time calculation processing unit for calculating a time until the peak detection trigger is output from the measurement start signal as a starting point. The time measurement circuit according to claim 1, wherein the time until the emitted pulse is reflected or scattered by the target and returned is measured and the distance to the target is measured.
The peak detector reads, as the input signal, a signal in which the emitted pulse is reflected or scattered by the target and returns, and detects a maximum value of the amplitude of the input signal, and outputs a peak detection trigger.
The analog signal generation unit uses the timing at which the pulse is emitted to the target as the measurement start signal, and generates and outputs an analog signal in which the voltage value rises in a predetermined pattern with time,
The pulse generator compares the voltage value of the analog signal output from the analog signal generator with the predetermined voltage value, and outputs a reset signal when the analog signal becomes larger than the predetermined voltage value. And a comparator configured to zero-reset the voltage value of the analog signal generated by the analog signal generator by the reset signal,
The time calculation processing unit
A pulse counter that clears the counter at the timing of firing the pulse to the target, and counts the number of reset signals output from the comparator;
Based on the voltage value of the analog signal output from the analog signal generation unit at the timing when the peak detection trigger is output from the peak detection circuit and the count value by the pulse counter, the emitted pulse is the target And a signal processing unit for calculating a time until it returns after being reflected or scattered by the time measurement circuit. The time measuring circuit according to claim 2,
2 systems comprising the analog signal generator, the comparator, and the pulse counter,
Based on the output from the comparator of each system, further comprising an arithmetic unit that controls the analog signal generation unit of each system to operate alternately,
The signal processing unit calculates a time until the emitted pulse is reflected or scattered by the target and returns based on signals alternately output from the two systems.

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