JPS6089897A - Sample-and-hold circuit - Google Patents

Abstract

PURPOSE:To suppress the effect of output ripple of a frequency voltage converter by producing a sampling pulse while using an input FM signal as a reference at each repetitive period of transmission start. CONSTITUTION:Monostable multivibrators 5, 6 are operated sequentially by a transmission trigger pulse and its Q output is fed to a DFF8. On the other hand, an input FM signal is given to a monostable multivibrator 7, its Q output is given to an AND gate 9 and a Q' output is given to an FF8 as a clock. A sampling pulse is produced by AND between the Q output of the FF8 and the Q output of the monostable multivibrator 7. Moreover, an input FM signal is fed to a sample-and-hold circuit 10 via a frequency voltage converter 4 and sampled and held by a sampling pulse from the gate 9. As a result, a value of a prescribed position of a ripple waveform of the input signal is sampled and the effect of ripple is reduced.

Description

[Detailed Description of the Invention] (Technical Field) The present invention is applicable to a sample to be measured by frequency converting an analog measure such as water temperature, water pressure, salinity concentration, etc., and further performing frequency voltage conversion. This relates to a hold circuit.

(Background Art) In the measurement of various data in science and technology, especially the measurement of data related to natural phenomena, it is often difficult to analyze and perform multiple processing on the data obtained at the measurement point.

Examples of such methods include the measurement of air temperature and atmospheric pressure in the sky, and the measurement of water temperature, water pressure, and salinity in the ocean. In such a case, it becomes necessary to place only the sensor and its associated circuitry at the measurement point and transmit the obtained data to a remote location.

However, it is impossible to transmit measured data to a remote location in a form that can be viewed up close, so in many cases it is converted into electrical signals in various forms before being transmitted.

The present invention was also made based on one such example. In other words, a wave height meter transducer installed on the ocean floor is equipped with sensors that measure water temperature, water pressure, salinity, etc., and the obtained data is transmitted to land via a submarine cable for the wave height meter. A method of analysis and processing is used.

(Conventional technology and problems) Conventionally used technology modulates the frequency of the transmission AC signal using data such as water temperature, water pressure, salinity concentration, etc., converts it into an FM signal, and transmits it on the same cable that transmits the wave height data. However, on land, a method is used in which this signal is applied to a frequency-voltage converter and extracted as a voltage signal.

FIG. 1 is a diagram showing operating waveforms of main parts in the prior art. Figure (a) shows a transmission pulse waveform that is repeated at a constant period. On the other hand, continuous FM signals are emitted from sensors that measure water temperature, water pressure, salinity, etc., but the output signal of the sensor itself is Immediately after the transmission pulse, however, both the frequency and amplitude temporarily drop to a low level, and then gradually recover and begin to send out normal signals. For this reason, when we amplify the signal that has passed through the transmission cable, Figure 1 (b)
The waveform looks like this. In order to apply this signal to a frequency-to-voltage converter, as a preprocessing step, the signal is shaped into a rectangular wave as shown in FIG. 1(c) using a high gain saturation amplifier.

When the signal shown in (e) of the same figure is input to a frequency-voltage converter, an output signal as shown in (d) of the same figure is obtained. The amplitude of this signal changes as the frequency of the input signal changes. Therefore, by measuring this voltage, it will once drop to a low level due to the influence of the transmitted pulse, and then gradually recover and stabilize at a predetermined value. Therefore, it is necessary to measure the voltage value when it is sufficiently stable. Furthermore, if the wave height data appears in the time range shown by t in FIG. 1(a), voltage measurement in the time range t must be avoided since the signals are transmitted through the same cable. For this reason, the voltage shown in FIG. 1(d) is delayed from the transmission pulse by a certain period of time that does not fall within the time range t and the voltage shown in FIG. 1(d) is stable.
The voltage is measured by sampling the voltage using a sampling pulse such as e).

However, in the voltage waveform of FIG. 1(d), there is a residual ripple due to the frequency component of the waveform of FIG. 1(e) that could not be completely smoothed by the frequency-voltage converter. Since this ripple matches the frequency component and phase of the FM signal in each cycle shown in FIG. 2(e), if the frequency and phase of the FM signal change, the frequency and phase of the ripple also change. On the other hand, since the timing of the sampling pulse is delayed by a certain period of time from the transmitted pulse regardless of the frequency and phase in Figure 1 (C), if the voltage waveform in Figure 1 ((1)) is sampled with such a sampling pulse, The voltage at different points of the ripple waveform is sampled each time it is repeated.This relationship is illustrated in Figure 1(e) and (f).Figure 1(f) is This is an enlarged view of the ripple waveform at the sample point of the waveform in Figure 1(d), both in amplitude and time axis.As is clear from Figure 1(f), the sampling position differs each time it is repeated. Therefore, there is a drawback that the sampled and held voltage value also contains ripples.

Of course, if we only focused on reducing this ripple, we could insert a low-pass filter with a low cut-off frequency at the output end of the frequency-voltage converter to further smooth it out.
Since the time constant of the circuit becomes large and it is no longer able to fully respond to the temporal changes in the original signal, there is a need for a means to minimize the influence of ripples without using such a filter. OBJECTS OF THE INVENTION In view of the above-mentioned drawbacks of the prior art, the present invention aims to improve the output voltage of a frequency-to-voltage converter without using a low-pass filter, which is responsible for the degradation of the time response to the original signal. (Configuration of the Invention) In order to achieve the above object, the present invention has the following configuration. That is, a change in the analog quantity of the object to be measured is extracted as an AC signal whose frequency changes according to the change, and the signal is converted into a frequency signal.

In addition to the pressure transducer, there is a circuit that converts the voltage into a voltage, converts the value into a sampling pulse with a period of a certain range, and generates a sampling pulse using the AC signal as a reference for each period. The sample bold circuit has a sampling pulse in which the temporal position of the sampling pulse coincides with a specific position of the phase of the alternating current signal every cycle.

(Example of the invention) Hereinafter, the present invention will be described in detail based on the drawings.

FIG. 2 is a block diagram showing the configuration of an embodiment of the present invention.

1 is the input terminal for the transmitted FM signal, 2 is the amplifier,
3 waveform shaping transistors, 4 is a frequency voltage converter,
5 is the first monostable multivibrator, 6 is the second monostable multivibrator, 7 is the third monostable multivibrator, 8 is the D-type flip-flop circuit, 9 is the AND circuit, and 10 is the sampling hole of Agyi. )' circuit, 11 is an output terminal, and 12 is a transmission activation trigger input terminal.

FIG. 3 shows waveforms of each part of the block diagram of FIG. 2. Figure 3(a) shows the transmission-activation trigger;
b) shows the waveform in which the FM signal input to input terminal 1 is amplified by amplifier 2, is shaped by transistor 3, and appears at the collector of the transistor, and (e) shows the time axis of the waveform in part (b) of the same figure. This is an enlarged waveform.

Below, the waveforms up to (j) in the same figure show the waveforms when enlarged.

First, connect the transmission start trigger input terminal shown in Fig. 3 (a) to the transmission start trigger input terminal in Fig. 2.
) is input, the first monostable multipipe rake 5 operates, and its terminal Q receives the signal shown in Fig. 3(d).
Outputs a voltage waveform like this.

The width T of the waveform is set so as to correspond to a time in which the output voltage of the frequency-to-voltage converter is free from the influence of the transmission pulse and is sufficiently stable and does not fall within the time range of pulse height data transmission. This output signal is applied to the second monostable multivibrator 6. The multivibrator 6
is activated by the falling edge of the waveform shown in FIG. 3(d) and outputs a signal having a waveform as shown in FIG. 3(e), which is applied to the terminal of the D-type flip 70 tube circuit. On the other hand, Fig. 3(c)
A signal having a waveform of is applied to the third monostable multivibrator 7. The multivibrator is activated by the rising edge of the waveform shown in FIG. 3(e), and the terminal Q receives a signal with the waveform shown in FIG. 3
A signal with a waveform as shown in figure (g) is output. And Figure 3 (
The signal g) is applied to the clock (CLK) terminal of the D-type flip-flop circuit 8. As a result, the D-type flip 70 tube circuit 8 loses the waveform shown in FIG. 3(e) due to the rise of the waveform shown in FIG. ) is obtained. When this output and the waveform of FIG. 3(f) are added to the AND circuit 9 and inverted, a pulse as shown in FIG. 3(1) is obtained. .

Then, the sampling pulse of FIG. 3(i) was applied to the sampling and hold circuit 10 of the Aoki, while the output of the transistor 3 was applied to the frequency-to-voltage converter 4 through the capacitor, and the change in frequency was converted into a change in voltage. After that, the output is sampled and held using the sampling and holding process. Now, if we consider the timing position of the sampling pulse shown in Figure 3(i),
Since they are generated based on the FM signal waveform in Figure 3(C), the timing relationship between the waveform in Figure 3(e) and the pulse waveform in Figure 3(i) is the same. I can see that there is.

The frequency and phase of the residual ripple in the output voltage waveform of the frequency-voltage converter 4 are also caused by the AC signal shown in FIG. 3(e), so they have the same relationship.

Therefore, with a sampling method as shown in Figure 3(i),
The output voltage of the frequency-voltage converter 4 having residual ripple as shown in FIG. 3(j) is measured by the sampling circuit 1.
When sampling at 0, the value at a fixed location of the ripple waveform is sampled. That is, even if the frequency of the FM input signal to the frequency-voltage converter 4 as shown in FIG. 3(j) and the pulse in FIG. 3(i), there is a time difference between the pulse in FIG. 3(1)'' and the ripple waveform in FIG. 3(j). This means that no relative change in phase or phase occurs.Thus, when a pulse that is simply synchronized with the transmission activation trigger and delayed by a certain period of time is used as a sampling pulse as in the conventional case, fluctuations in the sampled voltage do not occur. It can be seen that the amount decreases.

(Effects of the Invention) As explained above, in the present invention, sampling pulses are generated based on the input FM signal at each repetition period of transmission activation, so that the output of the frequency-voltage converter remains There is an advantage that the sampling point on the ripple waveform does not fluctuate uncertainly, and fluctuations in the output voltage can be suppressed without using a filter.

For example, when a signal with a frequency of 5 KHz is frequency-voltage converted, a ripple of approximately 30 mVpp will occur for an output of 2 V, but if this is extracted through a conventional sample and hold circuit, a maximum of approximately 30 mV of random fluctuation will remain. According to the sample-and-hold circuit of the present invention, the voltage can be suppressed to 3 mV pp D).

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of waveforms in a conventional y° sample hold circuit, Fig. 2 is a block diagram showing the circuit configuration of one embodiment of the present invention, and Fig. 3 is a signal waveform of each part in the embodiment of Fig. 2. This is a diagram showing 0 1...FM signal input terminal, 2...
......Amplifier, 3...... Waveform shaping transistor, 4... Frequency voltage converter, 5
・・・・・・・・・First monostable Martin case. , 6...... second monostable Martino (
Ibrator, 7...Third monostable Martino (Ibrator, 8...D-type flip-flop circuit, 9...An agent Patent Attorney Hiroshi Hachiman Figure 3

Claims (1)

[Claims] The change in the analog quantity of the object to be measured is extracted as an AC signal whose frequency changes according to the change, and the signal is applied to a frequency-voltage converter to convert it to voltage, and the value is converted into a sampling pulse with a period within a certain range. The sample hold circuit includes a circuit that generates a sampling pulse based on the alternating current signal every cycle, and the temporal position of the sampling pulse specifies the phase of the alternating current signal every cycle. A sample-and-hold circuit characterized by being consistent with the position.