JPS61154477A - Repeating analog-to-digital converter - Google Patents

Abstract

PURPOSE:To convert analog quantity to digital in a minute sampling time, by method wherein the analog quantity is compared with successively different voltage, wherein the comparison results are arranged to be memorized, and wherein a comparator and a shift register are used for the purpose of the comparison and memory. CONSTITUTION:Ultrasonic signal g is compared with reference voltage Vref by a comparator 6. The reference voltage Vref is obtained by D/A-converting the reference voltage programmed in a microcomputer 1, with a D/A converter 5. The output of the comparator 6 is directed to a shift register 8-3 for input, and is successively shifted to shift registers 8-2, 8-1. When clock pulse to the shift registers 8-1-8-3 comes to a specified quantity, the contents of the shift registers 8-1-8-3 are read by the microcomputer 1. Said action takes place with each different reference value Vref.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a digital conversion device for a repetitive analog waveform, which converts an analog quantity, such as an ultrasonic waveform in which the same waveform appears repeatedly, into a digital quantity.

[Background of the invention]

A computer converts an input analog value into a digital value, stores the converted digital value in a memory, and retrieves it when necessary to use it for a required calculation. Generally, to convert an analog value into a digital value, a well-known A/D such as an integral type or a successive approximation type is used.
A converter is used. Hereinafter, a configuration using such five A/D converters will be explained with reference to FIG.

FIG. 4 is a block diagram of a microcomputer and its peripheral devices. In the figure, 1 is the CPU, ROM, RAM,
2 is an A/D converter, and 3 is a multiplexer that selects and outputs one of a plurality of input signals.

The multiplexer 3 receives various analog signals αl.

α2, α3, . . . α, are input. In order to select and input a predetermined signal from among these analog signals, the microcomputer 1 outputs a switching command signal S to the multiplexer 3, and the multiplexer 3 is switched according to this signal I to input the selected predetermined signal. An analog signal (this signal is represented by α) is output to the A/D converter 2. Next, the microcomputer 1 outputs a conversion command signal C1 to the A/D converter 2, and the A/D converter 2
In response to this signal, starts the operation of converting the analog signal α into the corresponding digital signal d. When the digital signal d is determined by the conversion operation, the A/D converter 2 sends a conversion completion signal C2 to the microcomputer 1.
Output. The microcomputer 1 reads the digital signal d converted from the A/D converter 2 in response to the signal C2, and stores it in a predetermined memory such as a RAM.

Figure 5 is a waveform diagram of the analog signal α, where the horizontal axis represents time T and the vertical axis represents voltage. The sampling period of the conversion is indicated by ΔT. And this sampling period Δ
T is determined by the conversion speed of the A/D converter 2 itself and the signal processing speed of the microcomputer 1, and cannot be further shortened to perform high-speed processing.

In contrast, five means have been studied in which the A/D converter 2 and the RAM are directly connected and A/D conversion is performed based on a basic clock signal. According to this means, since the converted data is directly recorded in the RAM without going through the CPU of the microcomputer 1, the sampling period ΔT can be significantly shortened.

However, even if such means are adopted, the conversion speed is determined by the conversion speed of the A/D converter 2 itself and the writing speed of the RAM, and even higher conversion speeds cannot be expected. The above A/D conversion means is uniformly adopted for analog signals, that is, continuous signals, discontinuous signals, regular signals, irregular signals, etc., and the special characteristics of analog and log signals are It wasn't considered at all. Therefore, in A/D conversion of any analog signal, the conversion speed cannot escape from the above-mentioned restrictions, resulting in a disadvantage that the sampling time becomes long and coarse sampling is inevitable. .

[Purpose of the invention]

An object of the present invention is to convert analog signals, especially analog signals having repetitive waveforms such as ultrasonic signals, into digital signals with a finer sampling time without being constrained by the above-mentioned restrictions. Our goal is to provide digital conversion equipment.

[Summary of the invention]

In order to achieve the above object, the present invention inputs an analog signal to be converted into a comparator, compares it with a certain reference value, and sequentially inputs the results of the comparison by the comparator into a shift register using a clock pulse. The present invention is characterized in that the contents of the shift register are read when the clock pulse reaches a predetermined number, and such means are performed for each other different reference value.

[Embodiments of the invention]

The present invention will be explained below based on the illustrated embodiments.

FIG. 1 is a block diagram of a digital conversion device according to an embodiment of the present invention. In the figure, 1 is a microcomputer, 5
6 is a D/A converter that converts a reference voltage programmed in the microcomputer 1 (this reference voltage will be described later) into an analog reference voltage rgf, and 6 has a reference voltage rJ at one terminal; Ultrasonic signal on the other terminal! This is a comparator that inputs and compares the two. The output signal of the comparator 6 is the ultrasonic signal da which is the reference voltage rgf.
or more, the high level becomes "1", and the reference voltage vr,
When it is less than f, it becomes a low level rOJ. 7 is an oscillation device driven by an oscillation command signal from the microcomputer 1; 8-1, 8-2, and 8-3 are output signals to the comparator 6;
are sequentially stored in a shift register.

Before explaining the operation of this embodiment, let us first explain the ultrasonic signal! The principle of this embodiment for digitally converting the ultrasonic signal 1 will be explained.

FIG. 2 is an example of a received ultrasound waveform diagram. In the figure, the horizontal axis represents time t, and the vertical axis represents voltage V. The emitted ultrasonic waves are reflected by objects, etc., and necessary judgments are made based on the echo pulses. Pl in the figure is the transmission pulse s Pl
+Pl are echo pulses, and these are the pulses that are valid for the above judgment. These echo pulses appear repeatedly with a period t'. The value of the magnitude of the largest transmission pulse Pl among these pulses is known.

FIG. 3 is an enlarged view of a part of the received waveform shown in FIG.
The operation of this embodiment will be explained with reference to this diagram.

Now, a certain voltage ■rtft is set as a reference voltage, and the received voltage is compared with the reference voltage vrgfi every sampling period Δ. This comparison is performed for an appropriate period within the repetition period iI of the received waves. In the next repetition period,
A similar comparison is made by setting the reference voltage to a voltage V that is lower than the previous reference voltage vrgfs. As shown in this gfz, the received waves are sequentially converted to the reference voltage ■rgfs~■A1
Compared with f5, if the received wave is equal to or higher than the reference voltage vrtf, it is "1", and if it is less than the reference voltage ■rgf, it is "1".
O”, the effective pulse P 1 * Pl
*It is possible to grasp the magnitude of the voltage of P3 and the generation time interval of the echo pulse P2 y Pl with respect to the transmission pulse P1. The results of the above comparisons for the waveforms shown in Figure 3 are summarized as shown in the following table. According to the above table,
At time t1, pulse P1 of voltage V□f2 is generated, and at time t
A pulse P2 of voltage vref4 is generated at i, and then K,
It can be determined that a pulse P3 of voltage vrtfs is generated at time t'. It is clear that by setting the intervals of each reference voltage V□f more precisely, a more accurate voltage of each pulse can be obtained. And each reference voltage V
□f.

Since the value is known from the beginning, when the comparison result is rlJ for the first time, the digital value of the 7th pulse is immediately obtained. In this embodiment, the above comparison and accumulation of the results of the comparison are performed using a comparator and a shift register that can operate at high speed and are inexpensive.

Here, the operation of this embodiment shown in FIG. 1 will be explained with reference to FIG. 3. First 1. The microcomputer 1 outputs the reference voltage ■rgfx as a digital signal,
The D/A converter 5 converts this into an analog signal and inputs it to the negative terminal of the comparator 6. At the same time, the microcomputer 1 activates the oscillation device 7 with an oscillation command signal, but the clock signal C is not output from the oscillation device 7. Now, when the received ultrasonic wave 1 is input to the positive terminal of the comparator 6, the comparator 6 immediately compares it with the reference voltage rafl. On the other hand, the signal Da is input to the oscillation device 7, and when the pulse Pl is input, the clock pulse C is output for the first time using this as a trigger signal. here,
In order to use the pulse P as a trigger signal, it is necessary to distinguish it from the echo pulse, but this distinction requires a comparator to compare the signal f with an appropriate setting value, since the pulse P1 is always much louder than the echo pulse. This is possible by providing it separately.

The output of clock pulse C causes the shift register to be shifted by one. As a result of comparing the pulse Pl with the reference voltage V□c in the comparator 6, the value of the pulse Pl is less than the reference voltage V, so the output signal gfi of the comparator 6 is rOJ, and the shift register 8-3 rOJ is stored in the first register of . The oscillation period of the clock pulse C is set to the above-mentioned sampling period Δt, so that the signal f changes to the reference voltage vraf every time Δ.
s and the results are sequentially transferred to shift register 8-
1 to 8-3.

The oscillator 7 is equipped with a counter (not shown) and counts the clock pulses C that are output. As described above, this counter is set with a number that defines a predetermined period within the repetition period t' of the signal 1.

Here, the predetermined period is determined by the product Δt-r of the sampling period Δt and the number t, and the time t in the above table corresponds to this. When the clock pulse C output from the oscillation device 7 reaches the number set in the counter, the oscillation device 7 outputs a counter overflow signal f to the computer 1. This signal fK
The output of the clock pulse C is then stopped. Note that, after the counter is cleared when the next transmission pulse Pl is input, a new count is immediately started. In this case, the means described above is used to distinguish between the transmission pulse P1 and the echo pulse. On the other hand, the microcomputer 1 inputs the signal f to shift registers 8-1 to 8-1.
Read all the values stored in 8-3 and send this to Ft
Store in AM etc. The values stored in the shift register at this time are all "0", as shown in the column of the reference voltage (2) above, efi.

The microcomputer 1 reads the value of the shift register as described above, and outputs a new reference voltage V to the D/A converter 5, and the D/At''gf2 converter 5 converts the analog value corresponding to this. Reference voltage ■re
f2 is given to the comparator 6. When the signal f inputted to the positive terminal of the comparator 6 enters the next repetition period, the pulse P is generated again.
A clock pulse C is output from the oscillation device from the IK, and the signal l is compared with the reference voltage Vref2. As shown in the column, the value "1000...0" is obtained.Such operation is continued until the comparison using the reference voltage Vrgfs and storage are completed.

In this way, in this embodiment, the received ultrasonic waves are sequentially compared with different reference voltages and the results are stored, and a comparator with a fast response speed and a shift register with a fast shift speed are used for this comparison and storage. Therefore, it is possible to digitally convert received ultrasonic waves with a finer sampling time than a normal A/D converter.

In the description of the above embodiments, the digital conversion of received ultrasonic waves has been described, but the present invention is not limited to this, and it is obvious that the present invention can be applied to conversion of analog quantities in which the same waveform appears repeatedly. Further, in the above embodiment, five reference voltages have been described, but these are used for convenience of explanation, and in reality, the resolution is improved by comparing with a large number of reference voltages.

〔Effect of the invention〕

As described above, in the present invention, analog quantities in which the same waveform appears repeatedly are compared with different reference voltages sequentially, and the comparison results are stored, and a comparator and a shift register are used for this comparison and storage. , the analog quantity can be converted into digital data with a finer sampling time.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a digital conversion device according to an embodiment of the present invention, FIGS. 2 and 3 are reception waveform diagrams of ultrasonic signals, FIG. 4 is a block diagram of a microcomputer and its peripheral devices, and FIG. The figure is a waveform diagram of an analog signal. 1...Microcomputer, 5...
D/A converter, 6... Comparator, 7...
Oscillator, 8-1゜8-2.8-3...shift register. Figure 1 Figure 2 Figure 3 Figure 8

Claims (1)

[Claims] a comparator that has a first input terminal for inputting an analog value and a second input terminal for inputting a reference value, and for comparing the analog value with the reference value; and a comparator for sequentially inputting different reference values to the second input terminal. A reference value setting means for outputting, a shift register for sequentially shifting the output of the comparator in response to a clock pulse, and a reading means for reading the contents of the shift register when the clock pulse reaches a predetermined number. A repeating analog waveform digital conversion device featuring