JPH05175846A - Digitizing circuit - Google Patents

Abstract

PURPOSE:To easily detect the peak level of an input signal and to digitize the signal by detecting the amplitude of the input signal at plural levels and generating plural pulse sequences based on the detected levels. CONSTITUTION:A correlative output signal is transmitted to the minus terminals of respective comparators C1-Cn, the level of the correlative output signal is compared with the levels of respective reference voltages Vr1-Vrn at all times, and a comparator output is outputted from the comparator for which the level higher than the respective reference voltages is inputted. Next, since a correlative output waveform is a triangular wave and respective digital signals are not started at the same time, the waveforms of digital signals are extended by monostable multivibrators M1-Mn so as to be sampled by a clock CL. Next, the width of the digital signals is equalized by a latch L so as to easily operate an encoder E. Finally, the signal is converted to any binary number by the encoder E. Thus, the peak of the impulse signal like the triangular wave is caught and can be held for a long time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a digitizing circuit for converting an input signal having a desired time width such as a correlation peak output from a convolver into a digital signal.

[0002]

2. Description of the Related Art Conventionally, as a method for converting a correlation peak output from a convolver into a digital signal, A / D
There are a conversion method, a comparator method, and a peak hold method, and the correlation peaks are binarized by these methods and converted into digital signals.

The A / D conversion method is as shown in FIG.
This is a method of sampling the correlation peak (a) using the converter 1 to obtain a binarized digital signal (b).
As shown in FIG. 6, the comparator system uses a comparator 2 to compare the correlation peak (a) with the threshold voltage V _R to binarize the digital signal (b).
Is a method of obtaining. Furthermore, the peak hold circuit system is shown in Fig. 7.
As shown in FIG. 3, a peak hold circuit 3 including buffer amplifiers BA ₁ and BA ₂ and a capacitor C is used to hold the correlation peak (a) to obtain a binarized digital signal (b).

[0004]

However, in the correlation using the convolver, since the correlation output waveform becomes a sharp triangular wave, for example, when the A / D conversion method is used, in order to catch the peak of the triangular wave, The frequency of the sampling clock for A / D conversion must be increased considerably. This is because when the frequency of the sampling clock is low, that is, when the sampling interval is long, there is a high possibility that a steep triangular wave peak cannot be captured. For example, if the triangular wave has a width of t and a height of h and is sampled at a time of t / 2, the sampling pulse may be synchronized with the peak as shown by the triangular wave 4 in FIG. In this case, since the peak of the correlation output and the sampling pulse are synchronized, the peak can be surely grasped.) Usually, it is quite difficult to do such a thing. Therefore, the sampling of the triangular wave is performed asynchronously. Then, as shown by the triangular wave 1 in FIG.
A height of h2 is obtained. The higher the obtained height h
_H , that is, the range of h2 is between h / 2 ≦ h _H ≦ h, and the average height is h _H = 3h / 4, which is h / 4 from the actual height.
It becomes so low.

For example, in the triangular wave 1 of FIG. 8, the width of the triangular wave is t and the pulse width of the sampling pulse is t / 2.
In the case of, if the rising and falling parts of the triangular wave are linear, h1 = h2 (= h /
2), and hH that is the minimum value of h _H becomes maximum when the peak of the correlation output and the sampling pulse are synchronized as in the triangular wave 4. The range of h _H is h / 2
Since ≦ h _H ≦ h, therefore the average value of h _H is (under the condition that the rising and falling parts of the triangular wave are linear).
(H + h / 2) × 1/2 = 3 / 4h.

In the method of binarizing the A / D converted output, it is converted into a binary signal by comparing with digital data whose bit is shifted by 1 bit. As illustrated, in the relationship of the sampling pulse period t / 2 with respect to the width t of the triangular wave, the height h of the triangular wave corresponding to the average value of the level of the triangular wave is 3/4.
It is necessary to grasp as accurately as possible, but it cannot be said that the average value is reduced to 3/4.

As described above, in the case of A / D conversion as a method for detecting the peak of a triangular wave, the signal must be sampled and the comparator must be used in order to detect the peak because of the structure. Therefore, high-speed sampling must be performed. However, no matter how the speed is increased, the average value of the triangular wave level is unavoidably lowered. Further, in the case of the binarization processing using the comparator method, when the correlation output fluctuates, it is necessary to follow the fluctuation and change the threshold value.

For example, if there is a triangular wave whose level has fluctuated as shown in FIG. 6, and this is converted by a comparator having a fixed threshold value s, the triangular waves 1, 2 and 3 are binarized, but the triangular wave 3 is Since the level is lower than the threshold, it is not converted into binary. Therefore, in order to avoid this, it is necessary to change the threshold value in accordance with the fluctuation or eliminate the fluctuation of the triangular wave (the AGC circuit is required).

As another method, there is a peak hold circuit method using an analog method. However, with this method, the triangular voltage is sharp and the capacitor cannot be charged with the peak voltage. Furthermore, since the triangular wave generation time interval is long, leakage from the capacitor occurs, so that it cannot be held for a long time.

An object of the present invention is to detect a peak level of an input signal such as a correlation peak of a convolver output without being influenced by a sampling clock as in the A / D conversion method, and to easily detect and convert it into a digital signal. It is to provide a digitizing circuit.

[0011]

In order to achieve the above object, the digitizing circuit of the present invention comprises a detecting means for detecting the amplitude of an input signal having a predetermined time width at a plurality of desired levels, and the detecting means. Based on the level detected by
The gist of the present invention is to have pulse generation means for generating a plurality of pulse trains and conversion means for converting the pulse trains generated by the pulse generation means into digital signals.
In a preferred embodiment of the present invention, the detecting means is a plurality of comparator circuits each having a different threshold value. Further, the pulse generating means is a mono-multi circuit that generates a pulse based on each output of the comparator circuit. Furthermore, the conversion means is an encoder that converts the output of the mono-multi circuit into a binary number.

[0012]

In the digitizing circuit of the present invention, the amplitude of an input signal such as a correlation peak is detected at a plurality of desired levels, and a plurality of pulse trains are generated based on the detected levels. These pulse trains are converted into digital signals such as binary numbers.

[0013]

Embodiments of the present invention shown in the drawings will be described below.
FIG. 1 shows an embodiment of a digitizing circuit according to the present invention.
_{1 to} R _n are dividing resistors, C _{1 to} C _n are comparators, and M _{1 to} M _n
Is a mono-multivibrator circuit, L is a latch circuit, and E is an encoder circuit.

[0014] The (+) terminal of the comparator C ₁ -C _n split resistor R ₁ to R _n reference voltage Vr ₁ through Vr _n set in is applied, and each (-) to the terminal input signal V _IN is applied. Further, a predetermined clock CL is given to the latch circuit L and each of the mono multivibrator circuits M _{1 to} M _n .

[0015] In n = 4, if the resistance value of each divided resistors and R, the reference voltage Vr of the comparator C ₁ ~C _{4 1} ~Vr ₄
Are set by dividing into four, that is, Vr ₁ = V Vr ₂ = V · 3R / 4R = 3 / 4V Vr ₃ = V / 2 Vr ₄ = V / 4. In this example, the same resistance value R
Although it is linearly divided into four parts by using, the processing such as consciously changing the resistance value to raise the resolution accuracy in an arbitrary range of the level of the triangular wave can be freely performed by the simple operation of selecting the resistance value. .. Further, the number of divisions of the FEL amplitude level of the input signal is not limited to four divisions, and may be arbitrarily set as necessary.

[0016] In the embodiment, first correlation output signal (triangular wave) of the comparators C ₁ -C ₄ (-) is sent to the terminal. The correlation output signal and each reference voltage Vr _{1 to} Vr ₄ are constantly compared in level by the comparators C _{1 to} C ₄ (see FIG. 2).
(A)), Comparator outputs CO _{1 to} CO ₄ are output from the comparator to which a level higher than each reference voltage is input (FIG. 2 (b)). The details of FIGS. 2A and 2B are shown in FIG.

Next, since the start of each digital signal is not the same because the correlation output waveform is a triangular wave, the waveforms of the digital signals are stretched by the mono-multivibrators M _{1 to} M ₄ so that they can be sampled at the clock CL. Further, at this time, since the waveform data between the triangular waves is not needed, the waveform is stretched for a time slightly shorter than the time length of this triangular wave and the next triangular wave (FIG. 2).
(C)).

The time between the triangular waves of the correlation output is set in advance, and the time that does not exceed that time (if it exceeds the time, the next start timing comes before resetting during mono-multi operation. You can set the clock of the mono multivibrator. The mono-multivibrators M _{1 to} M ₄ are operated by using the rising edge of the output of the comparator as a trigger. As described above, the clock tc of the mono-multivibrator is set to a predetermined value smaller than the interval T between the triangular waves as shown in FIG. 4, and most of the time between the triangular waves is during the operating period of the mono-multivibrator. By operating in this way, as shown in FIG.
As is clear from (b) and (c), it becomes possible to grasp a pulse group having a narrow width as a pulse stretched as long as possible, and it is possible to stabilize the operation.

That is, since the comparator output is a pulse having a narrow width, it may not be detected due to the influence of fading or the like, but the waveform as shown in FIG. 2C (finally (d)). By doing so, the possibility that such a thing will occur can be reduced. Further, it is possible to grasp the phenomenon of the triangular wave peak, which has a very short duration, by replacing it with the stable phenomenon of the output of the mono-multi, and it is possible to prevent malfunction.

Next, in order to make the encoder easier to operate, the width of the digital signal is made uniform by the latch (see FIG. 2).
(D)). The binarization of the data is performed based on the length of the output waveform of the monomulti, and there is no problem in aligning the start ends with the latch. Finally, it is converted into a binary number by the encoder. In this way, the peak of an impulse-like signal such as a triangular wave can be captured and held for a long time.

[0021]

As described above, according to the digitizing circuit of the present invention, the peak level of the input signal such as the correlation peak can be easily and accurately detected without being influenced by the sampling clock and the like as in the conventional method. It is possible to reduce the amount of data to be processed by masking unnecessary data such as between the triangular waves of the above correlation peak.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a time chart for explaining the operation of the above embodiment.

FIG. 3 is a detailed waveform diagram of FIGS. 2 (a) and 2 (b).

FIG. 4 is a time chart for explaining the operation of the embodiment.

FIG. 5 is an explanatory diagram of a conventional A / D conversion method.

FIG. 6 is an explanatory diagram of a conventional comparator system.

FIG. 7 is an explanatory diagram of a conventional peak hold circuit system.

FIG. 8 is a waveform diagram for explaining the operation of the A / D conversion method.

FIG. 9 is a waveform diagram showing details of the triangular wave in FIG.

[Explanation of symbols]

R _{1 to} R _n division resistance C _{1 to} R _n comparator L latch circuit E encoder

Claims (4)

[Claims] 1. A detection means for detecting an amplitude of an input signal having a predetermined time width at a plurality of desired levels, and a pulse generation means for generating a plurality of pulse trains based on the levels detected by the detection means. A digitizing circuit comprising: a converting means for converting the pulse train generated by the pulse generating means into a digital signal; 2. The detection means is a plurality of comparator circuits each having a different threshold value.
The digitizing circuit according to. 3. The digitizing circuit according to claim 2, wherein the pulse generating means is a mono-multi circuit that generates a pulse based on each output of the comparator circuit. 4. The digitizing circuit according to claim 3, wherein the converting means is an encoder that converts the output of the mono-multi circuit into a binary number.