JPH02238707A - Signal processing unit - Google Patents

Abstract

PURPOSE:To keep the matching between an input waveform and an output waveform by forming a sampling signal whose period varies automatically with a change in the fundamental frequency of an input signal and using the sampling signal to apply sampling whose sampling number is set in each sampling period. CONSTITUTION:A fundamental pulse L synchronously with the period of a fundamental frequency of an input signal K is generated and a sampling signal M synchronously with a multiple of N of the fundamental frequency in response to the set sampling number N is generated within the period of the fundamental pulse L. Then upon the receipt of the sampling signal M and the fundamental pulse L, a trigger signal generating circuit 11 outputs a trigger signal P. As a result, an A/D converter 2, a processing section 14, and a D/A converter 13 are operated and an analog output signal Q is sent from the D/A converter 15. Thus, the matching of the phase and the waveform between the input signal K and the output signal Q is maintained.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention is a method of A/D converting a repeatedly fluctuating input signal, passing it through a processing device main body, and then D/A converting it and outputting it. The present invention relates to a signal processing device.

(Prior Art) In some types of devices, input signals that fluctuate repeatedly are processed by A/D.
Some signal processing devices require a signal processing device that converts the signal into a digital signal using a converter, passes it through the processing device main body, converts the signal that has passed through the processing device main body into an analog signal using a D/A converter, and outputs the analog signal.

A typical example of such a device is a rotating machine noise muffling device that artificially suppresses rotating machine noise at a certain location. The sound generated by a rotating machine repeatedly fluctuates at a frequency that is an integral multiple of the number of rotations. A four-turn machine sound muffling device usually has a microphone placed near the rotating machine that is the source of the noise, and a speaker placed near the point to be silenced.

Then, the rotating machine sound signal obtained by the microphone is converted into an A/D
After converting into a digital signal with a converter, frequency analysis is performed with a Fourier transformer, each frequency component signal is multiplied by a necessary coefficient, this is returned to an analog signal with a D/A converter, and this analog signal is converted into a speaker input signal. I try to give it as such.

By the way, in such a rotating machine sound muffling device, generally,
The sampling signal used in the A/D converter is used as it is as the clock signal for the D/A converter. Then, the period of the sampling signal, that is, the sampling time, is set to a constant value Δt derived from the sampling theorem that takes into account the variation width of the fundamental frequency of the input signal.

However, such a rotating machine noise muffling device, that is, a conventional signal processing device that performs A/D conversion on a repeatedly fluctuating input signal and then performs D/A conversion and outputs the resultant signal has the following problems. In other words, if the fundamental frequency of the input signal is approximately constant, this is not a big problem, but if the fundamental frequency fluctuates, the consistency between the input signal waveform and the output signal waveform will be lost, and good control may not be possible. It may disappear.

FIG. 3 illustrates this phenomenon using a rotating machine noise muffling device as an example. A conventional rotary machine noise muffling device generates a trigger signal (b) synchronized with the period of the fundamental frequency component of an input signal (a). Then, a constant period sampling signal (
c) is used to sample the input signal, and the samples obtained between the trigger signals are A/D converted (d) in real time and captured. Now, as shown in the figure, the trigger signals are n, n+l,
Assuming n+2, . . . , digital data taken in period n is Fourier transformed into period n+1, and each frequency component is multiplied by a necessary coefficient. That is, signal processing (e) is performed. Subsequently, the processed digital data is D/A in a period n+2 using the sampling signal (c) as a clock signal.
The data is converted (f) and output as analog data (g).

As can be seen from the waveform shown in Figure 3, there is no problem when the fundamental frequency of the input signal (a) is constant, but for example n+1
When the fundamental frequency changes, such as between the period 1 and the period n+2, the output (g) has a waveform completely different from the waveform of the input signal. Therefore, good muffling of rotating machine noise cannot be expected. In addition, in order to Fourier transform the A/D converted signal and perform frequency analysis, it is necessary to
), but in conventional devices, the period of the trigger signal (b) and the sampling signal are not synchronized. Therefore, the input signal is extracted discontinuously, and if Fourier transform is performed as it is, a leakage error will occur in the processing result. To prevent this, conventional devices perform window processing. However, there is a problem in that the data indicating the obtained energy must be corrected in consideration of calculation errors, and this processing requires a long calculation time.

(Problems to be Solved by the Invention) As mentioned above, in the conventional signal processing device of this type,
Not only may the waveform of the input signal and the waveform of the output signal not be consistent, but also special processing such as window processing is required in the process from A/D conversion to D/A conversion.
Moreover, there was a problem in that the processing required a long time.

Therefore, the present invention has a function to create a sampling signal whose period automatically changes in response to changes in the fundamental frequency of the input signal, and uses this sampling signal to sample a set number of samples within each sampling period. It is an object of the present invention to provide a signal processing device that can accurately perform processing, thereby solving the above-mentioned problems.

[Structure of the Invention] (Means for Solving the Problem) In order to achieve the above object, the signal processing device according to the present invention detects the fundamental frequency of an input signal that repeatedly fluctuates, and synchronizes with the period of the fundamental frequency. A basic pulse generating means for generating a basic pulse obtained by this means, and a continuous sampling signal that is N times the basic frequency and synchronized with the set number of samples N within the period of the basic pulse obtained by this means. and a sampling signal generating means for generating a sample signal.

(Function) When the fundamental frequency of the input signal changes, the period of the fundamental pulse changes, and the period of the sampled signal also changes in response to this change. Therefore, within the period of the basic pulse, sampling is always performed at a period of 1/N of the period of the basic pulse. Therefore, A/D conversion data of an input signal obtained within a certain basic pulse period is processed within the next basic pulse period, and this is further D/A converted using the above-mentioned sampling signal within the next basic pulse period. The waveform of the analog signal obtained by conversion is consistent with the waveform of the input signal. In addition, since the sampling signal can be generated in synchronization with the period of the fundamental pulse, the input signal can be continuously extracted and the A/
D conversion can be performed, and accurate frequency analysis, for example, can be performed without the need for window processing or the like.

(Example) Examples will be described below with reference to the drawings.

FIG. 1 shows an example of a signal processing device according to an embodiment of the present invention, which is applied to a rotating machine sound muffling device.

A rotating machine sound signal output from a microphone (not shown) is input as an input signal K to the basic pulse generation circuit 1 on one side, and to the A/D converter 2 on the other side. The basic pulse generation circuit 1 is composed of a filter circuit 3 and a waveform shaping circuit 4, and is designed to generate a basic pulse L at the zero cross point when the basic frequency component of the input signal K changes from, for example, negative to positive. It is configured. This basic pulse L is then introduced into the sampling signal generation circuit 5.

The sampling signal generation circuit 5 is constituted by, for example, a frequency-shifting phase-locked loop. That is,
A basic pulse L is input to one input terminal of the phase comparator 6, and the output of the phase comparator 6 is introduced into a voltage-controlled oscillator 8 via a low-pass filter 7, and the output of the voltage-controlled oscillator 8 is further frequency-divided. The signal is introduced into the other input terminal of the phase comparator 6 via the phase comparator 9. Note that the frequency division ratio of the frequency divider 9 is determined by the sample number setting device 10. Therefore, in this sampling signal generation circuit 5, the frequency division ratio of the frequency divider 9 is now set to 1/N.
If the frequency of the fundamental pulse L is f, then a sampled signal M with a frequency Nf times higher is always output. This sampling signal M is given on one side to the trigger signal generator 11, and on the other hand as a sampling signal to the A/D converter 2 and as a clock signal to the D/A converter 15, which will be described later. It will be done.

The trigger signal generator 11 inputs a frequency divider 12 that divides the frequency of the sampling signal M by 1/N, and the output of this frequency divider 12 and the fundamental pulse L, and generates the frequency at an arbitrary phase of the fundamental frequency component. The digital comparator 13 outputs a trigger signal P. The trigger signal P is given as a data transfer command to the A/D converter 2 and a data read command to the D/A converter 15.

The A/D converter 2 samples the input signal K with a sampled signal M, converts these samples into digital signals, and temporarily stores them. Then, each time the trigger signal P is applied, the stored data is transferred to the processing section 14.

The processing unit 14 performs a Fourier transform on the data transferred from the A/D converter 2, performs frequency analysis, and multiplies each frequency component by a necessary coefficient. The D/A converter 15 also receives a trigger signal P.
Each time data is given, it reads data from the processing section 14, converts it into an analog signal using the sampling signal M as a clock signal, and outputs it.

Next, the operation of the apparatus configured as described above will be explained with reference to FIG. 2 as appropriate. Input signal K that fluctuates repeatedly
is introduced, the basic pulse generation circuit 1 receives the input signal K
A fundamental frequency component is extracted, and a fundamental pulse L is output every time one zero-crossing point of this fundamental frequency component arrives. On the other hand, if the frequency division ratio of the frequency divider 9 is 1/N, the sampling signal generation circuit 5 generates a sample with a period of 1/N of the period of the fundamental pulse L due to the well-known effect of phase-lock drub. output signal M. Then, the sampling signal M and the basic pulse L are inputted, and the trigger signal P is output from the trigger signal generation circuit 11.

As a result, the A/D converter 2, the processing section 14, and the D/A converter 15 operate at the timing shown in FIG. 2, and the D/A converter 15 outputs an analog output signal Q.

In this way, a fundamental pulse L synchronized with the cycle of the fundamental frequency of the input signal K is generated, and a sample N times the fundamental frequency and synchronized with the set number of samples N is generated within the cycle of the fundamental pulse L. A sampling signal M is generated, and the sampling signal M is used to operate the A/D converter 2 and the D/A converter 15. That is, when the fundamental frequency of the input signal is f, the number of samples is N, and the number of harmonics of f is m, the sampling time Δt is set as Δt in order to always obtain N samples from one period of the fundamental pulse L. -17 (mm f *N). Therefore, n shown in FIG.
Even if the fundamental frequency changes as in the +2nd cycle, n+
A/D conversion can be performed with the same number of samples as in the lth cycle. Also, the D/A conversion in this n+2 cycle is also n+1
The conversion can be performed using the same number of clock signals as the D/A conversion in the period. Therefore, the phase and waveform consistency between the input signal K and the output signal Q can be maintained. Furthermore, since sampling can be completed within the fundamental period of the input signal, leakage errors will not occur even if Fourier transform processing is performed on the data after A/D conversion. Therefore, unlike conventional devices, there is no need to apply a window function to the input signal to eliminate leakage errors. For this reason,
There is no need to correct calculation errors caused by applying a window function, and processing speed and processing accuracy can be improved.

Note that the present invention is not limited to the embodiments described above. That is, the sampling signal generation circuit may use another PLL. Furthermore, the device of the present invention is not limited to use as a rotating machine noise muffling device, but can be applied to other uses as well.

[Effects of the Invention] As described above, according to the present invention, it is possible not only to maintain consistency between the input waveform and the output waveform, but also to shorten the processing time and improve the processing accuracy in the main body of the processing device. can be achieved.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a signal processing device according to an embodiment of the present invention, FIG. 2 is a diagram for explaining the operation of the same device, and FIG. 3 is a diagram for explaining the operation of a conventional signal processing device. This is a diagram for 1... Basic pulse generation circuit, 2... A/D converter,
5... Sampling signal generation circuit, 11... Trigger signal generation circuit, 14... Processing unit as a processing device main body, 15
...D/A converter. Applicant's agent Patent attorney Takehiko Suzue Figure 1

Claims (2)

[Claims] (1) After converting the repeatedly fluctuating input signal into a digital signal using an A/D converter, the signal is passed through the main body of the processing device, and the sampled signal of the A/D converter is converted into a clock signal. In a signal processing device that converts the signal into an analog signal using a D/A converter that operates as and a sample that continuously generates a synchronized sampling signal at N times the fundamental frequency in correspondence with a set number of samples N within the period of the fundamental pulse obtained by this means. What is claimed is: 1. A signal processing device comprising: conversion signal generation means. (2) The signal processing device according to claim 1, wherein the sampling signal generating means is constituted by a frequency multiplication type phase-locked loop that operates by inputting the fundamental pulse generated by the fundamental pulse generating means.