CN1196483A - Method and system for collecting frequency spectrum amplitude phase information of ultrasonic signal - Google Patents

Abstract

A system for extracting information on spectrum, amplitude and phase from ultrasonic echo signal is composed of ultrasonic pulse emitter, ultrasonic piezoelectric transducer, RF pulse receiver-amplifier, A/D converter and microcomputer. The signals obtained by RF pulse receiver-amplifier are digitalized and then stored in memory of microcomputer. The digital echo f(I) goes through FFT transform to obtain spectrum function. After modification, it goes through IFFT transform to obtain analytic function, whose amplitude and phase are just those of echo. So that the ultrasonic detection develops from qualitative analysis to quantitative analysis.

Description

A kind of method and system of extracting the spectral amplitude phase information of ultrasound echo signal

The present invention relates to a kind of method and system of extracting ultrasound echo signal information in the Ultrasonic NDT, international Patent classificating number is: GO1H

When Ultrasonic Detection, need obtain the various relevant informations of tested material, they often are included in the waveform of radio-frequency echo wave.Conventional ultrasound measuring instruments such as the super and B ultrasonic of A just show the amplitude envelope information of ultrasound echo signal, promptly utilize the amplitude detection waveform of echoed signal, and this is the part in the echo signal information data obviously.In the recent period, the domestic people of having carries out spectrum analysis to echoed signal, but Shang Weiyou is to the method for ultrasound echo signal phase information extraction and the report of system thereof.

The present invention aims to provide a kind of method and system of intactly extracting the information of whole relevant tested material behaviors that ultrasound echo signal carries, makes people when using the ultrasonic echo method to detect or evaluating tested material behavior, can utilize more useful information.This impels Ultrasonic Detection to be developed to quantitative test by qualitative analysis to improving the accuracy and the reliability of Ultrasonic Detection, has practical significance, and brings bigger economic benefit.

The object of the present invention is achieved like this, promptly become detection system with the microcomputer organic assembling, in microcomputer, carry out frequency spectrum, the amplitude of echoed signal, the extraction and the analysis of phase place by commonly used ultrasonic pulse transmitter, excess sound pressure electric transducer, radio-frequency pulse reception amplifier, A/D converter, clock.Be described as follows:

Fig. 1 is a systematic schematic diagram of the present invention, wherein: 1---the ultrasonic pulse transmitter, 2---the excess sound pressure electric transducer, 3---the radio-frequency pulse reception amplifier, 4---A/D converter, 5---clock, 6---microcomputer.

Fig. 2 is a main program flow chart of the present invention, wherein: 7---beginning, 8---High frequency filter is asked f (I), and 9---the FFT conversion of f (I) is asked , 10---revise, 11---f＜0 o'clock,

, 12---f) 0 o'clock,

The IFFT conversion ask F ^A(I), 14---asking A (I), 15---are asked (I), I (I), 16---finish.

Fig. 3 is a check and analysis oscillogram of the present invention, wherein 17---and f (I), I) power spectrum, 19---F ^A(I) real part, 20---F ^A(I) imaginary part, 21--- (I), 22---I (I), 23---A (I).

One, system

As shown in Figure 1, after connecting successively, the high-speed a/d converter 4 of ultrasonic pulse transmitter 1, excess sound pressure electric transducer 2, radio-frequency pulse reception amplifier 3,50MHz is connected with 486/586 microcomputer 6 by interface again, clock 5 is connected with ultrasonic pulse transmitter 1 and A/D converter 4 respectively, thereby forms the system that realizes the object of the invention.

Two, method

As seen from Figure 1, Figure 2:

(1) asks digital echo signal f (I)

A row rf echo signal that obtains by radio-frequency pulse reception amplifier 3, carry out analog to digital conversion through 50MHz A/D converter 4, its digitizing is delivered to microcomputer 6 internal memories and made work begin 7, and carry out High frequency filter with the method for moving average and ask f (I) 8, promptly obtain the discrete digital echo signal f (I) of corresponding row.Wherein, I=1,2,3 ... N, N are total number of sampling.

(2) ask the frequency spectrum function of f (I)

F (I) is carried out the FFT conversion, obtain its frequency spectrum function

Suppose that f (I) is 256 points at the sampled point of time domain, each sampled point time corresponding is spaced apart 0.02 μ s, after the FFT conversion, and 256 points that frequency domain obtains, the frequency interval that each point is corresponding is 1/N * 0.02.MHz, i.e. 0.1953MHz.In these 256 points, from left end, starting point is 0, the positive frequency spectrum part that 128 points are arranged is echo waveforms, the 128th size corresponding to the f (I) at the 25MHz place on the frequency axis.Locate at the 256th, to the left side 128 negative frequency spectrum parts corresponding to echo waveform were also arranged as 0 starting point with the 256th o'clock, positive and negative spectrum component is symmetrical with its mid point on frequency axis.It should be noted that

Be plural number, its Power Spectrum Distribution should be each frequency component real part square with square sum of imaginary part.

(3) ask the analytical function F of f (I) ^A(I)

According to the characteristic of Hilbert transform, revise frequency spectrum function

For , purpose is to seek the analytical function F of f (I) ^A(I), make F ^A(I) real part is digital echo signal f (I), and imaginary part is the Hilbert transform function F (I) of f (I).In fact, this method is not really obtained the corresponding Hilbert transform function F (I) of f (I) by the way of Hilbert transform, but passes through the FFT transforming function transformation function of F (I) Try to achieve with the relation of f (I) , get F by the IFFT conversion again ^A(I).Concrete steps are as follows:

1., whether check the pairing frequency of I greater than 0, if I has 256 points, then the pairing frequency of I of from 0 to 128 point is all greater than 0, makes each point

For

2 times become 2f (I) 12, and to I from 129 o'clock to 256 o'clock, pairing frequency makes the F of each point all less than 0 ^A(I) all become 011, promptly resulting revised new frequency spectrum function of ordering from 0-256 is

2., with F ^A(I) carry out the IFFT conversion, just can obtain analytical function F corresponding to f (I) ^A(I) 13.

(4), ask amplitude A (I), phase place (I), the phase change rate I (I) of f (I).

Mathematics and reality proves, the analytical function F that is obtained by above-mentioned steps ^A(I) amplitude A (I) and phase place (I) are exactly amplitude and the phase place of digital echo signal f (I), extract F so ^AThe phase place of amplitude (I) is extracted amplitude and the phase place of f (I) exactly.

A (I) can be by F ^A(I) real part f (I) square with imaginary part F (I) square sum again the numerical value of evolution obtain, compile out the detection amplitude envelope A (I) 14 that corresponding software program just can obtain the ultrasound echo signal that received.The waveform distortion that A (I) does not have the hardware detection to produce.

(I) can be by F ^A(I) imaginary part F (I) obtains divided by the arc tangent of real part f (I), i.e. (I)=argtg[F (I)/f (I)].

I (I) is obtained by (I) time differential value.Compile out corresponding computed in software program and just can obtain the phase place (I) and the phase change rate I (I) 15 that are received.

Below just be described further in conjunction with the check and analysis oscillogram (Fig. 3) of example:

Excess sound pressure electric transducer 2 actual detected to ultrasound echo signal to deliver to sample frequency through radio-frequency pulse reception amplifier 3 be that 50MHz high-speed a/d converter 4 and interface thereof are delivered to microcomputer 6 internal memories, carry out digital filtering by software program and obtain digital echo signal f (I) 17, this routine I is by changing 1 to 256, adjacent between time corresponding be 0.02 μ s.

F (I) is carried out the FFT conversion, obtain frequency spectrum function

(plural number), its real part square adds that imaginary part square sum is exactly its power spectrum function 18, as seen power spectrum function is to be symmetrical with its mid point, the left side is corresponding to positive portions of the spectrum, right-hand part is corresponding to negative portions of the spectrum, owing to be with the sampling of 50MHz speed A/D converter, so the corresponding 25MHz of the frequency of mid point.

Will

Frequency spectrum function is made correcting process, makes when I is at 0 o'clock to 128 o'clock, and its corresponding frequency spectrum is Its corresponding frequency spectrum is 0 when I is at 129 to 256, thereby obtains new frequency spectrum function

, again will Carry out the IFFT conversion, obtain complex function F ^A(I), i.e. the analytical function of f (I).Its real part waveform 19 is almost completely the same with f (I) 17, its imaginary part waveform 20 is Hilbert transform function F (I) of f (I), this shows, this method is not carried out Hilbert transform and is handled, only carry out positive and negative each fourier transform, just can obtain the Hilbert transform function F (I) of f (I) dexterously.

Because the top F that proved ^A(I) amplitude envelope A (I) and phase place (I) are exactly amplitude envelope A (I) and the phase place (I) of f (I), so the amplitude of f (I) and phase information can be by F ^A(I) data are tried to achieve:

Phase place (I) waveform of f (I) is 21, (I)=argtg[F (I)/f (I)]

The rate of change I (I) of the phase place (I) of f (I) is

The waveform of the amplitude envelope A (I) of f (I) is 23, $A\left(I\right)=\sqrt{f{\left(I\right)}^2+F{\left(I\right)}^2}$

According to above-mentioned example, compile out corresponding software programs, just can obtain 21,22,23 the distributed wave of Fig. 3.

The present invention has following advantage: 1, the present invention is according to the characteristic of Hilbert transform, but directly do not carry out Hilbert transform, just the echoed signal that receives is carried out after a fourier transform gets its required spectrum information, by the characteristic of Hilbert transform frequency spectrum is revised again, carry out once anti-fourier transform to revising the back frequency spectrum again, just can obtain the detection amplitude that does not have waveform distortion of required echoed signal and the distributed intelligence of phase place and phase change rate with serving multiple dexterously, make people when detecting or evaluate the characteristic of measured material, more useful information be can grasp, thereby the accuracy and the reliability of Ultrasonic Detection improved.

2, the present invention is not only applicable to industrial Ultrasonic NDT, also is applicable to aspects such as medical ultrasound, ultrasound computed tomography, impulse ultrasound holography.Measure in the time of three kinds of information of ultrasonic echo waveform frequency spectrum amplitude phase place, work in coordination, can impel Non-Destructive Testing by qualitative to quantitative development.

Claims (2)

1, a kind of method and system of extracting the spectral amplitude phase information of ultrasound echo signal, it is characterized in that realizing its purpose system by ultrasonic pulse transmitter (1), excess sound pressure electric transducer (2), radio-frequency pulse reception amplifier (3), A/D converter (4) connect successively by after be connected with 486/586 microcomputer (6) by interface again and form, clock (5) is connected with ultrasonic pulse transmitter (1), A/D converter (4) respectively.

2, a kind of method and system of extracting the spectral amplitude phase information of ultrasound echo signal is characterized in that realizing that its purpose method is:

(1) detects a row rf echo signal that obtains by radio-frequency pulse reception amplifier (3), carry out analog to digital conversion, its digitizing is delivered to microcomputer (6) internal memory and obtained a corresponding row discrete digital echoed signal f (I) through A/D converter (4);

(2) digital echo signal f (I) is carried out the FFT conversion, obtain its frequency spectrum function (I) (plural number), again its real part square is added that imaginary part square is the Power Spectrum Distribution function of digital echo signal f (I), the Power Spectrum Distribution function is symmetric points with the axes of coordinates mid point, left-right symmetric, the left side is corresponding to the spectrum distribution of frequency greater than 0 o'clock, and the right is corresponding to the spectrum distribution of frequency less than 0 o'clock;

(3) with frequency spectrum function , carry out correcting process according to the characteristic of Hilbert transform, promptly when the frequency of I correspondence greater than 0 the time, Numerical value, comprise that real part and imaginary part all double, and become

, less than 0 o'clock, f (I) was 0 entirely in frequency, thereby obtained new revised frequency spectrum function

(4) will Carry out the IFFT conversion, get analytical function F ^A(I), F ^A(I) real part is f (I), F ^A(I) imaginary part is the Hilbert transform function F (I) of f (I), F ^A(I) amplitude and phase place are amplitude A (I) and the phase place (I) of f (I).

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