CN103187949A - Filter for extracting digital logarithm rectification amplitude - Google Patents

Abstract

The present invention relates to a kind of filters of digital logarithm rectification amplitude extraction, it is characterized in that body surface EEG signals, signal x (n) by obtaining after acquisition and compensation obtains amplitude-integrated output signal y (n) by the filter of the digital logarithm rectification amplitude extraction. The amplitude-integrated output signal y (n) are as follows: In formula: y (n) be amplitude-integrated signal, x (n) after number rectification be signal, Cj after CFM compensation filter be correction parameter, the sample frequency that fs is x (n), f0 are the sample frequency of y (n), the unit impact response that d (i) is a kind of ideal capacitance. Fs and f0 takes 400Hz, and when d (i) is hamming window function, sampled and compensated body surface brain signal carries out the amplitude-integrated EEG signals that amplitude extraction obtains semilog. Big, the occasion of amplitude extraction high resolution in the variation amplitude of signal, digital logarithm rectification amplitude provided by the invention can obtain good effect, the digital filter suitable for Digital signal processing.

Description

A kind of digital logarithm rectification amplitude extraction filter

Technical field

The present invention relates to a kind of digital logarithm rectification amplitude extraction filter, be applicable to the digital filter of medical Digital Signal Processing, be applicable to research and development and Medical Instruments.Belong to the CFM filter field.

Background technology

For many years, brain damage is the main reason that neonatal period is dead and disable always.Ministry of Public Health's statistics demonstration in 2004 suffocates during death causes of newborn infants constitutes and complication accounts for 26.5%, and row rank first.In addition, premature's brain damage (comprising intracranials hemorrhage softens with periventricular white matter) also is the major reason that causes children cerebral palsy and feeblemindedness.Therefore the early diagnosis research of newborn baby damage, and in time carry out newborn baby damage examination in China, population and the general level of the health that improves China there is very important realistic meaning.

The amplitude-integrated cerebral function monitoring has important role to early detection and the examination of newborn baby damage, digital amplitude-integrated cerebral function monitoring is different from traditional brain, its mechanism does not also lie in the electroencephalogram (EEG) waveform in the concrete a certain moment, and is long variation tendency.Since this new signal processing method of the amplitude-integrated brain electricity of external proposition, states such as USA and Europe all strengthen the research to this medical domain, starting late of domestic amplitude-integrated electroencephalogram (EEG), professor Shao Xiaomei of one of the present patent application people Children's Hospital, Fudan University waits and takes the lead in beginning neonatal amplitude-integrated brain electricity is studied in late 1990s.The national multiple center clinical study result who carries out shows that the amplitude-integrated cerebral function monitoring with continuous multi-faceted monitoring in 24 hours has good effect in the newborn baby damage.This research is one of clinical multicenter study of present 3 sample size maximums in the world, also is unique research that represents the asian population feature.

The amplitude-integrated cerebral function monitoring, the body surface EEG signals of mainly sampling after the signal processing, extract the amplitude variations of signal, carry out record.Have safety, convenient, accurately, be not subject to advantage such as interference.Through after the amplification, sampling, CFM compensation filter, signal done amplitude extracts, the semilog compression could obtain amplitude-integrated brain wave patterns for diagnosing.The robustness of amplitude extraction algorithm, antijamming capability, adaptability have influenced the performance of amplitude-integrated cerebral function monitor device to a great extent.Because the body surface EEG signals are extremely faint, in amplifying gatherer process, easily introduce bigger noise; Because behaviors such as neonatal limb motion are difficult to control, in sampling process, also be easy to introduce multiple interference such as drift, myoelectricity in addition.Traditional rectification module is made of diode, electric capacity or its equivalent electric circuit, adopts the simulation rectification module can extract amplitude signal to the signal amplification back of 5-250 microvolt.But the simulation rectification module has the shortcoming that temperature drift is big, be subject to disturb, so most electroence phalograph all requires to use in the shielding machine room, requires the experimenter to loosen, be in sleep or half asleep.If adopt the simulation commutation technique, being on a grand scale of circuit, cost height, poor reliability, the limitation that the application of simulation commutation technique is subjected to more is very big.So the method for rectifying of rectification module that must abandoning tradition and simulation rectification module intends providing a kind of digital logarithm filter that new rectification amplitude extracts, satisfying the requirement that the neonate uses, thereby be guided out the application's design.

Summary of the invention

The object of the present invention is to provide a kind of digital logarithm rectification amplitude extraction filter, also namely the invention describes a kind of digital filter that can be used for amplitude-integrated brain wave patterns extraction.The patient who is primarily aimed at this specific group of neonate, its state is wayward, add the requirement of 24 hours on-line monitors, require to break away from the shielding machine room, and can under conventional environment, use, the structure of digital logarithm rectification amplitude extraction filter as shown in Figure 1, the EEG signals of patient's body surface, by gathering and compensate the back signal x (n) that obtains by digital logarithm rectification amplitude extraction filter described in the invention, can obtain amplitude-integrated signal y (n).The process that obtains is as follows:

$y\left(n\right)=\underset{j=0}{\overset{f0}{\mathrm{\Σ}}}{C}_j\left(\underset{i=-\mathrm{fs}/4}{\overset{\mathrm{fs}/4}{\mathrm{\Σ}}}\right|x(n-i+j\·\mathrm{fs})\left|d\left(i\right)\right)$

In the formula: y (n) is the amplitude-integrated signal after the digital rectification

X (n) is through the signal behind the CFM compensation filter

Cj is correction parameter

Fs is the sample frequency of x (n)

F0 is the sample frequency of y (n)

D (i) is a kind of unit impact response of ideal capacitance

Y (n) obtains amplitude-integrated signal after resampling through f0, handles obtaining amplitude-integrated EEG signals through incomplete logarithm

z(n)＝a log[y(n)] y(n)＞5μV

z(n)＝a y(n) y(n)≤5μV

Variation amplitude at signal is big, and amplitude extracts the high occasion of resolution, and digital logarithm rectification amplitude extraction algorithm can both be obtained good effect, is applicable to the digital filter of medical Digital Signal Processing, is particularly useful for the requirement that the neonate uses.

Description of drawings

Fig. 1 is logarithm numeral rectification schematic diagram provided by the invention.

Fig. 2 is the structure of filtering algorithm of the present invention.

Embodiment

Digital logarithm rectification amplitude extraction filter can be used in various instruments.The present invention will be further described below in conjunction with specific embodiment, should be clear, below just to an explanation of the present invention, and not will be understood that it is limitation of the invention.

The step extracted of digital logarithm rectification amplitude provided by the invention is the body surface EEG signals as shown in Figure 1, by gather and signal x (n) that the compensation back obtains by the filter of described digital logarithm rectification amplitude extraction, obtain amplitude-integrated output signal y (n).

And for example Fig. 2 is the schematic diagram to amplitude-integrated output signal filtering algorithm structure.

Be example with the amplitude-integrated cerebral function monitoring, fs and f0 all get 400Hz, and d (i) gets the hamming window function, the body surface EEG signals after over-sampling, compensation are carried out amplitude extract the amplitude-integrated EEG signals that just can obtain semilogization.Certainly, can realize better amplitude extraction effect with suitable adjustment d (i) and C (j) curve of clinical verification by experiment, filter of the present invention has been obtained good effect in clinical practice.

Claims (5)

1. a digital logarithm rectification amplitude extraction filter is characterized in that the body surface EEG signals, by gathering and compensate the back signal x (n) that obtains by described digital logarithm rectification amplitude extraction filter, obtains amplitude-integrated output signal y (n).

2. by the described filter of claim 1, it is characterized in that described amplitude-integrated output signal y (n) is:

$y\left(n\right)=\underset{j=0}{\overset{f0}{\mathrm{\Σ}}}{C}_j\left(\underset{i=-\mathrm{fs}/4}{\overset{\mathrm{fs}/4}{\mathrm{\Σ}}}\right|x(n-i+j\·\mathrm{fs})\left|d\left(i\right)\right)$

In the formula: y (n) is the amplitude-integrated signal after the digital rectification,

X (n) is through the signal behind the CFM compensation filter,

Cj is correction parameter,

Fs is the sample frequency of x (n),

F0 is the sample frequency of y (n),

D (i) is a kind of unit impact response of ideal capacitance.

3. by the described filter of claim 2, it is characterized in that obtaining amplitude-integrated signal after described y (n) resamples through f0, obtain amplitude-integrated EEG signals z (n) through incomplete logarithm processing and be expressed as:

a)z(n)＝a log[y(n)] y(n)＞5μV，

b)z(n)＝a y(n) y(n)≤5μV。

4. by the described filter of claim 2, it is characterized in that fs and f0 get 400Hz, when d (i) was the hamming window function, the body surface brain signal after sampling and compensation was carried out amplitude and is extracted the amplitude-integrated EEG signals that obtain semilogization.

5. by the described filter of claim 2, it is characterized in that adjusting d (i) and Cj curve and obtain better amplitude extraction effect.

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