# Patent

## Title
Baseline restoration methods and apparatuses and medical detecting equipments thereof

## Abstract

This disclosure relates to baseline restoration methods and apparatuses and medical detecting equipment thereof. The baseline restoration method comprises: determining whether there is a high-amplitude baseline in an input signal by previous k output signals (Y1, . . . , Yk) of a filter, where k is a natural number and k≧1; setting the previous m output signals (Y1, . . . , Ym) of the filter as Y′ when there is a high-amplitude baseline in the input signal, where Y′ is a desired output signal of the filter; and using a current input signal X0, the previous n input signals (X1, . . . , Xn), and the previous m output signals (Y1, . . . , Ym) of said filter to obtain a current output signal Y0 of said filter.

## Background
TECHNICAL FIELD
This disclosure relates generally to medical electronics, particularly to baseline restoration methods and apparatuses and medical detecting equipment thereof.
BACKGROUND
Due to polarization voltage, zero drift and other factors, a baseline of a signal acquired would exceed a dynamic range of the signal during signal collection. When displayed, the signal with a high-amplitude baseline might not be displayed within a display area, or only part of the signal could be displayed within the display area.
In order to observe the complete signal, the baseline should be restored. Because the baseline is a low-frequency signal, a baseline restoration method provided by prior art uses a high-pass filter to remove the baseline. The frequency of the baseline is generally low, so the cut-off frequency of the high-pass filter should be very low. However, the lower the cut-off frequency of the high-pass filter, the longer the time required for the baseline to restore to zero, which leads to the baseline spending a very long time to restore to zero and the requirement for use could not be met. As shown in FIG. 1, assuming that the amplitude of the baseline is 1, the time required for the baseline to restore to zero by a high-pass filter would be more than 20 seconds.
SUMMARY
Disclosed here are embodiments of baseline restoration methods and apparatuses and medical detecting equipment thereof.
In one aspect, a baseline restoration apparatus comprises a filter, a high-amplitude baseline detector and a baseline restoration module.
The high-amplitude baseline detector detects whether there is a high-amplitude baseline in an input signal by the previous k output signals (Y1, . . . , Yk) of said filter, where k is a natural number and k≧1.
Said baseline restoration module sets previous m output signals (Y1, . . . , Ym) of said filter as Y′ when there is a high-amplitude baseline in the input signal, where Y′ is a desired output signal of said filter.
Said filter uses a current input signal X0, the previous n input signals (X1, . . . , Xn), and the previous m output signals (Y1, . . . , Ym) to obtain a current output signal Y0 of said filter.
In another aspect, a baseline restoration method comprises:
determining whether there is a high-amplitude baseline in an input signal by the previous k output signals (Y1, . . . , Yk) of the filter, where k is a natural number and k≧1;
setting the previous m output signals (Y1, . . . , Ym) of the filter as Y′ when there is a high-amplitude baseline in the input signal, wherein Y′ is a desired output signal of the filter; and
using a current input signal X0, the previous n input signals (X1, . . . , Xn), and the previous m output signals (Y1, . . . , Ym) of said filter to obtain a current output signal Y0 of said filter.
In another aspect, a medical detecting equipment comprises a baseline restoration apparatus described above.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows an output signal of a high-pass filter used for baseline restoration in a prior art;
FIG. 2 shows a schematic diagram of a baseline restoration apparatus according to an embodiment.
FIG. 3 shows a specific schematic diagram of the baseline restoration apparatus shown in FIG. 2.
FIG. 4 shows a flow chart of a baseline restoration method according to one embodiment.



DETAILED DESCRIPTION
As shown in FIG. 2, in one embodiment, a baseline restoration apparatus 100 comprises a filter 110, a high-amplitude baseline detector 120 and a baseline restoration module 130. An output port of the filter 110 may be connected to the high-amplitude baseline detector 120, the high-amplitude baseline detector 120 may be connected to the baseline restoration module 130, and the baseline restoration module 130 may be connected to the filter 110.
The high-amplitude baseline detector 120 may detect whether there is a high-amplitude baseline in an input signal by previous k output signals (Y1, . . . , Yk) of the filter, where k is a natural number and k≧1.
When the high-amplitude baseline detector 120 determines there is a high-amplitude baseline in the input signal, the previous m output signals (Y1, . . . , Ym) of the filter may be set to equal to Y′ respectively by the baseline restoration module 130, that is, making Y1=Y′, Y2=Y′, . . . , Ym=Y′, where Y′ is a desired output signal of the filter 110. When the high-amplitude baseline detector 120 determines there is no high-amplitude baseline in the input signal, the baseline restoration 130 does not do anything.
The filter 110 may use a current input signal X0, the previous n input signals (X1, . . . , Xn), and the previous m output signals (Y1, . . . , Ym) of the filter to obtain a current output Y0 of the filter.
In this embodiment, when the high-amplitude baseline is detected, the previous m outputs (Y1, . . . , Ym) of the filter may be set to equal to the desired output signal Y′ respectively. Thus the intermediate process, in which the output signal of the filter drops from the current output signal to the desired output signal, could be skipped, and the time required for the baseline to restore to zero could be decreased. In the meantime, the baseline restoration apparatus has nothing to do with the cut-off frequency of the filter, so it could guarantee that the filter band would not be distorted.
FIG. 3 shows the specific schematic diagram of the baseline restoration apparatus shown in FIG. 2. In this embodiment, the filter 110 may be a high-pass filter, and the cut-off frequency of the filter 110 may be relatively low.
The filter 110 may comprise an input magnification part and an output magnification part. The input magnification part may comprise an input magnification branch and n input delay and magnification branches, and the output magnification branch may comprise an output branch and m output magnification branches.
For the input magnification part, in the input magnification branch, an input end 111 may be connected to an input end of an amplifier a0, and an output end of the amplifier a0 may be connected to a first input end of an adder e0; in the first input delay and magnification branch, the input end 111 may be connected to an input end of a delayer c1, a first output end of the delayer c1 may be connected to an input end of an amplifier a1, an output end of the amplifier a1 may be connected to a first input end of an adder e1, and an output end of the adder e1 may be connected to a second input end of the adder e0. In the second input delay and magnification branch, a second output end of the delayer c1 may be connected to an input end of a delayer c2, a first output end of the delayer c2 may be connected to an input end of an adder a2, an output end of the amplifier a2 may be connected to a first input end of an adder e2, and an output end of the adder e2 may be connected to a second input end of the adder e1; in turn, in the nth input delay and magnification branch, a second output end of a delayer cn-1 may be connected to an input end of a delayer cn, an output end of the delayer cn may be connected to an input end of an adder an, and an output end of the amplifier an may be connected to a second input end of the adder en-1.
The input magnification part may be connected to the output magnification part by connecting an output end of the adder e0 to a first input end of an adder f0.
For the output magnification part, in the output branch, an output end 113 may be connected to the output end of the adder f0; in the first output magnification branch, the output end 113 may be connected to an input end of a delayer d1, a first output end of the delayer d1 may be connected to an input end of an amplifier b1, an output end of the amplifier b1 may be connected to a first input end of an adder f1, and an output end of the adder f1 may be connected to the second input end of the adder f0. In the second output magnification branch, the second output end of the delayer d1 may be connected to an input end of a delayer d2, the first input end of the delayer d2 may be connected to the input end of an amplifier b2, the output end of the amplifier b2 may be connected to the first input end of an adder f2, and the output end of the adder f2 may be connected to the second input end of the adder f1. In the mth output magnification branch, the second output end of a delayer dm-1 may be connected to the input end of a delayer dm, the output signal of the delayer dm may be connected to the input end of an amplifier bm, and the output end of the amplifier bm may be connected to the second input end of the adder bm-1.
In the first embodiment, the high-amplitude detector 120 may detect whether all the previous k output signals (Y1, . . . , Yk) of the filter are greater than a high-amplitude threshold. When all the previous k output signals (Y1, . . . , Yk) of the filter are greater than the high-amplitude threshold, the high-amplitude detector 120 may determine there is a high-amplitude baseline in the input signal. When not all the previous k output signals (Y1, . . . , Yk) of the filter are greater than the high-amplitude threshold, the high-amplitude detector 120 may determine there is no high-amplitude baseline in the input signal.
It could be understood that the high-amplitude threshold may be related to the input signal of the filter 110. The greater the amplitude of the input signal is, the greater the high-amplitude threshold may be; the less the amplitude of the input signal is, the less the high-amplitude threshold may be.
In the second embodiment, the high-amplitude detector 120 may detect whether the output energy of the filter 110 calculated using the previous k output signals (Y1, . . . , Yk) of the filter is greater than an energy threshold. When the output energy of the filter 110 is greater than the energy threshold, the high-amplitude detector 120 may determine there is a high-amplitude baseline in the input signal. When the output energy of the filter 110 is less than or equal to the energy threshold, the high-amplitude detector 120 may determine there is no high-amplitude baseline in the input signal.
It could be understood that the energy threshold may be related to the amplitude of the input signal of the filter 110. The greater the amplitude of the input signal is, the greater the energy threshold may be; the less the amplitude of the input signal is, the less the energy threshold may be.
When the high-amplitude baseline detector 120 determines there is a high-amplitude baseline in the input signal, the previous m output signals 110 (Y1, . . . , Ym) of the filter may be set as Y′ respectively by the baseline restoration module 130, that is, making Y1=Y′, Y2=Y′, . . . , Ym=Y′, where Y′ is the desired output signal of the filter 110.
The filter 110 may use the current input signal X0, the previous n input signals (X1, . . . , Xn), and the previous m output signals (Y1, . . . , Ym) of the filter 110 to obtain the current output signal Y0 of the filter.
For the input magnification part, the current input signal X0 may be input into the amplifier a0 and the delayer c1 of the first input delay and magnification branch through the input end 111. The input signal X1 stored in the delayer c1 may be inputted into the amplifier a1 to obtain the magnified signal a1X1, . . . . The value of the input signal Xn outputted by the delayer cn of the nth input delay and magnification branch may be inputted into the amplifier an to obtain an amplified signal anXn.
The amplified signal anXn and an-1Xn-1 may be inputted into and summed by the adder en-1, and the output signal of the adder en-1 and the amplified signal an-2Xn-2 may be inputted into and summed by the adder en-2, . . . . In turn, the output signal of the adder e1 and the amplified signal a0X0 may be inputted into and summed by the adder e0, and the output signal of the adder e0 may be the first sum value Sx=a0X0+a1X1+ . . . +anXn.
For the output magnification part, the current output signal Y0 may be inputted into the delayer d1 of the first output magnification branch, the output signal Y1 of the delayer d1 may be inputted into the amplifier b1 to obtain the magnified output signal b1Y1, and the output signal Y1 may be inputted into the delayer d2 of the second output magnification branch. The output signal Ym-1 may be inputted into the delayer dm of the mth delay and magnification branch, and the output signal Ym stored in the delayer dm may be inputted into the magnification bm to obtain the magnified output signal bmYm.
The amplified output signal bmYm and bm-1Ym-1 may be inputted into and summed by the adder fm-1, the output signal of the adder fm-1 and the magnified output signal bm-2Ym-2 may be inputted into and summed by the adder fm-2, . . . , and the output signal of the adder f2 and the magnified output signal b1Y1 may be inputted into and summed by the adder f1 to obtain the second sum value Sy=b1Y1+ . . . +bmYm.
The first sum value Sx outputted by the adder e0 and the second sum value Sy outputted by the adder f1 may be inputted into and summed by the adder f0 to obtain the current output signal Y0=(a0X0+a1X1+ . . . +anXn) (b1Y1+ . . . +bmYm), where Y1=Y′, Y2=Y′, . . . , Ym=Y.
It could be understood that the structure of the filter 110 described above is just one embodiment of the present disclosure, and the filter 110 could be realized by other structures in other embodiments.
In addition, when the high-amplitude baseline detector 120 determines there is a high-amplitude baseline in the input signal, the baseline restoration module 130 may make Y1=Y1′, Y2=Y2′, . . . , Ym=Ym′, where Y1′, Y2′, . . . , and Ym′ cannot be exactly the same. The output signal of the filter could decline rapidly when the difference among Y1′, Y2′ . . . , and Ym′ is within a certain error range. The error range may be related to the amplitude of the input signal. The bigger the amplitude of the input signal, the bigger the error range allowed; the smaller the amplitude of the input signal, the smaller the error range allowed.
FIG. 4 shows a flow chart of a baseline restoration method in an embodiment. The baseline restoration method could include the following steps:
Step 410: detect whether there is a high-amplitude baseline in an input signal by previous k outputs (Y1, . . . , Yk) of the filter, where k is a natural number and k≧1. The filter could be a high-pass filter, and the cut-off frequency of the high-pass filter may be low.
Step 420: when there is a high-amplitude baseline in the input signal, set the previous m output signals (Y1, . . . , Ym) of the filter as Y′ respectively, that is, making Y1=Y′, Y2=Y′, . . . , Ym=Y′, where Y′ is the desired output signal of the filter.
Step 430: use a current input signal X0, previous n input signals (X1, . . . , Xn), and previous m output signals (Y1, . . . , Ym) of the filter to obtain a current output Y0 of the filter.
Step 410 could include the following steps: (1) detect whether all the previous k output signals (Y1, . . . , Yk) of the filter are greater than the high-amplitude threshold; (2) when all the previous k output signals of the filter are greater than the high-amplitude threshold, determine whether there is a high-amplitude baseline in the input signal; (3) when not all the previous k output signals of the filter are greater than the high-amplitude threshold, determine whether there is no high-amplitude baseline in the input signal.
In another embodiment, step 410 could include detecting whether the output energy of the filter calculated using the previous k output signals (Y1, . . . , Yk) of the filter is greater than an energy threshold. When the output energy of the filter is greater than the energy threshold, there is a high-amplitude baseline in the input signal; when the output energy of the filter is less than or equal to the energy threshold, there is not a high-amplitude baseline in the input signal.
Step 430 could include the following steps: (1) magnify the current input signal X0 and the previous n input signals (X1, Xn) by magnification factors (a0, a1, . . . , an) respectively, (2) sum all magnified input signals to obtain a first sum value Sx, where n is a natural number and n≧1; (3) magnify the previous m output signals (Y1, . . . , Ym) of the filter by magnification factors (b1, . . . , bm) respectively, (4) sum all magnified output signals to obtain a second sum value Sy, where m is a natural number and m≧1; and (5) sum the first sum value Sx and the second sum value Sy to obtain a current output signal Y0=(a0X0+a1X1+ . . . +anXn)+(b1Y1+ . . . +bmYm).
In this embodiment, the filter could be a high-pass filter.
This embodiment may be similar to the previous embodiments, the details of which could be understood to refer to FIGS. 2 and 3 and the related description above.
In one embodiment, a medical detecting equipment could comprise a baseline restoration apparatus described above, the details of which could be understood to refer to FIGS. 2 and 3 and the related description above.
In the above embodiments, when a high-amplitude baseline is detected, the previous m output signals (Y1, . . . , Ym) of the filter are set as Y′ respectively. Thus the intermediate process in which the value of the filter's output drops from the current output signal to the desired output signal could be skipped, and the time required for the baseline to restore to zero could be decreased. In the meantime, the baseline restoration apparatus has nothing to do with the cut-off frequency of the filter, so it could guarantee that the filter band would not be distorted.
This disclosure has been made with reference to various exemplary embodiments. However, those skilled in the art will recognize that changes and modifications may be made to the exemplary embodiments without departing from the scope of the present disclosure. While the principles of this disclosure have been shown in various embodiments, many modifications of structure, arrangements, proportions, elements, materials, and components may be adapted for a specific environment and/or operating requirements without departing from the principles and scope of this disclosure. These and other changes or modifications are intended to be included within the scope of the present disclosure.
One of ordinary skill in the art will appreciate that all or parts of steps of the method could be executed by relative hardware under direction of a computer program, and the computer program could be stored in computer-readable storage media, which could be a magnetic disk, a light disk, a Read-Only Memory, a Random Access Memory, and so on.
The foregoing specification has been described with reference to various embodiments. However, one of ordinary skill in the art will appreciate that various modifications and changes can be made without departing from the scope of the present disclosure. Accordingly, this disclosure is to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope thereof. Likewise, benefits, other advantages, and solutions to problems have been described above with regard to various embodiments. However, benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, a required, or an essential feature or element. The scope of the present invention should, therefore, be determined by the following claims.

## Claims

1. A baseline restoration apparatus, comprising:
a filter;
a high-amplitude baseline detector configured to detect whether there is a high-amplitude baseline in an input signal by previous k output signals (Y1, . . . , Yk) of said filter, wherein k is a natural number and k≧1; and
a baseline restorer configured to set previous m output signals (Y1, . . . , Ym) of said filter as Y′ when there is a high-amplitude baseline in the input signal, wherein Y′ is a desired output signal of said filter, wherein
said filter uses a current input signal X0, the previous n input signals (X1, . . . , Xn), and the previous m output signals (Y1, . . . , Ym) to obtain a current output signal Y0 of said filter, wherein m and n are natural numbers, and m and n are greater than or equal to 1.

2. The baseline restoration apparatus of claim 1, wherein said high-amplitude detector determines there is a high-amplitude baseline in the input signal when the previous k output signals (Y1, . . . , Yk) of the filter are all greater than a high-amplitude threshold, and determines there is no high-amplitude baseline in the input signal when not all the previous k output signals (Y1, . . . , Yk) are greater than the high-amplitude threshold.

3. The baseline restoration apparatus of claim 1, wherein said high-amplitude detector determines there is a high-amplitude baseline in the input signal when an output energy of said filter calculated using the previous output signals (Y1, . . . , Yk) is greater than an energy threshold, and determines there is no high-amplitude baseline in the input signal when the output energy of said filter is less than or equal to the energy threshold.

4. The baseline restoration apparatus of claim 1, wherein said filter magnifies the current input signal X0 and the previous n input signals (X1, . . . , Xn) by magnification factors (a0, a1, . . . , an) respectively and sums the magnified input signals to obtain a first sum value Sx, magnifies the previous m output signals (Y1, . . . , Ym) by magnification factors (b1, . . . , bm) respectively and sums the magnified output signals to obtain a second sum value Sy, and adds the first sum value Sx and the second sum value Sy to obtain the current output signal of the filter Y0=(a0X0+a1X1+ . . . +anXn)+(b1Y1+ . . . +bmYm), wherein n is a natural number and n≧1, and m is a natural number and m≧1.

5. The baseline restoration apparatus of claim 1, wherein said filter is a high-pass filter.

6. A medical detecting equipment, wherein said equipment comprises the baseline restoration apparatus of claim 1.

7. A baseline restoration method, comprising:
determining that there is a high-amplitude baseline in an input signal by previous k output signals (Y1, . . . , Yk) of a filter, wherein k is a natural number and k≧1;
setting previous m output signals (Y1, . . . , Ym) of said filter as Y′ when there is a high-amplitude baseline in the input signal, wherein Y′ is a desired output signal of the filter; and
using a current input signal X0, the previous n input signals (X1, . . . , Xn), and the previous m output signals (Y1, . . . , Ym) of said filter to obtain a current output signal Y0 of said filter, wherein m and n are natural numbers, and m and n are greater than or equal to 1.

8. The method of claim 7, wherein determining that there is a high-amplitude baseline in an input signal by previous k output signals (Y1, . . . , Yk) of said filter comprises:
determining whether the previous k output signals (Y1, . . . , Yk) of said filter are all greater than a high-amplitude threshold; and
determining whether there is a high-amplitude baseline in the input signal when all of the previous k outputs of said filter are greater than the high-amplitude threshold, and there is no high-amplitude baseline in the input signal when not all of the previous k output signals of said filter are greater than the high-amplitude threshold.

9. The method of claim 7, wherein determining whether there is a high-amplitude baseline in an input signal by the previous k output signals (Y1, . . . , Yk) of said filter comprises:
determining whether an output energy of said filter calculated using the previous k output signal (Y1, . . . , Yk) of said filter is greater than an energy threshold; and
determining whether there is a high-amplitude baseline in the input signal when the output energy of said filter is greater than the energy threshold, and there is no high-amplitude baseline in the input signal when the output energy of said filter is less than or equal to the energy threshold.

10. The method of claim 7, wherein using the current input signal X0, the previous n input signals (X1, . . . , Xn), and the previous m output signals (Y1, . . . , Ym) of said filter to obtain the current output signal Y0 of said filter comprises:
magnifying the current input signal X0 and the previous n input signals (X1, . . . , Xn) by magnification factors (a0, a1, . . . , an) respectively, wherein n is a natural number and n≧1;
summing the magnified input signals to obtain a first sum value Sx;
magnifying the previous m output signals (Y1, . . . , Ym) of said filter by magnification factors (b1, . . . , bm) respectively;
summing the magnified output signals to obtain a second sum value Sy; and
summing the first sum value Sx and the second sum value Sy to obtain the current output signal Y0=(a0X0+a1X1+ . . . +anXn)+(b1Y1+ . . . +bmYm) of said filter, wherein m is a natural number and m≧1.

11. The method of claim 7, wherein said filter is a high-pass filter.