CN1933770A - 用于输出生理信号的模拟表示的δ－σ调制器 - Google Patents

用于输出生理信号的模拟表示的δ－σ调制器 Download PDF

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CN1933770A
CN1933770A CNA2005800058567A CN200580005856A CN1933770A CN 1933770 A CN1933770 A CN 1933770A CN A2005800058567 A CNA2005800058567 A CN A2005800058567A CN 200580005856 A CN200580005856 A CN 200580005856A CN 1933770 A CN1933770 A CN 1933770A
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delta sigma
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sigma manipulator
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伊桑·彼得森
威廉·谢伊
布拉德福德·B·丘
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Nellcor Puritan Bennett LLC
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M3/00—Conversion of analogue values to or from differential modulation
    • H03M3/02—Delta modulation, i.e. one-bit differential modulation
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
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    • A61B5/14551—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue using optical sensors, e.g. spectral photometrical oximeters for measuring blood gases
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M7/00—Conversion of a code where information is represented by a given sequence or number of digits to a code where the same, similar or subset of information is represented by a different sequence or number of digits
    • H03M7/30—Compression; Expansion; Suppression of unnecessary data, e.g. redundancy reduction
    • H03M7/3002—Conversion to or from differential modulation
    • H03M7/3004—Digital delta-sigma modulation
    • H03M7/3015—Structural details of digital delta-sigma modulators
    • H03M7/3031—Structural details of digital delta-sigma modulators characterised by the order of the loop filter, e.g. having a first order loop filter in the feedforward path
    • H03M7/3042—Structural details of digital delta-sigma modulators characterised by the order of the loop filter, e.g. having a first order loop filter in the feedforward path the modulator being of the error feedback type, i.e. having loop filter stages in the feedback path only
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M7/00—Conversion of a code where information is represented by a given sequence or number of digits to a code where the same, similar or subset of information is represented by a different sequence or number of digits
    • H03M7/30—Compression; Expansion; Suppression of unnecessary data, e.g. redundancy reduction
    • H03M7/3002—Conversion to or from differential modulation
    • H03M7/3004—Digital delta-sigma modulation
    • H03M7/3015—Structural details of digital delta-sigma modulators
    • H03M7/302—Structural details of digital delta-sigma modulators characterised by the number of quantisers and their type and resolution
    • H03M7/3024—Structural details of digital delta-sigma modulators characterised by the number of quantisers and their type and resolution having one quantiser only
    • H03M7/3028—Structural details of digital delta-sigma modulators characterised by the number of quantisers and their type and resolution having one quantiser only the quantiser being a single bit one

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Abstract

本发明提供一种用于提供一生理信号的一模拟表示的大体实时表示的方法和设备。将来自传感器的波形信号转换成数字形式。Δ－∑调制器用作一简单的数字到模拟转换器(ADC)。接着，通过简单硬件滤波器提供输出，以近似实时地给出模拟输出信号，其可用于其它仪器、同步、显示器等。

Description

用于输出生理信号的模拟表示的Δ-∑调制器
技术领域
本发明涉及血氧计，且更特定而言，本发明涉及脉冲血氧计中的模拟波形显示。
背景技术
脉冲血氧定量法通常用于测量各种血液化学特征，包括(但不限于)：动脉血液中血红蛋白的血氧饱和度、供应给组织的个别血液脉动的体积，和对应于患者的每一次心跳的血液脉动率。使用非侵入性传感器来完成这些特征的测量。所述传感器将光散射而穿过患者组织中有血液灌注到组织的一部分，且光电地感测所述组织中光的吸收。以不同频率吸收的光的量接着用于计算被测量的血液成分的量。
选择散射过组织的光以具有一个或一个以上的波长，其由血液吸收且吸收数量表示血液中的血液成分的量。散射过组织的所传输的光的量将根据组织中血液成分的变化量和相关的光吸收而改变。根据用于测量血氧饱和度的已知技术，为测量血氧含量，所述传感器通常具有适用于产生至少两种不同波长的光的光源，及对于这些波长敏感的光电检测器。
已知的非侵入性传感器包括紧固到身体的一部分(如，手指，耳朵或头皮)的装置。在动物和人类中，这些身体部分的组织灌注有血液，且组织表面易于由传感器所接近。
在处理传感器数据并计算氧饱和度之后，脉冲血氧计将所述信息呈现给显示器。在一些脉冲血氧计中，也需要显示模拟波形本身。例如，美国专利第6,188,470号展示用于反映波形的显示的信号。美国专利第6,385,471号也论述一波形显示，且陈述：首先数字化、预滤波数据，且接着重构所述数据以用于显示。
本发明的受让人，Nellcor Puritan Bennett，在其许多产品中提供模拟输出。模拟输出是用于这样的目的：如与其它仪器(例如，EKG、多参数监视器)同步，也用于显示器。有时从硬件预处理电路提供模拟波形，以确保模拟信号及时地接近实际患者波形。
在处理后提供模拟波形给显示器的问题是：处理要花费一段时间，且因此所提供的信号被延迟，而不是实时信号。
发明内容
本发明提供一种用于提供生理信号的模拟表示的大体实时表示的方法和设备。将来自传感器的波形信号转换成数字形式。一Δ-∑调制器用作简单的数字到模拟转换器(ADC)。接着可通过一简单的硬件滤波器提供输出，以近似实时地给出模拟输出，其可用于其它仪器、同步、显示器等。
本发明允许将波形转换成数字形式，且供应给软件，同时仍允许在软件中初步处理后快速转换回硬件中。特别地，对于在软件中进行解调的脉冲血氧计而言，可在这个软件解调之后，但在慢得多的软件滤波处理(用作计算氧饱和度的处理的一部分)之前获得数字DR.信号。
在一个实施例中，在一第一路径中处理数字信号，但一第二路径将这个经数字化波形施加给Δ-∑调制器。所述第二路径在这个信号经转换成数字形式且经解调后立即传感这个信号。对于脉冲血氧计，选择IR信号用于模拟输出，因为它通常具有较少的噪音。
在一个实施例中，Δ-∑调制器是对波形的数字化版本进行操作的软件调制器。Δ-∑调制器提供单一位串行输出。这个输出提供给硬件RC滤波器，且接着提供给显示器。
为了进一步理解本发明的性质和优点，可参考结合附图所说明的以下实施方式。
附图说明
图1是并入本发明的血氧计的方框图。
图2是现有技术的用于产生模拟输出信号的电路的方框图。
图3是根据本发明的用于产生模拟输出信号的电路的实施例的方框图。
图4是根据本发明的一实施例的软件Δ-∑调制器的方框图。
图5是根据本发明的一实施例的硬件RC滤波器的实施例的电路图。
图6是根据本发明的一实施例的展示模拟显示的监视器的前视图。
具体实施方式
图1说明并入本发明的血氧定量法系统的实施例。传感器10包括红光LED和红外LED以及光电检测器。电缆12将它们连接到电路板14。LED驱动接口16提供LED驱动电流。从传感器所接收的光电流提供到I-V接口18。IR和红光电压接着提供到并入本发明的∑-Δ接口20。∑-Δ接口20的输出提供到微控制器22。微控制器22包括用于程序的闪存和用于数据的RAM存储器。血氧计还包括连接到闪存26的微处理器芯片24。最后，使用时钟28，且提供接口30以用于传感器10中的数字校准。独立主机32接收经处理的信息，且接收线34上的模拟信号以提供模拟显示。
现有技术的硬件中的解调
图2展示现有技术的用于产生模拟输出信号的电路的实例。在硬件通过电流到电压转换器(I-V)36和滤波器37中处理来自患者传感器的信号。接着在解调器38中解调红光信号和IR信号。通过滤波器39的第一通道和放大器40将红光信号提供给ADC 41。类似地，通过滤波器42的第二通道、放大器43和ADC 44提供IR信号。在ADC44的输入端从IR信号中获得模拟输出。
本发明的软件中的解调
图3展示本发明的实施例，其不在硬件中而是在软件中进行解调，因此模拟IR信号仅在硬件中不可用。在硬件通过电流到电压转换器45和滤波器46中处理来自患者传感器的信号，接着供应到ADC 47。在软件中，解调器将红光信号与IR信号分开。接着，将红光信号提供到软件滤波器49，且进一步处理(未展示)。类似地提供IR信号，使其通过软件滤波器50，且进一步处理(未展示)。因为软件滤波可引起显著的时间延迟，所以滤波器50之前的IR信号可转换回模拟形式。∑-Δ调制器51用作一个简单的数字到模拟转换器(ADC)。通过使用∑-Δ调制器，转换过程可较简单，且可快速完成。接着，仅需要在一简单RC滤波器52中对所得模拟信号进行滤波。
用于简单DAC的∑-Δ调制器和滤波器
图4是根据本发明的实施例的图3的Δ-∑调制器51的方框图。这个调制器优选用在图1的微控制器22上运行的软件来实施。线52上的输入是数字化传感器信号。在一优选实施例中，这个信号是红外(IR)信号，其与红光信号相对。选择红外是因为其通常是比红光信号更干净的信号。图4是实施以创建五分位信号(quintile signal)的二阶噪音整形(second order noise shaping)的不同等式的图形表示。在一个实施例中，实施不同等式的伪代码是：
X是线52上的输入
Y是线54上的输出
A、B和C是中间变量，其存储每206μS从一个迭代到下一循环的数据
A＝X-C+(2*B)
C＝B
if A＞then
Y＝1else
Y＝0
end if
B＝A-Y
end loop
这个代码在每206μS执行的循环中执行，因此输出(Y)是4845位/秒的位流，其平均值等于输入(X)。
线54上的输出优选4845Hz的位流。如图5中所示，此提供给硬件滤波器的输入60。这个滤波器包括电阻器62和64以及电容器66和68。这个滤波器对数字输出信号起作用以将其转换成模拟形式，以产生可提供给显示器的线70上的输出。这个滤波器是被动、二阶RC滤波器，在输出端上没有缓冲器。如果需要，那么可在显示前由主机系统完成任何缓冲。
图6展示脉冲血氧计监视器74上的模拟显示器72的实例。从图5的线70提供用于这个显示器的信号。
如所属领域的技术人员将了解，本发明可以其它特定形式体现，而不脱离本发明的本质特征。例如，Δ-∑调制器可具有不同于二阶的阶。可在硬件滤波器之前在软件中完成一些滤波，且可使用硬件滤波器的不同构形。因此，前述描述意在对以上权利要求书中所阐述的本发明的范畴进行说明而非限制。

Claims (9)

1.一种用于操作一生理监视器的方法，其包含：
检测一来自一患者的包括一生理波形的信号；
将所述波形转换成数字形式；
将所述波形施加给一Δ-∑调制器；和
对所述波形进行滤波以提供一模拟波形输出。
2.根据权利要求1所述的方法，其进一步包含解调所述波形的所述数字形式，其中所述Δ-∑调制器在所述解调后处理所述波形。
3.根据权利要求2所述的方法，其中所述滤波是由一耦合到所述Δ-∑调制器的一输出的硬件滤波器执行。
4.根据权利要求2所述的方法，其中所述Δ-∑调制器提供一单一位输出。
5.一种用于操作一血氧计的方法，其包含：
检测来自一患者的一包括一脉冲血氧定量法波形的信号；
将所述波形转换成数字形式；
将所述波形的所述数字形式解调成红光信号和IR信号；
将所述红光信号和所述IR信号中的一者施加给一软件Δ-∑调制器；
提供一来自所述Δ-∑调制器的单一位串行输出；
利用一硬件滤波器对所述单一位串行输出进行滤波；
6.一种生理监视器设备，其包含：
一输入端，其用于接收一来自一患者的包括一生理波形的信号；
一模拟到数字转换器，其用于将所述波形转换成数字形式；
一处理器，其包括一Δ-∑调制器，所述Δ-∑调制器经配置以将所述波形从数字形式转换成模拟形式；
一滤波器，其耦合到所述Δ-∑调制器的一输出端以用于对所述波形进行滤波。
7.根据权利要求6所述的血氧计设备，其中所述Δ-∑调制器是一产生一串行单一位输出的软件调制器。
8.根据权利要求6所述的血氧计设备，其中所述滤波器是一硬件RC滤波器。
9.一种血氧计设备，其包含：
一输入端，其用于接收一来自一患者的包括一脉冲血氧定量法波形的信号；
一模拟到数字转换器，其用于将所述波形转换成数字形式；
一处理器，其包括：
一解调器，其用于将所述波形分成红光信号和IR信号；和
一软件Δ-∑调制器，其经配置以通过产生以一串行单一位输出而将呈数字形式的所述红光信号和所述IR信号中的一者转换回一模拟信号；
一硬件RC滤波器，其耦合到所述Δ-∑调制器的一输出端以用于对所述波形进行滤波。
CNA2005800058567A 2004-02-25 2005-02-24 用于输出生理信号的模拟表示的δ－σ调制器 Pending CN1933770A (zh)

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