JP2017169870A - Cardiopulmonary function measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a product cost, eliminate complexity in using algorithm or the like for selecting any one signal of I/Q signals, and stably measure a heart rate and a respiration rate.SOLUTION: A cardiopulmonary function measuring apparatus: converts A/D of I/Q signals output from a Doppler sensor 1; in a case of heartbeat measurement, causes the signals after the A/D conversion to pass through first filters 5a and 5b composed of BPFs for passing a frequency range of the heartbeat (in a case of respiration measurement, causing the signals to pass LPF or BPF with the frequency range of respiration defined as a pass band); inputs the I/Q signals in a heartbeat measuring part 6; performs FFT operation, for example, with the I signal defined as real part data and the Q signal defined as imaginary part data to calculate vibration amplitude; and calculates a heart rate (a respiration rate in a respiration measuring part) from the frequency of a peak value of the vibration amplitude.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a cardiopulmonary function measuring device, and more particularly to a cardiopulmonary function measuring device that measures a heart rate and a respiratory rate using a Doppler sensor using a microwave.

  5 to 7 show examples of devices for measuring cardiopulmonary function using a conventional microwave Doppler sensor. In FIG. 5, reference numeral 1 denotes a Doppler sensor, 3 denotes an LPF (low-pass filter), 4 is an AD (analog / digital) converter, 5 is a BPF (band pass filter) having a frequency range of heartbeats as a pass band, and 21 has an FFT (Fast Fourier Transform) operation unit to measure a heart rate. The heartbeat measuring unit 22 is a zero setting unit that sets 0 as imaginary part data.

  In the apparatus of FIG. 5, the output of the Doppler sensor 1 is AD-converted, and the signal after AD conversion is passed through the BPF 5 having a frequency characteristic 31 that passes only the heartbeat frequency range Hr as shown in FIG. The heart rate is measured by performing FFT calculation (frequency conversion) in the measurement unit 21. That is, in the heartbeat measuring unit 21, while the output of the BPF 5 is used as real part data, the FFT calculation is performed using the 0 output from the zero setting unit 22 as imaginary part data. The heart rate is calculated from

  6 and 7 are examples of a cardiopulmonary function measuring apparatus using a Doppler sensor having two output signals I and Q. In FIG. 6, one of the I and Q signals output from the Doppler sensor 1 is selected. A selector 2 is provided. In this example, the selector 2 selects either I or Q signal, and the heart rate is measured based on the selected signal.

In the example of FIG. 7, two systems for processing each of the I signal and the Q signal are arranged, and LPFs 3a and 3b, AD converters 4a and 4b, BPFs 5a and 5b, heart rate measuring units 21a and 21b, and a zero setting unit. 22a and 22b are provided, and finally a selector 2 for selecting one of the outputs of the heart rate measuring units 21a and 21b is arranged. According to this example, both I and Q signals are subjected to an FFT operation, and one of the two results is output as a heart rate.
In the cardiopulmonary function measuring apparatus, the respiratory rate is also measured.

Japanese Patent No. 5776817 Japanese Patent No. 5432254 Japanese Patent No. 5333427

  However, as shown in FIG. 5, in the measurement using the 1 (single) output Doppler sensor 1, the output signal of this sensor may become unstable, and the Doppler sensor outputs two signals of I and Q. In the measurement with the configuration as shown in FIG. 6 using the algorithm, an algorithm for selecting a stable signal of either I or Q is required before the FFT calculation, which is complicated. In the configuration as shown in FIG. 7, two measurement units (FFT calculation units) 21a and 21b are required corresponding to each of the I and Q signals, the product cost is doubled, and the results of the two FFT calculations. Therefore, there is a problem that an algorithm for deriving a correct value is required, which is complicated.

  The present invention has been made in view of the above problems, and its object is to reduce the product cost by performing one FFT operation even when a Doppler sensor having two output signals I and Q is used. It is possible to stably measure the heart rate and the respiratory rate without using the algorithm for selecting one of the signals I and Q and the algorithm for deriving the correct value from the two FFT calculation results. An object of the present invention is to provide a cardiopulmonary function measuring apparatus that can be used.

  In order to achieve the above object, the invention according to claim 1 is a cardiopulmonary function measuring apparatus that measures cardiopulmonary function by a Doppler sensor that outputs two I and Q signals having a phase difference. An A / D converter for digital conversion and an output signal of the A / D converter are input, and a band pass filter that passes a heart rate frequency range in heart rate measurement, or a low pass filter that passes a breath frequency range in breath measurement A first filter composed of a bandpass filter and one of the I and Q signals passed through the first filter is a real part, the other is an imaginary part, and a Fourier transform operation using the real part and the imaginary part is performed. A measurement unit that includes a Fourier transform calculation unit that obtains amplitude by performing measurement, and that measures the heart rate or respiration rate from the frequency of the peak value of the output amplitude from the Fourier transform calculation unit , Characterized in that the provided.

According to the above configuration, I and Q signals having different phases (with a phase difference of 90 degrees) are output from the Doppler sensor, and when these I and Q signals are AD converted and a heart rate is measured, When measuring a BPF (band pass filter) having a frequency range as a pass band and respiration, the filter is passed through a first filter made of LPF (low pass filter) having a frequency band of respiration as a pass band or a BPF, and then I , Q signals are input to the measurement unit as real part data and the other as imaginary part data.
In this measurement unit, the signal amplitude (power) is obtained by performing fast Fourier transform based on a complex function using the real part and imaginary part, and the heart rate or respiration rate is measured from the frequency of the peak value of this amplitude. Is done.

According to the configuration of the present invention, even when a Doppler sensor having two output signals, I and Q, is used, measurement is performed by one FFT calculation process in which one of the I and Q signals is a real part and the other is an imaginary part. Product costs can be reduced. Further, unlike the conventional method, the heart rate and the respiratory rate are stably measured without the complexity of using an algorithm for selecting one of the signals I and Q and an algorithm for deriving a correct value from two FFT calculation results. There is an effect that it becomes possible.
Furthermore, the present invention can be used as a device for measuring heart rate and respiration rate without contact.

It is a circuit block diagram which shows the structure of the heart rate measurement in the cardiopulmonary function measuring device of the Example which concerns on this invention. It is a circuit block diagram which shows the structure of the respiration rate measurement in the cardiopulmonary function measuring apparatus of an Example. It is a graph which shows the filter characteristic of BPF used by the heart rate measurement of an Example. It is a graph which shows the filter characteristic of LPF and BPF used by the respiration measurement of an Example. It is a circuit block diagram which shows the structure of the cardiopulmonary function measuring apparatus using the conventional 1 output Doppler sensor. It is a circuit block diagram which shows one example of the cardiopulmonary function measuring apparatus using the conventional Doppler sensor of I and Q output. It is a circuit block diagram which shows the other example of the cardiopulmonary-function measuring apparatus using the conventional Doppler sensor of I and Q output.

FIG. 1 shows a configuration for measuring a heart rate in the cardiopulmonary function measuring apparatus according to the embodiment. In this embodiment, reference numeral 1 denotes a Doppler sensor that outputs two signals I and Q, 3a. , 3b are LPFs (low-pass filters) that are anti-aliasing filters, 4a and 4b are AD (analog / digital) converters, and 5a and 5b are first BPFs (band-pass filters) that pass the frequency range of heartbeats in heart rate measurement. The filter 6 inputs the I signal output of the first filter 5a as real part (real part) data, inputs the Q signal output of the first filter 5b as imaginary part (imaginary part) data, and performs FFT (Fast Fourier Transform). It is a measurement unit that counts the heart rate by performing calculations.
FIG. 3 shows the characteristics of the BPF of the first filters 5a and 5b. The BPF has a filter characteristic 31 having a heartbeat frequency range Hr as a pass band.

According to the cardiopulmonary function measuring apparatus having the above configuration, the two I and Q signals output from the Doppler sensor 1 pass through respective LPFs (anti-aliasing filters) 3a and 3b, and then are AD converted by the AD converters 4a and 4b. The converted and AD-converted signals are passed through first filters (BPF) 5a and 5b whose passband is the heartbeat frequency range Hr.
The I signal output from the first filter 5a is input to the heart rate measurement unit 6 as real part data of a complex function, and the Q signal output from the first filter 5b is input as imaginary part data of a complex function. Is done. In the heartbeat measuring unit 6, by performing FFT calculation, the amplitude (power) of the signal is calculated, and the heart rate is obtained from the frequency of the peak value.

FIG. 2 shows a configuration for measuring the respiratory rate in the cardiopulmonary function measuring apparatus of the embodiment. In this example, as in FIG. 1, the Doppler sensor 1, LPFs 3a and 3b as anti-aging filters, AD converters 4a and 4b are provided, and the first filters 7a and 7b made of LPF or BPF that pass the breathing frequency range, and the I signal output of the first filter 7a is used as real part data, and the first filter A respiration measurement unit 8 is provided that counts the respiration rate by inputting the Q signal output of 7b as imaginary part data and performing an FFT operation.
FIG. 4 shows the LPF or BPF characteristics of the first filters 7a and 7b. The LPF has a filter characteristic 32 having a pass band up to the respiration frequency range Br. It has a filter characteristic 33 having a pass band in the frequency range Br.

  According to the cardiopulmonary function measuring apparatus having the above configuration, the I and Q signals output from the AD converters 4a and 4b are the first filters (LPF / BPF) 7a and 7b whose pass band is the respiratory frequency range Br. The I signal from the first filter 7a is input to the respiration measuring unit 8 as real part data and the Q signal from the first filter 5b is input as imaginary part data. In the respiration measuring unit 8, the amplitude (power) of the signal is calculated by performing FFT calculation (frequency conversion), and the respiration rate is obtained from the frequency of the peak value.

In the above embodiment, the I signal is real part data and the Q signal is imaginary part data, but the reverse is also possible, and the Q signal may be real part data I and the signal may be imaginary part data.
Moreover, although it demonstrated as a structure which measures a heart rate and respiration separately, in fact, the common structure, such as LPF 3a, 3b, AD converter 4a, 4b from Doppler sensor 1, may be one system.

1 ... Doppler sensor, 2 ... selector,
3, 3a, 3b ... LPF (anti-aliasing filter),
4, 4a, 4b ... AD converter,
5, 5a, 5b ... heartbeat first filter (BPF),
6, 21, 21a, 21b ... heart rate measuring unit,
7a, 7b ... 1st filter for breathing (LPF / BPF),
8: Respiratory measurement unit.

Claims (1)

In a cardiopulmonary function measuring apparatus that measures cardiopulmonary function by a Doppler sensor that outputs two I and Q signals having a phase difference,
An A / D converter for analog-digital conversion of the I and Q signals;
A first filter comprising a band-pass filter that inputs an output signal of the A / D converter and passes a heart rate frequency range in heart rate measurement; a low-pass filter or a band-pass filter that passes a breath frequency range in breath measurement; ,
One of the I and Q signals passed through the first filter is a real part, the other is an imaginary part, and a Fourier transform operation part for obtaining an amplitude by performing a Fourier transform operation using the real part and the imaginary part is provided. A cardiopulmonary function measuring apparatus comprising: a measuring unit that measures a heart rate or a respiratory rate from a frequency of a peak value of an output amplitude from the Fourier transform calculating unit.

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