CN103654857A - Fetal heart signal acquisition device - Google Patents

Abstract

The invention discloses a fetal heart signal acquisition device, which comprises an ultrasonic Doppler probe connected in sequence, an amplifier circuit, an analog/digital converter, a data processing unit, a wireless communication unit and a remote terminal device, the ultrasonic Doppler The Le probe includes a receiving chip and a transmitting chip. The receiving chip is a circle, and the transmitting chip is a ring concentric with the receiving chip. The outer circle of the receiving chip is seamlessly connected with the inner circle of the transmitting chip. The device uses a ring-shaped ultrasonic Doppler probe, which can better receive the sound waves reflected on the receiving chip, and uses wavelet transform to effectively denoise the fetal heart signal, so that the cycle performance of the fetal heart signal can be well reflected. Come out, so as to more accurately calculate the fetal heart rate, to achieve the purpose of monitoring the health status of the fetus. The device has the advantages of simple structure, low cost and convenient and intelligent operation process.

Description

A fetal heart signal acquisition device

technical field

The invention relates to a fetal heart signal acquisition device, in particular to a wavelet transform-based fetal heart signal acquisition device, which belongs to the field of acoustic sensors and signal processing.

Background technique

Fetal heart signal is an important physiological and pathological information for judging the health status of the fetus in the mother's body, especially the collection and monitoring of fetal heart signal during the perinatal period can help improve the quality of fetal delivery and reduce the rate of fetal malformation and mortality. , Fetal heart signal acquisition and monitoring is of great significance in clinical diagnosis. Using ultrasonic Doppler probe to detect fetal heart rate signal is an important method to obtain fetal heart rate, but the ultrasonic echo is a non-stationary random signal, in which the useful signal is a low-frequency signal, and the noise signal is a high-frequency signal, and the fetal heart signal has Weak signal, low signal-to-noise ratio, non-stationarity and other random characteristics, therefore, we need to eliminate the high-frequency amount represented by the noise, and retain the low-frequency amount that reflects the useful information of the signal.

In order to extract useful low-frequency signals, the traditional denoising method is to pass the signal interfered by noise through a filter, such as a band-pass filter, to filter out the noise frequency components, but the traditional linear filtering method cannot It solves the contradiction between protecting the local characteristics of the signal and suppressing the noise well. The fetal heart signal processed by traditional filtering not only does not greatly improve the signal-to-noise ratio, but also the most important transient point position information in signal analysis is also blocked. blurred out. Moreover, a specific filter needs to be designed to match the specific signal-to-noise data, which correspondingly increases the equipment cost.

Contents of the invention

The object of the present invention is to provide a fetal heart signal acquisition device, which can effectively capture and denoise the fetal heart signal, and reduce the equipment cost.

In order to achieve the above object, the technical scheme adopted in the present invention is as follows:

A fetal heart signal acquisition device includes an ultrasonic Doppler probe with a receiving chip and a transmitting chip, the receiving chip is a circle, the transmitting chip is a ring concentric with the receiving chip, and the receiving chip is The outer circle seamlessly connects with the inner circle of the emitting chip.

Further, the fetal heart signal acquisition device also includes an amplification circuit, an analog-to-digital converter, and a data processing unit sequentially connected to the ultrasonic Doppler probe, and the data processing unit is used for amplifying and analog-to-digital conversion The final signal is denoised by wavelet transform.

Preferably, the wavelet transform denoising processing method is to use db6 wavelet function to perform three-layer wavelet decomposition on the amplified and analog-to-digital converted signal, remove the high-frequency part of the signal and reconstruct the low-frequency part.

Further, the fetal heart signal acquisition device also includes a wireless communication unit and a remote terminal device, the wireless communication unit is connected to the data processing unit, and the remote terminal device is connected to the wireless communication unit with a wireless signal for The fetal heart rate signal processed by the data processing unit is received.

After adopting the above scheme, a fetal heart signal acquisition device of the present invention adopts a ring-shaped ultrasonic Doppler probe, which can better receive the sound waves reflected on the receiving chip, and use wavelet transform to effectively remove the fetal heart signal. Noise processing, so that the cycle performance of the fetal heart signal is well reflected, so that the fetal heart rate can be calculated more accurately, and the purpose of monitoring the fetal health status can be achieved. The device has the advantages of simple structure, low cost and convenient and intelligent operation process.

Description of drawings

Fig. 1 is a system structure block diagram of a fetal heart signal processing device based on wavelet transform in the present invention.

Figure 2 is a structural diagram of a conventional probe.

Fig. 3 is a structure diagram of the ultrasonic Doppler probe of the present invention.

Fig. 4 is a waveform diagram of the fetal heart signal filtered by a traditional band-pass filter.

Fig. 5 is a waveform diagram of the fetal heart signal after the wavelet analysis of the present invention.

Detailed ways

The technical solutions of the present invention will be described in further detail below in conjunction with the accompanying drawings.

As shown in Figure 2, the transmitting chip and the receiving chip of the traditional ultrasonic probe are very close, and a part of the transmitting signal will always be directly coupled to the receiving chip, so the ultrasonic signal received by the receiving chip is not completely reflected by the viscera. The echo with Doppler frequency shift, the fetal heart signal received by the receiving chip is noisy, which will have an impact on the health status monitoring of the fetus.

As shown in Fig. 1 and Fig. 3, a kind of fetal heart signal processing device of the present invention comprises the ultrasonic Doppler probe that has receiving chip and transmitting chip, and described receiving chip is a circle, and described transmitting chip is a The concentric ring of the receiving chip, so that the received ultrasonic sound field has a large area and forms a fan shape, which can greatly improve the ability to capture fetal heart sound signals, so that it can be used for long-term monitoring, and the outer circle of the receiving chip is the same as that of the transmitting chip. The inner circle is seamlessly connected.

The fetal heart signal acquisition device also includes an amplification circuit, an analog/digital converter, and a data processing unit sequentially connected to the ultrasonic Doppler probe, and the data processing unit is used for amplifying and analog-to-digital converted signals Carry out wavelet transform denoising processing.

The device also includes a wireless communication unit and a remote terminal device, the wireless communication unit is connected to the data processing unit, the remote terminal device is connected to the wireless communication unit with a wireless signal, and is used to receive the processed fetal heart rate information, and the remote terminal device It can be mobile phone, tablet computer, etc., the data processing unit can be CPU, MCU, etc., and the wireless communication unit can be GSM, CDMA, 3G, etc.

A method for realizing a wavelet transform acquisition device: place an ultrasonic Doppler probe on the abdomen of a pregnant woman to collect fetal heart sound signals, the ultrasonic Doppler probe amplifies the collected signal through an amplification circuit, and the amplified signal is converted by analog/digital conversion The digital signal is converted into a digital signal and sent to the data processing unit. The data processing unit performs filtering and denoising processing on the signal through the wavelet transform algorithm. Finally, the processed signal is sent to the remote terminal device through the wireless communication unit, and the remote terminal device performs post-processing. Processing: the signal is filtered and denoised by the wavelet transform algorithm, specifically, using the db6 wavelet function to perform 3-layer wavelet decomposition on the amplified and analog-to-digital converted fetal heart signal, removing high-frequency parts and performing low-frequency part Refactor to get useful signals. The signal after wavelet transformation is closer to the original heartbeat signal of the fetus, and the prediction of the health status of the fetus is more accurate and reliable.

As shown in Figure 4, it is the fetal heart signal waveform diagram filtered by the traditional band-pass filter, the vertical axis is the amplitude, and the horizontal axis is time, the parameters of the band-pass filter are set as follows: the bandwidth is 30-250Hz, the data sampling rate It is 2000Hz, and the attenuation coefficient is 80dB. It adopts FIR digital filter and adds Hamming window to provide linear phase.

As shown in Figure 5, it is the waveform diagram of the fetal heart signal after wavelet analysis of the present invention, wherein: a1 is the signal amplitude after the wavelet reconstruction for the first time, and a2 is the signal amplitude after the wavelet reconstruction for the second time , a3 is the signal amplitude after the third wavelet reconstruction, and the horizontal axes of a1, a2, and a3 are time. According to the characteristics of weak signal, low signal-to-noise ratio, and non-stationary randomness of the fetal heart signal, using the multi-resolution analysis characteristics of wavelet, selecting the appropriate wavelet base, optimizing the number of decomposition layers, and dividing the high-frequency part and low-frequency part of the fetal heart signal Separate and remove the high-frequency part to obtain the low-frequency part containing all fetal heartbeat information, and then reconstruct the signal of the low-frequency part, which can greatly improve the signal-to-noise ratio. In order to ensure the effectiveness, smoothness and regularity of the processing, the db6 wavelet function is selected, which has the advantages of biorthogonality, compact support, and regularity. The regularity of the dbN wavelet system increases with the increase of the serial number N, which can avoid Signal phase shifting to obtain better smoothing effect during signal reconstruction. The choice of wavelet decomposition layers is also very important. The larger the number of wavelet decomposition layers, the longer the length of the filter and the better the filtering performance, but the longer the signal processing delay, the worse the time domain positioning. The number of wavelet decomposition layers is mainly based on its frequency band division characteristics, and is selected according to the frequency of the useful signal. In the present invention, the data sampling rate is 2000 Hz, and the fetal heart rate data is decomposed by three layers of wavelet through theoretical derivation and experiments to remove unnecessary high frequency part, and reconstruct the low frequency part of the fetal heart signal. It can be seen from Figure 5 that after the three-layer decomposition and low-frequency reconstruction of the original fetal heartbeat signal, the low-frequency part containing all the fetal heartbeat information is obtained, and has less noise, the noise of the signal is greatly reduced, and the signal has obvious periodic. However, the signal filtered by the band-pass filter in Figure 4 has certain periodicity, but the noise and interference are still relatively large, and the signal-to-noise ratio is very poor. Therefore, wavelet transform is an effective denoising method for non-stationary signals.

The above embodiments are only to illustrate the technical ideas of the present invention, and can not limit the protection scope of the present invention with this. All technical ideas proposed in accordance with the present invention, any changes made on the basis of technical solutions, all fall within the protection scope of the present invention. Inside.

Claims (4)

1. A fetal heart signal acquisition device, comprising an ultrasonic Doppler probe with a receiving chip and a transmitting chip, characterized in that: the receiving chip is a circle, and the transmitting chip is a concentric circle with the receiving chip Ring, the outer circle of the receiving chip is seamlessly connected with the inner circle of the transmitting chip. 2. a kind of fetal heart signal acquisition device as claimed in claim 1, is characterized in that: also comprise the amplifying circuit that is connected with described ultrasound Doppler probe successively, analog/digital converter, data processing unit, described data The processing unit is used to perform wavelet transform denoising processing on the amplified and analog-to-digital converted signal. 3. a kind of fetal heart signal acquisition device as claimed in claim 2, is characterized in that: described wavelet transform denoising processing method is, utilizes db6 wavelet function, carries out 3 layers of wavelets to the signal after amplification and analog-to-digital conversion Decomposition, remove the high frequency part of the signal and reconstruct the low frequency part. 4. A kind of fetal heart signal acquisition device as claimed in claim 2 or 3, it is characterized in that: also comprise wireless communication unit, remote terminal equipment, described wireless communication unit is connected with described data processing unit, and described remote terminal The device is in wireless signal connection with the wireless communication unit.

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