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Multi-frequency phase-sensitive demodulation method based on improved median filtering

A demodulation method and frequency-phase technology, applied in the field of electrical impedance tomography, can solve the problems of weakening impact noise and signal distortion, and achieve the effects of removing influence, short delay time and simple operation

Inactive Publication Date: 2018-12-14
TIANJIN UNIV
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Problems solved by technology

[0006] Although the median filter can effectively weaken the impact noise, it also allows the value of the original normal sampling point to be replaced by the median value in its neighborhood, distorting the filtered signal and introducing new noise
Therefore, the median filter should not be directly applied to phase-sensitive demodulation in data acquisition systems

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Embodiment Construction

[0021] The multi-frequency phase-sensitive demodulation method based on the improved median filter of the present invention is described in conjunction with the accompanying drawings and embodiments:

[0022] Such as figure 1 As shown, it is a block flow diagram of the multi-frequency phase-sensitive demodulation method based on the improved median filter of the present invention. The concrete implementation steps of this method are as follows:

[0023] (1) Obtain the multi-frequency measurement signal y(k) composed of P sinusoidal signal components through high-speed A / D sampling, and its mathematical form can be expressed as:

[0024]

[0025] Among them, A i , f i with are the amplitude, frequency and phase of the i-th signal component, n(k) represents the impact noise, N i Indicates the number of sampling points of the i-th signal component in a sampling period.

[0026] (2) Construct a signal matrix according to the periodicity of the multi-frequency signal.

...

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Abstract

The present invention relates to a multi-frequency phase-sensitive demodulation method based on improved median filtering. The method comprises the following steps of: obtaining a digital quantity ofdetected multi-frequency signals through A / D sampling, and performing temporary storage of the digital quantity of the detected multi-frequency signals in a cache module; according to the periodicityof the detected multi-frequency signals, converting the cached digital signals to an M*Nc signal matrix, wherein M is the quantity of the signal sampling periods, and Nc is the quantity of the sampling points in one sampling period; taking each row of elements of the signal matrix, wherein each row of elements forms one M*1 vector to construct Nc rows of vectors; performing median filtering of each row of vectors to obtain the signal vectors after filtering; and performing digital phase-sensitive demodulation according to the signal vectors after filtering to obtain the amplitude and phase information of each frequency component signal.

Description

technical field [0001] The invention belongs to the technical field of electrical impedance tomography, and in particular relates to a multi-frequency phase-sensitive demodulation method. Background technique [0002] Electrical impedance tomography (Electrical Impedance Tomography, EIT) is a process tomography technology based on the sensitive mechanism of electrical characteristics. This technology uses electrical detection methods to invert the distribution of electrical characteristics of objects in the sensitive field, and then obtains the measured field. Media distribution within the domain. Compared with traditional ray (x-ray, pet)-based visual detection methods, EIT has the advantages of non-invasiveness, no radiation, fast response speed, low price, etc., and can realize long-term and real-time monitoring of the measured object. In particular, the data acquisition speed of the EIT system can reach about 500 frames per second, which is much higher than the current ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01R27/26G01R27/02
CPCG01R27/02G01R27/2617
Inventor 岳士弘郝振华
Owner TIANJIN UNIV
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