A method for fast acquisition of multi-frequency point bioelectrical impedance

Abstract

The invention discloses a quick acquiring method for multi-frequency-point bioelectrical impedance. A multi-frequency-point composite excitation source Vin is realized based on a DDS (direct digital synthesizer) principle by means of FPGA (field-programmable gate array) programming, the composite excitation source Vin is loaded onto reference resistance Rref and to-be-tested organism electric impedance Zx simultaneously, corresponding amplitudes Ampref and Ampx and phase angles Degref and Degx of the Vref and Vx on frequency points can be acquired accurately by reasonably selecting sampling frequency fs and points N of DFT (digital Fourier transform) and by only performing DFT on the Vref and Vx on the several needed frequency points, and further amplitudes of the to-be-tested organism electric impedance Zx on the frequency points are acquired. The quick acquiring method has the advantages of high impedance acquisition accuracy, small operation amount, high anti-jamming capability, short scanning time and the like.

Description

technical field [0001] The invention relates to the field of biological characteristic signal extraction methods, in particular to a method for rapidly acquiring multi-frequency point bioelectrical impedance. Background technique [0002] Bioelectrical impedance technology: a non-invasive detection technology that uses the electrical characteristics of biological tissues and organs to extract biological and physiological information. It uses the electrodes placed on the body surface to input a weak detection current to the organism, and then measures the voltage change of the appropriate part, so as to obtain the electrical impedance transformation of the relevant tissues or organs, so as to obtain physiological and pathological information. This technique is widely used in modern medicine because of its non-invasive, safe, and low-cost advantages, mainly including: reactance blood flow diagram, human body impedance imaging, and body composition measurement. [0003] Bioele...

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Problems solved by technology

[0003] Bioelectrical impedance measurement technology has experienced the evolution of measurement technology from direct current to alternating current, from pure resistance to complex impedance, and from single-frequency point to multi-frequency point. However, the current mainstream multi-frequency bioelectrical impedance measurement method still belongs to time-sharing single-frequency The measurement method, which scans the impedance of the organism successively from low frequency to high frequency, takes a long time, and because the physiological state of the organism is affected by the heartbeat and blood flow, the time-sharing single-frequency measurement method cannot accurately reflect the biological state at a certain moment. Spectrum information of bioimpedance

[0004] The Chinese patent application No. CN103705236 published on April 9, 2014 discloses a method for synchronous rapid measurement of bioelectrical impedance spectrum, which uses FPGA to realize a multi-frequency synchronous excitation signal source based on Walsh function and the corresponding bioimpedance The anti-acquisition method, but because the Walsh function signal has some disadvantages compared with the traditional sinusoidal signal, its autocorrelation is not ideal, and the sidelobe value of the spectrum is large, so that on the one hand, false synchronization will be generated, and on the other hand, the method can obtain excitation The frequency accuracy of the source is limited, so it is necessary to increase the number of DFT points when extracting impedance, and at the same time increase the correction algorithm to solve the error caused by the DFT fence effect, which will greatly increase the amount of computation and complexity of the system

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