Phase error elimination method of digital demodulation system for bio-impedance measurement

Abstract

The invention belongs to the technical field of bio-impedance measurement, and particularly discloses a phase error elimination method of a digital demodulation system for bio-impedance measurement. The method particularly comprises the following steps: initializing conditional variables of a system and the cycle length of input signals; judging whether the system is started; starting up a cycle timer and an ADC simultaneously; delaying the cycles of digital signals obtained by conversion by the ADC within the time period of T(2n-1); and detecting and judging whether the number of cycles is an even number, and outputting the digital signals. Therefore, the sampling time of two groups of cycle signals is subjected to cycle delay by a cycle delay mode, so that the initial phases of sampling of the two groups of same cycle signals are equal in value, and the interval for sampling the two groups of signals by the ADC is integer multiples of the cycle of the input analog signals during digital demodulation, thereby achieving the aims of eliminating the problem of phase error caused by different phases of the two groups of signals acquired by the ADC and improving the operation accuracy of acquired data.

Description

technical field [0001] The invention belongs to the technical field of biological impedance measurement, and in particular relates to a phase error elimination method of a digital demodulation system suitable for biological impedance measurement. Background technique [0002] In bioimpedance measurement, the impedance of the measured body is usually measured by adding an excitation current to measure the voltage of the measured tissue. In actual measurement, two sets of signals are usually measured: the voltage signal and the current signal of the measured tissue. The impedance of the measured tissue is obtained through Ohm's law R=U / I. If digital demodulation is used, the ADC may have uneven acquisition intervals when acquiring the two sets of signals, resulting in phase errors in the acquired two sets of signals. Contents of the invention [0003] In view of the deficiencies in the prior art above, the purpose of the present invention is to provide a digital demodulation...

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Problems solved by technology

[0003] In view of the deficiencies in the above-mentioned prior art, the purpose of the present invention is to provide a digital demodulation system with low cost, accurate operation, and an even interval between the two sets of signal acquisitions by the ADC during the digital demodulation process, which is used to measure the phase error of the digital demodulation system for biological impedance. The elimination method solves the problem of the phase error of the two sets of signals collected by the ADC due to the different phases

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