Multi wavelength high precision dynamic spectrum detection based on walsh orthogonal coded frequency division multiplexing

In this paper, a Walsh Orthogonal Coded Frequency Division Multiplexing (WFDM) method is proposed for the first time, and a dynamic spectrum (DS) detection system based on this method for non-invasive blood composition analysis is built. The WFDM method can greatly improve the channel utilization and reduce the bandwidth occupation of the DS detection system, making the system realize the collection of multi-wavelength PPG signals with high signal-to-noise ratio (SNR > 75 dB) and the extraction of high-quality DS. Compared with the spectrometer, the SNR of this DS detection system is improved by about 47-62 dB. In addition, this paper used this DS detection system to collect 193 valid patient samples, and established a calibration model between DS data and hemoglobin (HGB) levels in blood. The results shows that the correlation coefficients of the model calibration set and prediction set are 0.9201 and 0.9031, which are close to the clinical requirement.