DLL-based portable frequency-domain near-infrared spectroscopy system

Abstract

Near-infrared spectroscopy modulated in the 100 MHz regions is a technique for determining the absolute concentration of tissue composition. In the conventional frequency-domain spectroscopy method, an avalanche photodiode is used to operate only at high voltages, and signals are sent and received using fibers. As a result, the overall system is large, and each measurement requires a process to compensate for delays occurring in the system. This dissertation confirmed the possibility of a portable system by dramatically reducing the size of the system by using a small photodiode with a bandwidth similar to that of the Avalanche photodiode. And based on the integrated circuit, we implemented a system to eliminate the delay that can occur in the whole system.