Blood Phantom Concentration Measurement Using An I-Q Receiver Design

Abstract

Near-infrared spectroscopy has been used as a non-invasive method of determining concentration of chemicals within living tissues of living organisms. This method employs LEDs of specific frequencies to measure concentration of blood constituents according to the Beer-Lambert Law. One group of instruments (frequency domain instruments) is based on amplitude modulation of the laser diode or LED light intensity, the measurement of light adsorption and the measurement of modulation phase shift to determine light path length for use in Beer-Lambert Law. This paper describes the design and demonstration of a frequency domain instrument for measuring concentration of oxygenated and de-oxygenated hemoglobin using incoherent optics and an in-phase quadrature (I-Q) receiver design. The design has been shown to be capable of resolving variations of concentration of test samples and a viable prototype for future, more precise, tools.