A phase-modulated sensor is a type of sensor that uses modulation of the phase of a signal to measure changes in a physical quantity. In such sensors, variations in the phase of the signal are directly related to the changes in the parameter being measured.
Key features and concepts associated with phase-modulated sensors include:
Phase modulation: Phase modulation involves changing the phase of a carrier signal in response to variations in the measured parameter. This modulation can be achieved through various means, such as altering the path length of an optical signal or changing the electrical properties of the signal.
Interferometric sensors: Many phase-modulated sensors are based on interferometric principles. Interferometry involves the interference of two or more coherent waves. Changes in the phase of these waves, caused by variations in the physical quantity being measured, lead to changes in the interference pattern, providing information about the parameter.
High sensitivity: Phase-modulated sensors are often chosen for applications requiring high sensitivity. Small changes in the phase of the signal can be detected and correlated with minute variations in the physical property being measured.
Applications: Phase-modulated sensors find applications in various fields, including optical sensing, acoustic sensing, and environmental monitoring. Common examples include interferometric sensors for measuring physical displacements, changes in refractive index, pressure, temperature, or other environmental factors.
Optical phase sensors: In the context of optics, interferometric sensors based on phase modulation are prevalent. For instance, in optical interferometry, changes in the optical path length can be detected through variations in the interference pattern, enabling the measurement of parameters like distance or refractive index.
Frequency-modulated continuous-wave radar: FMCW radar is an example of a phase-modulated sensor used in radar applications. In FMCW radar, the frequency of the transmitted signal is continuously varied, and the phase modulation is utilized to measure the range and velocity of targets.
Phase-modulated sensors are chosen for their ability to achieve high precision and sensitivity in measuring various physical parameters. The specific implementation of phase modulation depends on the type of sensor and the physical quantity under consideration.