Embodiments of the subject invention relate to a method and apparatus for detecting and/or analyzing respiratory motion of a patient, such as an animal or person. A specific embodiment can use a radar motion detector to measure and record respiratory movements at different parts of the body, using multiple identifiable markers, such as reflectors, positioned such that movements of the patient can be monitored by monitoring the movement of the markers. As an example, the markers can be attached to or worn by the patient, inserted into the patient (such as under the skin), or otherwise positioned in a known relation to a portion or surface of the patient. In an embodiment, the identifiable reflectors are transponders with different modulation codes (in frequency, phase, amplitude, or combinations thereof) on the reflected signal. A modulation frequency higher than the respiration rate can be used so that the multiple reflected signals received from the reflectors can be separated and respiration signal modulating on the reflected radio frequency signal from each reflector can be extracted and analyzed.
