Displacement Superposition Measurement Method Based on Microwave Multiple Reflections

Microwave displacement measurement techniques have been widely applied in areas such as vital signs monitoring and structural health monitoring due to their strong environmental adaptability. However, existing methods typically consider only direct reflections from the target surface. This letter proposes a multiple-reflection-based displacement superposition (MRDS) measurement method, which theoretically enables the measured signal to represent the linear superposition of displacements from all reflective surfaces when the motions are small. Two experiments were conducted to validate the method in both the frequency and time domains. The frequency-domain experiment demonstrated that MRDS yields the superimposed displacement signals of four membranes with distinct frequency responses, while the time-domain experiment showed that multiple reflections on the same target surface significantly improve signal-to-noise ratio (SNR) in microdisplacement measurement.