Abstract
Highly accurate vibrometry and ranging are important topics in the industrialized economy. Wherever optical measurement technology fails due to its high prices and vulnerability within harsh environments, millimeter-wave (mmWave) radar technology is well suited. This article introduces a signal processing chain for ultrawideband frequency-modulated continuous-wave (FMCW) radar. It uses fast-time measurement to evaluate the instantaneous phase, thus allowing for spatially resolved sensing of multiple simultaneously vibrating radar targets, faster than the chirp rate. In order to accomplish this, a sophisticated error model and a calibration scheme were derived. We used three FMCW radar systems covering a broad range of the mmWave spectrum to demonstrate the signal processing approach. In contrast to the commonly used slow-time measurement principle, the highest detectable frequency was improved from 55 Hz to at least 16 kHz, which is the upper limit of the audio range. Up to 10 kHz could be measured with an underlying large-scale motion of 0.4 m/s, while the vibration displacement was at a minimum of 30 nm.
Highlights
W ITHIN the last few years, millimeter-wave frequency-modulated continuous-wave (FMCW) radar systems have been widely used for short-range measurements
We utilized three different radar systems, within a span from 68 to 250 GHz. These miniaturized ultrawideband FMCW radar systems are different in many ways
We proposed a sophisticated error model for highly accurate sensing using FMCW radar systems
Summary
W ITHIN the last few years, millimeter-wave (mmWave) frequency-modulated continuous-wave (FMCW) radar systems have been widely used for short-range measurements. Compared with unmodulated continuous-wave (CW) radar, which is widely used for radio wave vibrometry [16], [19], [32]–[38], fast-time vibrometry using FMCW radar generally enables simultaneous measurements of multiple vibrating radar targets by separating them within the range domain, which is the radial distance from the radar sensor to the. Rodenbeck et al [39] demonstrated a procedure for remote sensing of vibrating radar targets in motion using mmWave pulse-Doppler radar Their approach works in fast time, and they use continuous motion compensation techniques. They clearly illustrate that we could measure the vibration frequencies of multiple nonmoving but simultaneously vibrating radar targets in fast time. Matrices and column vectors are written as boldface upper (e.g., E) and lower cases (e.g., 0), respectively
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