An mmWave Sensor for Real-Time Monitoring of Gases Based on Real Refractive Index

Abstract

We propose a millimeter-wave (mmWave) sensor to monitor gases and aerosols based on time-of-flight (ToF), thus, on the real refractive index. It utilizes an ultrawideband frequency-modulated continuous-wave (FMCW) radar operating from 72 to 92 GHz at a sampling rate of 500 Hz. Also, we introduce a model for simulation of the refractive index of arbitrary gases at mmWave frequencies using molecular spectroscopic data. Simulations then allow the identification of the respective gas under test. We characterized the performance of the sensor regarding the refractive index within various experiments. The precision is 0.027 ppm, and the 20-h long-term stability is better than 0.2 ppm. The linearity is at least 1.5 ppm. Due to sophisticated temperature compensation, the temperature drift is less than 10 ppm for 30 K. Since the sensor is accurate, precise, and robust, it is perfect for in-process real-time monitoring and classification of gases or aerosols in the industry.

Radar-Enabled Millimeter-Wave Sensing of Fire Interactions

“…As before, the signal is analyzed via phase and then compared with the previous measurements without fire. The study [8] shows that even the smallest changes in the chemical composition of the exhaust air from fires can be detected with FMCW radar sensors. Based on high precise phase evaluation of FMCW radar measurements, these changes can be visualized.…”

Recent Advances in mmWave-Radar-Based Sensing, Its Applications, and Machine Learning Techniques: A Review

“…This study includes a model for the echo signal of the NLOS target by considering the multipath effect and the weak target echo signal issues. The detection and classification of gases and aerosols have been implemented in [72]. Detecting the vibrational target objects by modifying shaking frequencies and assessing the performance is studied in [10].…”

Distance Measurement Using mmWave Radar: Micron Accuracy at Medium Range

“…The received signal is downconverted by using the transmit signal, i.e., the received signal is deramped, producing a signal at an intermediate frequency (IF) s if (t). Generally, one can say that the FMCW radar system serves as a frequency-domain reflectometer [24], measuring the frequency response of the radar path H ( f ) as…”

“…Most commonly, standard resolution methods are used and the ToF is obtained from the pulse position. However, using the pulse phase is beneficial in terms of noise, interference, and micromotions [2], [14], [24], [36]- [38], but as the phase is ambiguous in general, it requires more sophisticated signal processing.…”

“…It also increases the signal-to-noise ratio (SNR). The filter is determined once during initialization through time-gating of the radar echo (see also [14], [24]).…”