With the continuous development of modern industry, high-precision dynamic monitoring systems are essential to ensure the safety and efficiency of production. Therefore, the terahertz radar system based on frequency modulation continuous wave (FMCW) was studied in this work, aiming at realizing high-precision dynamic monitoring of coal levels in coal bunkers. The system adopts the FMCW method to measure the target distance by transmitting continuous linear frequency modulation signals and using the frequency difference and time delay between the received signal and the transmitted signal. The frequency selection algorithm is combined with the phase estimation algorithm, and the spectrum is refined by Zoom-FFT algorithm to improve the range resolution. The phase estimation algorithm is used to supplement and improve the ranging accuracy to ensure the reliability of the ranging results. To verify the feasibility of the system, field tests were conducted at 120-124 GHz frequencies and 4 GHz bandwidths. The system has a maximum operating range of 50 m, a beamwidth of 4 degrees, and a theoretical range resolution of up to 0.5 mm. By integrating optimization algorithm, the terahertz radar system can realize high-precision dynamic monitoring of coal level in the bunker, and show excellent anti-interference ability and stability, showing great practical application value.
The loss characteristics of the low-frequency terahertz band (0.325THz-0.50 THz) were tracked during sample aging from perspective of loss tangent, amplitude and phase. The attenuation of signal not only increases with the frequency but also with the aging time. Phase decrease with frequency and is also related to aging time. But the change of rate is almost same for all samples. Besides, it is observed that the loss tangent increases with the frequency, which will also increase with the aging time. Thus, investigators may get a deep understanding of rubber’s remaining life by analyzing optical parameter in terahertz range.
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