Orthogonal Frequency Division Multiplexing (OFDM) technique is obtained significant attention in radar applications for its interference resilience property. In this paper, Fractional Fourier Transformation (FRFT) and phase analysis techniques are proposed to enhance ranging accuracy of an OFDM Radar. A proof-of-concept radar is built and tested at 79 GHz and a range accuracy of 20 µm at 5 MHz measurement rate was measured. The range accuracy is 500 times higher compared with the application of fast Fourier transformation (FFT) method.
An enhanced accuracy random binary phase modulated radar is proposed. It can be used in high accuracy monitoring in manufacturing. Compared with the traditional high accuracy radar using frequency modulated continuous wave (FMCW), the proposed radar system can be used in a multiuser scenario without occupying more bandwidth. A two-step distance estimation method is introduced to estimate the distance. First, the distance estimation accuracy is narrowed down to a half carrier wavelength by analyzing the envelope of the phase modulated signal. Then the carrier phase information increases the distance accuracy to several micrometers. An equalization method is introduced to solve the I/Q imbalance problem. The proposed radar system is demonstrated at a carrier frequency of 80 GHz with a bandwidth of 2 GHz. The measured distance error was within ±7 μm. In addition, a high measurement repetition rate of 500 kHz was reached which is suitable for real-time monitoring in automatic manufacturing.
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