Studies on MIMO OFDM radar for automotive application

Abstract

Rapidly-growing attentions have been paid to automotive radar sensors over the past decade, as the cost of the hardware has drastically decreased with the advent of advanced semiconductor technologies. Better performance capabilities in range and angular resolutions of radar sensors are competitively required, as they are very important features not only to detect objects but also to recognize them in optical camera or light detection and ranging (LiDAR) applications. As many antennas and transceiver chains in multiple-input multiple-output (MIMO) radar systems are necessary to obtain high angular resolutions, virtual receive array (VRA) methods are widely adopted to synthesize a large aperture size effectively for high angular resolution. Orthogonal frequency-division multiplexing (OFDM) radar as a digital-oriented radar system has been studied for next-generation automotive radar with the advantages such as the fusion of radar and communication, strong interference suppression, and MIMO operation performance.First, a new multiplexing method with code division, which can compensate for the shortcomings of the existing multiplexing method for a MIMO OFDM radar is proposed. Second, a new signal structure of an OFDM radar to expand the range-Doppler ambiguities is proposed. It can help a MIMO OFDM radar to maintain TX orthogonality among a large number of TXs. Third, two interference suppression methods are proposed for OFDM-to-OFDM radar interference with the combination of low peak-to-average power ratio (PAPR) sequences and the proposed multiplexing method. A MIMO OFDM radar numerical platform is simulated for the verification of the proposed concepts. Fourth, a signal structure of a stepped-carrier OFDM (SC-OFDM) radar is proposed to solve the problem about high sampling rates of analog-to-digital converter (ADC) and digital-to-analog converter (DAC), which is a major drawback of a digital-oriented radar. The proposed concept is verified through the SC-OFDM radar simulation, and the target measurement is performed with the implemented radar hardware.First, a new multiplexing method with code division, which can compensate for the shortcomings of the existing multiplexing method for a MIMO OFDM radar is proposed. Second, a new signal structure of an OFDM radar to expand the range-Doppler ambiguities is proposed. It can help a MIMO OFDM radar to maintain TX orthogonality among a large number of TXs. Third, two interference suppression methods are proposed for OFDM-to-OFDM radar interference with the combination of low peak-to-average power ratio (PAPR) sequences and the proposed multiplexing method. A MIMO OFDM radar numerical platform is simulated for the verification of the proposed concepts. Fourth, a signal structure of a stepped-carrier OFDM (SC-OFDM) radar is proposed to solve the problem about high sampling rates of analog-to-digital converter (ADC) and digital-to-analog converter (DAC), which is a major drawback of a digital-oriented radar. The proposed concept is verified through the SC-OFDM radar simulation, and the target measurement is performed with the implemented radar hardware.