Seongwook Lee

Radar cross section measurement with 77 GHz automotive FMCW radar

In this paper, radar cross section (RCS) measurement for human subjects and vehicles in 77 GHz automotive frequency modulated continuous wave (FMCW) radar system is presented. In this system, it is impossible to utilize conventional RCS definition due to high frequency band and the modulation technique used. Therefore, we introduce a new parameter called pseudo-RCS that can replace the conventional RCS. Then, we conduct actual experiment in the road to measure the RCS of the human subjects and the vehicles. In the measurement, data of four human subjects and four different kinds of vehicles are recorded with the 77 GHz FMCW radar. From the actual measured data, we find RCS distributions of the human subjects and the vehicles. For the human subjects, the RCS values are distributed following the Nakagami distribution. On the other hand, the log-normal distribution is well fit for the RCS values in the case of the vehicle.

SNR analysis and estimation for efficient phase noise mitigation in millimetre-wave SC-FDE systems

This study demonstrates a signal-to-noise ratio (SNR) analysis and estimation algorithm for efficient phase noise mitigation that can be practically applied to single-carrier frequency-domain-equalisation (SC-FDE) systems that operate in millimetre-wave bands. First, the effect of phase noise in SC-FDE systems is investigated on each of the packet reception processes, namely, channel estimation, SNR estimation, and data-field reception. According to the analysis, an SNR estimation algorithm is proposed. The performance of minimum-mean-square-error equalisation and conventional phase noise mitigation algorithm can be enhanced using the proposed SNR estimation. The effectiveness of the proposed analysis and SNR estimation algorithm is verified through the link-level simulation. Compared with the conventional SNR estimation and the iterative phase noise mitigation algorithms, the proposed algorithm provides a lower packet-error rate without any iterative decoding process.

Logarithmic-domain array interpolation for improved DOA estimation in automotive radars

In this paper, we propose a novel array interpolation method in logarithmic domain for enhanced direction of arrival (DOA) estimation. Array interpolation techniques are broadly utilized in the DOA estimation for achieving better angular resolution. Generally, to generate interpolated array elements from original array elements, the method of linear least squares (LLS) has been used. When we use the LLS method, the interpolated array elements are formulated by linear combinations of the original array elements. Therefore, amplitudes of the interpolated array elements may not be equivalent to those of the original array elements. In addition, through a transformation matrix from the LLS method, phases of the interpolated array elements are not precisely generated. For the DOA estimation, phase information of interpolated array elements is important. Therefore, we propose a novel array transformation matrix for generating accurate phases of the interpolated array elements to improve the DOA estimation performance. Verifying from simulation and measurement results, our method shows much better angular resolution and estimation accuracy.

Harmonic clutter recognition and suppression for automotive radar sensors

In this article, we propose a novel harmonic clutter recognition and suppression method to overcome the deterioration of a target- or vehicle-detection performance due to harmonic clutters. Although several studies have been performed on the reflection and diffraction on road surfaces for automotive radar sensors, most of them did not consider the case where metallic structures such as iron tunnels with greater reflection are densely distributed. The proposed method measures the periodicity of harmonic clutters by analyzing the spectral characteristics of the received radar signal with various road conditions. The proposed method can successfully recognize harmonic clutters. In addition, experimental results show that early detection of a target vehicle in an iron tunnel under adaptive cruise control is improved using the proposed clutter suppression method.