(The) study on antennas for automotive radar and FMCW radar system for UAVs detection

Abstract

Automotive radar which is making driving safer and more convenient was first integrated in 1959 and the first generation of 77GHz band based automotive radar was introduced in 1998. The radar based driver assistance systems recently have become available even for mid-priced cars. Accelerating this trend, a rapidly growing number of radar sensors are being integrated into new vehicles to allow driver assistance functions such as adaptive cruise control (ACC), parking assistant system (PAS), lane change assist (LCA), and blind zone detection for comfort and safety. The problem of sensing pedestrians or obstacles on side roads due to the null point of the radiation pattern is issued in automotive radar systems. To overcome this problem, a null-filling antenna for automotive radar is proposed. A null-filling antenna for 77GHz automotive radar is investigated using the genetic algorithm. The single column of the proposed antenna consists of four gap-coupled antenna elements and 14 direct-coupled antenna elements. The radiating elements are inclined 45 from the feedline. The proposed antenna has 19.67 dBi gain with a 20.19-dB sidelobe level in the elevation and a 25.08-dB sidelobe level in the azimuth direction. The blind zone is reduced from 19.03 to 2.38 m using the proposed antenna for sensing the obstacle. A novel microstrip patch antenna is proposed for rear and side detection application. I propose a novel low cost microstrip patch antenna with fully covering 24GHz ISM band (24.05~24.25GHz). The antenna design has been investigated through both the parametric study and the demonstration of surface currents on the antenna structure. The surface currents related to the co-polarization increased, and those related to the cross polarization is reduced by attaching shorted parasitic element. The measured gain of the antenna is 11.04dBi and that of the cross polarization level is -20.73dB. The cross polarization level is reduced by 5dB due to the shorted parasitic patch. The cross polarization levels are increased in ±70° due to the current flowing along the large ground. However, it is negligible because those angle is out of angle of detection in automotive application. The sidelobe levels of the proposed antenna are -20.59dB @ 70° in the XZ plane and the front to back ratio of proposed antenna is -29.10dB. The half-power beamwidth of the proposed antenna is 16.2 ˚ in the XZ plane and 100.8˚ in the YZ plane. The popularity of small Unmanned Aerial Vehicles (UAVs) has rapidly increased over the years and is expected to be more accelerated. UAVs can be equipped with sensors and weapons for military applications (such as air reconnaissance, bombing and air combats) and civil missions (such as telecommunication, a border monitoring, the weather forecast, and remote sensing). The suitable countermeasures are required to prevent a potential threat. The identification of small UAV is discussed in this thesis. I present the realization of a High sensitivity K-band FMCW radar system to measure the range and micro-Doppler phenomenon. High performance of FMCW radar signals in terms of flatness, linearity and sensitivity are achieved. The novel signal processing for fast sweeping FMCW radar is proposed. In order to extract the micro-Doppler frequency in FMCW radar system, our approach is based on the selected bins of each chirp signal and the Hilbert-Huang Transform(HHT) method is used to extract the micro-Doppler signal. We measured the range and micro-Doppler phenomenon to evaluate the proposed signal processing at two different environments: an anechoic chamber in which unwanted reflection from other clutters are removed and the outdoor environment in which the noise and reflections from other clutters are considered. Using the proposed approach, we clearly extract the micro-Doppler signatures from a rotating propeller with an odd number of blades in the anechoic chamber and with an even number of blades in outdoor environment. The inherent problem of an FMCW radar system is that there will be a certain amount of coupling from the TX antenna to the RX antenna. The mutual coupling between the antennas describes energy absorbed by one antenna’s receiver when another nearby antenna is operating. That is, mutual coupling is typically undesirable because energy that should be radiated away is absorbed by a nearby antenna. The distributed FMCW Radar is discussed. I present the realization of a High sensitivity K-band FMCW radar system to detect and measure the range and velocity of the small RCS target. High performance of FMCW radar signals in terms of flatness, linearity and sensitivity is achieved. In order to enhance the isolation between Tx and Rx, our approach is fiber-optic based distributed radar system. The VGA is inserted in de-modulation block to compensate the path loss, it makes the beat signal more constant. We measured the range and velocity of the small drone to evaluate the proposed distributed radar system. The transmitter and receiver are located on the 3m fixture to reduce the ground reflection with 12m spacing to reduce the leakage. Using the proposed radar system, we clearly detect the small drone within 500m range.