Yoshikazu Asano, Shigeki Oshima,
Tomohisa Harada, Masaru Ogawa

This paper proposes a millimeter-wave holographic radar with a simple structure for automotive applications. The simplicity can be realized by switching both transmitting and receiving antennas. Also, a super resolution technique is introduced for the detection of angular positions in the proposed radar. The radar has accomplished an azimuthal angular resolution of less than 2 degrees and an azimuthal field of view (FoV) of more than 20 degrees. Simultaneously, the radar is capable of fulfilling the conditions that the width of the radar sensor must be less than 100 millimeters due to the limitation of the installation area.

We propose the microstrip array antenna with high efficiency for automotive radar systems. The proposed antenna consists of a straight feeding microstrip line and rectangular radiating elements connected directly to the microstrip line at their corners without dividers and impedance transformers in order to realize lower feeding line loss and linear polarization inclined 45 degrees. The radiation coefficient of the rectangular radiating elements is investigated by the finite element method. It is shown that the radiation coefficient is controlled from 1 % to 23 %, which is wide enough to set aimed amplitude distribution of an array antenna. The array antenna having 2 × 37 radiating elements is developed as one subarray of an electrical beam scanning array antenna for automotive radar systems. As a result of experiment, high efficiency of 53 % with high gain of 22.5 dBi is obtained at the design frequency of 76.5 GHz. The efficiency of the developed antenna is higher than that of conventional millimeter-wave microstrip array antennas.

Hideo Iizuka, Toshiaki Watanabe,
Kazuo Sato, Kunitoshi Nishikawa

A new type of microstrip line to waveguide transition fabricated on a single layer dielectric substrate is proposed. As a result of experiments, low transmission loss of 0.4 dB was realized at the design frequency of 76.5 GHz. Bandwidth of the transition was numerically investigated by the finite element method. It was clarified that the bandwidth of the transition became wider as the cross section of the waveguide became smaller and twice as wide as that of a conventional microstrip patch antenna element fabricated on a dielectric substrate with the same parameters. In addition, the effect of error in the relative position between the dielectric substrate and the waveguide was also investigated. It became clear that degradation of transmission characteristics was less than 0.1 dB for a manufacturing accuracy within ±0.1 mm.