Millimeter-Wave Microstrip Array Antenna for Automotive Radars

Hideo IIZUKA  Toshiaki WATANABE  Kazuo SATO  Kunitoshi NISHIKAWA  

IEICE TRANSACTIONS on Communications   Vol.E86-B   No.9   pp.2728-2738
Publication Date: 2003/09/01
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Antennas and Propagation
automotive radars,  millimeter-wave,  45-degree inclined linear polarization,  microstrip array antenna,  high aperture efficiency,  

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A microstrip array antenna with 45-degree inclined linear polarization is proposed for automotive radars. The proposed antenna has the advantages of high aperture efficiency, low profile and ease of manufacture. The rectangular radiating elements inclined at 45 degrees to the straight microstrip line are directly connected to it at their corners in the proposed array antenna. The radiating element has a feature that radiation conductance for co-polarization is controlled widely enough to set desired amplitude distribution keeping excited mode for cross-polarization negligibly small. The feed line loss of the linear array antenna having 15 wavelengths is estimated 0.9 dB in the design taking the loss of the microstrip line into account. The performance of two types of developed antennas, for electrical and mechanical scanning radars, is presented. The fan beam subarray antenna for electrical scanning radars has an aperture efficiency of 53% with gain of 22.5 dBi at 76.5 GHz. For mechanical scanning radars, the two-stage series feeding circuit is also proposed for lower feed line loss and setting desired amplitude distribution. The pencil beam array antenna has an aperture efficiency of 39% with gain of 32.2 dBi at 76.5 GHz.