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Vehicular collision avoidance radar systems using millimeter-wave have been developed in recent years. Because of their simple structures, a microstrip antenna or a lens antenna is often used as the radar antenna. However, the antenna efficiencies of these antennas are low, in general. Therefore, the types of antenna that have small antenna aperture are difficult to obtain high antenna gains. In addition, it is difficult to radiate many beams at narrow beam intervals with a lens antenna. We developed an offset paraboloidal reflector antenna (the OP antenna) for the vehicular collision avoidance radar. This antenna consists of one pyramidal horn antenna and one offset paraboloidal reflector. They pyramidal horn and the radio frequency unit (the RF unit) of the radar are fixed in the radar head. To scan the beam, only the reflector is rotated. Using a reflector-rotating mechanism, the OP antenna can radiate many beams toward different directions.

An offset paraboloidal reflector antenna for vehicular collision avoidance radar is designed and evaluated. The antenna is designed to use at 77GHz band, and to have suitable gain and beamwidth for the vehicular collision avoidance radar. The properties measured and calculated are compared and confirmed to agree well. The offset paraboloidal reflector antenna is low-loss and has large degree of freedom of antenna design, compared with such as a microstrip antenna. So, using this type of the antenna for the radar system contributes to miniaturize, to make light weight, and to be easily mass-produced of the radar system.

For either case for rotary shaft or reciprocating shaft motion, rubber lip type seal leakage problems are often encountered under low temperature conditions. As for causes of leakage under low temperature conditions, there are several factors such as following ability of the sealing lip for runout of a shaft or rod, roughening of the sealing surface of the rubber material at the stage of initial motion and so on. Sealing performance is essentially dependent upon the low temperature property of the rubber materials. In this paper, the leakage phenomena is explained through visco-elastic characteristics of the rubber materials.