This paper describes the development of a compact and low cost
millimeter wave doppler radar sensor (77 GHz band), which can
measure the vehicle ground speed precisely. The sensor has three
unique features: First, all the radio frequency components are
integrated into a single chip, including a millimeter wave
transceiver and an on-chip antenna. Then, the chip package is made
of plastic resin without use of expensive ceramic. Finally, a tiny
dome-shaped resin lens is attached to the chip to collimate waves.
These technologies enable the sensor to measure 53 x 71 x 65 mm₃,
to weigh 115 grams. Compared to a conventional optical measuring
instrument, for example, the sensor weighs only about fifteenth and
is one-fifth of the size, while the measurement accuracy is almost
comparable. So this sensor seems to have a variety of potential
applications.
In this paper, we also considered the feasibility of some other
applications than just measuring ground speed. One is the yaw rate
detection by using two sensors mounted on both sides of the
vehicle. It can be calculated from differential speed between
sensors. From the experimental results, we found that the detection
was possible and the limit of sensitivity depended on the speed
measurement accuracy which is under 2% variation. The other
possible application is detecting obstruction. Although it was
difficult to cover from 0 meters to far side with one sensor
because of its narrow beam shape, we confirmed from experiments
that the sensor was able to detect vehicles in the next lane in the
range from at least 10 to 60 meters.
