Yoichi Nakagawa, Device Solutions Center, R&D Division, Panasonic Corp, delivered a lecture titled "79GHz Milliwave Radar Capable of Separately Detecting Humans" at "Milliwave Application Conference," which Nikkei Electronics organized April 23, 2014.
To accurately detect an object with a radar device, a high resolution is required for all of range, angle and speed measurements. For example, resolution of range measurement improves in proportion to available frequency bandwidth. Resolution of angle measurement is proportionate to antenna size (in units of wavelength), and, therefore, a higher frequency is advantageous. Resolution of speed measurement can be directly estimated by using resolution for Doppler frequency shift and, thus, is proportionate to frequency when observation time is constant.
Therefore, 79GHz-band radar devices are superior to 24G/26GHz-band and 76GHz-band radar devices in resolutions of range, angle and speed measurements, Nakagawa said.
Panasonic aims to use a 79GHz radar device first as a roadside sensor at an intersection, having completed the "Research and Development for the Advancement of 79GHz-band Radar System," which was sponsored by Japan's Ministry of Internal Affairs and Communications (MIC), in fiscal 2013.
For a roadside sensor that can monitor every corner of an intersection, it is necessary to achieve (1) a range resolution of 20cm or less for separately detecting pedestrians and (2) angle resolution of 5° or lower for ensuring a positional accuracy equivalent to a lane width from a distance of 40m, Nakagawa said.
To meet those technical requirements, Panasonic employed coded pulse and adaptive array antenna for data transmission and reception. In regard to the coded pulse, the company improved reception sensitivity by (1) taking advantage of the high separation performance of the pulse Doppler method and (2) extending pulse transmission time by code modulation to increase average transmission output instead of transmitting and receiving single pulse.
As for the adaptive array antenna, Panasonic improved its angle estimation accuracy for multiple reflected waves with the spatial filter effect of transmission beamforming, Nakagawa said.
In the lecture, he showed high-resolution videos shot by sensor fusion of a milliwave radar device and stereo camera including a video taken by a prototyped device installed at an intersection in the company's property.