Speed Measurement of Vehicles by Radio Wave - Absolute Speed Measurement of Automobiles

This paper describes a new type of absolute speedometer of automobiles. It is known that the electric field intensity of the radio waves in the UHF/VHF range exhibits spatial periodic patterns due to the multi-pass fading phenomenon. We employ this pattern as the spatial scale for speed measurement. In this method, first two antennae set at the front and rear site of vehicle detects the pattern. Next a micro processor estimate the speed by calculating delay time between the two patterns detected. We have examined if the pattern can be used as the spatial scale for speed measurement by laboratory experiments. We found it could¹). In this paper we consider how to realize an automobile speedometer based on the above idea. In order to develop and design the speedometer, we read to develop a new electric field level meter with the following characteristics;

1. (1)
   The meter must have quick response.
2. (2)
   The meter must have wide dynamic range.
3. (3)
   The front and rear meters must have the same characteristics.

Further we went out from our laboratory to measure the electric field intensities at the various sites under various speeds. We found the method could measure the speed of automobile in the real situations.