We have made a prototype of a headway control radar using a pulsed semiconductor laser and have confirmed its feasibility.

The transmitter of this radar transmits two beams having radiation angles of ±0.5 and ±1.4 degrees. The transmitter uses an aspherical plastic lens, and the receiver uses a wide aperture Fresnel lens for improved detection performance. The receiver has automatic gain control (AGC) and sensitive time control (STC) circuits. AGC decreases measurement errors caused by fluctuations in target reflectivity. STC decreases misdetection errors caused by rain or snowfall. An 8-bit microprocessor simplifies the range measurement block. Vehicle tests have shown that the maximum detection range is 350 m from the rear of a static vehicle and the measurement error was 2 m or less in the range of 100 m and above. Since lost targets occurred in the field tests, it will be necessaryt o examine the beam scanning methods.