This paper presents a collision warning system that uses laser radar to measure the distance to a preceding vehicle and issues an audible warning to alert the driver if a safe headway is not maintained. The laser radar system is of the cooperative type in that it detects light reflected from a reflex reflector attached at the rear of other vehicles. With a 10-watt pulsed laser, a maximum detection range of over 100m is obtained. The construction and operation of the collision warning system are described along with the configuration of the optical system used in the laser radar head and the results of detection performance evaluations.

An FM-CW radar system for the detection of objects buried in sandy ground is explored and is applied to a field measurement. The key factors for underground FM-CW radar performance are the center frequency and bandwidth determining the depth at which the radar can detect targets and the resolution in the range direction. In order for FM-CW radar sounding, two ridged horn antennas are employed in the system, which are operative in the frequency range of 250-1000MHz. The impedance matching to the ground is optimized by measuring the echo strength from a fixed target as a function of the spacing interval between the antenna aperture and the ground surface. It is shown that the radar with an output power of 18dBm could detect a metallic plate (30100cm) and a pipe (10cmφ) buried at the depth of 1.2m. Also the synthetic aperture technique together with an averaging and subtracting method produced fine image in shallow region up to 100cm in the sandy ground.

We observed a ship as a radar target embedded in sea clutter using a millimeter wave radar. The shape of the ship and sea clutter were discriminated by using texture analysis in image processing. As a discriminator, a nonlinear transformation of a local pattern was defined to deal with high order statistics.

The diffraction of a plane electromagnetic wave by a parallel-plate waveguide cavity with a thick planar termination is rigorously analyzed for both the E and the H polarization using the Wiener-Hopf technique. Introducing the Fourier transform for the unknown scattered field and applying boundary conditions in the transform domain, the problem is formulated in terms of the simultaneous Wiener-Hopf equations, which are solved exactly in a formal sense via the factorization and decomposition procedure. Since the formal solution involves an infinite number of unknowns and branch-cut integrals with unknown integrands, approximation procedures based on rigorous asymptotics are further presented to yield the approximate solution convenient for numerical computations. The scattered field inside and outside the cavity is evaluated by taking the inverse Fourier transform and applying the saddle point method. Representative numerical examples of the monostatic and bistatic radar cross sections are presented for various physical parameters, and the scattering characteristics of the cavity are discussed in detail.

Most communication cables are laid underground. In order to make construction and maintenance works easier, systems to detect buried objects have already been developed using the electromagnetic pulse radar technique. However, existing detection systems are not really practical due to their rather limited processing speed. To achieve sufficient processing speed, two dedicated custom FFT LSI's are designed and realized with 0.8 µm-CMOS technology. The two chips have an equivalent processing capacity of 200 MOPS. An efficietn hardware algorithm for address generation and 2 word parallel processing are introduced. In addition, an enhanced system organization is developed together with an improved pattern recognition scheme and aperture synthesis hardware. The new processor executes a FFT/parameter extraction operation in 4 seconds and aperture synthesis in 1 second. This speed meets the design target, and a real time detection system for underground objects becomes possible.

The detection problem of fluctuating radar targets in the presence of interference (noise and clutter) is considered; the assumed model for both target and clutter is a zero-mean stationary Gaussian random process with assigned power spectral densities. The pertaing optimum linear processor, namely the Optimized Filtering, is derived and its performance are evaluated in different operating conditions, including mismatching with the designed model. Finally, comparison with filtering techniques designed for targets with zero spectral width, i.e. the Moving Target Detector, are performed.

Recently most of the singularities of the equivalent edge currents for flat plates were eliminated by the authors using the paths of most rapid phase variation. A unique direction on the plate was determined for given incidence and observer. This paper extends this method for arbitrary angle wedges and presents the new expressions of the equivalent edge currents. The resultant expressions are valid for any incidence and observation aspects and have no false singularities. Diffraction patterns and radar cross sections of 3-D objects composed of wedges are calculated by using these currents. They show good agreements with experimental data or the results by the other methods.

Surveillance capabilities and operational requirements for future Space-based radar systems are considered. With special attention paid to Air Traffic Control applications, an optimal system architecture is defined. The resulting large antenna dimensions call for novel solutions such as distributed arrays in space.