The rain attenuation in the frequency range from 1 to 1000 GHz was calculated by using the Laws-Parsons, Sekine-Lind and Ihara-Furuhama-Manabe distributions for raindrop-size. The results were compared with the recent microwave measurements from 8 to 312.5 GHz at the rain rate R50 mm/hr. The Laws-Parsons distribution has a good agreement with the measurements, while up to 100 GHz, the Sekine-Lind distribution leads to more attenuation than the Laws-Parsons distribution and above 100 GHz, the Ihara-Furuhama-Manabe distribution gives more attenuation than the Laws-Parsons distribution.

We have compared the various raindrop-size distributions (DSD) with the recent experimental data collected by the distrometer. It is shown that the Weibull distribution is the best fit to the experimental data for drizzle, widespread and thunderstorm rain cases. By using this Weibull DSD, we obtained a new expression of the radar reflectivity factor (Z) and the rainfall rate (R) relation, that is Z=285R1.48, which gives few errors comparing to some measurements in TRMM frequency of 14GHZ.

The millimeter wave (MMW) radar has good compromise characteristics of both microwave radar and optical sensors. It has better angular and range resolving abilities than microwave radar, and a longer penetrating range than optical sensors. We used the MMW radar to detect targets located in the sea and among sea ice clutter based on fractals, wavelets, and neural networks. The wavelets were used as feature extractors to decompose the MMW radar images and to extract the feature vectors from approximation signals at different resolution levels. Unsupervised neural classifiers with parallel computational architecture were used to classify sea ice, sea water and targets based on the competitive learning algorithm. The fractal dimensions could provide a quantitative description of the roughness of the radar image. Using these techniques, we can detect targets quickly and clearly discriminate between sea ice, sea water, and targets.

In a radar system, it is well known that the conventional and logarithmic CFAR techniques after a square-law detector are effective for Rayleigh clutter. To apply these CFAR techniques to practical radar systems with a linear detector, the false-alarm probability was calculated by a Monte Carlo simulation on a computer for a finite number of samples N. It is concluded that the conventional CFAR receiver is superior to the logarithmic CFAR receiver.

We have already measured ground clutter using an X-band and L-band radars. Here, ground clutter was first measured using a millimeter wave radar with the frequency of 34.86 GHz, which is located on the campus of the University of Electro-Communications. The pulsewidth of the radar was 30 ns. Thus the spatial resolution was as small as 4.5 m. We have found that the clutter amplitude distribution obeys a Weibull distribution with shape parameter of c0.497 to 0.675 at depression angles of 0.8 to 1.9 deg., when reflectors are ordinary terrain and such structures as landing strips at airport and buildings. To improve target detectability in such Weibull-distributed ground clutter, Weibull constant false alarm rate (CFAR) system will be required.

Ground clutter from irregular surfaces was measured using an L-band long range air-route surveillance radar (ARSR) at very low grazing angles, between 0.13 and 0.25. It is shown that the ground clutter amplitude statistics themselves do not always follow a Weibull distribution, but rather the residual amplitude after the double canceller moving target indicator (MTI) obeys a Weibull distribution. Therefore, the unsuppressed residual ground clutter will be suppressed by means of Weibull CFAR processors.

Fractals provide a good description of natural scenes and objects based on their statistically self-similar property. They are also used to discriminate natural or man-made objects because natural objects have a better fitting to the fractional Brownian motion (fBm) model than artificial objects. Sea clutter as natural phenomena well fit to the fBm to induce little error. On the other hand, targets as man-made objects induce much more error because they frequently deviate from the fBm model. Therefore, the fractal error has a good characteristic to detect targets buried in clutter. We modified the fractal error defined by Cooper to be suitable for radar image processing. For the X-band radar image, the performance of our proposed method is comparable to that of the Cooper's method. For the millimeter wave (MMW) radar images, our method is better than the Cooper's one.

A novel algorithm associated with fractal preprocessors, wavelet feature extractors and unsupervised neural classifiers is proposed for detecting radar targets embedded in sea ice and sea clutter. Utilizing the advantages of fractals, wavelets and neural networks, the algorithm is suitable for real-time and automatic applications. Fractal preprocessor can increase 10 dB signal-to-clutter ratios (S/C) for radar images by using fractal error. Fractal error will make easy to detect radar targets embedded in high clutter environments. Wavelet feature extractors with a high speed computing architecture, can extract enough information for classifying radar targets and clutter, and improve signal-to-clutter ratios. Wavelet feature extractors can also provide flexible combinations for feature vectors at different clutter environments. The unsupervised neural classifier has a parallel operation architecture easily applied to hardware, and a low computational load algorithm without manual interventions during learning stage. We modified the unsupervised competitive learning algorithm to be applicable for detecting small radar targets by introducing an asymmetry neighborhood factor. The asymmetry neighborhood factor can provide a protective learning to prevent interference from clutter and improve the learning effects of radar targets. The small radar targets in Millimeter wave (MMW) and X-band radar images have been successfully discriminated by our proposed algorithm. The effective, efficient, high noise immunity characteristics for our proposed algorithm have been demonstrated to be suitable for automatic and real time applications.

The QPI (quasiparticle injection) devices have the most transistor-like characteristics in many superconducting three-terminal devices. In particular, Quiteron which operates with the principle of energy gap's suppression only to modulate the conductance of the output junction has a promising feature, such as a large gain, non-latching operation, and binary inversion. In this paper, we have investigated the behavior of the energy gaps to analyze the characteristics of the QPI devices. First we have introduced the nonequilibrium GL equation. Then we have derived a set of equations for QPI devices by using this equation. It is found that the energy gap of middle layer has the singularity under quasiparticle injection.

Weibull-distributed ground, sea, sea-ice and weather clutter were measured in Japan for various radar resolutions and wavebands. Weibull clutter and its suppression techniques are reviewed. Especially, Weibull CFAR in two-dimensional clutter rejection system is emphasized.

The critical temperature Tc of recent oxide superconductors in Ba-Y-Cu-O systems is considered from the complete electron-phonon interactions in two-dimensional [CuO2]-layers. It is concluded that the value of Tc does not exceed 110 K, so long as the phonon-mechanism is assumed.

We have fabricated all-Nb thin film microbridges by nanometer process using new resist developed by us, electron beam lithography (EBL) and reactive ion etching (RIE) using CBrF3 gas. The resistance against CBrF3 plasma of this EB resist is 4-10 times as strong as poly-(methyl methacrylate) PMMA. The merit of RIE using CBrF3 gas is an anisotropic etching and high selectivity about resist and target. Trench of about 20 nm width was fabricated. Using this technique, the bridge with 40 nm length and 50 nm width was fabricated, and the thickness of bridge was 100 nm. The capacitance of the junction was estimated as 0.004 pF. Because of this small capacitance, fabricated samples are suitable for detection of submillimeter wave. The critical current Ic (T) of fabricated samples was proportional to (1T/Tc)3/2 like variable thickness bridge (VTB). Moreover, Shapiro step up to the 11th under the millimeter wave radiation (70 GHz) was observed.

Ground clutter from cultivated land was measured using an L-band long range air-route surveillance radar (ARSR) at very low grazing angles, between 0.21 and 0.32. It is shown that the Weibull-distributed ground clutter obeys a Weibull distribution in the frequency domain after processing by the discrete Fourier transform (DFT). Thus the new Weibull-CFAR should be considered to suppress such clutter in the frequency domain.

Weather clutter was measured using an L-band long-range (200 nmi.) air-route surveillance radar (ARSR), from the stored data of five scans. It is shown that weather clutter obeys a Weibull distribution, and moreover such Weibull-distributed weather clutter also obeys a Weibull distribution after passing through a moving target indicator (MTI) processor realized by a double canceller. Some adaptive methods for suppressing Weibull-distributed clutter are summarized.

Assuming a perfect circulary polarized radar system, the cancellation ratio limitations were evaluated using the Sekine-Lind rain-drop distribution. Numerical methods were used and the cancellation limitation was plotted against rainfall rate for various wind velocities.

We observed the log normal, log-Weibull and K-distributed sea-clutter from high sea state 7 with an X-band radar for grazing angles between 3.1 and 17.5. To determine the sea-clutter amplitude statistics, we introduced the Akaike Information Criterion (AIC), which is more rigorous fit of the distribution to the data than the least-squares method.

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.

Sea ice clutter was measured using an X-band radar which is located at the city of Mombetsu in Hokkaido. The pulsewidth of the radar was 80 nsec. To sample by 40 nsec and record digitally, an emitter coupled logic (ECL) was used as a high-speed IC. The sampled data were first transferred to 64 Kbyte dynamic memory board and next to a 5 inch floppy disk through an 8 bit micro-computer. These data were processed by a 16 bit micro-computer. As a result, it is shown that the amplitude of sea ice obeys a Weibull disturibution with shape parameters of c0.50 to 1.65. Thus, the amplitude statistics deviate from the well-known Rayleigh distribution of c2.0, in which a logarithmic/constant false alarm rate (LOG/CFAR) circuit is useful. Therefore, it is concluded that the new Weibull/CFAR should be considered to suppress sea ice clutter.