Observations of rain depolarization characteristics were conducted using the CS-2 and CS-3 beacon signals (19.45GHz, circular polarization, elevation angle=49.5) during seven years of 1986-1992 at Neyagawa, Osaka. The mean cross-polar phase relative to the co-polar phase of each rainfall event is distributed in a comparatively wide range from -100 to -150. This large variation is suggested to be caused by the difference of raindrop size distribution (DSD) in addition to that of rain intensity. The effects of DSD are examined by rain attenuation statistics for specific months, together with direct measurements of raindrop diameters on the ground for several rainfall events. Compared with representative DSD models, the effects of the Joss-drizzle type with relatively small raindrops primarily appear in "Baiu (Tsuyu)" period, while the effects of the Marshall-Palmer type which represents a standard type are enhanced in "Shurin (Akisame)" period. On the other hand, the effects of the Joss-thunderstorm type with comparatively large raindrops do not indicate a very clear seasonal variation. Possible improvements of XPD performed by differential phase shifters are generally found to be lower than 10dB for the rain depolarization due to the effect of residual differential attenuation after the cancellation of differential phase shift. Such XPD improvements are, however, very sensitive to the type of DSD, and it is suggested that the improvements are at least greater than 6dB for the Joss-drizzle type, whereas they are less than 6dB for the Marshall-Palmer and Joss-thunderstorm types. The effects of the XPD improvements are thus related to rainfall types, i.e., the type of DSD, and the improvements are considerably dependent upon the seasons in which each rainfall type frequently appears.

The Akebono satellite observed the Australian Omega signals when it passed about 1000km over the Omega station. In this paper, we compare the observed Omega signal intensities with the values obtained using a full wave calculation and we discuss a mechanism of modulation of the signals. The relative spatial variations of the calculated Omega intensities are quite consistent with those observed, but the absolute calculated intensities themselves are several dB larger than the observed intensities. This difference in intensity may be due to the horizontal inhomogeneity of the D region, which is not modeled in the full wave calculation, or to an incorrect assumption about radiation characteristics of the Omega antenna. It is found that modulation of the observed signals is caused by the interference between the waves with different k vectors.

In the present paper, we focus ourselves on the turning point (TP) algorithm proposed by Mueller and evaluate its performance when applied to a Gaussian signal with definite covariance function. Then the ECG wave is modeled by Gaussian signals: namely, the ECG is divided into two segments, the baseline segment and the QRS segment. The baseline segment is modeled by a Gaussian signal with butterworth spectrum and the QRS one by a narrow-band Gaussian signal. Performance of the TP algorithm is evaluated and compared when it is applied to a real ECG signal and its Gaussian model. The compression rate (CR) and the normalized mean square error (NMSE) are used as measures of performance. These measures show good coincidence with each other when applied to Gaussian signals with the mentioned spectra. Our results suggest that performance evaluation of the compression algorithms based on the stochastic-process model of ECG waves may be effective.

A communication LSI Set for Automotive Body control systems such as power windows, power seats, and power doors based on an in-vehicle network have been developed. The main function of the LSI is to achieve an original automotive communication protocol. The LSI set makes it possible to build a new kind of automotive control system, and reduces the number of wiring harnesses and weight below those of the conventional automotive body electronics. The communications transmitters and receivers have been integrated on-chip, so the LSI needs several external discrete components such as resistors, capacitors, and diodes. This communications LSI offers the advantages of small size and high reliability of the electronic control unit based on an in-vehicle network.

Automotive electronics technology has become extremely advanced in the regions of automotive engine control, anti-skid brake control, and others. These control systems require highly advanced control performance and high speed microprocessors which can rapidly execute interrupt processing. Automotive engine control systems are now widely utilized in cars with high speed, high power engines. At present, it is generally acknowledged that such high performance engine control for the 10,000 rpm, 12 cylinder engines requires three or more conventional microprocessors. We fabricated an engine control system prototype incorporating the data-driven processor under development, which was installed in an actual automobile. In this paper, the characteristics of the engine control program and simulation results are firstly discussed. Secondly, the structure of the engine control system prototype and the control performance applied to the actual automobile are shown. Finally, from the results of software simulation and the installation of the engine control system prototype with the data-driven processor, we conclude that a single chip data-driven microprocessor can control a high speed, high power, 10,000 rpm, 12 cylinder automobile engine.

Since carelessness in driving causes a terrible traffic accident, it is an important subject for a vehicle to avoid collision autonomously. Real-time collision detection between a vehicle and obstacles will be a key target for the next-generation car electronics system. In collision detection, a large storage capacity is usually required to store the 3-D information on the obstacles lacated in a workspace. Moreover, high-computational power is essential not only in coordinate transformation but also in matching operation. In the proposed collision detection VLSI processor, the matching operation is drastically accelerated by using a Content-Addressable Memory (CAM) which evaluates the magnitude relationships between an input word and all the stored words in parallel. A new obstacle representation based on a union of rectangular solids is also used to reduce the obstacle memory capacity, so that the collision detection can be parformed only by parallel magnitude comparison. Parallel architecture using several identical processor elements (PEs) is employed to perform the coordinate transformation at high speed based on the COordinate Rotation DIgital Computation (CORDIC) algorithms. The collision detection time becomes 5.2 ms using 20 PEs and five CAMs with a 42-kbit capacity.

We have developed new DMOS FET (DMOS) and intelligent power devices (IPD) specified for automotive load driving. Their features are extra-high surge immunity and low on-resistance. MOS power semiconductor devices are the most suitable for driving high speed and large current loads in future car electronics, but their high cost is the main obstacle preventing their implementation. To cut the total system cost, we have tried to enhance surge immunity of power semiconductor devices, at the same time reducing ON resistance, which enables us to omit external protection. Enhanced avalanche power dissipation also enables us to lower the breakdown voltage of the device, which also brings lower on-resistance. The drain to source avalanche immunity of vertical type DMOS (VDMOS) has been sharply improved by using the parasitic PN junction of the channel diffusion region as the cellular zener diode. Avalanche power dissipation energy per unit area of this durable DMOS is 10 to 100 times higher than that of conventional VDMOSs. Although the breakdown voltage of this device is only 30V, no external protection device is required in automotive applications. Several fault phenomena which might occur in this device are also described. Two types of IPDs are proposed in this paper. One is a durable and low-cost high-side switch IPD, whose enhanced surge immunity of IC section from VDD line transient is verified by prototypes. Simplification of the fabrication process has also been achieved by lowering its breakdown voltage. The other is an extra-low on-resistance H-bridge IPD. Major on-resistance reduction of an output lateral type DMOS (LDMOS) is achieved because the cell-array structure is realized by applying 2-layer electrode technology to the power section. The on-resistance per unit area of this LDMOS is almost equal to that of VDMOSs in the same voltage class.

The performances of BPNN (neural network trained by back propagation) and PCANN (neural network which computes principal component analysis) for ECG data compression have been investigated from several points of view. We have compared them with an existing data compression method TOMEK. We used MIT/BIH arrhythmia database as ECG data. Both BPNN and PCANN showed better results than TOMEK. They showed 1.1 to 1.4 times higher compression than TOMEK to achieve the same accuracy of reproduction (13.0% of PRD and 99.0% of CC). While PCANN showed better learning ability than BPNN in simple learning task, BPNN was a little better than PCANN regarding compression rates. Observing the reproduced waveforms, BPNN and PCANN had almost the same performance, and they were superior to TOMEK. The following characteristics were obtained from the experiments. Since PCANN is sensitive to the learning rate, we had to precisely control the learning rate while the learning is in progress. We also found the tendency that PCANN needs larger amount of iteration in learning than BPNN for getting the same performance. PCANN showed better learning ability than BPNN, however, the total learning cost were almost the same between BPNN and PCANN due to the large amount of iteration. We analyzed the connection weight patterns. Since PCANN has a clear mathematical background, its behavior can be explained theoretically. BPNN sometimes generated the connection weights which were similar to the principal components. We supposed that BPNN may occasionally generate those patterns, and performs well while doing that. Finally we concluded as follows. Although the difference of the performances is smal, it was always observed and PCANN never exceeded BPNN. When the ease of analysis or the relation to mathematics is important, PCANN is suitable. It will be useful for the study of the recorded data such as statistics.

A method for the compression of ECG data is presented. The method is based on the edit distance algorithm developed in the file comparison problems. The edit distance between two sequences of symbols is defined as the number of edit operations required to transform a sequence of symbols into the other. We adopt the edit distance algorithm to obtain a list of edit operations, called edit script, which transforms a reference pulse into a pulse selected from ECG data. If the decoder knows the same reference, it can reproduce the original pulse, only from the edit script. The amount of the edit script is expected to be smaller than that of the original pulse when the two pulses look alike and thereby we can reduce the amount of space to store the data. Applying the proposed scheme to the raw data of ECG, we have achieved a high compression about 14: 1 without losing the significant features of signals.

We extend the concept "optical instanton" to arbitrary dielectric media. For these general cases the exact analytical approach is no longer available. We derive an approximate analytical solution that would be valid in the vicinity of the light cone. A comparison is made between the analytical and the numerical solutions.

This paper gives a systematic approach to generate a Markov chain by a discrete-valued auto-regressive equation, which is a a nonlinear auto-regressive equation having a discrete-valued solution. The power spectrum, the correlation function and the transition probability are explicitly obtained in terms of the discrete-valued auto-regressive equation. Some computer results are illustrated in figures.

In this article, we consider a hysteresis oscillator which includes periodic thresholds. This oscillator relates to a model of human's sleep-wake cycles. Deriving a one dimensional return map rigorously, we can clarify existence regions of various periodic attractors in some parameter subspace. Also, we clarify co-existence regions of periodic attractors and existence regions of quasi-periodic attractors. Some of theoretical results are confirmed by laboratory measurements.

A two-dimensional quasi-exact active imaging method for detecting the conducting objects buried in a dielectric half-space is proposed. In this imaging method, an image function which is a projection of buried object to an arbitrary direction, is introduced exactly by taking account of the presence of the planar boundary. The image function is synthesized from the scattering fields which are measured by moving a transmitting antenna (a current source) and a receiving antenna (an observation point) simultaneously along the ground surface. The scattering field is generated by the physical optics current assumed on the surface of buried object. Because the effectiveness of physical optics approximation has been confirmed for this problem, this is a quasi-exact active imaging method. The validity of this imaging method is confirmed by some numerical simulations and an experiment.

This paper proposed a new algorithm of data compression for ambulatory ECG, where no distortion was included in the reconstructed signal, templates were constructed selectively from detected beats, and categorized ECG morphologies (templates) could be displayed in decoding the compressed data. This algorithm consisted of subtracting a best-fit template from the detected beat with an aid of multi-template matching, first differencing of the resulting residuals and modified Huffman coding. This algorithm was evaluated by applying it to ECG signals of the American Heart Association (AHA) data base in terms of bit rates. Following features were indicated. (1) Decompressed signal coincided completely with the original sampled ECG data. (2) Bit rate was approximately 800 bps at the appropriate threshold 50-60 units (1 unit2.4µVolt) for the template matching. This bit rate was almost the same as that of the direct compression (encoding the first differenced signal of original signal). (3) The decompressed templates could make it easy to classify the templates into the normal and abnormal beats; this could be executed without fully decompressing the ECG signal.

A technique was developed to reduce ECG data efficiently within a controlled accuracy. The sampled and digitized data of the original waveform of an ECG is transformed in three major processes. They are the calculation of a beat-to-beat variation, a polygonal approximation and the calculation of the difference between consecutive node points. Then, an adaptive coding technique is applied to minimize redundancies in the data. It was demonstrated that the ECG waveform sampled in 200 Hz, 10 bit/sample, 5 µV/digit could be reduced with the bit reduction ratio of about 10% and within the reconstruction error of about 2.5%. A polygonal approximation method, called MSAPA, was newly developed as a modification of the well known method, SAPA. It was shown that the MSAPA gave better reduction efficiency and smaller reconstruction error than the SAPA, when it was applied to the beat-to-beat variation waveform. The importance of the low-pass filtering as a preprocessing for the polygonal approximation was confirmed in concrete examples. The efficiency of the proposed technique was compared with the cased in which the polygonal approximation was not used. Through these analyses, it was found that the redundancy elimination of the coding technique worked effectively in the proposed technique.

We analyze the nonlinear dynamics of PLL from the "complex" singularity structure by introducing the complex time. The most important results which we have obtained in this work are as follow: (1) From the psi-series expansion of the solution, the local behavior in the neighbourhood of a movable singularity is mapped onto an integrable differential equation: the Ricatti equation. (2) From the movable pole of the Ricatti equation, a set of infinitly clustered singularities about a movable singularity is shown to exist for the equation of PLL by the multivalued mapping. The above results are interesting because the clustering and/or the fractal distribution of singularities is known to be a characteristic feature of the non-integrability or chaos. By using the method in this letter, we can present a circumstantial evidence for chaotic dynamics without assuming any small parameters in the equation of PLL.

We propose a recognition method for HMM using a simultaneous generative histogram. Proposed method uses the correlation between two features, which is expressed by a simultaneous generative histogram. Then output probabilities of integrated HMM are conditioned by the codeword of another feature. The proposed method is applied to isolated digit word recognition to confirm its validity.

It was more than 10 years ago that the first map navigation system, as an example of invehicle information system, has appeared in the market in Japan. Today's navigation system has been improved to the level that the latest system has 10 micro-processors, 7 MBytes of memories, and 4 GBytes of external data storage for map database. From the viewpoint of the automobile driver, there are still some problems with the system. Major problems in general are a lack of traffic information, better human interface, and a need for cost-reduction. The introduction of application specific ICs (ASICs) is expected to make systems smaller, costless, and give higher speed response. Today's in-vehicle information systems are reviewed function by function to discover what functions need to be implemented into ASICs for future systems, what ASICs will be required, and what technology has to be developed. It is concluded that more integration technology is expected including high parformance CPUs, large capacity memories, interface circuits, and some analog circuits such as DA converter. To develop this technology, some, major problems such as power consumption, number of input/output signals, as well as design aid and process technology are pointed out.

An electrocardiogram (ECG) data compression algorithm using a polygonal approximation and the template beat variation method (TBV) has been evaluated by reconstruction error and automatic interpretation. The algorithm combining SAPA3 with TBV (SAPA3/TBV) has superior compression performance in PRD and compression ratio. The reconstruction errors, defined as the difference of the amplitude and the time duration between the original ECG and the reconstructed one, are large at waves with small amplitude and/or gradual slopes such as the P wave. Tracing rebuilt from the compressed ECG has been analysed using the automatic interpretative program, and the diagnostic answers with the realated measurements have been compared with the results obtained on the original ECG. The data compression algorithms (SAPA3 and SAPA3/TBV) have been tested on 100 cases in the data base produced by CSE. The reconstruction errors are related to the diagnostic errors. The TBV method suppresses these errors and more than 90% of diagnostic agreements at the error limit of 15µV can be obtained.

A theoretical and experimental study of a thin card-sized antenna is presented. The method of moment with a wire-grid model is used to analyze this antenna. In order to validate numerical efficiency, measurements using Wheeler method are preformed on this antenna and its wire-grid models. The experimental and theoretical results are in good agreement if the wire conductivity is well chosen. And the noise reduction of measured Wheeler efficiency using least mean square method is also examined.