摘要:

AbstractLOTOS is a formal description technique (FDT) developed by ISO. This paper proposes a formal technique for generating test sequences from a LOTOS specification. In the proposed technique, test sequences correspond to a finite “tree” which is represented as a TreeLOTOS expression which is a subset of LOTOS. A labelled transition system (LTS) with variables called VTS is introduced to generate test sequences, which is useful not only for compactness of expression but also for effective selection of test sequences at the execution of tests. Furthermore, the concept of the reduced form of a VTS is introduced and, by using this concept, efficient test sequences can be obtai

ISSN:8756-6621    

DOI:10.1002/ecja.4410760201

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractIt is known that the bit error rate is deteriorated if there exist echoes on the transmission line. This paper presents a theoretical analysis on influences of an echo on the bit error rate in the optical DPSK communication system. In general, there exists a floor in the bit error rate due to the phase fluctuation of the laser light, which is not reduced by increasing the received optical power. It is shown that the floor value increases with the increase of the amplitude ratio of the echo to the principal wave, as well as the increase of the delay time. It also is shown that the effect of the echo is more remarkable when the bit rate is higher and the spectral linewidth of the laser light is narrower.Finally, the bit error rate is calculated as a function of the received optical power and the power penalty is evaluated. The relation between the bit error rate for which the effect of the echo cannot be ignored and the spectral linewidth is discussed. The features of this paper are that the echo with a small delay time, which has some correlation to the principal wave, can be analyzed.

ISSN:8756-6621    

DOI:10.1002/ecja.4410760202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThis paper proposes a switched snubber circuit for the switching converter. The switched snubber is made of a series connection of a switch and a capacitor. The switched snubber can suppress the surge over a wide range of duty ratio and is basically lossless. The switched snubber features zero‐voltage switching. A PWM controllable and low‐stress converters are developed by replacing the resonant capacitor with a switched snubber in the voltage‐mode resonant converters. Also, the region where the output voltage increases abnormally is narrow in the converters with a switched sn

ISSN:8756-6621    

DOI:10.1002/ecja.4410760203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractIn the electromagnetic slot‐coupled microstrip antenna in which a triplate transmission line is used and a patch antenna is fed via a slot on the ground plane, a parallel plate mode (TEM wave) propagating between the ground planes is excited so that a power leakage causes unwanted coupling and radiation.This paper studies the Poynting power and the electric field of this parallel plate mode. The amount of the parallel plate mode generated and the propagation behavior are investigated analytically by means of the Spatial Network Method. The method for installing shorting pins known for their suppression of the parallel plate mode is studied in its relationship to the generation of the parallel plate mode.A method for placing pins with a least number of pins is proposed. The relationship between the resonance of the parallel plate mode and the external dimensions of the dielectric substrate comprising the triplate transmission line is studied experimentally. It is found that the resonance of the parallel plate mode coincides with that of an open resonator with its dimensions identical to a finite dielectric substrate comprising the triplate transmission lin

ISSN:8756-6621    

DOI:10.1002/ecja.4410760204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractWhen the electromagnetic environment of the space plasma is observed by a spacecraft in space, it is often difficult to distinguish the disturbance due to the satellite itself and natural phenomena. In such cases, it is effective to use a numerical experiment in which the phenomena arising around a spacecraft are reconstructed on a computer. Since the plasma filling the space is extremely dilute, the particles are in a collisionless condition. To treat such a collisionless plasma, the electrons and ions comprising the plasma are treated as individual particles. In such cases, it is a good approach to use the electromagnetic particle code in which the electric field and the magnetic field are solved progressively in time according to Maxwell's equations.To reconstruct on the computer, the environment around the spacecraft flying in space as closely as possible, the authors are developing the electromagnetic particle code in which the spacecraft is included as an internal boundary. This paper reports the numerical experimental results on the electromagnetic environment around the satellite which is formed when the spacecraft is exposed to a high‐speed plasma flow in a space plasma. A plasma flow is given from one end of the free boundary, and a spacecraft is placed in such a flow. By changing the parameters of the plasma, the physical quantities controlling the generation of the disturbance are found. In regard to the mechanism of the disturbance generation and the two‐dimensional configuration of the disturbance, several characteristics different from those predicted are obtai

ISSN:8756-6621    

DOI:10.1002/ecja.4410760205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThree‐dimensional power loss distributions generated inside the human body by the electromagnetic irradiation from a waveguide‐type applicator are analyzed using the finite‐difference time‐domain (FD‐TD) method. To execute the three‐dimensional FD‐TD analysis with a small amount of computation, only a limited small muscular region representing a part of the human body near the waveguide aperture is employed in the analysis region. In this case, the external boundaries of the analysis region are located in the human body which is composed mostly of lossy media. Thus, the conventional absorbing boundary conditions often are not applied effectively.In this paper, new absorbing boundary conditions are proposed so that the FD‐TD analysis can be executed as accurately as possible even if the external boundaries of the analysis region are located in lossy media. The waveguide‐type applicator, with which the human body is heated, is assumed to be filled with water and the radiated electromagnetic wave is assumed to be excited by the electric current on a post. To represent the electric current source on the post, the following two types of formulation method also are presented: 1) a method representing the electric current as the electric field source; and 2) the magnetic field source. Both methods are proved numeri

ISSN:8756-6621    

DOI:10.1002/ecja.4410760206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractChorus is one of the most important VLF/ELF emissions in the magnetosphere, but several points are still unsolved concerning their generation and propagation mechanisms.In this paper, the near‐equatorial direction‐finding measurements made on board a satellite are studied first and it is confirmed that the rising tone chorus (frequency of the chorus increases with time) is generated at θ (the angle between the wave normal and earth's magnetic field) ˜ 0° by the cyclotron resonance interaction with the energetic electrons.These results support the previous theory of Helliwell. Moreover, the direction‐finding measurements of the rising tone chorus are carried out aboard theGEOS 1satellite in the off‐equatorial regions. Their generation and propagation mechanism are studied with the help of three‐dimensional ray‐tracing computations and these results are compared with the corresponding results ofOGO 5direction‐finding measurements by Burton et al.As a result, the observations byOGO 5indicate that after the generation of chorus at the equator with wave‐normal direction θ0˜ 0°, it reaches the satellite in ducted propagation along the magnetic field line, whereas the results ofGEOS 1suggest that the waves are generated in a wider region near the equator with comparatively smaller θ0(30° ˜ 40°, at the most 50°) and that the subsequent propagation is nonducted in the magnetosphere.Finally, the direction finding measurements and the ray‐tracing computation are suggested to be very important in the study of generation and propagation of various emissions ge

ISSN:8756-6621    

DOI:10.1002/ecja.4410760207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractIn high‐speed digital mobile communication systems, one of the most spectrally efficient modulation methods is Gaussian‐filtered minimum shift keying (GMSK). In this paper, two decision schemes of frequency‐detected GMSK under frequency‐selective fading are compared theoretically from the viewpoint of bit error rate (BER) performances.The GMSK signal which is encoded differentially has an eye pattern with three levels; and, by using the characteristic, the offset decision is made. The BER performances of the offset decision method are compared with those of the conventional one which is based on the eye pattern with two levels.Under the frequency‐selective fading, which is characterized by a two‐ray model, the BER performances forBbT= 0.20 with the offset‐type decision are superior to those with the conventional one when normalized rms delay spread (τ/2Tfor two‐ray model, τ: delay spread) is less than 0.10.By using the post‐detection selection diversity with two diversity branches, we can reduce the degradation of signal energy per bit to noise power spectral density ratio with the offset decision greater than that with the conventiona

ISSN:8756-6621    

DOI:10.1002/ecja.4410760208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractWith the advent of the radio relay system and multilevel modulation, the multicarrier system and variable capacity transmission system are proposed to realize excellent performance in the fading channel. Accordingly, it is desired to realize a highly functioned MODEM which can cope with those systems in a flexible way.On the other hand, intensive studies have been made on digital signal processing in the modulation and demodulation in the field of data modem. However, these methods consider the low‐rate system of less than 100 Kbaud and are difficult to apply directly to the system where the transmission rate of 10 Mbaud or above is required.For the foregoing reasons, this paper considers the realization of the all‐digital modulator which can realize the high‐capacity transmission of over 10 Mbaud for the multilevel modulation system, such as 256 QAM.This paper discusses the design of the digital filter with excellent intersymbol interference. The condition for the carrier frequency for a given clock rate is presented. Then a variable multilevel modulator with a simple correction circuit is proposed which can be applied to the variable‐capacity transmission system.Finally, the proposed circuit is constructed and it is confirmed that an excellent modulation performance is obtained without adjustment in various multilevel modulation

ISSN:8756-6621    

DOI:10.1002/ecja.4410760209

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY