摘要:

AbstractThe utilization of Ku‐band satellite broadcasting and satellite communication is progressing. A high stability of oscillation frequency is required for local oscillators of receiver converters used in such communication. Therefore, analytical and experimental examinations have been carried out for the oscillation principle and the stabilizing method for oscillators using a common drain GaAs FET without an external feedback circuit and a very high‐Qdielectric oscillator.First, the output admittance of the common drain FET oscillator is calculated using GaAs FET small‐signal parameters to clarify the oscillation principle. Next, the oscillation frequency characteristics are analyzed and it has been shown that it is necessary to reduce the variation of oscillator output susceptance with the applied voltage to stabilize the oscillation frequency. The addition of a capacitive admittance to the oscillator source output is effective for this purpose.In an oscillator with a 0.02 S capacitive stub formed at the source output, oscillation frequency of 10.678 GHz, temperature variation of less than 600 kHz (‐20°C ∼ +60°C), and phase noise of ‐95 dBc/Hz (offset frequency: °10 kHz) have

ISSN:8756-6621    

DOI:10.1002/ecja.4410720301

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

年代:1989

数据来源: WILEY

摘要:

AbstractThis paper considers the design and experimental result of an audiographic teleconferencing terminal which applies document and telewriting as media for teleconferences via 64 kbit/s transmission lines, in addition to voice. For an effective teleconference, it is desirable that the terminal realize common visual space and have a paperless facility. First, this paper shows that distributed memory allocation is appropriate to the file configuration and proposes a document retrieval method which uses visual information. Also input/output function and display function suitable for teleconferencing terminals are discussed. Next, human interface which is suitable for teleconferencing terminals is discussed, and a key design pattern and its operational characteristics are shown. Finally, the experimental result of a fabricated prototype is shown.

ISSN:8756-6621    

DOI:10.1002/ecja.4410720302

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe characteristics of packet transmission delay in a continuous ARQ (Go‐Back‐N type) system are analyzed here. The copies of each packet stored in the buffer are sent to reduce the delay. The optimum copy size minimizing the delay depends not only on packet error probability and round‐trip propagation delay but also on offered traffic intensity. It is possible to reduce the delay by transmitting many copies and using the residual transmission capacity when offered traffic is light. On the contrary, when offered traffic is heavy, transmission of few copies is preferable in consideration of the number of lost copies for a successful transmission. Finally, considering that packet error probability may be reduced in some practical situations, the relation among packet error probability, propagation delay and traffic density where the optimum copy size changes from 1 to 2 is de

ISSN:8756-6621    

DOI:10.1002/ecja.4410720303

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe performance of the spread‐spectrum multiple‐access communication system is analyzed assuming that channel access from each terminal (station) is random. By distinguishing the retransmission traffic load from the freshly originating traffic load, a more accurate formula for message delay can be derived. By comparing the performance between this communication system and the FDMA, this system is shown to have higher usage efficiency of the channel bandwidth. Moreover, the processing gain optimizing the system performance is obtained as the function of the mean offered load. Using this fact, we consider the group random access scheme where all terminals are grouped according to their utilization forms if possible. Then each group uses the separate channel whose bandwidth is determined in accordance with the offered load, and its performance is evalua

ISSN:8756-6621    

DOI:10.1002/ecja.4410720304

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

年代:1989

数据来源: WILEY

摘要:

AbstractA scattering problem of two parallel conducting plates of finite widths is analyzed by a new formulation. It was shown that an analysis of multiple scatterings by a system of parallel plates can be obtained formally by the representation of the scattered fields by one plate. The representation was derived for scattered waves using Wiener‐Hopf simultaneous equations which must be satisfied by each scattered field. Through an approximate integral by the saddle point method, we obtained numerically the diffraction patterns concretely for the far‐field diffracted waves. In a case where the distance between edges of parallel plates is almost or more than one wavelength, we showed that a system of conducting plates can be analyzed taking into account multiple scatterings by the present formulat

ISSN:8756-6621    

DOI:10.1002/ecja.4410720305

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe frequency of switching dc‐dc converters has become higher when their size and weight must be reduced. When a higher frequency is chosen, some related phenomena become problems. These include the increase of the transition loss of the switching, the increase of magnetic energy in leakage inductances of a transformer, and high‐frequency noises. These problems can be solved at the same time by utilizing the resonance‐arc of the switching mode. Notably, a mode in which the applied switching voltage becomes the resonance‐arc is suitable for an increase of the frequency.This paper analyzes a dc‐dc converter, based on the concept of a class‐E power amplifier which is useful for solving the three forementioned problems. The design of the converter and its characteristics which are useful for understanding the behavior of the converter, are also given. As an inherent characteristic of the resonant switching mode, there is a period in which a part of the energy stored in the resonance circuit returns to its input. By using the duty ratio of the switch in this period, the switching characteristics, such as the transition of a mode and the input/output voltage ratio,

ISSN:8756-6621    

DOI:10.1002/ecja.4410720306

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

年代:1989

数据来源: WILEY

摘要:

AbstractA cutoff cavity antenna is proposed in which excitation and parasitic posts are placed inside the antenna cavity. The input impedance of the antenna can be varied freely and matched. Its fundamental characteristics are obtained theoretically. The values of the load reactances which were connected externally to those posts are controlled and can be matched for a desired operating frequency. The current distribution on the excitation and parasitic posts and the electric field distribution over the aperture were analyzed. Integral equations for those distributions were derived and solved by Galerkin's moment method. In addition, the determinantal equation to obtain matched load reactances was obtained. Numerical examples were presented for the current distribution and the aperture electric field under a matched condition. Experiments were conducted on a test antenna and the validity of the theory was discussed.

ISSN:8756-6621    

DOI:10.1002/ecja.4410720307

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

年代:1989

数据来源: WILEY

摘要:

AbstractHigh‐speed packet switching is a promising technology for multimedia communications in such wide‐band ISDN as speeches, images, and data. In this type of high‐speed packet switching, priority‐transmission technology will be effective, since a different packet‐transmission quality (e.g., transmission delay and loss‐rate) is required for each medium. This paper analyzes a nonpreemptiveMi/G/1( Ni)system which is the basis of the priority transmission system. In addition,n‐priority classes (wherenis arbitrary) are treated using models of the Poisson arrival, general service‐time distribution, and individual waiting‐position type, while conventional analyses are limited to two priority classes. To obtain packet loss‐rate and delay characteristics, this paper analyzes mainly the marginal distribution of each priority class. The results of the analysis include an extension of the Cooper‐Gebhardt relationship which formulates the relationship between distributions at an arbitrary moment and after the completion of a service. For the packet loss characteristic and delay‐time characteristic and their approximate calculation methods, the reader is referred to t

ISSN:8756-6621    

DOI:10.1002/ecja.4410720308

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

年代:1989

数据来源: WILEY

摘要:

AbstractHigh‐speed packet switching is a promising method in the wide‐band ISDN system for such multimedia as speeches, images and data. In high‐speed packet switching, conditions (e.g., transmission delay and loss rate) required for the transmission quality of packets are different in each medium. The priority‐packet transmission method will satisfy these conditions. This paper is based on the results of analysis of the non‐preemptiveMi/G/1( Ni) method [6], describes the evaluation of the characteristics of the priority‐transmission system, and proposes their approximation methods. Numerical computation of a three‐priority‐class model was carried out assuming such multimedia as speeches, images and data. The results show that:1It is possible to design the number of buffers independently for each priority‐class2the traffic characteristic of each Priority‐class is not affected significantly by changes of traffic ratio of the class Saving a higher priority than its own.Two approximation methods are proposed: a method based on an approximation that marginal distribution is independent in ch priority class; and 2 a method using result (2); both me

ISSN:8756-6621    

DOI:10.1002/ecja.4410720309

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe low‐frequency crosstalk loss characteristics are analyzed by a statistical method which derives the mean square of the crosstalk coupling. The theoretical formulas are derived for the near‐end and far‐end crosstalk losses in which mismatch terminations are taken into consideration. From both the theoretical and experimental viewpoints, the frequency dependence, terminal impedance dependence and cable length dependence of the crosstalk loss are studied. At low frequencies below a few tens kilohertz, both the near‐end and far‐end crosstalk losses decrease at the rate of 20 dB/decade for an increasing frequency. In the case of the terminal impedance of about 100 ω, the near‐end crosstalk loss decreases at the rate of 20 dB/decade for the increase of the terminal impedance. The far‐end crosstalk loss has a larger decreasing characteristic than this. Further, in the near‐end crosstalk, the crosstalk component at the far‐end due to the reflection at the cable end causes the cable length dependence in which the crosstalk loss decreases at 10 dB/decade for the increase of the cable length. In the case of far‐end crosstalk, the crosstalk of the forementioned far‐end is superposed on the intrinsic crosstalk. Therefore, the crosstalk attenuation decreases at th

ISSN:8756-6621    

DOI:10.1002/ecja.4410720310

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

年代:1989

数据来源: WILEY