摘要:

AbstractThe reliability of air conditioning systems for next‐generation high‐power‐consuming telecommunication equipment is calculated taking into consideration the time delay effect. Also, a method is presented for improving the reliability of the air conditioning system. This method increases power supply reliability by sending the status information signal from the commercial power source to both the control equipment and the switch. Switching occurs only when the switch receives matching signals from both the control equipment and the power s

ISSN:8756-6621    

DOI:10.1002/ecja.4410761201

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

年代:1993

数据来源: WILEY

摘要:

AbstractIf the synchronous digital hierarchy (SDH) signal is converted into asynchronous transfer mode (ATM) cells to be transmitted through the ATM transport network, the efficiency of the operation/management/maintenance of the network will be improved in addition to maintaining the economy and reliability of the network. This is one of the advantages of the ATM transport network.This paper considers the system where SDH signal is transported by ATM technique. The delay variation produced in the ATM transport network is evaluated. Then the buffer readout control and the required buffer capacity are discussed. The order of processing between the delay variation smoothing function and other required functions in the proposed system is analyzed.

ISSN:8756-6621    

DOI:10.1002/ecja.4410761202

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

年代:1993

数据来源: WILEY

摘要:

AbstractIn the multichannel frequency division multiplex (FDM) optical transmission, the intermodulation distortion generated by the nonlinearity of the LD is a problem. In this paper, it is analyzed that for the number of transmission channel,N, and the optical modulation index per channel,m, the CSO and CTB are constant for a different value ofNif the effective optical modulation index, is maintained. The results are compared with experiments. In the present analysis, two types of nonlinearity of the current‐to‐optical conversion characteristics are considered. One of them is the nonlinearity near the bias current of the LD and is predominant in the region of a small effective optical modulation index. Another is the nonlinearity at the threshold value of the LD and is dominant when the effective optical modulation index is large. It is shown by means of the probability density function that the CSO and CTB degrade suddenly if the effect of the nonlinearity of the threshold value appears. In the FM‐FDM optical transmission, many distortions in the transmission bandwidth behave as the white noise due to frequency modulation when the carrier is frequency modulated by a video signal. Hence, the CN ratio is effectively degraded. In this paper, it is further presented that the CN ratio degraded by the distortions can be derived from the CSO and CTB by taking into consideration the frequency allocation of the FM s

ISSN:8756-6621    

DOI:10.1002/ecja.4410761203

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

年代:1993

数据来源: WILEY

摘要:

AbstractCommunications services and traffic have become varied with the development of communications and progress in telecommunications network control for call acceptance and routing has been desired. In implementing flexible control in communications networks, which are complicated systems, introduction of fuzzy control techniques which is an application of knowledge engineering is considered to be effective.To realize fuzzy control efficiently, it is necessary to establish appropriately membership functions that are quantitatively homologous with the target of control. However, finding and identifying such membership functions are difficult tasks.From this viewpoint, this paper proposes a method of tuning a membership function by learning and investigates call acceptance control in detail as an example. By this method, the input values to the fuzzy system and the revenues of the network are measured and optimal values are obtained automatically for various parameters of the membership functions by learning based on these data and the past tuning history. In this study, the efficiency of this tuning method is evaluated by simulation. As a result, it has been shown that by this method membership functions converge to appropriate forms and good control characteristics can be obtained.

ISSN:8756-6621    

DOI:10.1002/ecja.4410761204

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

年代:1993

数据来源: WILEY

摘要:

AbstractTrellis‐coded modulation (TCM) has good spectrum properties and excellent bit error rate (BER) performance. This paper presents the envelope control (EC) method which improves the transmitter power amplification efficiency of TCM for mobile radio. Applying EC to TCM leads to two new modulation schemes: smoothed envelope trellis‐coded 8 PSK (SE‐TC8PSK) and constant envelope TC8PSK (CE‐TC8PSK). Modulation and demodulation techniques for SE‐TC8PSK and CE‐TC8PSK are created. The spectrum properties, BER performance, and power‐conversion efficiency of SE‐TC8PSK and CE‐TC8PSK are calculated by computer simulations and compared with those of TC8PSK. EC greatly improves the power‐conversion efficiency at the cost of degrading the spectrum properties and BER performa

ISSN:8756-6621    

DOI:10.1002/ecja.4410761205

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe demand for expanded mobile communication capacity is increasing rapidly. It is expected that in addition to the currently used 900‐MHz band, the 1.5‐GHz band will have to be utilized. An antenna is designed so that it has the same sector beamwidth in both bands. The antenna is realized by placing a rod‐type parasitic element close to the driven element which is parallel to a corner reflector having a comer angle of 140°. The absolute beamwidth is determined by the corner

ISSN:8756-6621    

DOI:10.1002/ecja.4410761206

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

年代:1993

数据来源: WILEY

摘要:

AbstractWith the development of mobile communication, active research is being done on the small‐sized antennas such as microstrip antennas (MSAs). Moreover, MSAs normally are placed on spherical or cylindrical surfaces as a conformal antenna.Conformal MSAs are expected to have different characteristics compared to planar structure. In this case, numerical analysis is needed before the actual experiment.The method of analysis which has wide applications may be considered as efficient for this purpose. One such method is the conformal grids finite‐different time‐domain method (FD‐TD method).In this paper, an MSA on a curved surface is analyzed using the conformal grids FD‐TD method. Moreover, comparison with the experimental values also is performed. The experimental results and the analytical results are in close agreement which shows the validity of the method of analysis. As a result, it is confirmed that in the range of this paper, the input impedance and radiation pattern varies from their values for the planar patch when the patch surface

ISSN:8756-6621    

DOI:10.1002/ecja.4410761207

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

年代:1993

数据来源: WILEY

摘要:

AbstractTweek atmospherics have been used to estimate the physical quantities of the ionosphere and to understand the propagation mechanism of the waveguide modes due to the propagation characteristics. As the ionosphere, several realistic models which are anisotropic and inhomogeneous are used.From the theory of the waveguide mode of ionosphere and the ground surface, the propagation characteristics of the tweek atmospheric are evaluated theoretically. The results of the cutoff frequency and the polarization characteristics are compared with the measured data. The cutoff frequency of the first mode of the tweek atmospherics has been found to be very close to the measured value by means of the computation of the phase velocity and the attenuation constant on the actual waveguide in which the electron density profile by Reagan was used.The polarization of the 0th mode is extremely close to the linear polarization regardless of the electron density profile and agrees well with the measurement. The measured result of the polarization of the first mode is almost completely left‐handed circular at the cutoff frequency. This experimental evidence can be explained by the electron density profile by Reagan. However, it is found that the frequency dependence of the polarization at frequencies higher than the cutoff is substantially different from the measured data. Significant dependence of the polarization characteristics on the electron density profile and the earth's magnetic field suggests that the model of the ionosphere and the propagation characteristics of the waveguide mode can be estimated from the detailed measurement of the polarizatio

ISSN:8756-6621    

DOI:10.1002/ecja.4410761208

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

年代:1993

数据来源: WILEY

摘要:

AbstractThis paper proposes a new type of radial line microstrip antenna and studies both the design method and radiation characteristics. The following conclusions are obtained.(1) The relationship between the basic design parameters of this new type of planar antenna and the radiation characteristics was demonstrated, and the essential design data of this type of antenna were obtained.(2) A boresight antenna was fabricated based on the design data obtained in the foregoing, and it was shown clearly that such a type of antenna system offers an aperture efficiency of above 90 percent, ranging from the small‐aperture (low‐gain) type to the large‐aperture (high‐gain) type.(3) A beam‐tilt type antenna also was studied theoretically as well as experimentally, and the relationship of its radiation characteristics with the tilt angle and aperture efficiency was explained. It was demonstrated that such an antenna system may be considered to be effectively applicable as a high‐efficiency circularly polarized pla

ISSN:8756-6621    

DOI:10.1002/ecja.4410761209

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

年代:1993

数据来源: WILEY

摘要:

AbstractA ten‐element imaging array which consists of an integrated antenna‐detector system that incorporates trap‐loaded Yagi antennas and Schottky diodes has been developed for operation in the millimeter‐wave band around 70 GHz. Also, a prototype optical system that comprises a millimeter‐wave phase‐imaging interferometer has been designed and fabricated. They were fitted to the GAMMA 10 tandem mirror at Tsukuba University. A real‐time measurement of the radial distribution of the plasma electron density was successfully demonstrated using

ISSN:8756-6621    

DOI:10.1002/ecja.4410761210

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

年代:1993

数据来源: WILEY