DOI:10.1049/ree.1984.0051

出版商:IERE    

年代:1984

数据来源: IET

摘要:

The potential market presented by small users is considered and the characteristics of the present systems of communication satellites are reviewed. The satellite parameters of antenna gain and directivity and of bandwidth are then discussed and the operational considerations of the existing satellites are examined with reference to the requirements of the proposed small mobile users. The implications of economic tariffs arebriefly touched upon.

DOI:10.1049/ree.1984.0053

出版商:IERE    

年代:1984

数据来源: IET

摘要:

A recently developed three-stage Darlington transistor is described which has been specifically designed for direct off-line power control. The device features fast, low-loss switching with direct drive from an integrated circuit. The transistor has been designed with a very extensive safe operating area so that a snubber network is not required. The device is sufficiently robust to survive a number of system fault conditions and when used in conjunction with a suitable drive circuit, it can even withstand a short circuit load without damage.

DOI:10.1049/ree.1984.0054

出版商:IERE    

年代:1984

数据来源: IET

摘要:

A high-speed local area network that uses a bus architecture and spread spectrum techniques to overcome the problems of contention in a system with distributed control is described. Each node uses a pseudo-random binary code to modulate the data to be transmitted, effectively ‘spreading’ the bandwidth of the signal, and may transmit independently without first sensing the media. Interference between simultaneous transmissions is avoided by the careful selection of the codes used.The paper presents a technical description of the system developed and compares its performance with other bus networks. The choice of codes to be used, and their effect on the maximum number of nodes allowed and the data rate is discussed. The performance of the system in a noisy environment is also considered.

DOI:10.1049/ree.1984.0055

出版商:IERE    

年代:1984

数据来源: IET

摘要:

The role of ion implantation in the fabrication of optical waveguides in lithium niobate is describedtogether with a review of work carried out in this field. In addition the waveguide structure and the process parameters which determine its characteristics are outlined. Finally, the implications of this technology forthe fabrication of more complex integrated optical devices are discussed.

DOI:10.1049/ree.1984.0056

出版商:IERE    

年代:1984

数据来源: IET

摘要:

Results are presented of observations extending over a decade of propagation by means of sporadic-E ionization at frequencies in the range 59 to 77 MHz. The seasonal, diurnal and longer term trends in the data are discussed. Cumulative distributions of event durations are presented for different groupings of the data. A limited study of possible polarization discrimination at these frequencies is also described. The results are discussed in terms of their potential use in spectrum planning at frequencies around 70 MHz.

DOI:10.1049/ree.1984.0057

出版商:IERE    

年代:1984

数据来源: IET