摘要:

The history and development of air traffic control techniques are briefly outlined with particular reference to the rapid growth in the number of aircraft movements during and after World War II. The methods employed for the safe handling of large volumes of civil and military air traffic in crowded air space are discussed, and the systems of electronic position identification, guidance and communications currently used to support the management task are described together with their necessary performance characteristics. The growth predictions for air traffic movements and the demands which these will make upon the existing system performances are then examined. This is coupled with some speculative consideration of new techniques and systems which might possibly be introduced in the future.

DOI:10.1049/jiere.1988.0001

出版商:IERE    

年代:1988

数据来源: IET

摘要:

A signalling technique is described in which the sinusoidal spectrum envelope of a random Class 4 partial-response (PR) data signal is truncated at the first spectrum null, or maximum, with subsequent bandwidth expansion at the signal destination enabling data recovery from a reconstituted three-level waveform.The hypothetical case of signalling over a noiseless, ideal low-pass channel is used in order to show that the bandwidth-signalling speed relationship is a function of the digital correlation length; it is shown that a signalling speed indeterminately higher than that obtainable under the Nyquist criterion is conceptually possible as the digital data length approaches infinity.The practical case of using a digital correlation length of two digits in order to achieve a signalling speed twice that obtainable under the Nyquist criterion over a non-ideal low-pass channel is also considered.

DOI:10.1049/jiere.1988.0002

出版商:IERE    

年代:1988

数据来源: IET

摘要:

The Thames Water Authority recently commissioned a feasibility and design study to investigate the possibility of electronically automating the operation of the weirs along the Thames. The results of this study are incorporated in this paper and show that it should be possible to maintain the water level of each reach, measured with precision level sensors mounted above each weir, to within the order of ± 10 mm of a preset level at all times, regardless of water inflow rates, by the use of a distributed computer-based monitoring and control system. The design of this system relies on the use of an equivalent lumped rectangular cross-section model of a reach. The proposed strategy has been illustrated using data for the reach upstream of Caversham Weir and for the eight motorized weir gates at Caversham, Reading. The design has been verified using computer simulations which demonstrate that the system should be sufficiently robust to handle the expected variation of plant parameters.The system will be operated by a lock-keeper during daylight working hours, but will otherwise be unmanned. Accordingly, detailed consideration must be given to the practical implementation of the system so that it will provide the required degree of reliability and will degrade gracefully and fail safe. The paper discusses how these requirements may be achieved.

DOI:10.1049/jiere.1988.0003

出版商:IERE    

年代:1988

数据来源: IET

摘要:

The electromagnetic field measured in a screened room is dependent on the size and geometry of the room, the type of source (electric or magnetic dipole) and the dipole moment. In this paper, computer models based on TEM wave propagation within a screened room are used to describe the fields measured from a source inside the room. The models are used to predict the results of changes in the test set-up which enable qualitative measurements of the dipole type and moment to be undertaken.

DOI:10.1049/jiere.1988.0004

出版商:IERE    

年代:1988

数据来源: IET

摘要:

Static discharges on stay insulators of broadcast tower antennas can be efficiently eliminated by simple coils. Thus only relatively small RF voltages are left on the insulators, so that smaller and cheaper insulators can be used. A new method for evaluation of these RF voltages at insulators is presented, which can be used for the design of the insulators. The method is based on analysing the antenna and its stays as an integral wire structure. Mutual influences of the insulators, as well as influences of the stays on the antenna input impedance and radiation pattern are thereby properly taken into account.

DOI:10.1049/jiere.1988.0005

出版商:IERE    

年代:1988

数据来源: IET