DOI:10.1049/ree.1983.0046

出版商:IERE    

年代:1983

数据来源: IET

DOI:10.1049/ree.1983.0047

出版商:IERE    

年代:1983

数据来源: IET

DOI:10.1049/ree.1983.0048

出版商:IERE    

年代:1983

数据来源: IET

摘要:

A present-day sound mixing desk accepts a number of audio signals from microphones and/or tape machines and can be used to alter the tonal character of the signals, change the sound level, mix signals together and route them to selected outputs. An example of the use of a mixing console is given and this general treatment is then extended to a discussion of the advantages that can be obtained by implementing the mixer functions in digital form. An experimental digital mixer is described and the advances in hardware processing techniques since the inception of the equipment briefly reviewed. Finally, an indication is given of the form of the next generation of digital mixing consoles.

DOI:10.1049/ree.1983.0049

出版商:IERE    

年代:1983

数据来源: IET

摘要:

The factors involved in the planning and construction of the IBA's u.h.f. fourth channel network and the overall technical design requirements of the main transmitting stations are discussed in terms of the environmental, reliability and performance requirements. Transmitter configurations and the philosophy adopted for the control and monitoring systems are presented. The decision to introduce a new type of klystron which results in savings in both cost and building space is contrasted against the other available options of tetrodes or older type klystrons. Unattended operation is used at all sites and consequently a major goal is reliability, both in terms of failure rate and stability of performance and the results obtained discussed. Stringent filtering is required of the lower sideband transmitted at high-power transmitter sites using Ch. 21. The station supervisory system uses microprocessor-based control and monitoring techniques. The programme input equipment arrangements are also discussed. The decision was made to use all solid-state transposers up to the 200 W power level, at u.h.f. relay stations.

DOI:10.1049/ree.1983.0050

出版商:IERE    

年代:1983

数据来源: IET

摘要:

Experimental measurements of the velocity of blood cells have been used in research into the early detection of cancer in patients. These measurements have been made by manually timing cells moving across a television screen. This technique is tedious, involves the timing of over a hundred cells and is therefore subject to error. A low-cost microcomputer system was designed to automate the measurement of cell velocity in order to give faster and more accurate results.

DOI:10.1049/ree.1983.0051

出版商:IERE    

年代:1983

数据来源: IET

摘要:

This paper reports the results of a series of measurements designed to determine the viability of using conduction current techniques for data transmission in the offshore platform environment. The results show that ranges predicted some authors for conduction current systems in the open were not observed in practice. In particular, measurements conducted in the vicinity of a large metallic underwater structure show an increase in signal strength accompanied by a reduction in bandwidth compared with open sea case. The signalling rates which could be accommodated in the vicinity of an under water structure approximately 75% of the corresponding rates in the open sea. The noise amplitude at each test site was considerable, being composed predominantly of harmonics of land based power frequency. Such noise can be reduced acceptable levels using filtering techniques. For high signal-to-noise ratios a typical signalling rate at a range of 100m in the open sea was found to be 200 baud.

DOI:10.1049/ree.1983.0052

出版商:IERE    

年代:1983

数据来源: IET

摘要:

Non-uniform time-delay-and-integrate (n.u.t.d.i.) devices have been designed and used for fast beam scanning. The possibility of using such devices for very high angular resolution is examined and it is shown that there must be a trade-off between the number of angular resolution cells and the scanning rate. It is shown however that an improved sector scanning sonar may be realized by combining modulation scanning with time delay scanning. It is also shown how the n.u.t.d.i. device can be used to advantage for solving the ambitious problem of two dimensional beam scanning.

DOI:10.1049/ree.1983.0053

出版商:IERE    

年代:1983

数据来源: IET

摘要:

Besides the backscattered amplitude measurements of a conventional sidescan sonar, the Bathymetric Sidescan Sonar (BASS) makes simultaneous measurements of the depth of sea bed throughout the sidescanned area. It does this by determining the angle of the returning wavefront at each instant in time and combining the result in an appropriate manner with the range measurement. The depth information be used to generate contour maps. It can also be used to generate stereoscopic images of the sea bed. A potential cause of major errors in the depth measurement is surface multipath interference and special features are introduced into the transducer design to avoid this.

DOI:10.1049/ree.1983.0054

出版商:IERE    

年代:1983

数据来源: IET