摘要:

The paper discusses the lessons learned from several years of investigation into the performance of a large air traffic control data processing system. To achieve the twin requirements implicit in the title, the time between faults must be made as long as possible, whilst the time required to clear a fault must be reduced to the minimum. The practice of building up some degree of system redundancy with stand-by equipment is also one that can be employed to ensure that the occurrence of a fault does not cause an appreciable loss of system facilities.The experimental air traffic control system, on which the original findings were based, illustrates the feasibility of designing a high standard of reliability into data processing equipment. Extensive data on the performance of the system have since been analysed and used to improve further the reliability factor.

DOI:10.1049/ree.1968.0015

出版商:IERE    

年代:1968

数据来源: IET

摘要:

In this note a new TEM junction switch is described which is based on the three-port junction circulator. Microwave switching is achieved by applying a current waveform through a single wire loop inserted in each of the ferrite disks. In this way the demagnetizing fields of the ferrite shape and the eddy currents in the junction housing are eliminated. The magnetic energy is now determined by the inductance of a single wire turn and is extremely small. The switch can either be continuously modulated by a square current waveform or can be latched by short current pulses between the two remanence states of the closed ferrite shape.

DOI:10.1049/ree.1968.0016

出版商:IERE    

年代:1968

数据来源: IET

摘要:

The main features of the design and operation of the system are described. The techniques employed in the design and fabrication of the equipment are discussed in relation to the need for reliable operation in orbit,low power consumption and low weight. A brief account is given of the performance of prototype equipments during ground testing, and of the flight equipment since the launch of the satellite.

DOI:10.1049/ree.1968.0017

出版商:IERE    

年代:1968

数据来源: IET

DOI:10.1049/ree.1968.0019

出版商:IERE    

年代:1968

数据来源: IET

摘要:

The signal noise ratio of a quantum detector is considered under conditions where background illumination is the dominant noise component. It is shown that this is a function of the optical (pre-detector) and post-detector bandwidths. To obtain as general a case as possible, the modulation (information) signal is assumed to be white-noise of a defined bandwidth.Two separate methods of analysis are used. The first method assumes that the received light may be described in terms of its electromagnetic field while the other assumes that simple quantum theory is more appropriate. The first approach is valid for high levels of background radiation, the second for low levels. Theoverlap is shown to be in the region where the average quantum rate is just sufficient to define the pre-detector bandwidth—a result which is in agreement with sampling theory.The results are shown to be applicable to superhetrodyne and homodyne (synchronous detection) detectors by suitable parameter adjustment.

DOI:10.1049/ree.1968.0020

出版商:IERE    

年代:1968

数据来源: IET

摘要:

The experiment is designed to measure O2concentration from 150 km upwards with wide geographical coverage. The attenuation of solar ultra-violet light of 1425 Å to 1490 Å is observed as the satellite enters and leaves the Earth's shadow. The ultra-violet sensors used in the experiment are four gas-filled ionization chambers each of which produces about 10"11 amperes in full sunlight above the molecular oxygen layer. These four chambers all feed into a single electrometer valve amplifier whose circuit and performance are outlined. The constraints on the layout and mechanical structure of the experiment are discussed and the final experiment package is described. An outline is given of the performance of the equipment in orbit.

DOI:10.1049/ree.1968.0021

出版商:IERE    

年代:1968

数据来源: IET

摘要:

The very-low-frequency receiver carried by Ariel HI makes synoptic studies at 3-2, 9-6 and 16 kHz of the world-wide distribution and occurrence of natural v.l.f. phenomena such as whistlers, chorus and hiss and also determines the configuration of the wave-field above the ionosphere due to the GBR (Rugby) transmission at 16 kHz. At these three frequencies the peak, mean and minimum signals are measured in each 28 second period (~2°) around the orbit. This report is based on a preliminary analysis of 36 orbits (quick-look data). Zones of emission, mainly hiss, are present on every orbit. They occur at both high and medium latitudes and may often extend over 20° in invariant latitude and down to within 20° of the geomagnetic equator.Whistlers, at medium latitudes, are usually easily identified by the large peak, very low mean and zero minimum signal levels. The,signal amplitudes often vary rather smoothly along the orbit and the pattern of signal amplitude may be repeated on different orbits following the same sub-satellite path.The geomagnetic field and the D-region are the main factors determining the configuration and intensity of the GBR (Rugby) 16 kHz wave-field above the ionosphere. Signals were identified at locations as remote as the Antipodes and the North Pacific.

DOI:10.1049/ree.1968.0022

出版商:IERE    

年代:1968

数据来源: IET

摘要:

Callendar's ‘curve distortion criterion’, Sd, and a factor, Kr, in his power gain expressions are simply related to the ‘performance factor’, n and ‘inherent performance factor’, n1of the linear two-port active network. A lower limit of 10, proposed earlier for the ‘invariant stability factor’, s, is shown as equivalent to a lower limit of 4 for Sd. The role of the performance factor in the maximum power gains of mismatched and optimum unilateralized single active stages is emphasized. Finally, variations in thetotal port immittance due to changes in terminating immittance at the opposite port are expressed in terms of the performance factor

DOI:10.1049/ree.1968.0023

出版商:IERE    

年代:1968

数据来源: IET