DOI:10.1049/ree.1968.0101

出版商:IERE    

年代:1968

数据来源: IET

摘要:

The transmitter power requirements for adequate field strength are evaluated for direct broadcasting in the present u.h.f. television bands. It is shown that improved aerials, the use of preamplifiers and wideband frequency modulation will be necessary for practical transmitters in existing or foreseeable space vehicles. The concept of ‘indicial bandwidth’ is introduced which is defined as the receiver bandwidth for which carrier/noise power-ratio is unity. Satellite considerations of power supply, station keeping and launching costs are discussed. The conclusion is reached that satellite broadcasting can most satisfactorily operate to stations feeding conventional wire broadcasting networks.

DOI:10.1049/ree.1968.0103

出版商:IERE    

年代:1968

数据来源: IET

摘要:

The existing methods of assessing computer performance are reviewed. The advantages and limitations of each method are discussed. Finally, possible future areas of study are indicated.

DOI:10.1049/ree.1968.0105

出版商:IERE    

年代:1968

数据来源: IET

摘要:

The dynamic behaviour of a computer system is analysed by representing it as a network of queues and phases which are then treated as a Markov chain.

DOI:10.1049/ree.1968.0106

出版商:IERE    

年代:1968

数据来源: IET

摘要:

The particular effects of noise upon logic gate and flip-flop circuits and the resultant general effects upon digital systems are considered. Common sources of noise are outlined andtheir significance in integrated circuit systems is considered. Such sources include crosstalk, reflections, common-earth impedance coupling and supply line noise.Present methods of assessment and specification of d.c. noise margin and a.c. or pulse noise immunity are reviewed and examples are given of the application of such methods to representative commercial integrated circuits.

DOI:10.1049/ree.1968.0107

出版商:IERE    

年代:1968

数据来源: IET

摘要:

The rapid development of thick film micro-circuits has created a need for preparations that will provide resistor films on a variety of substrates. Until recently the majority of theresistive preparations available required a firing profile with a peak temperature around 750°C, necessary to complete complex chemical changes within the glaze resistor. This not only imposed the need for very close control of the firing cycle and furnace atmosphere to ensure reproducible values, but limited the choice of substrate to materials, such as 95–98% alumina ceramics, capable of withstanding this temperature. A prerequisite to attaining consistent values is the surface condition of the substrate. Relatively low-cost materials like mica and glass, whichinherently possess flat, highly finished surfaces, are excluded, since they either exfoliate (dehydrate) or deform at temperatures exceeding 650°C.To overcome these limitations and take advantage of the mechanism of conduction through ruthenium dioxide a series of glaze resistor preparations has been developed. The objective was an ink based on a chemically-inert system that would be far less dependent on firing conditions than those hitherto available. To be viable thesystem has to be capable of producing a wide range of resistivities; possess acceptably low temperature coefficients; contain the spread of resistance values within narrow limits and be economically competitive. The use of valency control and the techniques adopted to achieve these requirements are described.

DOI:10.1049/ree.1968.0108

出版商:IERE    

年代:1968

数据来源: IET

摘要:

A passive R-C synthesis fornth order rational transfer functions is presented. The synthesis is very simple in application and the networks realized are of the parallel ladder type. The main features of this procedure are maximum gain, minimum number of components, and reasonable component value spreads.

DOI:10.1049/ree.1968.0109

出版商:IERE    

年代:1968

数据来源: IET

摘要:

The use of symmetrical and asymmetrical space charge limited (s.c.l.) square-law diodes as mixer elements is considered, and it is shown that low conversion loss is possible with the latter type. In order to achieve this a d.c. bias is necessary on the diode. Matching source and load resistances are higher than for the unbiased diode. The use of an idler termination at the sum frequency (p+q) is shown to have some advantages. The symmetrical diode is shown to be unpromising as a mixer element.

DOI:10.1049/ree.1968.0110

出版商:IERE    

年代:1968

数据来源: IET

摘要:

A receiver designed to measure the galactic noise spectrum in the range from 2 to 4.5 MHz and flown in theAriel IIIsatellite is described. Problems arising from the use of a loop antenna with a swept receiver and the exclusion of spurious signals from terrestrial sources and other experiments in the payload are discussed. Preliminary results indicate a marked coupling between the receiver and another experiment in the satellite by modulation of the local plasma. In certain conditions the coupling is small enough to be neglected and the galactic noise level can be measured with fair accuracy.

DOI:10.1049/ree.1968.0111

出版商:IERE    

年代:1968

数据来源: IET