摘要:

Assurances of a long service life will often be demanded of m.o.s. integrated circuits used in telecommunication equipment. An attempt has accordingly been made to identify failure risks and devise life-prediction procedures by accelerated testing, ambient temperature being the primary stress variable. The test vehicle, manufactured on a volume production line, had a simple circuit configuration permitting direct access to its constituent transistors and allowing each of them to be operated under different electrical conditions. The parameters monitored included threshold voltages, both of the transistors and of a spurious device, gain factors, transistor resistances (in the conduction mode), leakage currents and protective-diode breakdown voltage. The most significant response was obtained from the transistor threshold voltages, which change substantially but in a manner consistent both with the electrical operating conditions and with known physical theories of charge instability in the m.o.s. system. It is suggested that at least the drift of transistor threshold voltage is amenable to a life-prediction procedure, and it is shown how the results could be exploited for procurement-specification purposes.

DOI:10.1049/piee.1971.0083

出版商:IEE    

年代:1971

数据来源: IET

摘要:

A control computer is described which uses a serial digital program to control an arithmetic unit and storage system working entirely in the analogue mode. Storage is capacitive, using field-effect-transistor switches for data selection. Using conventional techniques, speeds of 20μs per arithmetic operation are readily obtainable. The first application of this computer is to aircraft-gas-turbine control. A control program, for example, of a Rolls Royce Olympus 593B engine occupies 120 instructions, and the computation has a recursion time of 3ms. An accuracy of within 0.1% is obtainable.

DOI:10.1049/piee.1971.0084

出版商:IEE    

年代:1971

数据来源: IET

摘要:

An investigation of the design philosophy of large floating-point -arithmetic units has been undertaken, with a view to establishing the principles for constructing such a unit for a large high-speed computing system. The main consideration applied was maximum speed for a reasonable cost in a machine handling numbers 30–64 bits in length. Consideration of compatibility with other systems was specifically excluded, although the unit to be implemented does take this factor into account. Within these constraints, it is shown that negative numbers should be represented in twos-complement form. Numbers of upto 64 bits in length would be handled, with the binary point at the less significant end of the mantissa. Rounding should be performed by forcing a ‘carry in’ to the least significant bit when the answer is more than single length, sufficient information being retained to enable multilength arithmetic to be implemented. Answers should not be normalised. The data presented are sufficient to indicate the effect of applying different criteria.

DOI:10.1049/piee.1971.0085

出版商:IEE    

年代:1971

数据来源: IET

摘要:

An attempt has been made to review the methods of multiplication available for use in a large high-speed computing machine. Number lengths of 50 to 60 bits and multiplicatiion times of less than 0.5 μs were the design aims. Suitable multiplier units will make use of carry-save adders to reduce the time for each addition cycle, and will decode several multiplier bits in each cycle to reduce the number of cycles required. The number of carry-save adders to be used is set largely by economic considerations. The number of multiplier bits to be decoded in each cycle is determined by the time required to form multiples of the multiplicand prior to cycling. It is shown that the best compromise between cost and speed is achieved if two or three carry-save adders are used in a serial-parallel configuration, and three or two multiplier bits are decoded in each cycle, respectively. A comparison with several other multipliers is made. A method for incorporating carry assimilation at the less significant end of the product is described, thus requiring the final propagate addition to be only single length, while still retaining the full double-length result. An indication of the effect of number length on the conclusions is inclued, but is not worked out in complete detail.

DOI:10.1049/piee.1971.0086

出版商:IEE    

年代:1971

数据来源: IET

摘要:

A method is presented for analysing isolated symmetrical dipoles and two such parallel nonstaggered dipoles immersed in a homogeneous conducting medium. The results obtained by the present theory are in good agreement with experimental results. The theory is restricted to relatively thin dipoles, and the lengths of the dipoles should not considerably exceed the operating wavelength measured in the conducting medium. An interesting conclusion is reached that the usefulness of the idealised delta-function generator, commonly used in the linear-antenna theory, is restricted to media for which, approximately, σ/ωε<1.

DOI:10.1049/piee.1971.0087

出版商:IEE    

年代:1971

数据来源: IET

摘要:

A method of antenna analysis is presented which gives the current distribution and input impedance of finite conical antennas. The results for the impedance are identical with those obtained from the 'mode theory', but the results for the current have the advantage that they are found in closed form. In addition, the method is much more easily applied. A very general method of obtaining the characteristic impedance of an antenna which is a section of a spherical transmission line is also described, and this method is applied to the folded triangular monopole.

DOI:10.1049/piee.1971.0088

出版商:IEE    

年代:1971

数据来源: IET

摘要:

Results are presented from measurements of the signal strength made in an aircraft flying northwards from the 16kHz transmitter GBR, Rugby, England, on four days in June 1969, near the epoch of maximum, solar activity. The interference pattern due to the combination of ground and sky waves is found to change significantly with local time, whereas the change between different days at the same local time is small, even though the conditions of magnetic and solar activities have changed. This implies that, for the present observations, the influence of the Sun's position was more marked than that of the magnetic or solar conditions. The pattern is similar to, but extends, those of Budden, Ratcliffe and Wilkes3and of Weekes4, which were also made at solar maximum.

DOI:10.1049/piee.1971.0089

出版商:IEE    

年代:1971

数据来源: IET

摘要:

A very high-sensitivity S band radar capable of detecting targets with radar cross-section of 5 × 10−10m2of reflectivities of 2 × 10−15m−1at a range of 10km has recently been brought into operation for meteorological studies of the clear atmosphere. The paper outlines the constraints set by the meterological requirements, and describes the radar which has been assembled to meet them. Examples are presented of clear-air echoes obtained both from extensive horizontal layers at hieghts up to 3 km, and also from high-altitude clear-air turbulence.

DOI:10.1049/piee.1971.0090

出版商:IEE    

年代:1971

数据来源: IET

摘要:

Modern turbogenerators have large airgaps for system stability. This airgap space can be used to accommodate the a.c. windings of the machine, instead of placing them in slots. In the paper, the disadvantages of windings in slots are discussed, together with problems that will result from putting the winding in the airgap. Using a published design for a conventional 750 MW machine and converting this to an airgap-winding design, it is shown that the size and weight of the total machine are considerably reduced, with corresponding reductions in cost and transportability. Since it is desirable that a practical airgap winding should pass through the stator bore, so that it can be prefabricated as a complete cylinder, the normal winding is discussed and is shown to be difficult to make as a cylinder. A concentric winding, proposed by the author, which has normal winding factors in the active region and which can be made as a cylinder, is described. Simplified calculations for forces between phase bands and for leakage reactance are given. These forces will have to be calculated in detail later, but the simplified calculation shows that they can easily be contained by modern reinforced resins. The leakage reactance is shown to be considerably reduced; this is important as an indication that there will be little need for transposition in the radial direction. A simple method of threading the rator through the airgap winding is described.

DOI:10.1049/piee.1971.0091

出版商:IEE    

年代:1971

数据来源: IET

DOI:10.1049/piee.1971.0092

出版商:IEE    

年代:1971

数据来源: IET