DOI:10.1049/ree.1966.0024

出版商:IERE    

年代:1966

数据来源: IET

摘要:

The Selective Dissemination of Information or S.D.I, system is aimed at bringing to the individual scientist's attention only those new it e m s 0I" information that are of interest to him. This is done by comparing his subject interests in an electronic digital computer with the subjects covered by each document entering the information system, and printing out from the computer only those items which sufficiently match his interests. In this way a personal service can be provided to a large number of scientists, with feedback allowing progressive tailoring of the service to the needs of each individual.The National Electronics Research Council is at present engaged in the first stage of a three-year investigation of the value, economics and acceptability of the S.D.I, system for electronics research workers. Although the investigation will initially be confined to the subject of electronics research, the system developed will be immediately applicable to any other branch of science and technology.

DOI:10.1049/ree.1966.0025

出版商:IERE    

年代:1966

数据来源: IET

摘要:

In applications such as communication and Doppler systems, the f.m. noise performance of microwave sources is quite critical. The noise performance of X-band microwave sources using transistorized crystal oscillators and amplifiers and varactor frequency multipliers has been studied. The paper discusses the limitations due to the crystal, the associated oscillator, the amplifier and the multiplier and also the methods used to measure their contribution. Theoretical and experimental results are compared.

DOI:10.1049/ree.1966.0026

出版商:IERE    

年代:1966

数据来源: IET

摘要:

The minimum noise temperature of a parametric amplifier depends on the varactor junction capacitance, spreading resistance and its thermal temperature. The time-dependent junction capacitance remains nearly constant by cooling. But the spreading resistance remains constant with cooling only if the varactor is degenerately doped and has an abrupt p-n junction. Actually the junction region is slightly graded and therefore not degenerate. Thus the spreading resistance increases two or three times by cooling from room temperature to 4°K. The higher the thermal resistance of the varactor the more the spreading resistance is heated by the pump power. The measured thermal resistance of some diffused varactors is nearly the same at room and helium temperatures, while the thermal resistance of an epitaxial varactor increases sharply at very low temperatures. So the optimum pump frequency for minimum noise may be much lower than calculated from previous theories which neglect the pump heating. This is because the pump heating decreases with decreasing pump frequency and is of greater importance at low ambient temperatures. Considering the increase and the heating of the spreading resistance the minimum diode noise temperature of a helium cooled parametric amplifier at 4 Gc/s is calculated to be 3°–4°K. This agrees with measured data.

DOI:10.1049/ree.1966.0027

出版商:IERE    

年代:1966

数据来源: IET

摘要:

A paper on power dissipation in fourpole networks by A. Weissfloch is adapted to calculate the power dissipation in the input and output matching networks of an experimental varactor doubler and therefore to calculate the true input and output powers from semiconductor bulk material.Experimentally measured values of input and output power for specified biases are then compared with predicted values for the same biases calculated using an approximate analysis suggested by D. B. Leeson which assumes a non-linear depletion layer capacitance mechanism for harmonic generation.Reasonable agreement was achieved at power levels and biases which did not involve forward conduction. At higher power levels the results show that if charge storage does occur when forward conduction takes place then it does not enhance the efficiency to any greater extent than could be accounted for by depletion layer non-linearities.An analysis of the impedance changes of the varactor diode under high power conditions shows that this could account for the decrease in power loss in the surrounding circuits and could well explain the large increases in overall efficiency of the harmonic generator under these conditions.

DOI:10.1049/ree.1966.0028

出版商:IERE    

年代:1966

数据来源: IET

摘要:

The paper describes the design features of the highly reliable silicon planar transistors and a brief description of the ‘accelerated life test’ is given. These tests have to be carried out with high precision. The problem is discussed from the circuit designer's and the manufacturer's point of view and suggestions are made for obtaining reliable performance and a low rate of failure from the transistors

DOI:10.1049/ree.1966.0029

出版商:IERE    

年代:1966

数据来源: IET

摘要:

The tunnel diode is coupled weakly to a relatively highQresonator essentially of the hybrid, or re-entrant coaxial, type. This construction ensures a wide tuning range and a frequency of oscillation that is relatively insensitive to temperature change, supply voltage variations and interchange of diodes. In the basic form of the oscillator, using a 2 mA peak current germanium diode, stable and continuous oscillation is sustained over the full tuning range of 0.7 to 4.9 Gc/s with a power output greater than 1 μW up to 4 Gc/s. Alternative forms of the oscillator still under development give power outputs approaching 1 mW at some cost in tuning range.

DOI:10.1049/ree.1966.0030

出版商:IERE    

年代:1966

数据来源: IET

摘要:

From consideration of the factors influencing the design of varactor diodes for use in high-frequency parametric amplifiers and multipliers it appears that GaAs is the most suitable choice of semiconductor. The high carrier mobility of this material over a wide range of temperatures should enable high cut-off frequency varactor diodes tobe fabricated which will operate at the low temperatures required for ultra-low-noise parametric amplification. In addition, the high cut-off frequency should provide efficient harmonic generation at the higher microwave frequencies.An appraisal of the performance of an initial GaAs diode indicated that low frequency measurements were unreliable, and this has led to the development of a microwave measurement technique which has proved to be an extremely useful method of evaluating the junction parameters.As a result of these measurements new device structures have been evolved which reduce the microwave losses and simplify the fabrication processes. Three forms of diode have been developed for use at C, X and Q-band having cut-off frequencies of 150, 250 and 700 Gc/s (at zero bias) respectively, and the construction and performance of these varactors are described.

DOI:10.1049/ree.1966.0031

出版商:IERE    

年代:1966

数据来源: IET