摘要:

The older method of ionospheric predictions based on solar and ionospheric indices is described and the difficulties are illustrated. A new method which has been in use for three years and which makes no use of solar indices is described. The method also provides world charts of measured values offF2which form part of a permanent volume covering the whole range of ionospheric variation.

DOI:10.1049/pi-b-2.1962.0173

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The paper describes the theory and performance of a new microwave mixer based on the fact that the Hall electric field produced at any point in a semiconductor is dependent on the vector product of the current density and the magnetic field applied at that point. This mixer stage behaves differently from the more conventional forms in that the output contains only components of the local-oscillator and signal frequencies.Two designs of Hall-effect mixer were developed, and their conversion properties were experimentally investigated at about 10Gc/s. The best value achieved for the conversion loss was 57 dB with a local oscillator power of 10W and using a semiconducting film of indium antimonide having a Hall mobility of 0.173m/s per V/m. It should be possible to improve the efficiency of this mixer by using higher-mobility films and higher power for the local oscillator, and by operating the device at low temperatures.Besides being a linear device, the Hall-effect mixer has a power-handling capacity which is much larger than that of the ordinary crystal mixer. Moreover, the technique used offers a useful method for measuring the Hall mobilities of carriers in semiconductors at microwave frequencies.New information is also given about a technique for the preparation of evaporated indium-antimonide films which proved to have a Hall mobility as high as one-fifth of the material in bulk.

DOI:10.1049/pi-b-2.1962.0174

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The paper discusses the results of an experimental investigation concerned with the transverse magneto-resistance effect in very thin semiconducting films situated in a microwave field at 10Gc/s, with a superimposed steady magnetic field, of flux density up to 0.45 Wb/m2, applied at right angles to the surface of the film. The film used was of indium antimonide with a thickness of the order of 103Å, much less than the skin depth at the frequency employed. It was deposited by evaporation in a vacuum on a thin sheet of mica and placed longitudinally in a rectangular waveguide with the surface of the film parallel to the narrow wall of the guide, in much the same way as in the ordinary vane-type attenuator. The steady magnetic field, applied transversely to the film, produces a change in its conductivity and a corresponding effect on the microwave transmission properties. This magneto-resistance effect is related to the mobility of the carriers in the semiconductor, and consequently the technique enables this mobility to be determined without the use of electrodes attached to the specimen.

DOI:10.1049/pi-b-2.1962.0175

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The method which was developed by the author for analysing a simple cylindrical cavity with radial vanes has now been extended to the case of an interdigital resonator. The effect of the interdigital anode is taken into account in terms of modes of high orders, which are present only in the immediate vicinity of the anode. An approximation to the stored energy associated with these modes can be obtained by considering the equivalent static case. The effect of the vanes is accounted for by considering trial fields which satisfy the boundary conditions at the vanes. The evaluation of frequency proceeds by iterative steps, which essentially involve matching fields across an assumed dividing surface passing through the tips of the vanes. To get successively better approximations to the field distribution, variational principle is used.

DOI:10.1049/pi-b-2.1962.0176

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The new method presented is suitable for rapid testing of i.f. and microwave amplifiers under operational conditions. The input to the amplifier under test is a carrier simultaneously modulated in amplitude and phase, and the output is displayed on an oscilloscope by a spectrum analyser having special facilities for comparing the two sidebands and rejecting the carrier frequency. The technique of measurement is based on compensating the unknown phase modulation of the output signal with the known input phase modulation, the exact equality being indicated by noting the coincidence and minimum value of the two sidebands. The a.m.-to-p.h.m. conversion is then read on two instruments calibrated directly in decibels and degrees, and the a.m. compression is determined by reading the decibel scale of a u.h.f. attenuator.The new method is compared with those already known from the literature, and it is stated that the accuracy of measurement is primarily determined by the accuracy of measuring attenuation. A short analysis, upon which the new method is based, is given, and data for the equipment actually built are included, together with some typical oscillograms.

DOI:10.1049/pi-b-2.1962.0178

出版商:IEE    

年代:1962

数据来源: IET

DOI:10.1049/pi-b-2.1962.0179

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The causes of the residual errors in tapped-decade inductively-coupled voltage dividers are examined together with the additional errors which arise when several decades are interconnected to provide multiple adjustable ratios. Means for controlling or reducing these errors are considered, and an account is given of the construction and performance of a seven-decade divider whose errors at 1 kc/s do not exceed 1 part in 107of the output voltage for ratios between 1 : 1 and 0.1 : 1, and 1 part in 108of the input for ratios between 0.1 : 1 and 0.01 : 1.

DOI:10.1049/pi-b-2.1962.0180

出版商:IEE    

年代:1962

数据来源: IET

DOI:10.1049/pi-b-2.1962.0181

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The transmission of digital information by variation of the energy level of pulses of fixed shape is limited by channel distortion even in the absence of noise. For a fixed number of levels there is a maximum rate at which information can be transmitted without error—a rate which depends, in general, on the number of levels chosen. The nature of this dependence is examined for several classes of received pulse-shape. It is not generally true that the maximum rate increases with the number of levels, although this result can be obtained with a proper choice of received pulse-shape. The case of a channel with an exponentially decaying impulse characteristic, for which the maximum rate is independent of the number of levels, is of special interest as a large class of passive linear networks has this characteristic at least asymptotically. TheRCtransmission line when resistively terminated is a member of this class and the maximum rate of transmission over it is in fact approximately independent of the number of levels; when reflectionlessly terminated, however, it behaves in a quite different way.

DOI:10.1049/pi-b-2.1962.0182

出版商:IEE    

年代:1962

数据来源: IET

DOI:10.1049/pi-b-2.1962.0183

出版商:IEE    

年代:1962

数据来源: IET