摘要:

The design and realisation of a reliable and simple subnanosecond electro-optic light switch is given. This switch is suitable for controlling a mode-locked laser, or for use as a light shutter where nanosecond or subnanosecond response is necessary. The direct-current and pulse responses of the longitudinal zcut XH2PO4modulator are considered in detail, and an optimum design established using KD2PO4with ring electrodes. The pulse-forming network employed incorporates several novel features, to produce an overall jitter time of less than 1 ns for a wavefront of 1–4.3kV and a risetime of 0.65ns.

DOI:10.1049/piee.1970.0206

出版商:IEE    

年代:1970

数据来源: IET

摘要:

A new procedure for realising the cascade and parallel forms of digital filters is presented. The method is based on using a Taylor expansion of the input signal over each sampling interval. The results reported in the paper are largely concerned with the simplest expansion, namely that the input remains constant during the sampling period. The method is shown to be applicable to lowpass and bandpass filters and, with a certain modification (which involves both delay equalisation and frequency doubling), to highpass and bandstop filters too. Another important feature of the method is that the gain at zero frequency is completely independent of the sampling rate. The time-and frequency-domain characteristics of several Butter-worth filters are studied. It is also shown that the so-called impulse-invariant technique of synthetising digital filters can be derived by approximating to the convolution integral in a special manner.

DOI:10.1049/piee.1970.0207

出版商:IEE    

年代:1970

数据来源: IET

摘要:

A new type of threshold-extension f.m.-signal demodulator containing no feedback loop and no limiters is described. The f.m. signal and a delayed version of it are applied to a homoheterodyne mixer, the difference-frequency output of which is then demodulated by a synchronous-phase detector. The paper describes the basic principle of the demodulator and presents a theoretical analysis of its behaviour. Although the theory has been confirmed in the laboratory, no attempt is made to describe its practical design and measured performance; this will be the subject of a later paper.The new demodulator—termed ‘autocorrelation’ because the signal processing is analogous to deriving the autocorrelation function of the signal—offers some significant advantages in f.m. radio links. It should enable greater threshold extension to be achieved in satellite links, especially when channel signal/noise ratios of 30dB or less are acceptable. Moreover, the fact that no feedback loop is required should prove attractive in applications where baseband frequencies extend to many megahertz.

DOI:10.1049/piee.1970.0208

出版商:IEE    

年代:1970

数据来源: IET

摘要:

The object of the paper is an examination of the lowpass and highpass step and impulse responses of filters using the Legendre polynomial approximation. As in previous papers, the response data are presented in tabular and graphical form for Legendre filters of ordern= 1, 2, …, 9, for passband tolerances of 0.5, 1, 2 and 3 dB. The salient features of the transient response of the Legendre filters are discussed and compared, in a general manner, to the corresponding transient response of the Chebyshev filters. Tables and figures not included in the summary are given in the complete paper.

DOI:10.1049/piee.1970.0209

出版商:IEE    

年代:1970

数据来源: IET

摘要:

A simple and fairly accurate method is presented for determining directly impedances and feeding conditions for an array of dipoles, resulting approximately in a desired radiation pattern. The method is applicable to arrays of identical thin centre-fed cylindrical dipoles, and lends itself particularly to the design of medium-wave antenna arrays. It is assumed that dipoles are parallel, nonstaggered and of lengths less, or not significantly greater, than the operating free-space wavelength. The results agree satisfactorily with available experimental results.

DOI:10.1049/piee.1970.0210

出版商:IEE    

年代:1970

数据来源: IET

摘要:

The theoretical efficiencies of class-D amplifiers are compared with those of conventional amplifiers by means of a power balance. As a result of certain similarities, it is suggested that class-AD and class-BD modes of operation should be defined. The class-D amplifier converts the collector dissipation of a conventional amplifier into load power components at a large number of modulation frequencies. When these are removed by filtering, a high overall efficiency results. The analysis presented includes an idealised treatment of the class-D amplifier with an inductive load, and enables constructive comparisons to be made.

DOI:10.1049/piee.1970.0211

出版商:IEE    

年代:1970

数据来源: IET

摘要:

Microwave tubes are known to exhibit low-frequency instabilities due to ion bunching. These instabilities are treated theoretically for an idealised model in two dimensions. The problem is rendered soluble by using supersized charge carriers whose equations of motion are formulated exactly by using complex variable techniques. These equations of motion are integrated numerically to obtain a complete solution of the idealised problem. The results agree with earlier experimental work and support strongly the qualitative theory of the instability. The computations enable one to predict ways of preventing its occurrence.

DOI:10.1049/piee.1970.0213

出版商:IEE    

年代:1970

数据来源: IET

摘要:

General formulas and equivalent circuits are given for a resonant cavity coupled to the end plane of a wave guide, inserted between two waveguides, and coupled to the sidewall of a waveguide. The aperture, the cavity and the waveguides are of arbitrary shape.

DOI:10.1049/piee.1970.0214

出版商:IEE    

年代:1970

数据来源: IET

摘要:

The field over an open-sided linear motor contains a rotating component which can be used to spin rotors of a variety of types. If the field of the linear motor is visualised as a magnetic ‘river’, the motion is analogous to a mechanical rack and pinion. The paper concentrates on reluctance- and hysteresis-type rotors which can develop substantial torque in small sizes. It is shown that the possible acceleration of steel rotors increases with decrease in size. The effect of linear-motor fields on iron and steel filings is investigated and a demonstration of rack-and-pinion action using a permanent magnet is described.

DOI:10.1049/piee.1970.0215

出版商:IEE    

年代:1970

数据来源: IET

摘要:

Following the discovery that a steel rod can be made to roll along the surface of a linear induction motor in the same direction as that of the travelling magnetic field, the phenomenon was investigated with a view to the development of a low-speed high-torque brushless a.c. motor. It was found that the torque was increased when the rod rolled at an angle to the direction of the field. The paper describes the development of a rotor motor using these principles in which the stator winding is conventional, except that the slots are very heavily skewed to make use of the angled-field effect. Some initial theoretical calculations are included.

DOI:10.1049/piee.1970.0216

出版商:IEE    

年代:1970

数据来源: IET