摘要:

The gain-bandwidth performance of a filter-type degenerate parametric amplifier incorporating two synchronously pumped varactor diodes is analysed for general conditions, in which the source and load are not necessarily matched to the characteristic impedance of the filter. The diodes are the shunt capacitive elements in a conventional bandpass filter. Experimental work carried out in the h.f. band confirms the theory. The potential bandwidth of this type of amplifier is very great.

DOI:10.1049/piee.1967.0266

出版商:IEE    

年代:1967

数据来源: IET

摘要:

A parametric amplifier in which two varactor diodes are incorporated in a low-pass filter has been analysed when the phase of pumping of the diodes differs by ±π/2. It is shown that good forward gain can be achieved with concomitant unity gain in the reverse direction. The theory is verified by experimental work on an amplifier operating in the h.f. band.

DOI:10.1049/piee.1967.0267

出版商:IEE    

年代:1967

数据来源: IET

摘要:

Highly interconnected networks to be used for the distribution of high-speed digital information are currently the subject of design studies by both civil and military research organisations. One problem in such networks is that any frequency asynchronism between the oscillators which control digit switching at trunk exchanges can result in loss of information. Methods of controlling the frequency of oscillators to develop a common average frequency at all exchanges and so prevent information loss are discussed in the paper.The absence of a reference frequency, coupled with the effects of transmission delay between exchanges, can result in a controlled frequency which is outside the tolerance band of the uncontrolled frequencies. This feature applies when a linear control characteristic is employed and leads to an argument which favours a nonlinear characteristic. Control-loop stability is discussed, the bandwidth of the circuit used to extract digit-timing information being shown to be a critical factor affecting stability.

DOI:10.1049/piee.1967.0268

出版商:IEE    

年代:1967

数据来源: IET

摘要:

The various causes of modulation in the input circuit of a constant-resistance ring modulator (in which input modulation is ideally absent) are analysed theoretically and discussed on the basis of the analysis and of experimental results.

DOI:10.1049/piee.1967.0269

出版商:IEE    

年代:1967

数据来源: IET

摘要:

The paper analyses the ranges obtained using digital transmissions and frequencies in the range 30–300kc/s. Parameters are assumed which could be met by a mobile installation using solid-state amplifiers and a wire antenna supported by a captive helicopter. The calculations are for both binary and 32-ary f.s.k. modulation, and they take into account groundwave and skywave propagation, fading and noise. The results are expressed in terms of the percentage probability of achieving a given range during the two least favourable periods, namely, summer afternoons and late-spring evenings. With a radiated power of 50kW and a single teleprinter channel operating at 60 words per minute, ranges of about 400 km can be achieved at all times with high for frequencies of 50kc/s or lower, ranges the order of 700km are possible. At these lower frequencies, the range can even be extended to 2000km, if reliabilities of only 90% and error rates of 1 in 102are tolerable.

DOI:10.1049/piee.1967.0270

出版商:IEE    

年代:1967

数据来源: IET

摘要:

A new circuit is proposed which uses a bridge network for the timing element. The square-wave generator consists of anRCbridge network, a voltage comparator and a pair of electronic switches. The circuit analysis in the paper shows that the generator is self compensating with respect to power-supply variations and to variations in the active circuit components. The frequency stability therefore depends almost entirely on the stability of the passive components in theRCbridge network, and a stability of 10−3is readily obtained over a wide range of frequencies. The circuit proposed is very suitable for practical application, particularly at low and very low frequencies.Measurements taken on an actual bridge square-wave generator are in good agreement with the results of the circuit analysis.

DOI:10.1049/piee.1967.0271

出版商:IEE    

年代:1967

数据来源: IET

摘要:

A triangular stepped helical aerial, that is a helical aerial in which the axial length varies in discrete steps rather than continuously, has the same relative wideband radiation and impedance characteristics of a conventional axial-mode helical aerial, despite its discontinuous structure. The observed radiation and impedance characteristics of an equilateral-triangular stepped helix radiating in the axial mode are reported.The method of deriving the far field of such an aerial is outlined, assuming an unattenuated travelling wave along the length of the conductor.

DOI:10.1049/piee.1967.0272

出版商:IEE    

年代:1967

数据来源: IET

摘要:

The theory of surface-wave propagation around sharp corners in single-wire transmission lines is developed. Two main topics are studied: radiation loss at corners and radiation patterns of corners. An integral expression is obtained for the transmission loss of a corner, and theoretical curves are computed for the entire range of corner angles from 0° to 180°. The theoretical curves are in good agreement with experimental results obtained by the authors and also with some published results by other investigators. In addition, some new features of acute corners are analysed in some detail. For the radiation patterns of the corners an explicit formula is derived, from which a whole range of radiation patterns is calculated and compared with experimental results. The agreement is shown to be good for corners with obtuse angles.

DOI:10.1049/piee.1967.0273

出版商:IEE    

年代:1967

数据来源: IET

摘要:

Diaphragms made of ferrite slabs or metal diaphragms with ferrite screens have nonlinear susceptibility dependent on the applied transverse direct magnetic field. Such diaphragms, employing D type ferrite material, have been used at frequencies of 9 and 10GHz for coupling to a cavity, and measurements of v.s.w.r.,Qfactor and impedance have confirmed theoretical predictions that by altering the magnetic field it is possible to tune the cavity. Similar elements can be used in variable directional couplers etc.

DOI:10.1049/piee.1967.0274

出版商:IEE    

年代:1967

数据来源: IET

摘要:

The paper outlines the derivation of a constant-speed transient torque solution for a polyphase induction motor for any switching condition. A representative selection of computed torque/time patterns is given, for a 5hp motor, including all torque components. These are compared with actual experimental results. Also for this motor, the way in which the transient negative torque varies with speed is shown for the speed range zero to three times synchronous speed. For speeds above synchronous value, it has been found necessary to use values of rotor parameters corrected for the skin effect of the speed-frequency transient currents.Simple approximate expressions are given for evaluation of the maximum positive torque peak during starting from test and the maximum negative peak when the supply is connected when the rotor is rotating at some finite speed. The results given by such expressions are compared with values obtained from both computed and recorded torque/time patterns for motors up to 100hp.

DOI:10.1049/piee.1967.0277

出版商:IEE    

年代:1967

数据来源: IET