摘要:

One proposed method of reducing the channel capacity requirements for the transmissionof television signals over long distances is known as frame difference signal (f.d.s.) coding. This method implies the recoding of television signals so that only those parts of every frame are transmitted which are different in two consecutive frames. In order to assess the possible savings in channel capacity resulting from this technique, it is first necessary to measure and record the probability density of f.d.s. areas in actual television programme signals.In this paper an f.d.s. generator is described which, by using a vidicon camera tube as storageand subtracting device, produces frame difference signals suitable for of statistical analysis.The generated signals are further processed to obtain the frame by frame integral of the f.d.s.areas, and the ancillary equipment required to carry out this operation is described. The data are recorded for subsequent evaluation.

DOI:10.1049/ree.1965.0015

出版商:IERE    

年代:1965

数据来源: IET

摘要:

The paper describes a general-purpose computer program which may be used to calculate the performance of a wide variety of 2-port networks. The circuit to be analysed may contain 3-terminal active devices (such as transistors) provided their 2-port parameters are known, and there are no restrictions (apart from an upper limit to the size of the circuit) on the manner in which the resistors, capacitors, inductors and 3-terminal devices may be joined together. Thus the performance of amplifiers having multi-loop feedback paths can be analysed. The program is written in Elliott 803 Autocode, and can analyse a large feedback amplifier in a few minutes.

DOI:10.1049/ree.1965.0017

出版商:IERE    

年代:1965

数据来源: IET

摘要:

The characteristics of anode structures suitable for coldcathode high-power magnetrons have been investigated analytically and experimentally, with special emphasis on increasing the interaction and maximizing the area of coherent interaction with the electron beam at a given frequency. The structures analysed were designed for large mode separation, high interaction impedance, and easy coupling to the output circuit. They may be applicable to travelling-wave amplifiers; some circuit characteristics of the structures are therefore also included.

DOI:10.1049/ree.1965.0018

出版商:IERE    

年代:1965

数据来源: IET

摘要:

The paper relates to the design of hydrophone or antena arrays together with the associated signal processing networks.For the detection of weak signals in a noise background the outputs from the individual receivers may be combined by means of linear amplifiers and time delays. For a signal of known time dependence and spatial form there is an optimum set of processing networks which maximizes the signal/noise ratio at the output.A general theory, developed in a previous paper, is applied to consideration of line and crossed arrays. Several types of noise are considered. The analysis is also extended to treat multiplicative arrays. Application of the theory is to consideration of a crossed array in which some of the outputs are combined linearly and then multiplied at the output stage.

DOI:10.1049/ree.1965.0020

出版商:IERE    

年代:1965

数据来源: IET

摘要:

The conditions whereby interaction anomalies which occur in transmitting arrays could arise in acoustic or radio receiving arrays are established. It is concluded that the effect will only occur in special cases: for close packed resonant acoustic arrays and for radio arrays with thick dipoles arrayed asymmetrically.

DOI:10.1049/ree.1965.0022

出版商:IERE    

年代:1965

数据来源: IET

摘要:

This paper treats the antenna as an information processing device. By representing the antenna as a spatial (as well as temporal) frequency filter, information theory concepts can be applied so as to maximize the information content or rate at the system output or to minimize the information content in the system error. Rather than attempt to satisfy classical antenna design criteria such as maximization of gain, minimizing of side-lobe level, etc., the approach used here is to optimize the system by maximizing the useful information rate of the receiver subject to the physical constraints of the system.A convenient way of evaluating and comparing different signal processing systems is to determine their respective output information rates. Various non-linear as well as linear processing systems can be compared on this basis.For linear, one-way antennas, the optimum antenna in most cases is one which has uniform shading. For linear, two-way antennas, the optimum shading is non-uniform. The theory is illustrated with a nonreciprocal two-way array whose parameters are adjusted so as to yield the optimum antenna system according to the above criteria.

DOI:10.1049/ree.1965.0023

出版商:IERE    

年代:1965

数据来源: IET

摘要:

Coupled wave theory is applied to the absorption type ferrite modulator. The importance of the quantities (αx— αy)/K and (βx—βyK) in determining the attenuation of the incident polarization are thereby demonstrated. For maximum attenuation we require (αz—αy)/K= −2 and (βz— βy)/K = 0. Some experimental data confirming the effect of the quantity (αx— αy)/K on the loss of the incident polarization are given.

DOI:10.1049/ree.1965.0026

出版商:IERE    

年代:1965

数据来源: IET