DOI:10.1049/ree.1973.0024

出版商:IERE    

年代:1973

数据来源: IET

摘要:

The coupling together of the Decca Navigator and an automatic pilot has been achieved by the Decca Navigator Company using an Omnitrac computer. The method used is highly complicated and expensive to manufacture. This paper is a feasibility study of the possibility of solving the problem in a more economical fashion for marine applications.The proposals outlined employ a line following technique and could be adapted to suit any positional finding system using anx, y, tplotter as a sensing device to derive a path error signal.

DOI:10.1049/ree.1973.0025

出版商:IERE    

年代:1973

数据来源: IET

摘要:

The form of fields in a conical horn with uniform circumferential corrugations, when the corrugation depth assumes arbitrary values in the interval 0.25 ≦ (h/γo0) ≦ 0.5 is investigated in this paper. Assuming the corrugations to be infinitely thin and sufficiently close-packed, an impedance boundary condition is imposed on the fields in the axial region. Subject to a far-field approximation, accurate expressions are derived for the aperture field through a hybrid-mode formalism, which are subsequently used to calculate numerically the diffracted far-field of the horn supporting the HE11mode, using Silver's formula. Satisfactory agreement between calculated and measured values of the far-field pattern for a wide-flare horn having arbitrary values ofh/γosupports the validity of the theory presented. When the half-flare angle (α2:) is less than 30°, a closed form expression is derived for the on-axis gain of the horn.

DOI:10.1049/ree.1973.0026

出版商:IERE    

年代:1973

数据来源: IET

摘要:

A fully digital differential pulse code modulation (d.p.c.m.) system has been constructed to provide a flexible and stable basis for subjective optimization of a technique for efficient coding of video telephone picture signals. The experimental encoder accepts a precoded 8-bit p.c.m. input and delivers a 4-bit d.p.c.m. output which may be corrupted by simulated channel errors before decoding and display. The implementation of the system is described and photographic results of the coding technique are presented.

DOI:10.1049/ree.1973.0029

出版商:IERE    

年代:1973

数据来源: IET

摘要:

Direct conversion single sideband receivers are of interest because they are less subject to spurious responses than the conventional superheterodyne, do not entail the use of high-gain narrowband amplifiers with high centre frequency, and lend themselves better to integration in monolithic form.Two approaches to the design of receivers of this kind have been described: (1) the phasing technique, in which the local oscillator is tuned to the nominal signal carrier frequency and the unwanted sideband response eliminated by phase cancellation; (2) Weaver's ‘third method’, in which two oscillators are used, the first tuned to the centre of the incoming s.s.b. spectrum, and the second to the centre of the reconstituted a.f. spectrum.The characteristics of the two types of receiver are compared, and the superiority of the relatively neglected Weaver approach, particularly in a new a.c. coupled variant, is demonstrated, so far as the reception of speech modulated signals is concerned.

DOI:10.1049/ree.1973.0030

出版商:IERE    

年代:1973

数据来源: IET

摘要:

One method of designing non-recursive digital filters to arbitrary frequency specifications is to use optimization. However, the program will only minimize one particular performance index which may not give the ‘best’ filter for the particular application. Furthermore, when performing the optimization the errors at specified points are usually weighted and the weights are generally chosen in a fairly arbitrary manner. This paper describes how two different optimization runs can be used to give initial conditions which enable the final filter characteristic to be simply adjusted, interactively with the computer, thus avoiding the problem of how best to choose these weights.

DOI:10.1049/ree.1973.0031

出版商:IERE    

年代:1973

数据来源: IET

摘要:

The advent of on-line digital computers and relatively large-storage supervisory computers allows the possibility of improved control of processes containing pure time delay (distance/velocity lag). Such processes frequently occur in industrial plants and their control is also complicated by the fact that both the magnitude of pure time delay and the values of the parameters of the minimum-phase elements in the process may vary with time. Furthermore extraneous disturbances of time varying and unknown power spectra will cause further control difficulties. This paper contains an outline of a new general approach to this problem in which a digital computer is used as the main control element to implement a scheme designed to optimize the performance of such systems.

DOI:10.1049/ree.1973.0032

出版商:IERE    

年代:1973

数据来源: IET

摘要:

The use of recirculating shift registers in the implementation of binary transversal filters with quantized coefficients is discussed. Shift registers are employed in a serial processing mode to reduce circuit complexity at the expense of a lower maximum processing rate. An implementation of a 34-stage filter using standard m.o.s. shift registers is discussed in detail. Some alternative arrangements are considered.

DOI:10.1049/ree.1973.0033

出版商:IERE    

年代:1973

数据来源: IET