摘要:

In this paper the timing-jitter-suppression problem for partial-response systems is considered. In particular, by imposing the zero-derivative constraint on five practical classes of partial-response signals timingjitter suppression is achieved. For this purpose, an overall frequency-response design procedure is developed, and a minimum-bandwidth signalling scheme is introduced which results in a triangular filter followed by a tapped delay line, where the choice of taps depends on the type of partial-response signal used in the system. By introducing a recursive equaliser in the receiver the equaliser structure is redesigned and it is observed that some partial response signals result in an improved performance when operated in a recursive mode. In each case the performance characteristics are discussed.

DOI:10.1049/ij-ecs.1979.0032

出版商:IEE    

年代:1979

数据来源: IET

摘要:

The design of an antihangup system for 2-phase second-order phase-shift-keyed (p.s.k.) signal tracking systems is reported. Simulation studies indicate that the aided system exhibits improved performance over an unaided system in two respects(i) phase transient time may be reduced by up to an order of magnitude(ii) frequency acquisition time is reduced to the order of the phase acquisition time

DOI:10.1049/ij-ecs.1979.0033

出版商:IEE    

年代:1979

数据来源: IET

摘要:

In a spread-spectrum multiple-access communication system it is desirable to permit a number of users to simultaneously utilise the same channel. This can be achieved using code-division multiple-access techniques where the codes are very often maximal-length sequences. To permit reliable code-bit synchronisation and prevent multipath distortion, knowledge of the nonperiodic autocorrelation is necessary. The required autocorrelation may be obtained by simple modulo-two addition bit by bit, which, however, requires a large number of calculations even for moderate code lengths. From a computational aspect it is therefore of interest to obtain a simple algorithmic procedure which may lead to time saving. This paper discusses one such algorithm to ease the computation of the nonperiodic autocorrelation for maximal-length sequences.

DOI:10.1049/ij-ecs.1979.0034

出版商:IEE    

年代:1979

数据来源: IET

摘要:

This paper describes a method for designing 2-dimensional F.I.R. digital filters to an arbitrary phase, as well as gain, specification. Examples are given of filters designed using this approach.

DOI:10.1049/ij-ecs.1979.0039

出版商:IEE    

年代:1979

数据来源: IET

摘要:

This paper presents a method for the approximation of a transfer function with highQ-factor poles by a transfer function whose poles have a lowerQ-factor. The ratio of this new transfer function to the given transfer function approximates unity with a minimum deviation over the whole ω-axis. The method is based on rearranging all poles of a given transfer function, lowering theQof the highQ-factor poles and increasing theQof the lowQ-factor poles by interdependent movement in thes-plane. The resulting transfer function with decreased maximum £-factor has the same order as the original transfer function and a limit on the amount ofQ-factor lowering is shown to exist. The function obtained can be used as a first (and in many cases, sufficient) step of the approximation process. Further reduction of the approximation error is obtained by generating more complicated transfer functions. In these functions the multiplicity of all poles which are the poles of the first-step transfer function with decreasedQis increased simultaneously. The error decreases in a geometric progression with each step. The rapid growth of approximating-function complexity restricts the application of the proposed method to transfer functions with a small number of poles. A method for determining the poles and zeros of the approximating function is described and an example of approximation is given.

DOI:10.1049/ij-ecs.1979.0040

出版商:IEE    

年代:1979

数据来源: IET

摘要:

It is shown that the variation of a network functionF(ε)due to the presence of a parasitic element ε is approximately equal to the sensitivity of that function with respect to ε. Introducing the return difference with respect to e, a very simple expression for the variation ofF(ε)is obtained in Appendix 7, namely the product of the null-return difference with respect to ε and the sensitivity ofSεF(ε)i.e. the null-return difference sensitivity, or n.r.s. product. If the numerator of F(ε) is independent of ε, it is shown that the variation ofF(ε)due to ε is equal toSεF(ε)only. Various examples are given which demonstrate the usefulness of these results.

DOI:10.1049/ij-ecs.1979.0041

出版商:IEE    

年代:1979

数据来源: IET