IEE Journal on Electronic Circuits and Systems
Volume 2, Issue 5, September 1978
Volume 2, Issue 5
September 1978
Self dual l.t.a. filters
- Author(s): H.G. Dimopoulos and A.G. Constantinides
- Source: IEE Journal on Electronic Circuits and Systems, Volume 2, Issue 5, p. 137 –142
- DOI: 10.1049/ij-ecs.1978.0027
- Type: Article
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p.
137
–142
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In this paper self-dual linear transformation active (l.t.a.) filter structures are introduced. The general linear transformation approach is constrained to this end to produce the necessary and sufficient conditions for self duality from which active-RC realisations of given lossless ladder filters are effected. Further degrees of freedom within the self-dual concept are then effectively utilised to produce active-RC realisations of highly modular form. These concepts are developed in this paper and are also applied to the design of two filters, the performance of which is most satisfactory.
Even-degree elliptic function monolithic crystal filters
- Author(s): S.K.S. Lu
- Source: IEE Journal on Electronic Circuits and Systems, Volume 2, Issue 5, p. 143 –146
- DOI: 10.1049/ij-ecs.1978.0028
- Type: Article
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p.
143
–146
(4)
In monolithic crystal filter design even-degree elliptic function lowpass prototypes of the types designated b and c have been used. However, monolithic crystal filters designed from the original evendegree elliptic function are not only feasible but also more selective. An example of the filter, using cascade synthesis, is given.
Some results on the nature of a 2-dimensional filter function possessing certain symmetry in its magnitude response
- Author(s): P. Karivaratharajan and M.N.S. Swamy
- Source: IEE Journal on Electronic Circuits and Systems, Volume 2, Issue 5, p. 147 –153
- DOI: 10.1049/ij-ecs.1978.0029
- Type: Article
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147
–153
(7)
Constraints on analogue and digital two-dimensional filter functions so that they possess various symmetries like quadrantal symmetry and circular symmetry in their magnitude responses are derived. An ideal circularly symmetric separable magnitude squared function is obtained. Approximation of the ideal function in analogue and digital domain is carried out and the contour plots of the responses of the resulting functions show that they are very nearly circularly symmetric.
Erratum: Experimental study of the radar cross-section of maritime targets
- Author(s): P.D.L. Williams ; H.D. Cramp ; Kay Curtis
- Source: IEE Journal on Electronic Circuits and Systems, Volume 2, Issue 5, page: 154 –154
- DOI: 10.1049/ij-ecs.1978.0030
- Type: Article
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154
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Computer-aided cascade synthesis of passive networks
- Author(s): Tri T. Ha
- Source: IEE Journal on Electronic Circuits and Systems, Volume 2, Issue 5, p. 155 –158
- DOI: 10.1049/ij-ecs.1978.0031
- Type: Article
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155
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Livsic's theory on the decomposition of the state space into invariant subspaces is combined with the QR algorithm for finding the eigenvalues of the state-variable matrix to yield an efficient method for computer-aided synthesis of passive networks. The synthesis is presented for scattering and transfer-scattering matrices which are widely used in practical problems.
Fast adaptation of equaliser and desired response for digital data receivers
- Author(s): Hoang B. Doan and Antonio Cantoni
- Source: IEE Journal on Electronic Circuits and Systems, Volume 2, Issue 5, p. 159 –166
- DOI: 10.1049/ij-ecs.1978.0032
- Type: Article
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The paper considers the design of the equaliser and the desired overall system impulse response (d.i.r.) for various types of detection algorithms used to recover digital data which has suffered intersymbol interference. The joint optimisation of the equaliser and desired response is formulated using a mean-square error cost. A constraint on the desired response is introduced which enables simple adaptive algorithms to be derived for determining the optimum equalizer and d.i.r. One of the algorithms considered has been found to converge rapidly and is thus ideally suited for application where fast start-up is required. Simulation results of the probability of error performance of various detection algorithms, using the equaliser and d.i.r. designed according to the approach developed in the paper, are presented. These results show that the performance obtained is comparable to that achieved with systems in which the equaliser and d.i.r. are designed according to other techniques. The disadvantage of these other techniques is that they usually lead to algorithms which are difficult to make adaptive and are slow to converge.
Minimising the effects of filter overlap in multiband signal/noise improvement systems
- Author(s): G.R. Hoffman and D. King
- Source: IEE Journal on Electronic Circuits and Systems, Volume 2, Issue 5, p. 167 –171
- DOI: 10.1049/ij-ecs.1978.0033
- Type: Article
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(5)
Multiband signal processing is used in complementary audio noise-reduction systems to overcome the effects of the wideband noise modulation that occurs during changes of gain. Because practicable filters with a finite cutoff rate must be used to define each signal band, changes in the relative gains of adjacent signal bands in the frequency spectrum give rise to distortion in the overall amplitude/frequency characteristic. This paper is concerned with methods of applying gain-dependent correction to the time constants of each filter. Computer optimisation techniques have been used to evaluate filter-parameter correction factors, enabling a linear frequency response to be retained for differences in gain between adjacent channels of up to 12 dB.
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