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A matrix-based method of synthesising log-domain ladder filters is described. The nodal matrix equations characterising a LCR prototype are made directly realisable, facilitating the design of high-order filters. Different structures with a range of characteristics can be generated by a variety of matrix decompositions. The problem of floating capacitors normally required to realise transmission zeros in the log-domain is solved by matrix transformations. This avoids externally-LTV dynamics and hence distortion. Simulated results of different designs derived by various matrix decompositions validate the proposed procedures, which have been formalised in the CAD filter package XFILTER.
Date of Publication: 12 Aug. 2004