Wa. Frank, AN EFFICIENT APPROXIMATION TO THE QUADRATIC VOLTERRA FILTER AND ITS APPLICATION IN REAL-TIME LOUDSPEAKER LINEARIZATION, Signal processing, 45(1), 1995, pp. 97-113
Nonlinear filtering based on the Volterra series expansion is a powerf
ul and popular approach in signal processing. However, a serious probl
em is the increased filter complexity as compared to linear filtering.
This paper presents an efficient approximation to the second-order Vo
lterra filter. The proposed filter structure, called multi-memory deco
mposition (MMD), is composed of three linear FIR filters and one multi
plier. Hence, the number of required filter operations is linear in th
e filter memory length. MMD coefficient determination with respect to
a second-order reference kernel is presented. Additionally, block-orie
nted and adaptive algorithms are proposed which calculate the filter w
eights from input and output measurements of an unknown system. The go
od performance of the MMD model is demonstrated by simulations and in
a real-time application. Therefore, the linearization scheme for the c
ompensation of nonlinear distortions with a preprocessor is introduced
. The preprocessor was implemented on a DSP system to reduce the nonli
near distortions of electrodynamic loudspeakers in real-time. The resu
lts show the gain in performance if an MMD filter is used instead of a
Volterra filter. This is due to the fact that with a given computatio
nal power longer memory lengths can be achieved by the MMD model.