Patrick Lindecker wrote: > Hello Robert, > > TKS for the correction. I returned to my books. LMS filters are in > general linear (LMS-FIR), however they can also be in a recursive > structure (LMS-IIR).
Patrick, thanks for your reply. An IIR filter (with an FIR component and a feedback component) is still a linear filter. Even if you are adapting it, it is still a linear transfer function for each and every sample. The transfer function is Sum(Outputs * Feeback_coeffients) = Sum(Inputs * FeedForward_ Coefficients is linear on both sides and this is an IIR. The adaptation is funky and may be a nonlinear adaption, but at each sample instant a linear filter is applied to all samples in its delay lines and so no mixing can occur. Now, if you are thinking about decision directed LMS equalizers, where you make a hard decision as the output, that is most decidedly nonlinear. You do not hard limit the output of your NR filter! The typical AGC circuit in a receiver is more nonlinear than any LMS based NR filter, FIR, IIR, etc. could ever be. Bob > > >We agree that they are no good for digital modes. > Yes the a priori is not very favourable. > > 73 > Patrick > 73's Bob N4HY -- AMSAT Director and VP Engineering. Member: ARRL, AMSAT-DL, TAPR, Packrats, NJQRP, QRP ARCI, QCWA, FRC. ARRL SDR WG Chair "Taking fun as simply fun and earnestness in earnest shows how thoroughly thou none of the two discernest." - Piet Hine
