process for the production of digital nyquist filters without interference between symbols and corresponding filter arrangement

摘要

The invention concerns a method for producing a Nyquist digital filter with null interference between symbols, designed to process a physical signal transmitted between a transmitter and a receiver via a transmission channel, said filter being a symmetrical filter P(z) = F2(z) of order N using an oversampling factor M=4, and forming an adapted pair comprising a transmitting filter and a receiving filter, the polyphase decomposition of F(z) being written: F(z) = F0(z4) + z-1F1(z4) + z-2F2(z4) + z-3F3(z4). The invention is characterised in that N is different from 4n, n being an integer, and: If N=4n+1, F1(z)F1(z) + z-1F2(z)F2(z) = gamma z-n; If N=4+2, 2F0(z)F0(z) + F21 (z) + z-1F23(z) = gamma z-n; If N=4n+3, F0(z)F0(z) + F1(z)F1(z) = gamma z-n, F being the mirror symmetry of F and gamma being a non null constant.