Asymmetric filter combination for a digital transmission system

摘要

The combination comprises a finite impulse response (FIR) filter (F1) inserted between the digitiser (AD) and the modulator (M1) of the transmitter (T). An infinite impulse response filter (F2) is placed between the demodulator (D1) and the digital signal processor (D2) of the receiver (R). The overall transfer function fulfils both the Nyquist criterion and the noise matching criterion. The infinite impulse response filter includes two all-pass networks in parallel branches, whose outputs are subtracted. The subtrahend branch contains one all-pass network, and the minuend branch has the other all-pass network in series with a 1/z delay stage.