Jitter Characteristics of Timing Recovery Scheme Using a Prefilter

摘要

Analysis of timing jitter is presented for a baseband polar system, BPSK and QPSK with AWGN. A cosine roll-off bandlimiting scheme is assumed. The timing recovery circuit is composed of a prefilter, a square-law device, and a timing tank. Normalized jitter spectral densities and rms jitter are defined and calculated in order to examine jitter characteristics in various systems in common. The normalized jitter spectral density for the S × S component becomes negligibly small for every roll-off factor. Therefore, the rms jitter is determined only with the S × N and N × N components. The S × N component is predominant for large E{sub}b/N{sub}0 and the total rms jitter is almost inversely proportional to the square root of E{sub}b/N{sub}0, Numerical calculation in QPSK for a tank Q of 100 shows that a jitter reduction effect of a prefilter exists when E{sub}b/N{sub}0 is greater than 10 dB and that the rms jitter decreases with increasing E{sub}b/N{sub}0 and increasing roll-off factor.