The Design of Hybrid Symmetric-FIR/Analog Pulse-Shaping Filters

This correspondence presents a method for designing linear-phase square-root (SR) FIR digital filters that alleviate the effect of receiver timing jitter. We take a newly conceived parameter, the “roughness” of the analog/FIR-SR filter impulse response, into account. We show that the error-performance of a system employing a matched SR filter pair, in the presence of receiver timing jitter, is more strongly related to how well the roughness parameter is minimized, than it is to the maximizing of the eye width caused by the Nyquist pulse. Design examples validate the proposition that the proposed method can lead to improved error performance of a high-order QAM communication system in the presence of receiver clock jitter.