Synthesis of Pulse-Shaping Networks in the Time Domain

Abstract

A fundamental problem in the design of data transmission systems is the synthesis of pulse-shaping networks which satisfy specifications in both the time and frequency domains. This paper considers the problem of designing a network to shape an arbitrary input pulse into a band-limited pulse having minimum intersymbol interference. The design procedure uses the zeros of the network transfer function to achieve the band-limiting properties (using a modified Temes and Gyi constraint) while the transfer function poles are optimized with a computer to give the desired time response. By limiting the specifications on the shaped pulse to an absolute minimum, very accurate results are achieved with simple networks. Some sample designs and experimental results are included. For example, an 11th order transfer function is designed to shape rectangular pulses for a synchronous baseband pulse amplitude modulation system. The shaped pulses have a bandwidth 20 percent in excess of the Nyquist bandwidth and a theoretical worst-case distortion of 2.1 percent. An active realization of this transfer function achieved a worst-case distortion of about 2.5 percent.