Synthesis of mixed-signal designs from behavioral specifications must address analog-digital partitioning. In this paper, we investigate the issues in mixed-signal behavioral partitioning and design space exploration for signal-processing systems. We begin with the system behavior specified in an intermediate format called the Mixed Signal Flow Graph, based on the time-amplitude characterization of signals. We present techniques for analog-digital behavioral partitioning of the MSFG, and performance estimation of the technology-mapped analog and digital circuits. The partitioned solution must satisfy constraints on imposed by the target field programmable mixed-signal architecture on available configurable resources, available data converters, their resolution and speed, and IO pins. The quality of the solution is evaluated based on two metrics, namely feasibility and performance. The former is a measure of the validity of the solution with respect to the architectural constraints. The latter measures the performance of the system based on bandwidth/speed and noise.