Multi-bunch instabilities degrade beam quality through increased beam emittance, energy spread and even cause beam loss. A feedback system is used to suppress multi-bunch instabilities associated with resistive wall of the beam ducts, cavity-like structures, and trapped ions. A digital TFS (Transverse Feedback System) is in construction at the SSRF (Shanghai Synchrotron Radiation Facility), which is based on the latest generation of FPGA (Field Programmable Gate Array) processor. Before we get such FPGA digital board, investigation and simulation of the front-end were done in the first place. The signal flow was analyzed by SystemView. Construction and optimization of the entire system is our next goal.