Simulation of algorithms for pulse timing in FPGAs

Modern Field Programmable Gate Arrays (FPGAs) are capable of performing complex discrete signal processing algorithms with clock rates well above 100 MHz. This, combined with FPGA´s low expense and ease of use, make them an ideal technology for pulse timing and are a central part of our next generation of electronics for our pre-clinical PET scanner systems. To that end, our laboratory has been developing a pulse timing technique that uses pulse fitting to achieve timing resolution well below the sampling period of the analog to digital converter (ADC). While ADCs with sampling rates in excess of 400 MS/s exist, we feel that using ADCs with lowing sampling rates has many advantages for positron emission tomography (PET) scanners. It is with this premise that we have started simulating timing algorithms using MATLAB in order to optimize the parameters before implementing the algorithm in Verilog. MATLAB simulations allow us to quickly investigate filter designs, ADC sampling rates and algorithms with real data before implementation in hardware. We report our results for a least squares fitting algorithm and a new version of a leading edge detector of PMT pulses.