FPGA implementation of a CDMA source coding and modulation subsystem for a multiband fluorometer with pattern recognition capabilities

We describe the design of a source coding and modulation circuit to be used in the front end of a multiband fluorometer device. The circuit uses a CDMA approach to minimize ambient and exogenous noise contamination and is implemented in a Xilinx Spartan 3 FPGA. The eight channel CDMA modulator and demodulator subsections use 1172 slices, or 61% of a XC3S200 FPGA, leaving ample room to embed a Microblaze IP core for spectral signature analysis and pattern recognition, and user interaction.