An FPGA based implementation of baseband and passband modulation for wireless transmitters

There is a plethora of silicon options available for implementing the various functions of a transmitter, but FPGAs are an attractive alternative for many of these tasks due to performance, power consumption and flexibility. This paper presents a complete hardware architecture for transmitter which is then synthesized and mapped on the Spartan 3E FPGA kit. The transmitter carries out data formatting, NRZ line encoding, baseband modulation, pulse shaping and passband modulation. A ROM based raised cosine filter is designed to mitigate the effects of Inter-symbol Interference. Passband modulation is accomplished by designing hardware using Direct Digital Synthesizer. A dedicated module to introduce channel imperfections is also designed to study the behavior of transmitter on practical interfaces. The implemented sub-system is particularly suited for use in a typical WiMAX environment or any other SDR based system that performs downstream digital signal processing.