FPGA implementation of cordic algorithm used in DDS based modulators

Abstract: The modern communication systems and software radio based applications demands smart transceivers, consisting of only an antenna and a fully programmable circuit with digital modulators and demodulators. A basic communication system’s transmitter modulates the amplitude, phase or frequency proportional to the signal being transmitted. An efficient solution (that doesn’t require large tables/memory) for realizing universal modulator is CORDIC (CO-ordinate Rotation Digital Computer) algorithm. The CORDIC algorithm is used in the rotation mode, to convert the coordinates from polar mode to rectangular mode. CORDIC is a versatile algorithm widely used for VLSI implementation of digital signal processing applications. This paper presents how to use CORDIC to implement different communication subsystems that can be found in software defined radio. Specifically, it shows how to use CORDIC to implement direct digital synthesizers and ASK, PSK, FSK Modulators. The focus of this paper is to analysis and simulation of ASK, FSK, PSK modulation scheme using Direct Digital Synthesizer having CORDIC algorithm at the place of ROM Look up Table. CORDIC Algorithm provides many significant advantages over Conventional ROM Look up Table.

Keywords: Software Defined Radio, CORDIC algorithm, DDS, ASK, FSK, PSK.