Digital frequency(sinusoidal) synthesizer using CORDIC algorithm

Abstract

Digitization of instrumentation and communications systems has encouraged a digitally controlled method of generating multiple frequencies from a reference frequency source called Direct Digital Synthesis (DDS). DDS systems are characterized by fast switching, fine frequency discrimination, low phase noise, and transient-free frequency changes. Frequency changes are phase continuous, which is desirable in phase or frequency modulation. The fast frequency switching is useful in frequency-agile and spread spectrum systems. Algorithms used in communication technology require the computation of trigonometric functions, coordinate transformations, vector rotations, or hyperbolic rotations. The coordinate rotation digital computer (CORDIC) is a rotation-based arithmetic computing algorithm which has found many important applications. CORDIC is not the fastest way to perform multiplications or to compute algorithms and exponentials, but, since the same algorithm enables the computation of most mathematical functions using basic operations of the form (a ± b) 2−i, it is attractive for hardware implementations. The paper aims at introducing the concept of DDS and briefly cover the various major phase to amplitude conversion techniques used before reaching to the CORDIC algorithm. It also aims to present a proof of concept of the CORDIC algorithm by comparing the results obtained by simulating the CORDIC algorithm in VHDL & the theoretical values.