In-Phase and Quadrature-Phase Sinusoidal Signal Generation Using DDS Technique

In-phase and quadrature-phase (IQ) sinusoidal signals are used as bases functions in many phase modulation schemes in communication systems. Generating such signals in engineering education laboratories without higher-end signal generators is quite challenging. Most of the time, the IQ signals used in undergraduate engineering education laboratories are in audio frequency range that is used to demonstrate or experiment with various phase modulation schemes. This paper presents a method to generate IQ sinusoids in the audio frequency range using direct digital synthesis technique. The system developed is simulated using MathWorks (R) Simulink and implemented on commonly available Xilinx's(R) Spartan 6 FPGA. The system designed is capable of producing phase correct sine and cosine waves having frequencies between 1 Hz and 20 kHz.