Direct Digital Synthesizer (DDS)

Definition: A Direct Digital Synthesizer (DDS) is a digital signal processing technique used to generate precise and agile analog waveforms (typically sine waves) from a fixed-frequency clock source.

Main Components:

• Phase Accumulator: Adds the frequency tuning word (FTW) each clock cycle to generate a phase ramp.
• Phase-to-Amplitude Converter: Maps phase values to amplitude values using a lookup table (e.g., sine ROM).
• DAC (Digital-to-Analog Converter): Converts digital amplitude values into an analog output signal.

Key Features:

• High frequency resolution
• Fast frequency switching
• Phase continuity during switching
• Low phase noise (dependent on clock and DAC)

Applications: RF signal generation, function generators, modulation systems, radar, test equipment.

Common ICs: AD9833, AD9850, AD9910 (Analog Devices), MAX2871 (Maxim).