Our final year project is DDS, which was first proposed by J.Tierney in 1971. Direct digital synthesis (DDS) is a method used to create forms of wave and arbitrary digital frequencies from a single frequency source. While VLSI technology also meets the requirements of various modern communication systems, direct digital synthesizers have been widely used as wireless transceivers since the 1980s. Direct digital frequency synthesis (DDS) consists of a digitally controlled oscillator (NCO), which is a technique that uses digital data and mixed-signal or analog processing blocks that generate repetitive signal waveforms. DDS allows very fast frequency switching in very few frequency steps, over a wide band. It is also used to provide linear phase and frequency shift with good spectral purity. DDS is used in particular for high frequency, precise and phase-tunable output. A standard DDS architecture consists of an accumulator, a ROM/lookup table, a DAC, and some reconstruction filters. DDS solutions have been implemented in LSI (Large Scale Integration) and play a major role in digital waveform and clock generation. One of the main advantages of a direct digital synthesizer is that the output frequency, amplitude or phase can be manipulated precisely and quickly under the control of the digital processor. Other important attributes of DDS include tuning capability with extremely precise and fine frequency and phase resolution. Different modulation capabilities can be very easily included in DDS using digital signal processing methods, since the signal is in digital form. If we program DDS, adaptive channel bandwidths, modulation formats, frequency hopping...... middle of paper ...... quantized. Frequency is the rate of phase change, so obviously frequency is also quantized. Due to phase quantization, for a given clock frequency, certain frequencies cannot be achieved exactly. The frequency tuning word (FTW) is calculated using the equation: Fig 1.3 DDS output waveform 1.4 POPULAR USES OF DDS Applications that use DDS based waveform generation are divided into two main categories: Designers of communications systems that require agile (immediately responsive) frequency sources with excellent phase noise and must have low phase noise. parasitic performance, so we often choose DDS for its combination of spectral performance and frequency resolution. Some applications use a DDS for modulation, as a reference for a PLL to improve the overall frequency, as a local oscillator (LO).