Our final year project is DDS, first proposed by J.Tierney in 1971. Direct digital synthesis (DDS) is a method used to create waveforms and frequencies arbitrary digital signals from a single frequency source. Since VLSI technology is also developing the needs 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 numerically controlled oscillator (NCO), which is a technique that uses digital data and mixed-signal or analog processing blocks that generate repetitive signal waveforms. DDS achieves very fast frequency switching in just a few frequency steps, over a wide bandwidth. It is also used to provide linear phase shift and frequency shift with good spectral purity. DDS is primarily used for high-frequency, precise, 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 an important role in generating digital and clock waveforms. One of the main advantages of a direct digital synthesizer is that the output frequency, amplitude or phase can be precisely and quickly manipulated under the control of the digital processor. Other important attributes of the DDS include the ability to tune with extremely precise and precise frequency and phase resolution. Different modulation capabilities can be included very easily in the DDS using digital signal processing methods, since the signal is in digital form. If we program the DDS, adaptive channel bandwidths, modulation formats, frequency hopping... half the paper... quantized. Frequency is the rate of change of phase, so obviously frequency is also quantized. Due to phase quantization, for a given clock frequency, there are some frequencies that cannot be reached exactly. The frequency tuning word (FTW) is calculated using the equation:Fig 1.3 DDS Output Waveform 1.4 POPULAR USES OF DDS Applications using DDS-based waveform generation are divided into two main categories: Communication system designers who require agile (immediately responding) frequency sources with excellent phase noise and should have low spurious performance, therefore we often choose DDS for its combination of spectral performance and frequency resolution. Some of the applications include using a DDS for modulation, as a reference for a PLL to improve the overall frequency, as a local oscillator (LO).