In this work we analyzed the simulated results of DDS and the different PLLs used for frequency synthesis using tools Xilinx and Matlab. NCO is a digital computing block which renders digital word sequences in time at a given reference clock frequency fclk, which thereafter are converted into analog signals to serve as a synthesizer. The analog part has Digital-to-Analog Converter and a filter. DDFS's digital part is also known as Numerically Controlled Oscillator, which consists of a Phase Register, a Phase Accumulator and a ROM.
Second frequency technique, the Direct Digital Frequency Synthesis (DDFS) is a kind of frequency synthesizer that uses electronic methods for digitally creating arbitrary waveforms and frequencies from a single, fixed source frequency. Though we gave a comparative results of PLLs used in our simulation based on their settling time. We used DDS and two types of PLLs analog as well as digital in our work. In particular, it is possible to achieve a very high-frequency resolution together with fast settling and spectral purity.
The phase locked loop (PLL) has been widely used in wireless communication systems due to the high frequency resolution and the short locking time.
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