Abstract

Frequency synthesizer is an electronic device that is used for creating a number of frequencies in a large band by using a constant signal from an oscillator. They are used in a lot of devices like Satellites, walkie-talkies, cell phones etc. Direct digital frequency synthesizer (DDFS) is a device which is used to generate a large number of frequencies using electronic technique. Its input is a constant digital signal and it generates a discretionary waveform of different frequencies. It is also known as Numerically Control Oscillator. Its detailed parts are ROM, phase accumulator and phase register. It has some analog parts also like digital to analog converter and a low pass filter. When reference clock is given to NCO, it produces a square signal which advances at each progressive clock. The phase register is used to produce various phases using shift keying etc. The main purpose of this paper is to outline, investigate and to reproduce DDFS using environments like Xilinx, Cadence etc. Currently phase locked loops are in wide use but DDFS provides many advantages over PLL like low noise, low cost, fast settling time and high range of frequencies.

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