This paper presents a design and simulation of proposed frequency synthesizer which
can be used for WiMAX. Design parameters for the proposed fractional-N PLL
synthesizer for WiMAX system are either selected from WiMAX standards or
according to results of analysis for each unit of the proposed system. Different
techniques for phase noise reduction are discussed. Sigma-delta fractional-N
technique is chosen for WiMAX system, since low settling time, spurious level and
phase noise can be obtained by using this technique. The simulation result shows the
system is stable, since the phase margin is greater than 45 degree. The settling time,
spurious level and phase noise obtained with this synthesizer are 5.9μs, -90dBc/Hz,
and -100dBc/Hz respectively. CppSim program (C++ simulator language) and Matlab
(V.7) are used for simulation of ΣΔ fractional-N PLL synthesizer.