BANDWIDTH OPTIMIZATION TO ACHIEVE MINIMUM PHASE NOISE IN FREQUENCY SYNTHESIZERS

This paper analyzes the phase noise of the single loop second-order frequencyfractional-N synthesizer. The aim of this paper is the reduction of the output phase noise in theapplication of commercial and military subsystems as well as general local oscillators. Themathematical model of PLL based frequency synthesizer is analyzed to develop the minimumphase noise in the specific frequency range. An exact closed form relationship between bandwidthand output phase noise of the frequency synthesizer as well as the bandwidth-phase noise diagramis extracted by using this closed form relationship. From the analysis and simulation results, weobserve that the system has minimum phase noise at a particular closed-loop bandwidth. Tovalidate simulation results, the synthesizer is implemented on the low loss professional printedcircuit board (PCB). Measurement setup is scheduled on spectrum analyzer 8562A in the span of5MHz and 10MHz. These measurements show excellent results in output spectrum of thefrequency synthesizer.