Filter Design for A Fractional N-PLL Frequency Synthesizer At 2.4 GHz

Abstract

Abstract Radio frequency transmitter and receivers usually needs an efficient frequency synthesizer, and this synthesizer must use a digital electronic circuit to perform different modern digital application which contain a frequency synthesizer circuit as a main part of the circuits. The fractional-N phase locked loop (PLL) has been used widely in the last twenty year ago because it gives a large bandwidth with fine frequency resolution for various electronic applications. This research presents the design of second order low pass filter at a frequency bandwidth of (50,75,125,250,500) kHz and for each value of the phase margin (30,35,40,47,57,65,70,80) degree, the component values of the filters which the capacitors and resistance were found at each values of the frequency bandwidth and for each phase margin, also the filter impedance, open loop and closed loop gain was calculated, it is found that by proper design of the second order low pass filter component, the system can have more stability operation and the spurs noise in the output can be reduced efficiently.