An integer- frequency synthesiser locks a voltage-controlled oscillator at to a…

PHYSICS · Multi-part · Fermi University Physics · Electronics, Instrumentation & Communication · Feedback, operational amplifiers and analogue signal processing · Feedback, operational amplifiers and analogue signal processing

Inside the Instrument, Ch Filters, crystal oscillators and phase-locked loops

Problem

An integer-

N

frequency synthesiser locks a voltage-controlled oscillator at

900\,\mathrm{MHz}

to a

25\,\mathrm{MHz}

reference crystal through a divide-by-

N

counter in the feedback path. ((a)) Find the divider ratio

N

. ((b)) State the channel spacing this synthesiser can step in. ((c)) Find the in-band phase-noise penalty, in decibels, that the output carries relative to the reference's phase noise.

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