Lect22_Phase Noise II

Lect22_Phase Noise II - ECE 620 Introduction to RF...

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ECE 620 Introduction to RF Integrated Circuits Prof. Waleed Khalil Lecture Phase Noise II 22 1
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Outline Phase Noise Calculation Impact of Phase Noise 2
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S v (f) 3 PSD of the voltage fluctuations in Watts/Hz Measured directly using spectrum analyzer Passband measurement Both AM and PM noise are measured in S v (f o ±f) Need to suppress AM noise (limiter) to measure PN: Bc/Hz d P ) f f ( S log 10 ) f ( signal 0 v ± = L
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S Φ (f) 4 PSD of the RMS value of phase fluctuations Φ(t) in radians 2 /Hz S Φ (f) measured by passing the signal through a mixer/PD Convert phase fluctuations to voltage signal Baseband measurement S Φ (f) is the sum of power at both positive and negative offset frequency f from the carrier: Often confused with S v (f o ±f) [ ] 2 2 () 0 / RMS f S f f rad Hz df ϕ = < <∞
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Narrowband FM: L(f) vs. S Φ (f) 5 Modeling PN as PM signal : Φ pk : is the peak phase deviation (in radians) For small phase deviations; Φ pk << 1 ( ) ) t f 2 sin( t f 2 cos V ) t ( V m pk c o π φ + = ( ) ( ) ( ) ( )
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Lect22_Phase Noise II - ECE 620 Introduction to RF...

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