PhaseNoise+Jitter

PhaseNoise+Jitter - Phase Noise and Timing Jitter Phase...

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1 Phase Noise and Timing Jitter Phase noise and timing jitter Phase noise Measure of spectral density of clock frequency Units: dBc/Hz (decibels below the carrier per Hz) Analog people care about this Timing Jitter Measurement of variations in clock transition edges with respect to reference Units: Seconds (usually pS), or UI (unit interval) More intuitive, useful in digital systems
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2 Example: Communication Systems Signal of Interest Interference Local Oscillator ϖ ϖ ϖ RF ϖ IF ϖ RF - ϖ IF ϖ RF + ∆ϖ ϖ Received Signal IF Filter
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3 Phase-Noise in Communication Systems Signal of Interest Interference Local Oscillator ϖ ϖ ϖ RF ϖ IF ϖ RF + ϖ IF ϖ RF + ∆ϖ ϖ Received Signal Phase Noise Degraded SNR IF Filter
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4 Clock Jitter in high-speed Communication Systems Signal Ideal clock 1101001 Noisy clock 1100011 Degraded BER
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5 Noise in Oscillators ( 29 φ t A V o o + = ω cos ideal , ( 29 ( 29 ( 29 π ω 2 period    with    function    periodic practical , = + = t φ t f t A V o o AM PM FM v n φ AM o ω m o ω ω + m o ω ω - PM m o ω ω - m o ω ω + o ω Total noise power equally split into phase noise power and amplitude noise power
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6 o L nd nR P o L d o v dt di L i i R v i i dt t dv C P = + + - - = ; ) ( nd nR L P L d L i i dt di R L i i dt i d LC P + + - - - = 2 2 P m L P L m o m d R g dt di R L dt di L g v g i 1 when ; ) ( = - = - = - =
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7 ( 29 ( 29 ( 29 2 2 2 2 2 0 2 0 0 2 2 2 2 2 2 2 2 2 2 4 1 ) ( ; 1 ; When 1 1 1 nd nR on nd nR on nd nR L i i C v LC i i LC L v i i LC i P P P + = << = + = + - = + - = ϖ ϖ ϖ ϖ ϖ ϖ ϖ ϖ ϖ ϖ ϖ )) ( ) ( ( 1 1 ) ( 2 2 2 s I s I LCs s I i i i dt i d LC nd nR L nd nR L L P P + + = + + - =
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8 ( 29 ) ( ) ( 1 4 1 ) ( 2 2 2 0 2 2 2 2 2 2 2 2 2 2 2 ϖ ϖ ϖ ϖ ϖ ϖ ϖ ϖ = = + = + = F Q kTR F C R kT i i C R kT i i C v P P nR nd P nd nR on P P ϖ 1/f
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9 Phase Noise Spectrum { } ( 29 ϖ + ϖ = ϖ carrier sideband total P Hz P 1 , log 10 0 L ϖ 0 ϖ Hz 1 dBc Freq Power Frequency Phase Noise 0  (white phase) –2  (random walk phase or white FM) (flicker FM) –4  (random walk FM)
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10 Phase Noise in Oscillators Device noise leads to frequency fluctuations. Example: Ring Oscillators Phase noise characterizes the frequency fluctuations. Phase noise characterizes the frequency fluctuations. Output t f f o I t Time Domain Phase Noise Frequency Domain 0 2 4 -2
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11 Phase Noise: Formulation and Measurement Phase noise definition: PSD of signal divided by power Hard to formulate Easy to measure PN (dBc/Hz) f o f f o + f Phase noise measurement This method is most suitable for formulation of phase noise in switching- This method is most suitable for formulation of phase noise in switching- base oscillators. base oscillators. Need accurate formulation for specific oscillators.
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