71
Enrico Rubiola Phase Noise 1. Introduction 2. Spectra 3. Classical variance and Allan variance 4. Properties of phase noise 5. Laboratory practice 6. Calibration 7. Bridge (Interferometric) measurements 8. Advanced methods 9. References 1 www.rubiola.org you can download this presentation, an e-book on the Leeson effect, and some other documents on noise (amplitude and phase) and on precision electronics from my web page Phase Noise Enrico Rubiola Dept. LPMO, FEMTO-ST Institute Besançon, France e-mail rubiola@femto-st.fr or [email protected] Summary

Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

  • Upload
    others

  • View
    5

  • Download
    0

Embed Size (px)

Citation preview

Page 1: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

1. Introduction 2. Spectra3. Classical variance and Allan variance4. Properties of phase noise5. Laboratory practice6. Calibration7. Bridge (Interferometric) measurements8. Advanced methods9. References

1

www.rubiola.orgyou can download this presentation, an e-book on the Leeson effect, and some other documents

on noise (amplitude and phase) and on precision electronics from my web page

Phase Noise Enrico Rubiola

Dept. LPMO, FEMTO­ST Institute – Besançon, France e­mail rubiola@femto­st.fr or [email protected]

Summary

Page 2: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

1 – Introduction

2

Page 3: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

Representations of a sinusoid with noise3 introduction – noisy sinusoid

v(t) = V0 [1 + !(t)] cos ["0t + #(t)]

v(t) = V0 cos !0t + nc(t) cos !0t! ns(t) sin!0t

!(t) =nc(t)V0

and "(t) =ns(t)V0

Chapter 1. Basics 2

v(t)

v(t)V0

V0

phase fluctuation!(t) [rad]

phase time (fluct.)x(t) [seconds]

V0/!

2

phase fluctuation

Phasor RepresentationTime Domain

!(t)

ampl. fluct.

V0/!

2

(V0/!

2)"(t)

t

t

amplitude fluctuationV0 "(t) [volts]

normalized ampl. fluct."(t) [adimensional]

Figure 1.1: .

where V0 is the nominal amplitude, and ! the normalized amplitude fluctuation,which is adimensional. The instantaneous frequency is

"(t) =#0

2$+

1

2$

d%(t)

dt(1.3)

This book deals with the measurement of stable signals of the form (1.2), withmain focus on phase, thus frequency and time. This involves several topics,namely:

1. how to describe instability,

2. basic noise mechanisms,

3. high-sensitivity phase-to-voltage and frequency-to-voltage conversionhardware, for measurements,

4. enhanched-sensitivity counter interfaces, for time-domain measurements,

5. accuracy and calibration,

6. the measurement of tiny and elusive instability phenomena,

7. laboratory practice for comfortable low-noise life.

We are mainly concerned with short-term measurements in the frequency do-main. Little place is let to long-term and time domain. Nevertheless, problemsare quite similar, and the background provided should make long-term and timedomain measurement easy to understand.

Stability can only be described in terms of the statistical properties of %(t)and !(t) (or of related quantities), which are random signals. A problem arises

polar coordinates

Cartesian coordinates

|nc(t)|! V0 and |ns(t)|! V0

under low noise approximation It holds that

Page 4: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

Noise broadens the spectrum4 introduction – noisy sinusoid

v(t) = V0 [1 + !(t)] cos ["0t + #(t)]

v(t) = V0 cos !0t + nc(t) cos !0t! ns(t) sin!0t

! = 2"#

! ="

2#

Page 5: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

Basic problem: how can we measure a low random signal (noise sidebands) close to a strong dazzling carrier?

5 introduction – general problems

s(t) ! hlp(t)

s(t)! r(t" T/4)

convolution(low-pass)

time-domainproduct

vectordifference

distorsiometer,audio-frequency instruments

traditional instruments for phase-noise measurement(saturated mixer)

bridge (interferometric) instruments

Enrico Rubiola – Phase Noise – 6

How can we measure a low random signal (noise sidebands) close to a strong dazzling carrier?

Introduction – general problems

solution(s): suppress the carrier and measure the noise

s(t)! r(t)

Page 6: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

Why a spectrum analyzer does not work?

1. too wide IF bandwidth2. noise and instability of the conversion oscillator (VCO)3. detects both AM and PM noise4. insufficient dynamic range

6 introduction – general problems

Some commercial analyzers provide phase noise measurements, yet limited (at least) by the oscillator stability

Page 7: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

The Schottky-diode double-balanced mixer saturated at both inputs is the most used phase detector

7 introduction – φ –> v converterEnrico Rubiola – Phase Noise – 4

The Schottky-diode double-balanced mixer saturated at both inputs is the most used phase detector

Introduction – ! ! v converter

s(t) =!

2R0P0 cos [2!"0t + #(t)]

r(t) =!

2R0P0 cos [2!"0t + !/2]

signal

reference

r(t)s(t) = k!!(t) + “2"0” termsproductfiltered

out

The AM noise is rejected by saturationSaturation also account for the phase-to-voltage gain kφ

Page 8: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

2 – Spectra

8

Page 9: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

Power spectrum density

statistical expectation

In practice, we measure Sv(f) as

This is possible (Wiener-Khinchin theorem) with ergodic processes

Ergodicity: ensemble and time-domain statistics can be interchanged.This is the formalization of the reproducibility of an experiment

In many real-life cases, processes are ergodic and stationary

Stationarity: the statistics is independent of the origin of time.This is the formalization of the repeatability of an experiment

9 Spectra – definitions

In general, the power spectrum density Sv(f) of a random process v(t) is defined as

Sv(f) = E!F

"Rv(t1, t2)

#$

Fourier transformautocorrelation function

E!

·"

F!·"

Rv(t1, t2)

Sv(f) =!!F

"v(t)

#!!2

Page 10: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

Physical meaning of the power spectrum density10 Spectra – meaning

P =Sv(f0)

R0

Sv(f0)R0

power in 1 Hz bandwidth dissipated by R0

Page 11: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

Physical meaning of the power spectrum density11 Spectra – meaning

The power spectrum density extends the concept of root-mean-square value to the frequency domain

Page 12: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

Sφ(f) and ℒ(f) in the presence of (white) noise12 Spectra – Sφ(f) and ℒ(f)

v0+f

v0 v

N

B

SSBP0

!p

!R0P0

!R0NB

L =N

2P0

v0+f

v0 v

N

B

DSBP0

!p

!R0P0

v0–f

B

!R0NB/2

S! =N

P0dBrad2/HzdBc/Hz 3 dB

!rms =!

12

!p =!

NB

2P0!rms =

!12

!p =!

NB

P0

Page 13: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

ℒ(f) (re)defined

The problem with this definition is that it does not divide AM noise from PM noise, which yields to ambiguous results

13

The IEEE Std 1139-1999 redefines ℒ(f) as

ℒ(f) = (1/2) × Sφ(f)

ℒ(f) = ( SSB power in 1Hz bandwidth ) / ( carrier power )

Spectra – Sφ(f) and ℒ(f)

The first definition of ℒ(f) was

Engineers (manufacturers even more) like ℒ(f)

Page 14: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

y(t) is the fractional frequency fluctuation ν-ν0 normalized to the nominal frequency ν0 (dimensionless)

14 Spectra – useful quantities

Useful quantities

x(t) =1

2!"0#(t)

y(t) =1

2!"0#(t) = x(t)

phase time

fractional frequency fluctuation

x(t) is the phase noise converted into time fluctuationphysical dimension: time (seconds)

y(t) =! ! !0

!0

Page 15: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

Power-law and noise processes in oscillators15 Spectra – power lawEnrico Rubiola – Phase Noise – 15

Noise processes in oscillators

Spectra – power-law

Page 16: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

Relationships between Sφ(f) and Sy(f)16 Spectra – power law

Page 17: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

JitterThe phase fluctuation can be described in terms of a single parameter, either phase jitter or time jitterThe phase noise must be integrated over the bandwidth B of the system (which may be difficult to identify)

The jitter is useful in digital circuits because the bandwidth B is known – lower limit: the inverse propagation time through the system this excludes the low-frequency divergent processes) – upper limit: ~ the inverse switching speed

17 Spectra – jitterEnrico Rubiola – Phase Noise – 17

Jitter

The phase fluctuation can be described in terms of a single parameter, either phase jitter or time jitter

The phase noise must be integrated over the bandwidth B of the system (which may be difficult to identify)

xrms !1

2"#0 $%B S&' f ( df

&rms ! $%B S&' f ( df

The jitter is useful in digital circuits because the bandwidth is known - lower limit: the inverse propagation time through the system

this excludes the low-frequency divergent processes)- upper limit: the inverse witching speed

time jitter phase jitter

converted into time

phase jitter

Victor Reinhardt (invited), A Review of Time Jitter and Digital Systems, Proc. 2005 FCS-PTTI joint meeting

radians

seconds

Page 18: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

Typical phase noise of some devices and oscillators

18 Spectra – examples

Phase Noise Metrology 191

function R!(!). The one-side spectrum is preferred because this is whatspectrum analyzers display. Complying to the usual terminology, we use thesymbol " for the frequency and f for the Fourier frequency, i.e. the frequencyof the detected signal when the sidebands around " are down converted tobaseband.

The power-law model is most frequently used for describing phase noise.It assumes that S!(f) is equal to the sum of terms, each of which varies asan integer power of frequency. Thus each term, that corresponds to a noiseprocess, is completely specified by two parameters, namely the exponent andthe value at f = 1 Hz. Five power-law processes, listed underneath, arecommon with electronics.

noise type S!(f)white phase b0f0

flicker phase b!1f!1

white frequency b!2f!2

flicker frequency b!3f!3

random-walk frequency b!4f!4

All these noise types are generally present at the output of oscillators, whiletwo-port devices show white phase and flicker phase noise only. For reference,Fig. 1 reports the typical phase noise of some oscillators and devices.

-200-200-200

S (f

) (

dB

rad /H

z)!

2

-40

-60

-80

-100

-120

-140

-180

-160

0.1 100 100k10k1 10 1k

Fourier frequency (Hz)

10 GHz Dielectric Resonator Oscillator

10 GHz Sapphire Resonator Oscillator (SRO)

10 GHz SRO with noise degenerationRF amplifier

microwave ferrite isolators

100 MHz quartz oscillator

5 MHz quartz osc.

microwave amplifier

Fig. 1. Typical phase noise of some oscillators and devices

Phase noise can be measured by means of a phase-to-voltage converterin conjunction with a spectrum analyzer, which can be of the low frequency

Page 19: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

3 – Variances

19

Page 20: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

Classical variance

For a given process, the classical variance depends of N

Even worse, if the spectrum is f-1 or steeper,the classical variance diverges

The filter associated to the measure takes in the dc component

20 Variances – classicalEnrico Rubiola – Phase Noise – 20

Classical variance

y !1"0

1#$#

"%t & dt

'2!

1N(1 )

i!1

N

%yi(1N )

j!1

Ny j&

2

normalized reading of a counter that measures (averages) over a time T

classical variance, file of N counter readings

average of the N readings

For a given process, the classical variance depends of N

Even worse, if the spectrum is f-1 or steeper,the classical variance diverges

The filter associated to the measure takes in the dc component

Enrico Rubiola – Phase Noise – 20

Classical variance

y !1"0

1#$#

"%t & dt

'2!

1N(1 )

i!1

N

%yi(1N )

j!1

Ny j&

2

normalized reading of a counter that measures (averages) over a time T

classical variance, file of N counter readings

average of the N readings

For a given process, the classical variance depends of N

Even worse, if the spectrum is f-1 or steeper,the classical variance diverges

The filter associated to the measure takes in the dc component

Page 21: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

Zero dead-time two-sample variance(Allan variance)

Definition(Let N = 2, and average)

Estimated Allan variance, file of m counter readings

The filter associated to the difference of two contiguous measures is a band-pass

The estimate converges to the variance

21 Variances – AllanEnrico Rubiola – Phase Noise – 21

Zero dead-time two-sample variance(Allan variance)

Definition(Let N = 2, and average)

Estimated Allan variance, file of m counter readings

The filter associated to the difference of two contiguous measures is a band-pass(about one octave)

The estimate converges to the variance

! y2"

12 #$y2%y1&

2 '

!y2"

12 $m%1& (i"1

m%1

$ y2%y1&2

Enrico Rubiola – Phase Noise – 21

Zero dead-time two-sample variance(Allan variance)

Definition(Let N = 2, and average)

Estimated Allan variance, file of m counter readings

The filter associated to the difference of two contiguous measures is a band-pass(about one octave)

The estimate converges to the variance

! y2"

12 #$y2%y1&

2 '

!y2"

12 $m%1& (i"1

m%1

$ y2%y1&2

Page 22: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

The Allan variance is related to the spectrum Sy(f)22 Variances – Allan

Page 23: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

Convert Sφ and Sy into Allan variance23 Variances – Allan

noisetype S!(f) Sy(f) S! ! Sy !2

y(") mod!2y(")

whitePM b0 h2f2 h2 =

b0

#20

3fHh2

(2$)2"!2

2$"fH"1

3fH"0h2

(2$)2"!3

flickerPM b!1f!1 h1f h1 =

b!1

#20

[1.038+3 ln(2$fH")]h1

(2$)2"!2 0.084 h1"!2

n"1whiteFM b!2f!2 h0 h0 =

b!2

#20

12h0 "!1 1

4h0 "!1

flickerFM b!3f!3 h!1f

!1 h!1 =b!3

#20

2 ln(2) h!12720

ln(2) h!1

randomwalkFM

b!4f!4 h!2f!2 h!2 =b!4

#20

(2$)2

6h!2" 0.824

(2$)2

6h!2 "

frequency drift y = Dy12

D2y "2 1

2D2

y "2

fH is the high cuto! frequency, needed for the noise power to be finite.

Page 24: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

4 – Propertiesof phase noise

24

Page 25: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

Ideal synthesizer- noise-free- zero delay time

time translation:output jitter = input jitter phase time xo=xi

linearity of the integral and the derivative operators: φo = (n/d)φi => νo = (n/d)vi

spectra

Frequency synthesis25 Properties of phase noise – synthesis

Enrico Rubiola – Phase Noise – 24

Frequency synthesis

Ideal synthesizer- noise-free- zero delay time

time translation:output jitter = input jitter phase time xo=xi

linearity of the integral and the derivative operators:!o = (n/d)!i => "o = (n/d)"i

spectra

S!o " f # $ " nd #

2

S! i " f #

Properties of phase noise – synthesis

Page 26: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

Carrier collapse

random noise =>phase fluctuation

Simple physical meaning, complex mathematics. Easy to understand in the case of sinusoidal phase modulation

26 Properties of phase noise – synthesis

Page 27: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

Filtering <=> Phase Locked Loop (PLL)

The PLL low-passfilters the phase

Output voltage: the PLLis a high-pass filter

The signal “2”tracks “1”

The FFT analyzer (notneeded here) can be usedto measure Sφ(f)

27 Properties of phase noise – PLLEnrico Rubiola – Phase Noise – 26

Filtering <=> Phase Locked Loop (PLL)

S!2" f #

S!1" f #$

%ko k!H c" f #%2

4&2 f 2'%ko k! H c" f #%2

Svo" f #

S!1" f #$

4& f 2 k!2

4&2 f 2'%ko k! Hc" f #%2

The PLL low-passfilters the phase

Output voltage: the PLLis a high-pass filter

ko "rad (s (V #

k! "V (rad #

The signal “2”tracks “1”

The FFT analyzer (notneeded here) can be usedto measure S!(f)tracks “1”

Properties of phase noise – PLL

Enrico Rubiola – Phase Noise – 26

Filtering <=> Phase Locked Loop (PLL)

S!2" f #

S!1" f #$

%ko k!H c" f #%2

4&2 f 2'%ko k! H c" f #%2

Svo" f #

S!1" f #$

4& f 2 k!2

4&2 f 2'%ko k! Hc" f #%2

The PLL low-passfilters the phase

Output voltage: the PLLis a high-pass filter

ko "rad (s (V #

k! "V (rad #

The signal “2”tracks “1”

The FFT analyzer (notneeded here) can be usedto measure S!(f)tracks “1”

Properties of phase noise – PLL

Page 28: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

For slow frequency fluctuations, a delay-line t is equivalent to a resonatorof merit factor

Frequency discriminator

A resonator turns a slow frequency fluctuation Δν into a phase fluctuation

phase φ

ν0 Qresonator

Parametersν0 resonant frequencyQ merit factor

28

ν0

ν

ν

Properties of phase noise – discriminator

Page 29: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

The Leeson effect:phase-to-frequency noise conversion in oscillators

29 Properties of phase noise – Leeson

Enrico Rubiola – The Leeson Effect – 1

The Leeson EffectEnrico Rubiola

Dept. LPMO, FEMTO-ST Institute – Besançon, Francee-mail [email protected] or [email protected]

noise of electronic circuits

oscillator noise

D. B. Leeson, A simple model for feed back oscillator noise, Proc. IEEE 54(2):329 (Feb 1966)

S!" f #

f

Leesoneffect

resonator

out

fL = !0/2Q

S! " f # $ %1&" '0

2Q #2

1f 2 ( S) " f #

oscillatornoise

amplinoise

www.rubiola.orgsome free documents on noise (amplitude and phase) and on

precision electronics will be available in this non-commercial site

D. B. Leeson, A simple model for feed back oscillator noise, Proc. IEEE 54(2):329 (Feb 1966)

E. Rubiola, The Leeson effect, Tutorial 2A, Proc. 2005 FCS-PTTI (tutorials)E. Rubiola, The Leeson effect, e-book, (http://arxiv.org/abs/physics/0502143 or rubiola.org)

Page 30: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

5 – Laboratory practice

30

Page 31: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

Practical limitations of the double-balanced mixer

1 – Power narrow power range: ±5 dB around Pnom = 5-10 dBm r(t) and s(t) should have (about) the same power

2 – Flicker noise due to the mixer internal diodes typical Sφ = –140 dBrad2/Hz at 1 Hz in average-good conditions

3 – Low gain kφ ~ –10 to –14 dBV/rad typical (0.2-0.3 V/rad)

4 – White noise due to the operational amplifier

31 Laboratory practice – background noise

Page 32: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

Typical background noise

RF mixer (5-10) MHzGood operating conditions (10 dBm each input)Low-noise preamplifier (1 nV/√Hz)

32 Laboratory practice – background noise

Page 33: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

The operational amplifier is often misused

Warning: if only one arm of the power supply is disconnected, the LT1028 may delivers a current from the input (I killed a $2k mixer in this way!)

You may duplicate the low-noise amplifier designed at the FEMTO-STRubiola, Lardet-Vieudrin, Rev. Scientific Instruments 75(5) pp. 1323-1326, May 2004

33 Laboratory practice – background noise

Page 34: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

A proper mechanical assembly is vital34 Laboratory practice – background noise

Page 35: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise – 35 Laboratory practice – useful schemesEnrico Rubiola – Phase Noise – 34 Laboratory practice – useful schemes

Two-port device under test (DUT)

Page 36: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise – 36 Laboratory practice – useful schemes

Two-port device under test (DUT)Enrico Rubiola – Phase Noise – 35 Laboratory practice – useful schemes

other configurations are possible

Page 37: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

A frequency discriminator can be used to measure the phase noise of an oscillator

37 Laboratory practice – useful schemes

Page 38: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

Phase Locked Loop (PLL)

Phase: the PLLis a low-pass filter

Output voltage: the PLLis a high-pass filter

compare an oscillator under test to a reference low-noise oscillator– or –

compare two equal oscillators and divide the spectrum by 2 (take away 3 dB)

38 Laboratory practice – oscillator measurement

Enrico Rubiola – Phase Noise – 26

Filtering <=> Phase Locked Loop (PLL)

S!2" f #

S!1" f #$

%ko k!H c" f #%2

4&2 f 2'%ko k! H c" f #%2

Svo" f #

S!1" f #$

4& f 2 k!2

4&2 f 2'%ko k! Hc" f #%2

The PLL low-passfilters the phase

Output voltage: the PLLis a high-pass filter

ko "rad (s (V #

k! "V (rad #

The signal “2”tracks “1”

The FFT analyzer (notneeded here) can be usedto measure S!(f)tracks “1”

Properties of phase noise – PLL

Enrico Rubiola – Phase Noise – 26

Filtering <=> Phase Locked Loop (PLL)

S!2" f #

S!1" f #$

%ko k!H c" f #%2

4&2 f 2'%ko k! H c" f #%2

Svo" f #

S!1" f #$

4& f 2 k!2

4&2 f 2'%ko k! Hc" f #%2

The PLL low-passfilters the phase

Output voltage: the PLLis a high-pass filter

ko "rad (s (V #

k! "V (rad #

The signal “2”tracks “1”

The FFT analyzer (notneeded here) can be usedto measure S!(f)tracks “1”

Properties of phase noise – PLL

Page 39: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise – 39 Laboratory practice – oscillator measurement

Phase Locked Loop (PLL)Enrico Rubiola – Phase Noise – 38 Laboratory practice – oscillator measurement

Page 40: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise – 40 Laboratory practice – oscillator measurement

A tight PLL shows many advantagesEnrico Rubiola – Phase Noise – 39 Laboratory practice – oscillator measurement

but you have to correct the spectrum for the PLL transfer function

Page 41: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

Practical measurement of Sφ(f) with a PLL

1. Set the circuit for proper electrical operationa. power level

b. lock condition (there is no beat note at the mixer out)

c. zero dc error at the mixer output (a small V can be tolerated)

2. Choose the appropriate time constant

3. Measure the oscillator noise

4. At end, measure the background noise

41 Laboratory practice – oscillator measurement

Page 42: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise – 42 Laboratory practice – oscillator measurement

Enrico Rubiola – Phase Noise – 41 Laboratory practice – oscillator measurement Warning: a PLL may not be what it seems

Page 43: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

PLL – two frequencies

At low Fourier frequencies, the synthesizer noise is lower thanthe oscillator noise

At higher Fourier frequencies, the white and flicker of phase of the synthesizer may dominate

The output frequency of the two oscillators is not the same. A synthesizer (or two synth.) is necessary to match the frequencies

43 Laboratory practice – oscillator measurement

Page 44: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

PLL – low noise microwave oscillators

Due to the lower carrier frequency, the noise of a VHF synthesizer is lower than the noise of a microwave synthesizer.

With low-noise microwave oscillators (like whispering gallery) the noise of a microwave synthesizer at the oscillator output can not be tolerated.

This scheme is useful• with narrow tuning-range oscillator, which can not work at the same freq.• to prevent injection locking due to microwave leakage

44 Laboratory practice – oscillator measurement

Page 45: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

Designing your own instrument is simpleStandard commercial parts:• double balanced mixer• low-noise op-amp• standard low-noise dc components in the feedback path• commercial FFT analyzer

Afterwards, you will appreciate more the commercial instruments:– assembly– instruction manual– computer interface and software

45 Laboratory practice – oscillator measurement

Page 46: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

6 – Calibration

46

Page 47: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

Calibration – general procedure1 – adjust for proper operation: driving power and quadrature

2 – measure the mixer gain kφ (volts/rad) —> next

3 – measure the residual noise of the instrument

47 Calibration – general

Page 48: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

Calibration – general procedure4 – measure the rejection of the oscillator noise

Make sure that the power and the quadrature are the same during all the calibration process

48 Calibration – general

Page 49: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

Calibration – measurement of kφ (phase mod.)

The reference signal can be a tone: detect with the FFT, with a dual-channel FFT, or with a lock-in (pseudo-)random white noise

tone:

white noise

Some FFTs have a white noise outputDual-channel FFTs calculate the transfer function |H(f)|2=SVm/SVd

49 Calibration – measurement of kφ

Vm

Page 50: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

Calibration – measurement of kφ (rf signal)50 Calibration – measurement of kφ

Page 51: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

Calibration – measurement of kφ (rf noise)A reference rf noise is injected in the DUT path

through a directional coupler

51 Calibration – measurement of kφ

Page 52: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

7 – Bridge (interferometric) measurements

52

Page 53: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise – 53 Bridge – Wheatstone

Wheatstone bridgeEnrico Rubiola – Phase Noise – 52 Interferometer – Wheatstone bridge

Page 54: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

Wheatstone bridge – ac version

equilibrium: Vd = 0 –> carrier suppression

static error δZ1 –> some residual carrier real δZ1 => in-phase residual carrier Vre cos(ω0t) imaginary δZ1 => quadrature residual carrier Vim sin(ω0t)

fluctuating error δZ1 => noise sidebands real δZ1 => AM noise nc(t) cos(ω0t) imaginary δZ1 => PM noise –ns(t) sin(ω0t)

54 Bridge – Wheatstone

Page 55: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise – 55 Bridge – Wheatstone

Wheatstone bridge – ac versionEnrico Rubiola – Phase Noise – 54 Interferometer – Wheatstone bridge

Page 56: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise – 56 Bridge – schemeEnrico Rubiola – Phase Noise – 55 Interferometer – scheme

Bridge (interferometric) phase-noise and amplitude-noise measurement

Page 57: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise – 57 Bridge – synchronous detection

Synchronous detectionEnrico Rubiola – Phase Noise – 56 Interferometer – synchronous detection

Page 58: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

Synchronous in-phase and quadrature detection58 Bridge – synchronous detection

Enrico Rubiola – Phase Noise – 57

Synchronous in-phase and quadrature detection

Interferometer – synchronous detection

Page 59: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise – 59 Bridge – background noise

White noise floorEnrico Rubiola – Phase Noise – 58 Interferometer – noise floor

Page 60: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

White noise floor – example

60 Bridge – background noiseEnrico Rubiola – Phase Noise – 59 Interferometer – noise floor

White noise floor – example

Page 61: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

What really matters (1)61 Bridge – summary

Page 62: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

What really matters (2)62 Bridge – summary

Page 63: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

A bridge (interferometric) instrument can be built around a commercial instrument

You will appreciate the computer interface and the software ready for use

63 Bridge – commercial

Page 64: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

8 – Advanced Techniques

64

Page 65: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise – 65 Advanced – flicker reduction

Low-flicker schemeEnrico Rubiola – Phase Noise – 64 Advanced – flicker reduction

Page 66: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise – 66 Advanced – flicker reduction

Interpolation is necessaryEnrico Rubiola – Phase Noise – 65 Advanced – flicker reduction

Page 67: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

Correlation can be used to reject the mixer noise

67 Advanced – correlation

Page 68: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

Correlation – how it works

68 Advanced – correlation

Page 69: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

Flicker reduction, correlation, and closed-loop carrier suppression can be combined

E. Rubiola, V. Giordano, Rev. Scientific Instruments 73(6) pp.2445-2457, June 2002

69 Advanced – matrix

dualintegr matrix

D

R0=

50Ω

matrixB

matrixGv2

w1

w2

matrixB

matrixG

w1

w2

FFTanalyz.

atten

atten

x t( )

Q

II−Q

modul

’ γ’atten

Q

II−Q

detectRF

LO

Q

II−Q

detectRF

LOg ~ 40dB

g ~ 40dB

v1

v2

v1

u1

u2 z2

z1

atten

DUT

γΔ’

0R

0R

10−20dBcoupl.

pow

er sp

litte

r

pump

channel a

channel b (optional)

rf virtual gndnull Re & Im

RF

suppression controlmanual carr. suppr.

pump LO

diagonaliz.

readout

readout

arbitrary phase

var. att. & phase

automatic carrier

arbitrary phase pump

I−Q detector/modulator

G: Gram Schmidt orthonormalizationB: frame rotation

inner interferometerCP1 CP2

CP3

CP4

−90° 0°

I

QRF

LO

Page 70: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise – 70 Advanced – comparison

1 10 32 4 5

−180

10 10 10

−140

−170

−160interferometer

correl. saturated mixer

Fourier frequency, Hz−220

−210

saturated mixer

correl. sat. mix.

double interf.

interferometer

residual flicker, by−step interferometer

residual flicker, fixed interferometer

residual flicker, fixed interferometer

residual flicker, fixed interferometer, ±45° detection

S (f) dBrad2/Hzϕ real−time

correl. & avg.

nested interferometer

mixer, interferometer

saturated mixer

double interferometer

−200

−190

10

−150

measured floor, m=32k

Comparison of the background noise

Page 71: Enrico Rubiola – Phase Noise – Phase Noiserubiola.org/pdf-slides/2005T-ifcs-basics.pdf · 2. noise and instability of the conversion oscillator (VCO) 3. detects both AM and PM

Enrico Rubiola – Phase Noise –

9 – ReferencesSTANDARDSJ. R. Vig, IEEE Standard Definitions of Physical Quantities for Fundamental Frequency and Time Metrology--Random Instabilities, IEEE Standard 1139-1999 ARTICLESJ. Rutman, Characterization of Phase and Frequency Instabilities in Precision Frequency Sources: Fifteen Years of Progress, Proc. IEEE vol.66 no.9 pp.1048-1075, Sept. 1978. RecommandedE. Rubiola, V. Giordano, Advanced Interferometric Phase and Amplitude Noise Measurements, Rev. of Scientific Instruments vol.73 no.6 pp.2445-2457, June 2002. Interferometers, low-flicker methods, correlation, coordinate transformation, calibration strategies, advanced experimental techniquesBOOKSChronos, Frequency Measurement and Control, Chapman and Hall, London 1994. Good and simple reference, although datedW. P. Robins, Phase Noise in Signal Sources, Peter Peregrinus,1984. Specific on phase noise, but dated. Unusual notation, sometimes difficult to read.Oran E. Brigham, The Fast Fourier Transform and its Applications, Prentice-Hall 1988. A must on the subject, most PM noise measurements make use of the FFTW. D. Davenport, Jr., W. L."Root, An Introduction to Random Signals and Noise, McGraw Hill 1958. Reprinted by the IEEE Press, 1987. One of the best references on electrical noise in general and on its mathematical properties.E. Rubiola, The Leeson effect (e-book, 117 pages, 50 figures) arxiv.org, document arXiv:physics/0502143E. Rubiola, Phase Noise Metrology, book in preparation

ACKNOWLEDGEMENTSI wish to express my gratitude to the colleagues of the FEMTO-ST (formerly LPMO), Besancon, France, firsts of which Vincent Giordano and Jacques Groslambert for a long lasting collaboration that helped me to develop these ideas and to put them in the present form.

71