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Quartz Crystal Oscillators and Phase-Locked Loops

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Dominik Schneuwly of Oscilloquartz and Greg Armstrong of IDT delivered an ITSF 2016 tutorial on phase locked loops and oscillators.

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Quartz Crystal Oscillators and Phase-Locked Loops

  1. 1. Tutorial: Quartz Crystal Oscillators and Phase- Locked Loops Dominik Schneuwly (Oscilloquartz) Greg Armstrong (IDT) October 14th, 2016
  2. 2. © 2015 ADVA Optical Networking. All rights reserved.2 Content 1. Quartz Crystal Oscillator (XO) Technology • Quartz Crystal Overview • Ageing and Temperature • XO, TCXO, OCXO, DOCXO 2. Phase Locked Loops (PLL) • PLL Overview • Response To Injected Noise 3. PLL with 2 inputs
  3. 3. © 2015 ADVA Optical Networking. All rights reserved.3 1. Quartz Crystal Oscillator (XO) Technology
  4. 4. © 2015 ADVA Optical Networking. All rights reserved.4 Quartz = SiO2 Pink = silicon atoms Blue = oxygen atoms Quartz Crystal Piezo-Electric Effect: Mechanical strain  voltage Inverse Piezo-Electric Effect: Voltage  mechanical deformation = Oxigen atom = Silicon atom Oxygen atom
  5. 5. © 2015 ADVA Optical Networking. All rights reserved.5 Vibration Modes, Resonance Frequency, High Q, Cutting Orientation Fundamental Mode Thickness Shear Third Overtone Thickness Shear Thickness Shear Mode Face Shear Mode Extensional ModeFlexure Mode
  6. 6. © 2015 ADVA Optical Networking. All rights reserved.6 Frequency Drift Due to Ageing Time [day] Fractionalfrequencydeviation[1] 41 3 3E-10 2E-10 1E-10 - 1E-10 - 2E-10 - 3E-10 2 50 0 Positive Ageing Negative Ageing Ageing Reversal Frequency vs. Temperature SC-cut: Θ = 34° Φ = 22° Δf/f as a Function of Temperature (Parameter: ΔΘ = Deviation From Reference Angle) Lower Turnover Point (LTP) Inflection Point (IP) Upper Turnover Point (UTP)
  7. 7. © 2015 ADVA Optical Networking. All rights reserved.7 XO Categories rel. Temp. Control • XO, Crystal Oscillator: • LTP centered in the operation temperature range • > 1E-7 / °C • TCXO, Temperature Compensated XO: • Resonance frequency is modified by a varactor diode so as to compensate for temperature sensitivity • 5E-8 to 5E-7 over [-55°C to 85°C] UCONTROL Temp. Control Temp. Sensor
  8. 8. © 2015 ADVA Optical Networking. All rights reserved.8 XO Categories rel. Temp. Control • OCXO, Oven Controlled XO: • A control loop maintains the oven containing the XO at (nearly) constant temperature. • 5E-9 to 5E-8 over [-30°C to 60°C] • DOCXO, Double Oven Controlled XO: • Two temperature controlled ovens, one inside the other. • 5E-11 to 5E-9 over [-30°C to 60°C] XO Temp. Sensor Temp. Control Heating Oven XO Temp. Sensor Temp. Control Heating Temp. Sensor Heating Temp. Control Outer Oven Inner Oven
  9. 9. © 2015 ADVA Optical Networking. All rights reserved.9 Summary Oscillator Type Temperature Sensitivity (Fractional Frequency vs. Temperature) XO 1E-7 / °C TCXO 5E-8 to 5E-7 [-55°C to 85°C] SOCXO 5E-9 to 5E-8 [-30°C to 60°C] DOCXO 5E-11 to 5E-9 [-30°C to 60°C
  10. 10. © 2015 ADVA Optical Networking. All rights reserved.10 2. Phase-Locked Loops (PLL)
  11. 11. © 2015 ADVA Optical Networking. All rights reserved.11 PLL: Working Principle Phase Comparator Loop Filter Voltage Controlled Oscillator ( )INu t ( )OUTu t             0, 0, ( ) sin 2 sin 2 ( ) sin 2 sin 2 IN NOM IN OUT NOM IN OOU IN OT UT TU u t A t A u t A t A t t t x x t                          P P NOM IN OUT u K x x        ( ) C P u t u t g t   0 OUT C V u K    
  12. 12. © 2015 ADVA Optical Networking. All rights reserved.12 Phase-Time Deviation x(t) Note: Phase-time x = random component only Time Error TE = random and deterministic components t1 t1 + x(t1)      nominal signal actual signal sin 2 sin 2 NO NOM M t x t t         x(t1) t
  13. 13. © 2015 ADVA Optical Networking. All rights reserved.13 Transfer Function «Input-to-Output»  20log 2 [dB]INH j f                    where impulse response transfer function Laplace OUT IN IN OUT IN IN IN IN IN x t x t h t X s X s H s h t H s h t       
  14. 14. © 2015 ADVA Optical Networking. All rights reserved.14 Transfer Function «Oscillator-to-Output»  20log 2 [dB]OSCH j f                    where impulse response transfer function Laplace OUT OSC OSC OUT OSC OSC OSC OSC OSC x t x t h t X s X s H s h t H s h t       
  15. 15. © 2015 ADVA Optical Networking. All rights reserved.15 Both Transfer Functions    20 20 lo log 2 [dB] g 2 [dB] IN OSC H j H j f f  
  16. 16. © 2015 ADVA Optical Networking. All rights reserved.16 PLL: Jitter Filtering 0 100 200 t [s] xIN(t) [s] xOUT(t) [s] 1 x 10 - 6 5 x 10 - 7 - 5 x 10 - 7 - 1 x 10 - 6
  17. 17. © 2015 ADVA Optical Networking. All rights reserved.17 PLL With Direct Digital Synthesis Sine Look-up Table Counts from 0 to 2 N -1 in steps of M DAC & LPF Free-running Oscillator Phase Comparator Loop Filter Replaces the VCO! M νOSC νOUT   where output of the digital loop filter (integer) size of the counter in bits (integer) frequency of output signal free-run frequency of the oscilla OUT OUT OSC M N u t      tor 2 OUT OSCN M  DAC = Digital-to-Analog Converter LPF = Low-pass Filter
  18. 18. © 2015 ADVA Optical Networking. All rights reserved.18 PLL With Digitally Controlled Oscillator PFD – Phase & Frequency Detector TDC – Time-to-Digital Converter PFD & TDC Digital Loop Filter Digitally Controlled Oscillator (DCO) Divider ref(t) out(t) Free- running Oscillator 18
  19. 19. © 2015 ADVA Optical Networking. All rights reserved.19 PLL With VCO, DDS, and DCO Compared Pros Cons PLL with VCO •Very low phase noise •PLL’s pull-in range depends on VCO’s pulling range •Requires VCO PLL with DDS •Configurable pull-in range •Requires only free-running oscillator •Some quantization phase noise PLL with DCO •Fully programmable •Configurable pull-in range •Configurable low pass filter range •Requires only free-running oscillator •Requires APLL to clean up jitter •Precision of TDC affects close-in phase noise 19
  20. 20. © 2015 ADVA Optical Networking. All rights reserved.20 3. PLL with 2 Inputs
  21. 21. © 2015 ADVA Optical Networking. All rights reserved.21 Imagine the Following: Sine Look-up Table Counts from 0 to 2 N -1 in steps of M DAC & LPF Phase Comparator Loop Filter M Input 1 Sine Look-up Table Counts from 0 to 2 N -1 in steps of M DAC & LPF Free-running oscillator Phase Comparator Loop Filter M Input 2 Output
  22. 22. © 2015 ADVA Optical Networking. All rights reserved.22 Imagine the Following: │H2 (f)│ │HOSC (f)│ f [Hz] (log-log scales) │HINT (f)││H1 (f)│ f [Hz] IN 1 OUT INT IN 2 INT OSC
  23. 23. © 2015 ADVA Optical Networking. All rights reserved.23 What Do the Transfer Functions Look Like? f [Hz] log - log scales │H1 (f)│ │H2 (f)│ │HOSC (f)│ OUTIN 1 IN 2 OSC (Application: T-BC with support from SyncE physical layer according to G.8273.2)
  24. 24. © 2015 ADVA Optical Networking. All rights reserved.24 Imagine Three Spectral Densities (Phase-Time): OSC IN 1 IN 2 OUT (log-log scales) │SIN1 (f)│ f [Hz] │SIN2 (f)│ │SOSC (f)│
  25. 25. © 2015 ADVA Optical Networking. All rights reserved.25 … Combined by the 2 Input PLL: (log-log scales) f [Hz] │SOUT (f)│ OSC IN 1 IN 2 OUT
  26. 26. © 2015 ADVA Optical Networking. All rights reserved.26 Physical Layer Support for T-BC and T-TSC G.8273.2 calls for Telecom boundary clock (T-BC) and Telecom time slave clock (T-TSC) to use the physical layer (SyncE) in combination with PTP. G.8273.2
  27. 27. © 2015 ADVA Optical Networking. All rights reserved.27 SyncE PTP Filtering in Combination Transfer for SyncE Noise to Output: OutDCOPTP PLL 2 Osc PTP stack SyncE ToD Counter Loop Filter
  28. 28. IMPORTANT NOTICE The content of this presentation is strictly confidential. ADVA Optical Networking is the exclusive owner or licensee of the content, material, and information in this presentation. Any reproduction, publication or reprint, in whole or in part, is strictly prohibited. The information in this presentation may not be accurate, complete or up to date, and is provided without warranties or representations of any kind, either express or implied. ADVA Optical Networking shall not be responsible for and disclaims any liability for any loss or damages, including without limitation, direct, indirect, incidental, consequential and special damages, alleged to have been caused by or in connection with using and/or relying on the information contained in this presentation. Copyright © for the entire content of this presentation: ADVA Optical Networking. Thank You

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