uestc射频模拟电路与系统RFIC_fall2012_lect8_phase_noise_2p

Dr. K. Kang 2 Oscillator output spectrumDr. K. Kang 3Phase noise versus amplitude noiseDr. K. Kang 4Graphical picture of AM and PMDr. K. Kang 5Phase noise?Dr. K. Kang 6Phase noise measurementDr. K. Kang 7Phase noise in TX chainDr. K. Kang 8Phase noise in RX chainDr. K. Kang 9Phase noise in digital communication Dr. K. Kang10§▪ “Perfectly efficient” RLC oscillator§▪ Signal energy stored in the tank§▪ Mean square signal (carrier) voltage isDr. K. Kang 11General RLC oscillator§▪ Total mean-square noise voltage §▪ Noise to Signal ratio§▪ Resonator Q§▪ ThereforeDr. K. Kang 12General RLC oscillator (con’t)N/S =V↓n ↓↑2 /​V↓sig ↓↑2 =kT/​E↓stored §▪ The only source is the white thermal noise of the tank conductance§▪ For a relatively small offset frequency Δω from the center frequency ω0 , the impedance of an LC tank may be approximated by§▪ Unloaded tank QDr. K. Kang 13 Phase noise of an ideal oscillator §▪ Solving for L and substituting into previous equ. Yields §▪ The spectral density of the mean-square noise voltage §▪ In our idealized LC model, thermal noise affects both amplitude and phase, and the above equation. includes their combined effect. The equipartition theorem of thermodynamics tells us that, in equilibrium, amplitude and phase-noise power are equal. Therefore, the amplitude limiting mechanism present in any practical oscillator removes half the noise given by the above equation.Dr. K. Kang 14 Phase noise of an ideal oscillator (con’t)§▪ Normalize the mean-square noise voltage density to the mean-square carrier voltage§▪ Increasing the resonator Q and signal amplitude can reduce phase noise§▪ The unit is dBc/Hz, “decibels below the carrier per hertz”, specified at a particular offset frequency Δω from thecarrier frequency ω§▪ It is important to note that the “per Hz” actually applies to the argument of the log, not to the log itself: doubling the measurement bandwidth does not double the decibelquantity. Dr. K. Kang 15Phase noise of an ideal oscillator (con’t)§▪ A modification was made by D. B. LeesonDr. K. Kang 16Leeson Model§▪ F is an empirical fitting parameter and must be determined via measurements§▪ Δω1/f3 is also a fitting parameter§▪ The frequency at which the noise flattens out is notalways equal to half the resonator bandwidth, ω/2QDr. K. Kang 17Lesson Model (con’t)Dr. K. Kang18Dr. K. Kang 19LTV Phase noise model§▪ Nonlinearity is clearly a fundamental property of all real oscillators, as it is necessary for amplitude limiting§▪ a single-frequency sinusoidal disturbance injected into an oscillator gives rise to two equal-amplitude sidebands, symmetricallydisposed about the carrier.§▪ However, the amplitude of the sidebands does not depend nonlinearly on the amplitude of the injected signal. Therefore,nonlinear mixing can not explain it.§▪ An important insight is that disturbances are just that: perturbations superimposed on the main oscillation§▪ Linearity would therefore appear to be a reasonable assumption as far as the noise-to-phase transfer function is concerned.§▪ when assessing linearity, it is essential to identify explicitly the input–output variables. Linear relationships may exist betweencertain variable pairs at the same time nonlinear ones existbetween others.Dr. K. Kang 20LinearityDr. K. Kang 21Time variance: Injection at peak amplitudeDr. K. Kang 22Time variance: Injection at zero-crossing§▪ Limit cycle§▪ Phase and amplitude impulse response modelDr. K. Kang 23Impulse response modelDr. K. Kang 24ISF modelDr. K. Kang 25Example waveformsDr. K. Kang 26General responseDr. K. Kang 27Phase deviation to outputDr. K. Kang 28Noise sidebandDr. K. Kang 29Graphical interpretationDr. K. Kang 30White noise expressionDr. K. Kang 31Final expressionDr. K. Kang 32Cyclostationary noiseDr. K. Kang 331/f noise upconversionDr. K. Kang 34Amplitude noiseDr. K. Kang 35Amplitude responseDr. K. Kang 36JitterDr. K. Kang 37Jitter computationDr. K. Kang 38Jitter relation to phase noise§▪ Michael Perrot, “High speed communication circuits”, lecture notes, MIT§▪ Behzad Razavi, “RF microelectronics” Prentice Hall, 1998 §▪ Thomas H. Lee, “The design of CMOS radio-frequency integrated circuits” Second Edition, CambridgeUniversity Press, 2004§▪ Ali M Niknejad, “EECS 242”, lecture notes, Berkeley§▪ Lawrence E. Larson, “Introduction to Active Circuits”, lecture notes, UCSD§▪ John R Long, “Wireless IC Building Blocks in CMOS/ BiCMOS”, ISSCC 2005 short course§▪ S. Simon Wong, “Technology Options for RFIC”, ISSCC 2005 short course§▪ P. E. Allen, “CMOS Analog Circuit Design”, 2006 Dr. K. Kang 39ReferenceDr. K. Kang 40Reference。