Fundamentals of RF Design RF Back to Basics 2015

Transcription

1 Fundamentals of RF Design 2015 Updated January 1, 2015 Keysight EEsof EDA Objectives Review Simulation Types Understand fundamentals on S-Parameter Simulation Additional Linear and Non-Linear Simulators 2015 Page 2 1

2 Electronic Design Automation (EDA) IDEA CONCEPT DESIGN PRODUCT 2015 Page 3 We Are Focusing On The Idea to Concept / Design Simulations Only Consider Effects in the Model Reality Considers Everything 2015 Page 4 2

3 RF Calculations S 11 = Reflected Incident S 2 1 = b 1 a 1 a 2 =0 = Transmitted = b 2 Incident a 1 a 2 =0 S 2 2 = Reflected Incident S 1 2 = b 2 a 2 a 1 =0 = Transmitted = b 1 Incident a 2 a 1 = Page 5 Cascading S-Parameters a1 S a2 a1 S a2 b1 b2 b1 b2 For Cascaded S Matrix a1 =b2 and a2=b Page 6 3

4 Cascading S-Parameters b1=s11*a1+s12*a2=s11a1+s12*b1 where b1 =S11 *a1 +S12 *a2 substituting yields, b1=s11*a1+s12*s11 *a1 +S12*S12 *a2 eq 1 a1 =b2=s21*a1+s22*a2 where a2=b1 substituting and rearranging yields, a1 =(S21**a1+S22*S12 *a2 )/1-S22*S11 eq 2 then eq 2 into eq 1, Repeating for b2 results in cascaded S-Parameterw 2015 Page 7 Advanced Design System Lineage Touchstone 2015 Page 8 4

5 Touchstone Netlist 2015 Page 9 Simulation Types DC, AC, Linear (S-Parameter) Transient (High Frequency Spice) Harmonic Balance Circuit Envelope EM Simulation MoM, FEM, FDTD 2015 Page 10 5

6 S-Parameter Simulation 2015 Page 11 S-Parameter Termination Termination can be any impedance value Port Count is not limited No Calibration needed 2015 Page 12 6

7 S-Parameter Simulation (Frequency-domain) DC analysis is performed to find the bias point Nonlinear devices linearized at the bias point Assumes signal does not perturb the bias S-parameter sources are ports Components characterized by I and their small-signal [S] or [Y] Finds solution such that sum of all AC currents into each circuit node is zero (not iterative) Computes [S] and [Y] of the overall circuit at external ports Calculates response to small sinusoidal signals 2015 Page 13 S-Parameter Simulation 2015 Page 14 7

8 Instead of Take a Measurement We Run a Simulation 2015 Page 15 ADS Netlist 2015 Page 16 8

9 S-Parameter Controller Options/Sweep Plans 2015 Page 17 S-Parameter Controller Options/Sweep Plans 2015 Page 18 9

10 Tune 2015 Page 19 Transmission Lines 2015 Page 20 10

11 Ideal Transmission Line 2015 Page 21 Microstrip Transmission Lines Surface Roughness Option Frequency Dependent Dielectric Model 2015 Page 22 11

12 Multilayer Transmission Lines 2015 Page 23 Integration of EM Solvers Method of Moments Finite Elements Method 2015 Page 24 12

13 Power Transfer Efficiency RS RL For complex impedances, maximum power transfer occurs when Z L = Z S * (conjugate match) Load Power (normalized) RL / RS Maximum power is transferred when R L = R S 2015 Page 25 Power Transfer Efficiency 2015 Page 26 13

14 AC Analysis (Frequency-domain simulator) DC Analysis is performed to find the bias point Nonlinear devices linearized at the bias point Assumes signal does not perturb the bias Sources are voltage and current sine waves Superposition is allowed and encouraged Outputs are voltage and current Sums all AC currents into each circuit node (not iterative) 2015 Page 27 Power Transfer Efficiency 2015 Page 28 14

15 Power Transfer Efficiency 2015 Page 29 Power Transfer Efficiency 2015 Page 30 15

16 Smith Chart Review +jx Polar plane 90 o R o o 0 -jx Rectilinear impedance plane Smith Chart maps rectilinear impedance plane onto polar plane Z = 0 L Γ Z L= Zo Γ = 0 = 1 ±180 O Inductive -90 o (short) Z L = Constant X Γ Constant R = 1 0 O (open) Capacitive Smith Chart 2015 Page 31 Series Capacitance 2015 Page 32 16

17 Series Inductance 2015 Page 33 Series Resonance 2015 Page 34 17

18 Separating Resonant Elements 2015 Page 35 Example of Matching Elements 2015 Page 36 18

19 Example of Matching Elements 2015 Page 37 Smith Chart Characteristics 2015 Page 38 19

20 Modeling Linear Behavior In ADS S-Parameters 2015 Page 39 Using Optimization to Develop Models 2015 Page 40 20

21 AmodelB Optimization Setup 2015 Page 41 S-Parameters Before and After Optimization Before Optimization After Optimization 2015 Page 42 21

22 SP_Probe 2015 Page 43 Starting LineCalc 2015 Page 44 22

23 LineCalc Tool 2015 Page 45 Transient Analysis Just like SPICE Kirchoff s current equations are derived at each node in differential form v(t) The time derivatives are replaced with discrete-time approximations (integration) The solution, in the case of a complex circuit, will consist of a system of nonlinear equations which is solved using the Newton- Raphson method 2015 Page 46 23

24 Convolution Analysis Convolution calculates the response of distributed and dispersive network, to an arbitrary transient time-domain waveform. Models can includes conductor loss, dielectric loss, self-and coupled inductance and capacitance, as functions of frequency, and multi-port s-parameter data sets from measurements and field solvers. Impulse response for all distributed components is calculated, then convolved with input signal to yield output Results can be transformed to the frequency domain Page 47 Transient Simulation with Convolution 2015 Page 48 24

25 Harmonic Balance (Steady State Analysis) Start Simulation Frequencies Number of Harmonics Number of Mixing Products DC analysis always done Linear Components Measure Linear Circuit Currents in the Frequency-Domain Nonlinear Components Measure Nonlinear Circuit Voltages in the Frequency-Domain Inverse Fourier Transform: Nonlinear Voltage Now in the Time Domain Calculate Nonlinear Currents Fourier Transform: Nonlinear Currents Now back in the Frequency Domain Test: Error > Tolerance: if yes, modify & recalculate if no, then Stop= correct answer Page 49 Example Circuit: First and Last Iterations IR IC IL ID IY-port (Momentum file) Start in the Frequency Domain Calculate currents Convert: ts -> fs Initial Estimate: spectral voltage IR IC IL ID IY If within tolerance Last Estimate with least error IR IC IL ID I Y the n V Final Solution 2015 Page 50 25

26 Harmonic Balance Setup 2015 Page 51 Harmonic Balance Results 2015 Page 52 26

27 Modulated Sources 2015 Page 53 Circuit Envelope Time samples the modulation envelope (not carrier) Compute the spectrum at each time sample Output a time-varying spectrum Use equations on the data Faster than HB or Spice in many cases Integrates with System Simulations & Keysight s Ptolemy Next, what tests can it perform? 2015 Page 54 27

28 Test Circuits with Realistic Signals GSM, CDMA, GMSK, pi/4dqpsk, QPSK, etc. Simulations can include: Example CE results: 32.8 khz BW for NADC Adjacent Channel Power Ratio Noise Power Ratio Error Vector Magnitude Power Added Efficiency Bit Error Rate 2-tone tests and linearized models do not predict this behavior as easily! Also, Envelope can be used for PLL simulations: lock time, spurious signals, modulation in the loop. 890 MHz carrier 2015 Page 55 Circuit Envelope Technology Circuit V(t) * e t 3 Modulation t 2 t 4 t 1 j2π fot Vout Carrier Time sample the envelope and then perform Harmonic Balance on the samples! More... Periodic input signal NOTE: V(t) can be complex - am or fm or pm 2015 Page 56 28

29 More on CE Technology Captures time and frequency characteristics: Next, an example... dbm (fs (Vout[1])) 2015 Page 57 IS-95 Forward Link Modulated Signal Generation 2015 Page 58 29

30 IS-95 Forward Link Modulated Signal Generation 2015 Page 59 What are X-Parameters? X-parameters are the mathematically correct superset of S- parameters, applicable to both large-signal and small-signal conditions, for linear and nonlinear components. The math exists! We can measure, model, & simulate with X-parameters Each part of the puzzle has been created The pieces now fit together seamlessly NVNA: Measure X-parameters PHD: X-parameter block ADS: Simulate X-parameters Interoperable Nonlinear Measurement, Modeling & Simulation with X-parameters X-parameters have the potential to do for characterization, modeling, and design of nonlinear components and systems what linear S-parameters do for linear components & systems 2015 Page 60 30

31 X-parameters From Poly-Harmonic Distortion (PHD) 2015 Page 61 Experiment Setup and Simulation Schematic Objective: Design nonlinear circuits in ADS from NVNA-measured X-parameters of individual components 2015 Page 62 31

32 Cascaded Simulation vs. Measurement Red: Cascade Measurement Blue: Simulation of Cascaded Models X-parameters enable predictive nonlinear design from NL data 2015 Page 63 Thank you! For More Information ADS on Evaluate ADS Page 64 32