PLL Implementation with Simlink and Matlab

Project 2

ECE283

Fall 2004

Simulink in MATLAB

• Graphic user interface• Continuous, discrete, and

mixed mode• Integration with MATLAB• Fast prototyping• User-defined functions• How to run it

– >>simulink– Or click simulink icon Simulink main screen

Graphic User Interface

• Make a new model window• Expand library• Drag and drop• Connect blocks• Simulate• Visualize• Tuning

Simulink built-in library

Make a model

• New model• Open library• Drag blocks• Connect• Source and sink• Example:AmModEx.mdl

Amplitude modulation

Simulation

• Tune– Simulation time

– Relative tolerance

– Refine factor

– Etc

• Simulate• Example:AmModEx.mdl

Simulation parameters

Visualization

• Double click scope• Options on signal source

and sink– External files

– Workspace variables

• Example:AmModEx.mdl

Simulation output scope

Subsystem

• Subsystem for modular programming

• How to make it– Subsystem library

– Subsystem conversion

• Example:AmModEx.mdlPorts and subsystem library

Triggered subsystem

Getting Help

• Need help?– MATLAB and Simulink

help

– Mathworks user community

– Mathwork technical support

Simulink help screen

PLL Implementation

• Sampler • Voltage controlled clock• Voltage controlled

oscillator• Feedback loop

Decision-directed phase-locked loop

Sampler• Options

– Triggered subsystem

– User-defined function

– Others

• Latched and unlatched– Matters with discrete-time signals

– Almost same with continuous-time signals except for feedback

• Example:TriggerEx1.mdl• Subsystem examples

Latched and unlatched trigger example

Integration

• Initiailization– Matched filter

– Correlator

• External triggering• Example:IntegratorEx.mdl

Integration block parameters

S-function

• User-defined function written in MATLAB, etc.

• One input and one output– scalar, vector, matrix, etc.

• Static parameters• R14 provides more options

for user-defined function

User-defined functions library

S-function Operation• Initialization

• Calculate outputs

• Update discrete states

• Calculate derivatives

• Integration– Calculate outputs

– Calculate derivatives

• MATLAB example code sfuntmpl.m is in matlabroot/toolbox/simulink/blocks

S-function operation diagram

Example Codefunction [sys,x0,str,ts] =

VCO(t,x,u,flag,FreqCntr)%VCOswitch flag, case 0,% Initialization [sys,x0,str,ts]=VCOInit; case 1,% Derivatives sys=VCODeriv(t,x,u); case 2,% Update sys=VCOUpdate(t,x,u); case 3,% Outputs sys=VCOOutput(t,x,u,FreqCntr); case 4,% GetTimeOfNextVarHit sys=VCPNextHit(t,x,u); case 9,% Terminate sys=VCOExit(t,x,u); otherwise % Unexpected flagsEnd

• Flag 0: Initialization• Flag 1: Calculation of

derivatives • Flag 2: Update of discrete

states• Flag 3: Calculation of

output• Flag 4: Calculation of next

sample hit• Flag 9: End of simulation

tasks

S-function Initializationfunction [sys,x0,str,ts]=VCOInitsizes = simsizes;sizes.NumContStates = ;sizes.NumDiscStates = ;sizes.NumOutputs = ;sizes.NumInputs = ;sizes.DirFeedthrough = ;sizes.NumSampleTimes = ; % at least one sample time is

neededsys = simsizes(sizes);x0 = [];% initialize the initial conditionsstr = [];% str is always an empty matrixts = [0 0];% initialize the array of sample

times

• Define necessary – Internal states (continuous

and discrete-time)

– Number of inputs

– Number of outputs

– Initial conditions

S-function Outputfunction [sys,x0,str,ts] =

VCO(t,x,u,flag,FreqCntr,Phase,Gain)

switch flag,……………

case 3,% Outputs……………

sys=VCOOutput(t,x,u,FreqCntr,Phase,Gain);

End

……………function

sys=VCOOutput(t,x,u,FreqCntr,Phase,Gain)

sys = Gain*cos(2*pi*(FreqCntr+u)*t+Phase);

• T: time• X: state• U: input• Flag: computation mode• Static parameters

S-function Instantiation

• Drag and drop S-function system block to a model

• Double click the block to specify the script name and static parameters

• Example: VCOSfuncEx.mdl

S-function instance

S-function block parameters

Discussions on PLL• Modulation frequency

• Number of waves per symbol

• Low-pass filter

• Simulation length

• Symbol feedback delay

• Evaluation

• Timing error

• Capture range

• Loop lock range

• Effect of symbol error

• Effect of signal noiseDecision-directed PLL diagram