Transcript PLL Implementation with Simlink and Matlab Project 2 ECE283

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
Simulink main screen
– Or click simulink icon
Graphic User Interface
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Simulink built-in library
Make a new model window
Expand library
Drag and drop
Connect blocks
Simulate
Visualize
Tuning
Make a model
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Amplitude modulation
New model
Open library
Drag blocks
Connect
Source and sink
Example:AmModEx.mdl
Simulation
• Tune
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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
Ports and subsystem library
Triggered subsystem
• Example:AmModEx.mdl
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
Latched and unlatched trigger example – Matters with discrete-time signals
– Almost same with continuous-time
signals except for feedback
• Example:TriggerEx1.mdl
• Subsystem examples
Integration
• Initiailization
– Matched filter
– Correlator
• External triggering
• Example:IntegratorE
x.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
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Initialization
Calculate outputs
Update discrete states
Calculate derivatives
Integration
– Calculate outputs
– Calculate derivatives
• MATLAB example code
sfuntmpl.m is in
matlabroot/toolbox/si
mulink/blocks
S-function operation diagram
Example Code
• 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
function [sys,x0,str,ts] =
VCO(t,x,u,flag,FreqCntr)
%VCO
switch 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 flags
End
S-function Initialization
function [sys,x0,str,ts]=VCOInit
sizes = simsizes;
sizes.NumContStates = ;
sizes.NumDiscStates = ;
sizes.NumOutputs
= ;
sizes.NumInputs
= ;
sizes.DirFeedthrough = ;
sizes.NumSampleTimes = ;
% at least one sample time is
needed
sys = simsizes(sizes);
x0 = [];
% initialize the initial conditions
str = [];
% str is always an empty matrix
ts = [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 Output
function [sys,x0,str,ts] =
VCO(t,x,u,flag,FreqCntr,Phase
,Gain)
switch flag,
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case 3,% Outputs
……………
sys=VCOOutput(t,x,u,FreqCntr,
Phase,Gain);
End
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function
sys=VCOOutput(t,x,u,FreqCntr,
Phase,Gain)
sys =
Gain*cos(2*pi*(FreqCntr+u)*t+
Phase);
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T: time
X: state
U: input
Flag: computation mode
Static parameters
S-function Instantiation
S-function instance
S-function block parameters
• 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
Discussions on PLL
Decision-directed PLL diagram
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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 noise