PLL Implementation with Simlink and Matlab

1
PLL Implementation with Simlink and Matlab

• Project 2
• ECE283
• Fall 2004

2
Simulink in MATLAB

• Graphic user interface
• Continuous, discrete, and mixed mode
• Integration with MATLAB
• Fast prototyping
• User-defined functions
• How to run it
• gtgtsimulink
• Or click simulink icon

Simulink main screen
3
Graphic User Interface

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

Simulink built-in library
4
Make a model

• New model
• Open library
• Drag blocks
• Connect
• Source and sink
• ExampleAmModEx.mdl

Amplitude modulation
5
Simulation

• Tune
• Simulation time
• Relative tolerance
• Refine factor
• Etc
• Simulate
• ExampleAmModEx.mdl

Simulation parameters
6
Visualization

• Double click scope
• Options on signal source and sink
• External files
• Workspace variables
• ExampleAmModEx.mdl

Simulation output scope
7
Subsystem

• Subsystem for modular programming
• How to make it
• Subsystem library
• Subsystem conversion
• ExampleAmModEx.mdl

Ports and subsystem library
Triggered subsystem
8
Getting Help

• Need help?
• MATLAB and Simulink help
• Mathworks user community
• Mathwork technical support

Simulink help screen
9
PLL Implementation

• Sampler
• Voltage controlled clock
• Voltage controlled oscillator
• Feedback loop

Decision-directed phase-locked loop
10
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
• ExampleTriggerEx1.mdl
• Subsystem examples

Latched and unlatched trigger example
11
Integration

• Initiailization
• Matched filter
• Correlator
• External triggering
• ExampleIntegratorEx.mdl

Integration block parameters
12
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
13
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
14
Example Code

• function sys,x0,str,ts VCO(t,x,u,flag,FreqCntr
  )
• VCO
• switch flag,
• case 0, Initialization
• sys,x0,str,tsVCOInit
• case 1, Derivatives
• sysVCODeriv(t,x,u)
• case 2, Update
• sysVCOUpdate(t,x,u)
• case 3, Outputs
• sysVCOOutput(t,x,u,FreqCntr)
• case 4, GetTimeOfNextVarHit
• sysVCPNextHit(t,x,u)
• case 9, Terminate
• sysVCOExit(t,x,u)
• otherwise Unexpected flags
• End

• 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

15
S-function Initialization

• function sys,x0,str,tsVCOInit
• 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

16
S-function Output

• function sys,x0,str,ts VCO(t,x,u,flag,FreqCntr
  ,Phase,Gain)
• switch flag,
• case 3, Outputs
• sysVCOOutput(t,x,u,FreqCntr,Phase,Gain)
• End
• function sysVCOOutput(t,x,u,FreqCntr,Phase,Gain)
• sys Gaincos(2pi(FreqCntru)tPhase)

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

17
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
18
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 noise

Decision-directed PLL diagram