Second order type II decision-directed PLL. More...

Inherits unit.

Public Member Functions
function	DDPLL_v1 (in param)
	Class constructor. More...

function	traverse (in obj, in varargin)
	Travese function. More...

function	pll (in obj, in Ein, in Ts, in Kv, in tau1, in tau2, in refConstellation, in initialPhase)
	PLL core processing. More...

function	plot (in obj)
	Plot phase estimates. More...

Public Member Functions inherited from unit
function	traverseNode (in obj)
	Set unique ID when creating a unit. More...

function	connectOutput (in obj, in uobj, in unitOutput, in nextUnitInput)
	Specify where signal should go next. More...

function	connectOutputs (in obj, in units, in destInputs)
	Specify where signal should go next. More...

function	writeInputBuffer (in obj, in sig, in inputId)
	write input buffer

function	horzcat (in varargin)
	horizontal concatenation

function	vertcat (in varargin)
	vertical concatenation

function	setparams (in obj, in params, in REQUIRED_PARAMS, in QUIET_PARAMS)
	set parameters More...

function	view (in obj)
	Show interactive GUI through unit_view-class.

Public Attributes
Property	refConstellation
	Type of constellation (PSK, QAM, ...)

Property	Kv
	Loop constant.

Property	tau1
	PI paramters 1.

Property	tau2
	PI paramters 1.

Property	initialPhase
	Initial phase of the PLL.

Property	speedupEnabled
	Flag to process a single polarization and apply the results to all the others.

Property	Rs

Property	nInputs
	Number of inputs.

Property	nOutputs
	Number of outputs.

Public Attributes inherited from unit
Property	inputBuffer
	Buffer for storing inputs as we traverse the graph.

Property	nextNodes
	Children nodes.

Property	destInputs
	Destination inputs in children.

Property	results
	For storing results.

Property	label

Property	draw
	enable/disable plotting

Property	nInputs
	Number of signals traverse expects.

Property	nOutputs
	Number of outputs traverse expects.

Detailed Description

Second order type II decision-directed PLL.

This class implements a decision-directed PLL for frequency offset correction and carrier phase recovery as described in [1, section 5.8]. The loop filter is proportional-integrator type and based on the implementation discussed in [2, Software PLL chapter].

Tuning the feedback parameters

tau1 and tau2 are as defined in standard continuous time PI-PLL theory - i.e. the loop filter will be described by

F(s) = (1+tau2*s)/(tau1*s)

Kv is a discrete quantity. The analogous continuous time loop gain is given by

Kv_cts = 2*Kv/Ts

Translation from continuous to discrete is accomplished using the bilinear Z transform, which is why tan(Ts/2*tau) appears in the script. Then loop parameters are given by

wn = loop BW in rad/s = sqrt(Kv_cts/tau1)

damping_factor = wn*tau2/2

Example

param.ddpll.constellationType = '16-QAM';

ddpll = DDPLL_v1(param.ddpll);

Advanced example

Rs = 28e9;       %baud rate
param.ddpll.Kv = 0.3;
PI_BW = 100e6;    %Hz
PI_damping = 5;
param.ddpll.tau1 = (2*param.ddpll.Kv*Rs)/((2*pi*PI_BW)^2);
param.ddpll.tau2 = PI_damping*2/(2*pi*PI_BW);
param.ddpll.speedupEnabled = 1;
param.ddpll.constellationType = 'QAM';
ddpll = DDPLL_v1(param.ddpll);

Results:

phaseEstimates - Vectors containing the phases estimated by the DDPLL
frequencyOffsets - Estimation of the frequency offset for each component
linewidths - Estimation of the phase noise linewidth for each component. Highly approximate and will be affected by the SNR.

References:

[1] H. Meyer, Digital Communication Receivers: Synchronization, Channel estimation, and Signal Processing Wiley 1998. Section 5.8 and 5.9.

[2] R. Best, Phase-Locked Loops: Design, Simulation, & Applications, McGraw-Hill 1997. Chapter: Software PLL

Author: Molly Piels (copied from earlier Robochameleon); Simone Gaiarin

See also: constref.m

Definition at line 71 of file DDPLL_v1.m.

Constructor & Destructor Documentation

function DDPLL_v1::DDPLL_v1 ( in param )

Class constructor.

Parameters

param.constellationType	Type of constellation to be used in the decision directed phase detector. Possible values: {'PSK', 'QAM', ...} or using the fast syntax {'QPSK', '16-QAM', ...}. See constref.m for all the possible values.
param.M	Number of symbols in the constellation. Optional if fast syntax is used to define the constellation type.
param.Kv	Loop constant. Can be a scalar or a vector if different values should be used for the different input components (modes). Default: 0.3.
param.tau1	PI filter parameter 1. Default:1/(2piPI_BANDWIDTH) with PI_BANDWIDTH = 10e6
param.tau2	PI filter parameter 2. Default:1/(2piPI_BANDWIDTH) with PI_BANDWIDTH = 10e6
param.initialPhase	Phse used to initialize the DDPLL. Default: 0
param.speedupEnabled	If true the phase is estimated for a single component and used to compensate all the other components. Default: False.

Return values

obj	instance of DDPLL_v1 class

Member Function Documentation

function DDPLL_v1::pll	(	in	obj,
		in	Ein,
		in	Ts,
		in	Kv,
		in	tau1,
		in	tau2,
		in	refConstellation,
		in	initialPhase
	)

PLL core processing.

Estimates the phase error and applies ompensation to the input signal.

Parameters

Ein	input signal

Return values

Eout	signal with phase correction applied Class constructor

Parameters

Ein	Input complex field. [Vector of double].
Ts	Symbol period.
Kv	Loop constant. Can be a scalar or a vector if different values should be used for the different input components (modes). Default: 0.3.
tau1	PI filter parameter 1. Default:1/(2piPI_BANDWIDTH) with PI_BANDWIDTH = 10e6
tau2	PI filter parameter 2. Default:1/(2piPI_BANDWIDTH) with PI_BANDWIDTH = 10e6
refConstellation	Reference constellation points. [Vector of complex double].
param.initialPhase	Phse used to initialize the DDPLL. Default: 0

Return values

E_hat	Input signal with phase corrected.
phaseEstimate	Phase error estimates.

function DDPLL_v1::plot ( in obj )

Plot phase estimates.

Plots phase estimates and delta of the phase estimates as a function of the number of samples

function DDPLL_v1::traverse	(	in	obj,
		in	varargin
	)

virtual

Travese function.

Run the pll on the input signal to estimate the phase and then applies the correction to the input signal.

Saves the phase estimates and the frequency offsets for each components in the results structure.

Parameters

varargin	Case 1: signal_interface with N complex components (modes).
varargin	Case 2: 2 x signal_interface with 1 complex component.
varargin	Case 3: 4 x signal_interface with 4 real components.

Return values

out	signal with phase correction applied

Reimplemented from unit.

The documentation for this class was generated from the following file:

library/rx/DSP/DDPLL_v1.m

Public Member Functions

Public Attributes

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation