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classdef (StrictDefaults) LoopFilter < serdes.SerdesAbstractSystemObject & TriggeredComponent
% LoopFilter Loop Filter
% obj = LoopFilter returns a System Object, obj, that integrates the
% input Up/Down signal and increments or decrements the output phase
% control signal.
%
% LoopFilter methods:
% step - Integrates the input Up/Down phase detector signal and
% increments or decrements the output phase control signal when the
% sum exceeds some limit. The useage is:
% PhaseControl = step(obj,ClockIn,UpDown)
%
% LoopFilter properties:
% ProportionalGain - Proportional gain. Typically set to 1/timeInterleaveDepth
% PhaseStep - Step size for phase increment or decrement
% UpDownMaxLimit - Up/down counter limit
% Copyright 2021 The MathWorks, Inc.
%#codegen
properties (Nontunable)
% Proportional gain
% Typically set to 1/timeInterleaveDepth
ProportionalGain = 1.0;
% Step size for phase increment/decrement
PhaseStep = 1/128;
% Up/down counter limit
UpDownMaxLimit = 16;
end
properties (Hidden, SetAccess=private)
PhaseControlInternal % Phase control output
UpDownSum % Accumulated up/down pulses (sum)
UpDownLimit % Current limit of up/down sum
PhaseChange % Phase increment/decrement
end
properties(Hidden,Nontunable)
%Required by abstract class but not used
NumberOfClocks = 1;
end
properties (SetAccess = immutable, Nontunable, Hidden)
IsLinear = true;
IsTimeInvariant = true;
end
properties (Nontunable,Hidden)
%Input Waveform Type
% Set the input wave type as one of 'Sample' | 'Impulse' |
% 'Waveform'. The default is 'Sample'.
WaveType = 'Sample';
end
properties(Hidden, Constant)
WaveTypeSet = matlab.system.StringSet({'Sample','Impulse','Waveform'});
end
methods
% Constructor
function obj = LoopFilter(varargin)
% Support name-value pair arguments when constructing object
obj.BlockName = 'LoopFilter';
setProperties(obj,nargin,varargin{:})
end
end
methods (Hidden)
% The below methods, getAMIParameters, getAMIInputNames and
% getAMIOutputNames are for use only within the serdesDesigner App
% and will not influence the AMI parameters in Simulink whatsoever.
function amiParameters = getAMIParameters(~)
amiParameters = {};
end
function names = getAMIInputNames(~)
names = {};
end
function names = getAMIOutputNames(~)
names = {};
end
end
methods (Access = protected, Hidden)
function val = isSample(obj)
val = strcmpi(obj.WaveType,'Sample');
end
end
methods(Access = protected)
%% Common functions
function setupImpl(obj)
setupClock(obj);
% Initialize phase error output
obj.PhaseControlInternal = 0.0;
% Initialize filter properties
obj.UpDownSum = 0.0;
obj.UpDownLimit = 0.0;
obj.PhaseChange = 0.0;
end
function validateInputsImpl(~,waveIn)
validateattributes(waveIn,{'numeric'},{'finite'},'','waveIn');
end
function PhaseControl = stepImpl(obj,ClockIn,UpDown)
%PhaseControl = stepImpl(obj,ClockIn,UpDown)
if isSample(obj)
%Triggered clock step
ClockStep(obj,ClockIn)
% On falling clock edge, filter the incoming phase error
if obj.PhaseFallingIndex > 0
% Reset phase increment/decrement
obj.PhaseChange = 0.0;
% Update up/down accumulator
obj.UpDownSum = obj.UpDownSum + UpDown;
% Up/down sum exceed current limit (positive or negative side)
if abs(obj.UpDownSum) >= obj.UpDownLimit
% Set phase increment/decrement
obj.PhaseChange = sign(obj.UpDownSum) * obj.PhaseStep;
% Reset up/down accumulator
obj.UpDownSum = 0;
% Ramp up up/down limit at start up
if obj.UpDownLimit >= obj.UpDownMaxLimit
obj.UpDownLimit = obj.UpDownMaxLimit;
else
obj.UpDownLimit = obj.UpDownLimit + 1;
end
end
% Update phase control
obj.PhaseControlInternal = obj.PhaseControlInternal + obj.ProportionalGain * obj.PhaseChange;
end % obj.PhaseFallingIndex > 0
end
% Assign output
PhaseControl = obj.PhaseControlInternal;
end
function resetImpl(~)
% Initialize / reset discrete-state properties
end
%% Simulink functions
function icon = getIconImpl(~)
% Define icon for System block
icon = "Loop\nFilter";
end
function [name1,name2] = getInputNamesImpl(~)
name1 = sprintf('Demux\nClock');
name2 = 'UpDown';
end
function name1 = getOutputNamesImpl(~)
name1 = sprintf('Phase\nControl');
end
end
methods(Static, Access=protected)
function group = getPropertyGroupsImpl(~)
% Define property section(s) for System block dialog
group = matlab.system.display.SectionGroup(...
'Title','Main',...
'PropertyList',{'ProportionalGain','PhaseStep',...
'UpDownMaxLimit'});
end
end
end
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