104 lines
3.4 KiB
Matlab
104 lines
3.4 KiB
Matlab
classdef Photodiode
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%PGOTODIODE Summary of this class goes here
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% Detailed explanation goes here
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properties
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fsimu
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responsivity
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dark_current
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temperature
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nep
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randomkey
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randomstream
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end
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methods
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function obj = Photodiode(options)
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%PHOTODIODE Construct an instance of this class
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% Detailed explanation goes here
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arguments
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options.fsimu
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options.responsivity = 1;
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options.dark_current = 0;
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options.temperature = 20;
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options.nep = 0; %(Moveit IMDD Standard: 1.8e-11 == current noise density in A/sqrt(Hz)! ); usually between 10-20 pA/sqrt(Hz); see J.Leibrich Diss/ S. Pachnicke Slides
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options.randomkey = 1;
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end
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fn = fieldnames(options);
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for l = 1:numel(fn)
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obj.(fn{l}) = options.(fn{l});
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end
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obj.randomstream = RandStream('mlfg6331_64','Seed',obj.randomkey);
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end
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function signalclass_out = process(obj,signalclass_in)
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% actual processing of the signal (steps 1. - 3.)
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signalclass_in.signal = obj.process_(signalclass_in.signal);
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% cast the inform. signal to electrical signal
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[signalclass_in, nase, lambda] = Electricalsignal(signalclass_in,"fs",obj.fsimu,"logbook",signalclass_in.logbook);
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% append to logbook
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lbdesc = ['Photo Diode '];
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signalclass_in = signalclass_in.logbookentry(lbdesc);
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% write to output
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signalclass_out = signalclass_in;
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end
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function yout = process_(obj,xin)
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%METHOD1 Summary of this method goes here
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% Detailed explanation goes here
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k = Constant.Boltzmann;
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q = Constant.ElementaryCharge;
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T = obj.temperature + 273.15 ; %celsius + 273 = kelvin
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R = 50; %resistance of phdiode (50ohm is typical value)
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% Magnitude squared detection (sum over pols)
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yout = sum( abs(xin) .^2 * obj.responsivity, 2 ) ;
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% Shot Noise
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shot_noise = sqrt(q * obj.fsimu .* yout) .* randn(obj.randomstream,size(yout,1),1);
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yout = yout + shot_noise;
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% Thermal Noise
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% 2026 comment: obj.nep is not the correct naming, but math-wise everything is fine!
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% (2 * k * T / R ) -> A^2/Hz -> is the psd of thermal noise
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% earlier: move it's 1.8e-11 is current noise density -> A/sqrt(Hz)
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% power (of white process) is simple multiplication of PSD(f) and B
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% NEP is noise equivalent power, see Dissertation j. Leibrich
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% P. 121 or Stephan Pachnicke Optical Comm. Lecture Slides
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if obj.nep == 0 %
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nep_squared = (2 * k * T / R ) ; %squared
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else
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nep_squared = obj.nep^2;
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end
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Bw = obj.fsimu;
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therm_noise_pow = nep_squared * Bw; %squared
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therm_noise = sqrt(therm_noise_pow) .* randn(obj.randomstream,size(yout,1),1);
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yout = yout + therm_noise;
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% Dark Current
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yout = yout + obj.dark_current ;
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end
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end
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end
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