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start implementation of class based simulation of a IM/DD communication system. Mostly based on Move-It but cleaned up and with focus on direct detection, however I try to keep the versatility of move-it alive.
This commit is contained in:
Silas Oettinghaus
258
Classes/AWG.m
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258
Classes/AWG.m
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classdef AWG
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%AWG Summary of this class goes here
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% Detailed explanation goes here
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properties(Access=public)
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kover %oversampling factor e.g. 16
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repetitions %repeat the signal to generate a longer sequence?
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fdac %needed
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normalize %want to normalize at first? either 0 or 1
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bit_resolution %bit res. of quantizer (e.g. 5 bit)
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dac_min
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dac_max
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skew_active = 0;
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awg_skew ; %skew vector for each output channel
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lpf_active = 0;
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lpf_type ;
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f_cutoff ;
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lowpass ;
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signal_length;
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H_lpf;
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end
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methods (Access=public)
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function obj = AWG(options)
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%AWG Construct an instance of this class
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% Detailed explanation goes here
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arguments
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options.preset = [];
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options.kover = 16;
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options.repetitions = 1;
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options.normalize = 1;
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options.fdac = 92e9;
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options.bit_resolution = 5.5
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options.dac_min = -0.5;
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options.dac_max = 0.5;
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options.skew_active = 0;
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options.awg_skew = 0;
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options.lpf_active = 0;
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options.lpf_type = 0;
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options.f_cutoff = 32e9;
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options.lowpass = 1;
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end
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if isempty(options.preset)
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obj.skew_active = 0;
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obj.lpf_active = 0;
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elseif options.preset == "M8196A"
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% M8196A (92GBd) https://www.keysight.com/us/en/product/M8196A/92-gsa-s-arbitrary-waveform-generators.html
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obj.dac_max = 0.5;
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obj.dac_min = -.5;
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obj.lowpass = 1; %LP
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obj.f_cutoff = 32e9;
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elseif options.preset == "M8199B"
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%https://www.keysight.com/us/en/assets/3120-1465/data-sheets/M8199A-128-256-GSa-s-Arbitrary-Waveform-Generator.pdf
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end
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obj.kover = options.kover; %oversampling factor e.g. 16
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obj.repetitions = options.repetitions; %repeat the signal to generate a longer sequence?
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obj.fdac = options.fdac;
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obj.normalize = options.normalize;%want to normalize at first? either 0 or 1
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obj.bit_resolution = options.bit_resolution;%bit res. of quantizer (e.g. 5 bit)
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obj.dac_min = options.dac_min;
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obj.dac_max = options.dac_max;
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obj.lpf_active = options.lpf_active;
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obj.skew_active = options.skew_active;
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obj.awg_skew = options.awg_skew;
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end
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function data_out = process_channel(obj,data_in)
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%METHOD1 Summary of this method goes here
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% Detailed explanation goes here
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obj.signal_length = length(data_in);
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if obj.normalize
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% 5.1. Normalize the signal to 1 Vpp and set the amplitude of the signal
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data_in = data_in/(max(data_in)-min(data_in));
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else
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% 5.1. Cut the Signal at -1 and 1 and scale to amplitude
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data_in(data_in > 1) = 1;
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data_in(data_in < -1) = -1;
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end
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% 1. Quantize the signal
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if obj.bit_resolution>0
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data_out = obj.quantization(data_in) ;
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else
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data_out = data_in;
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end
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% 2. Sample and hold + repeat (data_out: 1xsignal length)
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data_out = repmat(data_out,obj.repetitions,obj.kover);
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data_out = reshape(data_out',[],1);
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% 3. Add skew
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if obj.skew_active
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data_out = obj.skew(data_out);
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end
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% 4. Apply LPF on the signal
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if obj.lpf_active
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obj.H_lpf = obj.buildFilter(1);
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data_out = obj.lpf(data_out) ;
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end
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end
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end
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methods (Access=private)
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function quant_out = quantization(obj,x_in)
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steps = round(2^obj.bit_resolution) + rem(round(2^obj.bit_resolution),2) ;
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if isreal(x_in)
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% shift signal and clip to quantizer intervall
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x_in = min(max(x_in-obj.dac_min,0),obj.dac_max-obj.dac_min);
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% quantize signal
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x_in = round((steps-1)/(obj.dac_max-obj.dac_min)*x_in);
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% scale and shift back
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quant_out = x_in*(obj.dac_max-obj.dac_min)/(steps-1) +obj.dac_min;
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else
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% shift signal and clip to quantizer intervall
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x_in = min(max(real(x_in)-obj.dac_min,0),obj.dac_max-obj.dac_min) + ...
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1i*min(max(imag(x_in)-obj.dac_min,0),obj.dac_max-obj.dac_min);
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% quantize signal and shift back signal
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x_in = round((steps-1)/(obj.max-obj.dac_min)*x_in);
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% scale and shift back
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quant_out = x_in*(obj.dac_max-obj.dac_min)/(steps-1) +(1+1i)*obj.dac_min;
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end
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end
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function skew_out = skew(obj,x_in)
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% Exact delay calculation
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% Calculate transfer function
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fsimu = obj.kover*obj.fdac;
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faxis = linspace(fsimu/2, fsimu/2, length(x_in)+1);
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faxis = fftshift(faxis(1:end-1));
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skew_out = ifft(fft(x_in) .* exp(-1i*2*pi*obj.awg_skew*faxis)' );
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skew_out = real(skew_out) ; % get rid of negligible imaginary part
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end
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function lpf_out = lpf(obj,x_in)
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lpf_out = ifft(obj.H_lpf.*fft(x_in));
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end
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function H = buildFilter(obj,filterType)
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filtdegree = 3;
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fsimu = obj.kover*obj.fdac;
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rp = 0.5; %passband ripple
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rs = 0.5; %stopband ripple
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switch filterType
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case 1
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% Bessel filter, impulse invariant transformed
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[B, A] = besself(filtdegree, 2*pi*obj.f_cutoff);
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[B ,A] = impinvar(B,A,fsimu);
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case 2
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% Bessel filter, impulse bilinear transformed
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[Z, P, K] = besself(filtdegree, 2*pi*obj.f_cutoff);
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[Z ,P, K] = bilinear(Z,P,K,fsimu);
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[B ,A] = zp2tf(Z ,P ,K);
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case 3
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% Butterworth filter
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if obj.lowpass == 1 %lowpass
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[B, A] = butter(filtdegree, obj.f_cutoff/(fsimu/2),'low');
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else % highpass
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[B, A] = butter(filtdegree, obj.f_cutoff/(fsimu/2),'high');
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end
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case 4
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% Chebyshev 1 filter
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[B, A] = cheby1(filtdegree,rp, obj.f_cutoff/(fsimu/2));
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case 5
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% Chebyshev 2 filter
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[B, A] = cheby2(filtdegree,rs, obj.f_cutoff/(fsimu/2));
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case 6
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% Elliptic filter
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[B, A] = ellip(filtdegree,rp,rs,obj.f_cutoff/(fsimu/2));
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case 7
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% Hamming filter
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g=(filtdegree-1)/2;
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wc=obj.f_cutoff/(fsimu/2);
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B = wc*sinc(wc*(-g:g)).*hamming(filtdegree)';
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A=1;
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case 8
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% Raised Cosine filter
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B = firrcos(filtdegree,obj.f_cutoff,para.df,fsimu);
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A=1;
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case 9
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% Sinc filter
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g=(filtdegree-1)/2;
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wc=obj.f_cutoff/(fsimu/2);
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B = wc*sinc(wc*(-g:g));
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A=1;
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end
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H = freqz(B, A, obj.repetitions*obj.kover*obj.signal_length,'whole');
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end
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end
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end
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