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Classes/Signal.m

@@ -24,6 +24,7 @@ classdef Signal
 
         end
 
+        %% CONVERT TO INFORMATIONSIGNAL
         function [i_sig, varargout] = Informationsignal(obj)
 
             if isa(obj,'Electricalsignal')
@@ -40,6 +41,7 @@ classdef Signal
 
         end
 
+        %% CONVERT TO Electricalsignal
         function [e_sig, varargout] = Electricalsignal(obj,options)
 
             arguments
@@ -70,6 +72,7 @@ classdef Signal
 
         end
 
+        %% CONVERT TO Opticalsignal
         function o_sig = Opticalsignal(obj, options)
 
             arguments
@@ -91,9 +94,9 @@ classdef Signal
             if isa(obj,'Electricalsignal')
 
                 %convert to optical
-                
+
                 o_sig = Opticalsignal(obj.signal,"fs",obj.fs,"lambda",options.lambda,"logbook",obj.logbook,"nase",options.nase);
- 
+
 
             elseif isa(obj,'Informationsignal')
 
@@ -104,12 +107,14 @@ classdef Signal
         end
 
 
+        %% Display length
         function return_length = length(obj)
             %METHOD1 Summary of this method goes here
             %   Detailed explanation goes here
             return_length = length(obj.signal);
         end
 
+        %% Write Logbook Entry
         function obj = logbookentry(obj,varargin)
 
             if nargin > 1
@@ -130,6 +135,7 @@ classdef Signal
 
         end
 
+        %% Resample Signal
         function obj = resample(obj,options)
 
             arguments
@@ -146,6 +152,104 @@ classdef Signal
 
         end
 
+        %%
+        function spectrum(obj,fsamp,options)
+
+            arguments
+                obj
+                fsamp
+                options.figurename = [];
+                options.displayname = [];
+            end
+
+            %Get figure if there is already a spectrum plot -> I want to add the new
+            %spectum "onto" the existing plot to have a better comparison
+            if isempty(options.figurename)
+                fig = findall(groot, 'Type', 'figure', 'Name', 'power density');
+                if isvalid(fig)
+                    fig = get(fig);
+                    hold on
+                else
+                    figure('name','power density');
+                end
+            else
+                fig = findall(groot, 'Type', 'figure', 'Name', options.figurename);
+                if isvalid(fig)
+                    fig = get(fig);
+                    hold on
+                else
+                    figure('name',options.figurename);
+                end
+
+            end
+
+
+            %compute FFT of input
+            Fsignal = fft(obj.signal);
+
+            %POWER spectral density (todo: toggle?)
+            psd = Fsignal.*conj(Fsignal);
+
+            %Use only magnitude of FFT (which was complex)
+            psd = abs(psd);
+
+            %Shift the spectrum to yield
+            psd = fftshift(psd);
+
+            %divide by N
+            psd = psd/length(Fsignal);
+
+            %smoothing
+            psd = smooth(psd,100);
+
+            psd_plot = 20*log10(psd);
+
+
+            testParseval = 1;
+            if testParseval == 1
+                E_FreqDomain = sum(psd);
+                %test parseval
+                E_TimeDomain = sum(abs(Fsignal.^2));
+
+                if isequal(round(E_FreqDomain,1),round(E_TimeDomain,1))
+                    %disp('Parseval is right!');
+                else
+                    disp('Parseval theorem is not right...');
+                end
+            end
+
+            if fsamp <= 1e+100
+                %Frequency Axis
+                freq_vec = linspace(-fsamp/2,fsamp/2,length(psd));
+                freq_vec = reshape(freq_vec,size(psd_plot));
+
+
+                if ~isempty(options.displayname)
+                    plot(freq_vec*1e-9,psd_plot,'Linewidth',0.5,'DisplayName',options.displayname);
+                else
+                    plot(freq_vec*1e-9,psd_plot,'Linewidth',0.5);
+                end
+
+                xlabel('Frequency [GHz]')
+            else
+                %Wavelength Axis
+                freq_vec = physconst('LightSpeed')*linspace(-fsamp/2,fsamp/2,length(psd))./((physconst('LightSpeed')/1550e-9)^2);
+                if ~isempty(options.displayname)
+                    plot(freq_vec*1e9,psd_plot,'Linewidth',0.5,'DisplayName',options.displayname);
+                else
+                    plot(freq_vec*1e9,psd_plot,'Linewidth',0.5);
+                end
+
+                xlabel('Wavelength [nm]')
+            end
+
+
+            ylabel('Magnitude [dB]')
+            legend
+            grid minor;
+
+        end
+
     end
 end