new plots for Diss. Mostly AI gen. Few changes in actual codebase

Classes/01_transmit/ChannelFreqResp.m

@@ -212,6 +212,81 @@ classdef ChannelFreqResp < handle
 
         end
 
+        function Target = apply(obj,Target,options)
+            % Apply the measured magnitude-only channel response.
+            arguments
+                obj
+                Target
+                options.fileName = ''
+                options.loadPath = ''
+                options.maxampdb double = 0
+            end
+
+            if isempty(obj.H)
+                obj.load("fileName",options.fileName,"loadPath",options.loadPath);
+            end
+
+            fstarget = Target.fs;
+            N_target = numel(Target.signal);
+
+            % Ignore measured DC attenuation when setting the response
+            % reference level.
+            H_measured = abs(obj.H(:)).';
+            H_measured_valid = isfinite(H_measured);
+            H_measured_dB = 20*log10(H_measured);
+
+            idx_old = (obj.faxis > 0) & ...
+                (obj.faxis < fstarget/2) & H_measured_valid;
+            H_reference_dB = max(H_measured_dB(idx_old));
+
+            H_measured_dB = H_measured_dB - H_reference_dB + options.maxampdb;
+            H_measured = 10.^(H_measured_dB/20);
+            H_measured(~H_measured_valid) = 0;
+
+            % Positive-frequency FFT bins, excluding DC and Nyquist.
+            N_positive = floor((N_target - 1)/2);
+            fnew = (1:N_positive)*fstarget/N_target;
+
+            f_old = obj.faxis(idx_old);
+            H_old = H_measured(idx_old);
+            H_interp = interp1(f_old,H_old,fnew,'linear');
+
+            % Match the edge handling used by the precompensation path.
+            nH = find(isfinite(H_interp),1,'first');
+            if isempty(nH)
+                error('ChannelFreqResp:InterpolationFailed', ...
+                    'The measured response does not overlap the target frequency grid.');
+            end
+            H_interp(1:nH-1) = H_interp(nH);
+
+            nH = find(isfinite(H_interp),1,'last');
+            H_interp(nH+1:end) = H_interp(nH);
+
+            % Real, zero-phase, conjugate-symmetric FFT response.
+            if mod(N_target,2) == 0
+                H_apply = [H_interp(1), H_interp, 0, fliplr(H_interp)];
+            else
+                H_apply = [H_interp(1), H_interp, fliplr(H_interp)];
+            end
+            H_apply = H_apply(:);
+
+            % Re-anchor the final interpolated response using only the
+            % positive-frequency bins, so DC attenuation is ignored.
+            H_apply_dB = 20*log10(abs(H_apply));
+            positive_bins = 2:(N_positive + 1);
+            H_apply_dB = H_apply_dB - max(H_apply_dB(positive_bins)) + options.maxampdb;
+            H_apply = 10.^(H_apply_dB/20);
+
+            obj.H_apply = H_apply;
+
+            % Apply the channel in the frequency domain and preserve shape.
+            signal_shape = size(Target.signal);
+            signal_in = real(Target.signal(:));
+            signal_out = real(ifft(fft(signal_in).*H_apply));
+            Target.signal = reshape(signal_out,signal_shape);
+
+        end
+
         function plot(obj)
 
             figure();