3676d92b30
+ duobinary_target now supports memoryless decoding (FFE targets DB response without MLSE) + PAMmapper.quantize now supports custom constellations for quantization + Added a new folder 'Documentations' for pdfs, slides, etc. + Added new FSO evaluation scripts in projects/FSO transmission/Evaluation Scripts + Added ffe_db (rudimentary module, not important anymore)
130 lines
4.4 KiB
Matlab
130 lines
4.4 KiB
Matlab
classdef Electrical_Hybrid < handle
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properties(Access=public)
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file_path
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plot = 0
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% If true: perform digital residual-echo cancellation using known TX
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cancel_echo = 1
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% If true: in addition return v_hyb and v_echo_est
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return_intermediates = 1
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end
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methods(Access=public)
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function obj = Electrical_Hybrid(options)
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arguments
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options.file_path = ''
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options.plot = 0
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options.cancel_echo = 1
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options.return_intermediates = 1
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end
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fn = fieldnames(options);
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for n = 1:numel(fn)
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obj.(fn{n}) = options.(fn{n});
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end
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end
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function [v_fe_rec, v_hyb, v_echo_est] = process(obj, v_ne_tx, v_fe_tx)
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% v_ne_tx : Near-End TX signal object (Port 1)
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% v_fe_tx : Far-End TX signal object (Port 2)
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%
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% Output:
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% v_hyb : physical hybrid differential output (Port4 - Port3)
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% v_echo_est : estimated residual echo due to local TX only
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% v_fe_rec : v_hyb - v_echo_est (if cancel_echo enabled), else v_hyb
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% --- Load S-Parameters (.s4p) ---
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net = sparameters(obj.file_path);
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f_s = net.Frequencies(:);
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S4 = net.Parameters;
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% Extract needed S-parameters for differential output:
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% V3 = S31*V1 + S32*V2
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% V4 = S41*V1 + S42*V2
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% Vhyb = V4 - V3 = (S41-S31)*V1 + (S42-S32)*V2
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S31_s = squeeze(S4(3,1,:));
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S41_s = squeeze(S4(4,1,:));
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S32_s = squeeze(S4(3,2,:));
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S42_s = squeeze(S4(4,2,:));
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% --- Time-domain signals ---
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x1 = v_ne_tx.signal(:);
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x2 = v_fe_tx.signal(:);
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if length(x2) ~= length(x1)
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error('Near-end and far-end signals must have the same length.');
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end
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N = length(x1);
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Fs = v_ne_tx.fs;
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% --- Use zero padding to avoid circular convolution artifacts ---
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Nfft = 2^nextpow2(2*N); % robust choice
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% --- FFT ---
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V1 = fft(x1, Nfft);
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V2 = fft(x2, Nfft);
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% --- Frequency axis for interpolation (signed then abs) ---
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f_fft = (0:Nfft-1).' * (Fs/Nfft);
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f_signed = f_fft;
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idxNeg = f_signed > Fs/2;
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f_signed(idxNeg) = f_signed(idxNeg) - Fs; % (-Fs/2, Fs/2]
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f_pos = abs(f_signed);
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% --- Interpolate S-parameters onto f_pos ---
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S31 = interp1(f_s, S31_s, f_pos, 'linear', 'extrap');
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S41 = interp1(f_s, S41_s, f_pos, 'linear', 'extrap');
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S32 = interp1(f_s, S32_s, f_pos, 'linear', 'extrap');
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S42 = interp1(f_s, S42_s, f_pos, 'linear', 'extrap');
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% Hermitian symmetry for real time-domain response:
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% For negative frequencies enforce conj symmetry.
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S31(idxNeg) = conj(S31(idxNeg));
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S41(idxNeg) = conj(S41(idxNeg));
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S32(idxNeg) = conj(S32(idxNeg));
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S42(idxNeg) = conj(S42(idxNeg));
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% --- Physical hybrid differential output ---
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% Vhyb = (S41-S31)*V1 + (S42-S32)*V2
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He = (S41 - S31); % residual echo transfer from local TX
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Hr = (S42 - S32); % transfer from far-end TX to output
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V_hyb = He .* V1 + Hr .* V2;
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% --- Residual echo estimate (digital canceller model) ---
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V_echo = He .* V1;
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% --- Back to time-domain (take first N samples after padding) ---
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v_hyb_full = ifft(V_hyb, 'symmetric');
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v_echo_full = ifft(V_echo, 'symmetric');
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v_hyb = v_hyb_full(1:N);
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v_echo_est = v_echo_full(1:N);
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% --- Optional cancellation ---
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if obj.cancel_echo
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v_fe_rec = v_hyb - v_echo_est;
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else
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v_fe_rec = v_hyb;
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end
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if ~obj.return_intermediates
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v_hyb = [];
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v_echo_est = [];
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end
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% --- Bring output in the correct form ---
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v_fe_rec = Informationsignal(v_fe_rec,"fs",v_fe_tx.fs);
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v_hyb = Informationsignal(v_hyb,"fs",v_fe_tx.fs);
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v_echo_est = Informationsignal(v_echo_est,"fs",v_fe_tx.fs);
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if obj.plot
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rfplot(net)
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end
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end
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end
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end |