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Theory stuff from sials work pc; minor stuff here and there

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Silas Oettinghaus
2026-02-19 15:11:32 +01:00
parent 1b8d83dec0
commit 2a724b833f
14 changed files with 810 additions and 39 deletions
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Functions/plot_s_parameter.m Normal file
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%% Plot S-parameters from Touchstone S2P or S4P (schema-aware, no RF Toolbox)
clear; clc;
[file,path] = uigetfile({"*.s2p;*.S2P;*.s4p;*.S4P","Touchstone (*.s2p, *.s4p)"});
if isequal(file,0); return; end
filename = fullfile(path,file);
%%
% Decide port count by extension (minimal-invasive, robust)
[~,~,ext] = fileparts(file);
ext = upper(ext);
if strcmp(ext,'.S4P')
[matrix, meta] = loads4p_schema(filename);
N = 4;
elseif strcmp(ext,'.S2P')
[matrix, meta] = loads2p(filename); % your original loader kept (below)
N = 2;
else
error("Unsupported extension: %s", ext);
end
% Frequency in GHz
frex = matrix(:,1);
if isfield(meta,'freqScaleHz') && ~isempty(meta.freqScaleHz)
frex = frex * meta.freqScaleHz / 1e9; % convert to GHz
else
% fallback heuristic (your original)
for i = 1:numel(frex)
if frex(i) > 1e4
frex(i) = frex(i).*1e-9;
end
end
end
figure(101);
hold on;
% overlay indexing: count lines already there
if N == 2
lines = numel(findall(gcf, 'type','line'))/4 + 1;
else
lines = numel(findall(gcf, 'type','line'))/16 + 1;
end
% styles (kept)
[CC, LL, MM] = ndgrid({1,2,3,4}, {'-', ':', '-.', '--'}, {'none','+', 'o', '*', 'square', 'diamond'});
combinations = [CC(:), LL(:), MM(:)];
cols = [0.3467 0.5360 0.6907
0.9153 0.2816 0.2878
0.4416 0.7490 0.4322
1.0000 0.5984 0.2000];
% -------------------- Plotting --------------------
if N == 2
heads = ["S11","S12","S22","S21"];
% matrix layout from loads2p:
% col pairs:
% 2-3 S11, 4-5 S21, 6-7 S12, 8-9 S22
colPairs = [2 3; 6 7; 8 9; 4 5]; % order matches heads above
subplots = 1;
for k = 1:4
if subplots, subplot(2,2,k); else, figure('Color','w'); end
hold on; grid on;
reCol = colPairs(k,1);
imCol = colPairs(k,2);
% S-parameter magnitude in dB: 20*log10(|S|)
response = 20*log10(abs(matrix(:,reCol) + 1i.*matrix(:,imCol)));
response = movmean(response,1);
plot(frex, response, ...
"Color", cols(combinations{lines,1},:), ...
"DisplayName", file, ...
"LineStyle", combinations{lines,2}, ...
"Marker", combinations{lines,3}, ...
"MarkerSize", 3);
if k == 2 || k == 3
ylim([-6 2]);
else
ylim([-30 2]);
end
xlim([0 100]);
title(heads(k));
xlabel('Frequency in GHz');
ylabel('|S| (dB)');
legend('Location','best');
end
sgtitle(sprintf('S-Parameters (2-port) [%s]', meta.headerLine));
elseif N == 4
% For s4p schema we plot all Sij in a 4x4 grid
% matrix layout from loads4p_schema:
% columns: 1=f, then pairs in order:
% S11,S12,S13,S14, S21..S24, S31..S34, S41..S44
subplots = 1;
for i = 1:4
for j = 1:4
sp = (i-1)*4 + j;
if subplots, subplot(4,4,sp); else, figure('Color','w'); end
hold on; grid on;
idx = (i-1)*4 + j; % 1..16 for Sij in row-major
reCol = 1 + 2*(idx-1) + 1; % after freq col
imCol = 1 + 2*(idx-1) + 2;
response = 20*log10(abs(matrix(:,reCol) + 1i.*matrix(:,imCol)));
plot(frex, response, ...
"Color", cols(combinations{lines,1},:), ...
"DisplayName", file, ...
"LineStyle", combinations{lines,2}, ...
"Marker", combinations{lines,3}, ...
"MarkerSize", 2);
xlim([0 100]);
title(sprintf("S%d%d", i, j));
set(gca,'FontSize',8);
% reduce clutter
if j ~= 1, yticklabels([]); end
if i ~= 4, xticklabels([]); end
if j == 1, ylabel('|S| (dB)'); end
if i == 4, xlabel('GHz'); end
end
end
sgtitle(sprintf('S-Parameters (4-port) [%s]', meta.headerLine));
end
%% ========================================================================
% Loader for S4P with the EXACT provided schema (4 lines per frequency)
% ========================================================================
function [matrix, meta] = loads4p_schema(filepath)
meta = struct();
meta.headerLine = "";
meta.freqScaleHz = []; % Hz per file unit (e.g., GHz -> 1e9)
fid = fopen(filepath,'r');
if fid < 0, error("Cannot open file: %s", filepath); end
cleaner = onCleanup(@() fclose(fid));
% Parse header: find "#"
freUnit = "";
while true
t = fgetl(fid);
if ~ischar(t), break; end
ts = strtrim(t);
if startsWith(ts,'#')
meta.headerLine = ts;
parts = split(upper(string(ts)));
if numel(parts) >= 2, freUnit = parts(2); end
switch freUnit
case "HZ", meta.freqScaleHz = 1;
case "KHZ", meta.freqScaleHz = 1e3;
case "MHZ", meta.freqScaleHz = 1e6;
case "GHZ", meta.freqScaleHz = 1e9;
otherwise, meta.freqScaleHz = [];
end
break;
end
end
data = [];
while true
l1 = nextNumericLine(fid);
if strlength(l1) == 0
break;
end
% IMPORTANT: sscanf wants char for robust behavior
v1 = sscanf(char(l1), '%f').';
if numel(v1) < 9
error("S4P schema mismatch: expected 9 numbers on first line of a block, got %d.\nLine: %s", numel(v1), char(l1));
end
l2 = nextNumericLine(fid); if strlength(l2)==0, error("Unexpected EOF after first S4P line."); end
l3 = nextNumericLine(fid); if strlength(l3)==0, error("Unexpected EOF after second S4P line."); end
l4 = nextNumericLine(fid); if strlength(l4)==0, error("Unexpected EOF after third S4P line."); end
v2 = sscanf(char(l2), '%f').';
v3 = sscanf(char(l3), '%f').';
v4 = sscanf(char(l4), '%f').';
if numel(v2) < 8 || numel(v3) < 8 || numel(v4) < 8
error("S4P schema mismatch: expected 8 numbers on continuation lines.\nL2: %s\nL3: %s\nL4: %s", char(l2), char(l3), char(l4));
end
f = v1(1);
s1 = v1(2:9); % S11..S14 (re/im pairs)
s2 = v2(1:8); % S21..S24
s3 = v3(1:8); % S31..S34
s4 = v4(1:8); % S41..S44
row = [f, s1, s2, s3, s4]; % 1 + 32 = 33 columns
data = [data; row]; %#ok<AGROW>
end
matrix = data;
end
function ln = nextNumericLine(fid)
ln = "";
while true
t = fgetl(fid);
if ~ischar(t)
ln = "";
return;
end
ts = strtrim(t);
% Skip blanks and comments and header lines
if ts=="" || startsWith(ts,'!') || startsWith(ts,'#')
continue;
end
% Remove inline comment after '!' if present
excl = strfind(ts,'!');
if ~isempty(excl)
ts = strtrim(extractBefore(ts, excl(1)));
if ts==""; continue; end
end
% Keep only if there's at least one numeric token
if ~isempty(regexp(ts,'[-+]?\d*\.?\d+(?:[eEdD][-+]?\d+)?','once'))
ln = string(ts);
return;
end
end
end
%% ========================================================================
% Your original loads2p (kept as-is, but returns meta too)
% ========================================================================
function [matrix, meta] = loads2p(filepath)
meta = struct();
meta.headerLine = "";
meta.freqScaleHz = [];
% Try to read # line for unit scaling (minimal invasive)
fid = fopen(filepath,'r');
if fid >= 0
cleaner = onCleanup(@() fclose(fid));
while true
t = fgetl(fid);
if ~ischar(t), break; end
ts = strtrim(t);
if startsWith(ts,'#')
meta.headerLine = ts;
parts = split(upper(string(ts)));
if numel(parts) >= 2
switch parts(2)
case "HZ", meta.freqScaleHz = 1;
case "KHZ", meta.freqScaleHz = 1e3;
case "MHZ", meta.freqScaleHz = 1e6;
case "GHZ", meta.freqScaleHz = 1e9;
end
end
break;
end
end
end
startRow = 2;
formatSpec = '%20s%25s%23s%23s%23s%23s%23s%23s%23s%s%[^\n\r]';
fileID = fopen(filepath,'r');
dataArray = textscan(fileID, formatSpec, 'Delimiter', '', 'WhiteSpace', '', ...
'TextType', 'string', 'HeaderLines' ,startRow-1, 'ReturnOnError', false, 'EndOfLine', '\r\n');
fclose(fileID);
raw = repmat({''},length(dataArray{1}),length(dataArray)-1);
for col=1:length(dataArray)-1
raw(1:length(dataArray{col}),col) = mat2cell(dataArray{col}, ones(length(dataArray{col}), 1));
end
numericData = NaN(size(dataArray{1},1),size(dataArray,2));
for col=[1,2,3,4,5,6,7,8,9,10]
rawData = dataArray{col};
for row=1:size(rawData, 1)
regexstr = '(?<prefix>.*?)(?<numbers>([-]*(\d+[\,]*)+[\.]{0,1}\d*[eEdD]{0,1}[-+]*\d*[i]{0,1})|([-]*(\d+[\,]*)*[\.]{1,1}\d+[eEdD]{0,1}[-+]*\d*[i]{0,1}))(?<suffix>.*)';
try
result = regexp(rawData(row), regexstr, 'names');
numbers = result.numbers;
invalidThousandsSeparator = false;
if numbers.contains(',')
thousandsRegExp = '^[-/+]*\d+?(\,\d{3})*\.{0,1}\d*$';
if isempty(regexp(numbers, thousandsRegExp, 'once'))
numbers = NaN;
invalidThousandsSeparator = true;
end
end
if ~invalidThousandsSeparator
numbers = textscan(char(strrep(numbers, ',', '')), '%f');
numericData(row, col) = numbers{1};
raw{row, col} = numbers{1};
end
catch
raw{row, col} = rawData{row};
end
end
end
R = cellfun(@(x) ~isnumeric(x) && ~islogical(x),raw);
raw(R) = {NaN};
matrix = cell2mat(raw);
end