145 lines
4.0 KiB
Matlab
145 lines
4.0 KiB
Matlab
function h = plotRefl(port, varargin)
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% h = plotRefl(port,varargin)
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%
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% plot the reflection coefficient of a port into a Smith chart.
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% left and right facing triangles mark the lower and upper cutoff
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% frequency of the pass bands. An asterisk marks the frequnecy with
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% the lowest reflection.
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%
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% input:
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% port: port data structure. Call calcPort with an appropriate
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% frequency vector before calling this routine
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%
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% output: graphics handle for further modification of the plot.
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%
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% variable input:
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% 'precision': - number of decimal places (floating point precision)
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% for the frequency (always in MHz), default is 0
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% 'threshold': - Threshold value (in dB) for the upper and lower
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% cutoff frequency, default is -3
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% example:
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% myport = calcPort(myport, Sim_Path, linspace(f_0-f_c, f_0+f_c, 200));
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% plotRefl(myport);
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%
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% See also calcPort
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%
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% openEMS matlab interface
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% -----------------------
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% author: Georg Michel
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%defaults
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precision = 0;
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threshold = -3;
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for n=1:2:numel(varargin)
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if (strcmp(varargin{n},'precision')==1);
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precision = varargin{n+1};
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elseif (strcmp(varargin{n},'threshold')==1);
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threshold = varargin{n+1};
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else
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warning('openEMS:polarFF',['unknown argument key: ''' varargin{n} '''']);
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end
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end
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if ~isfield(port, 'uf')
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error('Cannot plot the reflection coefficient. Please call calcPort first.');
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end
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s11 = port.uf.ref ./ port.uf.inc;
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ffmt = ['%.', num2str(precision), 'f'];
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figure; %new figure
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plot([-1, 1], [0, 0], 'k');
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axis ([-1.15, 1.15, -1.15, 1.15], "square");
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axis off;
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hold on
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ReZ = [.2; .5; 1; 2];
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ImZ = 1i * [1 2 5 2];
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Z = bsxfun(@plus, ReZ, linspace(-ImZ, ImZ, 256));
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Gamma = (Z-1)./(Z+1);
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plot(Gamma.', 'k');
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ReZ = [.5 .5 1 1 2 2 5 5 10 10];
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ImZ = 1i * [-.2; .2; -.5; .5; -1; 1; -2; 2; -5; 5];
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Z = bsxfun(@plus, linspace(0, ReZ, 256), ImZ);
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Gamma = (Z-1)./(Z+1);
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plot(Gamma.', 'k');
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angle = linspace (0, 2 * pi, 256); ReZ = [0 5 10];
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center = ReZ ./ (ReZ + 1);
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radius = 1 ./ (ReZ + 1);
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plot(bsxfun(@plus, bsxfun(@times, radius, cos(angle.')), center), bsxfun(@times, radius, sin(angle.')), 'k');
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% resistance
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ReZ = [0.2 0.5 1 2 5 10]; ImZ = zeros (1, length (ReZ));
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rho = (ReZ.^2 + ImZ.^2 - 1 + 2i * ImZ) ./ ((ReZ + 1).^2 + ImZ.^2);
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xoffset = [0.1 0.1 0.05 0.05 0.05 0.075];
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yoffset = -0.03;
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for idx = 1:length (ReZ)
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text (real (rho(idx)) - xoffset(idx), ...
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imag (rho(idx)) - yoffset, num2str (ReZ(idx)));
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end
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% reactance
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ReZ = [-0.06 -0.06 -0.06 -0.12 -0.5];
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ImZ = [0.2 0.5 1 2 5];
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rho = (ReZ.^2 + ImZ.^2 - 1 + 2i * ImZ) ./ ((ReZ + 1).^2 + ImZ.^2);
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for idx = 1:length (ImZ)
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text (real (rho(idx)), imag (rho(idx)), [num2str(ImZ(idx)), "j"]);
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text (real (rho(idx)), -imag (rho(idx)), [num2str(-ImZ(idx)), "j"]); end
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% zero
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rho = (-0.05.^2 + 0.^2 - 1) ./ ((-0.05 + 1).^2 + 0.^2);
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text (real (rho), imag (rho), '0');
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s11dB = 20*log10(abs(s11));
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upperind = s11dB(1:end-1) < threshold & s11dB(2:end) > threshold;
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lowerind = s11dB(1:end-1) > threshold & s11dB(2:end) < threshold;
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minind = nthargout(2, @min, s11dB);
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handle1 = plot(s11(lowerind),['<','b']);
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handle2 = plot(s11(upperind),['>','b']);
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handle3 = plot(s11(minind),['*', 'b']);
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llegend = num2str(port.f(lowerind)(1)/1e6, ffmt);
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ulegend = num2str(port.f(upperind)(1)/1e6, ffmt);
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if nnz(lowerind) > 1
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for i= 2:nnz(lowerind)
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llegend = strjoin({llegend, num2str(port.f(lowerind)(i)/1e6, ffmt)}, ', ');
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end
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end
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if nnz(upperind) > 1
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for i= 2:nnz(upperind)
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ulegend = strjoin({ulegend, num2str(port.f(upperind)(i)/1e6, ffmt)}, ', ');
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end
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end
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legend([handle1, handle2, handle3], {[llegend, " MHz"], ...
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[ulegend, " MHz"], ...
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[num2str(20*log10(abs(s11(minind))), "%4.0f"), ...
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"dB @ ", num2str(port.f(minind)/1e6, ffmt), " MHz"]});
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h = plot(s11);
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if (nargout == 0)
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clear h;
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end
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end |