1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
|
function h = plotRefl(port, varargin)
% h = plotRefl(port,varargin)
%
% plot the reflection coefficient of a port into a Smith chart.
% left and right facing triangles mark the lower and upper cutoff
% frequency of the pass bands. An asterisk marks the frequnecy with
% the lowest reflection.
%
% input:
% port: port data structure. Call calcPort with an appropriate
% frequency vector before calling this routine
%
% output: graphics handle for further modification of the plot.
%
% variable input:
% 'precision': - number of decimal places (floating point precision)
% for the frequency (always in MHz), default is 0
% 'threshold': - Threshold value (in dB) for the upper and lower
% cutoff frequency, default is -3
% example:
% myport = calcPort(myport, Sim_Path, linspace(f_0-f_c, f_0+f_c, 200));
% plotRefl(myport);
%
% See also calcPort
%
% openEMS matlab interface
% -----------------------
% author: Georg Michel
%defaults
precision = 0;
threshold = -3;
for n=1:2:numel(varargin)
if (strcmp(varargin{n},'precision')==1);
precision = varargin{n+1};
elseif (strcmp(varargin{n},'threshold')==1);
threshold = varargin{n+1};
else
warning('openEMS:polarFF',['unknown argument key: ''' varargin{n} '''']);
end
end
if ~isfield(port, 'uf')
error('Cannot plot the reflection coefficient. Please call calcPort first.');
end
s11 = port.uf.ref ./ port.uf.inc;
ffmt = ['%.', num2str(precision), 'f'];
figure; %new figure
plot([-1, 1], [0, 0], 'k');
axis ([-1.15, 1.15, -1.15, 1.15], "square");
axis off;
hold on
ReZ = [.2; .5; 1; 2];
ImZ = 1i * [1 2 5 2];
Z = bsxfun(@plus, ReZ, linspace(-ImZ, ImZ, 256));
Gamma = (Z-1)./(Z+1);
plot(Gamma.', 'k');
ReZ = [.5 .5 1 1 2 2 5 5 10 10];
ImZ = 1i * [-.2; .2; -.5; .5; -1; 1; -2; 2; -5; 5];
Z = bsxfun(@plus, linspace(0, ReZ, 256), ImZ);
Gamma = (Z-1)./(Z+1);
plot(Gamma.', 'k');
angle = linspace (0, 2 * pi, 256); ReZ = [0 5 10];
center = ReZ ./ (ReZ + 1);
radius = 1 ./ (ReZ + 1);
plot(bsxfun(@plus, bsxfun(@times, radius, cos(angle.')), center), bsxfun(@times, radius, sin(angle.')), 'k');
% resistance
ReZ = [0.2 0.5 1 2 5 10]; ImZ = zeros (1, length (ReZ));
rho = (ReZ.^2 + ImZ.^2 - 1 + 2i * ImZ) ./ ((ReZ + 1).^2 + ImZ.^2);
xoffset = [0.1 0.1 0.05 0.05 0.05 0.075];
yoffset = -0.03;
for idx = 1:length (ReZ)
text (real (rho(idx)) - xoffset(idx), ...
imag (rho(idx)) - yoffset, num2str (ReZ(idx)));
end
% reactance
ReZ = [-0.06 -0.06 -0.06 -0.12 -0.5];
ImZ = [0.2 0.5 1 2 5];
rho = (ReZ.^2 + ImZ.^2 - 1 + 2i * ImZ) ./ ((ReZ + 1).^2 + ImZ.^2);
for idx = 1:length (ImZ)
text (real (rho(idx)), imag (rho(idx)), [num2str(ImZ(idx)), "j"]);
text (real (rho(idx)), -imag (rho(idx)), [num2str(-ImZ(idx)), "j"]); end
% zero
rho = (-0.05.^2 + 0.^2 - 1) ./ ((-0.05 + 1).^2 + 0.^2);
text (real (rho), imag (rho), '0');
s11dB = 20*log10(abs(s11));
upperind = s11dB(1:end-1) < threshold & s11dB(2:end) > threshold;
lowerind = s11dB(1:end-1) > threshold & s11dB(2:end) < threshold;
minind = nthargout(2, @min, s11dB);
handle1 = plot(s11(lowerind),['<','b']);
handle2 = plot(s11(upperind),['>','b']);
handle3 = plot(s11(minind),['*', 'b']);
llegend = num2str(port.f(lowerind)(1)/1e6, ffmt);
ulegend = num2str(port.f(upperind)(1)/1e6, ffmt);
if nnz(lowerind) > 1
for i= 2:nnz(lowerind)
llegend = strjoin({llegend, num2str(port.f(lowerind)(i)/1e6, ffmt)}, ', ');
end
end
if nnz(upperind) > 1
for i= 2:nnz(upperind)
ulegend = strjoin({ulegend, num2str(port.f(upperind)(i)/1e6, ffmt)}, ', ');
end
end
legend([handle1, handle2, handle3], {[llegend, " MHz"], ...
[ulegend, " MHz"], ...
[num2str(20*log10(abs(s11(minind))), "%4.0f"), ...
"dB @ ", num2str(port.f(minind)/1e6, ffmt), " MHz"]});
h = plot(s11);
if (nargout == 0)
clear h;
end
end
|
