Plotting the attenuation constant against frequency

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Vinci
Vinci 2021-3-23
回答： VBBV 2024-9-3
Hello, I'm trying to plot the attenuation coefficient and phase coefficient against a frequency range. The values produced for a single freqency check out correct but my plots don't look similar to the characteristics curves that that I'm expecting from textbooks. Am I messing up the units or dimensions somewhere?
% Clear screen and variables
clc, clear all
% Define distributed parameters
R = 100;
L = 80e-9;
C = 200e-12;
G = 1.6;
% Define frequency range
low_freq = 1; % Enter low frequency here
high_freq = 1e7; % Enter high frequency here
% Calculate frequency axis
freq = low_freq:high_freq;
% Angular frequency
omega = 2*pi.*freq;
% Propagation coefficient
gamma = sqrt((R+(omega.*L*i)).*(G+(omega.*C*i)));
% Attenuation coefficient
alpha = real(gamma);
% Phase coefficient
beta = imag(gamma);
% Plot attenuation coefficient verses frequency
figure('units','pixels','position',[150 200 1000 600])%Set figure properties
plot (freq,alpha)
grid on
title('Attenuation Coefficient verses frequency')% Graph title
xlabel('Frequency (Hz)')% x axis label
ylabel('Attenuation Coefficient')% y axis label
% Plot phase coefficient verses frequency
figure('units','pixels','position',[150 200 1000 600])%Set figure properties
plot (freq,beta)
grid on
title('Phase Coefficient verses frequency')% Graph title
xlabel('Frequency (Hz)')% x axis label
ylabel('Phase Coefficient')% y axis label
  3 个评论
显示 1更早的评论
Vinci
Vinci 2021-3-27
Sorry about the late response. I was expecting something like this.
Mathieu NOE
Mathieu NOE 2021-3-29
So far I believe the input values are simply not compatible / coherent with this plot
you cannot have gamme as low as 2e-3 (max y value on this graph) with
R = 100;
L = 80e-9;
C = 200e-12;
G = 1.6;

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回答（2 个）

Abrham De La Torre
Abrham De La Torre 2021-9-29
12
VBBV
VBBV 2024-9-3
Ran in:
@Vinci Use smaller conductnce value, and semilogx for ploting graph
% Clear screen and variables
clc, clear all
% Define distributed parameters
R = 100;
L = 80e-9;
C = 200e-12;
G = 1.6e-12; % conductance valoue is small,
% Define frequency range
low_freq = 1; % Enter low frequency here
high_freq = 1e7; % Enter high frequency here
% Calculate frequency axis
freq = low_freq:1:high_freq;
% Angular frequency
omega = 2*pi.*freq;
% Propagation coefficient
gamma = sqrt((R+(omega.*L*i)).*(G+(omega.*C*i)));
% Attenuation coefficient
alpha = real(gamma);
% Phase coefficient
beta = imag(gamma);
% Plot attenuation coefficient verses frequency
subplot(211)
semilogx((freq),alpha)
axis([min(freq), max(freq) min(alpha) max(alpha)])
title('Attenuation Coefficient verses frequency')% Graph title
xlabel('Frequency (Hz)')% x axis label
ylabel('Attenuation Coefficient')% y axis label
% Plot phase coefficient verses frequency
subplot(212)
semilogx(freq,beta)
axis([min(freq), max(freq) min(beta) max(beta)])
title('Phase Coefficient verses frequency')% Graph title
xlabel('Frequency (Hz)')% x axis label
ylabel('Phase Coefficient')% y axis label

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