morasu
Newbie level 4
Hi guys,
I am trying to see how much attenuation I am going to get with a signal with a center frequency of 416.7 kHz going through about 100 meters of a cable. I was calculating the impedance by taking the square route of the cable resistance squared plus the capacitive reactance squared. I was getting about -4 dBV, which seems about right but after including the inductive reactance in the calculation, I am getting a gain of 5 dBV. I do not know why I am getting a positive gain when the signal should be attenuated. Should I ignore the inductance? Underneath is a copy of my .m. Any information on the subject would be greatly appreciated.
I am trying to see how much attenuation I am going to get with a signal with a center frequency of 416.7 kHz going through about 100 meters of a cable. I was calculating the impedance by taking the square route of the cable resistance squared plus the capacitive reactance squared. I was getting about -4 dBV, which seems about right but after including the inductive reactance in the calculation, I am getting a gain of 5 dBV. I do not know why I am getting a positive gain when the signal should be attenuated. Should I ignore the inductance? Underneath is a copy of my .m. Any information on the subject would be greatly appreciated.
Code:
close all; clear all; clc;
v1 = 24; % max voltage input of hydrophone
I = 200*10^-3; % max current of hydrophone
l = 0.59058*10^-6*100; % inductance of cable for 100m
c = 108.273*10^-12*100; %capacitance of cable for 100m
f = linspace(374000.7,458000.7); %frequency range of hydrophone
xc = (2*pi*f*c).^-1; %capacitive reactance
xl = (2*pi*f*l); % inductive reactance
x = xc; % reactance
z = sqrt(67^2 + x.^2); % total impedance sqrt(R^2 + X^2)
v2 = I.*z; % output voltage
g = v2./v1; % Gain
G = 20*log10(g);
plot(f,G)
xlabel('Frequency (Hz)')
ylabel('Gain (dB)')
title('Gain vs Frequency for 100 m of Cable')
figure(2)
plot(f,z)
xlabel('Frequency (Hz)')
ylabel('Impedance (Ohms)')
title('Impedance vs Frequency for 100 m of Cable')
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