Last graph is plotted with no data points(figure 3) dont know why

clc;
clear all;
close all;
% strength of signal is inversely proportional to the distance between Tx
% and Rx
d= 0:1:10
signal_strength = (1)./(d*exp(2)); %  where d is  the distance between Tx and Rx
figure(1)
plot(d,signal_strength) % simple plot of signal strength vs distance between Tx and Rx
title('Signal Strength against Distance of Transmission')
ylabel('Signal Strength(dBm)')
xlabel('Transmission Distance(kM)')

% signal strength equation
u = 4*pi*10*exp(-7); % constant 
c = 3000000; % speed of light in kM per second
P = 500; % power transmission assumed to be 5000 watts
signal_strength_ = sqrt((u*c*P)./(2*pi*d*exp(2)));
figure(2)
plot(d,signal_strength_)
title('Signal Strength against Distance of Transmission')
ylabel('Signal Strength(dBm)')
xlabel('Transmission Distance(kM)')

% Signal Attenuation Plot

Signal_Attenuation = ((signal_strength_-30) / d)
figure(3)
plot(d,Signal_Attenuation)
title('Signal Attenuation vs Distance')
ylabel('Signal Attenuation(dB)')
xlabel('Tx to Rx Distance(kM)')

% signal attenuation plot graph is plotted without any data points and i
% cant seem to identify the problem please help...

Answer 1

[Voss]

Use ./ instead of /

Signal_Attenuation = (signal_strength_-30) ./ d

Answer 2

[Paul]

Hi Gophela,

See below for probable error in calculation of Signal_Attenuation and correction.

clc;
clear all;
close all;
% strength of signal is inversely proportional to the distance between Tx
% and Rx
d= 0:1:10;

d = 1×11

0 1 2 3 4 5 6 7 8 9 10

signal_strength = (1)./(d*exp(2)); %  where d is  the distance between Tx and Rx
figure(1)
plot(d,signal_strength) % simple plot of signal strength vs distance between Tx and Rx
title('Signal Strength against Distance of Transmission')
ylabel('Signal Strength(dBm)')
xlabel('Transmission Distance(kM)')

% signal strength equation
u = 4*pi*10*exp(-7); % constant 
c = 3000000; % speed of light in kM per second
P = 500; % power transmission assumed to be 5000 watts
signal_strength_ = sqrt((u*c*P)./(2*pi*d*exp(2)));
figure(2)
plot(d,signal_strength_)
title('Signal Strength against Distance of Transmission')
ylabel('Signal Strength(dBm)')
xlabel('Transmission Distance(kM)')

Inputs to the Signal_Attenuation compuationg are both 1 x 11

% Signal Attenuation Plot
signal_strength

signal_strength = 1×11

Inf 0.1353 0.0677 0.0451 0.0338 0.0271 0.0226 0.0193 0.0169 0.0150 0.0135

d

d = 1×11

0 1 2 3 4 5 6 7 8 9 10

Using the mrdivide, / operator results in a scalar NaN, I doubt this is the desired result.

Signal_Attenuation = ((signal_strength_-30) / d)

Signal_Attenuation = NaN

Insatead, use element-wise division with the ./ operator, see rdivide, ./

Signal_Attenuation = ((signal_strength_-30) ./ d)

Signal_Attenuation = 1×11

1.0e+03 * Inf 1.8941 0.6653 0.3603 0.2330 0.1661 0.1259 0.0996 0.0813 0.0679 0.0578

figure(3)
plot(d,Signal_Attenuation)
title('Signal Attenuation vs Distance')
ylabel('Signal Attenuation(dB)')
xlabel('Tx to Rx Distance(kM)')

[Gophela Seiphepi]

thank you it worked