Question

electromagnatic wave of loop antenna in matlab

Answer 1

% ab.m - dB to absolute units
%
% Usage: Gab = ab(Gdb)   
%
% Gdb = power gain in dB
% Gab = power gain in absolute units, Gab = 10^(Gdb/10)
%
% see also Gdb = db(Gab) for the reverse operation
function Gab = ab(Gdb)

if nargin==0, help ab; return; end

Gab = 10.^(Gdb/10);

clear all
set(0,'DefaultAxesFontSize',26);
set(0,'DefaultTextFontSize',26);
set(0,'DefaultAxesLineWidth',1.5);
set(0,'DefaultLineLineWidth',2);
set(0,'DefaultAxesFontName','Arial');
%
mu0 = 4*pi*1e-7; % permeability of air (H/m)
c_light = 2.9979*10^8; % speed of light (m/s)
vc = 0.67; % velocity factor = velocity inside the cable wrt speed of light RG223/U; see paper
%
%% INPUT PARAMETERS
Fstart = 9*10^3; % start frequency
Fstop = 30*10^6; % stop frequency
%f = linspace(Fstart,Fstop,50); % number of frequency points
f = [Fstart linspace(10^4, 9*10^4,9) linspace(10^5, 9*10^5,9) linspace(10^6, Fstop, 30) ]; % number of frequency points
w = 2*pi*f; % Frequency (radians/sec)
lambda = c_light./f; % wavelength (m)
k = 2*pi./lambda; % wavenumber in free space
kc = k./vc; % wavenumber in material
%
% transmit antenna
I_mdip_dB = 100; % current magnetic dipole (dBuA)
I_mdip = 10^(I_mdip_dB/20); % current in the transmit antenna (uA)
D_mdip = 0.4; % diameter of the transmit loop antenna (m)
S_mdip = pi*(D_mdip/2)^2; % surface of the transmit loop antenna (m2)
M_mdip = I_mdip * S_mdip; % mangetic dipole moment (uAm2)
%
%% LLA PARAMETERS
%d_lla = 0.0054; % diameter central conductor coaxial cable LLA = RG223/U (m)
d_lla = 3.96*10^-3; % diameter central conductor coaxial cable LLA = RG223/U (m); ref page 867 [1]
Rc = 50; % Rc characteristic impedance coaxial LAS cable (Ohm)
Rt = 50; % termination resistance LAS cable (Ohm)
%
%% CALCULATION CURRENT IN THE LLA FOR DIFFERENT LLA DIAMETERS
I_lla_1m = iLAS(f,I_mdip,S_mdip,1); % for diameter = 1 m
I_lla_magn_db_1m = db(abs(I_lla_1m));
%
I_lla_15m = iLAS(f,I_mdip,S_mdip,1.5); % for diameter = 1.5 m
I_lla_magn_db_15m = db(abs(I_lla_15m));
%
I_lla_2m = iLAS(f,I_mdip,S_mdip,2); % for diameter = 2 m
I_lla_magn_db_2m = db(abs(I_lla_2m));
%
I_lla_3m = iLAS(f,I_mdip,S_mdip,3); % for diameter = 3 m
I_lla_magn_db_3m = db(abs(I_lla_3m));
%
I_lla_4m = iLAS(f,I_mdip,S_mdip,4); % for diameter = 4 m
I_lla_magn_db_4m = db(abs(I_lla_4m));
%
%% CALCULATION CONVERSION FACTORS FOR DIFFERENT LLA DIAMETERS
C_LAS_1to2 = I_lla_magn_db_1m - I_lla_magn_db_2m;
C_LAS_15to2 = I_lla_magn_db_15m - I_lla_magn_db_2m;
C_LAS_2to2 = I_lla_magn_db_2m - I_lla_magn_db_2m;
C_LAS_3to2 = I_lla_magn_db_3m - I_lla_magn_db_2m;
C_LAS_4to2 = I_lla_magn_db_4m - I_lla_magn_db_2m;
%
%% PLOTTING RESULTS
%
% Plot of relative sensititivity for different loop diameters: Figure C.11 of CISPR 16-1-4 [3]
figure
semilogx(f,C_LAS_1to2,'b',f,C_LAS_15to2,'g',f,C_LAS_2to2,'k',f,C_LAS_3to2,'r',f,C_LAS_4to2,'m'); hold on;
title('Sensitivity of a large-loop antenna with different diameters relative to a 2 m LLA')
xlabel('Frequency (MHz)')
set(gca,'XTick',1e6*[0.01 0.02 0.05 0.1 0.2 0.5 1 2 5 10 20 30]);
set(gca,'XTickLabel',{'0,01','0,02','0,05','0,1','0,2','0,5','1','2','5','10','20','30'});
ylabel('Relative sensitivity (dB)')
%legend('1 m','1,5 m','2 m','3 m','4 m','Location','Northwest')
xt = [10^5 10^5 10^5 10^5 10^5];
yt = [12 6.5 1 -6.5 -11.5];
str = {'1 m','1,5 m','2 m','3 m','4 m'};
text(xt,yt,str)
axis([Fstart Fstop -15 15])
hold off;
grid
%grid minor
%
%% PRINT TABULAR RESULTS OF THE RELATIVE SENSITIVITY
fprintf('\nSENSITIVITY RELATIVE TO THE 2 M LAS\n');
fprintf('Freq\tC_LAS_1to2\tC_LAS_1.5to2\tC_LAS_3to2\tC_LAS_4to2\n');
fprintf('(MHz)\t(dB)\t\t(dB)\t\t(dB)\t\t(dB)\n');
for iprnt = 1: length(f)
fprintf('%3.3f\t%3.2f\t\t%3.2f\t\t%3.2f\t\t%3.2f\n',f(iprnt)/10^6,C_LAS_1to2(iprnt),C_LAS_15to2(iprnt),C_LAS_3to2(iprnt),C_LAS_4to2(iprnt));
end;
%%