%  Envelope of two signals resulting from propagation over flat earth
% figure 6.3

x = 0:.01:4*pi;
figure;
for j=1:3
    R=.3+(j-1)*.3
    X=1+R*cos(x);
    Y=R*sin(x);
env=sqrt(X.^2+Y.^2);
plot(x,env,'k')
hold on
end
hold off
xlabel('(2kh_1h_2)/d')
ylabel('Envelope')
axis([0 12 0 2])
grid on
figure
for j=1:3
    R=.3+(j-1)*.3
    X=1+R*cos(x);
    Y=R*sin(x);
phaz=atan2(Y,X);
plot(x,phaz*180/pi,'k')
hold on
end
hold off
xlabel('(2kh_1h_2)/d')
ylabel('Phase')
axis([0 12 -90 90])
grid on