zdB = 0:50;							% predetection SNR in dB
z = 10.^(zdB/10);					% predetection SNR
beta = [1 5 10 20];				% modulation index vector
hold on								% hold for plots
for j=1:length(beta)
   bta = beta(j);   					% current index
	a1 = exp(-(0.5/(bta+1)*z));	% temporary constant	
	a2 = qfn(sqrt(z/(bta+1)));		% tempory constant
	num = (1.5*bta*bta)*z;
	den = 1+(4*sqrt(3)*(bta+1))*(z.*a2)+(12/pi)*bta*(z.*a1);
	result = num./den;
	resultdB = 10*log10(result);
	plot(zdB,resultdB,'k')
end
hold off
xlabel('Predetection SNR in dB')
ylabel('Postdetection SNR in dB')