pd_swerling3.m
上传用户:szahd2008
上传日期:2020-09-25
资源大小:1275k
文件大小:1k
- function pd = pd_swerling3 (nfa, np, snrbar)
- % This function is used to calculate the probability of detection
- % for Swerling 2 targets.
- format long
- snrbar = 10.0^(snrbar/10.);
- eps = 0.00000001;
- delmax = .00001;
- delta =10000.;
- % Calculate the threshold Vt
- pfa = np * log(2) / nfa;
- sqrtpfa = sqrt(-log10(pfa));
- sqrtnp = sqrt(np);
- vt0 = np - sqrtnp + 2.3 * sqrtpfa * (sqrtpfa + sqrtnp - 1.0);
- vt = vt0;
- while (abs(delta) >= vt0)
- igf = incomplete_gamma(vt0,np);
- num = 0.5^(np/nfa) - igf;
- temp = (np-1) * log(vt0+eps) - vt0 - factor(np-1);
- deno = exp(temp);
- vt = vt0 + (num / (deno+eps));
- delta = abs(vt - vt0) * 10000.0;
- vt0 = vt;
- end
- temp1 = vt / (1.0 + 0.5 * np *snrbar);
- temp2 = 1.0 + 2.0 / (np * snrbar);
- temp3 = 2.0 * (np - 2.0) / (np * snrbar);
- ko = exp(-temp1) * temp2^(np-2.) * (1.0 + temp1 - temp3);
- if (np <= 2)
- pd = ko;
- return
- else
- temp4 = vt^(np-1.) * exp(-vt) / (temp1 * exp(factor(np-2.)));
- temp5 = vt / (1.0 + 2.0 / (np *snrbar));
- pd = temp4 + 1.0 - incomplete_gamma(vt,np-1.) + ko * ...
- incomplete_gamma(temp5,np-1.);
- end
- return