function y = cir_to_bler(cs,x)

%valid from 3dB to 27dB

if (cs==1)

  p1 = -2.9687e-005;
  p2 = 0.00064926;
  p3 = 0.0024331;
  p4 = -0.13418;
  p5 = 0.75881;
  
  y = p1*x^4 + p2*x^3 + p3*x^2 + p4*x^1 + p5;

 
end

if (cs==2) 

  p1 = -2.6381e-006;
  p2 = 0.00011105;
  p3 = 0.00060427;
  p4 = -0.07636;
  p5 = 0.83198;
 y = p1.*x.^4 + p2.*x.^3 + p3.*x.^2 + p4.*x.^1 + p5; 
   
end

if (cs==3)
    
  p1 = -6.2246e-006;
  p2 = 0.00035063;
  p3 = -0.0045221;
  p4 = -0.046837;
  p5 = 0.96087;
y = p1.*x.^4 + p2.*x.^3 + p3.*x.^2 + p4.*x.^1 + p5; 

end

if (cs==4) 
    
  p1 = -8.3854e-006;
  p2 = 0.00054796;
  p3 = -0.010585;
  p4 = 0.020171;
  p5 = 0.84776;
y = p1.*x.^4 + p2.*x.^3 + p3.*x.^2 + p4.*x.^1 + p5; 

end

  index=find(x<2);
  y(index)=1;


  index=find(x>27);
  y(index)=0;