chebylp.m

阵列信号处理的工具箱

function an=chebylp(nn,r0dB)

%CHEBYLP Calculates Dolhp-Chebychev weights.
%--------
%Synopsis:
%  an=chebylp(nn,r0dB)
%
%Description
%  Dolhp-Chebychev weights of an n-element array with sidelobes r0dB.
%  see C. Balanis "Antenna Theory", pp. 245-254.
%
%Output and Input:
%  nn (IntScalarT): Number of weight coefficients to produce.
%  r0dB (RealScalarT): Side lobe level in dB. This number is positive.
%
%--------
%Notations:
%  Data type names are shown in parentheses and they start with a capital
%  letter and end with a capital T. Data type definitions can be found in [1]
%  or by "help dbtdata".
%  [D] = This parameter can be omitted and then a default value is used.
%  When the [D]-input parameter is not the last used in the call, it must be
%  given the value [], i.e. an empty matrix.
%  ... = There can be more parameters. They are explained under respective
%  metod or choice.
%
%Examples:
%Software Quality:
%  (About what is done to ascertain software quality. What tests are done.)
%Known Bugs:
%
%References:
%  [1]: Bj鰎klund S.: "DBT, A MATLAB Toolbox for Radar Signal Processing.
%    Reference Guide", FOA-D--9x-00xxx-408--SE, To be published.
%
%See Also:
%  gettap1 taylorlp bartlett blackman* boxcar* chebwin* hamming* hanning* 
%  kaiser* triang*
%  (* = Part of Matlab Signal Processing Toolbox)

%   *  DBT, A Matlab Toolbox for Radar Signal Processing  *
% (c) FOA 1994-2000. See the file dbtright.m for copyright notice.
%
%  Start        : xxxxx Lars Pettersson (larpet).
%  Latest change: $Date: 2000/10/16 15:20:05 $ $Author: svabj $.
%  $Revision: 1.3 $
% *****************************************************************************


     an=zeros(1,nn);
     r0=10^(r0dB/20);
     if rem(nn,2)==0
       eo='evn';
       m=nn/2;
       msum=m;
     else
       eo='odd';
       m=(nn-1)/2;
       msum=m+1;
     end
		z0=cos(acos(r0)/(nn-1));
     for n=1:msum
       f1=(-1)^(msum-n);
       if strcmp(eo,'evn')
         f2=z0^(2*n-1);	
         f4=2*m-1;
       else
         f2=z0^(2*n-2);
         f4=2*m;
       end
       f3=1;
       for k=1:(m+n-2);
         f3=f3*k;
       end
       f5=1;
       f6=1;
       for k=1:(2*n-2)
         f6=f6*k;
       end
       if strcmp(eo,'evn')
         f6=f6*(2*n-1);
       end
       f7=1;
       for k=1:(msum-n)
         f7=f7*k;
       end
             a=f1*f2*f3*f4/(f5*f6*f7);
       for q=n+1:msum
         f1=-f1;
         f2=f2*z0^2;
         f3=f3*(m-2+q);
         f5=f5*(q-n);
         if eo=='evn'
           f6=f6*(q+n-1);
         else
           f6=f6*(q+n-2);
         end
         f7=f7/(msum-q+1);
             a=a+f1*f2*f3*f4/(f5*f6*f7);
       end
             an(m+n)=a;
             an(msum+1-n)=a;
     end