rect_array.m
上传用户:szahd2008
上传日期:2020-09-25
资源大小:1275k
文件大小:5k
- function [pattern] = rect_array(Nxr,Nyr,dolxr,dolyr,theta0,phi0,winid,win,nbits);
- %%%%%%%%%%%%%%%%%%%% ************************ %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
- % This function computes the 3-D directive gain patterns for a plannar array
- % This function uses the fft2 to compute its output
- %%%%%%%%%%%%%%%%%%%% ************ INPUTS ************ %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
- % Nxr ==> number of along x-aixs; Nyr ==> number of elemnts along y-axis
- % dolxr ==> element spacing in x-direction; dolyr ==> element spacing in y-direction Both are in lambda units
- % theta0 ==> elevation steering angle in degrees, phi0 ==> azimuth steering angle in degrees
- % winid ==> window identifier; winid negative ==> no window ; winid positive ==> use window given by win
- % win ==> input window function (2-D window) MUST be of size (Nxr X Nyr)
- % nbits is the number of nbits used in phase quantization; nbits negative ==> NO quantization
- %%%%%%%%%%%%%%%%%%%% *********** OUTPUTS ************* %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
- % pattern ==> directive gain pattern
- %%%%%%%%%%%%%%%%%%%% ************************ %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
- eps = 0.0001;
- nx = 0:Nxr-1;
- ny = 0:Nyr-1;
- i = sqrt(-1);
- % check that window size is the same as the array size
- [nw,mw] = size(win);
- if winid >0
- if nw ~= Nxr
- fprintf('STOP == Window size must be the same as the array')
- return
- end
- if mw ~= Nyr
- fprintf('STOP == Window size must be the same as the array')
- return
- end
- end
- %if dol is > 0.5 then; choose dol = 0.5 and compute new N
- if(dolxr <=0.5)
- ratiox = 1 ;
- dolx = dolxr ;
- Nx = Nxr ;
- else
- ratiox = ceil(dolxr/.5) ;
- Nx = (Nxr -1 ) * ratiox + 1 ;
- dolx = 0.5 ;
- end
- if(dolyr <=0.5)
- ratioy = 1 ;
- doly = dolyr ;
- Ny = Nyr ;
- else
- ratioy = ceil(dolyr/.5) ;
- Ny = (Nyr -1) * ratioy + 1 ;
- doly = 0.5 ;
- end
- % choose proper size fft, for minimum value choose 256X256
- Nrx = 10 * Nx;
- Nry = 10 * Ny;
- nfftx = 2^(ceil(log(Nrx)/log(2)));
- nffty = 2^(ceil(log(Nry)/log(2)));
- if nfftx < 256
- nfftx = 256;
- end
- if nffty < 256
- nffty = 256;
- end
- % generate array of elements with or without window
- if winid < 0
- array = ones(Nxr,Nyr);
- else
- array = win;
- end
- % convert steering angles (theta0, phi0) to radians
- theta0 = theta0 * pi / 180;
- phi0 = phi0 * pi / 180;
- % convert steering angles (theta0, phi0) to U-V sine-space
- u0 = sin(theta0) * cos(phi0);
- v0 = sin(theta0) * sin(phi0);
- % Use formula thetal = (2*pi*n*dol) * sin(theta0) divided into 2^m levels
- % and rounded to the nearest qunatization level
- if nbits < 0
- phasem = exp(i*2*pi*dolx*u0 .* nx *ratiox);
- phasen = exp(i*2*pi*doly*v0 .* ny *ratioy);
- else
- levels = 2^nbits;
- qlevels = 2.0*pi / levels; % compute quantization levels
- sinthetaq = round(dolx .* nx * u0 * levels * ratiox) .* qlevels; % vector of possible angles
- sinphiq = round(doly .* ny * v0 * levels *ratioy) .* qlevels; % vector of possible angles
- phasem = exp(i*sinthetaq);
- phasen = exp(i*sinphiq);
- end
-
- % add the phase shift terms
- array = array .* (transpose(phasem) * phasen);
-
- % determine if interpolation is needed (i.e N > Nr)
- if (Nx > Nxr )| (Ny > Nyr)
- for xloop = 1 : Nxr
- temprow = array(xloop, :) ;
- w( (xloop-1)*ratiox+1, 1:ratioy:Ny) = temprow ;
- end
- array = w;
- else
- w = array ;
- % w(1:Nx, :) = array(1:N,:);
- end
- % Compute array pattern
- arrayfft = abs(fftshift(fft2(w,nfftx,nffty))).^2 ;
- %compute [su,sv] matrix
- U = [-nfftx/2:(nfftx/2)-1] ./(dolx*nfftx);
- indexx = find(abs(U) <= 1);
- U = U(indexx);
- V = [-nffty/2:(nffty/2)-1] ./(doly*nffty);
- indexy = find(abs(V) <= 1);
- V = V(indexy);
- %Normalize to generate gain patern
- rbar=sum(sum(arrayfft(indexx,indexy))) / dolx/doly/4./nfftx/nffty;
- arrayfft = arrayfft(indexx,indexy) ./rbar;
- [SU,SV] = meshgrid(V,U);
- indx = find((SU.^2 + SV.^2) >1);
- arrayfft(indx) = eps/10;
- pattern = 10*log10(arrayfft +eps);
- figure(1)
- mesh(V,U,pattern);
- xlabel('V')
- ylabel('U');
- zlabel('Gain pattern - dB')
- figure(2)
- contour(V,U,pattern)
- grid
- axis image
- xlabel('V')
- ylabel('U');
- axis([-1 1 -1 1])
- figure(3)
- x0 = (Nx+1)/2 ;
- y0 = (Ny+1)/2 ;
- radiusx = dolx*((Nx-1)/2) ;
- radiusy = doly*((Ny-1)/2) ;
- [xxx, yyy]=find(abs(array)>eps);
- xxx = xxx-x0 ;
- yyy = yyy-y0 ;
- plot(yyy*doly, xxx*dolx,'rx')
- hold on
- axis([-radiusy-0.5 radiusy+0.5 -radiusx-0.5 radiusx+0.5]);
- grid
- title('antenna spacing pattern');
- xlabel('y - lambda units')
- ylabel('x - lambda units')
- [xxx0, yyy0]=find(abs(array)<=eps);
- xxx0 = xxx0-x0 ;
- yyy0 = yyy0-y0 ;
- plot(yyy0*doly, xxx0*dolx,'co')
- axis([-radiusy-0.5 radiusy+0.5 -radiusx-0.5 radiusx+0.5]);
- hold off
- return