- Intital revision

git-svn-id: http://moon:8086/svn/vhdl/trunk@139 cc03376c-175c-47c8-b038-4cd826a8556b
2008-12-21 16:18:22 +00:00
parent 8e6affa627
commit 776094e4b2
24 changed files with 4752 additions and 0 deletions
@@ -0,0 +1,171 @@
+function eval_cordic(Nmax, doplot)
+N = 100;
+
+arctan_tbl = (atan(2.^-(0:N-1))/pi)'
+%gain_tbl = (1./cumprod(sqrt(1+2.^-(2*(0:N-1)))))'
+
+% Rotation mode
+disp('Rotation:')
+for i=1:N,
+    phi(i) = 2*pi*(i-N/2)/N;
+    [x(i),y(i)] = cordic_rot(0, 1, phi(i), Nmax, 0);
+end;
+close all;
+figure
+plot(1:N, x, 1:N, y);
+legend('x','y')
+grid;
+
+% Vector mode
+disp('Magnitude and phase:')
+for i=1:N,
+    [mag(i), phi(i)] = cordic_vec(x(i), y(i), Nmax, 0);
+end;
+figure
+plot(1:N, mag, 1:N, phi);
+legend('Magnitude','Phase')
+grid;
+
+
+% ------------------------------------------------------------
+function [mag, phi] = cordic_cart2polar(x, y, Nmax, doplot)
+    [mag, phi] = cordic_vec(x, y, Nmax, doplot);
+  
+% ------------------------------------------------------------
+function [x, y] = cordic_polar2cart(mag, phi, Nmax, doplot)
+    [mag, phi] = cordic_vec(x, y, Nmax, doplot);
+  
+% ------------------------------------------------------------
+function [xout, yout] = cordic_rot(xin, yin, phi, N, doplot)
+
+    % Initialize
+    arctan_tbl = atan(2.^-(0:N-1));
+    gain_tbl = 1./cumprod(sqrt(1+2.^-(2*(0:N-1))));
+
+    coeffs = arctan_tbl';
+    gains = gain_tbl';
+
+    % Calculate initial rotation
+    if (phi < (-pi/2))
+        z = phi + pi;
+        x = -xin;
+        y = -yin;
+    else
+        if (phi > pi/2)
+            z = phi - pi;
+            x = -xin;
+            y = -yin;
+        else
+            x = xin;
+            y = yin;
+            z = phi;
+        end;
+    end;
+
+    % Loop
+    for i=1:N,
+        xi(i) = x;
+        yi(i) = y;
+        zi(i) = z;
+    
+        S = 2^(-(i-1));
+        if (z < 0)
+			t = x + y*S;
+			y = y - x*S;
+			z = z + arctan_tbl(i);
+			x = t;
+        else
+			t = x - y*S;
+			y = y + x*S;
+			z = z - arctan_tbl(i);
+			x = t;
+        end;
+        
+    end;
+
+    % Result
+    k = gain_tbl(i);
+    xout = k*x;
+    yout = k*y;
+
+    % Output
+    if(doplot)
+        close all;
+        figure(1);
+        plot(1:N, xi, 1:N, yi, 1:N, zi)
+        legend('x','y','z');
+        title('Convergence');
+        grid;
+
+        figure(2);
+        plot(xi.*gain_tbl, yi.*gain_tbl, '-x')
+        title('Polar plot');
+        grid;
+    end;
+
+% ------------------------------------------------------------
+function [mag, phi] = cordic_vec(xin, yin, N, doplot)
+
+    % Initialize
+    arctan_tbl = atan(2.^-(0:N-1));
+    gain_tbl = 1./cumprod(sqrt(1+2.^-(2*(0:N-1))));
+
+    coeffs = arctan_tbl';
+    gains = gain_tbl';
+    
+    % Calculate initial rotation
+    if (xin < 0)
+        x = -xin;
+        y = -yin;
+        if (yin < 0)
+            z = -pi;
+        else
+            z = pi;
+        end;
+    else
+        x = xin;
+        y = yin;
+        z = 0;
+    end;
+  
+    % Loop
+    for i=1:N,
+        xi(i) = x;
+        yi(i) = y;
+        zi(i) = z;
+    
+        S = 2^(-(i-1));
+        if (y < 0)
+			t = x - y*S;
+			y = y + x*S;
+			z = z - arctan_tbl(i);
+			x = t;
+        else
+			t = x + y*S;
+			y = y - x*S;
+			z = z + arctan_tbl(i);
+			x = t;
+        end;
+        
+    end;
+
+    % Result
+    k = gain_tbl(i);
+    mag = k*x;
+    phi = z;
+    
+    % Output
+    if(doplot)
+        close all;
+        figure(1);
+        plot(1:N, xi, 1:N, yi, 1:N, zi)
+        legend('x','y','z');
+        title('Convergence');
+        grid;
+
+        figure(2);
+        plot(xi.*gain_tbl, yi.*gain_tbl, '-x')
+        title('Polar plot');
+        grid;
+    end;
+