CORDIC算法的matlab实现

大笨象

9 H5 B: P& S( \7 t6 z
# k! N9 j+ L2 u9 t不知道有木有人研究这个，比较偏向于硬件描述。
" _7 l: v1 l( C今天先发一个sine cose函数的实现。
有兴趣的可以看一下，m文件见附件。
function v=f_cordic(beta,n)
5 P/ R) @4 ?' D9 xif beta < -pi/2 || beta > pi/2
    if beta < 0
1 ^$ |; p- @2 p& S3 j3 ^. {        v=f_cordic(beta + pi,n);
/ t7 r3 o8 v+ f  h    else
( B/ I3 H- H9 F7 m6 F        v=f_cordic(beta - pi,n);
    end
    v = -v;% flip the sign for second or third quadrant
    return
end
% Initialization of tables of constants used by CORDIC
% need a table of arctangents of negative powers of two, in radians:
" e  I8 T, S0 M/ o6 Z% angles = atan(2.^-(0:27));
angles =  [  ...
  J4 F$ j5 }0 q3 c3 f+ e    0.78539816339745   0.46364760900081   0.24497866312686   0.12435499454676 ...
    0.06241880999596   0.03123983343027   0.01562372862048   0.00781234106010 ...
    0.00390623013197   0.00195312251648   0.00097656218956   0.00048828121119 ...
    0.00024414062015   0.00012207031189   0.00006103515617   0.00003051757812 ...
2 s5 a4 M! z, z+ V$ ^/ O    0.00001525878906   0.00000762939453   0.00000381469727   0.00000190734863 ...
3 O" T7 T+ d- ^' M% |* c3 _    0.00000095367432   0.00000047683716   0.00000023841858   0.00000011920929 ...
% b& U5 w. I4 x# ?    0.00000005960464   0.00000002980232   0.00000001490116   0.00000000745058 ];
% and a table of products of reciprocal lengths of vectors [1, 2^-j]:
% E- h" Q6 H: h" qKvalues = [ ...
! d7 D) L$ {+ L    0.70710678118655   0.63245553203368   0.61357199107790   0.60883391251775 ...
    0.60764825625617   0.60735177014130   0.60727764409353   0.60725911229889 ...
    0.60725447933256   0.60725332108988   0.60725303152913   0.60725295913894 ...
    0.60725294104140   0.60725293651701   0.60725293538591   0.60725293510314 ...
    0.60725293503245   0.60725293501477   0.60725293501035   0.60725293500925 ...
, H, k/ \- Q+ s# P* s' r% ^    0.60725293500897   0.60725293500890   0.60725293500889   0.60725293500888 ];
2 Q9 `/ O% c* G( {- k0 OKn = Kvalues(min(n, length(Kvalues)));
$ z3 C: V. H) z- w$ v9 R2 B* p
) m. g) X6 N# i5 U% Initialize loop variables:
v = [1;0]; % start with 2-vector cosine and sine of zero
poweroftwo = 1;
% Iterations
for j = 1:n;
    if beta < 0
1 h' k  n/ F1 f& u+ `        sigma = -1;
) G! W9 h' G" x+ V; \! U9 u    else
        sigma = 1;
    end
    % update the angle from table, or eventually by just dividing by two
6 J. h2 F& q1 t/ x2 H* }- P# u# M/ C    if j <= length(angles)
        angle = angles(j);
' s6 X) N) D: g1 S- \# ~6 J    else
        angle = angle/2;
    end
+ N- P# b: m5 v) J) A    factor = sigma * poweroftwo;
8 T/ r, K* Q9 i+ Z    R = [1, -factor; factor, 1];
    v = R * v; % 2-by-2 mtrix multiply
) r: a( o2 x* e6 b/ f; z1 P    beta = beta - sigma * angle; % update the remaining angle
    poweroftwo = poweroftwo / 2;
end
0 h! g. `( V( w  A4 X% Adjust length of output vector to be [cos(beta), sin(beta)]:
v = v * Kn;
$ Y8 i8 `3 e6 z4 N  F4 xreturn

  G) q: ^5 Q& I) J使用20位寄存器，仿真波形如下：
# w- R3 C8 l, W& p5 ^& `9 H

杨帆

我表示学习了

zhangjichang

这是什么算法？第一次听说

赛才

我表示很给力

大笨象

zhangjichang 发表于 2011-6-8 22:31
7 r, }3 }1 \$ M2 y这是什么算法？第一次听说

这个，就是那个。感兴趣的话你还是自己搜搜吧。

大笨象

赛才 发表于 2011-6-9 15:01
/ e( S4 |) \" E% |% d我表示很给力

9 ?3 ^, k5 P% d, W4 Y给力就好。呵呵

魅影骑士

顶一下！

yingzhen

费解。。。。。。。。。。。。。。。。

羅雲琦

有什麽用？求解

jt202010