CORDIC算法的matlab实现

大笨象

* x+ S! V8 T+ M, |
" \8 x5 ?  x: @3 C' _) Z/ O不知道有木有人研究这个，比较偏向于硬件描述。
0 F7 c/ f7 m+ ]; _+ e今天先发一个sine cose函数的实现。
4 }- a$ x3 @  d6 h有兴趣的可以看一下，m文件见附件。
function v=f_cordic(beta,n)
if beta < -pi/2 || beta > pi/2
3 a+ x- l: X& r5 J7 a4 A- B8 s    if beta < 0
. M6 N- E) E8 {        v=f_cordic(beta + pi,n);
    else
        v=f_cordic(beta - pi,n);
) _" `; O% ~& |0 @  V: f& S    end
    v = -v;% flip the sign for second or third quadrant
    return
: h9 ^  B* p0 ^  A, Dend
4 O- X* }; u2 Y: z! ~- ]" M. o% Initialization of tables of constants used by CORDIC
% need a table of arctangents of negative powers of two, in radians:
2 X- ^9 j; o% L& ^9 \3 K% angles = atan(2.^-(0:27));
% f1 t" x* C! d5 v$ |angles =  [  ...
! w7 ?5 r4 v$ Z5 [( J- G, K    0.78539816339745   0.46364760900081   0.24497866312686   0.12435499454676 ...
    0.06241880999596   0.03123983343027   0.01562372862048   0.00781234106010 ...
4 \: m  C! @2 a( T! a: p1 D    0.00390623013197   0.00195312251648   0.00097656218956   0.00048828121119 ...
    0.00024414062015   0.00012207031189   0.00006103515617   0.00003051757812 ...
" y) V# V% D+ t, y' f2 K& x    0.00001525878906   0.00000762939453   0.00000381469727   0.00000190734863 ...
( L; j) J3 i) z$ F7 [    0.00000095367432   0.00000047683716   0.00000023841858   0.00000011920929 ...
% |9 `5 H. z4 Z# ?    0.00000005960464   0.00000002980232   0.00000001490116   0.00000000745058 ];
. V. T* h3 r1 L% and a table of products of reciprocal lengths of vectors [1, 2^-j]:
Kvalues = [ ...
" D' j& f( l9 L    0.70710678118655   0.63245553203368   0.61357199107790   0.60883391251775 ...
" p$ p4 g% B. q4 E    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 ...
    0.60725293500897   0.60725293500890   0.60725293500889   0.60725293500888 ];
* u  F. b: K$ Q) e0 C. l! @5 qKn = Kvalues(min(n, length(Kvalues)));

8 R3 G, B; A: l* }3 c% Initialize loop variables:
0 B/ d, U; X/ I! j# n) P" D/ Tv = [1;0]; % start with 2-vector cosine and sine of zero
' q* z$ o7 ~* g# i1 _  Ipoweroftwo = 1;
, y7 `8 W" V' D) x+ c% Iterations
for j = 1:n;
    if beta < 0
7 R! U; Z5 e. Q; E        sigma = -1;
* T' L8 H& f6 J# `3 X    else
5 E! J$ r9 t/ o- W/ n7 H        sigma = 1;
2 c0 m1 N! ]$ y- ~- z7 A7 @0 p    end
    % update the angle from table, or eventually by just dividing by two
% P+ I6 O. k- T  R2 a! W    if j <= length(angles)
        angle = angles(j);
- h1 C3 Z/ \3 r6 {  I    else
; g7 ?  b9 ~. @$ J( k* ?" R: x5 W        angle = angle/2;
1 _: Z/ n* X) w4 e3 O$ z/ G    end
    factor = sigma * poweroftwo;
; A+ z% m+ T4 I    R = [1, -factor; factor, 1];
0 W# g' _5 L4 k" i% [- x6 Y" L" {5 l    v = R * v; % 2-by-2 mtrix multiply
    beta = beta - sigma * angle; % update the remaining angle
7 [/ @2 I8 D% a: t' d$ l0 J/ ^    poweroftwo = poweroftwo / 2;
end
% Adjust length of output vector to be [cos(beta), sin(beta)]:
v = v * Kn;
return

使用20位寄存器，仿真波形如下：
7 W1 z8 k. @+ }
+ P( D' F  Z' ?' ^' }9 o9 {

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
这是什么算法？第一次听说

1 }3 ~& X: ?% z0 G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
/ ^* y- ]. `: h3 q' i/ d; C4 V我表示很给力

6 a& o! b; g; Z, W. j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