📄 routine.c
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void Bit_Reverse( int BR_Array[] )
{
unsigned char swapA,swapB,sw_cnt ;
int TempStore ;
for(sw_cnt =1 ;sw_cnt <NUM_FFT/2 ;sw_cnt++ )
{
swapA = sw_cnt;
swapB = BRTable[sw_cnt]*2 ;
if( swapB>swapA )
{
TempStore =BR_Array[ swapA ] ;
BR_Array[ swapA ] = BR_Array[ swapB ] ;
BR_Array[ swapB ] = TempStore;
}
swapA += NUM_FFT/2 ;
swapB++ ;
if( swapB>swapA )
{
TempStore =BR_Array[ swapA ] ;
BR_Array[ swapA ] = BR_Array[ swapB ] ;
BR_Array[ swapB ] = TempStore;
}
}
}
//Int_FFT_A这个算法的循环和教科书上的有些不一样
//有L级运算 有group个蝴蝶运算 每个蝴蝶运算有stage个运算因子
//Int_FFT_A如果改为Int_FFT_B:有L级运算 ,有stage个运算因子 ,每个蝴蝶运算有有group个蝴蝶运算，这样会更加减少计算量
//因为因子的计算是查表进行的，用时很少，所以Int_FFT_B不会比Int_FFT_A快很多，没有必要进行改进了。
void Int_FFT_A(int ReArray[] , int ImArray[] )
{
unsigned char sin_index,g_cnt,s_cnt ;
unsigned char indexA,indexB ;
unsigned int group = NUM_FFT/4, stage = 2 ;
long CosVal,SinVal ;
long TempImA, TempImB, TempReA , TempReB , TempReA2 , TempReB2 ,TempImA2, TempImB2 ;
IBALONG ReTwid , ImTwid, TempL ;
indexA = 0 ;
for(g_cnt = 0 ; g_cnt < NUM_FFT/2 ; g_cnt++) //这里是第1层运算，只有一个因子 这个因子有NUM_FFT/2个蝴蝶运算
{
indexB = indexA + 1 ;
TempReA = ReArray[indexA] ;
TempReB = ReArray[indexB] ;
TempL.l = (long)TempReA + (long)TempReB ;
if( (TempL.l < 0 ) && ( 0x01 & TempL.b[0] ) )
TempReA2 = ( TempL.l >> 1 ) + 1 ;
else
TempReA2 = TempL.l >> 1 ;
TempL.l = (long)TempReA - (long)TempReB ;
if( (TempL.l < 0 ) && ( 0x01 & TempL.b[0] ) )
ReArray[indexB] = ( TempL.l >> 1 ) + 1 ;
else
ReArray[indexB] = TempL.l >> 1 ;
ReArray[indexA] = TempReA2 ;
ImArray[indexA] = 0;
ImArray[indexB] = 0;
indexA = indexB + 1 ;
}
while( stage <= NUM_FFT/2 )
{
indexA = 0 ;
sin_index = 0 ;
for(g_cnt = 0 ; g_cnt < group ; g_cnt++ )
{
for(s_cnt = 0 ; s_cnt < stage ; s_cnt++ )
{
indexB = indexA + stage ;
TempReA = ReArray[indexA] ;
TempReB = ReArray[indexB] ;
TempImA = ImArray[indexA] ;
TempImB = ImArray[indexB] ;
//计算
if(sin_index == 0) //旋转因子是0 系数是1
{
//计算rearray[indexa]
TempL.l = (long)TempReA + TempReB ;
if( (TempL.l < 0) && (0x01 & TempL.b[0]) )
TempReA2 = ( TempL.l >> 1 ) + 1 ;
else
TempReA2 = TempL.l >> 1 ;
//计算rearray[indexB]
TempL.l = (long)TempReA - TempReB ;
if( (TempL.l < 0) && (0x01 & TempL.b[0]) )
TempReB2 = ( TempL.l >> 1 ) + 1 ;
else
TempReB2 = TempL.l >> 1 ;
//计算IMarray[indexA]
TempL.l = (long)TempImA - TempImB ;
if( (TempL.l < 0) && (0x01 & TempL.b[0]) )
TempImA2 = ( TempL.l >> 1 ) + 1 ;
else
TempImA2 = TempL.l >> 1 ;
//计算IMarray[indexB]
TempL.l = (long)TempImA - TempImB ;
if( (TempL.l < 0) && (0x01 & TempL.b[0]) )
TempImB2 = ( TempL.l >> 1 ) + 1 ;
else
TempImB2 = TempL.l >> 1 ;
ReArray[indexA] = TempReA2 ;
ReArray[indexB] = TempReB2 ;
ImArray[indexA] = TempImA2 ;
ImArray[indexB] = TempImB2 ;
}
else if( sin_index == NUM_FFT/4) //旋转因子是pi/2 系数是-i
{
//计算rearray[indexa]
TempL.l = (long)TempReA + TempImB ;
if( (TempL.l < 0) && (0x01 & TempL.b[0]) )
TempReA2 = ( TempL.l >> 1 ) + 1 ;
else
TempReA2 = TempL.l >> 1 ;
//计算Imarray[indexa]
TempL.l = (long)TempImA - TempReB ;
if( (TempL.l < 0) && (0x01 & TempL.b[0]) )
TempImA2 = ( TempL.l >> 1 ) + 1 ;
else
TempImA2 = TempL.l >> 1 ;
//计算rearray[indexb]
TempL.l = (long)TempReA - TempImB ;
if( (TempL.l < 0) && (0x01 & TempL.b[0]) )
TempReB2 = ( TempL.l >> 1 ) + 1 ;
else
TempReB2 = TempL.l >> 1 ;
//计算Imarray[indexb]
TempL.l = (long)TempImA + TempReB ;
if( (TempL.l < 0) && (0x01 & TempL.b[0]) )
TempImB2 = ( TempL.l >> 1 ) + 1 ;
else
TempImB2 = TempL.l >> 1 ;
ReArray[indexA] = TempReA2 ;
ReArray[indexB] = TempReB2 ;
ImArray[indexA] = TempImA2 ;
ImArray[indexB] = TempImB2 ;
}
else //旋转因子不是任何特殊值
{
if(sin_index > NUM_FFT/4)
{
SinVal = SinTable[(NUM_FFT/2) - sin_index] ;
CosVal = -SinTable[sin_index - (NUM_FFT/4)];
}
else
{
SinVal = SinTable[sin_index] ;
CosVal = SinTable[(NUM_FFT/4)-sin_index ];
}
ReTwid.l = ((long)TempReB * CosVal) +
((long)TempImB * SinVal) ;
ImTwid.l = ((long)TempImB * CosVal) -
((long)TempReB * SinVal) ;
//计算rearray[indexa]
TempL.i[0] = 0 ;
TempL.i[1] = TempReA ;
TempL.l = TempL.l >> 1;
TempL.l += ReTwid.l ;
if((TempL.l < 0) && (TempL.i[0]))
TempReA2 = TempL.i[1] + 1 ;
else
TempReA2 = TempL.i[1] ;
//计算IMarray[indexa]
TempL.i[0] = 0 ;
TempL.i[1] = TempImA ;
TempL.l = TempL.l >> 1;
TempL.l += ImTwid.l ;
if((TempL.l < 0) && (TempL.i[0]))
TempImA2 = TempL.i[1] + 1 ;
else
TempImA2 = TempL.i[1] ;
//计算rearray[indexB]
TempL.i[0] = 0 ;
TempL.i[1] = TempReA ;
TempL.l = TempL.l >> 1;
TempL.l -= ReTwid.l ;
if((TempL.l < 0) && (TempL.i[0]))
TempReB2 = TempL.i[1] + 1 ;
else
TempReB2 = TempL.i[1] ;
//计算IMarray[indexB]
TempL.i[0] = 0 ;
TempL.i[1] = TempImA ;
TempL.l = TempL.l >> 1;
TempL.l -= ImTwid.l ;
if((TempL.l < 0) && (TempL.i[0]))
TempImB2 = TempL.i[1] + 1 ;
else
TempImB2 = TempL.i[1] ;
ReArray[indexA] = TempReA2 ;
ReArray[indexB] = TempReB2 ;
ImArray[indexA] = TempImA2 ;
ImArray[indexB] = TempImB2 ;
}
indexA++ ;
sin_index += group ;
}
indexA = indexB + 1 ;
sin_index = 0 ;
}
group /= 2 ; //代表每级运算中有几个蝴蝶运算
stage *= 2 ; //代表第几级运算
}
}
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