Computes the discrete Fourier transform for a given frequency for a single signal.
Syntax
IppStatus ippsGoertz_32f(const Ipp32f* pSrc, int len, Ipp32fc* pVal, Ipp32f rFreq);
IppStatus ippsGoertz_64f(const Ipp64f* pSrc, int len, Ipp64fc* pVal, Ipp64f rFreq);
IppStatus ippsGoertz_32fc(const Ipp32fc* pSrc, int len, Ipp32fc* pVal, Ipp32f rFreq);
IppStatus ippsGoertz_64fc(const Ipp64fc* pSrc, int len, Ipp64fc* pVal, Ipp64f rFreq);
IppStatus ippsGoertz_16s_Sfs(const Ipp16s* pSrc, int len, Ipp16sc* pVal, Ipp32f rFreq, int scaleFactor);
IppStatus ippsGoertz_16sc_Sfs(const Ipp16sc* pSrc, int len, Ipp16sc* pVal, Ipp32f rFreq, int scaleFactor);
IppStatus ippsGoertzQ15_16sc_Sfs(const Ipp16sc* pSrc, int len, Ipp16sc* pVal, Ipp16s rFreqQ15, int scaleFactor);
Parameters
pSrc |
Pointer to the input data vector. |
len |
Number of elements in the vector. |
pVal |
Pointer to the output DFT value. |
rFreq |
Single relative frequency value [0, 1.0). |
rFreqQ15 |
Single relative frequency value in Q15 format [0, 32767]. |
scaleFactor |
Scale factor, refer to Integer Scaling. |
Description
The function ippsGoertz is declared in the ipps.h file. This function computes a DFT for an input len-length vector pSrc for a given frequency rFreq, and stores the result in pVal.
ippsGoertzQ15. This function operates with relative frequency in Q15 format. Data in Q15 format are converted to the corresponding float data type that lay in the range [0, 1.0).
The functionality of the Goertzel algorithm can be described as follows:
where k/N is the normalized rFreq value for which the DFT is computed.
Example below illustrates the use of Goertzel functions for selecting the magnitudes of a given frequency when computing DFTs.
Return Values
ippStsNoErr |
Indicates no error. |
ippStsNullPtrErr |
Indicates an error when one of the specified pointers is NULL. |
ippStsRelFreqErr |
Indicates an error when rFreq is out of range. |
ippStsSizeErr |
Indicates an error when len is less than or equal to 0. |
Using Goertzel Functions for Selecting Magnitudes of a Given Frequency
IppStatus
goertzel( void ) {
#undef LEN
#define LEN 100
IppStatus status;
Ipp32fc *x = ippsMalloc_32fc( LEN ), y;
int n;
///generate a signal of 60 Hz freq that
/// is sampled with 400 Hz freq
for( n=0; n<LEN; ++n) {
x[n].re =(Ipp32f)sin(IPP_2PI * n * 60 / 400);
x[n].im = 0;
}
status = ippsGoertz_32fc( x, LEN, &y, 60.0f / 400 );
printf_32fc("goertz =", &y, 1, status );
ippsFree( x );
return status;
}
Output:
goertz = {0.000090,-50.000008}
Matlab* Analog
>> N=100;F=60/400;n=0:N-1;x=sin(2*pi*n*F);y=fft(x);n=N*F;y(n+1)