Re: [Help-gsl] Re: FFT(INVFFT) is not returning original data!

[James Bergstra]

I didn't run your code, but is the difference simply a matter of
scaling?  There is some discussion of this in the documentation.

On Mon, Jan 11, 2010 at 4:54 AM, Sumit Adhikari
<address@hidden> wrote:
> A small correction ... "not returning"
> Sorry for the inconvenience.
>
>
> On Mon, Jan 11, 2010 at 3:22 PM, Sumit Adhikari <address@hidden>wrote:
>
>> Hello All,
>>   Following function is returning me the original data. Can anybody please
>> tell me what is the problem I am doing with it ?
>>
>>
>> # ifndef SC_FFT_H
>> # define SC_FFT_H
>>
>> # include <cmath>
>>
>> # include "systemc.h"
>>
>> # include "m_signal_inout_if.h"
>> # include "m_signal_in_if.h"
>>
>>
>> # include <gsl/gsl_errno.h>
>> # include <gsl/gsl_fft_complex.h>
>>
>> # include "hann.h"
>>
>>
>> # define REAL(z,i) ((z) [2*(i)])
>> # define IMAG(z,i) ((z) [2*(i) + 1])
>>
>> template < typename T > class sc_fft : public sc_module {
>> public :
>>    sc_port < m_signal_in_if < T > >          inp ;
>>    sc_port < m_signal_inout_if < T > >       out ;
>>    sc_port < m_signal_inout_if < bool > >    tx  ;
>>    sc_port < m_signal_inout_if < T > >       freq;
>>
>>
>>    typedef sc_fft SC_CURRENT_USER_MODULE ;
>>
>>    sc_fft(sc_module_name name,const unsigned Nfft,T Offset):
>>       inp("inp"),
>>       out("out"),
>>       tx("tx"),
>>       freq("freq"),
>>       sc_module(name),
>>       _Nfft(Nfft) ,
>>       _Offset(Offset) {
>>
>>          Npoints = _Nfft ;
>>
>>          i = 0 ;
>>
>>          fft_inp_buff = (double*) malloc (_Nfft * sizeof(double));
>>          fft_inp_buff = new double [_Nfft] ;
>>
>>          fft_trn_buff = (double*) malloc (2*_Nfft * sizeof(double));
>>          fft_trn_buff = new double [2*_Nfft] ;
>>
>>          fft_out_buff = (double*) malloc (_Nfft * sizeof(double));
>>          fft_out_buff = new double [_Nfft] ;
>>
>>
>>          SC_METHOD(read);
>>          sensitive << inp ;
>>       }
>>
>>
>> private :
>>    const unsigned       _Nfft          ;
>>    T                    _Offset        ;
>>    unsigned             Npoints        ;
>>    unsigned             i              ;
>>    double*              fft_inp_buff   ;
>>    double*              fft_trn_buff   ;
>>    double*              fft_out_buff ;
>>
>>
>>    void inline read(){
>>       if (i == (Npoints - 1)) {
>>          i = 0 ;
>>
>>          for(int j = 0 ; j < Npoints ; j++) {
>>             REAL(fft_trn_buff,j) = fft_inp_buff[j];
>>             IMAG(fft_trn_buff,j) = 0.0 ;
>>          }
>>
>>          int fstatus =
>> gsl_fft_complex_radix2_forward(fft_trn_buff,1,Npoints);
>>          int rstatus =
>> gsl_fft_complex_radix2_inverse(fft_trn_buff,1,Npoints);
>>          for(int j = 0 ; j < Npoints ; j++) fft_out_buff[j] =
>> sqrt(REAL(fft_trn_buff,j)*REAL(fft_trn_buff,j) +
>> IMAG(fft_trn_buff,j)*IMAG(fft_trn_buff,j)) ;
>>
>>
>>          fft_inp_buff[i] = (double) (inp->read() - _Offset);
>>          out->write((T) fft_out_buff[i]);
>>          tx->write(true);
>>
>>       }
>>       else {
>>          i ++ ;
>>
>>          fft_inp_buff[i] = (double) (inp->read() - _Offset) ;
>>          out->write((T) fft_out_buff[i]);
>>          tx->write(false);
>>       }
>>
>>       freq->write((T) i);
>>    }
>>
>>
>> };
>>
>>
>> # endif
>>
>> Regards,
>>
>> Sumit
>>
>
>
>
> --
>
> --------------------------------------------
> Sumit Adhikari
> System Design Engineer
> austriamicrosystems AG
> Business Unit : Automotive
> Mob : 00-91-9885271710/00-91-9000161710
> _______________________________________________
> Help-gsl mailing list
> address@hidden
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>



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