Re: [USRP-users] problem with fftw_plan_dft_2d

[Marcus D. Leech via USRP-users]

On 05/16/2019 11:52 PM, Koyel Das (Vehere) via USRP-users wrote:

Hi,


Following is a snapshot of my code using fftw_plan_dft_2d. I am 
getting all zeros in the imaginary part of fft (in the printf command 
of the following code:last line). The real part is correct.Could you 
please tell where am I going wrong?


 fftw_complex *imageOutputPlane=VDDSAlgorithm::imageOutPlane;

    fftw_complex *imageInputPlane=VDDSAlgorithm::imageInputPlane;
    unsigned char*imageData=VDDSAlgorithm::imageData;
    unsigned char*imageDataFinal=VDDSAlgorithm::imageDataFinal;

memset(imageInputPlane,0x0,IMAGE_DIMENSION*IMAGE_DIMENSION*sizeof(fftw_complex));
memset(imageOutputPlane,0x0,IMAGE_DIMENSION*IMAGE_DIMENSION*sizeof(fftw_complex));
    memset(imageData,0x0,IMAGE_DIMENSION*IMAGE_DIMENSION);

    for(size_t count=0;count<TOTAL_BASE_LINE;count++){
 
imageInputPlane[(int)round(IMAGE_DIMENSION/2+diffX[count])*IMAGE_DIMENSION+(int)round(IMAGE_DIMENSION/2-diffY[count])][0]=phy[count][0];
 
imageInputPlane[(int)round(IMAGE_DIMENSION/2+diffX[count])*IMAGE_DIMENSION+(int)round(IMAGE_DIMENSION/2-diffY[count])][1]=-(phy[count][1]);
 
imageInputPlane[(int)round(IMAGE_DIMENSION/2-diffX[count])*IMAGE_DIMENSION+(int)round(IMAGE_DIMENSION/2+diffY[count])][0]=phy[count][0];
 
imageInputPlane[(int)round(IMAGE_DIMENSION/2-diffX[count])*IMAGE_DIMENSION+(int)round(IMAGE_DIMENSION/2+diffY[count])][1]=phy[count][1];
    }

    fftLock.lock();
    fftw_plan 
 planeX=fftw_plan_dft_2d(IMAGE_DIMENSION,IMAGE_DIMENSION, 
imageInputPlane, imageOutputPlane, FFTW_FORWARD, FFTW_ESTIMATE);
    fftw_execute(planeX);
    fftw_destroy_plan(planeX);
    fftLock.unlock();


    double max=0;
    for(size_t row=0;row<IMAGE_DIMENSION;row++){
        for(size_t col=0;col<IMAGE_DIMENSION;col++){
            if(col==0)printf("\n");
            if(col<100){
printf("(%lf,%lf)",imageOutputPlane[row*IMAGE_DIMENSION+col][0],imageOutputPlane[row*IMAGE_DIMENSION+col][1]);
            }
        }
    }

Regards,

Koyel Das
Senior – Product Engineer

Vehere | Proactive Communications Intelligence & Cyber Defence
M: +919051132173 | T: +91 33 40545454 | F: +91 33 40545455 | W: 
www.vehere.com <http://www.vehere.com/>//
I'm having a hard time seeing how this is related to UHD and USRPs.

There's probably a support forum for FFTW out there that would be more 
helpful than here.


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