Beispiel #1
0
int main() {
    // spectral periodogram options
    unsigned int nfft=256;              // spectral periodogram FFT size
    unsigned int num_samples = 2001;    // number of samples
    float beta = 10.0f;                 // Kaiser-Bessel window parameter

    // allocate memory for data arrays
    float complex x[num_samples];       // input signal
    float complex X[nfft];              // output spectrum
    float psd[nfft];                    // power spectral density

    unsigned int ramp = num_samples/20 < 10 ? 10 : num_samples/20;

    // create spectral periodogram
    unsigned int window_size = nfft/2;  // spgram window size
    unsigned int delay       = nfft/8;  // samples between transforms
    spgram q = spgram_create_kaiser(nfft, window_size, beta);

    unsigned int i;

    // generate signal
    nco_crcf nco = nco_crcf_create(LIQUID_VCO);
    for (i=0; i<num_samples; i++) {
        nco_crcf_set_frequency(nco, 0.1f*(1.2f+sinf(0.007f*i)) );
        nco_crcf_cexpf(nco, &x[i]);
        nco_crcf_step(nco);
    }
    nco_crcf_destroy(nco);

    // add soft ramping functions
    for (i=0; i<ramp; i++) {
        x[i]                    *= 0.5f - 0.5f*cosf(M_PI*(float)i          / (float)ramp);
        x[num_samples-ramp+i-1] *= 0.5f - 0.5f*cosf(M_PI*(float)(ramp-i-1) / (float)ramp);
    }

    // 
    // export output file(s)
    //
    FILE * fid;
    
    // 
    // export time-doman data
    //
    fid = fopen(OUTPUT_FILENAME_TIME,"w");
    fprintf(fid,"# %s : auto-generated file\n", OUTPUT_FILENAME_TIME);
    for (i=0; i<num_samples; i++)
        fprintf(fid,"%12u %12.8f %12.8f\n", i, crealf(x[i]), cimagf(x[i]));
    fclose(fid);
    printf("results written to %s.\n", OUTPUT_FILENAME_TIME);
    
    // 
    // export freq-doman data
    //
    fid = fopen(OUTPUT_FILENAME_FREQ,"w");
    fprintf(fid,"# %s : auto-generated file\n", OUTPUT_FILENAME_FREQ);

    unsigned int t=0;
    for (i=0; i<num_samples; i++) {
        // push sample into periodogram
        spgram_push(q, &x[i], 1);

        if ( ((i+1)%delay)==0 ) {
            // compute spectral periodogram output
            spgram_execute(q, X);

            unsigned int k;

            // compute PSD and FFT shift
            for (k=0; k<nfft; k++)
                psd[k] = 20*log10f( cabsf(X[(k+nfft/2)%nfft]) );
#if 1
            for (k=0; k<nfft; k++)
                fprintf(fid,"%12u %12.8f %12.8f\n", t, (float)k/(float)nfft - 0.5f, psd[k]);
#else
            for (k=0; k<nfft; k++)
                fprintf(fid,"%12.8f ", psd[k]);
#endif
            fprintf(fid,"\n");
            t++;
        }
    }

    // destroy spectral periodogram object
    spgram_destroy(q);

    fclose(fid);
    printf("results written to %s.\n", OUTPUT_FILENAME_FREQ);

    printf("done.\n");
    return 0;
}
SpectrogramComponent::~SpectrogramComponent()
{
  if(sp_)
    spgram_destroy(sp_);
}
Beispiel #3
0
int main() {
    // spectral periodogram options
    unsigned int nfft=512;              // spectral periodogram FFT size
    unsigned int num_samples = 4000;    // number of samples
    float beta = 10.0f;                 // Kaiser-Bessel window parameter
    float noise_floor = -60.0f;         // noise floor [dB]

    unsigned int i;

    // derived values
    float nstd = powf(10.0f, noise_floor/20.0f);

    // allocate memory for data arrays
    float complex X[nfft];              // output spectrum
    float psd[nfft];                    // power spectral density

    // initialize PSD estimate
    for (i=0; i<nfft; i++)
        psd[i] = 0.0f;

    // create spectral periodogram
    unsigned int window_size = nfft/2;  // spgram window size
    unsigned int delay       = nfft/8;  // samples between transforms
    spgram q = spgram_create_kaiser(nfft, window_size, beta);

    // generate signal (interpolated symbols with noise)
    unsigned int k = 4;     // interpolation rate
    unsigned int m = 7;     // filter delay (symbols)
    firinterp_crcf interp = firinterp_crcf_create_rnyquist(LIQUID_RNYQUIST_RKAISER, k, m, 0.3f, 0.0f);

    int spgram_timer = nfft;
    unsigned int n=0;
    float complex x[k]; // interpolator output
    unsigned int num_transforms = 0;
    while (n < num_samples) {
        // generate random symbol
        float complex s = ( rand() % 2 ? 0.707f : -0.707f ) +
                          ( rand() % 2 ? 0.707f : -0.707f ) * _Complex_I;

        // interpolate
        firinterp_crcf_execute(interp, s, x);

        // add noise
        for (i=0; i<k; i++)
            x[i] += nstd * ( randnf() + _Complex_I*randnf() ) * M_SQRT1_2;

        // push resulting samples through spgram
        spgram_push(q, x, k);

        // 
        spgram_timer -= k;
        n += k;

        //
        if (spgram_timer <= 0) {
            // update timer, counter
            spgram_timer += delay;
            num_transforms++;

            // run spectral periodogram
            spgram_execute(q, X);

            // accumulate PSD and FFT shift
            for (i=0; i<nfft; i++) {
                float complex X0 = X[(i+nfft/2)%nfft];
                psd[i] += crealf(X0*conjf(X0));
            }
        }
    }

    // destroy objects
    firinterp_crcf_destroy(interp);
    spgram_destroy(q);

    // normalize result
    printf("computed %u transforms\n", num_transforms);
    // TODO: ensure at least one transform was taken
    for (i=0; i<nfft; i++)
        psd[i] = 10*log10f( psd[i] / (float)(num_transforms) );

    // 
    // export output file
    //
    FILE * fid = fopen(OUTPUT_FILENAME,"w");
    fprintf(fid,"%% %s : auto-generated file\n", OUTPUT_FILENAME);
    fprintf(fid,"clear all;\n");
    fprintf(fid,"close all;\n\n");
    fprintf(fid,"nfft = %u;\n", nfft);
    fprintf(fid,"f    = [0:(nfft-1)]/nfft - 0.5;\n");
    fprintf(fid,"H    = zeros(1,nfft);\n");
    fprintf(fid,"noise_floor = %12.6f;\n", noise_floor);
    
    for (i=0; i<nfft; i++)
        fprintf(fid,"H(%6u) = %12.4e;\n", i+1, psd[i]);

    fprintf(fid,"figure;\n");
    fprintf(fid,"plot(f, H, '-', 'LineWidth',1.5);\n");
    fprintf(fid,"xlabel('Normalized Frequency [f/F_s]');\n");
    fprintf(fid,"ylabel('Power Spectral Density [dB]');\n");
    fprintf(fid,"grid on;\n");
    fprintf(fid,"ymin = 10*floor([noise_floor-20]/10);\n");
    fprintf(fid,"ymax = 10*floor([noise_floor+80]/10);\n");
    fprintf(fid,"axis([-0.5 0.5 ymin ymax]);\n");

    fclose(fid);
    printf("results written to %s.\n", OUTPUT_FILENAME);

    printf("done.\n");
    return 0;
}