/* SigLib Amplitude Modulation / Demodulation Example */ #include #include #include "GraphFunctions.h" #include "plot_fd.h" /* Define constants */ #define SAMPLE_RATE ((SLData_t)10000.0) #define CARRIER_FREQUENCY ((SLData_t)2500.0) #define CARRIER_TABLE_LENGTH ((SLArrayIndex_t)1000) #define PRE_FILTER_LENGTH 14L #define LPF_FILTER_LENGTH 27L #define SAMPLE_LENGTH 256L #define FFT_SIZE 256L #define LOG_FFT_SIZE ((SLArrayIndex_t)8) /* Initialise filter coefficients */ SLData_t pPreFilterTaps[PRE_FILTER_LENGTH] = { -2.0, -5.0, -6.0, -5.0, -1.5, 4.5, 9.0, 10.0, 9.0, 4.5, -1.0, -5.0, -6.0, -2.0 }; SLData_t pPreFilterState[PRE_FILTER_LENGTH]; SLArrayIndex_t PreFilterIndex; SLData_t pLpfFilterTaps[LPF_FILTER_LENGTH] = { 0.076923, 0.0, -0.09091, 0.0, 0.111111, 0.0, -0.14286, 0.0, 0.2, 0.0, -0.33333, 0.0, 1.0, 1.570796, 1.0, 0.0, -0.33333, 0.0, 0.2, 0.0, -0.14286, 0.0, 0.111111, 0.0, -0.09091, 0.0, 0.076923 }; SLData_t pLpfFilterState[LPF_FILTER_LENGTH]; SLArrayIndex_t pLpfFilterIndex; SLData_t *pInput, *pCarrierTable, *modulated, *demodulated; SLData_t CarrierTablePhase; void main(void); void main(void) { GraphObject *h2DGraph; /* Declare graph object */ pInput = SUF_VectorArrayAllocate (SAMPLE_LENGTH); pCarrierTable = SUF_VectorArrayAllocate (CARRIER_TABLE_LENGTH); modulated = SUF_VectorArrayAllocate (SAMPLE_LENGTH); demodulated = SUF_VectorArrayAllocate (SAMPLE_LENGTH); h2DGraph = /* Initialize graph */ Create2DGraph ("Amplitude Modulation / Demodulation", /* Graph title */ "Time", /* X-Axis label */ "Magnitude", /* Y-Axis label */ SV_AUTO_SCALE, /* Scaling mode */ SV_SIGNED, /* Sign mode */ SV_GRAPH_LINE, /* Graph type */ "localhost"); /* Graph server */ if (h2DGraph == NULL) /* Graph creation failed - e.g is server running ? */ { printf ("\nGraph creation failure. Please check that the server is running\n"); exit (1); } SIF_AmplitudeModulate2 (pCarrierTable, /* Carrier table pointer */ &CarrierTablePhase, /* Carrier table index */ CARRIER_TABLE_LENGTH); /* Modulator array length */ SIF_Fir (pPreFilterState, /* Pointer to filter state array */ &PreFilterIndex, /* Pointer to filter index register */ PRE_FILTER_LENGTH); /* Filter length */ SIF_Fir (pLpfFilterState, /* Pointer to filter state array */ &pLpfFilterIndex, /* Pointer to filter index register */ LPF_FILTER_LENGTH); /* Filter length */ /* Generate signal to be shifted */ SDA_SignalGenerate (pInput, /* Pointer to destination array */ SIGLIB_IMPULSE, /* Signal type - Impulse function */ SIGLIB_ONE, /* Signal peak level */ SIGLIB_FILL, /* Fill (overwrite) or add to existing array contents */ SIGLIB_ZERO, /* Signal frequency - Unused */ SIGLIB_ZERO, /* D.C. Offset */ SIGLIB_ZERO, /* Unused */ SIGLIB_ZERO, /* Signal end value - Unused */ SIGLIB_NULL_DATA_PTR, /* Unused */ SIGLIB_NULL_DATA_PTR, /* Unused */ SAMPLE_LENGTH); /* Output array length */ /* Apply fir filter and store filtered data */ SDA_Fir (pInput, /* Input array to be filtered */ pInput, /* Filtered output array */ pPreFilterState, /* Pointer to filter state array */ pPreFilterTaps, /* Pointer to filter coefficients */ &PreFilterIndex, /* Pointer to filter index register */ PRE_FILTER_LENGTH, /* Filter length */ SAMPLE_LENGTH); /* Array length */ Display2DGraph (h2DGraph, /* Graph handle */ "Source Signal", /* Title of the dataset */ pInput, /* Array of Double dataset */ SAMPLE_LENGTH, /* Number of data points */ SV_GRAPH_LINE, /* Graph type */ SV_BLUE, /* Colour */ SV_HIDE_MARKERS, /* Marker enable / disable */ SV_GRAPH_NEW); /* New graph */ printf ("\nSource Signal\nPlease hit to continue . . ."); getchar (); plot_frequency_domain (pInput, SIGLIB_FLAT_TOP, "Raw signal spectrum ", SAMPLE_LENGTH, FFT_SIZE); SDA_AmplitudeModulate2 (pInput, /* Modulating signal source pointer */ pCarrierTable, /* Carrier table pointer */ modulated, /* Modulated signal destination pointer */ &CarrierTablePhase, /* Carrier table phase */ CARRIER_FREQUENCY / SAMPLE_RATE, /* Carrier frequency */ CARRIER_TABLE_LENGTH, /* Modulator array length */ SAMPLE_LENGTH); /* Array length */ Display2DGraph (h2DGraph, /* Graph handle */ "Modulated Signal", /* Title of the dataset */ modulated, /* Array of Double dataset */ SAMPLE_LENGTH, /* Number of data points */ SV_GRAPH_LINE, /* Graph type */ SV_BLUE, /* Colour */ SV_HIDE_MARKERS, /* Marker enable / disable */ SV_GRAPH_NEW); /* New graph */ printf ("\nModulated Signal\nPlease hit to continue . . ."); getchar (); plot_frequency_domain (modulated, SIGLIB_FLAT_TOP, "Modulated signal spectrum ", SAMPLE_LENGTH, FFT_SIZE); SDA_AmplitudeModulate2 (modulated, /* Modulating signal source pointer */ pCarrierTable, /* Carrier table pointer */ demodulated, /* Modulated signal destination pointer */ &CarrierTablePhase, /* Carrier table phase */ CARRIER_FREQUENCY / SAMPLE_RATE, /* Carrier frequency */ CARRIER_TABLE_LENGTH, /* Modulator array length */ SAMPLE_LENGTH); /* Array length */ SIF_Fir (pLpfFilterState, /* Pointer to filter state array */ &pLpfFilterIndex, /* Pointer to filter index register */ LPF_FILTER_LENGTH); /* Filter length */ SDA_Fir (demodulated, /* Input array to be filtered */ demodulated, /* Filtered output array */ pLpfFilterState, /* Pointer to filter state array */ pLpfFilterTaps, /* Pointer to filter coefficients */ &pLpfFilterIndex, /* Pointer to filter index register */ LPF_FILTER_LENGTH, /* Filter length */ SAMPLE_LENGTH); /* Array length */ Display2DGraph (h2DGraph, /* Graph handle */ "Demodulated Signal", /* Title of the dataset */ demodulated, /* Array of Double dataset */ SAMPLE_LENGTH, /* Number of data points */ SV_GRAPH_LINE, /* Graph type */ SV_BLUE, /* Colour */ SV_HIDE_MARKERS, /* Marker enable / disable */ SV_GRAPH_NEW); /* New graph */ printf ("\nDemodulated Signal\nPlease hit to continue . . ."); getchar (); plot_frequency_domain (demodulated, SIGLIB_FLAT_TOP, "Demodulated signal spectrum ", SAMPLE_LENGTH, FFT_SIZE); SUF_MemoryFree (pInput); /* Free memory */ SUF_MemoryFree (pCarrierTable); SUF_MemoryFree (modulated); SUF_MemoryFree (demodulated); }