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Will discuss the code in fragments

As usual, I will discuss the code in fragments. A complete listing of the program is presented in Listing 19 near the end of the module. Because of the similarity of Dsp028 with Dsp029 discussed earlier, the fragments for Dsp028 will be much larger and will be explained in much less detail.

Beginning of the class named Dsp028

The class definition begins in Listing 8 . For reasons that you already understand, this class implements the interface named GraphIntfc01.

Listing 8. Beginning of the class named Dsp028.
class Dsp028 implements GraphIntfc01{ final double pi = Math.PI;//for simplification//Begin default parameters int len = 400;//data length//Sample that represents zero time. int zeroTime = 0;//Low and high frequency limits for the // spectral analysis.double lowF = 0.0; double highF = 1.0;int numberSpectra = 5; //Frequencies of the sinusoidsdouble[] freq = {0.1,0.2,0.3,0.4,0.5};//Amplitudes of the sinusoids double[]amp = {60,70,80,90,100}; //End default parameters

The code in Listing 8 defines a set of default parameter values that are used in the event that a file named Dsp028.txt does not exist in the current directory.

Declare array variables

The code in Listing 9 declares several array variables that will be used to point to array objects whose purposes are explained in the comments.

Listing 9. Declare array variables.
//Following arrays will contain data that is // input to the spectral analysis process.double[] data1;double[] data2;double[] data3;double[] data4;double[] data5;//Following arrays receive information back // from the spectral analysis that is not used// in this program. double[]real; double[]imag; double[]angle; //Following arrays receive the magnitude// spectral information back from the spectral // analysis process.double[] magnitude1;double[] magnitude2;double[] magnitude3;double[] magnitude4;double[] magnitude5;

The constructor

The constructor for the class begins in Listing 10 . The constructor begins by getting the parameters from a file named Dsp028.txt . If that file doesn't exist in the current directory, default parameters are used.

Listing 10. Beginning of the constructor.
public Dsp028(){//constructor if(new File("Dsp028.txt").exists()){getParameters(); }//end if

Always processes five sinusoids

For simplicity, this program always processes five sinusoids, even if fewer than five were requested as the input parameter for numberSpectra . In that case, the extra sinusoids are processed using default values and simplyignored when the results are plotted.

Create the raw sinusoidal data

The code in Listing 11 instantiates array objects and creates the sinusoidal data upon which spectral analysis will be performed.

Listing 11. Create the raw sinusoidal data.
//First create empty array objects. double[]data1 = new double[len];double[] data2 = new double[len]; double[]data3 = new double[len];double[] data4 = new double[len]; double[]data5 = new double[len];//Now populate the array objects for(int n = 0;n<len;n++){ data1[n]= amp[0]*Math.cos(2*pi*n*freq[0]); data2[n]= amp[1]*Math.cos(2*pi*n*freq[1]); data3[n]= amp[2]*Math.cos(2*pi*n*freq[2]); data4[n]= amp[3]*Math.cos(2*pi*n*freq[3]); data5[n]= amp[4]*Math.cos(2*pi*n*freq[4]); }//end for loop

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Source:  OpenStax, Digital signal processing - dsp. OpenStax CNX. Jan 06, 2016 Download for free at https://legacy.cnx.org/content/col11642/1.38
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