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src/dsp/nbfm/NBFMDemodulator.java

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+/*******************************************************************************
+ *     SDR Trunk 
+ *     Copyright (C) 2014 Dennis Sheirer
+ * 
+ *     This program is free software: you can redistribute it and/or modify
+ *     it under the terms of the GNU General Public License as published by
+ *     the Free Software Foundation, either version 3 of the License, or
+ *     (at your option) any later version.
+ * 
+ *     This program is distributed in the hope that it will be useful,
+ *     but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *     GNU General Public License for more details.
+ * 
+ *     You should have received a copy of the GNU General Public License
+ *     along with this program.  If not, see <http://www.gnu.org/licenses/>
+ ******************************************************************************/
+package dsp.nbfm;
+
+import sample.Broadcaster;
+import sample.Listener;
+import sample.complex.ComplexSample;
+import dsp.filter.ComplexFIRFilter;
+import dsp.filter.FilterFactory;
+import dsp.filter.Window.WindowType;
+
+public class NBFMDemodulator implements Listener<ComplexSample>
+{
+	private Broadcaster<Float> mBroadcaster = new Broadcaster<Float>();
+	private ComplexFIRFilter mIQFilter;
+	private FMDiscriminator mDiscriminator;
+
+	public NBFMDemodulator( double[] iqFilter, double iqGain )
+	{
+		mIQFilter = new ComplexFIRFilter( iqFilter, iqGain );
+
+		/**
+		 * Add the FM polar discriminator with a gain of 32768, to match
+		 * the fact that we're producing demodulated float values
+		 */
+		mDiscriminator = new FMDiscriminator( 32768 );
+
+		mIQFilter.setListener( mDiscriminator );
+
+		mDiscriminator.setListener( mBroadcaster );
+	}
+	
+	public void dispose()
+	{
+		mDiscriminator.dispose();
+		
+		mBroadcaster.dispose();
+		
+		mIQFilter.dispose();
+	}
+	
+	/**
+	 * Implements a quadrature narrow-band demodulator that produces float
+	 * valued demodulated, audio filtered output samples.
+	 */
+	public NBFMDemodulator()
+	{
+		this( FilterFactory.getLowPass( 48000, 4000, 73, WindowType.HAMMING ), 
+			  1.0002 );
+	}
+
+	/**
+	 * Receive method for complex samples that are fed into this class to be
+	 * processed
+	 */
+	@Override
+    public void receive( ComplexSample sample )
+    {
+		mIQFilter.receive( sample );
+    }
+
+	/**
+	 * Adds a listener to receive demodulated samples
+	 */
+	public void addListener( Listener<Float> listener )
+    {
+		mBroadcaster.addListener( listener );
+    }
+
+	/**
+	 * Removes a listener from receiving demodulated samples
+	 */
+    public void removeListener( Listener<Float> listener )
+    {
+		mBroadcaster.removeListener( listener );
+    }
+}