#1397 Adds channel fft frequency overlay, cursor readout, pll tracking indicator, and channel bandwidth lines. (#1406)

Co-authored-by: Dennis Sheirer <dsheirer@github.com>

src/main/java/io/github/dsheirer/dsp/oscillator/AWGNOscillator.java

@@ -0,0 +1,117 @@
+/*
+ * *****************************************************************************
+ * Copyright (C) 2014-2023 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 io.github.dsheirer.dsp.oscillator;
+
+import io.github.dsheirer.sample.complex.ComplexSamples;
+import java.util.Random;
+
+/**
+ * Additive white gaussian noise wrapper around a complex oscillator that mixes in gaussian noise to the complex
+ * samples generated by the underlying complex oscillator.
+ */
+public class AWGNOscillator implements IComplexOscillator
+{
+    private final Random mRandom = new Random();
+    private IComplexOscillator mComplexOscillator;
+    private float mNoiseScale;
+
+    /**
+     * Constructs an instance
+     * @param complexOscillator to generate samples
+     * @param noiseScale to apply to generated samples to reduce the power of the noise and increase the SNR.
+     */
+    public AWGNOscillator(IComplexOscillator complexOscillator, float noiseScale)
+    {
+        mComplexOscillator = complexOscillator;
+        mNoiseScale = noiseScale;
+    }
+
+    /**
+     * Produce the next scaled noise sample.
+     * @return next scaled noise sample.
+     */
+    private float nextNoise()
+    {
+        return (float)mRandom.nextGaussian() * mNoiseScale;
+    }
+
+    @Override
+    public float[] generate(int sampleCount)
+    {
+        float[] generated = mComplexOscillator.generate(sampleCount);
+
+        for(int x = 0; x < generated.length; x++)
+        {
+            generated[x] += nextNoise();
+        }
+
+        return generated;
+    }
+
+    @Override
+    public ComplexSamples generateComplexSamples(int sampleCount, long timestamp)
+    {
+        ComplexSamples samples = mComplexOscillator.generateComplexSamples(sampleCount, timestamp);
+
+        for(int x = 0; x < samples.i().length; x++)
+        {
+            samples.i()[x] += nextNoise();
+            samples.q()[x] += nextNoise();
+        }
+
+        return samples;
+    }
+
+    @Override
+    public double getFrequency()
+    {
+        return mComplexOscillator.getFrequency();
+    }
+
+    @Override
+    public void setFrequency(double frequency)
+    {
+        mComplexOscillator.setFrequency(frequency);
+    }
+
+    @Override
+    public boolean hasFrequency()
+    {
+        return mComplexOscillator.hasFrequency();
+    }
+
+    @Override
+    public double getSampleRate()
+    {
+        return mComplexOscillator.getSampleRate();
+    }
+
+    @Override
+    public void setSampleRate(double sampleRate)
+    {
+        mComplexOscillator.setSampleRate(sampleRate);
+    }
+
+    @Override
+    public boolean isEnabled()
+    {
+        return mComplexOscillator.isEnabled();
+    }
+}