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#1106 Adds half-band filter create to filter factory (#1107)

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Co-authored-by: Dennis Sheirer <dsheirer@github.com>
This commit is contained in:
Denny Sheirer
2021-11-21 04:17:54 -05:00
committed by GitHub
parent b8bbe9264a
commit 87b3d34024
2 changed files with 78 additions and 69 deletions
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90
src/main/java/io/github/dsheirer/dsp/filter/FilterFactory.java
View File

@@ -1,25 +1,21 @@
/*******************************************************************************
* SDR Trunk
* Copyright (C) 2014,2015 Dennis Sheirer
/*
* *****************************************************************************
* Copyright (C) 2014-2021 Dennis Sheirer
*
* Root Raised Cosine filter designer:
* Copyright 2002,2007,2008,2012,2013 Free Software Foundation, Inc.
* http://gnuradio.org/redmine/projects/gnuradio/repository/changes/gr-filter
* /lib/firdes.cc?rev=435b1d166f0c7092bbd5e1f788e75dbb6ade3a4b
* 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 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.
*
* 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/>
******************************************************************************/
* 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.filter;
import io.github.dsheirer.dsp.filter.design.FilterDesignException;
@@ -31,7 +27,7 @@ import org.jtransforms.fft.FloatFFT_1D;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.Arrays;
import java.text.DecimalFormat;
import java.util.Set;
import java.util.TreeSet;
@@ -1001,6 +997,44 @@ public class FilterFactory
return coefficients;
}
/**
* Creates a symmetrical half-band filter where all odd-indexed coefficients except center are zero
* valued.
* @param length N is odd where m is an integer multiple in the formula: N = 4m + 3 (e.g. 7, 11, 15, etc.)
* @param windowType to apply to the filter.
* @return coefficients
*/
public static double[] getHalfBand(int length, Window.WindowType windowType)
{
if((length - 3) % 4 != 0)
{
throw new IllegalArgumentException("Half Band filter length (N) must be an odd length where m must be an " +
"integer multiple in (N=4m+3), e.g. 7, 11, 15, etc");
}
double[] window = Window.getWindow(windowType, length);
double[] taps = new double[length];
int halfLength = length / 2;
for(int x = 0; x < length; x++)
{
int offset = x - halfLength;
if(offset == 0)
{
taps[x] = 0.5f; //No window here - window coefficient should be 1.0 anyway
}
else if((x % 2) == 0)
{
//Only calculate the even-index taps, leaving odd-index taps at default value of zero
taps[x] = (float)((Math.sin(offset * Math.PI / 2) / (offset * Math.PI)) * window[x]);
}
}
return taps;
}
/**
* Compares two doubles for equals and avoids any rounding error that are present.
*
@@ -1015,17 +1049,17 @@ public class FilterFactory
public static void main(String[] args)
{
float[] taps = null;
DecimalFormat df = new DecimalFormat("0.000000");
try
int length = 15;
double [] taps = FilterFactory.getHalfBand(length, Window.WindowType.HAMMING);
for(int x = 0; x < length; x++)
{
taps = FilterFactory.getSincM2Channelizer(12500.0, 800, 9, true);
}
catch(FilterDesignException fde)
{
mLog.error("Error", fde);
mLog.debug("Tap: " + x + " Value: " + df.format(taps[x]));
}
mLog.debug("Done: " + Arrays.toString(taps));
mLog.debug("Done!");
}
}

57
src/main/java/io/github/dsheirer/dsp/filter/Window.java
View File

@@ -1,39 +1,22 @@
/*******************************************************************************
* sdr-trunk
* Copyright (C) 2014-2018 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/>
*
******************************************************************************/
/*
* Kaiser Window design methods: getKaiser(), getKaiserBeta() and getBesselZerothOrder() with minor naming changes were
* adopted from:
* *****************************************************************************
* Copyright (C) 2014-2021 Dennis Sheirer
*
* https://github.com/rjeschke/neetutils-base/blob/master/src/main/java/com/github/rjeschke/neetutils/audio/FIRUtils.java
* 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.
*
* Copyright (C) 2012 René Jeschke <rene_jeschke@yahoo.de>
* 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.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
* 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.filter;
import org.apache.commons.math3.util.FastMath;
@@ -294,13 +277,9 @@ public class Window
{
double[] coefficients = new double[length];
double a0 = 0.54;
double a1 = 0.46;
double denominator = length;
for(int x = 0; x < length; x++)
{
coefficients[x] = a0 - (a1 * FastMath.cos(TWO_PI * (double)x / denominator));
coefficients[x] = 0.54 - (0.46 * FastMath.cos((TWO_PI * x) / (length - 1)));
}
return coefficients;
@@ -316,13 +295,9 @@ public class Window
{
double[] coefficients = new double[length];
double a0 = 0.5;
double a1 = 0.5;
double denominator = length;
for(int x = 0; x < length; x++)
{
coefficients[x] = a0 - (a1 * FastMath.cos(TWO_PI * (double)x / denominator));
coefficients[x] = 0.5 - (0.5 * FastMath.cos(TWO_PI * (double)x / (length - 1)));
}
return coefficients;