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#130 MPT-1327 Decoder Filter issue resolved. Converts the post-demodulation filter from a band pass filter to a low-pass filter with 60 dB attenuation and a cutoff of 3200 Hz. This is then followed by a high-pass filter at the decimated channel rate, internal to the decoder that performs DC removal and removes any CTCSS tones prior to the FSK decoder.

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This commit is contained in:
Denny
2017-01-24 20:26:57 -05:00
parent 8b403e6d87
commit 1786ffac47
3 changed files with 83 additions and 53 deletions
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20
src/module/decode/DecoderFactory.java
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@@ -101,17 +101,25 @@ public class DecoderFactory
{
private final static Logger mLog = LoggerFactory.getLogger(DecoderFactory.class);
private static final FIRFilterSpecification MPT1327_FILTER_SPECIFICATION = FIRFilterSpecification.bandPassBuilder()
.sampleRate(48000).stopFrequency1(200).passFrequencyBegin(400).passFrequencyEnd(3200)
.stopFrequency2(3400).stopRipple(0.0003).passRipple(0.008).build();
//Low-pass filter with ~60 dB attenuation and 89 taps
private static final FIRFilterSpecification MPT1327_FILTER_SPECIFICATION = FIRFilterSpecification.lowPassBuilder()
.sampleRate( 48000 )
.gridDensity( 16 )
.passBandCutoff( 3200 )
.passBandAmplitude( 1.0 )
.passBandRipple( 0.02 )
.stopBandStart( 4000 )
.stopBandAmplitude( 0.0 )
.stopBandRipple( 0.03 )
.build();
private static float[] MPT1327_BANDPASS_FILTER;
private static float[] MPT1327_LOWPASS_FILTER;
static
{
try
{
MPT1327_BANDPASS_FILTER = FilterFactory.getTaps(MPT1327_FILTER_SPECIFICATION);
MPT1327_LOWPASS_FILTER = FilterFactory.getTaps(MPT1327_FILTER_SPECIFICATION);
}
catch(Exception e)
{
@@ -221,7 +229,7 @@ public class DecoderFactory
}
modules.add(new FMDemodulatorModule(iqPass, iqStop));
modules.add(new DemodulatedAudioFilterModule(MPT1327_BANDPASS_FILTER, 2.0f));
modules.add(new DemodulatedAudioFilterModule(MPT1327_LOWPASS_FILTER, 1.0f));
modules.add(new AudioModule(metadata));
break;
case PASSPORT: