Commit Graph

3 Commits

Author SHA1 Message Date
Denny
8946d789ff WIP - updated tuners to use CIC decimation tuner channel sources instead
of polyphase channelizer.

Channel sample rate reduced to 30 kHz - seems to work better with P25
decoders than previous 25 kHz.
2018-09-04 08:16:57 -04:00
Denny
c13315f731 [WIP] The Two-Channel synthesizer is now fully-functional and the
channelizer sub-system is functionally complete.

Updated the channelizer and synthesizer filter design methods to use a
Kaiser windowed Nyquist filter.  Updated the synthesizer filter design
to use a new cutoff frequency of 105% of the channel bandwidth to
resolve a slight dip in the synthesized channel gain at the channel
union region.

Updated the 2 channel output processor to use a low-pass filter that
is designed for the runtime channel sample rate versus hard-coded 12.5
khz.

Testing and redesign continues ...
2018-05-20 07:21:14 -04:00
Denny
488b2e02ce [WIP] Work continues on resolving issues with the 2-channel synthesizer
that is currently up/down converting the signal of interest, but the
synthesizer is not correctly combining the original two channels.

Some experimentation with the tap count for the channelizer indicates
that we can cut the tap count in half and still have decent decoding
on the P25 decoder when paired to an aligned channelized output.  The
2-channel synthesized output decodes partially, but needs more work.

Resolved issue with channel gain in the channelizer that was making the
sample values so small that they were registering as zero when converted
from float to 16-bit int value in the complex wave recorder.
2018-04-29 06:19:39 -04:00