[Discuss-gnuradio] Wildlife Tracking (Re: fast parallel filtering)

[Andy Walls]

Hi Dirk:

On Sat, 2019-01-12 at 18:40 +0000, Dirk Gorissen wrote:
> Better late than never, but massive thanks to Andy, Marcus and the
> GnuRadio community:
> 
> https://dirkgorissen.com/2019/01/06/wheres-pinoh-tracking-orangutans-
> with-drones-and-gnu-radio/

You're welcome.  It was our pleasure to help.

I was wondering when the report would come out.  I had periodically
checked your Twitter for the few months following March 2018, but never
saw anything.

I'm sure the data analysis is fascinating, even though the collection
was degraded by the sub-optimal antenna.  I've been in a similar
situation: collect data with sub-optimal system, get tantalizing bits
of good data along with lots of noisy data, fix system and wait for
opportunity to collect more data.  Waiting for the time window to get
more data with the fixed system is frustrating. :P

In your report you mention:

1. "Some implants seemed to transmit much longer and stronger than the
10ms pulse they should be transmitting."

That lengthened pulse will widen your time domain correlation "peaks". 
The stronger pulse will muck with your thresholds, if the thresholds
aren't adaptive. Or maybe you're using a CFAR detector? (As I write
this, I'm musing how similar this is to RADAR or IFF: pulse compression
followed by a CFAR filter/detector.) 


2. "The pulse would also be mirrored in the spectrum at times [...]"

An impairment common to almost all SDR hardware is I/Q imbalance (along
with DC offset).  I/Q imbalance will result in the spectrum having a
weaker image of the signal spectrum reflected about 0 Hz.  If the SDR
manufacturer hasn't calibrated most of the imbalance away for you using
harware chip functions, you have to get rid of I/Q imbalance and DC
offset using software.

Some more reading on the topic, if it matters to you: 
https://www.analog.com/media/en/technical-documentation/application-notes/AN-1039.pdf
https://www.faculty.ece.vt.edu/swe/argus/iqbal.pdf
https://cgit.osmocom.org/gr-iqbal/


Also, unless "Alan Walls" speaks up, I think you typo'ed my name at the
end of your write-up. :)


Anyway, great work.  Being the Principal Investigator and doing all the
hardware, software, analysis, and field data collection legwork is a
big job for one person.


Regards,
Andy