[time-nuts] Very Accurate Delta Time RF Pulse Measurements

Bob Stewart bob at evoria.net
Sat Jul 30 13:14:09 EDT 2016


Hi Jerome,
This may or may not be of any help, but have you considered using several RTL-SDR devices running at the same time?  You'd need to use a common clock, and probably a number of other enhancements.  But, if you could pull it off, you'd have a wideband RDF type of device.  You'd probably need to include GPS location as part of your datastream and do a lot of offline post-processing.  Rather than using the time domain, though, it would probably be easier to put the antennas in a shadow from each other and use the amplitude domain for your post-processing.

Bob -----------------------------------------------------------------
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info
-------- Original Message --------
> Hi Guys,
>
> This is a little outside of time-nuts scope, but not by much.  I'm interested in finding the time between two rising edges above a set threshold with preferably nS or high ps timing accuracy.  Can this be simply done with a few programmed Microchip PICs or with a good short term OCXO clock?  The issue I see is that a 10Mhz timing reference with 1 cycle difference in time yields 100ns resolution, which is far too large, so maybe a PIC can solve this.
>
> This weekend project would be a multi-element antenna array, each with a super-fast response log peak power detector fed into several PICs for time of arrival.  Whenever a nearby high energy RF pulse is detected, the time of arrival between two antenna elements and hence the direction toward the TX could be roughly computed.  Some typical log peak detectors have an 8ns input pulse response time, so I'm hoping that rise times are similar between multiple detectors, negating the delayed response.
>
> There are time of arrival/AoA systems out there with synthetic doppler, phased arrays, correlative interferometers, and phase comparators, but it would be interesting to accomplish super wideband AoA timing on two rising pulses with relatively cheap parts.
>
> Thanks,
>
> -Jerome
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