[time-nuts] Precise Time transfer and relative position over a short baseline
jimlux
jimlux at earthlink.net
Mon Apr 11 08:33:50 EDT 2016
On 4/11/16 1:40 AM, Björn wrote:
> Hi Bruce,
>
> For such short baselines single frequency GNSS should be able to keep fixed integer solutions. Not sure how much money thas is going to save, since you might need timing specific geodetic receivers to get external 10MHz input.
>
> Did you consider implementing time transfer using time reversal using say a sdr tranciever (usrp or other) where your clock is driving the radio. As done on HF by Yen & Sengupta at last PTTI.
>
> https://www.ion.org/ptti/abstracts.cfm?paperID=3373
>
VLA used VHF (I think) radio links to provide common phase reference
among apertures.
Consider, for example, using a 1 GHz CW carrier among your stations.
With good SNR, tracking phase to 1/1000th of a cycle should be
straightforward.
The challenge will be (as always with this kind of thing) the mechanical
effects. Motion of 1mm is 3ps.
On the other hand, my victim detection radar trivially measures 1mm
displacements in path length with 20 dB SNR with EIRP of 1 mW, omni
antennas, and a range of 30m with a 0.1 square meter target. That's at
3 GHz.
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