Eric Blossom wrote: > On Wed, Jun 14, 2006 at 02:00:27PM -0400, Lee Patton wrote: > >>Hi, folks - >> >>I'm trying to build an active pulsed radar using GR/USRP. Right now I am >>only concerned with the transmission and reception of pulses. All radar >>signal processing will happen offline. I know Eric is working on >>passive radar. Has anyone tried active yet? I am also working on passive radar at the moment, not active (yet). I would suggest using a chirp signal instead of a pulse. It is much more accurate and power efficient.
> On TX, the idea is to have a timestamp in the header that says "do not > transmit before time t". There will be some way to map "frames" > (variable length things possibly bigger or smaller than a USB packet), > into something we keep track of across the USB. It would also be handy to have a feedback-path for TX. The fpga could report back: TX packet AAA was transmitted on timestamp XXXX Then you can also send continuous streams (of packets) and still have exact synchronisation with RX. (RX packet BBB was received on timestamp YYYY) On my passive radar experiments. After doing a lot of simulation I am now trying to do real-world passive-radar using the usrp and just basic RX-boards with simple standard cheap FM/TV antenna-amplifiers in front of them. (I still need better filtering of the FM band) I do get signals, but it is probably not an accurate radar image. If I plot slant-range (the total distance transmitter-object-receiver) against received phasediff between my two antenna's I get allways spirals. This would suggest I have a doppler-shift which allways increases with objects further away which is not very logical. If I correlate with different doppler shifts my spirals turn around but they keep being spirals. In this image I change the doppler shift in every frame http://www.olifantasia.com/projects/gnuradio/mdvh/passive_radar/passive_radar_time_is_time_x_arc_is_phasediff_length_is_slantrange.gif In this image every frame is from samples further in time. http://www.olifantasia.com/projects/gnuradio/mdvh/passive_radar/passive_radar_time_is_doppler_x_arc_is_phasediff_length_is_slantrange.gif Greetings, Martin _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
