[Discuss-gnuradio] Active Radar Hardware

[Lee Patton]

My active radar code has been working for some time, but I'm just now
getting around to thinking about real-world tests.  The difficulty I'm
facing at the moment is how to isolate the transmitter and receiver
while still providing decent power on target.  I'm looking for
suggestions.

Right now, using the RFX2400, I'm thinking something like:


Tx/Rx port ----> AMP ----------->.
                                 |
                            circulator <----> Antenna
                                 |
Rx2 port   <---- LNA <-----------.

where ---- is coax.


I found a nice LNA with SMA connectors from MiniCircuits (25 dB gain,
1.0 dB noise figure), but the problem is that all of the 2.4 GHz
circulators I have found offer only ~20 dB of isolation.  So, even with
the "AMP" gain set to 0 dB, the Tx power into the circulator will be
+13dBm.*   Any attenuation to this signal via the circulator en route to
the receiver will be undone by the LNA, and +13 dBm > 0 dBm, which is
the safe level for the receiver.**  I cannot turn down the transmit
power if I hope to be able to operate at useful ranges.

I have zero experience building a system like this. I'll be thinking a
lot more about it, and looking for better parts, but I've learned to ask
the experts early ;) Any ideas?

Thanks,
 -Lee

*http://lists.gnu.org/archive/html/discuss-gnuradio/2006-06/msg00238.html
**http://lists.gnu.org/archive/html/discuss-gnuradio/2006-09/msg00291.html

P.S. The parts I'm considering can be found here:

http://www.minicircuits.com/cgi-bin/inquery.cgi?querystring=ZQL-2700MLNW&searchtype=modelfamily&x=23&y=10
http://www.ditom.com/product_info.php?products_id=30&osCsid=9339bea3608c32e01f46033a16b8255f