Steve Ellingson (Virginia Tech)
This page is http://www.ece.vt.edu/swe/eta/ARX/
23 Oct 2006. Added pictures of rack-mounted ARX and measured response.
21 Sep 2006. Added pictures of ARX in enclosure.
22 Jun 2006. Started page
|(Click image for high-res.) The first 16 version 3 ARX modules, mounted in rack. Front view. October 23, 2006.|
|(Click image for high-res.) The first 16 version 3 ARX modules, mounted in rack. Rear view. October 23, 2006.|
|(Click image for high-res.) Frequency response of "production" version 3 ARX, complete in enclosure. NOTE: This illustration shows gain minus 50 dB (i.e., add 50 dB to get actual response.) October 23, 2006.|
|(Click image for high-res.) ARX version 3, complete in enclosure. The enclosure is a Vector model, which is inexpensive and fits nicely in groups of 8 in Vector's CMA13 card rack. October 9, 2006.|
|(Click image for high-res.) ARX version 3, with back panel and connectors attached. The N-connector is RF in, SMA is RF out, and the DB9 conveys power and 3-bit attenuator control. October 9, 2006.|
|(Click image for high-res.) ARX version 2: It's a 4-layer board, which is 4 inches by 4 inches (any numerologists care to comment?), designed to fit in a Vector card cage-mountable enclosure. The big blue thing is a coaxial relay which physically separates the receiver from the cable when the power is turned off -- the idea is to reduce the likelihood of lightning- or static-related damage when the system is not being used. Actually, it's the $100K+ in digital electronics behind the receiver I'm really worried about. The rectangles appearing in the layout are fittings for FerriShield Model PS100EMC24 shielding enclosures (sometimes referred to as "cans"). FWIW, I noticed absolutely no difference in performance with cans on vs. cans off, so at this moment I'm thinking to leave them off. That might change after trying this out in a box in field conditions. Also visible are the two holes I had to drill to fix a bone-headed layout error. I left off the DB9 connector but you can see where it goes. Also I have MMCX connectors on the input and output just because I currently have a ton of these.|
Max Gain: 52.3 dB
1 dB Bandwidth: 30.7 - 43.7 MHz
3 dB Bandwidth: 27.3 - 47.3 MHz
40 dB Bandwidth: 17.7 - 65.3 MHz
Attenuation in 4 dB steps, 3 bits, to 24 dB total
Power: 330 mA @ 12VDC (accepts 12-15 VDC)
I didn't measure noise figure or IP3. The GNI analysis, combined with the active balun and feedline, give a cascade noise temperature of 256 K and IIP3 of -41 dBm (OIP3 = +38 dBm). Appears to be unconditionally stable, even without the cans; however, I did not try it in a box. The bandwidth is determined entirely by the 2 custom BPFs. The bandwidth of everything else exceeds LWA preliminary specs by a large margin. Might be possible to develop an LWA version just by changing the component values, keeping the same BPF topology.
Cost: As shown: $260 each, quantity 2. The PCBs will be the big quantity price break; in quantity 2 I get the PCBs for $162 each; could be had for much less if I ordered larger quantities. The cans cost $22 each, so the total "as shown" cost goes from $260 to $304 if cans are used. The coax relay is $28; a bit pricey but I really like the idea of being able to electronically "stow" the system. The attenuator is $47; that can definately be done more cheaply for LWA.
|(Click image for high-res.) The schematic.|
|(Click image for high-res.) Top layer of PCB.|
|(Click image for high-res.) Layer 2 of PCB (ground plane).|
|(Click image for high-res.) Layer 3 of PCB (power plane; a combination of 5V, 9V, and 12V).|
|(Click image for high-res.) Layer 4 of PCB (more traces). Mostly used to dive under the can boundaries. No components on the back side, but a few through-hole components.|