Yesterday we had Matt Ettus from Ettus Research and Leif Johansson from National Instruments visiting SGO. We had a one-day meeting on mainly EISCAT_3D and KAIRA related things. Naturally, the scope was in the software radio defined technologies and on how to use them with phased-array systems. Hence, today we feature two photos of the meeting.
Derek McKay (on the right hand-side) presenting KAIRA to Markku Lehtinen (on the left hand-side), Leif Johansson and Matt Ettus.
Markku Lehtinen and Matt Ettus in front of the 32-metre EISCAT VHF receiver dish in Sodankylä.
This past week, a team from KAIRA/SGO, LTU and EISCAT have been installing a digital beamforming system on the Kiruna Demonstrator Array. Today, we feature some of the photographs from the installation of the field equipment.
Tomi brings out more USRP subracks. (Photo: D. McKay-Bukowski)
Johan installing the LTU receiver system. (Photo: D. McKay-Bukowski)
Lars-Göran runs the cables back into the main building. (Photo: D. McKay-Bukowski)
This week, I spent a few more days trying to understand the errors related with strong radar targets in the analysis of weak targets in passive radar. As a consequence of this, I wrote a linear least squares estimator to remove this contribution more effectively (and consistently). I also optimized my code a bit, and got a massive speed-up. Now the signal processing and plotting all runs in real time.
This video shows a lot of aeroplanes around the New England area detected using a simple passive radar setup, consisting of: one USRP and two yagi antennas, a quad core Linux PC. Every now and then an occasional specular meteor echo is observed too. Because this is FM radio, the waveform is not always optimal for inverting the echoes, which results in a blow up of the solutions when the waveform is narrow band (eg., somebody talking, or silence). This is not a problem with digital modulation schemes, which will be explored next.
I updated my code. I came up with a way to efficiently estimate ground clutter and transmitter self-noise using a linear least squares matrix equation, which works better than the previous attempt. I also made some optimizations that allow me to run this in real-time using a normal PC. Next up: imaging using the midas-mini cube.
Tomi Teppo, Derek McKay-Bukowski, and I have been working on the 16-channel USRP N210 system that I put together before I left _. In anticipation of using this with a phased array antenna array in Kiruna, the setup needed to be modified in a way that all USRPs communicate via a switch, as the field site only has one fibre optic cable going into the building. A few days ago, we completed the setup and verified that we can do get 16 channels through a switch. This was not possible just a little while ago, so the firmware has definitely improved. Before all the channels were directly connected to the computer. Hurray!
This system will have many cool uses with eg., riometry, or HF radar imaging.
16 channel USRP N210 setup.
USRP racks.
8 USRPs going one switch, which has one 1 Gbit line going to the computer. I don't know what the upper switch is for though (maybe testing).
All the equipment. Everything is still a bit tangled.
Two computers. More computers can be added if we need more bandwidth or computational capacity.
Today I cabled up the new MIDAS-Mini system that Frank Lind and I are putting together at MIT Haystack. This is a suitcase sized shock mounted rack that contains four USRP N200 devices, an octoclock (gps stabilized oscillator and a 1 PPS + 10 MHz clock splitter), and a 1 U server computer. The computer is fast enough to simultaneously record four 25 MHz wide bands of data, which will be very useful. The box is small and rugged enough to be transported on an airplane.
We currently have two such racks, and there are plans to build more at a later point. With multiple boxes it is possible to get even more channels, and it is possible to chain the clock together to act as 4Nx4N MIMO systems.
Yeah, the cabling sucks. I just wanted to get my testing and calibration routines running. This will be cleaned up.
