Signal Processing with GNU Radio

Jon Jacky

Magnetic Resonance Force Microscopy (MRFM)

Goal: molecular microscope, 3D images of individual molecules in situ

Marriage of atomic force microscope (AFM) and MRI imaging

RF coil (left), sample positioner (bottom), interferometer (top), cantilever (right)

Cantilever requires closed loop control: our GNU Radio application

MRFM Laboratory

MRFM Experiment Control Software

http://staff.washington.edu/jon/gr-mrfm/

GNU Radio

http://vps.gnuradio.org/redmine/wiki/gnuradio

GNU Radio technology stack

Integrated design from volts to GUI.

Developers are encouraged to program several layers (optimize across the whole stack).

GNU Radio hardware

http://vps.gnuradio.org/redmine/wiki/gnuradio/UsrpFAQIntro

Universal Sofware Radio Peripheral (USRP)

• 2 x AD9862 codec: each 2 A/D 12 bit, 64 Megasamples/sec; 2 D/A, 14 bit, 128 Ms/sec
• FPGA: Altera Cyclone EP1C12, 64 MHz, 12,060 LEs, 239,616 RAM bits
• USB 2.0, Cypress FX2
• 4 x daughterboards for signal conditioning

Available from Ettus Research LLC, but design is open source.

Newer USRP2 has 100 MHz converters, much larger Xilinx FPGA

Python programming

Connect signal processing blocks into a network and add a GUI.

http://vps.gnuradio.org/redmine/wiki/gnuradio/TutorialsWritePythonApplications

Signal processing

Select signal processing blocks from the GNU Radio library.

http://gnuradio.org/doc/doxygen/modules.html

Or, program your own in C++.

http://www.gnu.org/software/gnuradio/doc/howto-write-a-block.html

FPGA programming

Program the hardware on the USRP board.

http://staff.washington.edu/jon/verilog-prog.html

FPGA: sea of logic gates and flipflops, your program connects them.

Design your own special-purpose computer (DSP or ...)

• Program in Verilog (C-like syntax)
• Free development system from FPGA vendor
• Store program on host, load into FPGA under program control
• Highly parallel, all variables can update simultaneously (on each clock tick)
• No operating system (no resource sharing)