Broadband data transfer over USB for GNU/Linux: 1-2 GHz (L-band) SDR receiver dedicated to GNSS (and other) reception, interfacing with PocketSDR, GNU Radio and gnss-sdr

A dual-MAX2771 radiofrequency frontend fitted on a FX2LP parallel to USB interface is presented as an update to Tomoji Takasu's PocketSDR. Having understood the underlying operating principles of the FX2LP configured through its 8051 microcontroller core using the opensource sdcc compiler, we configure the MAX2771s to collect samples up to 44 MS/s in the L-band ranging from 1 to 2 GHz. We first demonstrate proper operation by collecting and decoding Iridium messages using gr-iridium, despite the 2 or 3-bit resolution of the IQ ADCs, before demonstrating post-processing and real time processing of GNSS data. Both real time data collection, processing and streaming using GNU Radio and GNSS signal decoding using gnss-sdr are demonstrated. Tomoji Takasu's PocketSDR software provides invaluable insight and our contribution is porting the firmware to sdcc to get rid of any proprietary tool for developing the PocketSDR-like board.

The coherent multi-receiver architecture allows for processing the same L-band with two antennas for Controlled Radiation Pattern Antenna (CRPA) processing and detecting spoofing by inconsistent direction of arrival ; or processing two bands (e.g. L1/L5 or L1/L2) simultaneously.

See https://github.com/jmfriedt/max2771_fx2lp/: the subject of this presentation was the core project of the opensource tools for embedded systems development ELISE Master teaching at University of Franche-Comté is Besançon, France.