GRCon20 - Software defined radio based Synthetic Aperture noise and OFDM (WiFi) RADAR mapping
0Presented by Jean-Michel Friedt, and Weike Feng at GNU Radio Conference 2020 https://gnuradio.org/grcon20
Software defined radio based Synthetic Aperture noise and OFDM (WiFi) RADAR mapping (Main Track) [application]
Session Chair: Jean-Michel Friedt, FEMTO-ST/Time & Frequency
We demonstrate the use of commercial, off the shelf hardware for Software Defined Radio based RADAR measurements. Starting with a UHF RADAR demonstration hinting at some reflections attributed to targets in the 100-m range, the aim of identifying the source of the reflections led to implement a synthetic aperture RADAR. Because of the challenge of synchronizing transmitting and receiving local oscillators, we have selected to separate the transmitter and the receiver, using either a PlutoSDR generating a pseudo-random phase modulated signal for spectrum spreading, or a WiFi emitting USB dongle for OFDM spectrum spreading. The receiver is a dual-channel Ettus Research B210 SDR platform with both channels set as receivers, one for reference and the other for measurement. Range compression is the first step demonstrating the proper operation of the RADAR in the 2.4 GHz ISM band. Moving the receiving antenna while keeping the emitting antenna at a fixed location allows for creating a synthetic aperture receiving antenna with azimuth compression capability. Finally, automating the scanning with a motorized rail allows for reproducible measurements and hence interferometric Ground Based Synthetic Aperture RADAR motion measurements. Most fascinating is how such challenging signal processing aspects become accessible to dedicated experimenters thanks to affordable Software Defined Radio platforms. Beyond the use of GNU Radio for data streaming through a 0-MQ socket, we explain how the Python script generated by GNU Radio Companion is updated to include a TCP server receiving commands for tuning the local oscillator frequency of the transmitter and receiver and moving the antenna setup along the rail. Emphasis will be given on separating acquisition (GNU Radio), experiment control (Python) and signal processing (GNU Octave).