Abstract
M.Ing.
This dissertation studies the use of GNU Radio (a free software development toolkit that provides signal processing blocks to implement software-defined radios and signal-processing systems) and the universal software radio peripheral (USRP) with the aim of exploring frequency modulated continuous wave (FMCW) radar. Radar uses radio frequencies to determine the range, Doppler shift and bearing for a target. This is used to determine the range, altitude, direction and speed of objects. Software-defined radio allows radio operations to be controlled in software, and has the capability of implementing portable, cheap and configurable radar systems provided that it meets the required radar performance.
The design of the radar had to be based on user requirements coupled with performance specifications. The requirement was to design and implement an FMCW surveillance radar to detect a drone with an RCS (radar cross-section) of 0.1 m2 and a maximum range of 150 m for the purpose of point detection. A USRP B210 transceiver was used for the project, while the antenna and amplifiers selected had to improve the performance of the USRP B210 to meet the given performance specifications.
This dissertation introduces an FMCW radar using GNU Radio to generate sawtooth and triangular waveforms. A simulation target was also designed, whose radial velocity and range could be controlled in real time. It can be used for simulation and testing and to check if the signal processing does what it is supposed to do before field tests are carried out. Signal processing was done in Python for either triangular or sawtooth waveforms in order to extract the range and radial velocity. The signal processing takes the beat frequency which has pulse compression gain and performs coherent integration. It windows and displays the results on a range Doppler map using two-dimensional Fast Fourier Transform (FFT) when a sawtooth waveform is used.
The radar was designed to use the sawtooth waveform to create detections for multiple targets. The Pulse Repetition Frequency (PRF) of the waveform is selected as 2 200 Hz with a chirp bandwidth of 28 MHz. The PRF selected is able to resolve a maximum velocity of 30 m/s unambiguously, which is the typical maximum speed of a small drone. The experiments were conducted using a human being and a car as targets since a drone was not available. The radar managed to detect the human target at a range of 150 m with a reduced transmitter power level. A car was used to test radial velocity performance of the radar. The car was moving with a velocity of 22 m/s and was successfully detected by the radar. It was discovered that the B210 induces a phase drift on the results which causes a Doppler shift. The phase drift was resolved by creating a phase equalisation matrix, which was used to correct the phase drift in real-time.