Design and implementation of a low-cost FMCW imaging radar

Master Thesis


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University of Cape Town

Imaging radar systems have been predominantly developed using a coherent pulse radar approach, which is typically associated with expensive and complex hardware that usually requires a large amount of space. Hence, the use of such sensors is reserved to large organizations that can afford to purchase or develop them. This is unfortunate as there are numerous uses for imaging radar sensors in both military and civilian sectors. One of such uses lies in the agricultural sector and entails using imaging radar data to monitor crop development. As a result, a project was initiated at the University of Cape Town (UCT), in collaboration with droneSAR company, which aimed to develop a low-cost, compact, imaging radar that could be mounted on a small Unmanned Aerial Vehicle (UAV). The purpose of this research project is aimed at developing the first system prototype. The RadioCamera-S is the S-band FMCW radar, that was developed to test the architecture that could be utilised to enable the filtering of the feed-through and nadir components, which are typically the strongest returns in the spectrum. The prototype has two modes of operation that are aimed at shifting the unwanted signals outside of the pass band of the receiver. This is achieved by generating two identical L-FMCW waveforms that are offset by a chosen time period. This enables a shift of the spectrum by the frequency, which corresponds to the time offset. The capabilities of the proposed hardware were examined and the specifications for the ground based version were developed. The parameters that influence the wave-form design were discussed and the optimal values were chosen for the ground based radar system. Verification of the transmitter and receiver operation was carried out, which was followed by system tests that demonstrated that the feed-through signal could be attenuated by employing the first proposed mode of operation. RTI plots were generated and showed that the radar was capable of detecting the movement of a reflector in the observable scene.