Active Backscatter Transponder for FMCW Radar Applications

This letter presents a low-cost wideband active backscatter transponder at X-band suitable for frequency-modulated continuous-wave (FMCW) radar applications. In order to maximize its read range, the radar cross section (RCS) of the transponder is increased by means of a two-stage amplifier based on high electron mobility transistors (HEMT), which is connected between two (one receiver and one transmitter) bowtie antennas. To distinguish the transponder response from stationary clutter it modulates the level of its RCS modifying the bias of the transistors. The backscattered response of the transponder is collected using a FMCW commercial radar. The transponder achieves a bandwidth of 7-12 GHz, with a gain between 18-22 dB, and a power consumption of 75 mW. Theoretical operation and experimental results are presented.