A Compact 77 GHz IQ-Modulated Transponder for High Gain and High Dynamic Range Radar Target Simulation

This paper explores the concept and design of a transponder for radar target simulators (RTSes) within the 77 GHz automotive radar band. The modulator is based on PIN diode attenuators arranged in an IQ configuration with additional amplification. Novel design strategies and components were implemented and evaluated during the design process. The layout is based on circular waveguide elements and the RF phase can be tuned even after fabrication. In addition, the signal can be varied for modulation by 28 dB using an additional tuning range of 24 dB for the gain setting. The usable RF bandwidth ranges over 10 GHz centered at 80 GHz, whereas the modulation bandwidth is set to 10 MHz via the implemented filter characteristic of the driving circuit. This covers the relevant range of automotive radars operating at 77 GHz.