Design of hybrid optical delay line for automotive radar test system

In this paper, hybrid optical delay line (HODL) which is demanded on automotive radar test system (RTS) is proposed and demonstrated. HODL is composed with coaxial cable in short delay time (< 32 nsec) and optical fiber in long delay time (≥ 32 nsec) which are considering the volume, loss and frequency characteristics. Also, the optical transceiver that has the bandwidth of 1 GHz is designed for frequency modulated continuous wave (FMCW). Experimental results show that the S21 is ± 0.5 dB in the optical transceiver and ± 1.7 dB in the whole system at 3.7 GHz ~ 4.7 GHz. The resolution of delay time is 1 ns and the delay flatness is ± 0.23 ns.