Differential Coupler Topologies for Built-In Self-Test of SiGe Automotive Radar Transceivers
Yannick Wenger, Herman Jalli Ng, Falk Korndorfer, BERND MEINERZHAGEN, Вадим Іссаков · 2022
This paper presents two differential directional coupler topologies for millimeter-wave built-in self-test (BIST) in the 76 GHz to 81 GHz automotive radar band. One structure is weakly-coupled with a coupling factor (CF) of 21.5 dB, which corresponds to a minimal insertion loss of only 0.3 dB in the signal path under test. The second structure features a tighter coupling of 9.6 dB with an insertion loss around 2 dB. Measured sample-to-sample and frequency variation of the coupling factor are below 0.8 dB for the weakly-coupled and 0.2 dB for the tightly-coupled topology, facilitating accurate power measurement in the BIST. To minimize BIST overhead, the area footprint is kept compact. A generic approach to layout ensures that the couplers can be re-used in various parts of the circuit under test to minimize design time.