DC-Offset Compensation Concept for Monostatic FMCW Radar Transceivers

A novel dc-offset compensation technique for monostatic frequency-modulated continuous-wave (FMCW) transceivers is presented. This approach uses the intermediate frequency (IF) port of the active direct-conversion mixer to access its collector resistors. Additional external variable resistors in parallel connection can vary the total load resistance in each branch and hence compensate or generate a dc-offset voltage at the output. Since the wiring is located on the low-frequency side of the mixer, the variable resistors can also be external (off-chip), which offers great flexibility and eases application. The concept was successfully tested with an integrated 77 GHz automotive radar mixer fabricated in a 200 GHz
$f_{T}$
Silicon Germanium (SiGe) bipolar technology.