An active quasi-circulator with a passive linear TX-path for 77-GHz automotive FMCW radar systems in SiGe technology
Sprache des Titels:
Microwaves for Intelligent Mobility (ICMIM), 2015 IEEE MTT-S International Conference on
An active quasi-circulator (QC) for transmit (TX) and receive (RX) signal separation in monostatic FMCW 77-GHz radar transceivers is presented with special emphasis on linear behavior in the TX-path. To increase the compression point in the TX-path, the conventional structure of an active QC circuit is modified. A transformer is used to transfer the transmit power to the antenna, which performs DC decoupling at the antenna
port at the same time. The circuit is implemented in a 200-GHz fT Silicon-Germanium (SiGe) HBT technology and measured onwafer. Since there is no active device in the TX-path, there is no compression of the transmitted signal, which has been verified up to 10dBm input power. The TX/RX isolation is maintained independent of the transmit power. The measured return loss at 77 GHz is below 10 dB at each port, whereas the transmission parameter for the TX signal and RX signal are -7.2 dB and
2.7 dB, respectively. The TX/RX isolation is about 23 dB over a bandwidth of 8 GHz.