A Study on 23-GHz Low-Phase-Noise VCO with Transformer Output

In this paper, the combination of the tank circuit inductor and the output inductor for 23-GHz LC-VCO has been studied to obtain high output power and low phase noise under low power consumption. To investigate it, the three kinds of transformers were studied. The configurations of the metal usage were M6+M3 vs. M5+M4 (Trans1), M6+M4 vs. M5 (Trans2), and M6 vs. M5 (Trans3), which indicated “tank circuit inductor” vs. “output inductor”. Under the conditions of this study, the inductance of the inductor by a metal stack structure varied significantly, exerting a substantial influence on its Q value. The results showed that the lowest phase noise was −121.4 dBc/Hz at an output power of −3.7 dBm with 9.3 mW power consumption and the FOM was 199.2 dB for VCO with Trans3. The process technology used in this study was 180–nm CMOS