A 4.4-GHz 193.2-dB FoM 8-Shaped-Inductor Based LC-VCO Using Orthogonal-Coupled Triple-Coil Transformer

• Published in: IEEE transactions on circuits and systems. II, Express briefs Vol. 69; no. 10; pp. 4028 - 4032
• Main Authors: Sun, Yaqian, Deng, Wei, Jia, Haikun, Wang, Zhihua, Chi, Baoyong
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.10.2022; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: 8-shaped coil; area saving; Coils; Filtration; high FOM; Inductance; Inductors; Metals; noise filtering; Phase noise; Resistors; Thermal noise; Transformers; Varactors; VCO; Voltage-controlled oscillators; Wires
• ISSN: 1549-7747; 1558-3791
• DOI: 10.1109/TCSII.2022.3186304

A 4.2-to-4.6 GHz 8-shaped-inductor based LC-VCO with an orthogonal-coupled triple-coil transformer is presented in this brief. The orthogonal-coupled triple-coil transformer is designed to reduce magnetic coupling and improve phase noise. The mutual inductance between the 8-shaped inductor and the tail-filtering inductor is negligible due to the symmetrical and reversal magnetic field generated by the two loops of the 8-shaped inductor, which avoids the additional chip area occupation of the bulky tail-filtering inductor. In addition, an 8-shaped transformer with thin line width is proposed to bias the varactor instead of using resistors, which avoids the resistor thermal noise contribution. The VCO is implemented in a 180 nm CMOS process, which consumes 7.4 mA current from a 1 V power supply. By adopting the 8-shaped inductor with noise filtering and noise-free biasing technique from the orthogonal-coupled triple-coil transformer, the measured phase noise achieves −149.3 dBc/Hz at 10 MHz offset away from a 4.3 GHz carrier and the resulting figure-of-merit (FoM) is −193.2 dB. To the best knowledge of the authors, this brief presents the VCO with the best FoM among published 8-shaped-inductor based LC-VCOs.