A 33–39-GHz Compact Low-Power Low-PN VCO Achieving 205-dBc/Hz FOMTA with Overlapping Symmetrical Folded Tail Inductors for FMCW Radars

This paper presents a miniaturized, low-power, and low-phase-noise (PN) Ka-band voltage-controlled oscillator (VCO) tailored for FMCW radar applications. A complementary cross-coupled topology is employed to minimize the power and improve current efficiency. To enhance PN without area penalty, an overlapping symmetrical folded-tail inductor structure is introduced, effectively shortening the VDD-to-GND current return path. Furthermore, a dual-tank coupled resonator (DTCR) is utilized to isolate the parasitic capacitance of the transistors for bandwidth extension, while simultaneously realizing third-harmonic resonance to suppress flicker noise up-conversion. The VCO is fabricated in a 28-nm CMOS process and achieves a frequency tuning range of 33.3–39.3 GHz while consuming 3–3.5 mW. The PN is -99.4 dBc/Hz at 1-MHz offset. Occupying a core area of 0.03 mm², the VCO achieves an excellent figure-of-merit with tuning range and area (FoMTA) of 205 dBc/Hz.