A single-core CMOS VCO with wide tuning range and PVT robust biasing for 5G new radio applications
Abstract
This study aims to present the design and implementation of a single-core CMOS Voltage-Controlled Oscillator (VCO) intended for 5G New Radio (5G NR) sub-6 GHz applications, focusing on achieving a wide tuning range, low phase noise, low power consumption, a stable performance under process, voltage and temperature (PVT) variations. Fabricated in 180 nm CMOS technology, the proposed VCO uses a differential LC resonator with a co-designed accumulation-mode MOS (A-MOS) varactor tuning network. A co-tracking PVT stabilized bias circuit is introduced, combining feedback attenuation, current-ratio co-tracking and low-pass bias filtering to maintain a stable tail current. This approach suppresses amplitude-to-phase (AM-PM) conversion, minimizes phase noise degradation across the tuning range and stabilizes oscillation amplitude across varying operating conditions. The design is optimized to cover the 5G NR n78 band and is validated through both simulation and measurement. The fabricated VCO achieves a continuous tuning range from 3.11 GHz to 3.96 GHz (24.05%), exceeding both the lower and upper boundaries of the 5G NR n78 band, thereby providing sufficient frequency headroom for robust operation under practical variations. The VCO achieves a measured phase noise of −120.4 dBc/Hz at 1 MHz offset and a Figure of Merit (FoM) of −181.49 dBc/Hz while consuming 9.75 mW from a 1.5 V supply. Measurements from 25 fabricated samples demonstrate consistent oscillation amplitude and robust performance PVT variations, confirming the effectiveness of the proposed biasing strategy. The proposed VCO introduces a co-tracking PVT-stabilized bias architecture that enhances robustness without relying on complex circuit or switching technique designs. By directly addressing bias-induced instability and AM to PM conversion, the design achieves a balanced tradeoff among tuning range, phase noise, power consumption and circuit simplicity, making it compatible for compact and reliable 5G NR transceiver applications.