An evolution of Colpitts VCO for simultaneous optimization of phase noise and FoM in GaAs technologies
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An evolution of Colpitts VCO for simultaneous optimization of phase noise and FoM in GaAs technologies Jing-Yu Han1,2 • Yu Jiang1,2 • Gui-Liang Guo1,2 • Xu Cheng3,4 Received: 21 April 2020 / Revised: 13 July 2020 / Accepted: 26 September 2020 Ó Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract This paper presents a novel co-optimization configuration to simultaneously improve phase noise and FoM in order to solve the long-existing issue of excellent phase noise and mediocre FoM in the light of GaAs technologies. Considering traditional GaAs based Colpitts/class-C VCOs, a first step is taken with the introduction of noise shifting structure while a second step is carried out with the presentation of Darlington pair. Afterwards, a detailed outline of pros and cons of five VCO topologies, including Colpitts/class-C/noise shifting (NS) Colpitts/noise shifting class-C/noise shifting Darlingtonbased (NSDB) class-C VCO, is given in theory and in practice while respective start-up conditions and capacitive feedback factors are derived mathematically. It can be found that iterative phase noise and FoM improvement is achieved in GaAs based VCOs above in a gradual manner. Furthermore, the output power is stabilized with a simple trick of two-stage Darlington-based topology and thus, the power-hungry buffer is avoided. Ultimately, three VCOs out of the five are fabricated in GaAs technologies while their specifications are thoroughly compared with previous research. The fabricated Colpitts VCO demonstrates a frequency tuning range of 3.59–3.69 GHz with a current consumption of 11.2 mA@5 V supply, a phase noise of - 130.1 to - 129.1 dBc/Hz at 1 MHz offset from the carrier and the output power is around - 5 to - 5.1 dBm. The fabricated noise shifting Colpitts VCO demonstrates a frequency tuning range of 3.58–3.67 GHz with a current consumption of 10.8 mA@5 V supply, a phase noise of - 132.4 to - 130.2 dBc/Hz at 1 MHz offset from the carrier and the output power is around - 2.5 to - 3.5 dBm. The fabricated Darlington-based class-C VCO demonstrates a frequency tuning range of 2.76–2.91 GHz with a current consumption of 9.5 mA@5 V supply, a phase noise of - 138.6 to - 135.9 dBc/Hz at 1 MHz offset from the carrier and the output power is around - 3.06 to - 4.18 dBm. To the best of the authors’ expertise, the proposed Darlington-based class-C VCO achieves both exceptional phase noise and FoM, which far outweigh that of existing GaAs ones. Keywords Colpitts VCO Noise shifting Class-C VCO Darlington GaAs technology
1 Introduction
& Xu Cheng [email protected] 1
Institute of Microelectronics, Chinese Academy of Sciences, Beijing, China
2
University of Chinese Academy of Sciences, Beijing, China
3
Institute of Electronic Engineering, China Academy of Engineering Physics, Mianyang, China
4
Microsystem & Terahertz Research Center, China Academy of Engineering Physics, Chengdu, China
As a pivotal block in local oscillator (LO) chain and signal generation modules, VCOs have long been investigated
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