Elsevier

Microelectronics Journal

Volume 54, August 2016, Pages 32-39
Microelectronics Journal

Design of low phase noise CMOS VCO using cross coupled topology with capacitor feedback

https://doi.org/10.1016/j.mejo.2016.05.005Get rights and content

Abstract

In this paper, a new structure for a capacitor feedback with quality factor enhancement of 5 GHz band CMOS VCO is presented. The proposed VCO was able to reduce the parasitic effect of the circuit at high frequencies and without additional body biased voltage. The phase noise was improved with this capacitor feedback circuit. The circuit was analyzed by means of a simplified high frequency model. The improvement of low power consumption resulted from the adopted self-body biased technology without additional body biased voltage. The optimal low voltage design with 0.8 V was determined as the aim for low phase noise. The measured bandwidth of the frequency was from 5.07 GHz to 6.2 GHz with a 20.37% tuning ratio. The core consumption was 2.8 mW from the 0.8 V supply. The phase noise of the proposed VCO was −117.34 dBc/Hz at an offset frequency of 1 MHz. The figure of merit was −187.45 dBc/Hz and the figure of merit with tuning range (FOMT) was −193.6 dBc/Hz.

Introduction

In wireless communication systems, the receivers or transmitters have a local oscillator, which generates the required high-frequency carrier for amplitude modulation, phase modulation and frequency modulation. As consumers prefer low-cost wireless communication products, as well as continuity and portability, the development of wireless communication front-end circuits has focused on small size, low power and high-performance features.

In the recent five years, there has been greater progress on voltage controlled oscillator architectures and techniques. Cross-coupled topology compared with colpitts oscillation can provide more negative resistance for speed-up oscillation and stability [1], [2], [3]. Transformer feedback topology can easily achieve high performance (i.e., low voltage and low power; however, it needs a large area for inductor design [4], [5], [6]. Body-biased techniques [7], [8], [9], [10] and current-reused topology [11], [12], [13], [14], [15], [16] are always used for low power application, but body-biased circuitry needs additional voltage. Capacitor feedback topology [17], [18], [19] which can increase the Q-factor has reduced the level of phase noise. How to make the operation of the radio frequency integrated circuits (RFICs) with low power consumption is an area that is currently being researched. The best choice for a VCO design comes with trade-offs.

In this study, a new circuit based on cross-coupled topology with capacitor feedback was developed with low voltage and low power operation for the proposed VCO. This research still used the 0.18 μm process technology but also included a new architecture of oscillator circuits designed to achieve low phase noise at an optimum voltage where the core current can be reduced and high performance of the circuit maintained.

The paper is organized as follows. Section 2 discusses the proposed VCO topology, circuit analysis and design flow. Circuit measurement results are shown in Section 3. The paper ends with a conclusion in Section 4.

Section snippets

Proposed VCO topology

The proposed VCO design concept is shown in Fig. 1(a)–(d). Fig. 1(a) is a typical NMOS cross-coupled VCO. The oscillator frequency is determined by the passive element of inductor L and varactor Cvar. The passive circuit also shows some loss at the high frequency end. Transistors M1 and M2 are cross-coupled active circuits that are designed to generate negative resistance for the lost compensation of the LC tank. Fig. 1(b) is an NMOS cross-coupled VCO with capacitor (Non feedback) which can

Measurement results

The proposed VCO is fabricated by means of TSMC 0.18 um 1P6M CMOS technology. Fig. 9, shows the die micrograph of the proposed low phase noise VCO, which had a chip area of 789.1×636.2 um2 including the RF pads. The buffer with 50 Ω matching for measurement is also included as the block. Fig. 10 shows the output spectrum which had an operating frequency of 5.368 GHz with −5d Bm peak value. Fig. 11 shows the tuning ranges of the oscillation frequency versus varactor controlled voltage (Vtune) which

Conclusion

This paper shows a new circuit based on capacitor feedback and body biased technology. Capacitor feedback is a function to enhance the quality factor of the circuit. Moreover, the body biased technique is a function that can reduce the supply voltage and also reduce the power consumption. Measurement results showed that the phase noise −117.34 dBc/Hz at 1 MHz offset frequency and output power was about −5 dBm. The measured tuning range was about 20.37% from 5.07 GHz to 6.2 GHz and the power

Acknowledgment

The authors would like to thank the Taiwan Semiconductor Manufacture Company (TSMC) and National Chip Implementation Center (CIC) for the wafer fabrications and IC measurement. This project was partly supported by National Science Counsel (NSC), Taiwan. NSC 100-2221-E-224-072.

Meng-Ting Hsu was born in Changhua, Taiwan, R.O.C. in 1961. He received his B.S. and M.S. degrees from Chung-Yuan Christian University in the Electrical and Electronic Engineering in 1989 and 1991, respectively. Since 1992 he has served as a lecturer in the Electronic Department of National Yunlin University of Science & Technology (NYUST), And he later obtained a Ph.D. degree from National Chiao-Tung University in Communication Engineering in 2004. In 2005, he was promoted to associate

References (24)

  • Meng-Ting Hsu et al.

    Design of sub-1 mW Q-enhancement CMOS LC VCO with body-biased technique

    Microelectron. J.

    (2014)
  • T. Tuan Thanh, et al., A 5GHz band low noise and wide tuning range Si-CMOS VCO, in: Radio Frequency Integrated Circuits...
  • Young-Jin Moon et al.

    A 4.39–5.26 GHz LC-tank CMOS voltage-controlled oscillator with small VCO-gain variation

    Microw. Wirel. Comp. Lett. IEEE

    (2009)
  • Sheng-Lyang Jang

    A 0.3 V cross-coupled VCO using dynamic threshold MOSFET

    Microw. Wirel. Comp. Lett. IEEE

    (2010)
  • J. Sheng-Lyang

    A 5.6 GHz low power balanced VCO in 0.18 um CMOS

    Microw. Wirel. Comp. Lett. IEEE

    (2009)
  • Tzuen-Hsi Huang et al.

    A 1 V 2.2 mW 7 GHz CMOS quadrature VCO using current-reuse and cross-coupled transformer-feedback technology

    Microw. Wirel. Comp. Lett. IEEE

    (2008)
  • Guansheng Li et al.

    A low-phase-noise wide-tuning-range oscillator based on resonant mode switching,” in solid-state circuits

    IEEE J.

    (2012)
  • Meng-Ting Hsu, Po-Hung Chen, 5GHz low power CMOS LC VCO for IEEE 802.11a application, in: Microwave Conference...
  • Szu-Ling Liu

    A low-power K-band CMOSVCO with four-coil transformer feedback

    Microw. Wirel. Comp. Lett. IEEE

    (2010)
  • S. Jain et al.

    Indirect back-gate coupling quadrature LC-VCO

    IEEE Microw. Wirel. Comp. Lett.

    (2014)
  • L. Fanori, A. Mahmoud, T. Mattsson, P. Caputa, S. Ramo, P. Andreani, A 2.8–5.8GHz harmonic VCO in a 28nm UTBB FD-SOI...
  • Wenrong Ying, et al., A 1mW 5GHz current reuse CMOS VCO with low phase noise and balanced differential outputs...
  • Cited by (0)

    Meng-Ting Hsu was born in Changhua, Taiwan, R.O.C. in 1961. He received his B.S. and M.S. degrees from Chung-Yuan Christian University in the Electrical and Electronic Engineering in 1989 and 1991, respectively. Since 1992 he has served as a lecturer in the Electronic Department of National Yunlin University of Science & Technology (NYUST), And he later obtained a Ph.D. degree from National Chiao-Tung University in Communication Engineering in 2004. In 2005, he was promoted to associate professor and has more than ten years experience in microwave circuit design. His current research interests are in noise theory application on MMIC and CMOS RFICs. He is also active on RF UWB design. He served as a vice dean of Electronic Department of NYUST from August, 2011. Now he is a professor from August, 2014.

    Wei-Jhih Li was born in Taipei, Taiwan, R.O.C. in 1982. He received the B.S. and M.S. degree in electrical engineering from Nan Jeon Institute & Technology (NJIT), National Yunlin University of Science & Technology (NYUST) in 2005 and 2007, respectively. And he pursues a Ph.D of National Yunlin University of Science & Technology (NYUST) in electric engineering from 2007. His present research interests in CMOS RFICs and MMIC.

    Shuo-Chang Hsu was born in Nantou, Taiwan, R.O.C. in 1988. He received a B.S. degree in Electrical Engineering from National United University in 2010. Then, he obtained an M.S. degree from National Yunlin University of Science & Technology (NYUST) in Electronic and Optoelectronic Engineering in July 2012. His present research interests are in RF integrated circuit design.

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