J. Semicond. > 2015, Volume 36 > Issue 3 > 035003
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SEMICONDUCTOR INTEGRATED CIRCUITS

A 3.16—7 GHz transformer-based dual-band CMOS VCO

Zhu Li1, 2, Zhigong Wang1, , Zhiqun Li1, Qin Li1 and Faen Liu1

+ Author Affiliations

 Corresponding author: Zhigong Wang, E-mail: zgwang@seu.edu.cn

DOI: 10.1088/1674-4926/36/3/035003

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Abstract: A dual-band, wide tuning range voltage-controlled oscillator that uses transformer-based fourth-order (LC) resonator with a compact common-centric layout is presented. Compared with the traditional wide band (VCO), it can double frequency tuning range without degrading phase noise performance. The relationship between the coupling coefficient of the transformer, selection of frequency bands, and the quality factor at each band is investigated. The transformer used in the resonator is a circular asymmetric concentric topology. Compared with conventional octagon spirals, the proposed circular asymmetric concentric transformer results in a higher quality-factor, and hence a lower oscillator phase noise. The VCO is designed and fabricated in a 0.18-μm CMOS technology and has 75% wide tuning range of 3.16—7.01 GHz. Depending on the oscillation frequency, the VCO current consumption is adjusted from 4.9 to 6.3 mA. The measured phase noises at 1 MHz offset from carrier frequencies of 3.1, 4.5, 5.1, and 6.6 GHz are —122.5, —113.3, —110.1, and —116.8 dBc/Hz, respectively. The chip area, including the pads, is 1.2 × 0.62 mm2 and the supply voltage is 1.8 V.

Key words: CMOS, phase noise, voltage-controlled oscillator (VCO), wideband, transformer



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Fig. 1.  Transformer-based LC tank. (a) Equivalent circuit. (b) The amplitude-frequency response of the tank.

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Fig. 2.  Model of one-port dual-band oscillator.

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Fig. 3.  The dependence of $\omega_{\rm L}$/$\omega_{1}$, $\omega_{\rm L}$/$\omega_{2}$, $\omega_{\rm H}$/$\omega_{1}$ and $\omega_{\rm H}$/$\omega_{2}$ on the coupling factor ($k)$ and the ratio of the resonance frequencies of the uncoupled tank($\xi$ $=$ $\omega_{2}$/$\omega$

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Fig. 4.  The magnitude and phase responses of $Z_{11}$ and $Z_{22}$.

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Fig. 5.  (a) The transconductance ratio $\alpha_{1}$ versus $\xi$ and $k$. (b) The transconductance ratio $\alpha_{2}$ versus $\xi$ and $k$.

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Fig. 6.  Schematic of the one-port dual-band wide tuning range VCO.

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Fig. 7.  Layout of the transformer.

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Fig. 8.  The coupling coefficient $k$ of the transformer.

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Fig. 9.  The inductance of $L_{1}$ and $L_{2}$ of the transformer.

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Fig. 10.  The quality factor $Q_{1}$ and $Q_{2}$ of the transformer.

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Fig. 11.  (a) The proposed cross-connected pair. (b) Small-signal equivalent circuits of (a).

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Fig. 12.  The micrograph of the VCO.

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Fig. 13.  The frequency spectrum of the VCO.

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Fig. 14.  Phase noise of the VCO.

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Fig. 15.  Phase noise measurements at 3.16, 4.55, 5.14, and 6.6 GHz.

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Table 1.   Comparison of the performances for the currently published VCOs.

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    Received: 31 August 2014 Revised: Online: Published: 01 March 2015

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      Article Navigation >  Journal of Semiconductors  > 2015  >  36(3): 035003
      Zhu Li, Zhigong Wang, Zhiqun Li, Qin Li, Faen Liu. A 3.16—7 GHz transformer-based dual-band CMOS VCO[J]. Journal of Semiconductors, 2015, 36(3): 035003. doi: 10.1088/1674-4926/36/3/035003 ****Z Li, Z G Wang, Z Q Li, Q Li, F E Liu. A 3.16—7 GHz transformer-based dual-band CMOS VCO[J]. J. Semicond., 2015, 36(3): 035003. doi: 10.1088/1674-4926/36/3/035003.
      Citation:
      Zhu Li, Zhigong Wang, Zhiqun Li, Qin Li, Faen Liu. A 3.16—7 GHz transformer-based dual-band CMOS VCO[J]. Journal of Semiconductors, 2015, 36(3): 035003. doi: 10.1088/1674-4926/36/3/035003 ****
      Z Li, Z G Wang, Z Q Li, Q Li, F E Liu. A 3.16—7 GHz transformer-based dual-band CMOS VCO[J]. J. Semicond., 2015, 36(3): 035003. doi: 10.1088/1674-4926/36/3/035003.
      shu

      A 3.16—7 GHz transformer-based dual-band CMOS VCO

      DOI: 10.1088/1674-4926/36/3/035003
      • 1.

        Institute of RF- & OE-ICs, Southeast University, Nanjing 210096, China

      • 2.

        Nanjing University of Science and Technology, Nanjing 210094, China

      Funds:

      Project supported by the National High Technology Research and Development Program of China (No. 2011AA10305) and the National Natural Science Foundation of China (No. 60901012).

      More Information
      • Corresponding author: E-mail: zgwang@seu.edu.cn
      • Received Date: 2014-08-31
      • Accepted Date: 2014-10-12
      • Published Date: 2015-01-25

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