Design and Investigation of Wide Frequency Tuning Range Millimeter-Wave Voltage Controlled Oscillators (VCO) in 65nm CMOS Technology

  • Author / Creator
    Basaligheh, Ali
  • The available unlicensed spectrum in millimeter-wave (mm-wave) frequencies has been a very attractive candidate for high data rate wireless communications, high-resolution radars, and imaging applications. Voltage-controlled oscillators (VCO), which are essential building block of tunable multi-standard mm-wave transceivers or ultra-wideband radar front-ends, should provide a wide frequency tuning range (FTR), a low phase noise (PN), a low power consumption, and a low fabrication cost (i.e., small silicon area). For wideband radar applications and multi-standard wireless communication often a large FTR is required to achieve the desired resolution and communication data rates, respectively. In addition, because of the process and temperature variations in practical applications, more than allocated FTR is usually required to consider in design of single-standard mm-wave communication systems (e.g. 15% for 60 GHz). This thesis introduces new circuit architectures of mm-wave VCOs providing wide FTR and low phase noise circuits in a standard CMOS process. First, a millimeter-wave wide tuning range voltage controlled oscillator incorporating two switchable decoupled VCO cores is introduced. When the first core is switched on producing the low-frequency band (LFB) signal and the second core is off, the inductors of the second core are reused to create additional buffers that pass the LFB signal to the output buffers. The generated high-frequency band (HFB) signals by the second core when turned on, are directly fed to the output buffers. Producing the outputs of both VCO cores across the same terminals without utilizing active/passive combiners and coupled inductors will enhance the PN performance of the VCO, increase its output power, and reduce the chip size. Fabricated in a 65 nm CMOC process, the VCO achieves a measured wide tuning range of 26.2% from 54.1 to 70.4 GHz while consuming 7.4-11.2 mA current from 1 V power supply. The peak measured phase noise at 10 MHz offset is -116.3 dBc/Hz and the corresponding FOMT and FOM varies from -180.96 to -191.86 dB and -172.6 to -183.5 dB, respectively. The VCO core area occupies only 0.1 ×0.395 mm2. Second, a wide-tuning range dual-mode mm-wave VCO incorporating high quality-factor (Q) transformer-based variable inductors is presented. A high Q switched inductor with two different values is proposed by constructing the load of a transformer of a high Q fixed capacitor in series with a lossless switch structure that does not add any loss to the LC-tank as implemented by changing the signals mode across the capacitor. By choosing a proper center frequency for each mode and sufficient frequency overlap, a wide FTR mm-wave VCO can be designed. It provides almost twice higher tuning range while keeping PN nearly the same as the two-mode VCO designed with two standalone inductors. Fabricated in a 65 nm CMOS process, the VCO demonstrates the measured FTR of 22.8% from 64.88 to 81.6 GHz range. The measured peak PN at 10 MHz offset is -114.63 dBc/Hz and the maximum and minimum corresponding figures of merit FOM and FOMT are -181.07 to -189 dB and -173.9 to 181.84 dB, respectively. The VCO cores consume 10.2 mA current from 1 V power supply, and the occupied area is 0.146 ×0.205 mm2.

  • Subjects / Keywords
  • Graduation date
    Fall 2019
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • License
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