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1. A Single-Switch 3.1-4.7 GHz 194.52-dB FoM Class-D VCO With 495μW Power Consumption

   https://doi.org/10.1109/TCSII.2024.3407842  

   Liu, Xuyang ; Moradi, Behnam ; Aghasi, Hamidreza ( January 2024 , IEEE Transactions on Circuits and Systems II: Express Briefs)

   Bonizzoni, Edoardo (Ed.)

   This brief presents an ultra-low-power class-D voltage-controlled oscillator (VCO) designed for GHz applications that mandate decent phase noise performance. A waveform-centric approach of phase noise reduction by controlling the ratio between the floating and single-ended (SE) capacitors in an oscillator tank is proposed. By co-designing an RF choke with the tank inductor to introduce high impedance for the floating capacitors, the optimum capacitance ratio is maintained across the tuning range. The VCO is fabricated in 65nm Bulk CMOS technology and achieves a measured phase noise of -118.36 dBc/Hz and -138.64 dBc/Hz, and figure-of-merit of 192.89 dBc/Hz and 194.52 dBc/Hz at 1 MHz and 10 MHz offset frequencies, respectively. The VCO’s lowest measured 1/f3 corner is approximately 50kHz, which enables a decent figure-of-merit (FoM) down to a frequency offset of 10 kHz. The VCO features a tuning range of 40% (3.1 GHz -4.66 GHz) using a one-bit switch to realize two-point modulation in phase-locked loops (PLLs) with milliwatt-level power consumption. 

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2. A Low Phase Noise 28 GHz VCO Using Transformer-based Q-enhanced Active Impedance Converter

   https://doi.org/10.1109/IMS37962.2022.9865389  

   Hoque, Md Aminul ; Chahadori, Mohammad ; Mokri, Mohammad Ali ; Mohapatra ; Soumen Mohapatra ; Kar, Dipan ; Heo, Deukhyoun ( July 2022 , IEEE International Microwave Symposium)

   This paper presents a low phase noise 28 GHz voltage-controlled oscillator (VCO) using a transformer-based active impedance converter to enhance the quality factor (Q) of the capacitor in the resonator. The active impedance converter can enhance the Q of a capacitor bank and varactor by 25-40% across the VCO’s tuning range. The proposed VCO is fabricated using the proposed transformer-based Q-enhancement impedance converter in a standard 65 nm CMOS process. The VCO achieves a 15.9% measured fractional frequency tuning range and phase noise of −107.6 dBc/Hz at 1 MHz offset from 28 GHz oscillation frequency while occupying only 0.05 mm2 area (200 μm × 250 μm). The VCO consumes 5.1 mW power, resulting in an excellent figure-of-merit (FoM) of 189.4 dBc/Hz and a figure-of-merit-with-area (FoMA) of 202.8 dBc/Hz. 

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3. A Compact Mm-Wave Multi-Band VCO Based on Triple-Mode Resonator for 5G and Beyond

   Chahardori, Mohammad ; Hoque MD Aminul ; Mokri Mohammad Ali ; Heo, Deukhyoun Heo ( July 2022 , IEEE RFIT 2022)

   We present a low phase noise four-core triple-band voltage controlled-oscillator (VCO) with reconfigurable oscillator cores and multi-mode resonator. By activation/deactivation of oscillator cores and change of resonator impedance in three modes of operations, the proposed VCO provides complete freedom in selecting the resonance frequency for three operation bands in the mm-wave range. Compared to VCOs using switch-capacitor-bank for multi-band operation, the proposed VCO does not use any series switches with passive components in the resonator to provide a low phase noise in all three bands of operation. As a proof of concept, the proposed four-core triple-band VCO is implemented in a 65 nm CMOS process using four class-D oscillators with tail switches and a compact high-Q triple-mode resonator. The VCO oscillation frequencies center at 19, 28, and 38 GHz while providing good phase noise and low power consumption in all bands. Measured results show the total frequency tuning range (FTR) of 38.5% while the PN at 1MHz offset varies from -100.3 dBc/Hz to -106.06dBc/Hz resulting in an excellent FoMT of 199.8 dBc/Hz. 

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4. A 23.7 to 29.9 GHz Tunable Fully Differential Voltage Controlled Oscillator Designed in 180nm CMOS process

   https://doi.org/10.1109/DCAS57389.2023.10130248  

   Kakaraparty, Karthik ; Mahbub, Ifana ( April 2023 , 2023 IEEE 16th Dallas Circuits and Systems Conference (DCAS))

   This paper presents the design of a 23.7 to 29.9 GHz wide tuning range VCO (Voltage Controlled Oscillator) designed using a 180 nm CMOS process. In order to achieve a good phase noise performance and get a wide frequency tuning range, cross-coupling and gate biasing techniques are utilized in the proposed cross-coupled LC VCO architecture. The simulated phase noise of −130 dBc/Hz is achieved at a 1 MHz offset. With the supply voltage of 1.8 V, the total power consumption of the VCO is 32.04 mW. The proposed VCO has good performance in terms of low-phase noise and has a wide frequency tuning range, which makes it highly suitable for millimeter wave-based applications. 

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5. A Triple-Band, High DC-to-RF Efficiency, Multicore VCO With a Dual-Path Inductor and Mode-Switching Capacitor

   https://doi.org/10.1109/TMTT.2024.3439653  

   Hoque, Md Aminul ; Heo, Deukhyoun ( January 2024 , IEEE Transactions on Microwave Theory and Techniques)

   This article introduces an innovative four-port dual-path inductor designed to deliver two distinct inductance values to the resonator of a voltage-controlled oscillator (VCO). The switching between the inductor’s two excitation modes, even and odd, is determined by the differential excitation’s input polarity, eliminating the need for a series switch. Thus, the inductor has a high-quality factor ( Q ) in both modes. The inductances in these modes can be independently set based on desired frequencies. This inductance change achieves coarse frequency tuning, while fine-tuning is realized by a conventional 2-bit capacitor bank with a small-size varactor. This inductor is well suited for designing multiband VCOs aimed at widely spaced operation frequency bands. Apart from the inductance change, a particular case of mode-switching capacitor is employed to extend to another frequency band in between the low and middle bands, achieving triple-band oscillation. As a result, this article presents two VCOs designed using the proposed inductor: one in class-D biasing in a 65-nm CMOS process and another with class-B biasing in a 180-nm BiCMOS process. Both VCOs successfully oscillate across three distinct frequency bands, centered at 19, 28, and 36 GHz, while maintaining outstanding phase noise and minimal power consumption. Measurement results show good match with simulation, resulting in a peak figure of merit (FoM) of 185.7 dBc/Hz at 18.5 GHz, and occupy 0.088- mm2 (250 × 350 μ m) area in both processes. 

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