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Design of an X-Band CMOS VCO with a Transformer-Coupled and Transconductance-Boosted Stacked Topology
(2026-06-01)
Peng, Yen Ying
;
Li, Syu Bin
;
Wang, Sen
;
Pakasiri, Chatrpol
This paper presents the design and implementation of an X-band voltage-controlled oscillator (VCO) fabricated in a standard 180-nm CMOS process. To sustain stable oscillation under a constrained power budget, a gm-boosted topology is employed, integrating vertically stacked cross-coupled transistors with a center-tapped transformer to enhance the equivalent negative conductance. The boosting is achieved through two complementary mechanisms: the center-tapped transformer performs an impedance transformation that repurposes the layout parasitic capacitances into transconductance-enhancing elements, while the stacked cross-coupled pair reuses the DC current and suppresses the source-degeneration of a conventional pair, jointly sustaining a robust start-up margin at a low 0.75 V supply. On-wafer measurement results demonstrate a frequency tuning range from 8.78 GHz to 9.13 GHz as the control voltage is swept from 0 V to 1.8 V, with an average VCO gain K<inf>VCO</inf> of 447.5 MHz/V. Under a total DC power consumption of 6.9 mW, the oscillator delivers an output power of 4.54 dBm and exhibits a measured phase noise of −103 dBc/Hz at a 1-MHz offset.
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Differential Phase Coupler Using Balun-Type Power Divider
(2025-05-01)
Pakasiri, Chatrpol
;
Chang, Chung Yu
;
Wang, Sen
This paper presents a differential phase coupler design methodology in the IPD process. The coupler consists of a balun and two phase-shifter circuits. The compact balun was designed with lumped components and a common inductor. Each output of the balun circuit was connected to a phase shifter with an opposite phase to make a desired output phase. In the design example, a three-port 90-degree hybrid coupler was implemented on the IPD process to operate at the 6 GHz WIFI frequency. The post-simulation showed that all reflection coefficients were below −19 dB, with an insertion loss of 1.76 dB and isolation of 20 dB. The core chip size was only 0.02λ<inf>0</inf> × 0.018λ<inf>0</inf>.
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Two CMOS Wilkinson Power Dividers Using High Slow-Wave and Low-Loss Transmission Lines
(2024-08-01)
Pakasiri, Chatrpol
;
Teng, Wei Sen
;
Wang, Sen
This work presents two Wilkinson power dividers (WPDs) using multi-layer pseudo coplanar waveguide (PCPW) structures. The PCPW-based WPDs were designed, implemented, and verified in a standard 180 nm CMOS process. The proposed PCPW features high slow-wave and low-loss performances compared to other common transmission lines. The two WPDs are based on the same PCPW structure parameters in terms of line width, spacing, and used metal layers. One WPD was realized in a straight PCPW-based layout, and the other WPD was realized in a meandered PCPW-based layout. Both the two WPDs worked up to V-band frequencies, as expected, which also demonstrates that the PCPW guiding structure is less susceptible to the effects of meanderings on the propagation constant and characteristic impedance. The meandered design shows that the measured insertion losses were about 5.1 dB, and its return losses were better than 17.5 dB at 60 GHz. In addition, its isolation, amplitude imbalance, and phase imbalance were 18.5 dB, 0.03 dB, and 0.4°, respectively. The core area was merely 0.2 mm × 0.23 mm, or 1.8 × 10−3λ<inf>o</inf>2.
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A Compact 0.73~3.1 GHz CMOS VCO Based on Active-Inductor and Active-Resistor Topology
(2024-06-01)
Pakasiri, Chatrpol
;
Hsu, Ke Chung
;
Wang, Sen
In this paper, a wideband VCO that covers popular Long-Term Evolution (LTE) 0.7 GHz and LTE 2.6 GHz frequencies is designed and developed in a standard 0.18 μm CMOS process. The VCO utilizes active inductors to achieve coarse-tuning of the inductance and a compact chip area. Moreover, an active feedback resistor is introduced into the active inductor for fine-tuning of the inductance. The feedback resistor also affects the equivalent resistance of the active inductor; therefore, wide inductance tuning and low power consumption can be obtained by optimizing the resistor. The core area of the fabricated CMOS chip is merely 0.046 mm2, excluding all testing pads. With a 6.7~10.1 mW DC consumption, the measured oscillation frequencies range from 0.73 GHz to 3.1 GHz, which demonstrates a 123.8% tuning range. At the frequencies of interest, the measured phase noises are from −80.7 to −84.5 dBc/Hz at a 1 MHz offset frequency.
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A 10 GHz Compact Balun with Common Inductor on CMOS Process
(2023-01-01)
Pakasiri, Chatrpol
;
Xu, Jian Long
;
Wang, Sen
This paper presents a compact balun with a common inductor design. The design used Wilkinson-type balun topology with modified lumped transmission lines and a common inductor to realize circuit size reduction on a lossy CMOS process. Measurements of the prototype chip had a reflection coefficient below 17.8 dB at all ports, an insertion loss of 1.98 dB, and an isolation of 16.8 dB. The chip size was only 0.025λ<inf>0</inf> × 0.034λ<inf>0</inf>.
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Modified Class-F power amplifier design with fundamental frequency output impedance load
(2021-04-01)
Pakasiri, Chatrpol
;
Manasummakij, Prateep
;
Wang, Sen
A modified Class-F power amplifier with medium output power at 433 MHz was designed, simulated and implemented in this paper. The design process used a load condition of 1) output impedance of the amplifier at the fundamental frequency, 2) short-circuit loads at the even harmonics and 3) open-circuit loads at the odd harmonics. By biasing the circuit to be a typical Class-F, the circuit yielded moderate efficiency as the load condition was different from the optimum one. By strongly biasing the circuit toward that of Class-A, the load condition approached the optimum, but the circuit still yielded moderate efficiency due to the low efficiency nature of a Class-A amplifier. By proper choice of the operating point in Class-AB, a prototype circuit, with 9 dBm input power, yielded a maximum PAE of 68.5% with output power 21.8 dBm. Furthermore, at 11 dBm input power, the prototype yielded a better PAE 79.6% with 23.2 dBm output power. Our design procedure did not need expensive load-pull equipment.
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A low-phase-noise and low-power CMOS colpitts VCO using Gm boosting and capacitance switching techniques
(2021-01-01)
Pakasiri, Chatrpol
;
You, Jia Hao
;
Wang, Sen
This letter presents a low-power and low-phase-noise 5-GHz VCO fabricated in a standard CMOS 0.18-μm process. The low power dissipation was achieved by using the PMOS cross-coupled pair and G<inf>m</inf>-boosting topology, and the low phase noise was obtained by adding two pairs of switched capacitor array. The VCO consumed a dc power of 2.92 mW with the supply voltage of 1 V. The measured phase noises were − 104.6 dBc/Hz and − 117.4 dBc/Hz at 1 MHz offset frequency with switched off and on capacitances, respectively, which demonstrated 12.8-dB improvement.
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Compact Wilkinson Power Divider with Common Inductor on the IPD Process
(2021-01-01)
Pakasiri, Chatrpol
;
Wang, Sen
This paper presents a Wilkinson power divider using a common inductor. The lumped topology uses the inherently inductive loss of the inductor as a part of the design, so the conventional resistor for high isolation can be omitted. Therefore, low-loss and high-isolation performances of the compact circuit were achieved. The proposed 2.5-GHz divider was implemented on a silicon-based integrated passive device process. Measurement of the prototype chip had a reflection coefficient below 18 dB at all ports, an insertion loss of 0.5 dB and isolation above 28 dB. The chip size is merely 0.011λ o× 0.019λ o.
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Compact Wilkinson Power Divider Using Composite Right/Left-Handed Transmission Line on CMOS Process
(2020-03-01)
Nithiporndecha, Kittipong
;
Wang, Sen
;
Pakasiri, Chatrpol
This paper shows the design and analysis of CMOS Wilkinson power divider using composite right/left-handed transmission lines. The effects of lossy components in the circuit are also analyzed. The circuit is then implemented on a 0.18-μm CMOS process. The return losses are less than -16 dB, the isolation is better than -26 dB, and the insertion losses are better than -5.15 dB at the frequencies of interest. Its chip size is 0.5 mm2 (9.9e-5λ<inf>o</inf>2) including testing pads.
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Dual-band compact wilkinson power divider using common inductor and complex load
(2020-01-01)
Pakasiri, Chatrpol
;
Wang, Sen
A 1.8/2.4-GHz dual-band compact Wilkinson power divider was designed and implemented using an integrated passive device process. The design used a common inductor to match impedance in the even mode. The common inductor replaced two shunt inductors in the circuit so the circuit size was reduced. An additional complex load was then used for matching impedance in the odd mode. The circuit measurements showed reflection at all ports better than -11.9 dB, isolation at the output ports better than -14 dB and transmission coefficient better than -4.3 dB, at both operating frequencies. The circuit occupied only only 0.036λο λ0.018λο at the higher operating frequency at the higher operating frequency.

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