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Design of a varactor-tunable metamaterial absorber

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Chinese Physics B 2014年第6期23卷 542-546页

作者：林宝勤达新宇赵尚弘蒙文李凡方英武王甲富 Institute of Information and Navigation Air Force Engineering University

In this paper, we design a varactor-tunable metamaterial absorber （MA）. The tunable MA is based on a mushroom-type high impedance surface （HIS）, in which varactors are loaded between adjacent metal patches to adjust the capacitance and tune the resonance frequency, the primary ground plane is etched as the bias network to bias all of the varactors in parallel, and another ultra-thin grounded film is attached to the bottom. Its absorption characteristics are realized for electrically dielectric loss. The simulated values of a sample indicate that a tunable frequency range from 2.85 GHz to 2.22 GHz is achieved by adjusting the varactor capacitance from 0.1 pF to 2.0 pF, and better than 0.97 absorbance is realized; in addition, the tunable frequency range is expanded from 4.12 GHz to 1.70 GHz after optimization.

关键词： metamaterial absorber （MA） high impedance surfaces （HISs） varactor

INDEPENDENTLY-TUNED CONCURRENT DUAL-BAND BRANCH-LINE COUPLER USING varactor

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Journal of Electronics(China) 2014年第4期31卷 348-353页

作者： Guo Xiaofeng Ye Yan Liu Taijun Xu Qian Li Ruiyang College of Information Science and Engineering Ningbo University

This paper presents a concurrent dual-band branch-line coupler with an independently tunable center frequency. In the proposed architecture, the quarter-wavelength lines, which work at two separated bands concurrently and can be tuned in one of them, are key components. Based on the analysis of ABCD-matrix, a novel hybrid structure and a pair of varactors topology are utilized to achieve concurrent dual-band operation and independent tunability, respectively. Using this configuration, it is convenient to tune the center frequency of the upper band, while the responses of the lower band remain unaltered. To verify the proposed idea, a demonstration is implemented and the simulated results are presented.

关键词： Branch-line coupler Concurrent dual-band varactor Independently tuned Quarter-wavelength line

A 2.4 GHz high-linearity low-phase-noise CMOS LC-VCO based on capacitance compensation

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Journal of Semiconductors 2010年第7期31卷 96-101页

作者：李振荣庄奕琪李兵靳刚靳钊 Key Laboratory of the Ministry of Education for Wide Band-Gap Semiconductor Materials and Devices School of MicroelectronicsXidian University

A 2.4 GHz high-linearity low-phase-noise cross-coupled CMOS LC voltage-controlled oscillator（VCO） is implemented in standard 0.18-μm CMOS technology.An equalization structure for tuning sensitivity base on the three-stage distributed biased switched-varactor bank and the differential switched-capacitor bank is adopted to reduce the variations of the VCO gain,achieve high linearity,and optimize the phase-noise performance.Compared to the conventional VCO,the proposed VCO has more constant gain over the entire tuning range.The tuning range is about 18.7%from 2.23 to 2.69 GHz,and the phase noise is-95 dBc/Hz at 100-kHz offset and-117 dBc/Hz at 1-MHz offset from the carrier frequency of 2.42 GHz.The power dissipation is 2.1 mW from a 1.8 V power supply.The active area of this VCO is 500×810μm^2.

关键词： switched-capacitor varactor VCO phase noise tuning range linearity

Design of a tunable frequency selective surface absorber as a loaded receiving antenna array

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Chinese Physics B 2014年第2期23卷 252-256页

作者：林宝勤赵尚弘魏伟达新宇郑秋容张衡阳朱蒙 Institute of Information and Navigation Air Force Engineering University

An effective approach to designing a tunable electromagnetic absorber is presented and experimentally verified; it is based on an idea that an existing frequency selective surface （FSS） absorber is regarded as a loaded receiving antenna array. The existing absorber is effectively simplified by withdrawing half of the loaded resistors; a more compact one is obtained when lumped capacitors are introduced. Building on this, a varactor-tunable absorber with a proper bias network is proposed. Numerical simulations of one tunable absorber with 1.6 mm in thickness show that a wide tuning range from 3.05 GHz to 1.96 GHz is achieved by changing the capacitance of the loaded varactor from 0.5 pF to 5.0 pF. An experiment is carried out using a rectangular waveguide measurement setup and excellent agreement between the simulated and measured results is demonstrated.

关键词： electromagnetic absorber frequency selective surfaces （FSS） varactor

A fully integrated CMOS VCXO-IC with low phase noise, wide tuning range and high tuning linearity

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Journal of Semiconductors 2015年第6期36卷 148-155页

作者：杨艳军曾云 School of Physics and Electronics Hunan University

This paper describes a low phase noise, wide tuning range and high tuning linearity CMOS voltage controlled crystal oscillator IC （VCXO-IC） with LVCMOS and LVPECL output. A differential coupled frequency doubling Colpitts oscillator is adopted to obtain low noise 2x frequency output. Wide tuning range and high lin- earity are simultaneously achieved by using MOS varactor arrays. The measurement results show that the designed VCXO-IC achieves -134 dBc/Hz phase noise at 1 kHz offset frequency and 4-135 ppm output frequency tuning range within 3% linearity by using 40 MHz fundamental AT-cut crystal. The VCXO-IC is fabricated in the chartered 0.35/zm standard CMOS process and occupies a total silicon area of 2.4 mm2.

关键词： VCXO varactor linear frequency tuning low phase noise

Superconducting tunable filter with constant bandwidth using coplanar waveguide resonators

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Chinese Physics B 2017年第10期26卷 472-476页

作者：蒋莹李博魏斌郭旭波曹必松姜立楠 State Key Laboratory of Low-Dimensional Quantum Physics Department of Physics Tsinghua University Department of Electronic Engineering Tsinghua University

In this paper we propose a two-pole varactor-tuned superconducting filter using coplanar waveguide （CPW） spiralin-spiral-out （SISO） resonators. Novel internal and external coupling structures are introduced to meet the requirements for a tunable filter with a constant absolute bandwidth. The fabricated device has a frequency tuning range of 14.4% at frequencies ranging from 274.1 MHz to 317.7 MHz, a 3-dB bandwidth of 5.14±0.06 MHz, and an insertion loss of 0.08 dB-0.70 dB. The simulated and measured results are in excellent agreement with each other.

关键词： coplanar waveguide （CPW） superconducting tunable filter varactor

Development and Experimental Measurements of a Tunable Antenna

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Communications and Network 2013年第3期5卷 220-224页

作者： Vasilis Raptis Giorgos Tatsis Spyridon K. Chronopoulos Stavros Mallios Panos Kostarakis Physics Department University of Ioannina Ioannina Greece

Modern telecommunication systems need to be equipped with antennas that are precisely tuned to more than one frequency in order to allow operation in several bands. Antenna precise tuning to the desired frequency is very important for system performance. In this paper the operating frequency of a PIFA antenna is adjusted using a varactor. This configuration has the advantage of continuous tuning, thus correcting any frequency deviation due to environmental or other changes. The PIFA antenna’s tuning ranges from 860 MHz to 1025 MHz. Also, the geometry of the antenna is studied through simulations and the effect of the varactor is tested experimentally.

关键词： PIFA Mobile Antenna varactor Frequency Tuning

Conversion of Common-Frequency Absorption/Transmission Based on Semiconductor Switch

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Conversion of Common-Frequency Absorption/Transmission Based...