Improvements in reverse breakdown characteristics of THz GaAs Schottky barrier varactor based on metal-brim structure

The excellent reverse breakdown characteristics of Schottky barrier varactor(SBV)are crucially required for the application of high power and high efficiency multipliers.The SBV with a novel Schottky structure named metal-brim is fabricated and systemically evaluated.Compared with normal structure,the reverse breakdown voltage of the new type SBV improves from-7.31 V to-8.75 V.The simulation of the Schottky metal-brim SBV is also proposed.Three factors,namely distribution of leakage current,the electric field,and the area of space charge region are mostly concerned to explain the physical mechanism.Schottky metal-brim structure is a promising approach to improve the reverse breakdown voltage and reduce leakage current by eliminating the accumulation of charge at Schottky electrode edge.

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

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.

A GaAs planar Schottky varactor diode for left-handed nonlinear transmission line applications

The left-handed nonlinear transmission line （LH-NLTL） based on monolithic microwave integrated circuit （MMIC） technology possesses significant advantages such as wide frequency band, high operating frequency, high conversion efficiency, and applications in millimeter and submillimeter wave frequency multiplier. The planar Schottky varactor diode （PSVD） is a major limitation to the performance of the LH-NLTL frequency multiplier as a nonlinear component. The design and the fabrication of the diode for such an application are presented. An accurate large-signal model of the diode is proposed. A 16 GHz-39,6 GHz LH NLTL frequency doubler using our large-signal model is reported for the first time. The measured maximum output powers of the 2nd harmonic are up to 8 dBm at 26.4 GHz, and above 0 dBm from 16 GHz to 39.6 GHz when the input power is 20 dBm. The application of the LH-NLTL frequency doubler furthermore validates the accuracy of the large-signal model of the PSVD.

Varactor-tunable frequency selective surface with an embedded bias network

A new technique for designing a varactor-tunable frequency selective surface （FSS） with an embedded bias network is proposed and experimentally verified. The proposed FSS is based on a square-ring slot FSS. The frequency tuning is achieved by inserting varactor diodes between the square mesh and each unattached square patch. The square mesh is divided into two parts for biasing the varactor diodes. Full-wave numerical simulations show that a wide tuning range can be achieved by changing the capacitances of these loaded varactors. Two homo-type samples using fixed lumped capacitors are fabricated and measured using a standard waveguide measurement setup. Excellent agreement between the measured and simulated results is demonstrated.

Design of a varactor-tunable metamaterial absorber

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.

NOVEL ELECTRONIC TUNER USING VARACTORS FOR TUNABLE RF FRONT-ENDS

This paper presents a novel electronic tuner with high power handling capability utilizing varactors based on the asymmetric bilateral coupled microstrip transmission line. Through varying the bias voltage of the varactor at the Ultra High Frequency (UHF) band, the performance of the tuner is demonstrated according to simulated and measured results from several cases with the return loss (S11 ) below -20 dB and the insertion loss (S21 ) within ±0.5 dB. Compared with tuners using p and t network, electronic tuner of this paper shows superior frequency agility as well as wide impendence coverage. Advanced biasing structure has been developed to improve power handling for high power level applications. It is expected that the novel tuner would be part of intelligent Radio Frequency (RF) front-ends system and cognitive wireless system in the future.

Optimization of terahertz monolithic integrated frequency multiplier based on trap-assisted physics model of THz Schottky barrier varactor

The optimization of high power terahertz monolithic integrated circuit (TMIC) is systemically studied based on the physical model of the Schottky barrier varactor (SBV) with interface defects and tunneling effect. An ultra-thin dielectric layer is added to describe the extra tunneling effect and the damping of thermionic emission current induced by the interface defects. Power consumption of the dielectric layer results in the decrease of capacitance modulation ration (Cmax/Cmin), and thus leads to poor nonlinear C–V characteristics. The proposed Schottky metal-brim (SMB) terminal structure could improve the capacitance modulation ration by reducing the influence of the interface charge and eliminating the fringing capacitance effect. Finally, a 215 GHz tripler TMIC is fabricated based on the SMB terminal structure. The output power is above 5 mW at 210–218 GHz and the maximum could exceed 10 mW at 216 GHz, which could be widely used in terahertz imaging, radiometers, and so on. This paper also provides theoretical support for the SMB structure to optimize the TMIC performance.

Planar Schottky varactor diode and corresponding large signal model for millimeterwave applications

A GaAs-based planar Schottky varactor diode （PSVD） is successfully developed to meet the demand of millimeter-wave harmonic generation. Based on the measured S-parameter, I-V and C-V characteristics, an accurate and reliable extraction method of the millimeter-wave large signal equivalent circuit model of the PSVD is proposed and used to extract the model parameters of two PSVDs with Schottky contact areas of 160 μm2 and 49 μm2, respectively. The simulated S-parameter, I-V and C-V performances of the proposed physics-based model are in good agreement with the measured one over the frequency range from 0.1 to 40 GHz for wide operation bias range from -10 to 0.6 V for these two PSVDs. The proposed equivalent large signal circuit model of this PSVD has been proven to be reliable and can potentially be used to design microwave circuits.

基于阶跃阻抗谐振器的四阶频率可调滤波器设计

提出一种基于阶跃阻抗谐振器的紧凑型四阶四零点频率可调滤波器设计。滤波器使用变容二极管加载的阶跃阻抗谐振器(VL-SIR),有效拓宽了滤波器的调谐范围。在VL-SIR之间引入交叉耦合,从而在滤波器通带近端产生一对传输零点,显著提高了滤波器的选择性。同时,引入源和负载端的交叉耦合,在通带远端生成一对传输零点,以提高带外抑制。此外,采用基于VL-SIR的频变耦合结构来实现恒定绝对带宽。仿真结果与实测结果吻合良好。测量结果显示,可调滤波器频率调谐范围为0.78~1.15 GHz,3 dB绝对带宽约为55±3 MHz,滤波器的回波损耗大于10 dB,插入损耗约为2.8~3.3 dB。

基于变压器磁调谐的双模W波段VCO

提出了一种基于变压器的用于无变容管W波段压控振荡器(VCO)的磁调谐技术。通过控制变压器磁调谐线圈所连接MOS管的开关状态,引入了四个重叠的频率子带。所提出的可切换的六线圈变压器采用40 nm CMOS工艺的顶层厚金属设计,实现了较高的输出频率稳定性和谐振腔品质因数。所采用的技术在对相位噪声的不利影响最小的情况下扩展了调谐范围,实现了无变容管W波段VCO的宽调谐范围和低功耗。所设计的双模W波段VCO输出频率为84.2~107.5 GHz,频率调谐范围大于24%,在1 V电源电压下功耗仅6.1 mW,在10 MHz偏移处的相位噪声为-107.203~-97.875 dBc/Hz。

基于变容二极管的直流电压非接触测量方法研究

为解决接触式测量技术对原电路的侵入性和安全性问题,根据变容二极管PN结反向偏压下的电容特性,提出了一种基于变容二极管的非接触式直流电压测量方法。该方法通过电场耦合效应感应待测直流电压,通过正弦信号激励和相关测量技术实现变容二极管的电容测量。利用LTspice软件对设计的测量电路进行仿真,并搭建实验测量系统。仿真和实验结果表明:该测量系统可以实现非接触式的直流电压测量,在变容二极管的工作电压范围内,相对测量误差≤2.50%。文中提出的测量方法,摒弃了传统直流电压非接触测量方式中的机械运动部件,具有较好的应用前景。

An Accurate 1.08GHz CMOS LC Voltage-Controlled Oscillator

An accurate 1.08GHz CMOS LC voltage-controlled oscillator is implemented in a 0.35μm standard 2P4M CMOS process.A new convenient method of calculating oscillator period is presented.With this period calculation technique,the frequency tuning curves agree well with the experiment.At a 3.3V supply,the LC-VCO measures a phase noise of -82.2dBc/Hz at a 10kHz frequency offset while dissipating 3.1mA current.The chip size is 0.86mm×0.82mm.

Design of 2.5GHz Low Phase Noise CMOS LC-VCO

A 2 5GHz fully integrated LC VCO is fabricated in a standard single poly 4 metal 0 35μm digital CMOS process,using a complementary cross coupled topology for lowering power dissipation and reducing the effect of 1/ f noise.An on chip LC filtering technique is used to lower the high frequency noise.Accumulation varactors are used to widen frequency tuning.The measured tuning range is 23 percent.A single hexadecagon symmetric on chip spiral is used with grounded shield pattern to reduce the chip area and maximize the quality factor.A phase noise of -118dBc/Hz at 1MHz offset is measured.The power dissipation is 4mA at V DD =3 3V.

A wideband low-phase-noise LC VCO for DRM/DAB frequency synthesizer

The wideband CMOS voltage-controlled oscillator（VCO）with low phase noise and low power consumption is presented for a DRM/DAB（digital radio mondiale and digital audio broadcasting）frequency synthesizer.In order to obtain a wide band and a large tuning range,a parallel switched capacitor bank is added in the LC tank.The proposed VCO is implemented in SMIC 0.18-μm RF CMOS technology and the chip area is 750 μm×560 μm,including the test buffer circuit and the pads.Measured results show that the tuning range is 44.6%;i.e.,the frequency turning range is from 2.27 to 3.57 GHz.The measured phase noise is-122.22 dBc/Hz at a 1 MHz offset from the carrier.The maximum power consumption of the core part is 6.16 mW at a 1.8 V power supply.

Design of a 4.224GHz Quadrature LC-VCO

A 4. 224GHz quadrature voltage-controlled oscillator （QVCO） applied in MB-OFDM UWB synthesizers is implemented in 0.18μm RF-CMOS technology. An improved structure of the QVCO is presented for better phase noise. A novel configuration of a MOS varactor is designed for good linearity of K as well as a new digital capacitor controlled array topology with lower parasitic capacitance and lower Ron. Measurement results show a phase noise of - 90.4dBc/Hz at 100kHz offset and - 116.7dBc/Hz at 1MHz offset from a carrier close to 4. 224GHz. The power dissipation is 10. 55mW from a 1.8V supply.

225 GHz三倍频器实用设计方法

结合国内现有的加工工艺水平,提出自偏置条件下的反向并联二极管对电路结构.不但解决了三倍频器偏置电路加工的难题,而且可以有效实现奇次倍频.同时,利用HFSS和ADS软件,以场路结合的方式准确模拟三倍频器的电特性,考虑到寄生参数引入的影响.设计完成以后,器件加工以及电装过程均在国内完成.测试结果表明在221 GHz处,有最大输出功率3.1 m W,在219~227 GHz频率范围内输出功率均大于2 m W.以上研究为今后设计高效率亚毫米波倍频器提供重要的参考价值.

一种适用于2.4GHz ISM射频波段的全集成C MOS压控振荡器

提出了一种频率可调范围约 2 30MHz的全集成LC压控振荡器 (VCO) .该压控振荡器是用 6层金属、0 18μm的标准CMOS工艺制造完成 .采用MOS晶体管和电容组合来实现等效变容管 ,为降低芯片面积仅使用一个片上螺旋电感 ,并实施了低电压、低功耗的措施 .测试结果表明 ,该压控振荡器在电源电压为 1 8V的情况下功耗约为10mW ,在振荡器中心频率为 2 46GHz时的单边带相位噪声为 - 10 5 89dBc/Hz @6 0 0kHz .该压控振荡器可以应用于锁相环电路或频率综合器中 .

1V 2.5GHz压控振荡器设计

设计了 1V ,2 .5 GHz的全集成压控振荡器 .通过优化集成电感的设计 ,同时采用 NMOS管和开关电容阵列作为可变电容 ,使该设计具有较低的相位噪声和较宽的调谐范围 .采用 0 .18μm CMOS工艺进行仿真 ,结果显示 ,在1V电源电压下 ,在偏离中心频率 6 0 0 k Hz处的相位噪声为 - 119d Bc/ Hz,调谐范围为 2 8% ,功耗为 3.6 m W.

宽带低相噪分立VCO的设计

压控振荡器(VCO)在通信、雷达、测试仪器等领域中的应用非常广泛,但宽带调谐、低相噪一直是VCO设计的瓶颈。通过对负阻原理的分析,根据三极管的等效电路参数采用准线性法对最佳谐振元件进行了估算,从而提高了对VCO设计的准确性和时效性。由变容二极管对和PC电感组成的并联谐振网络,实现了宽带调谐、低相噪,并对三次谐波分量有所抑制。通过最后的实验测试,调谐电压在5~18 V时,频率覆盖范围为468 MHz^1.13 GHz,相位噪声?105 dBc/Hz@10 kHz at 969.27 MHz,输出功率?1 dBm,调谐灵敏度为34 MHz/V。

基于肖特基变容二极管的0.17THz二倍频器研制

研制了一种基于肖特基变容二极管的0.17 THz二倍频器,该器件为0.34 THz无线通信系统收发前端提供了低相噪、低杂散的本振信号。倍频器结构基于波导腔体石英基片微带电路实现,其核心器件是多结正向并联的肖特基变容二极管。文中采用结参数模型和三维电磁模型相结合的方式对二极管进行建模,通过两种电路匹配方式实现了0.17 THz二倍频器的最优化设计,最终完成器件的加工及测试。测试结果表明,在输入80~86 GHz,20 d Bm的驱动信号下,倍频器的最大输出功率达12.21 m W,倍频效率11%,输出频点为163 GHz;当前端输入功率达到饱和状态时,该频点输出功率可达21.41 m W。