CMOS LC VCO中交叉耦合MOS管的结构和特点

在近年来的文献报道中,CMOS LC VCO中交叉耦合MOS管的电路结构变化多端.在不同的设计中,MOS管的类型、数目和连接方式有很多不同的结构.从其基本结构出发总结这些结构,就不同结构MOS管电路对振荡器性能做了简要分析.着重介绍了近年来在理论认识,低电压、低相位噪声和宽频率覆盖设计方面所做的努力.     

超宽频带VHF频段CMOS LC VCO

实现了一个宽频带VHF频段CMOS VCO.其最大的改进在于将振荡器中交叉耦合MOS管分为并联可开关的若干段.这样使其特性可以在较大范围内补偿VCO调频过程中状态的变化.该VCO使用标准0.18μmCMOS工艺制作,核心版图面积约为550μm×700μm.测试结果表明:该VCO频率覆盖范围为31～111MHz;功耗为0.3～6.9mW;在100kHz频偏处相位噪声约-110dBc/Hz.     

An Ultra Wideband VHF CMOS LC VCO

实现了一个宽频带VHF频段CMOS VCO.其最大的改进在于将振荡器中交叉耦合MOS管分为并联可开关的若干段.这样使其特性可以在较大范围内补偿VCO调频过程中状态的变化.该VCO使用标准0.18μmCMOS工艺制作,核心版图面积约为550μm×700μm.测试结果表明:该VCO频率覆盖范围为31～111MHz;功耗为0.3～6.9mW;在100kHz频偏处相位噪声约-110dBc/Hz.     

基于等效小参量法的CMOS LC振荡器特性分析

建立了描述CMOS LC振荡器特性的二阶非线性微分方程.利用等效小参量法原理导出了原系统的等效线性方程组及其特性解析表达式,得到了交叉耦合MOS特性对振荡器性能的影响,包括起振条件、输出幅度与参数间的解析表达式、振荡器输出频率与LC谐振回路和交叉耦合CMOS管非线性特性影响的关系、振荡器输出的谐波特性.这些结论揭示了CMOS LC差分振荡器新的现象,对设计者了解振荡器的工作状态和优化设计有一定的参考意义.     

基于可调谐LC谐振回路的双频VCO

采用嵌有交叉耦合晶体管对的LC谐振回路结构,利用其固有的多种振荡模式,设计了一款用于多标准射频收发器的压控振荡器(VCO)。该电路通过变容管开关偏置的作用,操作于高频串联谐振和低频并联谐振两个模式,并且输出的所有频率都与谐波无关。通过累积型MOS变容管的调谐作用对LC谐振回路的节点阻抗进行改变,实现振荡器在两个模式下的切换。基于TSMC 0. 18μm 1P6M CMOS工艺实现文中所提出的VCO,测试表明:该VCO的振荡频率为2.92 GHz~3.23GHz和7.31 GHz~8.2 GHz,该两个频带的相位噪声分别为-128.22 dBc/Hz@1 MHz和-123.2 dBc/Hz@1 MHz。     

一种应用于低噪声PLL的RF-VCO设计

在PLL电路设计中,压控振荡器设计是电路的关键模块,按类型又主要分为LC震荡器和环形振荡器两种,其性能直接决定了相位噪声、频率稳定度及覆盖范围。文章介绍了一款1.8 GHz的基于交叉耦合对LC结构的低噪声CMOS压控振荡器的设计,并对调谐范围、相位噪声以及电路起振条件等做了分析讨论。该设计采用0.18μm 6层金属CMOS工艺制造,模块面积为0.3 mm2,电路经过Cadence SpectreRF仿真,VCO的输出范围为1 594~2 023 MHz,中心频率1.8 GHz输出时相位噪声为-118 dBc/Hz@600 kHz,1.9 GHz输出时相位噪声为-121 dBc/Hz@600 kHz。结果表明该VCO设计达到了较宽的频率覆盖范围和较低的相位噪声,可以满足低噪声PLL的设计要求。     

采用CMOS工艺中寄生V-NPN改进低频相位噪声的压控振荡器

本文将CMOS工艺中的寄生垂直NPN管(V-NPN)用于压控振荡器的交叉耦合单元来改善其低频偏处的相位噪声. 相对于MOS晶体管, V-NPN管拥有更低的闪烁噪声. 为了便于后续的电路设计, 本文对V-NPN管的直流和交流特性进行了测试. 提出的V-NPN VCO最终在SMIC 0.18-μm CMOS 射频/混合信号工艺上流片验证. 测试结果显示, 相比于一个类似的用MOS管充当交叉耦合管的VCO, 提出的V-NPN VCO在100Hz到10KHz频偏内的相位噪声改善了3.5~9.1dB. 在1.5V的电源电压下, 其消耗的电流仅为0.41mA.     

利用Van der Pol方程分析MOS LC差分振荡器

回顾了对MOS LC差分振荡器的认识现状。通过简单的推导和Van der Pol方程现有结论,得到了交叉耦合MOS特性对振荡器性能的影响。这些结论包括:1)起振条件;2)输出幅度与参数间的解析表达式;3)振荡器输出频率与LC谐振回路和交叉耦合MOS管非线性特性影响的关系;4)过渡过程的时间常数;5)振荡器输出的谐波特性。这些结论揭示了MOS LC差分振荡器新的现象,对设计者了解振荡器的工作状态和优化设计有一定的参考意义。     

基于0.18 μm RF CMOS工艺的低相噪宽带LC VCO设计

介绍了一种低功耗、低相噪和超宽频率覆盖范围的全差分电感电容结构的压控振荡器(VCO)设计.采用开关控制的二进制MIM电容阵列对频率进行粗调,再结合MOS可变电容进行微调,实现了极大的频率覆盖范围.流片采用TSMC的0.18μm、5层金属RF CMOS工艺,所用无源器件全部片内集成.在1.8 V电源供电情况下,该VCO仅仅消耗3 mA的电流.测试结果表明,该VCO能够覆盖1.65～2.45 GHz的频率范围,并且增益控制在100 MHz/V以下.在1.65 GHz频率下20 kHz频偏处的相位噪声仅-87.88 dBc/Hz.     

一个2.4 GHz CMOS LC压控振荡器的设计

采用单层多晶6层金属(1P6M)的0.18μm标准CMOS工艺,设计了一个2.4 GHz电感电容压控振荡器(LC tank VCO)。该压控振荡器的电路结构选用互补交叉耦合型。测试结果表明,在VCO的输入参考频率为1 MHz,工作电压1.8 V时,工作电流为5.5 mA,频率调谐范围2.1~2.8 GHz。     

A wide-range 22-GHz LC-based CMOS voltage-controlled oscillator

This work presents a novel voltage-controlled oscillator (VCO) design and simulations that combine a varactor bank with a transformer in the LC tank to achieve a high-frequency range. While the varactor bank is responsible for changing the capacitance in the LC tank, the transformer acts as a means to change the value of the inductance, hence allowing tune-ability in the two main components of the VCO. A control mechanism utilises a mixed-mode circuit consisting of comparators and a state machine. It allows efficient tuning of the VCO by controlling the capacitance and transformer in the LC tank. The VCO has a 10.75–22.43 GHz frequency range and the VCO gain, K_VCO, is kept at a low value ranging from 98.6 to 175.7 MHz/V. The simulated phase noise is ?111 dBc/Hz at 1 MHz offset from the 10.75 GHz oscillation frequency. The circuit is designed and simulated in 28 nm CMOS technology and uses a 1 V supply drawing a typical power of 14.74 mW.     

Large-signal analysis of MOS varactors in CMOS -G/sub m/ LC VCOs

MOS varactors are used extensively as tunable elements in the tank circuits of RF voltage-controlled oscillators (VCOs) based on submicrometer CMOS technologies. MOS varactor topologies include conventional D = S = B connected, inversion-mode (I-MOS), and accumulation-mode (A-MOS) structures. When incorporated into the VCO tank circuit, the large-signal swing of the VCO output oscillation modulates the varactor capacitance in time, resulting in a VCO tuning curve that deviates from the dc tuning curve of the particular varactor structure. This paper presents a detailed analysis of this large-signal effect. Simulated results are compared to measurements for an example 2.5-GHz complementary -G/sub m/ LC VCO using I-MOS varactors implemented in 0.35-/spl mu/m CMOS technology.     

Low-power low-phase-noise differentially tuned quadrature VCOdesign in standard CMOS

This paper describes the design and optimization of VCOs with quadrature outputs. Systematic design of fully integrated LC-VCOs with a high inductance tank leads to a cross-coupled double core LC-VCO as the optimal solution in terms of power consumption. Furthermore, a novel fully differential frequency tuning concept is introduced to ease high integration. The concepts are verified with a 0.25-μm standard CMOS fully integrated quadrature VCO for zero- or low-IF DCS1800, DECT, or GSM receivers. At 2.5-V power supply voltage and a total power dissipation of 20 mW, the quadrature VCO features a worst-case phase noise of -143 dBc/Hz at 3-MHz frequency offset over the tuning range. The oscillator is tuned from 1.71 to 1.99 GHz through a differential nMOS/pMOS varactor input     

Design and Analysis of a 90 nm mm-Wave Oscillator Using Inductive-Division LC Tank

A 60 GHz voltage-controlled oscillator with an inductive division LC tank has been designed in 90 nm CMOS. The analysis of the oscillator shows that the presence of higher harmonics, the capacitance nonlinearity and the very high $K _{rm VCO}$ are critical for the phase noise performance of oscillators. Therefore, a pseudo-differential amplifier is employed in this design because of its high linearity. Furthermore, the proposed inductive division reduces the phase noise by increasing the signal amplitude across the varactor, without affecting the operation mode of the cross-coupled pair transistors. It also helps to increase the tuning range by isolating the varactor from the parasitic capacitances of the transistors and interconnects. The mm-wave oscillator is fabricated in a 90 nm CMOS technology. Under 0.7 V supply, the oscillator achieves a tuning range from 53.2 GHz to 58.4 GHz, consuming 8.1 mW. At 58.4 GHz, the phase noise is $-hbox{91~dBc}/hbox{Hz}$ at 1 MHz offset. Under 0.43 V supply, the oscillator achieves a tuning range from 58.8 to 61.7 GHz. At 61.7 GHz, the phase noise is $-hbox{90~dBc}/hbox{Hz}$ @1$~$MHz offset with a power consumption of only 1.2 mW.      

A 0.5 V LC-VCO with improved varactor tuning technique for WSN

A 0.5 V LC-VCO implemented in 0.18 μm CMOS technology for wireless sensor network is described in this paper. An improved varactor tuning technique is proposed to decrease low frequency noise up-conversion and AM–FM phase noise of VCO, also it can increase Q of LC tank and reduce power consumption of VCO. For coarse tuning of VCO, it can increase the varactor control voltage variation range. For fine tuning of VCO, it can reduce the varactor nonlinearity. The measured tuning range is 4.58–5.26 GHz and power consumption is 2.2 mW. The measured phase noise is ?114 dBc/Hz at 1 MHz frequency offset from a 4.8 GHz carrier.     

Design formula for band-switching capacitor array in wide tuning range low-phase-noise LC-VCO

A low phase noise with wide tuning range complementary LC cross-coupled voltage control oscillator (LC-VCO) using 0.18 μm CMOS technology is presented. This paper proposes a design formula for the choice of the value of varactor (ΔC_var) and band switch capacitor (C_s) for the binary-weighted band-switching LC tank which is convenient to determine the proper tuning constant for wideband, low-phase-noise operations. This general formula considers the ratio of frequency overlap (ov) and all the parasitic effects from band-switching capacitor array and transistors. The designed VCO using a 4-bit band-switching capacitor array demonstrates the operating frequencies from 4.166 to 5.537 GHz with an equivalent tuning bandwidth of 28.26%. The measured tuning range of all sub-bands is well agreed with that of the post-layout simulation results. The measured phase noise is −123.1 dBc/Hz at 1 MHz offset in the 5.2 GHz band. The calculated figure-of-merit (FoM) of this VCO was as high as −187 dB. When considering the tuning bandwidth the designed VCO obtains a FoM-bandwidth product of 52.83, which is much better than previously published works.     

一款基于65nm CMOS工艺的高效率50GHz 压控振荡器及其电感耦合效应的研究

A 50 GHz cross-coupled voltage controlled oscillator(VCO) considering the coupling effect of inductors based on a 65 nm standard complementary metal oxide semiconductor(CMOS) technology is reported.A pair of inductors has been fabricated,measured and analyzed to characterize the coupling effects of adjacent inductors. The results are then implemented to accurately evaluate the VCO’s LC tank.By optimizing the tank voltage swing and the buffer’s operation region,the VCO achieves a maximum efficiency of 11.4%by generating an average output power of 2.5 dBm while only consuming 19.7 mW(including buffers).The VCO exhibits a phase noise of—87 dBc/Hz at 1 MHz offset,leading to a figure of merit(FoM) of-167.5 dB/Hz and a tuning range of 3.8%(from 48.98 to 50.88 GHz).     

应用于IMT-A和UWB系统的0.13μm CMOS宽带压控振荡器设计

基于TSMC 0.13μm CMOS工艺设计并实现了应用于IMT-Advanced和UWB系统的双频段宽带频率合成器中的电感电容压控振荡器(LC-VCO)。此压控振荡器的设计采用了开关电流源、开关交叉耦合对和噪声滤波等技术,以优化电路的相位噪声,功耗,振荡幅度,调谐范围等性能。为达到宽的调谐范围,核心电路采用了4比特可重构的开关电容调谐阵列。整个芯片包括焊盘面积为1.11′0.98 mm₂。测试结果表明,在1.2V电源电压下,两个频段压控振荡器所消耗的电流分别为3mA和4.5mA,压控振荡器的调谐范围为3.86~5.28GHz和3.14~3.88GHz。在振荡频率3.5GHz和4.2GHz上,1MHz频偏处,压控振荡器的相位噪声分别为-123dBc/Hz与-119dBc/Hz。     

基于90nmCMOS工艺的低功耗宽带压控振荡器设计

A low power VCO with a wide tuning range and low phase noise has been designed and realized in a standard 90 nm CMOS technology. A newly proposed current-reuse cross-connected pair is utilized as a negative conductance generator to compensate the energy loss of the resonator. The supply current is reduced by half compared to that of the conventional LC-VCO. An improved inversion-mode MOSFET(IMOS) varactor is introduced to extend the capacitance tuning range from 32.8% to 66%. A detailed analysis of the proposed varactor is provided. The VCO achieves a tuning range of 27–32.5 GHz, exhibiting a frequency tuning range(FTR) of 18.4%and a phase noise of –101.38 d Bc/Hz at 1 MHz offset from a 30 GHz carrier, and shows an excellent FOM of –185d Bc/Hz. With the voltage supply of 1.5 V, the core circuit of VCO draws only 2.1 m A DC current.     

Fully Differential 5‐GHz LC‐Tank VCOs with Improved Phase Noise and Wide Tuning Range

In this paper, we propose two LC voltage‐controlled oscillators (VCOs) that improve both phase noise and tuning range. With both 1/f induced low‐frequency noise and low‐frequency thermal noise around DC or around harmonics suppressed significantly by the employment of a current‐current negative feedback (CCNF) loop, the phase noise in the CCNF LC VCO has been improved by about 10 dB at 6 MHz offset compared to the conventional LC VCO. The phase noise of the CCNF VCO was measured as ?112 dBc/Hz at 6 MHz offset from 5.5 GHz carrier frequency. Also, we present a bandwidth‐enhanced LC VCO whose tuning range has been increased about 250 % by connecting the varactor to the bases of the cross‐coupled pair. The phase noise of the bandwidth‐enhanced LC‐tank VCO has been improved by about 6 dB at 6 MHz offset compared to the conventional LC VCO. The phase noise reduction has been achieved because the DC‐decoupling capacitor Cc prevents the output common‐mode level from modulating the varactor bias point, and the signal power increases in the LC‐tank resonator. The bandwidth‐enhanced LC VCO represents a 12 % bandwidth and phase noise of ?108 dBc/Hz at 6 MHz offset.