小学教育MEMS技术噪声与器件性能PPT教案

1、小学教育小学教育MEMS技术噪声与器件性能技术噪声与器件性能第1页/共49页简单的其他域的元件及其简要设计要点设计实例第2页/共49页第3页/共49页 2Let ( )0,0Di tI tIi twhilei22201Then ilimTDDTIIIIdtT第4页/共49页第5页/共49页0ijHjj 2*0iiSHjHjSHjS 0iSHjS第6页/共49页 21111nnSfSfBf第7页/共49页21ni211z1Hnniif第8页/共49页 11onniHj 22211onniHj222123,nnnivv222221234onTOTononononvvvvv22221234onTOT

2、ononononvvvvv第9页/共49页第10页/共49页24nBfk Tb f1/damping coefficientbMQ22221141/Bnk Tb fxfffQf第11页/共49页24nBvk TR f2/4nBvfk TR 22/4/ 4nrmsnvfnVHzvvmV第12页/共49页24/Bnk TifR 244Bnk TiBWAR第13页/共49页第14页/共49页2anKIiff第15页/共49页When biased in saturation, (VDSVDS,sat), the noise can be represented by an input noise v

3、oltage and an input noise current Origin of 1/f noise in MOSFETs: surface states22 143fmBmoxKfvk TfgWLCf channel resistance in saturationinverse dependence on gate area large transistors have lower 1/f noise22222 143gsDmBmmCKIik Tffgfg (neglecting DC gate current and its shot noise第16页/共49页Equivalen

4、t MOSFET small-signal model with input-referred noise sourcesCrossover frequency between thermal and flicker noise can range from 1 kHz to 1 MHz第17页/共49页第18页/共49页Signal-to-noise ratio = SNRNote 1: Pnoise is calculated over a limited bandwidthNote 2: Vn,rms is taken as the minimum detectable signal,

5、in the absence of special coding or signal processingDynamic range = DR222,10log10log20log20logssssnn rmsnnPvvvSNRPvvv2,max,max,max2,10log10log20logsssnoisen rmsnPvvDRPvv第19页/共49页Sinusoid with amplitude normalized to 1Gaussian noise with rms level normalized to 1; note that peak-peak noise level is

6、occasionally as high as 6!第20页/共49页第21页/共49页第22页/共49页Where 4/ m/ HznBZfk TRG fk 222200222000 1/1/ 6and 4/, In the accelerometer limit (), the noise displacement becomes 4/ (7) 4nBBnG fffffQfk mffZfk TR kkZf 300202s/4/ (8)The signal response is /G (9)but is the magnitude of the input acceleration, a(

7、in meters per square second per roBsssTkQk TmQZffffYY 202ot hertz), so / (10)1 in the accelerometer limit. The signal-to-noise ratio (SNR) at any frequency is then /sssnsZfa G fG fZZa mQ0/4 (11)Bk T第23页/共49页第24页/共49页第25页/共49页根据下图，画出压阻加速度计的噪声模型，途中的Cp需要改成R和Cp的并联。计算方式可参考陀螺的计算过程。2ccdFmamx The gyro sense

8、 presents a large effective source impedanceCurrents are the imprtant variable; voltages are “opend” outMust compare i0 with the total current noise ieqTOT going into the amplifier circuit第26页/共49页B. The simple Pressure snesor In the simple pressure snesor, the moving mass is directly exposed to the

9、 incident acoustic pressure and the displacement of this mass is measured. Such a sensor is shown schematically in Fig. 3. For an arbitrary force F, the displacement response Z is / (12)ZFG fkIEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 40, NO. 5. MAY 1993Mechanical-Thermal Noise in Micromachined Aco

10、ustic and Vibration SensorsFor signal, the force F=psS, where S is the area of the transducer face and ps is the spectral density of the signal pressure; for noise, the force , so the signal-to-noise ratio is 4BFk TR2220/4/4 (13)snsBsBZZp Sk TRQ p Sk T m第27页/共49页第28页/共49页第29页/共49页IEEE SENSORS JOURNA

11、L, VOL. 5, NO. 3. JUNE 2005Mechanical-Thermal Noise in MEMS Gyroscopes2 12 2xxdrivexxsenseMxR xK xMyuMyR yK yMxu （ ）（ ）第30页/共49页Generate momentum by vibrating structuresAgain, conservation of momentum leads to mechanisms for measuring rotation rate and orentationExample: vibrating mass in a rotating

12、 frame第31页/共49页Principle of OperationDrive/Sense Reponse spectra:Tuning Fork Gyroscope2cav2ccccrFmaaxkk 第32页/共49页In-plane drive and sense modes pick up z-axis rotationsMode-matching for maxmum output sensitivityFrom Zaman, Ayazi, et al, MEMS06第33页/共49页第34页/共49页Generates drive displacement velocity x

13、d to which the Coriolis force is proportionalTo Sense Amplifer(for synchronization)第35页/共49页Rotation- Induced Coriolis Force:22 Acts in the sense mode direction2sin90cdddocddaxxax 第36页/共49页Gyro Sense Element Output CircuitGyro Sense Element Output CircuitEasiest to analyze if all noise source are su

14、mmed at common node2ccdFmamx 第37页/共49页2ccdFmamx Gyro Sense Element Output CircuitSignal Conditioning circuit (Transresistance Amplifier)Here, and are equivalent input-referred voltage and current noise source2eqv2eqi 第38页/共49页The gyro sense presents a large effective source impedanceCurrents are the

15、 important variable; voltages are “opened” outMust compare i0 with the total current noise ieqTOT going into the amplifier circuit2ccdFmamx 第39页/共49页First, find the rotation to i0 transfer function:2ssssdsdddssQQxjFxmjkk2dsddsxQxj第40页/共49页002 Ascale factor where 2desdedsddedsixQxjiAAQxjmin0eqTOTwhen

16、 MDS, i =i input-referred noise current entering the sense amplifier in A/ Hz minmin360180 /oeqTOTeqTOTiDSiAo hrHzAhr min1Angle Random Walk = ARW = /60 Easier to determine directional error as a function of elapsed timo hrHze第41页/共49页Now, find the ieqTOT entering the amplifier input:222222iaeqTOTseq

17、eqTOTsfiafviiiiiiiR24rxxfkTvfBrownion motion noise of the sense element determined entirely by the noise in rx 2rxf第42页/共49页Where 2222222222222, , 1144 441Thus: yxxxexxeessRxdxdxxsdxeqTOTiaiadxfflrLCcRiivjkTRjRfRikTjfRiivkTkTjfRRffR第43页/共49页第44页/共49页Example Design:第45页/共49页 120Get rotation rate to o

18、utput current scale factor:10225020520000.0000242.83 1015dsdedskAQ xjkCk 82222228/1015/ 50310151.25 1031510503 0.0000241.25 103dssddsdssdjQjkkkjkjjjkkjkkkQkkjk 0000022010020005 20001pphwCCCVxddx2222eqTOT2Then, get noise:i441 fffiaiadxffivkTkTjRRR第46页/共49页102282154.6 10110.6508.85 10sxsekmRkQk22020222eqTOT21.66 101.66 10i120.0000240.01f110.611npkMM22eqTOT26213i1.68 10/1.30 10/ffeqTOTeqTOTiAHziAHz13min1236001801.30 1018036009448/2.83 10oeqTOToishrHzAhrmin11And finaly: ARW=9448157 / Almost turned 6060 around in 1 hour!ohrARW第47页/共49页