基于LMS 算法的多麦克风降噪
武汉理工大学 信息处理课设 基于LMS 算法的多麦克风降噪 给定主麦克风录制的受噪声污染的语音信号和参考麦克风录制的噪声，实现语音增强的目标，得到清晰的语音信号。2007控制科学与工程全国博士生学术论坛2007年8月其中日为语音信号与麦克风阵列所在平面的夹角,d为麦克风间距,c为声音传播速度,f为信号采样率。固定波束形成器通过延时求和单元产生参考语音信号y(n),y(n)与y(m)分别代表期望语音信号与噪声信号。y,(n)4x(m)=y(m)+y/(m(3)信号通过阻塞矩阵产生噪声参考信号用来估计波束形成输出信号中的噪声成分。选取B使其中任意行向量之和为零,即任意行向量线性无关。为了进一步降低噪声参考信号中的语音泄漏,参考文献“提出了用自适应阻塞矩阵替代固定阻塞矩阵的方法。ynly2nMM-[nJ]=BLun], u2n],umn自适应噪声抵消器ANC通过对输入噪声参考信号进行自适应滤波处理抵消了参考信号y,(m)中的噪声成分,得到增强的语音信号。em]=y[m-∑nnl3LMS自适应算法及改进31LMS自适应算法GSC架构中的自适应噪声抵消器ANC需要用增强的语音信号作为反馈对滤波器权值进行自适应更新。很多自适应算法基于LMS及其改进形式, Clark提出的块LMS算法使得滤波器的自适应逐块更新而非传统LMS滤波器逐点更新4, HOSHUYAMA、 Kellermann分别提出的基于范数约束自适应算法的权值更新,以及频域无约束实现。这些算法基本结构如图2所示y(n-1)(n-L+1)wo(ne(ny/(n)图2自适应横向滤波器结构图图2为图1中的M-1路L阶多通道自适应噪声对消器中某一路的展开形式,其抽头输入向量为[ym]yn-]yn-L+1],对应的抽头权向量为wmwn]w-]。LMS算法的梯度向量通过G2007控制科学与工程全国博士生学术论坛2007年8月计算抽头输入相关矩阵R和抽头输入与期望响应间互相关向量p得到VJ(n)=-2p+2Rv(m),将R和p的瞬态估计R(n)=y(m)y"(n),p(n)=y(n)y/(m)代入,得出梯度向量的瞬态估计:VJ(n)=-2y(n)y, (n+2y(n)y"(n)w(n)进而推出LMS算法权值更新公式为w(n+1)=w(n)+uy(n)Ly(n)-y"(n)w(n)32基于稳态噪声的自适应算法改进考查图2中具有L个抽头权值的LMS算法,抽头权值与抽头输入一一对应。在传统的逐点更新LMS算法中,每计算一个输出需要L次乘法,而更新一次抽头权值也需要L次乘法,故每次迭代需要2L次乘法。对于L个输出样值,所需要的乘法次数为2次。针对传统LMS算法复杂度高的缺点,Ca利用离散傅立叶变换在频域完成滤波器系数的自适应提出了快速块LMS箅法, Ann Spriet在此基础上通过改进LMS算法中的步长矩阵进一步降低了算法复杂度以上LMS算法改进均在图2的横向滤波器架构下进行,即抽头权值与抽头输入一一对应。考虑到稳态噪声的特点,本文提出了“一对多”的滤波器抽头权值更新算法,即L个输入样值共享一个滤波器权值。如此M路多麦克风语音增强系统中的ANC滤波器权值便由(M-1)×L维矩阵W[n=[w[η],n2[rl…wM-[r],其中H[n]=[won],w1[nw-r]退化为(M-1)×1维向量n]=[wryw2n],M-m]j。改进算法权值更新公式为w(n+D)=w(n)+uBu(nu"(n)[A-Bw(n)其中B为阻塞矩阵,A为固定波束形成器,为步长,U(n)为LxM维输入信号。与传统的“一对一”LMS滤波器相比,“一对多”结构在降低算法复杂度的同时,牺牲了前者具有的时间域严格对齐的特性。为降低这一缺点对系统降噪性能的影响,应在频域进行噪声对消,改进算法的多麦克风语音增强系统结构如图3所示。e(n)(n)B Yn图3改进的噪声消除算法结构图3中用虚线框表示可选滤波器权值w。由于实际应用中语音泄漏的存在,在参考语音信号中加入v能有效补偿由语音泄漏引起的语音崎变⑩。实际应用中由于阻塞矩阵输出不可避免的存在语音泄4642007控制科学与工程全国博士生学术论坛2007年8月漏,为了避免期望信号的消除,箅法中加入语音活动检测单元89,当前帧为噪声时更新滤波器系数,当前帧为语音信号时,滤波器系数不变33算法复杂度比较表1列出了本文算法与其他几种噪声消除算法之间算法复杂度的比较。我们采用实数乘法运算次数作为衡量算法复杂度的标准,每个N点傅立叶变换或其反变换需要Mlog2N次实数乘法运算。传统逐点LMS算法在时间域逐点更新滤波器权值。快速块LMS算法与多通道 Wiener算法通过FFT快速循环卷积特性实现LMS中的线性卷积运算,从而降低算法复杂度。本文算法在此基础上通过改进滤波器抽头权值更新算法进一步降低运算复杂度。由表1可见,当麦克风数目M4,L=32时,本文算法与多通道 Wiener滤波算法相比,R(3M+2)FT+8ML+2M63M+2)+4M2+6M_172(M+2)FFT+2ML6(M+2)+M40°文算法运算量降低了4倍左右。表1算法复杂度比较算法名称算法复杂度传统逐点LMS算法2ML快速块LMS算法(41(3M+2)FFT+16ML多通道 Wiener滤波算法53M+2)FFT+8M2+12M本文提出的算法(M+2)FF+2M…图4a)麦克风采集到的原始信号b)采用快速块LMS算法处理后的信号[4]c)采用多通道 Wiener滤波算法[10处理后的信号d采用本文算法处理后的信号4实验结果与分析实验采用线性排列的4个间距为4厘米的麦克风组成的语音采集系统,采样率为44KHZ,说话人位于阵列的正前方,噪声为稳态噪声,其与麦克风阵列法线所夹角度为50度。图4比较了麦克风采集到的信号、采用本文算法处理后的语音信号以及采用其他主流语音增强算法处理后的语音信号的时域波形。由4652007控制科学与工程全国博士生学术论坛2007年8月图4可见采用本文算法处理的语音信号背景噪声有明显降低。为进一步分析各种语音增强算法消噪能力,分别按照公式9计算各算法输出信号的信噪比,其中k代表帧序列号,N代表噪声,Y代表输出语音信号,L为帧长。∑(Y(k,2)2-|N(k,)SNRou(E)=10 log,o∑1MV6)图5釆用各箅法输出信号信噪比与输入信号信噪比之差来衡量噪声降低程度。由图5看出,在本文算法基础上在参考通道中加入可选滤波器权值能够进一步消除背景噪声,提高输出信噪比。苯文鲜法(使用权值w)木文好法未使用权值y块LMS算法Frame Number图5信噪比增强对比5结论本文在稳态噪声的前提下,提出了一种基于广义旁瓣消除器架构具有低算法复杂度的噪声消除算法,该算法通过改进LMS滤波器权值更新算法来达到降低算法复杂度的目的。实验结果证明,在稳态噪声环境下,该方法降噪性能优于传统LMS算法,同时有效降低了传统算法的算法复杂度。在现实生活中一些存在稳态噪声的场合,如发动机舱、厂房等该算法具有很强的实用价值。参考文献[U]LJ. Griffiths and C. W. Jim []. "An altemative approach to linearly constrained adaptive beamforming, IEEE Trans. AntennasProcess., voL. AP-30, no. I, pp 27-34, Jan. 1982.[2]0. Hoshuyama, A Sugiyama, and A Hirano [J]. "A robust adaptive beamformer for microphone arrays with a blocking matrixusing constrained adaptive filters, "IEEE Trans. Signal Process. vol 47, pp. 2677-2683, Oct. 1999[3]W. Herbordt and W Kellermann [J]. " Frequency-domain integration of acoustic echo cancellation and a generalized sidelobecanceller with improved robustness, "Eur. Trans. Telecommun., voL. 13, no 2, pp 123-132, Mar. -Apr. 2002.[4]Clark. G.A., S K Mitra, and S.R. Parker [J]. Block implementation of adaptive digital filters, "IEEE Trans. Circuits Syst,voL. CAS-28,PP584-592.1981.[5]Ann Spriet, Jan Wouters, Simon Doclo, Marc Moonen, "Frequency-Domain Criterion for the Speech Distortion WeightedMultichannel Wiener Filter for Robust Noise Reduction", Ap: //ftp. esat kuleuven. ac, be/pub/SISTA/doclo/reports/04-240 pdf[6JH. Buchner, J. Benesty, W. Kellermann J]. Generalized multichannel frequencydomain adaptive filtering: efficient realizationand application to hands free speech communication", Signal Processing 85(3), PP 549-570. 2005[7]W.Herbordt and W. Kellermann [A]. " Efficient Frequency-domain realization of robust generalized sidelobe cancellers", IEEE4662007控制科学与工程全国博士生学术论坛2007年8月Fourth workshop, multimedia signal Processing, PP. 377-382 2001[8]S. Van Gerven, F. Xie [J. "A Comparative Study of Speech Detection Methods", Proc. EUROSPEECH, VoL 3, Rhodos, Greecepp.1095-1098.1997[9]J Sohn, N.S.Kim, W Sung [] A Statistical Model-Based Voice Activity Detection", IEEE Signal Processing Lett. 6(1)1-31999[10]A Spriet, M. Moonen, J Wouters[]. Robustness Analysis of Multi-channel wiener Filtering and generalized sidelobeCancellation for Multi-microphone Noise Reduction in Hearing Aid Applications", IEEE Trans. Speech and Audio Processing, 13(4)PP.487-503.2005[IlJFerrara, E R r [] Fast implementation of LMS adaptive filters", IEEE Trans. Acoust. Speech Signal Process,voL.ASSP-28pp474-475.1980[12]S. Doclo and M. Moonen[J]. " Multi-microphone noise reduction using recursive GSVD-based optimal filtering with ANCpostprocessing stage, "IEEE Trans. Speech Audio Process., vol. 13, no. 1,Pp 53-69, Jan. 2005[13]Philipos C Loizou [J]. "Speech Enhancement Based on Perceptually Motivated Bayesian Estimators of the MagnitudeSpectrum" IEEE TRANSACTIONS ON SPEECH AND AUDIO PROCESSING, VOL 13, NO 5, Pp.857-869, 2005种新的基于稳态噪声的噪声消除算法旧WANFANG DATA文献链接作者:董鹏宇,朱子元,林涛作者单位:同济大学超大规模集成电路研究所,上海20009本文链接http://d.g.wanfangdata.comcn/confereNce6584700.aspx
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使用CC2591作为CC2530的功放
使用CC2591作为CC2530的功放, CC2591 PAThe absolute maximum ratings and operating conditions listed in the CC2530 datasheet [1]and the CC2591 datasheet [4] must be followed at all times. Stress exceeding one or more ofthese limiting values may cause permanent damage to any of the devicesNote that these characteristics are only valid when using the recommended register settingspresented in Section 4.6 and in Chapter 8, and the CC2530 - EM reference designOperating Frequency240524835MHzOperating Supply Voltage2036VOperating Temperature-40CTC=25C, VDD=3.0V, f=2440 MHz if nothing else is stated. All parameters are measuredon the CC2530-Cc2591EM reference design [11] with a 50 Q2 loadReceive CurrentWait for sync, -90 dBm input levelWait for sync, -50 dBm input level24mATXPOWER OXE5166mATXPOWER OXD5149mATXPOWER OXC5138mATXPOWER OXB5127mATransmit currentTXPOWER OXA5115ATXPOWER = 0X95100mATXPOWER = 0X8594ATXPOWE=0×75mATXPOWE=0×6579APower Down Current PM2UAISTRUMENTSPage 3 of 19SWRA308ATC=25C, Vdd=3.0V, f= 2440 MHz if nothing else is stated. All parameters are measuredon the CC2530-CC2591 EM reference design with a 50 Q2 loadReceive Sensitivity HGM 1 %PER, IEEE 802. 15.4[6] requires -85 dBm-988dBmReceive Sensitivity LGM1 PER, IEEE 802. 15.4 [6] requires -85 dBm-90.4dBmSaturationlEEE 802.15. 4 [6] requires-20 dBm10dBmWanted signal 3 db above the sensitivity levelIEEE 802.15.4 modulated interferer at ieee 802.15.4 channelsInterferer Rejection+5 MHz from wanted signal, IEEE 802. 15. 4 [6] requires 0 dBdB+10 MHz from wanted signal, IEEE 802. 15. 4 [6] requires 30 dB49dB+20 MHz from wanted signal wanted signal at- 82d BmdBdue to in the external lna and the offset in cc2530 the rssi readouts from cc2530CC2591 is different from rssi offset values for a standalone cc2530 design the offsetvalues are shown in table 4.4High Gain Mode79LoW Gain mode67Real rssi Register value-Rssl offsetISTRUMENTSPage 4 of 19SWRA308ATc=25C, Vdd=3.0V, f=2440 MHz if nothing else is stated All parameters are measuredon the CC2530-CC2591 EM reference design with a 50 Q2 load Radiated measurements aredone with the kit antennaRadiated Emissionwith TXPOWer Oxe5Conducted 2. RF (FCC restricted band)-462|dBmConducted 3. RF(FCC restricted band46.5 dBmComplies withFCC 15.247. SeeChapter 7 for moredetails about regulatoryRadiated 2.RF(FCC restricted band)42.2dBmrequirements andcomplianceIEEE 802.15.4[6]requires max.35%%Measured as defined by IEEE 802.15. 4 6TXPOWER OxE5. f= EEE 802.15. 4 channels13TXPOWER= OXD5. f= EEE 802.15.4 channelsTXPOWER= OXC5 f= EEE 802.15.4 channelsMax error∨ ectorTXPOWER OxB5 f= IEEE 802.15. 4 channelsMagnitude(EVM)TXPOWER OxA5. f= IEEE 802.15.4 channelsTXPOWER 0X95. f= IEEE 802. 15.4 channels643333%%%%%%%TXPOWER= 0x85. f= iEEE 802. 15.4 channelsTXPOWER =0x75 f= IEEE 802. 15.4 channels%TXPOWER= 065. f= iEEE 802. 15.4 channelsThe RF output power of the CC2530- CC2591 EM is controlled by the 7-bit value in theCC2530 TXPOWER register. Table 4.6 shows the typical output power and currentconsumption for the recommended power settings The results are given for Tc= 25 C, Vdd3.0V and f= 2440 MHz, and are measured on the cC2530-CC2591 EM reference designwith a 50 Q2 load. For recommendations for the remaining CC2530 registers, see Chapter 8 oruse the settings given by SmartRF StudioOXE520166OxD519149OxC18138OxB517127OxA5161150x95141000x8513940X75860x651079Note that the recommended power settings given in Table 4.6 are a subset of all the possibleTXPOWER register settings. However, using other settings than those recommended mightINSTRUMENTSPage 5 of 19SWRA308Aresult in suboptimal performance in areas like current consumption, EVM, and spuriousemissionTc=25C, Vdd=3.0V, f=2440 MHz if nothing else is stated All parameters are measuredon the CC2530-CC2591EM reference design with a 50 32 load2221-2V201918171611121314151617181920212223242526251510OxE5OxC5OxA50X850x65540-30-20-1001020304050607080ISTRUMENTSPage 6 of 19SWRA308A98Avg 3.6VAva 3vAvg 2V110111213141516171819202122232425261023.6V-1062V-110-40-30-20-100102030405060708070604020-Wanted signal at:-82 dBm10ISTRUMENTSPage 7 of 19SWRA308ACC2530-CC2591EM High Gain ModeC C2530-CC2591EM Low Gain Mode- CC2530EM40000-100110100908070-60-50-40-30-20-100The IEEE standard 802.15. 4 [8] requires the transmitted spectral power to be less than thelimits specified in table 4.7If-fc>3.5 MHz-20 dB-30 dBmThe results below are given for Tc=25 C, Vdd=3.0V and f= 2440 MHz, and are measuredon the CC2530-CC259 1EM reference design with a 50 Q loadIEEE absoluteChannel 182432.52435243752442524452447.5ISTRUMENTSPage 8 of 19SWRA308AOnly a few external components are required for the CC2530-CC2591 reference design. Atypical application circuit is shown below in Figure 5.1. Note that the application circuit figuredoes not show how the board layout should be done. The board layout will greatly influencethe RF performance of the CC2530-CC2591EM. TI provides a compact CC2530CC2591 EM reference design that it is highly recommended to follow. The layout, stack-upand schematic for the CC2591 need to be copied exactly to obtain good performance. Notethat the reference design also includes bill of materials with manufacturers and part numbersL102 L10=TI INF inductorVDD13cc2530LA 1RF PANTCC2591 RF NFNPA EN(P1 1)i工工I NA FNP:1HGM ENPO 7)T:1Proper power supply decoupling must be used for optimum performance. In Figure 5.1, onlythe decoupling components for the CC2591 are shown. This is because, in addition todecoupling, the parallel capacitors C11, C101, and C131 together with, L101, L102, TL11TL101 and TL131 also work as RF loads. These therefore ensure the optimal performancefrom the CC2591. C161 decouples the AvDD blAs power.The placement and size of the decoupling components, the power supply filtering and thePCB transmission lines are very important to achieve the best performance Details about theimportance of copying the CC2530-CC2591EM reference design exactly and potentialconsequences of changes are explained in chapter 6The RF input/output of CC2530 is high impedance and differential. The CC2591 includes abalun and a matching network in addition to the PA, LNa and RF switches which makes theinterface to the CC2530 seamless. Only a few components between the CC2530 andCC2591 necessary for RF matching For situation with extreme mismatch(VSWR 6: 1 till 12: 1out-of-band as shown in Figure 6.2) it is recommended to include all the components asshown in Figure 5.1ISTRUMENTSPage 9 of 19SWRA308ANote that the PCB transmission lines that connect the two devices also are part of the RFmatching. It is therefore important to copy the distance between the devices, the transmissionlines and the stack-up of the PCB according to the reference design to ensure optimumperformanceThe network between the CC2591 and the antenna(L111, C112, C111 C113 and L112matches the CC2591 to a 50 2 load and provides filtering to pass regulatory demands. C111also works as a dc-blockR151 is a bias resistor the bias resistor is used to set an accurate bias current for internaluse in the cc2591The TI reference design contains two antenna options. As default, the Sma connector isconnected to the output of CC2591 through a 0 Q2 resistor. This resistor can be soldered offand rotated 90 clockwise in order to connect to the PCB antenna, which is a planar invertedF antenna(PIFA). Note that all testing and characterization has been done using the SMAconnector. The PCB antenna has only been functionally tested by establishing a link betweentwo EMs. Please refer to the antenna selection guide [6] and the Inverted F antenna designnote [7 for further details on the antenna solutionsISTRUMENTSPage 10 of 19SWRA308A
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