关于DSP的外文文献

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  文章介绍了以DSP芯片TMS320VC5509A作为其核心的实时心电信号采集系统。详细介绍了心电信号采集电路的设计。心电信号的模拟滤波和放大,然后从模拟域转换为数字域。最后,它经过DSP上的数字低通滤波显示在LCD上。收集到的心电数据能够真实地反映人类心脏的健康状况。该系统具有的优点:体积小,功耗小,成本低和实时处理。
Kening Wang et al. / Procedia Engineering 29(2012)3763-3767 3765 平十丰 条 LDO Fig. 2.(a)The preamplifier and driver circuit of right leg;(b)Band-pass filter circuit Fig2(a)shows the design of the preamplifier and driver circuit of right leg for the system. The gain of amplifier circuit can be calculated by formula 3-1RG is 5.1 K 32, and the gain G is about 10 G49.4k9 R 3.3 Band-pass filter circuit Band-pass filter circuit adopts feedback structure based second-order active rC filter [6]. The system achieves a 0.05-100Hz transmission bands by designing the series of a second-order active high-pass filter(HPF) and a second-order active low-pass filter(LPF) whose cut-off frequencies are 0.05Hz and 100Hz respectively with dual operational amplifier OPA2604, 0.05-100Hz band-pass filter circuit schematic diagram is shown in Fig2(b)It is implemented by using a dual operational amplifier OP A2604 For high-pass filter, the parameters are R&=Ro=68KQ2, C2l=C22=47uF, and the cut-off frequency is ≈0.05(Hz) R&Ro C2C22 If the gain k is l, then the quality factor Q is o (3) 3-K For low-pass filter, the parameters are Ro=Ru=1. 6KQ2, C,=C4=1uF and the cut-off frequency is ≈100(Hz) R,RCCa 3.450Hz notch filter In the process of ECG signal extraction, a band-stop filter is commonly used to restrain the 50Hz power frequency interference produced by outside or system itself, the band-stop filter is also called notch filter [7]. The double T-RC active notch filter is used in this system. It is an improved, Q value adjustable band stop double t active filter circuit. The circuit uses an amplifier to make a positive feedback in order to reduce the bandwidth which is the difference between it and the previous double-T notch filter. So the amplitude near both sides of the stop-band center frequency increases, quality factor Q can be regulated If the gain k is l, then the quality factor Q is 0.5 3-K (5 by potentiometer Rsl. The schematic diagram of 50Hz notch filter is shown in Fig4(a). The transfer function of the circuit is 3766 Kening Wang et al. / Procedia Engineering 29(2012)3763-3767 s2R2C2+1 s)s2R2C2+4(1-K)+1 Fig 4.(a)50Hz notch filter schematic diagram; (b)The main amplifier and voltage lifting circuit In the actual circuit, R is 6.8 and C is 0.47R=6.8KQ2,C=0.47u F, the center frequency is: ≈50(1z) 2TRC In the preamplifier circuits, we amplified ECG signal about 10 times, and then the main amplifier circuit should amplify it about 100 times to meet the requirements of post processing. The schematic diagram of main amplifier circuit is shown in Fig4. (b). In this design, the input range of the A/D converter we use is0- 3.3 V. In order to meet the A/D conversion range, we design a level lifting circuit. If we takeR,=lMQ2, Rs,=10.1KQ2, The magnification is R 100 (8) R 4.A/D conversion The TMS320VC5509A provide 10-bit ADC input interface of double-channel. This is a continuous approximation type ADC and its external reference voltage is 3.3 V. The ADC can be controlled by setting up four corresponding registers, ADCCtl, ADCDate, ADCC Ik Div and ADCClkCtl. In this system we use channel 1. According to the sampling theory, the sampling frequency must be more than or equal to twice as much as the signal frequency in order to obtain the digital signal without distortion. The maximum frequency of ECG signals is 100 Hz, so the sampling frequency must be more than 200 Hz The highest sampling frequency of this system is 21.5 KHz, so the system finally set sampling frequency as 360 Hz, which can meet the sampling theory [9, 10]. The system uses the adC in TMS320VC5509A which reduces system cost, and the stability is relatively better In the A/D conversion of ECG signal, we start sampling in ADC through setting ADC Start in ADC register, wait for completing data transformation by the enquiring the ADCBusy, obtain sampling data by read data from the ADCData register, the data of low-10-bit in ADCData is converted so the high six-bit should be resetted, the procedures are described below: Data in=ADCData: //Obtain data Data in&=0x03ff:// Data conversion 5. Digital filtering to Electrocardiological signal andTotal program flow In order to get more cleaner ECG signal, the system should adds an analog filter after the digital filter a0 100 HzFIR low-pass filter is designed to filter out-of-band noise by using frequency sampling method[8], whose stop-band attenuation can reach to 80 dB. If a 0.05- 100 Hz low pass filter is designed, the sampling density is too high, and calculation amount is too big, so it can't meet the real-time requirment. The software system uses C programming language and mixed language to program. The overall process of program is shown in Fig5(a) Kening Wang et al. / Procedia Engineering 29(2012)3763-3767 3767 Ivar Fig5. (a)The system flow chart 6. System test results The system uses Q15 to express integer and Q0 to express decimal [3]. The oscilloscope observation of ECG output signal is shown in Fig6(a).Real time ECG signal oflCd display is shown in Fig6(b) Fig. 6. a)ECG waveform of output; (b)ECG signal of LCD display This design adopts TMS320VC5509A with high cost performance as its core, which Completes ECG portable and low power consumption. Therefore, it has strong practical value CG acquisition system of signal acquisition, completes the filtering and real-time display achieves a Acknowledgements The author would like to acknowledge the support of the National Science Foundation of China (nsfc) under grant NO. 61162067 and NO. 20927114, and also the high school graduate tutor scientific research project of Gansu province under grant No. 1101-03 eferences [1] Liu hong-xia, WeI dong-fang Atmega . SCM ECG signal detection and pr rocessing system. Journal of Yunnan University(Natural science edition )2009, 31(S2): 248251 [2] Bahoura, M, Hassani, M, DSP implementation of Wavelet transfom for rael time ECG wave forms detection and heart rata analysis", Comput Mothods Programs Biomed, 52: 1, pp. 35-44., 1997 [3] WANG chun-mei.TMS320C55xDSP principle and application BeiJing: Publishing House of electronics industry, 2008 4]OPA2604-Dual FET-Input, Low Distortion OPERATIONAL AMPLIFIER. Burr-Brown Corporation, 1991 [5] AD620-Low Cost, Low Power Instrumentation Amplifier. Analog Device Inc. 1999 [6]YANG Zhi-min, Ma yi-de, ZHANG xin-guo. Modern circuit theory and design. BeiJing: Tsinghua university press [7] Cai kun, LU-yaosheng Based on the median filter for ECG baseline correction method. Information of Medical Equipment,2004,19(2):5-7 8]ICL7660--Switched-Capacitor Vollage Converters Maxin Integraled ProductS, 1994 9] DOU ming-tao. Data acquisition system based on the design of TMS320VC5402 Electronic measurement technology. 2004(4): 37-38 [10] ZHONG yin-bao, XIAO ying-bin, SHI chang-ning, Full ECG monitoring system design and Implementation Informationo Medical Equipment, 2006, 27(8): 46 [11 XUE nian-xi MATLAB in the application of digital signal processing. Beijing tsinghua university press, 2003

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