摘要
射频(RF)信号收发器是MRI 谱仪的重要组成部分,它负责MR 信号的接收和RF脉冲的调制发射。本论文旨在研究全数字高性能MRI射频收发器的原理、算法和硬件实现。
首先,本文从信号处理的角度系统的描述了MRI 射频信号收发器的原理和算法。提出全数字正交解调和多级滤波抽取算法相结合用于高精度MR 信号接收。通过分析对比各种脉冲波形设计和幅度调制方法,提出了Gaussian-Sinc 脉冲和SLR 算法结合解决脉冲波形设计问题。在分析双边带和单边带调制的性能后,采用移相法实现RF 脉冲的单边带幅度调制,并给出了具体的实现算法和仿真。
其次,基于软件无线电提出了一个全数字新型MRI 射频收发器硬件设计方案。这个新方案以高速AD、DA 转换器为基础,采用DSP/FPGA 器件作为系统核心,因而可以获得高精度和极大的灵活性。通过对系统的要求和难点的详细分析,给出了详细的硬件系统模块图。
最后,利用TMS320C6713DSK 为硬件平台,对系统中的DSP 模块进行了模拟和仿真。采用C 语言和汇编程序混合编程完成了多级滤波抽取算法的实现和优化,在整个处理过程中采用单精度浮点数据格式,提高了处理精度。C6713DSK板上的仿真结果验证了DSP 模块中算法的正确性和实时性。
RF signal transceiver is an important component of MRI spectrometer. It is responsible for the receive of MR signal and the transmit of RF pulse. This dissertation focused on the research of all-digital RF signal transceiver with high performance, including principles, algorithms and hardware implementation.
Firstly, the principles and algorithms of MRI signal transceiver were described and designed. An new algorithm combined all-digital quadrature demodulation and multi-stage decimation was presented in detail. By comparing and analyzing several shaped pulse design methods were compared and analyzed, and a composite method was presented for various MRI pulse sequences. After comparing with the performance of double sideband modulation and single sideband modulation, Single sideband modulation based on phasing was used for RF pulse modulation, which can cut down the peak power of RF pulse transmitter and achieve a precise phase.
Secondly, a novel MRI RF transmitter hardware architecture based on software-radio idea was presented, which used DSP and FPGA devices including high speed ADC/DAC chipsets. Advantages of this solution are of high precision and good flexibility. After the system level design and concerns were analyzed, the detailed chart of hardware platform was given.
Finally, DSP module simulation based on TMS320C6713 DSK was demonstrated in detail. An optimized filter-decitmation method was established and implemented with a DSP program in ANSI C and inline assembly, and Single-precision floating-point format was used in the whole process so that large dynamic range and high processing precision are achieved. The result of simulation on 6713DSK proved that this algorithm satisfied the real-time requirement.
引文
[1] 赵喜平,核磁共振成像系统的原理及其应用,科学出版社,2000 年
[2] Marinus T.Vlaardingerbroek, Jacques A.den Boer; Magnetic resonance imaging: theory and practice, Berlin; New York, Springer, c2003.
[3] RI NMR user manual; 2000.
[4] http://www.bruker-biospin.de/NMR/avance/
[5] RI DRX Hardware user manual; 2000
[6] 张岩LW003979 武汉数学与物理所,博士论文,固液两用高分辨率NMR谱仪的研制和应用1999
[7] 谭萍LW003987 武汉数学与物理所,硕士论文,数字信号处理在NMR 谱仪中的应用2000
[8] 李鲠颖等,数字正交检测和过采样的结合,波谱学杂志,2000,17(1):73-78
[9] 蒋瑜等,核磁共振谱仪技术中的高速数据采集,波谱学杂志,2001,18(3):269-274
[10]蒋赟等,用于核磁共振的直接数字合成频率源,波谱学杂志,2001,18(4):351-355
[11]晏小龙,台式核磁共振小谱仪的研制[D],上海:华东师范大学,2001
[12]肖鹏飞等,台式磁共振成像系统的研制[J],波谱学杂志,2002,19(4):345-352
[13]杨文辉,王慧贤,基于软件无线电的核四极矩谱仪设计,波谱学杂志,2003, 20(1): 51-56
[14]LIANG Z P, PAUL C.LAUTERBUR, Principles of Magnetic Resonance Imaging: a signal processing perspective[M], New York: IEEE PRESS, 2000
[15]杨小牛楼才义等, 软件无线电原理与应用, 电子工业出版社,2001 年1 月第一版
[16]G.A Wright, signal acquisition and processing for magnetic resonance imaging,IEEE 1994, p523-527
[17]S.J.Riederer,R.F Busse,real-time signal processing techniques in MRI, IEEE 2001 Proceeding of the 23th annual EMBS International Conference p2240-2243
[18]Stephen J,Riederer, Recent developments in real time MRI techniques and applications, p33-38
[19]刘朝阳,谭萍,裘鉴卿, 叶朝辉.核磁共振谱仪数字接收机的原理与实现[J],波谱学杂志, 2000,17(2):161-165.
[20]Bennett C,Wong, Henry Samueli, A 200MHz all digital QAM modulator and demodulator in 1.2um CMOS for digital radio applications, IEEE Journal of solid state circuit,VOL.12.DECEMBER 1991, P1970--1980
[21]John C. Hoenning, Lawrence E.crooks, Mitsuaki arakawa; A Floating point digital receiver for MRI[J],IEEE Trans. Biomedical Engineering, JULY 2002, 49 (7): 689-693.
[22]GUO guirong,Zhuang zhaowen,Wang feixue,Mixer-free all digital quadrature demodulation, proceeding of ICSP 98 ,P1704-1707
[23]宗孔德,多抽样率信号处理。清华大学出版社,1996
[24]刘益成罗维炳等信号处理与过抽样转换器电子工业出版社1997
[25]Koichi ICHIGE,Kiyoshi UEDA, a new estimation formula for mimimum filter length of optimum fir low-pass digital filters,International Conference on information,communications and signal processing ICICS’97
[26]Koichi Ichige; Accurate Estimation of Minimum Filter Length for Optimum FIR Digital Filters, IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS—II: ANALOG AND DIGITAL SIGNAL PROCESSING, VOL. 47, NO. 10, OCTOBER 2000
[27]Uegene,An Economical Class of Digital Filters for Decimation and Interpolation IEEE Transaction on acoustics,speech,and signal processing, VOL. ASSP-29, NO. 2, APRIL 1981 p155-162
[28]D. I. Hoult, the solution of the bloch equations in the presence of a varying B1 field: An approach to selective pulse analysis, J. Magnet.Resonance, vol.35, pp.66-68, 1979.
[29]M. Shinnar, L.bolinger, and J.S Leigh, “the use of finite impulse response filters in pulse design”, Magn.Reson. Med., vol. 12, pp.81-87,1989
[30]J. Pauly, P. Le Roux, D. Nishimura, and A. Macovski, “Parameter relations for the Shinnar–Le Roux selective excitation pulse design algorithm,”IEEE Trans. Med. Imag., vol. 10, pp. 53–65, Mar. 1991.
[31]Intelligent instrumentation for selective pulse excitation in NMR imaging H Jazayeri-Rad et al 1987 J. Phys. E: Sci. Instrum. (20) 643-648
[32]PatrickN.Morgan; Real-Time Cardiac MRI Using DSP’s, IEEE TRANSACTIONS ON MEDICAL IMAGING, VOL. 18, NO. 7, JULY 1999 649-653
[33]Stephen J. Riederer, Current Technical Development of Magnetic Resonance Imaging, IEEE engineering in medicine and biology September, 2000
[34]James A.Bankson,Mark.A.Griswold,SMASH imaging with an eight element multiplexed RF coil array ,Magnetic resonance materials in physics,Biology and Medicine 10 2000,93-104
[35]DRX hardware user manual, Resonance Instruments Ltd, 2001
[36]Alan Y. Kwentus, Zhong N J,Alan N.Willson, Application of filter sharpening to cascaded integrator-comb decimation filters[J], IEEE Trans. Signal Processing, Feb 1997, 45(2):457—467.
[37]A.V. 奥本海默信号与系统西安交通大学出版社1985 年
[38]现代通信原理[M] 曹志刚, 钱亚生著北京清华大学出版社1992.8
[39]A comparison of SSB-SC and conventional AM under a peak power limitation Bedrosian, E., Sollfrey, W., Communications, IEEE Transactions on Volume 37, Issue 1, Jan. 1989 Page(s):1–5
[40]Spectral Properties of Single-Sideband Angle Modulation Mazo,J.Salz;J.Communications,IEEE Transactions, Volume 16, Issue 1, Feb 1968 Page(s): 52–62
[41]P Devoulon, C Delon-Martin, A highly linear pulse shape modulator for NMR applications, measurement science and technology, 4(1993),1029-1032
[42]J.Tierney, C.M.Radre, and B.Gold A Digital Frequency Synthesizer IEEE Transactions on Audio and Electroacoustics, March 1971
[43]D.A. Sunderland, R. A. Strauch, S. S. Wharfield, H. T. Perterson, and C. R. Cole, CMOS/SOS frequency synthesizer LSI circuit for spread spectrum communications, IEEE Journal of Solid State Circuits, vol. SC-19, pp. 497-505, Aug. 1984.
[44]L. A. Weaver and R. J. Kerr, High resolution phase to sine amplitude conversion, U.S. Patent 4 905 177, Feb. 27, 1990.
[45]H. T. Nicholas III and H. Samueli, A 150-MHz direct digital frequency synthesizer in 1.25um CMOS with -90dB spurious performance, IEEE J. Solid-State Circuits, vol. 26, pp. 1959–1969, Dec. 1991.
[46]J.Vankka, A direct digital synthesizer with an on-chip D/A converter, IEEE J. Solid-State Circuits, vol. 33, pp. 218–227, Feb. 1998.
[47]Yamagishi, A.; Ishikawa, M.; A 2-V, 2-GHz low-power direct digital frequency synthesizer chip-set for wireless communication Solid-State Circuits, IEEE Journal of, Volume: 33 Issue: 2 Page(s): 210 –217, Feb. 1998
[48]M. Sodagar and G. R. Lahihi, Mapping from phase to sine-amplitude in direct digital frequency synthesizer using parabolic approximation, IEEE Analog and Digital Signal Processing, vol. 47, No-12, pp. 1452-1457,Dec. 2000.
[49]沈泊,一种适用于数字视频编码器的高性能直接数字频率合成器;半导体学报. 2001. 06 p796-799
[50]Yong Sin Kim; Sung-Mo Kang; Multiple trigonometric approximation of sine-amplitude with small ROM size for direct digital frequency synthesizers;VLSI Design, 2003. Proceeding. Pages:261–265 , 16th International Conference on , 4-8 Jan. 2003
[51]孟祥育王友钊一种基于CORDIC算法的高精度数控振荡器的ASIC设计微电子学.2003.033(005).458-461
[52]Wang Yang. A direct digital frequency synthesizer based on CORDIC algorithm implemented with FPGA. ASIC, 2003. Proceedings.5th International Conference on, Volume: 2,21-24 Oct.2003 Vol.2 Pages:832-835
[53]Rupert Baines, The DSP bottleneck, IEEE Communications Magazine, 1995.
[54]IDT application note AN-409,2004
[55]TMS320C6713 DATASHEET, 2003
[56]TMS320C6000 Peripherals Reference Guide, 2003
[57]TMS320C6000 CPU and Instruction Set Reference guide, 2003
[58]TMS320C6000 Optimizing Compiler User's Guide, Texas Instruments, 2003
[59]AD9244-65 datasheet,Analog Devices,1999
[60]AD9752, datasheet, Analog Devices ,1999
[61]HSP45106 datasheet, INTERSIL,1999
[62]Oh,H.J;Sunbin Kim;Ginkyu Choi;Lee,Y.H.;On the use of interpolated second-order polynomials for efficient filter design in programmable downconversion, Selected Areas in Communications, IEEE Journal on