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The status of microwave research, development and manufacturing in China.

High Microwave Power Generation

A great amount of work has been done in the area of high microwave power generation in China. New theory has ushered in the electronic device technology. One such technology is the kinetic theory of electron cyclotron resonance (ECRM) based on the guiding center coordinate system.|1,2~ Rigorous derivations of the dispersion equation of ECRM have been derived on the guiding center coordinate system, showing that this solution is compact and rigorous.|3-5~ In addition, new structures have appeared, such as harmonic gyrotrons|6-8~ with excellent experimental research work carried out. A 75 GHz single cavity is under construction. It will be used by one of the most important laboratories, the Chinese West-South Physics Institute of High Energy in its Tokamak project.|2~ Appendix A lists papers that address this area.

High Microwave Power Transmission

The transmission of high microwave power, even over a short path from the output of the generator to the antenna, and the maintenance of an undistorted pulse form in a guiding system pose new problems for the microwave engineer. A circular coaxial line supporting only a TEM mode would be a good high power transmission line because of its circumferential uniform field distribution. The disadvantage of this line is its strong field intensity and high power loss in its inner conductor. Therefore, the rectangular coaxial line had to be worked on in order to find a new line cross section, in which one of the boundaries is flatter, carries smaller electric field intensity and gives large space between the two conductors when used as a heater. Works published in the area of high microwave power transmission include Microwave Networks, Microwave Theory and Technique, and Electromagnetic Field Engineering. All three books are written in Chinese.

Monitoring of the Earth by Satellites

A delegation of 13 microwave experts from the United States voiced their impression of their visit to China in 1983.|9~ Their observations included 17 set-ups for making measurements at X-band, powered by various Gunn oscillators and klystrons. The equipment looks similar to that which can be seen in the United States, but it has all been made in China. A system for evaluating the reflectivity of crops from an airborne CW FM radar is underway. Some of the these crops are cycled as many as three, even five times a year.

Currently, specialized optical measuring equipment for China's space program has been set up. The infrared test equipment will be used by the Remote Sensing Institute in Beijing. This equipment uses geostationary satellites to monitor the country's weather patterns and natural land resources, including crop development. This equipment also measures the optical transfer function and modulation transfer function of lenses and lens systems operating in the visible and infrared spectrum.

Electrostatic Field Theory

Electrostatic field problems in microwave field theory are important for the solutions of TEM transmission line problems and attenuation and scattering problems of EM waves in media consisting of small layered particles, such as sleet or wet snow. Static analyses of such structures are essential to finding out the polarizability of the individual particles, assuming that there is no interaction of particles at the start, that is, there is relatively sparse distribution of particles. To improve the computation of polarization moments, the interactions of neighboring particles have to be studied.

The most uniform particle is the sphere, such as the melting ice sphere. In the melting ice sphere, the ice core and water shell play different roles in the attenuation and scattering. Due to the high permittivity of water, a thin layer of water is capable of screening the ice core. These static problems have been extensively investigated. The study on complete or incomplete spheres|10,11~ has been pursued for some time. Appendix B lists literature on these investigations.

Microwave Field Theory

Electromagnetic fields in various media and along different guiding structures have been studied in China. A partial list of literature in this field composes Appendix C.

Optoelectronic Technology

Since 1970, China has experienced rapid growth in optoelectronic research, production, installation and education. Laser technology and products were displayed last year in Beijing. This display included state-of-the-art laser systems, such as components and modules, medical systems, measurement and test equipment, and infrared technology and products. The exhibition, the first of its kind in China, promotes the trade of laser and optoelectronic products and Sino-foreign co-operation in the field. In addition, sales, business discussions and technological seminars were included as part of the six-day gathering at the Beijing International Exhibition Centre. The exhibition was a joint effort by the Chinese State Planning Commission, State Science and Technology Commission, State Education Commission, Ministry of Machine-Building and Electronics Industry and other high-powered government offices and organizations.

Recently, a full monolithic GaAs Gunn VCO has been fabricated. It incorporates a Gunn diode, a Schottky diode, matching network and bias on a single 5 x 3 mm integrated chip. The Gunn oscillator delivers 3.03 mW at 34.6 GHz. The tuning band is 90 MHz. This is the first report on mm-wave MMIC VCOs in China.|12~

A new analytical model of a short channel GaAs MESFET has been proposed. The model shows results that agree better with the experiments than those of the complete velocity saturation and the square-law models.|12~ Appendix D lists other papers of this seminar

Journal of Electronic Science and Technology of China

The University of Electronic Science and Technology of China is an influential school in the field of electronic technology. It confers the largest number of PhD degrees in this field. Selected papers recently published in its 31-year-old journal are listed in Appendix E.

Quarterly Journal of Microwaves, China

The following is a list of selected papers from the Quarterly Journal of Microwaves, China, Vol. 30, No. 3, 1992. The papers' titles and authors are provided, as well as abstracts describing the articles.

Lin Qinan and Wu Yongshi, "A New Improvement of Computer-Aided Design of Mixed Lumped Distributed Networks." A synthesis procedure of mixed lumped-distributed networks with the building block concept is developed in this paper. By means of impedance and frequency transformations, the mixed lumped-distributed two-port networks become generalized unit elements, so the mixed lumped-distributed networks can be synthesized conveniently on the basis of Richards theory. Using the results of the lossless design as the initial value, according to the cascade matrix method to optimize elements involving losses, the design precision can be improved.

Gu Changqing, "Spectral Domain Immittance Approach for Characteristics Analysis of Symmetrical Bilateral Finline Loaded with Biaxial Medium." This paper describes biaxial medium loaded symmetrical bilateral finline. This finline is analyzed and an equivalent circuit is used to represent it when the couple between TE mode and TM mode is neglected. Therefore, the field problem is transformed to a circuit problem, and the deduce of the characteristic equation is simplified. The ideal transformers in a network equate the mode match condition of the interface between the isotropic and biaxial medium. Finally, the effective dielectric constants of the symmetrical bilateral finline loaded with biaxial medium have been calculated numerically. Numerical results confirm that the approximation used in this paper is reasonable and of high accuracy.

Wang Zhi-Liang, "On the Expansion of First-Kind Spherical Wave Functions in Terms of Cylindrical Wave Functions." An expansion of the first-kind scalar spherical wave functions in terms of the scalar cylindrical wave functions is given in this paper. According to the definition of vector wave functions, the expansions of the first-kind vector spherical wave functions in terms of the vector cylindrical wave functions are obtained. These expansions are useful in solving the problems of EM radiation and scattering with the complex boundary.

Wang Changqing and Zhu Xili, "The Convergence of the Finite-Difference Time-Domain (FD-TD) Method." This paper discusses the convergence problem of the FD-TD method through some computation examples. The electromagnetic field distribution in an infinite dielectric cylinder illuminated by plane wave has been calculated. The results of the calculations with various space steps and time steps are compared with their analytical results. The comparison shows that the FD-TD method has a good convergence performance. EM energy absorbed by a two-dimensional nonuniform man block model with a different space resolution has been calculated and shows that the EM distribution still has good convergence, even for highly nonuniform medium. This paper provides the basis in one aspect for selection of the steps of the meshes.

Xu Jin-ping and Liang Changhong, "Equivalent Impedances of Inductive Diaphragms and Strips with Finite Conductivity." Traditional analyses for inductive diaphragms and strips in rectangular waveguides have been restricted to the case of perfectly conducting metal sheets. In this paper, the diaphragms and strips with finite conductivity are studied by the method of lines. The equivalent resistances and reactances of the discontinuities can be calculated simultaneously. As an example of their applications, a lossy resonant cavity constructed with two symmetrical diaphragms is analyzed.

Chen Sui-bin and Liu Yony-Pu, "A Stripline Coupler with Small Aperture." In this paper, a closed expression of the normalized electric field in stripline is derived from the potential function obtained by conformal transformation. The formulas of coupling through a circular aperture on the common wall between striplines are presented by a small aperture coupling theory. Theoretical results agree well with those of the experiments.

Xin-she Yin, "Accurate Determination of Arbitrary Resonant Frequencies of Dielectric-Loaded Cavities Using Mode Matching Method." This paper presents simplified and rigorous mode matching analyses for accurate determination of the arbitrary resonant frequency of a circular dielectric resonator shielded in a coaxial circular conducting box with both symmetrical and asymmetrical structures. Formulas are given in detail. The calculation results agree closely with measurements and other calculations.

Shen Tin-gen, "Direct Soliton Solution of Loss Fiber." This paper evaluates an elementary soliton solution of nonlinear transferring equation of lossy optical fiber using a simple mathematical method.

The International Community

The study of microwaves has reached a sufficient level of interest in China that Chinese research is now being presented in greater amounts in the international science community. At the 1992 IEEE International Microwave Symposium, Albuquerque, NM, 17 papers by Chinese scientists and their colleagues were part of the technical program.

Topics of the 1992 session included coaxial probe modeling in waveguides and cavities; high |T.sub.c~ superconductor-sapphire microwave resonators; superconducting strip transmission lines; E-plane waveguide junction analysis; optoelectronic mm-wave finline switches; optically-controlled Gunn subharmonic oscillators; microstrip and suspended substrate line discontinuity analysis; coupled microstrip lines; Doppler radar using inverted strip dielectric waveguide; cylindrical dielectric resonators; photoconductive switches; FD-TD full-wave analyzers; waveguide E-plane high-temperature semiconductor insert filters; hybrid ring couplers; annular ring waveguide cavities; laser-diode-based photoconductive harmonic mixers; and five-mode single spherical cavity microwave filters. At the 1993 IEEE International Microwave Symposium, Atlanta, GA, five papers by Chinese authors or co-authors were given. Topics included the surface roughness of metals; distributed amplifiers; TM triple-mode cavities; circuit optimization; and Valley microstrip lines in MMICs.

References

1. Liu Shenggang, Relativistic Electronics, 1987, Science Press (in Chinese).

2. Liu Shenggang, Progress in Gyro-Electronic Masers and Gyrotrons, 1988, Sichuan Press (in Chinese).

3. Liu Shenggang, "Electrostatic Electron-Cyclotron Resonance Maser," Scientia Sinica (Series A), Vol. XXX, No. 4, 1987, pp. 413-419.

4. Liu Shenggang and Liu Hong-xiu, "Electrostatic Free-Electron Laser," Physical Review A, Vol. 36, No. 8, p. 3837-3844.

5. Liu Shenggang and Xie Wenkai, "3-Mirror Quasi-Optical Power Combining of mm-Wave Sources," Int. J. Electronics, Vol. 65, No. 3, 1988, pp. 717-724.

6. Li Hongfu, Xu Fengling and Liu Shenggang, "Theory of Harmonic Gyrotron with Multiconductors Structure," Int. J. Elect., Vol. 65, No. 3, pp. 409-418.

7. Liu Shenggang and Ouyang Zhengbiao, "Free-Electron Laser-Electrostatic Electron Cyclotron Resonance Maser Hybrids," Phys. Fluids, Vol. 31, No. 5, May 1988, pp. 1280-1285.

8. Liu Shenggang, Ouyang Zhengbiao and Cheng Xiaodong, "The Orbit Theory of Electrostatic Electron Cyclotron Resonance Masers," IEEE Trans. on Plasma Science, Vol. 16, No. 2, April 1988, pp. 275-280.

9. Theodore S. Saad, "MTT-S China Diary: Shanghai," Microwave Journal, Vol. 26, No. 12, December 1983.

10. Weigan Lin, "The Rotational Degenerated Bipolar Coordinate System and its New Applications," Journal of Electrostatics, Vol. 26, 1991, pp. 21-26.

11. Weigan Lin, "The Electrostatic Problem of a Portion of a Multilayer Dielectric Sphere in a Uniform Field," Microwave and Optical Technology Letters, Vol. 4, No. 3, Feb. 1991, pp. 123-128.

12. "Ka-Band GaAs Gunn MMIC VCO" by Lai Ping, Chen Yan, Xie Zhonghua, Wang Maosen and Lin Jinting, Research and Progress of Solid-State Electronics, Vol. 12, No. 3, Aug. 1992, pp. 179-203; and "A Model of GaAs MESFET's Direct Current Characteristics" by Huang Qingan and Tong Qinyi, Research and Progress of Solid-State Electronics, Vol. 12, No. 3, Aug. 1992, pp. 230-234.

Appendix A: High Microwave Power Generation Articles

Liu Shenggang, Relativistic Electronics, 1987, Science Press (in Chinese).

Liu Shenggang, Progress in GyroElectronic Masers and Gyrotrons, 1988, Sichuan Press (in Chinese).

Liu Shenggang, "Electrostatic Electron-Cyclotron Resonance Maser," Scientia Sinica (Series A), Vol. XXX, No. 4, 1987, pp. 413-419.

Liu Shenggang and Liu Hong-xiu, "Electrostatic Free-Electron Laser," Physical Review A, Vol. 36, No. 8, 1987, pp. 3837-3844.

Liu Shenggang and Xie Wenkai, "3-Mirror Quasi-Optical Power Combining of mm-Wave Sources," Int. J. Electronics, Vol. 65, No. 3, 1988, pp. 717-724.

Li Hongfu, Xu Fengling and Liu Shenggang, "Theory of Harmonic Gyrotron with Multiconductors Structure," Int. J. Electronics, Vol. 65, No. 3, 1988, pp. 409-418.

Liu Shenggang and Ouyang Zhengbiao, "Free-Electron Laser-Electrostatic Electron Cyclotron Resonance Maser Hybrids," Phys. Fluids, Vol. 31, No. 5, May 1988, pp. 1280-1285.

Liu Shenggang, Ouyang Zhengbiao and Cheng Xiaodong, "The Orbit Theory of Electrostatic Electron Cyclotron Resonance Masers," IEEE Trans. on Plasma Science, Vol. 16, No. 2, April 1988, pp. 275-280.

Appendix B: Electrostatic Field Theory Literature

Cheng Dajun and Xue Liangjin, "Electrostatic Question of the Grounded Conducting Rotational Cyclide," Journal of University of Electronic Science and Technology of China, Vol. 20, Oct. 1991, pp. 481-484.

Weigan Lin, "Analytic Solutions to the Electrostatic Problems of Two Dielectric Spheres," J. Appl. Phys., Vol. 67, No. 3, 1990, pp. 1160-1166.

Weigan Lin, "The Rotational Degenerated Bipolar Coordinate System and its New Applications," Journal of Electrostatics, Vol. 26, 1991, pp. 21-26.

B.Y. Zhou (Xi'an, Shaanxi, China), "Relations of Field Magnitudes at Two Points Along a Flux Line in the Electrostatic Field," Journal of Electrostatics, Vol. 26, 1991, pp. 37-46.

Wu Zong-han and Xie Xi-shun, "A Method to Measure Average Charge Depth in Bio-Electrets," Journal of Electrostatics, Vol. 26, 1991, pp. 245-249.

Weigan Lin, "The Electrostatic Problem of a Portion of a Multilayer Dielectric Sphere in a Uniform Field," Microwave and Optical Technology Letters, Vol. 4, No. 3, Feb. 1991, pp. 123-128.

Appendix C: Microwave Field Theory Publications

Y. Huang, L. Xue and Weigan Lin, "Excel Singular Integral Equation Approach for Planar Transmission Lines," Electronics Letters, 15 March 1990, Vol. 26, No. 6, pp. 300-360.

Yafel Huang, Liangjin Xue and Weigan Lin, "Accurate Solutions for Planar Transmission Lines by an Improved Singular Integral Equation Technique," Microwave and Optical Technology Letters, Vol. 3, No. 6, June 1990, pp. 208-209.

Weigan Lin and W. Dou, "An Exact Electromagnetic Field Theory for the Broadband H-Plane Waveguide Junction Circulators," Alta Frequenza, Vol. LVIII, No. 2, March-April 1989, pp. 225-237.

Weigan Lin, "Mode Theory of Uniform Waveguides Filled With Dielectric Inhomogenous Along One Direction Only," J. Appl. Phys., Vol. 52, 1981, pp. 3640-3645.

Weigan Lin, "Contributions to the Theory of Elliptical Waveguides," Scientia Sinica, Vol. 22, No. 10, 1979, pp. 27-39.

Weigan Lin, "The Problem of a Conducting Sphere Resting on an Earthed Plane in a Uniform Perpendicular Field and its Applications," Electron. Lett., Vol. 20, No. 3, 1984, pp. 122-124.

Weigan Lin, "A New Transmission Line of Round Conductor and Parallel Plane with Symmetrically Placed Slit," IEEE Trans. Microwave Theory Tech., Vol. 33, No. 8, 1985, pp. 739-740.

Weigan Lin, "Computation of the Parallel-Plate Capacitor with Symmetrically Placed Unequal Plates," IEEE Trans. Microwave Theory Tech., Vol. 33, No. 9, 1985, pp. 800-807.

Weigan Lin, "Electromagnetic Wave Propagating in Uniform Waveguides Containing Inhomogenous Dielectric," IEEE Trans. Microwave Theory Tech., Vol. 28, No. 4, 1980, pp. 339-347.

Weigan Lin, "A Critical Study of the Coaxial Transmission Line Utilizing Conductors of Both Circular and Square Cross-Section," IEEE Trans. Microwave Theory Techniques, Vol. 30, No. 11, 1982, pp. 1981-1988.

Weigan Lin, "Low-Frequency Scattering of Dielectric Cylinders," IEEE Trans. Microwave Theory Tech., Vol. 28, No. 11, 1980, pp. 1190-1204.

D. Cheng and L. Xue, "Radiation of Elementary Dipole Sources in Stratified Chiral Media."

D. Cheng, L. Xue and R. Xu, "Radiation of Elementary Time-Harmonic Current in Chiral Half Space," Microwave Optical Technology Letters,

D. Cheng and L. Xue, "Dipole Radiation in the Presence of a Grounded Chiral Slab," Microwave Optical Technology Letters, Vol. 5, No. 2, Feb. 1992, pp. 65-68.

Inhomogeneities (Obstacles) and Discontinuities Lead to the Scattering of Guided Waves

Z.L. Wang and W.G. Lin, "Inelastic Scattering of Gaussian Beams by Active Molecules Embedded in a Sphere," Microwave Optical Technology Letters, Vol. 1, No. 5, 1988, pp. 179-182.

Z.L. Wang and Weigan Lin, "Elastic and Inelastic Scattering by an Arbitrary Body Filled with Active Molecules: Method of Eigenfunction Expansion in Integral Equation," Microwave Optical Technology Letters, Vol. 2, No. 2, 1989, pp. 70-74.

Z.L. Wang and Weigan Lin, "Elastic Multiple Scattering by Randomly Distributed Spherical Scatterings," Microwave Optical Technology Letters, Vol. 1, No. 10, 1988, pp. 380-384.

Z.L. Wang and Weigan Lin, "Inelastic Multiple Scattering by Active Molecules Embedded in Randomly Distributed Spherical Scatterers," Microwave Optical Technology Letters, Vol. 2, No. 1, 1989, pp. 23-26.

Z.L. Wang and Weigan Lin, "Raman and Fluorescent Scattering by Active Molecules Embedded in a Monomode Optical Fiber," J. Opt. Soc. Am. B., to be published.

Z.L. Wang, W. Ren and Weigan Lin, "Raman Scattering by Active Molecules Embedded in a Sphere in a Monomode Optical," J. Electromagnetic Waves and Application, to be published.

Weigan Lin, Y. Liu and Y. Zhao, "The Electrostatic Problem of a Portion of a Multilayer Dielectric Sphere in a Uniform Field," Microwave Optical Technology Letters, Vol. 4, No. 3, Feb. 1991, pp. 123-128.

Wei Ren, Chenghua Wan and Weigan Lin, "Geometrical Optics Analysis of Electromagnetic-missile Backscattering," J. Appl. Phys., Vol. 72, No. 5, 1 Sept. 1992, pp. 1-2.

Wei Ren, "Contributions to the Electromagnetic Wave Theory of Bounded Homogenous Anistropic Media," Physical Review, Vol. 24, Sept. 1992.

Y.H. Cheng and Weigan Lin, "Investigation of Rectangular Dielectric Waveguides: An Iteratively Equivalent Index Method," IEE Proceedings, Vol. 137, Pt. J, No. 5, Oct. 1990, pp. 323-329.

Appendix D: Technical Papers at the Bejing International Exhibition Centre

"Ka-Band GaAs Gunn MMIC VCO" by Lai Ping, Chen Yan, Xie Zhonghua, Wang Maosen and Lin Jinting, Research and Progress of Solid-State Electronics, Vol. 12, No. 3, Aug. 1992, pp. 179-203; and "A Model of GaAs MESFET's Direct Current Characteristics" by Huang Qingan and Tong Qinyi, Research and Progress of Solid-State Electronics, Vol. 12, No. 3, Aug. 1992, pp. 230-234.

Z.Y. Yee and Weigan Lin, "A New Way to Optically Control Millimeter-Wave Oscillators," Acta Electronica Sinica, Vol. 18, No. 6, Nov. 1990, pp. 97-98.

Guo Qi, Zhou Guosheng, Wen Qun and Weigan Lin, "Propagation Properties of a Pair of Soliton Pulses in a Fiber," Acta Optical Sinica, Vol. 10, No. 7, 1990, pp. 651-656.

X.B. Luo, L. Hu and Weigan Lin, "Very High-Isolation All-Fiber Wavelength-Division Multi-Demultiplexer," Microwave and Optical Technology Letters, Vol. 3, No. 4, April 1990, pp. 116-117.

Appendix E: Journal of Electronic Science and Technology of China: Selected Papers

Liu Shenggang, "Linear Theory of Free Electron Laser," J. of Univ. of Electronic Science and Tech., Vol. 19, No. 1, 1990, p. 1.

Jia Baofu, "Research of Coal Moisture Measurement Using Microwave Reflection Method," J. of Univ. of Electronic Science and Tech., Vol. 19, No. 1, 1990, p. 22.

Chen Tianqi and Fang Xianghong, "An Algorithm for Adaptive Multi-Beam-former," J. of Univ. of Electronic Science and Tech., Vol. 19, No. 2, 1990, p. 127.

Deng Shuhui and Wang Dinghua, "Plate-Like Antenna," J. of Univ. of Electronic Science and Tech., Vol. 19, No. 2, 1990, p. 169.

Song Ruhua, Wang Junbo and Wu Jiang, "The Imaging Properties of Pseudo-Conjugator," J. of Univ. of Electronic Science and Tech., Vol. 19, No. 2, 1990, p. 175.

Liu Shenggang, "Space-Charge Wave Theory of the Free Electron Laser with Longitudinal Electrical Field Component," J. of Univ. of Electronic Science and Tech., Vol. 19, No. 3, 1990, p. 225.

Ruan Yingzheng, "Synthesis of Reflected Seismic Wavefield by Complex Huyghens' Principle," J. of Univ. of Electronic Science and Tech., Vol. 19, No. 4, 1990, p. 341.

Li Xiang and Li Hongfu, "Analysis of TM Mode in Azimuthal Multiconductor Structure," J. of Univ. of Electronic Science and Tech., Vol. 19, No. 4, 1990, p. 358.

Ruan Chengli, "Antistealth and EM Wave Propagation," J. of Univ. of Electronic Science and Tech., Vol. 19, No. 6, 1990, p. 563.

Xie Wenkai and Zhu Xiongwei, "A Study on the Space-Charge-Limit Current in Waveguide and Resonance Cavity," J. of Univ. of Electronic Science and Tech., Vol. 20, No. 3, 1991, p. 281.

Luo Xiaobing and Hu Li, "Coupled-Mode Analysis of Tapered Dielectric Optical Waveguides," J. of Univ. of Electronic Science and Tech., Vol. 20, No. 3, 1991, p. 288.

Liu Shenggang, "Kinetic Theory of ECRM with Azimuthal Standing Wave," J. of Univ. of Electronic Science and Tech., Vol. 20, No. 5, 1991, p. 455.

Shi Zhendong and Yang Shiwen, "Analysis of Surface Wave on Conducting Plane Covered with Lossy Media," J. of Univ. of Electronic Science and Tech., Vol. 20, No. 6, 1991, p. 593.

Lin Weigan and Jin Hang, "Green's Function in the Domains Bounded by Two Intersecting Spheres," J. of Univ. of Electronic Science and Tech., Vol. 19, No. 3, 1990, p. 232.

Weigan Lin graduated from Tsing Hua University, China and received his PhD from UC, Berkeley in 1950. From 1948 to 1951, he was a lecturer in EE at UC Berkeley. Since then, he has been a professor in China. In 1981, he was a visiting professor in the EECS deparment at UC Berkeley. In the same year, he was elected a member of the Academy of Sciences fo China. In 1984, he was a visiting professor at the University of Manitoba, Canada. In 1990, he was invited to become a member of the Electromagnetic Academy of MIT, Cambridge. Lin is a member of the Chinese Academy of Sciences.
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Title Annotation:Special Report
Author:Weigan Lin
Publication:Microwave Journal
Date:Oct 1, 1993
Words:3713
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