A DUAL-POLARIZED DENSE ARRAY FOR MIMO SYSTEM APPLICATIONS LU YIHAO NATIONAL UNIVERSITY OF SINGAPORE 2004 A DUAL-POLARIZED DENSE ARRAY FOR MIMO SYSTEM APPLICATIONS LU YIHAO (B.ENG , SHANGHAI JIAO TONG UNIVERSITY) A THESIS SUBMITTED FOR THE DEGREE OF MASTER OF ENGINEERING DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING NATIONAL UNIVERSITY OF SINGAPORE 2004 Dedicated to My Parents, Lu Xiao-Di and Zhu Yu-Ya Name: Lu Yihao Degree: M.Eng. Dept: Electrical and Computer Engineering Thesis Title: A Dual-Polarized Dense Array for MIMO System Applications Abstract This thesis examines the performance of dense antenna arrays in Multi-Input Multi-Output (MIMO) systems. An N-element antenna array is regarded as an N-port network with non-vanishing off-diagonal elements in the network parameter matrices, for example, the scattering parameter matrix. A modal expansion is then used to express the matrix in terms of mutually orthogonal eigenmodes. To facilitate the simultaneous removal of signal correlation and gain reduction due to the cross-talk, an approach, which employs an RF decoupling network at the array ports, is proposed. To verify the theory, a practical design of a novel, compact, four-port, dual-polarized aperture-coupled patch array with decoupling network is presented and tested. This antenna would be attractive for WLAN applications with limited antenna platforms such as PDAs, smart phones or laptop computers, where element spacing is significantly smaller than half a wavelength. Key word: Dense Antenna Array, Decoupling Network, Channel Correlation, Gain Reduction, Aperture-Coupled Patch Antenna, MIMO System Acknowledgements The deeply enriching experience that I have enjoyed during my master study at National University of Singapore (NUS), Singapore and Bergische Universität Wuppertal (BUW), Germany, is attributed to those people who have assisted and influenced my work and me. Firstly, I would like to take this opportunity to express my deepest gratefulness to my supervisors: Prof. Dr.–Ing. H.J. Chaloupka (BUW) and Prof. J.C. Coetzee (NUS), for their countless efforts on advising my research and helping me project my future career. They taught me not only the specific technologies on the project, but how to be a competent researcher-the most valuable thing I have ever learned- as well. I would also like to extend my gratitude to my colleagues in NUS and BUW. There are simply too many people to mention here, but I am particularly grateful to Xin Wang, Dietmar Eßer, Gregor Kotyrba, Martin Kaluza, Chua Ping Tyng, Chua Chee Parng, Lu Lu, Li Zhong-Chen, Chen Yuan, Ng Tiong Huat and Ewe Wei Bin, for many enjoyable hours of discussion and working. Most of all, I am grateful to my family. I am deeply grateful to my parents, Lu Xiao-Di and Zhu Yu-Ya. Thanks for their support and faith in me all the time. Without these strengths, I cannot adhere to my dream up to this day. They are my motivation. I dedicate this work to them. i Summary While conventional smart antennas improve the quality of one single data stream, a new multi-antenna technology known as Multi-Input Multi-Output (MIMO) offers multiple independent transmission channels, resulting in a channel capacity that increases linearly with the number of antenna elements. In a MIMO system, both the transmitting end and the receiving end are equipped with multiple antenna elements and space-time processing techniques are employed to improve the bit error rate and data rate. One problem arising in the practical implementation of MIMO systems is that the size and number of antenna elements are limited by the fixed volume of mobile stations such as PDAs, smart phones or laptop computers. This results in dense arrays with element spacing significantly smaller than half a wavelength. This in turn causes problems related to the correlation between signals of the transmission channels. Dual polarization is a promising approach to achieve uncorrelated signals. However, the gain reduction arising from mutual coupling between radiating elements still impairs the successful utilization of polarization diversity within a compact MIMO system. This thesis examines the performance of dense antenna arrays in MIMO systems. An N-element antenna array is regarded as an N-port network with non-vanishing off-diagonal elements in the network parameter matrices, for example the scattering parameter matrix. A modal expansion is then used to express the matrix in terms of mutually orthogonal eigenmodes. To facilitate the simultaneous removal of signal ii correlation and gain reduction due to the cross-talk, an approach, which employs an RF decoupling network at the array ports, is proposed. To verify the theory, a practical design of a novel, compact, four-port, dual-polarized aperture-coupled patch array with decoupling network is presented and tested. This antenna would be attractive for WLAN applications with limited antenna platforms. iii Table of Contents Acknowledgements i Summary . ii List of Figures viii List of Tables xi Chapter Introduction .1 1.1. Future Generation Wireless Communication .1 1.2. Contributions of this Thesis .4 1.3. Thesis Outline Chapter Antenna Fundamentals 10 2.1. Introduction 10 2.2. Radiation Quality and Bandwidth 11 2.2.1. Historical Background .11 2.2.2. Radiation Q . 13 2.2.3. Antenna Size and Radiation Q . 16 2.3. Superdirective Antenna Arrays 18 2.3.1. Overview of Superdirective Arrays 18 2.3.2. Superdirective Multi-Port Antennas of Low Order 20 2.4. Summary 23 Chapter Aperture-Coupled Antennas 25 3.1. Introduction 25 iv 3.2. Aperture-Coupled Antenna Fundamentals .26 3.2.1. Features and Developments 26 3.2.1.1. Wideband Aperture-Coupled Patch Antennas .27 3.2.1.2. Dual/Circular Polarization .28 3.2.1.3. Aperture-Coupled Patch Antenna Arrays 29 3.2.1.4. Monolithic Arrays 30 3.2.2. Analytical Methods 30 3.2.2.1. Modeling Methods 30 3.2.2.2. CAD .31 3.2.3. Basic Operation 32 3.2.4. Design Variations 37 3.3. Antenna Design 39 3.3.1. Single Aperture-Coupled Ring Patch Design . 40 3.3.2. Four-Element Aperture-Coupled Ring Patch Array . 47 3.4. Summary 51 Chapter Dense Multi-Port Antennas .52 4.1. Introduction 52 4.2. General Model for Dense Arrays .53 4.3. Modal Representation 57 4.4. Properties of Dense Multi-Port Antennas 58 4.4.1. Pattern Correlation and Gain Reduction . 58 4.4.2. Antenna Properties by means of Eigenmode Models . 60 v 4.4.2.1. Pattern Correlation and Gain Reduction 61 4.4.2.2. Superdirectivity .64 4.5. DBF in Dense Multi-Port Antennas .66 4.6. DN for Dense Multi-Port Antennas .68 4.7. Dissipative Losses in Dense Multi-Port Arrays .72 4.8. Summary 73 Chapter DN Realization 75 5.1. Introduction 75 5.2. DN Design .76 5.2.1. Topology . 78 5.2.2. Realization 80 5.2.2.1. Lemma .80 5.2.2.2. Four Port DN Design .82 5.3. Network Synthesis .94 5.3.1. Network Realization: Bp1 94 5.3.2. Network Realization: B0 96 5.3.3. Network Realization: Bp2 97 5.4. Results and Discussions .98 5.4.1. Numerical Results 98 5.4.1.1. Port and Modal Scattering Parameters 98 5.4.1.2. Port Radiation Patterns 100 5.4.2. Measured Results . 103 vi Chapter Conclusions 6.1.Conclusions In this thesis, dense antenna arrays were studied. We regard dense antenna array as multi-port antenna. Due to the strong mutual coupling between the array elements, it is not appropriate to consider the array as independent individual radiating elements. Hence, in this thesis, we use an N-port network to model the array. A modal representation was used to represent the array in terms of N mutual orthogonal modes. The corresponding modal patterns and modal radiation quality factors were also defined in order to study the performance of such an array. Reduced element spacing of compact arrays causes the port patterns to become strongly correlated. Moreover, due to the cross-talk, antenna gain is also reduced. As a consequence of mutual coupling, the port patterns become a function of the load admittance. While it is widely believed that the application of weighted digital coefficients is able to compensate for the mutual coupling, it was shown that this Chapter 6. Conclusions 111 measure is unable to overcome the problem of gain reduction. Here, a feeding network approach, the so-called decoupling network (DN), is presented. The DN is a feeding/decoupling network introduced between feeding points of the elements and the ports. It produces decoupled ports associated with mutually orthogonal port patterns without gain reduction. Moreover, dual polarization provides an opportunity to further utilize antenna diversity within a compact volume. Thus, a four-element aperture-coupled ring patch array with dual polarization was designed and fabricated. The DN was mounted onto the feed circuit to remove pattern correlation and gain reduction, thus allowing for a more compact array. This practical example shows that this DN approach is well suited to be applied to mobiles with antenna diversity and MIMO capabilities. 6.2.Future Research MIMO systems have traditionally been regarded as being the domain intended for DSP experts rather than RF engineers. However, if one wants to explore the possibility of system integration, the RF engineers have a role to play. To realize a MIMO system on an electrically small platform, there are at least three aspects of future research can be explored in terms of RF technology. 1. Antenna Design/Optimization for MIMO In this thesis, we tune the feed line to omit one element. Actually, some Chapter 6. Conclusions 112 modification on the antenna design may also achieve this. Future research may consider ways of finding methods to co-design the antenna array and the DN, so that more criteria can be involved into the optimization, e.g., the front-to-back ratio. The basic idea is to find a return path for the power coupled to other ports. 2. Wideband Decoupling At this stage, we synthesize the DN at the centre frequency. One possibility to improve the system performance is to synthesize it over a wider frequency range. This would require a curve-fitting approach, or otherwise, an equivalent circuit may be found for the dense array. 3. Circuit/Algorithm Modification One hint we get from the modal representation is that if we rather excite the modes instead of the ports, we can circumvent the problem of mutual coupling, because these modes are mutually orthogonal. Hence, current algorithms to tune the digital coefficients at different ports can be modified. Another possibility is to realize it in hardware. That is, instead of modifying the algorithm, we change the feeding network, so that, the coefficients function effectively on the modes. There is much deeper future research and studies can be carried out within this Chapter 6. Conclusions 113 field. A more compact antenna array with even higher mutual coupling is a possibility based on these results. REFERENCES [1] P. Lehne and M. Petterson. “An Overview of Smart Antenna Technology for Mobile Communications Systems”, IEEE Communications Surveys, Vol. 2, No. 4, pp.2-13, 1999 [2] A. Boukalov and S. Haggman, “System Aspects of Smart-Antenna Technology in Cellular Wireless Communications -an Overview”, IEEE Transactions on Microwave Theory and Techniques, Vol. 48, No. 6, pp.919-929, 2000 [3] G.J. Foschini, “Layered Space-Time Architecture for Wireless Communication in a Fading Environment When Using Multi-element Antennas”, Bell Labs Technical Journal, pp.41-589, Autumn 1996 [4] L.C. Godara, “Application of Antenna Arrays to Mobile Communications, Part I: Performance Improvement, Feasibility and System Considerations”, Proc. IEEE, Vol. 85, No. 7, pp.1031-1060, 1997 [5] L.C. Godara, “Application of Antenna Arrays to Mobile Communications, Part II: Beam-Forming and Direction-of-Arrival Considerations”, Proc. IEEE, Vol. 85, No. 8, pp.1195-1245, 1997 [6] R.A. Monzingo and T.W. Miller, Introduction to Adaptive Arrays, John Wiley & Sons, New York, 1980 [7] S. Verdú, Multiuser Detection, Cambridge University Press, Cambridge, UK, 1998 [8] J. Zhang, “Design and Performance Analysis of Power-Controlled CDMA Wireless Networks with Linear Receivers and Antenna Arrays”, PhD thesis, Purdue University [9] C. Berrou, A. Glavieux, and P. Thitimajshima, “Near Shannon Limit Error-Correcting Coding and Decoding: Turbo Codes”, Proceedings of 1993 IEEE International Conference on Communications, Geneva, Switzerland, May 1993 References 115 [10] R. Yates, “A Framework for Uplink Power Control in Cellular Radio Systems”, IEEE Journal on Selected Areas in Communication, Vol. 43, No. 7, pp.1341-1347, 1995 [11] A. Viterbi, CDMA: Principles of Spread Spectrum Communication, Addison-Wesley, 1995 [12] J. Zander, “Performance of Optimum Transmitter Power Control in Cellular Radio Systems”, IEEE Transactions on Vehicular Technology, Vol. 41, No. 1, pp.51-62, February 1992 [13] J. Zander, “Trends in Resource Management Future Wireless Networks”, Future Telecommunications Forum (FTF 99), Beijing, China, December 1999 [14] F. Berggren, S. Kim, R. Jantti and J. Zander, “Joint Power Control and Intracell Scheduling of DS-CDMA Nonreal Time Data”, IEEE Journal on Selected Areas in Communications, Vol. 19, No. 10, pp.1860-1870, October 2001 [15] M. Xiao, N. Shroff, and E. Chong, “Utility-Based Power control in Cellular Wireless Systems”, Proceedings of IEEE INFOCOM 2001, Vol. 1, 2001 [16] I. Katzela and M. Naghshineh, “Channel Assignment Schemes for Cellular Mobile Telecommunication Systems: A Comprehensive Survey”, IEEE Personal Communications Magazine, Vol. 3, No. 3, pp.10-31, June 1996 [17] D.A. Levine, I.F. Akyildiz and M. Naghshineh, “A Resource Estimation and Call Admission Algorithms for Wireless Multimedia Networks Using the Shadow Cluster Concept”, IEEE/ACM Transactions on Networking, Vol. 5, No.1, pp.1-13, February 1997 [18] T. Ojanperä and R. Prasad, Wideband CDMA for Third Generation Mobile Communications, Artech House, 1998 [19] L. Cimini, J. Chuang and N. Sollenberger, “Advanced Cellular Internet Service (ACIS)”, IEEE Communications Magazine, Vol. 36, No. 10, pp.150-159, October, 1998 References 116 [20] B. Wu and Q. Wang, “Maximization of the Channel Utilization in Wireless Heterogeneous Multiaccess Networks”, IEEE Transactions on Vehicular Technology, Vol. 46, No. 2, pp.437-444, 1997 [21] J. Chuang and N. Sollenberger, “Beyond 3G: Wideband Wireless Data Access Based on OFDM and Dynamic Packet Assignment”, IEEE Communications Magazine, Vol. 38, No. 7, pp.78-87, July 2000 [22] H. Rohling, T. May, K. Bruninghaus and R. Grunheid, “Broad-band OFDM Radio Transmission for Multimedia Applications”, Proc. IEEE, Vol. 87, No. 10, pp.1778-1789, 1999 [23] A. Paulraj and C.B. Papadias, “Space-Time Processing for Wireless Communications”, IEEE Signal Proc. Magazine, Vol. 14, pp.49-83, November 1997 [24] J.H. Winters, “On the Capacity of Radio communication Systems with Diversity in Rayleigh Fading Environments”, IEEE Journal on Selected Areas in Communication, Vol. 5, pp.871-878, June 1987 [25] I.E. Telatar, “Capacity of Multi-antenna Gaussian Channels”, European Transaction On Telecommunications, Vol. 10, pp.585-595, November/December 1999 [26] G.J. Foschini and M.J. Gans, “On Limits of Wireless Communications in a Fading Environment When Using Multiple Antennas”, Wireless Personal Communications, Vol. 6, pp.311-335, March 1998 [27] V. Tarokh, A. Naguib, N. Seshadri and A.R. Calderbank, “Space-time Codes for High Data Rate Wireless Communications: Performance Criteria in the Presence of Channel Estimation Errors, Mobility and Multiple Paths”, IEEE Transactions on Communications, Vol. 47, pp.199-207, 1998 References 117 [28] V. Tarokh, N. Seshadri and A.R. Calderbank, “Space-time Codes for High Data Rate Wireless Communications: Performance Criterion and Code Construction”, IEEE Transactions on Information Theory, Vol. 44, pp.744-765, 1998 [29] H. Bölcskei, A.J. Paulraj, K.V.S. Hari, R.U. Nabar and W.W. Lu, “Fixed Broadband Wireless Access: State of the Art, Challenges, and Future Directions”, IEEE Communications Magazine, pp.100-108, 2001 [30] S. Alamouti, “A Simple Transmitter Diversity Scheme for Wireless Communications”, IEEE Journal on Selected Areas in Communications, pp.1451-1458, October 1998 [31] 3GPP (3rd Generation Partnership Project), UMTS Radio Interface, March 2000 [32] D.J.V. Wyk, I.J. Oppermann and L.P. Linde, “Low Rate Coding Considerations for Space-time Coded DS/CDMA”, Proceeding Vehicular Technology Conference, 1999 Fall, Amsterdam, pp.2520-2524, IEEE 1999 [33] V. Tarokh, H. Jafarkhani and A.R. Calderbank, “Space-time Block Code from Orthogonal Designs”, IEEE Transactions on Information Theory, Vol. 45, pp.1456-1467, July 1999 [34] Y. Li, N. Seshadri and A. Ariyavisitakul, “Channel Estimation for OFDM Systems with Transmitter Diversity in Mobile Wireless Channels”, IEEE Journal on Selected Areas in Communications, Vol. 17, pp.461-471, 1999 [35] R.G. Vaughan and J.B. Andersen, “Antenna Diversity in Mobile Communications”, IEEE Transactions on Vehicular Technology, Vol. 36, pp.149-172, November 1987 [36] R.G. Vaughan and N.L. Scott, “Closely Spaced Monopoles for Mobile Communications”, Radio Science, Vol. 28, pp.1259-1266, Nov./Dec. 1993 [37] T. Swanteson and A. Ranheim, “Mutual Coupling Effects on the Capacity of Multielement Antenna Systems”, Proc. ICASSP, Salt Lake City, USA, References 118 pp.2485-2488, 2001 [38] V. Jungnickel, V. Pohl and C. Von Helmolt, “Capacity of MIMO Systems with Closely Spaced Antennas”, IEEE Communications Letters, Vol. 7, pp.361-363, August 2003 [39] C. Waldschmidt, J.V. Hagen and W. Wiesbeck, “Influence and Modeling of Mutual Coupling in MIMO and Diversity Systems“, IEEE International Symposium on Antennas and Propagation AP-S, San Antonio, Texas, Vol. 3, pp.190-193, 2002 [40] T. Svantesson, “Mutual Coupling Effects on the Capacity of Multielement Antenna Systems”, IEEE Proceedings of Acoustics, Speech and Signal Processing Conference, Vol. 2, pp.2485-2488, 2001 [41] H.A. Wheeler, “Small Antennas”, IEEE Transactions on Antennas and Propagation, Vol. AP-23, No. 4, pp.462-469, July 1975 [42] H.A. Wheeler, “Fundamental Limitations of Small Antennas”, Proc. IRE, Vol. 35, pp.1479-1484, December 1947 [43] L.J. Chu, “Physical Limitations on Omni-Directional Antennas”, Journal of Applied Physics, Vol. 19, pp.1163-1175, December 1948 [44] R.F. Harrington, “Effect of Antenna Size on Gain, Bandwidth and Efficiency”, J. Res. Nat. Bur. Stand., Vol. 64D, pp.1-12, Jan.-Feb. 1960 [45] R.C. Hansen, “Fundamental Limitation in Antennas”, Proc. of IEEE, Vol. 69, No. 2, pp.170-182, February 1981 [46] R.M. Fano, “Theoretical Limitations on the Broadband Matching of Arbitrary Impedances”, Journal of the Franklin Institute, January 1950 [47] Guillermo Gonzales, Microwave Transistor Amplifiers, Analysis and Design, Prentice-Hall, Inc., Englewood Cliffs, N.J., 1984, pp.167-168 References 119 [48] R.E. Collin, Foundations for Microwave Engineering, Second Ed., McGraw-Hill, Inc., 1992, pp.325-326 [49] R.E. Collin and S.Rothschile, “Evaluation of antenna Q”, IEEE Transactions on Antennas and Propagation, Vol. AP-12, pp.23-27, January 1964 [50] R.L. Fante, “Quality Factor of General Ideal Antennas”, IEEE Transactions on Antennas and Propagation, Vol. AP-17, pp.151-155, March 1969 [51] C.A. Balanis, Antenna Theory, Analysis, and Design, New York: Wiley, 1982, pp.439-444 [52] P.K. Park and C.T. Tai, “Receiving Antennas”, in Antenna Handbook: Theory, Applications, and Design, Y.T. Lo and S.W. Lee, Ed. New York: Van Nostrand Reinhold, 1998, pp.6.22-6.24 [53] D.M. Grimes, C.A. Grimes, “The Complex Poynting Theorem: Reactive Power, Radiative Q and Limitations on Electrically Small Antennas”, Electromagnetic Compatibility, 1995. Symposium record. 1995 IEEE International Symposium on, 14-18 August 1995, pp.97-101 [54] C.A. Grimes, “Efficient Radiation From an Electrically Small Antenna: Control of Higher Order Modes”, Aerospace Applications Conference, 1996. Proceedings, 1996 IEEE, 3-10 February 1996, Vol. 4, pp.147-160 [55] C.A. Grimes, J.L. Horn, F. Tefiku, R. Shahidain and D.M. Grimes, “An Experimental Investigation into the Control of Antenna Input Impedance Through Cancellation of Near Field Standing Energy”, Aerospace Conference, 1998. Proceedings., IEEE, 21-28 March 1998, Vol. 3, pp.273-282 [56] G. Goubau, “Multi-element Monopole Antennas”, in Proc. Workshop on Electrically Small Antennas, ECOM, Ft. Monmouth, N.J., pp.63-67, May 1976 References 120 [57] P.H. Smith, “Cloverleaf Antenna for F.M. Broadcasting”, Proc. of the IRE, Vol. 12, pp.1556-1563, December 1947 [58] H.J. Chaloupka, “HTS Antennas”, in H. Weinstock and M. Nisenoff (eds.), Microwave Superconductivity, Dordrecht: Kluwer 2001 [59] H.J. Chaloupka, X. Wang and J.C. Coetzee, “Superdirective 3-Element Array For Adaptive Beamforming”, Microwave and Optical Technology Letters, Vol. 36, No. 6, pp.425-430, March 2003 [60] H.J. Chaloupka, X. Wang and J.C. Coetzee, “Performance Enhancement of Smart Antennas with Reduced Element Spacing”, Wireless Communications and Network, 2003. WCNC 2003, 16-20 March 2003, Vol. 1, pp.425-430 [61] H.J. Chaloupka, X. Wang, “On the Properties of Small Arrays with Closely Space Antenna Elements”, to be published in Proc. IEEE Antennas Propagation Society International Symposium, APS 2004 [62] H.J. Chaloupka, X. Wang and J.C Coetzee, “Compact Arrays for Mobile Platforms: Trade-off Between Size and Performance for SDMA and MIMO Applications”, 48 Internationales Wissenschaftliches Kolloquium, Technische Universität Ilmenau, 22-25 September 2003 [63] H.J. Chaloupka, “On the Frequency Bandwidth of Functionally Small Antennas”, Proc. URSI International Symposium Electron Theory (Sydney 1992), pp.266-268 [64] H.J. Chaloupka, “High Temperature Superconductor Antennas: Utilization of Low RF Losses and of Nonlinear Effects”, Journals on Superconductivity 5, pp.403-416 [65] G. Broussaud and Spitz, “Superdirective Supergain”, Ann. Radioelect., Vol. 15, pp.289-304, 1960 References 121 [66] A. Bloch, R.G. Medhurst, S.D. Pool and W.E. Knock, “Superdirectivity”, Proc. IEE, Vol. 48, pp.1164, 1960 [67] M.M. Dawoud and A.P. Anderson, “Superdirectivity with Appreciable Bandwidth in Arrays of Radiating Elements Fed by Microwave Transistors”, Conf. Proc. 4th European Microwave Conf., Switzerland, pp.278-282, September 1974 [68] A.P. Anderson, M.M. Dawoud, J.C. Bennet, and P.D. Patel, “Search Procedure for Efficient Superdirective Array and Image Enhancement Functions”, Electron. Letter, Vol. 13, No. 2, pp.43-44, January 20, 1977 [69] M.M. Dawoud and A.P. Anderson, “Design of Superdirective Arrays with High Radiation Efficiency”, IEEE Transactions on Antennas and Propagation, Vol. AP-26, No. 6, pp.819-823, November 1978 [70] M.M. Dawoud and A.P. Anderson, “Design of Endfire Antenna Arrays for Beam Narrowing and Low Side Lobe Levels”, Proc. Third IEE Int. Conf. on Antennas and Propagation, Norwitch, U.K., pp.61-64, April 1983 [71] D.C. Skigin, V.V. Veremey and R. Mittra, “Superdirective Radiation from Finite Gratings of Rectangular Grooves”, IEEE Transactions on Antennas and Propagation, Vol. 47, No. 2, February 1999 [72] O. Ishii, K. Itoh, Y. Nagai and K. Kagoshima, “Miniaturization of Array Antennas with Superdirective Excitation”, Digest of Antennas and Propagation Society International Symposium, AP-S 1993, Vol. 3, pp.1850-1853, 28 June- July 1993 [73] I.J. Gupta and A.A. Ksienski, “Effect of Mutual Coupling on the Performance of Adaptive Arrays”, IEEE Transactions on Antennas and Propagation, Vol. AP-31, No. 5, pp.785-791, September 1983 [74] D.M. Pozar, “A Microstrip Antenna Aperture-Coupled to a Microstrip Line”, Electronics Letters, Vol. 21, pp.49-50, January 17, 1985 References 122 [75] D.M. Pozar, “Microstrip Antennas”, IEEE Proc., Vol. 80, pp.79-91, January 1992 [76] D.H. Schaubert, “Microstrip Antennas”, Electromagnetics, Vol. 12, pp.381-401, 1992 [77] J.P. Daniel, G. Dubost, C. Terret, J. Citerne and M. Drissi, “Research on Planar Antennas and Arrays: Structures Rayonnates”, IEEE Antennas and Propagation Magazine, Vol. 35, No. 1, pp.14-38, February 1993 [78] D.M. Pozar and D.H. Schaubert, Microstrip Antennas: The analysis and design of microstrip antennas and arrays, IEEE Press, New York, 1995 [79] D.M. Pozar, “A Review of Aperture-Coupled Microstrip Antennas: History, Operation, Development, and Applications”, www.ecs.umass.edu/ece/pozar/ pozarhome.htm, May 1996 [80] J.F. Zurcher, “The SSFIP: A Global Concept for High Performance Broadband Planar Antennas”, Electronics Letters, Vol. 24, pp.1433-1435, November 1988 [81] F. Croq and A. Papiernik, “Large Bandwidth Aperture-Coupled Microstrip Antenna”, Electronics Letters, Vol. 26, pp.1293-1294, August 1990 [82] S. Targonski and D.M. Pozar, “Design of Wideband Circularly Polarized Aperture-Coupled Microstrip Antennas”, IEEE Transactions on Antennas and Propagation, Vol. 41, pp.214-220, February 1993 [83] F. Croq and A. Papiernik, “Stacked Slot-coupled Printed Antenna”, IEEE Microwave and Guided Wave Letters, Vol. 1, pp.288-290, October 1991 [84] F. Croq and D.M. Pozar, “Millimeter Wave Design of Wide-Band Aperture-Coupled Stacked Microstrip Antennas”, IEEE Transactions on Antennas and Propagation, Vol. 39, pp.1770-1776, December 1991 References 123 [85] M. Edimo, P. Rigoland and C. Terret, “Wideband Dual Polarized Aperture-Coupled Stacked Patch Antenna Array Operating in C-Band”, Electronics Letters, Vol. 30, pp.1196-1197, July 1994 [86] S.D. Targonski and R.B. Water house, “An Aperture-Coupled Stacked Patch Antenna with 50% Bandwidth”, IEEE International Symposium on Antennas and Propagation, Baltimore, MD. 1996 [87] A. Adrian and D.H. Schaubert, “Dual Aperture-Coupled Microstrip Antenna for Dual of Circular Polarization”, Electronics Letters, Vol. 23, pp.1226-1228, November 1987 [88] C.H. Tsao, Y.M. Hwang, F. Killburg and F. Dietrich, “Aperture-Coupled Patch Antennas with Wide Bandwidth and Dual Polarization Capabilities”, IEEE Antennas and Propagation Symposium Digest, pp.936-939, 1988 [89] M. Edimo, A. Sharaiha and C. Terret, “Optimized Feeding of Dual-Polarized Broadband Aperture-Coupled Printed Antenna”, Electronics Letters, Vol. 28, pp.1785-1787, September 1992 [90] M.I. Aksun, S.L. Chuang and Y.T. Lo, “Theory and Experiment of Electromagnetically Excited Microstrip Antennas for Circular Polarization Operation”, IEEE Symposium on Antennas and Propagation Digest, pp.1142-1145, San Jose, 1989 [91] T. Vlasits, E. Korolkiewicz, A. Sambell and B. Robinson, “Performance of a Cross-Aperture-Coupled Single Feed Circularly Polarized Patch Antenna”, Electronics Letters, Vol. 23, pp.612-613, March 1996 [92] C. Wu, J. Wang, R. Fralich, and J. Litva, “Analysis of a Series-Fed Aperture-Coupled Patch Array Antenna”, Microwave and Optical Technology Letters, Vol. 4, pp.110-113, February 1991 [93] H. Ohmine, T. Kashiwa, T. Ishikawa, A. Iida and M. Matsunaga, “An MMIC References 124 Aperture-Coupled Microstrip Antenna in the 40GHz Band”, Proc. ISAP, pp.1105-1108, September 1992, Japan [94] S. Sanzgiri, W. Pottenger, D. Bostrom, D. Denniston and R. Lee, “Active Subarray Module Development for Ka Band Satellite Communication Systems”, IEEE Symposium on Antennas and Propagation Digest, pp.860-863, June 1994 [95] P.L. Sullivan and D.H. Schaubert, “Analysis of an Aperture-Coupled Microstrip Antenna”, IEEE Transactions on Antennas and Propagation, Vol. AP-34, pp.977-984, August 1986 [96] D.M. Pozar, “A Reciprocity Method of Analysis for Printed Slot and Slot Coupled Microstrip Antennas”, IEEE Transactions on Antennas and Propagation, Vol. AP-34, pp.1439-1446, December 1986 [97] S.G. Pan and I. Wolff, “ Computation of Mutual Coupling Between Slot-Coupled Microstrip Patches in a Finite Array”, IEEE Transactions on Antennas and Propagation, Vol. 40, pp.1047-1053, September 1992 [98] D.M. Pozar, “Analysis of an Infinite Array of Aperture-Coupled Microstrip Patches”, IEEE Transactions on Antennas and Propagation, Vol. AP-37, pp.418-425, April 1989 [99] M. Himdi, J.P. Daniel and C. Terret, “Analysis of Aperture-Coupled Microstrip Antenna Using Cavity Method”, Electronics Letters, Vol. 25, pp.391-392, March 1989 [100] M. E. Yazidi, M. Himdi, and J.P. Daniel, “Transmission Line Analysis of Non-Linear Analysis of Slot Coupled Microstrip Antenna”, Electronics Letters, Vol. 28, pp.1406-1407, July 1992 [101] P. Darwood, P.N. Fletcher and G.S. Hilton, “Mutual Coupling Compensation in Small Planar Array Antennas”, IEE Proc. Microwaves, Antennas Propagation, Vol. 145, pp.1-6, 1998 References 125 [102] H. Steyskal and J.S. Herd, “Mutual Coupling Compensation in Small Array Antennas”, IEEE Transactions on Antennas Propagation, Vol. 38, pp.1971-1975, 1990 [103] R.S. Adve and T.K. Sarkar, “Compensation for the Effects of Mutual Coupling on the Direct Data Domain Adaptive Algorithms”, IEEE Transactions on Antennas Propagation, Vol. 48, pp.86-94, 2000 [104] B. Friedlander and A.J. Weiss, “Direction Finding in the Presence of Mutual Coupling”, IEEE Transactions on Antennas Propagation, Vol. 39, pp.273-284, 1991 [105] R.C. Hansen, Phased Array Antennas, New York: Wiley, 1998 [106] E. Hammerstad, and F. Bekkadal, A Microstrip Handbook, ELAB Report, STF 44 A74169, University of Trondheim, Norway, 1975 [107] D.M. Pozar, Microwave Engineering, 2nd Ed., John Wiley & Sons Inc., 1998 [108] Y.H. Lu, H.J. Chaloupka, and J.C. Coetzee, “Compact Dual-polarized 4-port Microstrip Antenna with Decoupling-Network”, IEEE International Symposium on Antennas and Propagation And USNC/URSI National Radio Science Meeting, Monterey, CA, 2004 [109] H.J. Chaloupka, Y.H. Lu and J.C. Coetzee, “A Dual Polarized Microstrip Antenna Array with Port Decoupling for MIMO System”, International Symposium on Antennas and Propagation, Aug. 17-21, 2004, Sendai, Japan [...]... radiation quality (radiation Q) value and hence gives an approximate indication of the maximum operational bandwidth of a lossless antenna, which fits inside a sphere of a given radius Collin [49] and Fante [50] published an exact theory based on a calculation of the evanescent energy stored around an antenna The approximate fundamental lower limit given by Chapter 2 Antenna Fundamentals Chu and Harrington’s... estimation for the achievable fractional bandwidth of power matching as a function of Qrad and the in-band reflection 2.2.3 Antenna Size and Radiation Q To discuss the relationship between antenna dimension and radiation quality, the radiation of an antenna is represented as a sum of spherical wave functions with main modal numbers µ In the transmit mode, if a time harmonic wave is incident at the antenna... uncorrelated signals, and therefore, require a smaller space, compared with traditionally used space diversity However, in a dense array, the gain reduction arising from mutual coupling between radiating elements still impairs the successful utilization of polarization diversity within a compact MIMO system After studying the characteristics of dense arrays, we will present a novel approach which employs an RF... parameters in Chapter 2 and the modal model in Chapter 4 to evaluate the whole system; that is, the compact antenna array with the feed network It is shown that, with a DN, a compact array without port 8 Chapter 1 Introduction gain reduction and pattern correlation is realized Finally, we conclude with a summary and an outlook on future research in Chapter 6 9 Chapter 2 Antenna Fundamentals 2.1.Introduction... work on characteristics of dense arrays is 7 Chapter 1 Introduction followed by a modal model from Chaloupka [59-62] The eigenmodes of the array are defined and associated modal impedances and modal radiation patterns are given A further discussion on these properties in Chapter 4 will give us more insight on the array system design Chapter 4 will also address the properties of radiation patterns in... radiation power factor as the ratio of resistance to reactance in the series equivalent circuit or the ratio of conductance to susceptance in the parallel equivalent circuit Hence, the fractional bandwidth of the equivalent circuit of the antenna, combined with an appropriate lossless matching network to form a resonant series or Chapter 2 Antenna Fundamentals 12 parallel RLC network, is approximately... properties and limits of dense arrays We use the concept of “multi-port antenna” throughout this thesis, because considering antenna elements as independent ones is no longer justified in such a dense array Instead, a systematic approach, which treats the whole array as one antenna with 5 Chapter 1 Introduction mutually coupled ports, is more suitable Two important figures of merit for multi-port antennas are... [46, 47] To understand the fundamental relationship between antenna size and bandwidth, the quantity “radiation power factor” was used by Wheeler [42] He approximated electrically-small antennas as either a lumped inductance in series with a frequency-dependent radiation resistance (magnetic dipoles) or a lumped capacitance in parallel with a frequency-dependent radiation conductance (electric dipoles)... disturbances based on their angular distribution of incidence This approach is known as “adaptive nulling” For adaptive forming of the radiation pattern, an array is needed which provides multiple (M) output ports with different linearly-independent radiation patterns The output signals from these ports can be subjected to various forms of analog and digital signal processing In particular, by means of a. .. books, and is therefore beyond the scope of this thesis However, this chapter addresses some fundamentals and definitions, which are of particular relevance to antennas and shed light on how antennas resonate and radiate in a highly packed environment The focus is on the radiation quality, impedance bandwidth and the superdirectivity, because these parameters determine the RF performance of a MIMO system . A DUAL-POLARIZED DENSE ARRAY FOR MIMO SYSTEM APPLICATIONS LU YIHAO NATIONAL UNIVERSITY OF SINGAPORE 2004 A DUAL-POLARIZED DENSE ARRAY FOR MIMO SYSTEM APPLICATIONS LU YIHAO (B.ENG , SHANGHAI. thesis examines the performance of dense antenna arrays in MIMO systems. An N-element antenna array is regarded as an N-port network with non-vanishing off-diagonal elements in the network parameter. My Parents, Lu Xiao-Di and Zhu Yu-Ya Name: Lu Yihao Degree: M.Eng. Dept: Electrical and Computer Engineering Thesis Title: A Dual-Polarized Dense Array for MIMO System Applications Abstract This