近年來，快迅發展的無線通訊系統滿足了個人通訊之需求。對於現今無線通訊元件的訴求是：價格低廉、小型化及多功能化。關於元件小型化而言，高介質陶瓷材料的使用，能有效縮小微波元件的尺寸。
本論文包括兩大部份：微波介電材料的研究和微帶陶瓷天線的製作。論文的第一部份，完整地探討BiNbO4系列材料[包括(Bi1-xSmx) NbO4]，和Al2O3-TiO2陶瓷材料之微結構與微波介電特性。BiNbO4陶瓷材料，能夠藉由CuO或V2O5燒結促進劑的添加，在低於940℃的溫度下進行有效的燒結。實驗結果顯示，過量的燒結促進劑或過高的燒結溫度，會造成微波介電特性的下降，其中包括品質因數(Q)和共振頻率溫度係數(τf)；從而得到燒結促進劑的最佳含量為0.5 wt%。針對BiNbO4陶瓷而言，因為CuO的添加會使BiNbO4陶瓷呈負溫度係數，而V2O5的添加會使BiNbO4陶瓷呈正溫度係數。所以BiNbO4陶瓷可藉由CuO和V2O5的同時添加，且控制CuO/V2O5重量比使其τf值達到0 ppm/℃。另外，我們也研究利用Sm元素來取代Bi元素，而使τf值趨近0 ppm/℃的目的。在(BixSm1-x)NbO4材料的燒結過程中，斜方體的α相會轉變為三斜體的β相，這個β相的出現對於材料晶粒成長、密度、Q×f值及τf值有很大的影響，但對εr值的影響卻不大。綜合而論，在BiNbO4系列的研究中，可獲得高介質、高品質因數和溫度穩定的微波介電陶瓷材料。
關於(1-x)Al2O3-xTiO2材料，藉由MCAS玻璃的添加，可將燒結溫度由1500℃降到1300℃。另外，控制組成中TiO2含量和燒結溫度，可使材料的τf值趨近於0 ppm/℃。在燒結過程中，Al2TiO5晶相的產生將伴隨TiO2含量的減少，導致對材料微波介電特性有深遠的影響。就此研究而言，燒結溫度的下降及τf值的改善是主要進展。研究顯示，當2 wt%的MCAS玻璃加入於x = 0.12的組成中，且燒結溫度在1300℃時，有最小的τf值，其值為-0.6 ppm/℃。
論文第二部份則以BiNbO4微波介電陶瓷為基板，進行微帶天線的研製。雖然元件尺寸被縮小，但過窄的頻寬卻無法適用於WLAN系統。於是我們利用二種方法來擴展頻寬，第一種方法是在幅射金屬層上挖一對U型的槽孔，可將原本 2.3%的頻寬改善至5.3%。第二種方法是利用堆疊結構，可將頻寬改善至4.5%。這兩種方法都是藉由結合鄰近兩個共振模態，來達成頻寬擴展的目的。

Recently, the evolutions of wireless communication systems are growing rapidly to satisfy the personal communication requirements. Compact, small size, low cost, and multi-function are the major developing trends among these modern wireless communication devices. The use of ceramic materials with high permittivity can effectively reduce the sizes of microwave devices.
This thesis consists of two parts: the research of microwave dielectric materials and the implementation of microstrip ceramic antennas. In the first part of the dissertation, the systematic investigations of the microstructure and microwave dielectric properties in respect of BiNbO4-based ceramics and MCAS glass-added Al2O3-TiO2 ceramics have presented. By the addition of CuO, V2O5, or CuO-V2O5 mixture, the BiNbO4 ceramics can be densified at lower sintering temperatures less than 940℃. The excellent microwave dielectric properties are obtained as 0.5 wt% CuO or V2O5 are added as sintering aids. The exceeded additive amount or sintering temperatures will result in the appearance of abnormal grain growth and the increase of grain boundary inclusions, which will decrease the microwave dielectric properties including the quality factor (Q) and the temperature coefficient of resonant frequency (τf). The CuO-added BiNbO4 ceramics reveal a negative τf value and V2O5-added BiNbO4 ceramics reveal a positive one. The τf values can be reduced to near 0 ppm/℃ by controlling the weight ratio of CuO/V2O5. Another method to reduce the τf values to near 0 ppm/℃ is the substitution of Sm for Bi. For the (Bi1-xSmx)NbO4 ceramics, the presence of the β-form of (Bi1-xSmx)NbO4 ceramics will affect the grain growth, density, Q×f values and τf values, but that has no apparent effect on εr values. On the whole, a high permittivity, an acceptable quality factor, and the temperature stable BiNbO4-based ceramic can be obtained.
As for (1-x)Al2O3-xTiO2 ceramics, the addition of MCAS glass can lower the sintering temperatures of (1-x)Al2O3-xTiO2 ceramics from 1500℃ to 1300℃. And the τf value can be adjusted to near zero by controlling the TiO2 content and sintering temperature. The appearance of Al2TiO5 phase, resulted from the consumption of TiO2, exhibits intense effect on the microwave dielectric properties of (1-x)Al2O3 -xTiO2 ceramics. The major contributions in this research would be the lower sintering temperatures and the near 0 ppm/℃ of τf value. The 2wt%- MCAS-added (1-x)Al2O3-xTiO2 ceramics sintered at 1300℃ and x = 0.12 has a minimum τf value of –0.6 ppm/℃.
In the second part of the dissertation, the microstrip antennas with high permittivity BiNbO4 ceramics (εr = 43) substrate are fabricated. The bandwidths obtained are narrow and insufficient for the WLAN application. The techniques of U-slots patch and stacked structure are used to enhance the bandwidth of the microstrip ceramic antennas by combining the two adjacent resonant modes. The results indicate that the impedance bandwidth can be enhanced from 2.3% to 5.3% by embedding double U-shaped slots in the rectangular patch, or to 4.5% by using stacked patches.

Contents
Chapter 1 General Introduction…1
1-1 Introduction…1
1-2 Objectives and Thesis Organization…5
Chapter 2 Theory…7
2-1 Liquid Phase Sintering…7
2-2 Dielectric Properties of Materials…9
2-3 Electromagnetic Theory…12
2-4 Microstrip Transmission Lines…16
Chapter 3 Experimental Procedure…20
3-1 Specimens Preparation…20
3-1-1 Preparation of BiNbO4 and (Bi1-xSmx)NbO4 compositions…20
3-1-2 Preparation of (1-x)Al2O3-xTiO2 composition…20
3-2 Characteristics Analysis…21
3-3 Measurement of Microwave Dielectric Properties…21
3-3-1 Calculation of dielectric constant (εr)…22
3-3-2 Measurement of Q values…23
3-3-3 Measurement of τf values…24
Chapter 4 Results and Discussion…26
4-1 BiNbO4 Ceramics…26
4-1-1 Microstructure analysis…26
4-1-2 Microwave dielectric properties analysis…30
4-2 (Bi1-xSmx)NbO4 Ceramics…32
4-2-1 Microstructure analysis…32
4-2-2 Microwave dielectric properties analysis…35
4-3 (1-x)Al2O3-xTiO2 Ceramics…37
4-3-1 Microstructure analysis…37
4-3-2 Microwave dielectric properties analysis…40
4-4 Summary…43
Chapter 5 Microstrip Antenna Applications…46
5-1 Introduction…46
5-2 U-slot Patch Antenna…47
5-2-1 Antenna design…47
5-2-2 Results and discussion…48
5-3 Stacked Patch Antenna…50
5-3-1 Antenna design…50
5-3-2 Results and discussion…50
Chapter 6 Conclusion…52
References…56

References
[1] R. A. Sainati, “CAD of microstrip antenna for wireless applications", Artech House, Boston, 1996.
[2] I. J. Bahl and P. Bhartia, “Microstrip antennas”, Artech House, 1980.
[3] T. K. Lo, C. O. Ho, Y. Hwang, E. K. W. Lam and B. Lee, “Miniature aperture- coupled microstrip antenna of very high permittivity”, Electron. Lett., 1997, vol. 33, pp. 9-10.
[4] Y. Hwang, Y. P. Zhang, K. M. Luk and E. K. N. Yung, “Gain-enhanced miniaturized rectangular dielectric resonator antenna”, Electron. Lett., 1997, vol. 33, pp. 350-352.
[5] T. Ishizaki, M. Fujita, M. Fujita, H. Kagata and H. Miyake, “A very small dielectric planar filter for portable telephones”, IEEE Trans. on Micro.Theory Techno., 1994, vol. 42, pp. 2017-2021.
[6] T. Negas, G. Yeager, S. Bell and N. Coats, “BaTi4O9/Ba2Ti9O20-based ceramics resurrected for modern microwave applications”, Am. Ceram. Soc. Bull., 1993, vol. 72, pp. 80-89.
[7] R. Christoffersen, P. K. Davies and X. Wei, “Effect of Sn substitution on cation ordering in (Zr1-xSnx)TiO4 microwave dielectric ceramics”, J. Am. Ceram. Soc., 1994, vol. 77, pp. 1441-1450.
[8] S. Nomura, K. Toyama and K. Kaneta, “Ba(Mg1/3Ta2/3)O3 ceramics with temperature-stable high dielectric constant and low microwave loss”, Jpn. J. Appl. Phys., 1982, vol. 21, pp. 624-626.
[9] H. Ohsato, S. Nishigaki and T. Okuda, “Superlattice and dielectric properties of BaO-R2O3-TiO2 (R=La, Nd and Sm) microwave dielectric compounds”, Jpn. J. Appl. Phys., 1992, vol. 31, pp. 3136-3138.
[10] S. Katayama, I. Yoshinaga, N. Yamada and T. Nagai, “Low-temperature synthesis of Ba(Mg1/3Ta2/3)O3 ceramics from Ba-Mg-Ta alkoxide precursor”, J. Am. Ceram. Soc., 1996, vol. 79, pp. 2509-2564.
[11] T. Takada, S. F. Wang, S. Yoshikawa, S. J. Jang and R. E. Newnham, “Effect of glass additions on BaO-TiO2-WO3 microwave ceramics”, J. Am. Ceram. Soc., 1994, vol. 77, pp. 1909-1916.
[12] D. Liu, Y. Liu, S. Q. Huang and X. Yao, “Phase structure and dielectric properties of Bi2O3-ZnO-Nb2O5-based dielectric ceramics”, J. Am. Ceram. Soc., 1993, vol. 76, pp. 2129-2132.
[13] H. Kagata, T. Inoue, J. Kato and I. Kameyama, “Low-fire bismuth-based dielectric ceramics for microwave use”, Jpn. J. Appl. Phys., 1992, vol. 31, pp. 3152-3155.
[14] E. M. Levin, C. R. Robbins and H. F. McMurdie, “Phase diagrams for ceramists 1969”, The American Ceramic Society, Columbus, OH, 1969.
[15] W. Choi and K. Y. Kim, “Effects of Nd2O3 on the microwave dielectric properties of BiNbO4 ceramics”, J. Mater. Res., 1998, vol. 13, pp. 2945-2949.
[16] M. H. Weng and C. L. Huang, “The microwave dielectric properties and the microstructures of Bi(Nb,Ta)O4 ceramics”, Jpn. J. Appl. Phys., 1999, vol. 38, pp. 5949-5952.
[17] S. J. Peen, N. M. Alford, A. Templeton, X. Wang, M. Xu, M. Reece and K. Schrapel, “Effect of porosity and grain size on the microwave dielectric properties of sintered alumina”, J. Am. Ceram. Soc., 1997, vol. 80, pp. 1885-1888.
[18] G. Wolfram and H. G. Gobel, “Existence range, structural and dielectric properties of ZrxTiySnzO4 ceramics (x+y+z=2)”, Mat. Res. Bull., 1981, vol. 16, pp. 1455-1461.
[19] K. H. Yoon, D. P. Kim and E. S. Kim, “Effect of BaWO4 on the microwave dielectric properties of Ba(Mg1/3Ta2/3)O3 ceramics”, J. Am. Ceram. Soc., 1994, vol. 77, pp. 1062-1066.
[20] S. Kucheiko, J. W. Choi, H. J. Kim and H. J. Jung, “Microwave dielectric properties of CaTiO3-Ca(Al1/2Ta1/2)O3 ceramics”, J. Am. Ceram. Soc., 1996, vol. 79, pp. 2739-2743.
[21] A. Templeton, X. Wang, S. J. Peen, S. J. Webb, L. F. Cohen and N. M. Alford, “Microwave dielectric loss of titanium oxide”, J. Am. Ceram. Soc., 2000, vol. 83, pp. 95-100.
[22] H. M. O’Bryan, J. Thomson and J. K. Plourde, “A new BaO-TiO2 compound with temperature-stable high permittivity and low microwave loss”, J. Am. Ceram. Soc., 1974, vol. 57, pp. 450-453.
[23] H. M. O’Bryan, “Identification of surface phases on BaTiO3-TiO2 ceramics”, Am. Ceram. Soc. Bull., 1987, vol. 66, pp. 677-680.
[24] Z. Y. Xu and X. M. Chen, “Dielectric ceramics with TiO2 rich compositions in Bi2O3-TiO2 system”, Mater. Lett., 1999, vol. 39, pp. 18-21.
[25] J. W. Choi, S. J. Yoon, H. J. Kim and K. H. Yoon, “Microwave dielectric characteristics of (1-x)(Al1/2Ta1/2)O2-xTiO2 ceramics”, Jpn. J. Appl. Phys., 2002, vol. 41, pp. 3804-3807.
[26] A. I. Berezhnoi, “Properties of glass-ceramics”, Glass Ceram. and Photo-Sitalls, 1970, pp. 326-339.
[27] C. F. Yang, “The sintering characteristics of MgO-CaO-Al2O3-SiO2 composite powder made by Sol-Gel method”, Ceram. Int., 1998, vol. 24, pp. 243-247.
[28] C. M. Cheng, C. F. Yang and S. H. Lo, “The influence of crystallization on the flexural strength of MgO-CaO-Al2O3-SiO2 composite glass”, Ceram. Int., 1999, vol. 25, pp. 581-586.
[29] C. F. Yang and C. M. Cheng, “The influence of B2O3 on the sintering of MgO-CaO-Al2O3-SiO2 composite glass powder”, Ceram. Int., 1999, vol. 25, pp. 383-387.
[30] V. N. Eremenko, Y. V. Naidich, and I. A. Lavrinenko, “Liquid phase sintering”, Consultants Bureau, New York, NY, 1970.
[31] M. Chandler, “Ceramics in the modern world”, Doubleday, Garden City, NY, 1968.
[32] D. W. Budworth, “An introduction to ceramic science”, Pergamon Press, Oxford, UK, 1970.
[33] W. D. Kingery, H. K. Bowen, and D. R. Uhlmann, “Introduction to ceramics”, second edition, Wiley-Interscience, New York, NY, 1976.
[34] F. V. Lenel, “Sintering in the presence of a liquid phase”, Trans. AIME, 1948, vol. 175, pp. 878-896.
[35] H. S. Cannon, and F. V. Lenel, “Some observations on the mechanism of liquid phase sintering”, Plansee Proceeding, Reutte, Austria, 1953, pp. 106-121.
[36] W. D. Kingery, “Densification during sintering in the presence of a liquid phase. 1. Theory”, J. Appl. Phys., 1959, vol. 30, pp. 301-306.
[37] W. D. Callister, “Materials science and engineering an introduction”, 5th ed., John Wiley, New York, 2000, pp. 643.
[38] G. Burns, “Solid state physics”, John Wiley, 1985, pp. 461.
[39] W. S. Kim, T. H. Kim, E. S. Kim, and K. H. Yoon, “Microwave dielectric properties and far infrared reflectivity spectra of the (Zr0.8Sn0.2)TiO4 ceramics with additives”, Jpn. J. Appl. Phys., 1998, vol. 37, pp. 5367-5371.
[40] C. T. Johnk, “Engineering electromagnetic fields and waves”, John Wiley, New York, 1975.
[41] D. K. Cheng, “Field and wave electromagnetics”, 2nd edition, Addison-Wesley, Reading MA, 1996.
[42] D. Kajfez, “Basic principles give understanding of dielectric wave-guides and resonators”, Microwave Systems News, 1983, vol. 13, pp. 152-161.
[43] D. Kajfez, A. W. Glisson, and J. James, “Computed modal field distributions for isolated dielectric resonators”, IEEE Trans. On Microwave Theory and Techniques, 1984, vol. 32, pp. 1609-1616.
[44] G. A. Deschamps, “Microstrip microwave antennas”, 3rd USAF Symp. Antennas, University of Illinois, Urbana, IL, 1953.
[45] J. Q. Howell, “Microstrip antennas”, IEEE Int. Symp. Digest Antennas and Propagation, Williamsburg, VA, 1972, pp. 177-180.
[46] G. G. Sanford, “Conformal microstrip phased array for aircraft tests with ATS-6”, Proc. Nat. Electron. Conf., 1974, Vol. 29, pp. 252-257.
[47] R. E. Munson, “Conformal microstrip antennas and microstrip phased arrays”, IEEE Trans. On Antennas and Propagation, 1974, Vol. 22, pp. 74-77.
[48] D. D. Grieg and H. F. Englemann, “Microstrip-a new transmission technique for the kilomegacycle range”, Proc. IRE, 1952, Vol. 40, pp. 1644-1650.
[49] E. H. Fooks, and R. A. Zakarevicius, “Microwave engineering using microstrip circuits”, Prentice Hall, 1989, pp. 41-61.
[50] H. A. Wheeler, “Transmission-line properties of parallel strips separated by a dielectric sheet”, IEEE Trans., 1965, MTT-13, No. 3, pp. 172-185.
[51] R. P. Owens, “Accurate analytical determination of quasi-static microstrip line parameters”, The Radio and Electronic Engineer, 1976, vol. 46, pp. 360-364.
[52] L. W. Cahill, “Approximate formulae for microstrip transmission lines”, Proc. IREE, 1974, vol. 3, pp. 317-321.
[53] B. W. Hakki and P. D. Coleman, “A dielectric resonator method of measuring inductive capacities in the millimeter range”, IEEE Trans. on Microwave Theory Tech., 1960, MTT-8, pp. 402-410.
[54] William E. Courtney, “Analysis and evaluation of a method of measuring the complex permittivity and permeability of microwave insulators”, IEEE Trans. on Microwave Theory and Techniques, 1970, MTT-18, pp. 476-485.
[55] P. Wheless and D. Kajfez, “The use of higher resonant modes in measuring the dielectric constant of dielectric resonators”, IEEE MTT-S Symposium Dig., 1985, pp. 473-476.
[56] Yoshio Kobayashi and S. Tanaka, “Resonant modes of a dielectric rod resonator short-circuited at both ends by parallel conducting plates”, IEEE Trans. on Microwave Theory and Techniques, 1980, MTT-28, pp. 1077-1085.
[57] Darko Kajfez and Pierre Guillon, “Dielectric resonators”, Artech House, Washington, 1986, pp. 339-344.
[58] Yoshio Kobayashi and M. Katoh, “Microwave measurement of dielectric properties of low-loss materials by the dielectric rod resonator method”, IEEE Trans. on Microwave Theory and Techniques, 1985, MTT-33, pp. 586-592.
[59] S. B. Cohn and K. C. Kelly, “Microwave measurement of high-dielectric constant materials”, IEEE Trans. on Microwave Theory and Techniques, 1966, MTT-14, pp. 406-410.
[60] W. D. Kingery, H. K. Bowen and D. R. Uhlmann, “Introduction to ceramics”, John Wiley & Sons, 1975, Chapter 10, pp. 461-465.
[61] M. A. Subramanianm and J. C. Calabrese, “Crystal structure of the low temperature form of bismuth niobium oxide”, Mater. Res. Bull., 1993, vol. 28, pp. 523-529.
[62] L. Wu, C. F. Yang and T. S. Wu, “The influence of sintering and annealing temperature on grain boundary barrier layer capacitors in a modified reduction-reoxidation method”, J. Mater. Sci. Materials in Electronics, 1992, vol. 3, pp. 272-277.
[63] C. L. Huang and C. S. Hus, “Improved high Q value of 0.5LaAlO3-0.5SrTiO3 microwave dielectric ceramics at low sintering temperature”, Mater. Res. Bull., 2001, vol. 36, pp. 2677-2687.
[64] E. F. Keve and A. C. Skapski, “The crystal structure of triclinic β-BiNbO4”, J. of Solid State Chemistry, 1973, vol. 8, pp. 159-165.
[65] M. H. Kim, S. Nahm, C. H. Choi, H. J. Lee and H. M. Park, “Dielectric properties of (1-x)NdGaO3-xCaTiO3 solid solution at microwave frequencies”, Jpn. J. Appl. Phys., 2002, vol. 41, pp. 717-721.
[66] JCPDS card Nos. 16-906 and 16-0909, 1997 JCPDS International Center for Diffraction Data Formerly by the Joint Committee on Power Diffraction Standards.
[67] C. L. Huang, M. H. Weng and C. C. Wu, “The microwave dielectric properties and the microstructures of La2O3-modified BiNbO4 ceramics”, Jpn. J. Appl. Phys., 2000, vol. 39, pp. 3506-3510.
[68] C. F. Yang and S. H. Lo, “Effect of glass addition on BaTi4O9 microwave ceramics”, J. Mater. Sci. Lett., 1998, vol. 17, pp. 1029-1032.
[69] W. Wersing, “Electronic Ceramics”, Elsevier, London, 1991, pp. 67-85.
[70] JCPD card Nos. 21-1276, 26-0040 and 82-1399, 1997 JCPDS International Center for Diffraction Data Formerly by the Joint Committee on Power Diffraction Standards.
[71] C. F. Yang, “The microwave characteristics of glass-BaTi4O9 ceramics”, Jpn. J. Appl. Phys., 1999, vol. 38, pp. 3576-3579.
[72] C. M. Cheng, C. F. Yang and S. H. Lo, “Sintering and dielectric properties of Ba2Ti9O20 microwave ceramics by glass addition”, Jpn. J. Appl. Phys., 1997, vol. 36, pp. L1604-L1607.
[73] C. L. Huang, R. J. Lin and H. L. Chen, “Microwave dielectric properties and microstructures of CuO- and ZnO-doped LaAlO3 ceramics”, Mater. Res. Bull., 2002, vol. 37, pp. 449-457.
[74] Fulrath Pask, “Ceramic microstructures”, Plenum Press, New York, 1968, pp. 102-135.
[75] T.K. Lo, C.O. Ho, Y. Hwang, E.K.W. Lam and B. Lee, “Miniature aperture- coupled microstrip antenna of very high permittivity”, Electron Lett , 1997, vol. 33, pp. 9-10.
[76] Y. Hwang, Y. P. Zhang, K. M. Luk and E. K. N. Yung, “Gain-enhanced miniaturized rectangular dielectric resonator antenna”, Electron Lett, 1997, vol. 33, pp. 350-352.
[77] K. F. Lee, K. Y. Ho and J. S. Dahele, “Circular-disk microstrip antenna with an air gap”, IEEE Trans. Antennas Propagat., 1984, vol. 32, pp. 880-884.
[78] E. Changs, S. A. Long and W. F. Richards, “Experimental investigation of electrically thick rectangular microstrip antennas”, IEEE Trans. Antennas Propagat., 1986, vol. 34, pp. 767-772.
[79] K. S. Fong, H. F. Pues and M. J. Withers, “Wideband multiplayer coaxial-fed microstrip antenna element”, Electron. Lett., 1985, vol. 21, pp. 497-499.
[80] P. S. Hall, C. Wood and C. Garrett, “Wide bandwidth microstrip antennas for circuit integration”, Electron. Lett., 1979, vol. 15, pp. 458-460.
[81] R. Q. Lee, K. F. Lee and J. Bobinchak, “Characteristics of a two-layer electromagnetically coupled rectangular patch antenna”, Electron. Lett., 1987, vol. 23, pp. 1070-1072.
[82] R. Q. Lee and K. F. Lee, “Experimental study of the two-layer electromagnetically coupled rectangular patch antenna”, IEEE Trans. Antennas Propagat., 1990, vol. 38, pp. 1298-1302.
[83] P. S. Bhatnagar, J. P. Daniel, K. Mahdjoubi and C. Terret, “Experimental study on stacked triangular microstrip antennas”, Electron. Lett., 1986, vol. 22, pp. 864-865.
[84] C. Wood, “Improved bandwidth of microstrip antennas using parasitic elements”, IEE Proc. H, 1980, vol. 127, pp. 231-234.
[85] G. Kumar and K. C. Gupta, “Broad-band microstrip antennas using additional resonators gap-coupled to the radiating edges”, IEEE Trans. Antennas Propagat., 1984, vol. 32, pp. 1375-1379.
[86] Y. F. Lin and K. L. Wong, “Compact broadband triangular microstrip antenna with an inset microstrip-line feed”, Microwave Opt. Technol. Lett., 1998, vol. 17, pp. 169-170.
[87] G. Kumar and K. C. Gupta, “Nonradiating edges and four edges gap-coupled multiple resonator broad-band microstrip antenna”, IEEE Trans. Antennas Propagat., 1985, vol. 33, pp. 173-178.
[88] N. Fayyaz and S. Safavi-Naeini, “Bandwidth enhancement of a rectangular patch antenna by integrated reactive loading”, IEEE AP-S Int. Symp. Dig., 1998, vol. 2, pp. 1100-1103.
[89] J. Y. Sze and K. L. Wong, “Broadband circuit microstrip antenna with embedded reactive loading”, Electron. Lett., 1998, vol. 34, pp. 1804-1805.
[90] Y. X. Guo, K. M. Luk and K. F. Lee, “L-probe proximity-fed short-circuited patch antenna”, Electron. Lett., 1999, vol. 35, pp. 2069-2070.
[91] H. M. Chen, J. Y. Sze and Y. F. Lin, “A broadband rectangular microstrip antenna with a pair of U-shaped slots”, Microwave Opt. Technol. Lett. 2000, vol. 27, pp. 369-370.
[92] Y. X. Guo, K. M. Luk, K. F. Lee and Y. L. Chow, “Double U-slot rectangular patch antenna”, Electron. Lett. 1998, vol. 34, pp. 1805-1806.
[93] K. F. Tong, K. M. Luk, K. F. Lee and R. Q. Lee, “A broad-band U-slot rectangular patch antenna on a microwave substrate”, IEEE Trans. Antennas Propagat. 2000, vol. 48, pp. 954-959.
[94] C. L. Mak, K. M. Luk, and K. F. Lee, “Proximity-coupled U-slot patch antenna”, Electron. Lett.1998, vol. 34, pp. 715-716.
[95] D. M. Pozar and B. Kaufman, “Increasing the bandwidth of a microstrip antenna by proximity coupling”, Electron. Lett., 1987, vol. 23, pp. 368-369.
[96] IE3D user’s manual, Zeland Software, Inc., Aug. 1998.
[97] Vittorio Cirilli, Aurelio Burdese and Cesare Brisi, “Phase diagram for CuO-V2O5”, Atti. Accad. Sci. Torino, 1961, vol. 95, p. 15.