本研究開發了一分集天線量測系統並提出可包含LTE全頻帶的寬頻天線設計。第一部分提出了一個低成本、半自動的量測系統架構，可用來對多天線系統的有效分集增益做評估。架構分成發射端及接收端兩個部分。發射端由訊號產生器及參考天線提供一連續波訊號；接收端包含一個控制用的主機、多通道資料擷取卡、RF功率檢測器，以及待測的多天線系統。系統可自動讀取並記錄數據，在一富含多重路徑且無嚴重背景雜訊的環境中，可以快速獲得多天線系統的有效分集增益值。為了驗證量測系統的有效性，本研究對分集天線以及多天線系統進行了測試。相較於現有的分集效能評估方法，此量測系統不僅提供了合理的量測結果，更節省了大量的時間和人力。此外，它可以同時量測大量的天線，滿足高階MIMO多天線系統的評估需要。
第二部分提出了一個在平板上使用，支援MIMO的LTE雙天線系統架構。為了能在窄邊框的行動裝置中使用，天線使用軟性印刷電路板製成。天線結構簡單，主要由摺疊的金屬片及槽縫所構成。該設計可以提供非常大的操作頻寬，常用的LTE頻段，包括690至960 MHz和1710至2690 MHz都可涵蓋在內，並擁有不錯的匹配和輻射特性。本研究也將此天線設計成一個雙天線系統的架構，透過改變兩個天線在平板上的擺放位置，取得一個合理的隔離度表現，並透過破地結構技術進一步降低天線間的耦合。輻射場型和封包相關係數都顯示其具有良好的分集效能。在多重路徑豐富的環境中，進行測量並取得有效分集增益值。結果證明，此雙天線系統可符合MIMO系統的傳輸需求。

This thesis is focused on the development of an antenna measurement system and a broadband antenna applicable for LTE uses. The first part is about a low-cost, semi-automatic effective diversity gain measurement system for multi-antenna systems. It comprises a transmitter and a receiving end. Continuous waves are provided by a signal generator and emitted from a reference antenna. The receiving end contains a control computer, a multi-channel data acquisition card, RF power detectors, and the multi-antenna system under test. The system can automatically read and record the data. Measurements of basic diversity antenna setups as well as multi-antenna systems were tested to validate the effectiveness of the proposed approach. Comparing to existing diversity evaluation methods, this approach provides not only convincing results but also saves a lot in time and cost.
The second part is about a two-antenna system for LTE MIMO uses on tablets. To be integrated within slim portable devices, the proposed antenna is made with a flexible printed circuit board. The antenna structure is simple, which is a folded metal sheet with slots. It provides very broad operation bands. Commonly used LTE bands including 690 to 960 MHz and 1710 to 2690 MHz bands are covered with decent matching and radiation characteristics. A two-antenna displacement scheme on tablet is proposed with a fair isolation performance. The defected ground structure technique is employed to further reduce antenna coupling. Performance features such as radiation patterns, envelope correlation coefficient and effective diversity gain are measured. All the results validate that it is suitable for MIMO uses.

[1] J. Winters, “On the capacity of radio communication systems with diversity in a Rayleigh fading environment,” IEEE J. Select. Areas Commun., vol. JSAC-5, pp. 871–878, Jun. 1987.

[2] A. Goldsmith, S. A. Jafar, N. Jindal, and S. Vishwanath, “Capacity limits of MIMO channels,” IEEE J. Sel. Areas. Commun., vol. 21, no. 5, pp. 684–702, Jun. 2003.

[3] A. Sibille, C. Oestges, and A. Zanella, MIMO: from Theory to Implementation, Burlington, MA, Academic Press, 2011.

[4] T. W. Kang, and K. L. Wang, “Isolation improvement of WLAN internal laptop computer antennas using dual-band strip resonator,” IEEE Conference Publications, pp. 2478–2481, 2009.

[5] C. H. Wu, H. N. Chu, C. A. Lin and T. G. Ma, “A decoupling network for two-element array using uniform coupled-line sections,” IEEE Conference Publications, pp. 457–458, 2014.

[6] S. D. Assimonis, T. V. Yioultsis, and C. S. Antonopoulos, “Computational investigationand design of planar EBG structures for coupling reductionin antenna applications,” IEEE Trans. Magn., vol. 48, no. 2, pp. 771–774, Feb. 2012.

[7] C. C. Hsu, K. H. Lin, and H. L. Su, “Implementation of broadband isolator using metamaterial-inspired resonators and a T-shaped branchfor MIMO antennas,” IEEE Trans. Antennas Propag., vol. 59, no. 10, pp. 3936–3939, Oct. 2011.

[8] T. Y. Wu, S. T. Fang, and K. L. Wong, “Printed diversity monople antenna for WLAN operation,” Electron. Lett., vol. 38, no. 25, pp. 1625-1626, Dec. 2002.

[9] Y. L. Ban, S. Yang, Z. Chen, K. Kang, and J. L. W. Li, “Decoupled planar WWAN antennas with T-shaped protruded ground for smartphone applications,” IEEE Antennas Wireless Propag. Lett., vol. 13, pp. 483–486, 2014.
[10] L. Guo, Y. Wang, Z. Du, Y. Gao, and D. Shi “A compact uniplanar printed dual antenna operating at the 2.4/5.2/5.8 GHz WLAN bands for laptop computers,” IEEE Antennas Wireless Propag. Lett., vol. 13, pp. 229–232, 2014.

[11] H. Li, J. Xiong, and S. He, “A compact planar MIMO antenna system of four elements with similar radiation characteristics and isolation structure,” IEEE Antennas Wireless Propag. Lett., vol. 8, pp. 1107–1110, 2009.

[12] S. W. Su, C. T. Lee, and F. S. Chand, “Printed MIMO-antenna system using Neutralization-line technique for wireless USB-dongle applications,” IEEE Antennas Wireless Propag. Lett., vol. 60, no.2, pp.456-463, Feb. 2012.

[13] H. Paul, “The significance of radiation efficiencies when using S-parameters to calculate the received signal correlation from two antennas,” IEEE Antenna. Wireless Propag. Lett., vol. 4, no. 1, pp. 97–99, Jun. 2005.

[14] J. F. Li, Q. X. Chu, and T. G. Huang, “A compact wideband MIMO antenna with two novel bent slits,” IEEE Trans. Antennas Propag., vol. 60, no. 2, pp. 482-489, Feb. 2012.

[15] M. A. Jensen and Y. Rahmat-Samii, “Performance analysis of antennas for hand-held transceivers using FDTD,” IEEE Trans. Antennas Propag., vol. 42, no. 8, pp. 1106–1113, Aug. 1994.

[16] R. G. Vaughan and J. B. Andersen, “Antenna diversity in mobile communications,” IEEE Trans. Veh. Technol., vol. VT-36, pp. 149-172, Nov. 1987.

[17] V. C. Papamichael, “Selection-combining diversity performance of actual multielement antenna systems using the covariance matrix method,” IEEE Antennas Wireless Propag. Lett., vol. 9, pp. 705-707, 2010.

[18] W. C. Lee, Mobile Communications Engineering, 2nd ed. New York: McGraw-Hill, 1998.

[19] W.-J. Liao, S.-H. Chang, J.-T. Yeh, B.-R. Hsiao, “Compact dual-band WLAN diversity antennas on USB dongle platform,” IEEE Trans. Antennas Propag., vol. 62, no. 1, pp. 109-118, Jan. 2014.
[20] Z. Li, Z. Du, M. Takahashi, K. Saito, and K. Ito, "Reducing mutual coupling of MIMO antennas with parasitic elements for mobile terminals," IEEE Trans. Antennas Propag., vol. 60, no. 2, pp. 473-481, Feb. 2012.

[21] K. Payandehjoo and R. Abhari, "Compact multi-band PIFAs on a semi-populated mobile handset with tunable isolation," IEEE Trans. Antennas Propag., vol. 61, no. 9, pp. 4814-4819, Sep. 2013.

[22] S. Ghosh, T.-N. Tran, and T. Le-Ngoc, “Miniaturized four-element diversity PIFA,” IEEE Antennas Wireless Propag. Lett., vol. 12, pp. 396–400, 2013.

[23] M. P. Karaboikis, V. C. Papamichael, G. F. Tsachtsiris, C. F. Soras, and V. T. Makios, “Integrating compact printed antennas onto small diversity/MIMO terminals,” IEEE Trans. Antennas Propag., vol. 56, no. 7, pp. 2067–2078, Jul. 2008.

[24] W.-J. Liao, C.-Y. Hsieh, B.-Y. Dai, B.-R. Hsiao, “Inverted-F/slot integrated dual-band four-antenna system for WLAN access points,” IEEE Antenna Wireless Propag. Lett., vol. 14, pp.847-850, 2015.

[25] Mini-Circuits, Coaxial Power Detector ZX47-60+/ZX47-60LN+, datasheet, [online] http://www.minicircuits.com/pdfs/ZX47-60+.pdf

[26] Advantech, PCI-1711U/UL, datasheet, [Online]
http://downloadt.advantech.com/ProductFile/PIS/PCI-1711U/Product-Datasheet/PCI-1711U_DS20140505160816.pdf

[27] D. Kim, M. A. Ingram, and W. W. Smith, “Small-scale fading for an indoor wireless channel with modulated backscatter,” in Proc. of 2001 IEEE Vehicular Tech. Conf., pp. 1616–1620, Oct. 2001.

[28] E. Tanghe, W. Joseph, P. Ruckebusch, L. Martens, and I. Moerman, “Intra-, inter-, and extra-container path loss for shipping container monitoring systems,” IEEE Antenna Wireless Propag. Lett., vol. 11, pp. 889–892, 2012.

[29] C.-L. Hu, D.-L. Huang, H.-L. Kuo, C.-F. Yang, C.-L. Liao, and S.-T. Lin, “Compact multibranch inverted-F antenna to be embedded in a laptop computer for LTE/WWAN/IMT-E applications,” IEEE Antennas Wireless Propag. Lett., vol. 9, pp. 838–841, 2010.

[30] C.-W. Yang, Y.-B. Jung, and C. W. Jung, “Octaband internal antenna for 4G mobile handset,” IEEE Antennas Wireless Propag. Lett., vol. 10, pp. 817–819, 2011.

[31] W.-J. Liao, S.-H. Chang, L.-K. Li, “A compact planar multiband antenna for integrated mobile devices,” Progress in Electromagnetics Research, vol. 109, pp. 1-16, 2010.

[32] K.-L. Wong and C.-Y. Tsai, “Small-size stacked inverted-F antenna with two hybrid shorting strips for the LTE/WWAN tablet device,” IEEE Trans. Antennas Propag., vol. 62, no. 8, pp. 3962-3969, Aug. 2014.

[33] T.-W. Kang, K.-L. Wong, L.-C. Chou, and M.-R. Hsu, “Coupled-fed shorted monopole with a radiating feed structure for eight-band LTE/WWAN operation in the laptop computer,” IEEE Trans. Antennas Propag., vol. 59, no. 2, pp. 674-679, Feb. 2011.

[34] B. Mun, C. Jung, M.-J. Park, and B. Lee, “A compact frequency-reconfigurable multiband LTE MIMO antenna for laptop applications,” IEEE Antennas Wireless Propag. Lett., vol. 13, pp. 1389–1392, 2014.

[35] C.-T. Lee and K.-L. Wong, “Planar monopole with a coupling feed and an inductive shorting strip for LTE/GSM/UMTS operation in the mobile phone,” IEEE Trans. Antennas Propag., vol. 58, no. 7, pp. 2479-2483, Jul. 2010.

[36] M. K. Meshram, R. K. Animeh, A. T. Pimpale, and N. K. Nikolova, “A novel quad-band diversity antenna for LTE and Wi-Fi applications with high isolation,” IEEE Trans. Antennas Propag., vol. 60, no. 9, pp. 4360-4371, Sep. 2012.

[37] F.-H. Chu and K.-L. Wong, “Planar printed strip monopole with a closely-coupled parasitic shorted strip for eight-band LTE/GSM/UMTS mobile phone,” IEEE Trans. Antennas Propag., vol. 58, no. 10, pp. 3426-3431, Oct. 2010.

[38] S.-H. Chang, W.-J. Liao, “A broadband LTE/WWAN antenna design for tablet PC,” IEEE Trans. Antennas Propag., vol. 60, no. 9, pp. 4354-4359, Sep. 2012.
[39] J. Lee, Y. Liu, and H. Kim, “Mobile antenna using multi-resonance feed structure for wideband operation,” IEEE Trans. Antennas Propag., vol. 62, no. 11, pp. 5851-5855, Nov. 2014.

[40] J. Villanen, J. Ollikainen, O. Kivekas, and P. Vainikainen, “Coupling element based mobile terminal antenna structures,” IEEE Trans. Antennas Propag., vol. 54, no. 7, pp. 2142-2153, Jul. 2006.

[41] R. Valkonen, M. Kaltiokallio, and C. Icheln, “Capacitive coupling element antennas for multi-standard mobile handsets,” IEEE Trans. Antennas Propag., vol. 61, no. 5, pp. 2783-2791, May 2013.

[42] J. Ilvonen, R. Valkonen, J. Holopainen, and V. Viikari, “Design strategy for 4G handset antennas and a multiband hybrid antenna,” IEEE Trans. Antennas Propag., vol. 62, no. 4, pp. 1918-1927, Apr. 2014.

[43] R. Martens, J. Holopainen, E. Safin, J. Ilvonen, and D. Manteuffel, “Optimal dual-antenna design in a small terminal multiantenna system,” IEEE Antennas Wireless Propag. Lett., vol. 12, pp. 1700–1703, 2013.

[44] Y.-L. Ban, Z.-X. Chen, Z. Chen, K. Kang, and J. L.-W. Li “Decoupled closely spaced heptaband antenna array for WWAN/LTE smartphone applications,” IEEE Antennas Wireless Propag. Lett., vol. 13, pp. 31–34, 2014.

[45] I. Dioum, A. Diallo, S. M. Farssi, and C. Luxey, “A novel compact dual-band LTE antenna-system for MIMO operation,” IEEE Trans. Antennas Propag., vol. 62, no. 4, pp. 2291-2296, Apr. 2014.

[46] B. Lee, F. J. Harackiewicz, and H. Wi, “Closely mounted mobile handset MIMO antenna for LTE 13 band application,” IEEE Antennas Wireless Propag. Lett., vol. 13, pp. 411–414, 2014.

[47] J. Lee, Y.-K. Hong, S. Bae, G. S. Abo, W.-M. Seong, and G.-H. Kim, “Miniature long-term evolution (LTE) MIMO ferrite antenna,” IEEE Antennas Wireless Propag. Lett., vol. 10, pp. 603–606, 2011.

[48] Y.-J. Ren, “Ceramic based small LTE MIMO handset antenna,” IEEE Trans. Antennas Propag., vol. 61, no. 2, pp. 934-938, Feb. 2013.
[49] D.-B. Lin, .J.-H. Chou, C.-Y. Wu, and H.-J. Li, “A novel miniaturized dual-layered LTE printed antenna for handheld devices,” IEEE Antennas Wireless Propag. Lett., vol. 12, pp. 1680–1683, 2013.

[50] Z. Miers, H. Li, and B. K. Lau, “Design of bandwidth-enhanced and multiband MIMO antennas using characteristic modes,” IEEE Antennas Wireless Propag. Lett., vol. 12, pp. 1696–1699, 2013.

[51] S. C. Fernandez and S. K. Sharma, “Multiband printed meandered loop antennas with MIMO implementations for wireless routers,” IEEE Antennas Wireless Propag. Lett., vol. 12, pp. 96–99, 2013.

[52] S. Zhang, K. Zhao, Z. Ying, and S. He, “Adaptive quad-element multi-wideband antenna array for user-effective LTE MIMO mobile terminals,” IEEE Trans. Antennas Propag., vol. 61, no. 8, pp. 4275-4283, Aug. 2013.

[53] H. T. Chattha, M. Nasir, Q. H. Abbasi, Y. Huang, and S. S. AlJa’afreh, “Compact low-profile dual-port single wideband planar inverted-F MIMO antenna,” IEEE Antennas Wireless Propag. Lett., vol. 12, pp. 1673–1675, 2013.

[54] X. Zhou, X. Quan, and R. Li, “A dual-broadband MIMO antenna system for GSM/UMTS/LTE and WLAN handsets,” IEEE Antennas Wireless Propag. Lett., vol. 11, pp. 551–554, 2012.

[55] Y.-L. Ban, Z.-X. Chen, Z. Chen, K. Kang, and J. L.-W. Li, “Decoupled hepta-band antenna array for WWAN/LTE smartphone applications,” IEEE Antennas Wireless Propag. Lett., vol. 13, pp. 999–1002, 2014.

[56] K. Payandehjoo and R. Abhari, “Compact multi-band PIFAs on a semi-populated mobile handset with tunable isolation,” IEEE Trans. Antennas Propag., vol. 61, no. 9, pp. 4814-4819, Sep. 2013.

[57] J.-T. Yeh, W.-J. Liao, S.-H. Chang, “Compact internal antenna for handheld devices with comprehensive DTV band coverage,” IEEE Trans. Antennas Propag., vol. 62, no. 8, pp. 3998-4007, Aug. 2014.