In this paper, a quad-antenna system for laptop computers is studied. Because two dual-antenna systems can construct a quad-antenna system, the dual-antenna systems in the open literature are utilized. The mutual coupling between the two dual-antenna systems is analyzed and reduced. To validate the design of a quad-antenna system, the quad-antenna system, consisting of two dual-antenna systems proposed in the open literature and a decoupling element, is fabricated and tested. Its measured -10 dB impedance bandwidths are 200 MHz (2.33-2.52 GHz) and 1.62 GHz (4.5-6.12 GHz). The measured mutual couplings are below -15.5/-19 dB at the 2.4- and 5.2/5.8-GHz WLAN bands, respectively. The measured gains are better than 2.4/3.9 dBi with efficiencies higher than 70%/72% at the two bands, respectively. The envelop correlation coefficient is evaluated based on the measured results.
2., "Wireless LAN specification to provide significantlyimproved data throughput and range,", IEEE 802.11n, 2012, Online Available: http://standards.ieee.org/announcements/ieee802.11n.
doi:10.2528/PIER07052203
3. Jensen, M. A. and J. W. Wallace, "A review of antennas and propagation for MIMO wireless communication," IEEE Trans. Antennas Propag., Vol. 52, No. 11, 2810-2824, Nov. 2004.
doi:10.2528/PIER12040603
4. Wen, G., "Multi-antenna information theory," Progress In Electromagnetics Research, Vol. 75, 11-50, 2007.
doi:10.2528/PIER12090610
5. Yu, X. H., L.Wang, H.-G.Wang, X.Wu, and Y.-H. Shang, "A novel multiport matching method for maximum capacity of an indoor MIMO system," Progress In Electromagnetics Research, Vol. 130, 67-84, 2012.
doi:10.2528/PIER12080604
6. Sharawi, M. S., A. B. Numan, and D. N. Aloi, "Isolation improvement in a dual-band dual-element MIMO antenna system using capacitively loaded loops," Progress In Electromagnetics Research, Vol. 134, 247-266, 2013.
doi:10.1109/LAWP.2012.2188824
7. Lee, J.-H. and C.-C. Cheng, "Spatial correlation of multiple antenna arrays in wireless communication systems," Progress In Electromagnetics Research, Vol. 132, 347-368, 2012.
doi:10.1002/mop.24831
8. Addaci, R., A. Diallo, C. Luxey, P. L. Thuc, and R. Staraj, "Dual-band WLAN diversity antenna system with high port-to-port isolation," IEEE Antennas Wireless Propag. Lett., Vol. 11, 244-247, 2012.
doi:10.1002/mop.27279
9. Kang, T. W. and K.-L. Wong, "Isolation improvement of 2.4/5.2/5.8 GHz WLAN internal laptop computer antennas using dual-band strip resonator as a wavetrap," Microw. Opt. Technol. Lett., Vol. 52, No. 1, 58-64, Apr. 2010.
doi:10.1109/LAWP.2014.2303495
10. Wong, K.-L., H.-H. Jiang, and Y.-C. Kao, "High-isolation 2.4/5.2/5.8-GHz WLAN MIMO antenna array for laptop computer application," Micro. Opt. Technol. Lett., Vol. 55, No. 2, 382-387, 2013.
11. Guo, L., 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, 229-232, 2014.
12. LTE Advanced the 3rd Generation Partnership Project, 2011, , Online Available: http://www.3gpp.org/LTE-Advanced.
doi:10.1109/LAWP.2006.873948
13. Martin, C. C., J. H. Winters, and N. R. Sollenberger, "Multiple-input multiple-output (MIMO) radio channel measurements," Proc. IEEE VTC Fall 2000, Vol. 2, 774-779, 2000.
doi:10.1109/TAP.2010.2103020
14. Guterman, J., A. A. Moreira, and C. Reixeiro, "Integration of omnidirectional wrapped microstrip antennas into laptops," IEEE Antennas Wireless Propag. Lett., Vol. 5, 141-144, 2006.
doi:10.1163/156939312800030929
15. Wong, K. L., W.-Y. Chen, and T.-W. Kang, "On-board printed coupled-fed loop antenna in close proximity to the surrounding ground plane for penta-band WWAN mobile phone," IEEE Trans. Antennas Propag., Vol. 59, No. 3, 751-757, Mar. 2011.
doi:10.1109/T-VT.1987.24115
16. Chen, J.-H., Y.-L. Ban, H.-M. Yuan, and Y.-J. Wu, "Printed coupled-fed PIFA for seven-band GSM/UMTS/LTE/WWAN mobile phone," Journal of Electromagnetics Waves and Applications, Vol. 26, No. 2-3, 390-401, 2012.
17. Vaughan, G. B. and J. B. Andersen, "Antenna diversity in mobile communication," IEEE Trans. Veh. Technol., Vol. 36, No. 4, 149-172, Nov. 1987.