A low-profile, decoupled two-monopole system with its two parasitic grounded strips conjoined, forming a very compact structure is demonstrated. Each of the two identical antennas comprises a driven coupling strip and a parasitic grounded strip, operating respectively in the 2.4 GHz (2400-2484 MHz) and 5 GHz (5150-5825 MHz) wireless local area network (WLAN) bands. The two parasitic strips are further joined together, becoming a central, grounded T monopole. By loading a capacitor between the T monopole and the antenna ground, the mutual coupling in the 2.4 GHz band can be reduced by about 12 dB. The capacitor in this design is used to control Ant2 monopole mode to cancel out opposite-phased currents of the dipole mode on the T monopole when Ant1 is excited, such that isolation enhancement can be attained. The proposed two-monopole system occupies a compact size of 5 mm × 40 mm (about 0.04λ × 0.32λ at 2.4 GHz) and is favorable for applications in the narrow-bezel notebook computers owing to its low profile of 5 mm.
2. Khorov, E., A. Kiryanov, A. Lyakhov, and G. Bianchi, "A tutorial on IEEE 802.11ax high efficiency WLANs," IEEE Comm. Surveys & Tutorials, Vol. 21, 197-216, 2019.
3. Mak, A. C. K., C. R. Rowell, and R. D. Murch, "Isolation enhancement between two closely packed antennas," IEEE Trans. Antennas Propagat., Vol. 56, 3411-3419, 2008.
4. 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, 58-64, 2010.
5. 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 Propagat. Lett., Vol. 13, 229-232, 2014.
6. Liu, Y., Y. Wang, and Z. Du, "A broadband dual-antenna system operating at the WLAN/WiMax bands for laptop computers," IEEE Antennas Wireless Propagat. Lett., Vol. 14, 1060-1063, 2015.
7. Deng, J. Y., J. Y. Li, L. Zhao, and L. X. Guo, "A dual-band inverted-F MIMO antenna with enhanced isolation for WLAN applications," IEEE Antennas Wireless Propagt. Lett., Vol. 16, 2270-2273, 2017.
8. Su, S. W. and Y. W. Hsiao, "Small-sized, decoupled two-monopole antenna system using the same monopole as decoupling structure," Microw. Opt. Technol. Lett., Vol. 61, 2049-2055, 2019.
9. Su, S.-W., C. T. Lee, and Y. W. Hsiao, "Compact two-inverted-F-antenna system with highly integrated π-shaped decoupling structure," IEEE Trans. Antennas Propagat., Vol. 67, 6182-6186, 2019.
10. Su, S.-W., C. T. Lee, and S. C. Chen, "Very-low-profile, triband, two-antenna system for WLAN notebook computers," IEEE Antennas Wireless Propagat. Lett., Vol. 17, 1626-1629, 2018.
11. Sui, J. and K. L. Wu, "Self-curing decoupling technique for two inverted-F antennas with capacitive loads," IEEE Trans. Antennas Propagat., Vol. 68, 1093-1101, 2018.
12. Wong, K. L., B. W. Lin, and S. E. Lin, "High-isolation conjoined loop multi-input multi-output antennas for the fifth-generation tablet device," Microw. Opt. Technol. Lett., Vol. 61, 111-119, 2019.
13. Su, S.-W., "Very-low-profile, 2.4/5-GHz WLAN monopole antenna for large screen-to-body-ratio notebook computers," Microw. Opt. Technol. Lett., Vol. 60, 1313-1318, 2018.
14. Su, S.-W., C. T. Lee, and S. C. Chen, "Compact, printed, tri-band loop antenna with capacitivelydriven feed and end-loaded inductor for notebook computers," IEEE Access, Vol. 6, 6692-6699, 2018.
15. Su, S.-W., "Capacitor-inductor-loaded, small-sized loop antenna for WLAN notebook computers," Progress In Electromagnetics Research M, Vol. 71, 179-188, 2018.
16. Su, S.-W., "Very-low-profile, small-sized, printed monopole antenna for WLAN notebook computer applications," Progress In Electromagnetics Research Letters, Vol. 82, 51-57, 2019.
17., , ANSYS HFSS, ANSYS Inc., https://www.ansys.com/Products/Electronics/ANSYS-HFSS.
18., "Novel and efficient parasitic decoupling network for closely coupled antennas," IEEE Trans. Antennas Propagat., Vol. 67, 3574-3585, 2019.
19., , SG 64, SATIMO, http://www.mvg-world.com/en/products/field product family/antennameasurement- 2/sg-64.
20. Volakis, J. L., Antenna Engineering Handbook, 4th Edition, Chapter 6, 16–19, McGraw-Hill, New York, 2007.
21. Balanis, C. A., Antenna Theory: Analysis and Design, 3rd Edition, Chapter 2, Wiley, Hoboken, NJ, 2012.