Electrically Small, Planar, Horizontally Polarized Dual-band Omnidirectional Antenna and its Application in a MIMO System

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

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Original languageEnglish
Journal / PublicationIEEE Transactions on Antennas and Propagation
Online published4 Mar 2021
Publication statusOnline published - 4 Mar 2021


A method of designing a miniature planar dual-band horizontally polarized omnidirectional antenna is presented. It combines an electrically small lower-band omnidirectional loop antenna with an upper-band Alford loop antenna on a single substrate. Its frequency ratio is higher than two. A technique that effectively increases the bandwidth of the Alford loop is developed. To reduce the gain variation in the azimuthal plane, the electrically small loop is fed by four symmetrical radial strips extended from a circular patch. For demonstration, the electrically small loop and Alford loop were designed for the 2.4- and 5-GHz Wi-Fi bands for Wi-Fi applications. The antenna prototype has a diameter of 0.296λ0 and a height of 0.012λ0 only, where λ0 is the wavelength in air at the lowest operating frequency. It covers the Wi-Fi bands of 2.4–2.5 GHz and 5.1–5.9 GHz, with a high total efficiency of ~90%. Based on the single-element design, a four-element multiple-input-multiple-output (MIMO) antenna is developed for Wi-Fi applications. The MIMO antenna has a size of 0.93×0.93×0.012λ03, with a small gain variation of less than 3.2 dB in the azimuthal plane. The isolations between any two antenna elements are higher than 16 dB and 24.5 dB for the 2.4-GHz and 5-GHz bands, respectively.

Research Area(s)

  • electrically small antenna, horizontally polarized antenna, Omnidirectional antenna, dual-band antenna