What question did this study set out to answer?

The aim is to develop a compact and efficient PIFA MIMO antenna suitable for 5G and WLAN applications.

March 13, 2026Open Access

Compact Wideband PIFA MIMO Antenna Based on the Characteristics Mode Analysis for 5G/WLAN Wireless Applications

Key Points

The aim is to develop a compact and efficient PIFA MIMO antenna suitable for 5G and WLAN applications.
Optimized using characteristic mode theory (CMT) for better performance.
Analyzed for SAR and MIMO diversity parameters.
Conducted iterations modifying antenna structure and applying an integral solver.
Ground plane tuned with eight slots for enhancing bandwidth and isolation.
Achieved isolation better than 20 dB across 3.2-5.46 GHz with 52.19% fractional bandwidth.
Attained gain of 5.5–7 dBi and average efficiency of 84%.
Demonstrated stable performance with data rates over 25 Gbps and connectivity exceeding 10 Gbps at distances beyond 80 m.
SAR values are compliant with international limits, ensuring safe usage.

Abstract

• The article presents a PIFA MIMO antenna for 5G and WLAN bands. • The proposed antenna is optimized by characteristic mode theory (CMT). • The proposed antenna is analyzed for SAR and MIMO diversity parameters. This article presents a compact, wideband, four-port, multiple-input-multiple-output (MIMO) planar inverted-F antenna (PIFA) for the sub-6 GHz 5G and WLAN bands. The dimensions and strategic placements of the shorting pin, feed plate, and radiator are determined using characteristic mode theory (CMT), as it is a rapid development tool. The current distribution on the antenna structure is solved using an integral solver to investigate and enhance the specific mode of interest. The process is repeated by modifying the antenna structure and applying the solver till the desired modes are generated. Through CMT, two complementary structures are evolved and incorporated into the MIMO antenna for efficient performance. Furthermore, the antennas ground plane is tuned with eight slots, which enhanced the bandwidth, isolation, and directivity (at θ = ± 52 ∘ ). Again, these slot positions have been strategically chosen to keep the ground free for other RF circuitry. The four radiating elements are arranged to exploit the benefits of spatial and pattern diversity, achieving isolation better than 20 dB across the 3.2-5.46 GHz operating band (52.19% fractional bandwidth). The antenna achieves a gain of 5.5–7 dBi with an average total efficiency of 84%. MIMO performance metrics, including envelope correlation coefficient (ECC), diversity gain (DG), and channel capacity loss (CCL), confirm reliable operation. Specific absorption rate (SAR) values are well within international limits (0.558 W/kg at 1 g and 1.24 W/kg at 10 g). Moreover, stable performance is achieved even when operated with a mobile casing. The antenna also demonstrated a data rate of over 25 Gbps for a 15 dB SNR. It shows reliable connectivity delivering >10 Gbps of data over more than 80 m. Thus, the proposed antenna is a strong candidate for next-generation portable wireless devices due to its compactness, simple geometry, and robust performance.

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