Low-profile miniaturized wideband circularly polarized monopole and MIMO antennas using characteristic mode analysis for wireless communication

• Main Authors: Ding, Z., Cao, J., Yu, Junhong, Nasimuddin, Nasimuddin, Chia, M. Y., Fei, S., Wang, H.
• Other Authors: School of Electrical and Electronic Engineering
• Format: Article
• Language: English
• Published: 2024
• Subjects: Engineering; Characteristic angle; Characteristic mode analysis
• Online Access: https://hdl.handle.net/10356/181450
• Institution: Nanyang Technological University

Low-profile miniaturized wideband circularly polarized (CP) monopole and multiple-input-multiple-output (MIMO) antennas using characteristic mode analysis (CMA) are presented. The antennas are constructed with a microstrip feeding line, a slot, and a branch, which positions the transmission line perpendicularly to the branch to achieve CP. The CP characteristic is realized through a characteristic angle (CA) difference of approximately 90° at three mode significance (MS) intersections across four modes. CMA provides both theoretical analysis and design guidance for these antennas. The antennas were fabricated and tested, with dimensions of 0.48λ₀ × 0.48λ₀ × 0.03λ₀ and 0.47λ₀ × 0.47λ₀ × 0.03λ₀, where λ₀ represents the free-space wavelength. Measurements indicate that the monopole antenna achieves a −10 dB impedance bandwidth (IBW) from 3.2 to 8.4 GHz (89.7% relative bandwidth), a 3 dB axial ratio bandwidth (ARBW) from 3.6 to 5.1 GHz (34.5%), and a peak gain of 6.6 dBic. The MIMO antenna has a −10 dB IBW from 3.1 to 8.2 GHz (90.3%), a 3 dB ARBW from 3.2 to 6 GHz (60.9%), and a peak gain of 5.1 dBic. Both antennas feature a low profile, ultra-wideband IBW, broadband ARBW, and miniaturized design, making them suitable for wideband wireless communication applications.