volume | PIER Journals

Abstract

A compact four-port circularly polarized multiple-input multiple-output (CP-MIMO) antenna with a dual-layer architecture is proposed for low-altitude communication applications. In compact MIMO arrays of CP-capable monopole elements, strong mutual coupling makes stable CP radiation difficult to achieve. To address this issue, the proposed antenna uses a lower layer for dual-polarized MIMO generation and an upper layer for polarization conversion. The antenna is fabricated on two FR-4 substrates with an overall size of 0.85λ × 0.85λ × 0.084λ. In the lower layer, a dual-polarized feed backplane (DPFB) forms a ±45° dual-polarized MIMO array with port isolation exceeding 17 dB. In the upper layer, a polarization conversion superstrate (PCS) converts the incident dual-polarized waves into CP radiation. The PCS extends the impedance bandwidth by 36%, from 7.55 to 10.08 GHz, and enables LHCP radiation with a 3 dB AR bandwidth of 8.22-8.89 GHz. A gain enhancement of 48% is also achieved. Measured results verify the design and show good MIMO diversity performance.

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Professor Jingchang Nan

Ms. Siyao Zhao

Dr. Yifei Wang