Dual-Band and Dual-Collinear-Polarization Self-Decoupling of MIMO Slot Antenna by Employing Nonuniform Shared Radiators

A novel multiple-input–multiple-output (MIMO) slot antenna with dual-band self-decoupling characteristics is proposed. The operating principle of the proposed method is to obtain the proper equivalent characteristic impedance and proper equivalent electrical length by adjusting the width of the shared radiators. The radiators of the initial antenna consist of only two nested square ring slots, and they are widened by multiple structures to form the nonuniform radiators in the proposed antenna. It can be coupled fed by four microstrip lines, respectively, creating the dual collinear polarization. The initial antenna operates at 1.3–1.6 GHz in the low band (LB) while at 3.6–3.83 GHz in the high band (HB). The isolation ranges from 7–10 dB in LB and 10–14 dB in HB. The proposed antenna ranges from 1.20 to 1.88 GHz and from 3.52 to 3.90 GHz, and the isolations are improved to over 30 dB in LB and over 65 dB in HB, respectively. The nonuniform slot radiators have both decoupling and matching functions without additional components. The proposed antenna has the advantages of wideband, compact and high isolation.