4×4 Dual-band MIMO antenna with low mutual coupling using a novel structure of neutral line

A 4×4 dual-band MIMO Fractal-PIFA antenna with high isolation is designed and fabricated. The antenna operates at 2.6 GHz and 5 GHz with large bandwidth of 13.4% and 20.4% resprctivrly for wide-band applications in portable terminals. Based on self affinity and lengthened shorting pin of PIFA structure, the single antenna is miniaturized up to nearly 90% comparing to traditional patch one. Being on RO 4350B substrate with the thickness of 1.52 mm, the proposed antenna gets compact size with approximate radiation patch size of 10.8×11mm² and total one of 74×75 mm². To get high isolation between radiation elements of MIMO antenna at so close distance of 3.13 mm from edge to edge, a novel structure of neutral line is presented with equivalent circuit model. The mutual coupling is lower than -20dB for both operating bands. All are simulated based on CST software.