Investigation of 2-port UWB MIMO diversity antenna design using characteristics mode analysis

Abstract

In this research work, a 2-port UWB MIMO diversity antenna is designed to operate from 2.7 to 10.5 GHz with −10 dB impedance bandwidth of 118.18%. The proposed design has a total size of 0.57λ2.7×0.28λ2.7 (λ2.7 is lowest operating wave-length) consists of bi-planar printed fractal radiators whose feeds are contorted in geometry and are diametrically-fed. Characteristics mode analysis (CMA) is introduced to investigate antenna design, feeding technique and modal current distributions. The analysis includes study of modal dynamics, resonance mechanism, bandwidth potentials and modal radiation quality factor. The port-isolation is ⩾−15 dB when ground plane is truncated by rectangular slots via ellipsoid slot. With an end-connected ground thin neutralization lines, mutual coupling is further reduced by 7.5 dB (>−22.5 dB, measured). The diversity performance metrics are evaluated from ECC, CCL, DG, multiplexing efficiency, MEG and TARC. ECC is low <0.17 (from far-field magnitudes) and mean effective gain for both ports are |MEG| < 3 dB with MEG1MEG2 ≊ 1, which is serviceable for UWB multi-standard mobile/wireless/sensor ad-hoc diversity systems. An equivalent circuit model is also designed and the prototype of antenna is fabricated and measured to validate its performance.