A compact flexible four-element dual-band antenna using a unique defective ground decoupling structure for Sub-6 GHz wearable applications

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A compact wearable four-element dual-band antenna with good isolation is presented here. The antenna constitutes of a circular monopole with slits and slots incorporated into it to generate dual-band function, and a unique defected ground structure (DGS) with vertical stubs to neutralize coupling current and enhance isolation. The proposed antenna has a dimension of 62 × 52 × 0.25 mm3, bandwidth of 3.8–4.43 GHz (15.31%) and 5.25–6.3 GHz (18.18%), and 5.2 dBi peak gain. The specific absorption rate (SAR) analysis in W/kg for 1/10 g tissue exhibits values of 0.877/0.356 at 4.1 GHz and 0.309/0.105 at 5.3 GHz respectively. The antenna radiation characteristics are analysed using characteristic mode analysis. Furthermore, the diversity parameters are investigated, and the antenna exhibits relatively good results with envelope correlation coefficient (ECC) < 0.02, diversity gain (DG) > 9.99 dB, total active reflection coefficient (TARC) < −10 dB, mean effective gain (MEG) ratio ∼0 dB, multiplexing efficiency (ME) < −0.5, and channel capacity loss (CCL) < 0.3 bps/Hz, indicating its suitability for real-time MIMO applications.