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A compact four-element UWB MIMO antenna is proposed and its characteristics are investigated. The proposed antenna has a hexagon molecule-shaped fractal structure as its radiating element. The antenna elements are placed orthogonally to each other in order to yield good isolation, without any additional decoupling structure. The band rejection in WLAN band is attained by etching a C-shaped slot on each radiating element. The antenna has a compact size of 40 × 40 × 1.6 mm 3 and exhibits stable omni-directional radiation pattern. In addition, it shows an acceptable impedance bandwidth (S 11 < −10 dB) in the range 2.4-10.6 GHz with an isolation better than −20 dB over the UWB range. The performance of the proposed antenna is calculated in terms of antenna characteristics and MIMO parameters. The isolation level in-between the elements is found to be reasonable for MIMO application. The simulated and measured results are in good accord which makes the antenna a suitable candidate for massive MIMO and high-density packaging applications.

In this study, a two‐element multiple‐input–multiple‐output (MIMO) antenna with heptaband characteristics is proposed. The total size of the proposed antenna is 82 × 40 × 0.8 mm3. The geometry of the radiating element is derived from a hybrid Quadric–Koch island fractal for size miniaturisation. The antenna operates at the bands of 0.95–1.02 GHz (GSM 900), 1.73–1.79 GHz (GSM 1800), 2.68–2.85 GHz (LTE‐A), 3.66–3.7 GHz [ultra‐wideband (UWB)], 4.20–4.40 GHz (UWB), 5.50–5.65 GHz [worldwide interoperability for microwave access/high‐performance radio local area network] and 5.93–6.13 GHz (UWB). The spacing between the two radiating elements is maintained at 5 mm. The proposed heptaband swastik arm MIMO antenna exhibits an S11 ≤ −6 dB and S21 ≤ −17 dB over the entire bands of operation. It provides high isolation without requiring any additional structures. The antenna also offers stable radiation characteristics with circular polarisation at the operating bands of 3.66–3.7 GHz and 5.93–6.13 GHz and linear polarisation at 0.95–1.02 GHz, 1.73–1.79 GHz, 2.68–2.85 GHz, 4.20–4.40 GHz and 5.50–5.65 GHz bands. The diversity performance of the antenna is studied in terms of the envelope correlation coefficient which is <0.05, and capacity loss which is <0.5 bits/s/Hz at all the operating frequencies, making it suitable for use in fifth generation communication systems incorporating the existing bands.

Table 3 presents the comparison of the proposed parasitic patch array antenna in different literatures. 4,10,11 The parameters including number of layer and patch, the size of the antenna, the impedance bandwidth and the peak gain are taken into account. From the table, we can see that the 5 3 5 CPPS-based array antenna has the advantages of simple structure, wide bandwidth and high gain. | C ONCL US I ONThis article presents a design of a 5 3 5 array antenna based on coplanar parasitic patch structure. A feed network is formed via dual ports stimulating the two center patches and resonance branches between the central patches and the parasitic patches. The designed array antenna has a simple structure, high gain, strong orientation, and low crosspolarization. It has good reference value to the array antenna research. Therefore, it has important applications in communication and radar system.