A compact four element multi-band multi-input multi-output (MIMO) antenna system for 4G/5G and IoT applications is presented in this paper. The proposed antenna is developed using the theory of characteristic modes helping in systematic design of MIMO antenna system. It consists of four L-shaped planar inverted-F antenna (PIFA) elements each operating at 3.5, 12.5, and 17 GHz bands with the bandwidth of 359 MHz, 1 GHz, and more than 3.7 GHz, respectively. The proposed antenna system is suitable for both 4G/5G and internet of things devices as it shows the satisfactory MIMO system performance. Good isolation characteristics are observed by implementing complimentary Metamaterial structure on the ground plane resulting in isolation level lower than −21 dB between the antenna elements. The proposed antenna is fabricated and experimental results are also presented and discussed.
K E Y W O R D S5G, IoT, multi-input multi-output, planar inverted-F antenna, theory of characteristic modes
The design of a three-port radiating structure, integrating wide and narrow band antennas for cognitive radio applications, is presented. It consists of a UWB antenna for spectrum sensing and two narrow band antennas for wireless communication integrated on the same substrate. The UWB antenna covers the complete UWB spectrum (3.1 GHz to 10.6 GHz) approved by FCC. In the two narrow band antennas, each antenna presents dual bands. In particular, the first narrowband antenna resonates at 6.5 GHz, covering the frequency band between 6.36 GHz and 6.63 GHz, and at 9 GHz, covering the frequency band between 8.78 GHz and 9.23 GHz, presenting minimum return loss values of 28.3 dB at 6.5 GHz and 20.5 dB at 9 GHz, respectively. Similarly, the second one resonates at 7.5 GHz, covering the frequency band between 7.33 GHz and 7.7 GHz, and at 9.5 GHz, covering the frequency band between 9.23 GHz and 9.82 GHz, presenting minimum return loss values of 19.6 dB at 7.5 GHz and 28.8 dB at 9.5 GHz, respectively. Isolation among the three antennas is less than −20 dB over the UWB frequency spectrum. These antennas are realized on a FR4 substrate of dimensions 30 mm × 30 mm × 1.6 mm. Experimental results show a good agreement between the simulated and measured results.
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