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A compact 5.5 GHz band‐notched ultra‐wideband (UWB) 2‐element antenna with high isolation for multiple‐input multiple‐output (MIMO) portable wireless devices in wireless personal area network (WPAN) application is proposed. The MIMO antenna is designed for 3.1–10.6 GHz range on Neltec substrate with compact dimension of 43 × 20 mm2 and is tested experimentally. For the rejection band at 5.5 GHz, a slot of length 1.0 λ is etched into the radiator. Simple structure, i.e., receded steps at ground are used to improve isolation by 3 dB between two UWB antennas. The simulated and measured results show |S11| ≤ −10 dB and |S21| ≤ −20 dB in most of the frequency range excluding the reject band at 5.5 GHz in UWB range. The measured, simulated and calculated results show that the proposed UWB MIMO antenna is a good candidate for UWB MIMO systems. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1390–1394, 2016

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In this work, a Tri-Band frequency reconfigurable antenna for LTE (Long Term Evolution)/WiFi (Wireless Fidelity)/ITS (Intelligent Transportation Systems) applications is presented. The proposed design consists of a wine glass shaped slotted radiating patch along with a switchable rectangular ring type slot on the ground plane. This structure operates in three different states viz. state-1, state-2, and state-3 at 4.5 GHz (LTE band), 5.9 GHz (ITS band), and 3.8 GHz (LTE band)/5 GHz (Wi-Fi band), respectively, with an overall compact size of 30 × 30 × 0.762 mm 3 . Multi-band resonances are obtained by incorporating slots in the main radiating element and ground plane. Moreover, switching among these bands is achieved by placing two PIN diodes at optimized positions on the rectangular ring slot in the ground plane. For the proposed design, good agreement between simulated and measured results is obtained in all the three operating states of the design, which makes it suitable for compact reconfigurable systems.

A very compact 2 3 2 and 4 3 4 ultra wide band (UWB) multiple input multiple output (MIMO) antenna array with high isolation and polarization/pattern diversity are proposed in this letter. The compact size of antenna with orthogonally polarized elements help in achieving high isolation between elements of the arrays without using any decoupling circuit while maintaining its overall size very compact. The monopole UWB antenna prototype has compact size of 14 3 14 mm 2 and enlarged to 2 3 2 array having size of 14 3 31 mm 2 and 4 3 4 array having overall size of 31 3 31 mm 2 . The proposed designs have been fabricated and tested. Measured isolations |S 21 | are 225 dB and 220 dB for 2 3 2 and 4 3 4 arrays, respectively. However, impedance bandwidth |S 11 | is 210 dB for both arrays in the range from 3.6 to 10.6 GHz. The simulated, measured and calculated result shows good agreement for its impedance matching, isolation and dual polarization characteristics. Dual polarization improves its diversity performance and compact size improves its spatial multiplexing.mutual coupling, polarization/pattern diversity, UWB MIMO | I NT ROD UCTI ONMIMO technology has been drawing a lot of attention in modern wireless communication systems, because it satisfies the demand of high data rate system by using multiple antennas both at Tx and Rx with reduced multipath fading and increasing reliability.1 On the other hand, FCC (federal communication commission) has announced the range of frequency 3.1-10.6 GHz as unlicensed ultra wide band (UWB). UWB technology is promising for short distance communication because it provides high data rate with low power spectral density, but has issues of fading and reliability. Most of the papers mentioned above are reported with 2 3 2 configurations but to further enhance data capacity and signal reliability at once, more number of antennas are needed to deploy in a system. Some papers report 4 3 4 UWB MIMO antenna 8,10-12 but only few are feasible to use in a compact portable wireless devices due to its size constraints. To solve above mentioned issue, this article reports a very compact planner antenna with orthogonally polarized elements to improve isolation. The UWB MIMO antenna array covers the range from 3.6 to 10.6 GHz. The 2 3 2 array has compact size of 14 3 31 5 434 mm 2 which is about 42, 62, 59, and 24% smaller than the UWB MIMO antenna reported in Ref. [4,6,7], and [9], respectively, whereas the 4 3 4 array has compact size of 31 3 315 961 mm 2 which is about 58, 61, 53, and 52% smaller than the UWB MIMO antennas in Refs. 8, 10-12, respectively. The compact size of single UWB element helps in attaining very compact 2 3 2 and 4 3 4 MIMO arrays which are free from any decoupling and matching circuits. The simulated and measured results show that the proposed UWB MIMO antenna is good candidate for compact portable wireless devices such as USB dongle and others. | S I NG LE EL EME NT UW B M I MO A NTEN NAThe proposed UWB MIMO antenna is simulated in CST Microwave Studio simulator....