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Abstract-A very compact triple band-notched multiple input multiple output antenna (MIMO) for ultra-wideband (UWB) communications is fabricated on an FR4 dielectric substrate having the overall size of 18 × 21 × 0.8 mm 3 . The proposed antenna consists of two rectangular metal monopoles which are excited by 50-Ω microstrip lines on top of a substrate, and a common protrude ground is at the bottom. To achieve low mutual coupling between radiating elements, a T-shaped stub is protruded from the ground plane. By etching two C-shaped slots on the radiating patches, band-notched functions at 5.15-6 GHz and 7.8-8.4 GHz are obtained. The third notch band from 3.3-3.7 GHz is realized by adding Ushaped metal strips to the ground. The measured and simulated results demonstrate that the proposed antenna offers good impedance bandwidth of |S 11 | ≤ −10 dB from 2.8-12.2 GHz covering whole UWB band except at the designed notch bands, while giving less mutual coupling (|S 21 |) of lower than −25 dB in the whole UWB band. The measured envelope correlation coefficient (ECC < 0.013), nearly constant gain and stable radiation patterns show that the proposed MIMO antenna is an appropriate candidate for portable UWB systems.

Purpose Microstrip patch antenna is generally used for several communication purposes particularly in the military and civilian applications. Even though several techniques have been made numerous achievements in several fields, some systems require additional improvements to meet few challenges. Yet, they require application-specific improvement for optimally designing microstrip patch antenna. The paper aims to discuss these issues. Design/methodology/approach This paper intends to adopt an advanced meta-heuristic search algorithm called as grey wolf optimization (GWO), which is said to be inspired by the hunting behaviour of grey wolves, for the design of patch antenna parameters. The searching for the optimal design of the antenna is paced up using the opposition-based solution search. Moreover, the proposed model derives a nonlinear objective model to aid the design of the solution space of antenna parameters. After executing the simulation model, this paper compares the performance of the proposed GWO-based microstrip patch antenna with several conventional models. Findings The gain of the proposed model is 27.05 per cent better than WOAD, 2.07 per cent better than AAD, 15.80 per cent better than GAD, 17.49 per cent better than PSAD and 3.77 per cent better than GWAD model. Thus, it has proved that the proposed antenna model has attained high gain, leads to cause superior performance. Originality/value This paper presents a technique for designing the microstrip patch antenna, using the proposed GWO algorithm. This is the first work utilizes GWO-based optimization for microstrip patch antenna.

Massive MIMO has gained much attention with the increase in the high speed data communication. The problem of peak-to-average power ratio (PAPR) is considered, the detrimental aspects in OFDM based massive multiple-input multiple-output (MIMO) downlink systems. The previous works done in reduction of PAPR problem using convex optimization are computationally inefficient. We considered Bayesian approach to mitigate PAPR by utilizing the redundant degrees of freedom (DOF) of the transmit array, which effectively reduced the level of PAPR. The performance or numerical results indicate the applied algorithm achieved a good improvement over the existing techniques in terms of the PAPR reduction.

The current and future wireless communication systems demand for higher data rates, enhanced quality of service and more channel capacity. Since Federal Communications Commission (FCC) allocated the unlicensed frequency spectrum from 3.1 to 10.6 GHz for commercial applications in the year 2002, Ultra-Wideband (UWB) technology has attained considerable attention because of its inherent features like high data rate, more channel capacity, extremely less power consumption and low cost. However, for UWB systems, multipath fading and frequency interference are the two significant issues that requires further investigation. In recent times, Multiple Input Multiple Output (MIMO) technology has gained much attention in wireless communication as it exploits multipath to increase the communication range and link quality. Thus, MIMO technology is a promising solution for mitigating multipath fading in UWB system. However, accommodating multiple antennas with less mutual coupling between them in portable devices is always a challenging task for antenna designers. UWB system could easily interfere with existing narrowband communication system such as Wireless Local Area Network (WLAN). So, the design of an ultra-wideband antenna with integrated frequency notching function is a good solution to suppress the frequency interference and to reduce the complexity of the UWB system instead of using a conventional filter. In this chapter, compact isolation-enhanced planar UWB-MIMO antenna with single band-notched characteristics is presented.

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