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In this paper, we analyse the performance of infrastructure-based fixed relay with multi-antenna in cognitive radio. We derive the mathematical expression for detection probability of single cooperative relay system over Rayleigh fading channel. Relay and fusion centre may perform either selection combining or maximal ratio combining of the signals. Effect of number of relay antennas for all four combinations of combining schemes has been analysed and as expected, increase in relay diversity improves the sensing performance. This is because, on installing more number of receiving antennas on the relay, it's participation increases, so the detection performance also improves. In the non-cooperative system also, the performance improves on increasing the diversity order but on the other hand, this increment imposes burden on the fusion centre. Whereas in multi-antenna cooperative relay system, the burden of relay gets transferred on relay node and the fusion centre takes advantage of increased diversity order of relay. For cooperative spectrum sensing, we have used soft decision combining scheme in which secondary users send their test statistics calculated from their local observations. [ABSTRACT FROM AUTHOR]

A 3 × 3 slotted circular Electromagnetic Band gap based Metasurface (SCEBG-MS) has been presented in this article, which enhances the performance of a circularly polarized (CP) patch antenna by improving its impedance bandwidth, axial ratio bandwidth and gain. The proposed antenna is having a low profile of 0.065 λo (λo is the free-space wavelength at center frequency of 6.16 GHz) with ground size selection of 30 × 30 mm. The prototype antenna achieves a measured −10 dB impedance bandwidth of 37% (5.02–7.30 GHz) and measured 3-dB axial ratio bandwidth of 5.9% (5.24–5.56 GHz). Furthermore, the antenna yields a good peak gain of 6.6 dBic in the CP bandwidth which makes it a promising candidate for Wireless Local Area Network (WLAN) applications. Experimental results obtained from the fabricated prototype closely matched with the simulated results. [ABSTRACT FROM AUTHOR]

In this article, a new compact Circularly Polarized Antenna with wide operating bandwidth is proposed. The proposed structure consists of a Modified Circular Split Ring Resonator (MCSRR) as the radiating patch, which is fed by coplanar waveguide and loaded with 2 × 2 closed-ring resonantor (CRR) array on its FR4 epoxy substrate. The dimensions of the antenna are 0.329 λo x 0.329 λo x 0.024 λo (λo stands for the free space wavelength at center frequency of 4.94 GHz).The implementation CRR on modified printed monopole antenna leads to a wide measured impedance bandwidth of 2726 MHz with a peak gain of 5.09dBi and efficiency of 96.3% in the operating bandwidth. A prominent feature of the proposed antenna is that dual 3-dB axial ratio bandwidth of 430 MHz and 670 MHz is observed in the operating band, and thus, making it to be a promising candidate for recent day wireless applications. The simulated results was verified by measuring the characteristics of the fabricated antenna; the obtained results showed a good matching with the simulated results. [ABSTRACT FROM AUTHOR]

In this article, a hexagonal ring electromagnetic band gap (HREBG) structure‐based circularly polarized (CP) slot antenna for improving performance is proposed. The proposed antenna has a compact structure with a low profile of 0.517λo × 0.517λo × 0.055λo (λo stands for the free space wavelength at 5.10 GHz), is coplanar waveguide fed, and comprises of a circular microstrip patch with a T‐shaped slot. An inclined coupling slot loaded feed line is used on the ground for the generation of CP. Furthermore, eight HREBG's are implemented on the substrate to enhance the performance of the antenna, thereby achieving a measured impedance bandwidth of 18%, 3‐dB axial ratio bandwidth of 6.4%, and a peak gain of 5.93 dBi in the operating bandwidth. A close agreement is reached between the experimental results and the simulated results to verify the proposed antenna's performance. [ABSTRACT FROM AUTHOR]

In this article, a new structure comprising of a novel compact slot loaded polarization dependent Electromagnetic Band Gap structure (SLPDEBG), which enhances the performance of circularly polarized rotated square patch antenna by placing SLPDEBG unit cells around it, has been designed. The proposed antenna, having dimensions 0.640 λo x 0.640 λ x 0.0128 λo (λo stands for the free space wavelength at 2.39 GHz), shows that the measured impedance bandwidth and AR bandwidth is 120 MHz and 50 MHz, respectively, with a peak gain of 3.52 dB. Some prominent features of the proposed structure are: front to back ratio of 64, 3 db, beamwidth of 92° at xz-plane and 74° at yz-plane. This prototype antenna finds its application in wireless communication of ISM band. Good performance of the proposed antenna is verified by the close agreement between the simulated and measured results. [ABSTRACT FROM AUTHOR]