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A novel approach based on the extraordinary transmission is proposed to improve the photovoltaic properties of thin film solar cells. In this approach, a perforated gold film with a periodic array of square holes is embedded inside the absorber layer of the solar cell at an optimum depth. The gold film also serves the purpose of an electrode to take dc output. The transmission of light through the film takes place due to the extraordinary transmission which leads to significant absorption increase in the absorber layer. To achieve the optimal response the periodicity of holes is varied and the corresponding solar cell parameters including short-circuit current and efficiencies are calculated. Here, we report that the increased absorption of solar energy gives almost twofold enhancement in short-circuit current density and optical conversion efficiency of the solar cell. The investigation is performed using finite difference time domain (FDTD) computational method.

In this paper, a compact planar CPW-fed antenna operating over the four frequency bands is proposed for RF energy harvesting applications. The proposed antenna includes five radiating elements and a stepped ground plane, occupies a total area of 48 × 42 mm2. By virtue of stepped ground plane, the antenna exhibits a better impedance match compared to the antenna with the full ground plane. The measured | S 11 | better than −10 dB is obtained at the frequency bands GSM-900, GSM-1800, Wi-Fi 2.1 GHz and Bluetooth (2.4 GHz), showing its suitability for RF energy harvesting application. For this to be feasible, the developed antenna is matched with the rectifier at four desired frequencies using a compact quad-band matching network. The merit of the proposed rectifier circuit is it can be extended for n number of frequency the band by using only 3n-1 number of lumped elements. To validate the design method experimentally, a prototype of a dual-band rectifier is also fabricated. The measured result demonstrates that the proposed dual-band rectifier circuit achieved the peak efficiency of 42 % and 38 % for 0.9 and 2.1 GHz, respectively at a load impedance of 4.7 k Ω .

This paper presents a compact active integrated antenna (AIA) comprising of class-A power amplifier (PA) and stepped impedance planar inverted-F antenna (PIFA). In the proposed design, a common ground is used for both PA and PIFA, resulting a compact antenna of size 0.14λ 0 × 0.11λ 0 × 0.01λ 0 (λ 0 is free space wavelength at 0.85 GHz). Moreover, it is demonstrated that by using the stepped impedance radiator the operating frequency of the active PIFA is shifted down from its natural resonant frequency of 1.36 GHz to 0.85 GHz, offering an extensive size reduction of 80%. This active integration increases the passive antenna gain through the effective loading of the antenna to the power amplifier. The measured result indicates that the active and passive antennas achieved the gain of 15.7 dB and 3.81 dBi, respectively after the integration. In addition, the maximum SAR value of antenna is found to be 0.64 W/kg.

A novel high gain and broadband hybrid dielectric resonator antenna (DRA) is designed and experimentally validated. To obtain the wide impedance bandwidth, the proposed antenna geometry combines the dielectric resonator antenna and an underlying slot with a narrow rectangular notch, which effectively broadens the impedance bandwidth by merging the resonances of the slot and DRA. An inverted T-shaped feed line is used to excite both antennas, simultaneously. It supports amalgamation of different resonant modes of the both, DRA and slot antenna. The measured results show that the proposed antenna offers an impedance bandwidth of 120% from 1.67 to 6.7 GHz. The antenna gain is next enhanced by a reflector placed below the antenna at an optimum distance. On engineering the height and dimension of this reflector the antenna gain is improved from 2.2 dBi to 8.7 dBi at 1.7 GHz. Finally, antenna operation is attested experimentally with a rectifier circuit in the frequency range of 1.8–3.6 GHz, where various strong radio signals are freely available for RF energy harvesting. The measured maximum efficiency of the rectifier and rectenna circuit were found to be 74.4% and 61.4%, respectively.

In this work, a frequency reconfigurable MIMO antenna for 4G and early 5G applications is presented. The MIMO antenna design consists an array of two radiating/receiving elements positioned diagonally opposite to each other for better isolation (>12 dB) and pattern diversity. Each antenna element in MIMO array has a single module consisting two meandered radiating arms which could be connected or disconnected to the 50 Ω feedline electronically using two PIN diodes to operate in two switchable frequency bands/modes, 2.4 GHz or 3.5 GHz assigned for 4G/LTE and early 5G/Sub-6 GHz wireless communication technologies, respectively. The length of each radiating arm is around half-wavelength at operating frequency of interest (2.4 GHz or 3.5 GHz). The overall size of the MIMO antenna system is 120 mm × 60 mm × 1.52 mm. The proposed MIMO antenna configuration provides a 28.81% FBW (2.0 GHz to 2.7 GHz) and 49.7% FBW (2.57 GHz to 4.27 GHz) in both the resonance modes, respectively. The measured antenna gain values in two switchable frequency modes are 3.7 dBi and 4.2 dBi, respectively with overall efficiency > 60%. A low envelope correlation coefficient (0.0056 at 2.4 GHz and 0.0009 at 3.5 GHz) is achieved. Furthermore, the SAR and hand mode analysis is carried out to verify the performance of the MIMO antenna for mobile handset. The measured ergodic channel capacity of the MIMO antenna has been achieved more than 10b/s/Hz for both the mode.