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This paper presents an innovative technique to synthesize a virtual antenna array (VAA) that consumes less energy than conventional antenna arrays that are used in mobile communications systems. We have shown that for a specific spectral efficiency a wireless system using the proposed virtual antenna array consumes significantly less energy per bit (∼3 dB) than a wireless system using a conventional multiple-input multiple-output (MIMO) array. This means the adoption of the proposed VAA technology in smartphones, iPad, Tablets and even base-stations should significantly reduce the carbon footprint of wireless systems. The proposed VAA is realized by employing a pair of linear antenna arrays that are placed in an orthogonal configuration relative to each other. This orthogonal arrangement ensures the radiation is circularly polarized. The size of the standard radiating elements constituting the VAA were miniaturized using the topology optimization method. The design of the VAA incorporates substrate integrated waveguide (SIW) and metasurface technologies. The function of SIW in the design was twofold, namely, to reduce energy loss in the substrate on which the VAA is implemented, and secondly to mitigate unwanted electromagnetic interactions between the neighboring radiating elements and thereby enhancing isolation which otherwise would degrade the radiation characteristics of the array. Metasurface technology served to effectively increase the effective aperture of the array with no impact on the footprint of the array. The consequence of SIW and metasurface technologies was improvement in the gain and radiation efficiency of the array. The proposed four orthogonal 4-element VAA covers the entire sub-5 GHz frequency range, and it radiates bidirectional in the azimuth plane and omni-directional in the elevation plane. Moreover, it is relatively easy to design and fabricate. The proposed VAA has dimensions of 0.96λ0 × 0.96λ0 × 0.0016λ0 at mid-band frequency of 3 GHz. VAA has a measured gain of 25 dBi and radiates with 90% efficiency. The average isolation between the linear arrays constituting the virtual array is better than 27 dB. Dr. Mohammad Alibakhshikenari acknowledges support from the CONEX-Plus programme funded by Universidad Carlos III de Madrid and the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 801538. The authors also extend their appreciation to the Deputyship for Research & Innovation, Ministry of Education in Saudi Arabia for funding this research work through the project number 223202. Additionally, this work was supported by Ministerio de Ciencia, Innovación y Universidades, Gobierno de España (Agencia Estatal de Investigación, Fondo Europeo de Desarrollo Regional-FEDER-, European Union) under the research grant PID2021-127409OB-C31 CONDOR.

Design of a novel triband bandpass filter is presented for wireless communications systems. The filter is based on inter-coupled stepped impedance resonators and inter-digitally coupled to the input/output ports. The configuration of the filter circuit consists of open-loop resonators that are electromagnetically coupled to each other using inverted tee-shaped open stubs. The intrinsic characteristics of filter structure generates five transmission zeros that results in triband bandpass response exhibiting sharp selectivity, high inter-band isolation and a wide out of band rejection. Unlike other triband filters reported in literature the proposed single layer filter does not require any short-circuited plated through hole which reduces fabrication complexity and therefore production cost. Moreover, the triband structure can be configured to provide passbands with identical 3-dB fractional bandwidth and whose center frequency can be equally spaced. In the proposed prototype design presented here the passband frequencies are set to 3.6 GHz, 4.6 GHz and 5.6 GHz that corresponds to WiMAX, 5G and WLAN applications. The consequence of employing open-circuited transmission lines in the design results in a relatively large structure, which can be overcome by employing higher dielectric constant substrate. The triband filter was designed to achieve identical 3-dB fractional bandwidth of 11.9%. Measured results confirm inter-band isolation better than 30-dB. The theoretical model is consistent with the measured results.

This paper presents the design of a microstrip ultra-wideband (UWB) bandpass filter that exhibits desirable characteristics of low-loss, high selectivity, wide stopband and high out-of-band rejection at room temperature. These characteristics are normally achieved with high temperature superconductor filters that require cryogenic cooling. The design of the proposed filter was realized by exciting multiple resonant modes in a unique Z-shaped microstrip resonator. The admittance of the filter configuration can be tuned prior to fabrication to adjust its center frequency by about 11.5% without affecting the profile of the bandpass response however this can have an impact of the loss. The proposed configuration allows adjustment of the upper and lower transmission zeros defining the bandpass response by 20.5% and 11.4%, respectively, without degrading the overall filter response. The low-loss quasi-elliptic function UWB bandpass filter design was fabricated on a commercially available dielectric substrate using standard PCB technology and its performance verified. The fabricated filter exhibits insertion-loss of 0.68 dB and return-loss better than 17 dB.

Robotic manipulators have a wide range of applications in many sectors from automation to medical surgery. Since decades, researchers and developers have been proposing creative designs in leveraging specific applications or to demonstrate proof of concepts in bespoke scenarios. \ud \ud This paper presents a novel smart, secure and sustainable framework for the design of a 3D printed robotic hand. The smart robotic hand, consisting of two elements: i) a user-wearable glove and ii) a mechanical hand, is a seamless entity in which the movement of the mechanical hand is controlled by the user-wearable glove. A real-time communication between the glove (server) and the mechanical hand (client) is facilitated through a secure wireless client-server model running on a commercially available microcontroller making it light-weight and cost-effective. In order to promote sustainable 3D printing, a conscious decision was taken to use recyclable and biodegradable Polylactic acid (PLA) based wood filament for the casing of the mechanical hand as well a cotton and linen based material for the user glove.