Advances in Reconfigurable Antenna Systems Facilitated by Innovative Technologies

© 2013 IEEE. Future fifth generation (5G) wireless platforms will require reconfigurable antenna systems to meet their performance requirements in compact, light-weight, and cost-effective packages. Recent advances in reconfigurable radiating and receiving structures have been enabled by a variety of innovative technology solutions. Examples of reconfigurable partially reflective surface antennas, reconfigurable filtennas, reconfigurable Huygens dipole antennas, and reconfigurable feeding network-enabled antennas are presented and discussed. They represent novel classes of frequency, pattern, polarization, and beam-direction reconfigurable systems realized by the innovative combinations of radiating structures and circuit components

Multipolarization-reconfigurable air-filled substrate integrated waveguide cavity-backed slot antenna

A novel single-feed ultrawideband cavity-backed slot antenna with a reconfigurable polarization capability is demonstrated in substrate-independent air-filled substrate integrated waveguide (AFSIW) technology for Internet-of-Things applications in the [5.15-5.85] GHz frequency band of the unlicensed national information infrastructure. The antenna achieves an ultrawide impedance bandwidth by exploiting a double ring of slots and supports four switchable linear polarization states (+/- 45 degrees, 0 degrees, +45 degrees, and 90 degrees) by leveraging four quartets of p-i-n diodes. By electrically shorting the slots at well-defined positions by these p-i-n diodes, dynamic polarization reconfiguration is achieved by switching their dc bias current, supplied at the antenna feed through an external bias tee and routed from the antenna's back to front cavity plane via the AFSIW sidewalls. This new simple, yet effective, bias network enables the integration of all polarization control electronics inside the antenna cavity to protect them from environmental effects. Finally, measurements prove that the prototype exhibits an overlapping impedance bandwidth of 29%, from 4.85 to 6.45 GHz, and a stable conically shaped radiation pattern across the operating bandwidth with a 3 dB beamwidth of 45 degrees and a peak gain of 6.5 dBi for all four states

A Study on Frequency Reconfigurable Antennas for Applications in Frequency Agile Radio and mm-Wave.

As the current technologies in mobile communications are constantly growing it is becoming a necessity for researchers to investigate and deliver novel, versatile and agile devices providing adaptive performance in order to fulfil the ever changing requirements for communication engineering standards in the next and currently developing generation of mobile communications known as 5G. The current technologies in adaptive antennas have provided optimal numbers using comprehensive technologies that are compatible with the past generations of mobile communications. However, the increasing amounts of data exchanged by mobile devices nowadays require multiple services to be covered by reduced number of devices. In order to overcome this inconvenience, the use of reconfigurable antennas, specifically frequency reconfigurable antennas introduce an adaptive and innovative concept for versatile devices with applications in radio agility that overcomes the limitations of the current devices that are unable to cover multiple services by a single antenna. Two different kinds of frequency reconfigurable antennas are discussed in this work. The design, simulations, manufacture, and measurements for the discussed antennas are developed in this thesis. The first discussed designs are three prototypes of 1×2 triple-slotted antennas with different positions in the board. These boards offered independent frequency tuning using varactor-loaded slots that are electrically tunable by voltages from 0 – 25 V offering a fully tunable frequency range from 0.57 GHz and up to 2.73 GHz. The commented antennas offered independent metrics for frequency response and radiation patterns as well as good agreement between simulations and measurements. Moreover, the three slot antenna prototypes were object of a study in diversity metrics as they present spatial diversity schemes. The simulated and measured diversity parameters observed agreed on optimal numbers for frequencies above 750 MHz for the three prototypes with correlations well below 0.3 and diversity gains near the ideal value of 10 dB which allows reduction of required power in multi-antenna systems and determines its capacity to operate in MIMO systems for 5G. The second kind of antennas discussed in this is a dielectric resonant antenna (DRA) designed to operate at 28 GHz using bioplastics with relatively low dielectric constants and filled by different materials in order to achieve frequency reconfiguration including electrically tunable substances such as graphene oxide covering a frequency range from 26.3 GHZ to 28.3 GHz presenting good agreement between measured and simulated reflection coefficients and radiation patterns

Holographic MIMO Communications: Theoretical Foundations, Enabling Technologies, and Future Directions

Future wireless systems are envisioned to create an endogenously holography-capable, intelligent, and programmable radio propagation environment, that will offer unprecedented capabilities for high spectral and energy efficiency, low latency, and massive connectivity. A potential and promising technology for supporting the expected extreme requirements of the sixth-generation (6G) communication systems is the concept of the holographic multiple-input multiple-output (HMIMO), which will actualize holographic radios with reasonable power consumption and fabrication cost. The HMIMO is facilitated by ultra-thin, extremely large, and nearly continuous surfaces that incorporate reconfigurable and sub-wavelength-spaced antennas and/or metamaterials. Such surfaces comprising dense electromagnetic (EM) excited elements are capable of recording and manipulating impinging fields with utmost flexibility and precision, as well as with reduced cost and power consumption, thereby shaping arbitrary-intended EM waves with high energy efficiency. The powerful EM processing capability of HMIMO opens up the possibility of wireless communications of holographic imaging level, paving the way for signal processing techniques realized in the EM-domain, possibly in conjunction with their digital-domain counterparts. However, in spite of the significant potential, the studies on HMIMO communications are still at an initial stage, its fundamental limits remain to be unveiled, and a certain number of critical technical challenges need to be addressed. In this survey, we present a comprehensive overview of the latest advances in the HMIMO communications paradigm, with a special focus on their physical aspects, their theoretical foundations, as well as the enabling technologies for HMIMO systems. We also compare the HMIMO with existing multi-antenna technologies, especially the massive MIMO, present various...Comment: double column, 58 page

6G Enabled Smart Infrastructure for Sustainable Society: Opportunities, Challenges, and Research Roadmap

The 5G wireless communication network is currently faced with the challenge of limited data speed exacerbated by the proliferation of billions of data-intensive applications. To address this problem, researchers are developing cutting-edge technologies for the envisioned 6G wireless communication standards to satisfy the escalating wireless services demands. Though some of the candidate technologies in the 5G standards will apply to 6G wireless networks, key disruptive technologies that will guarantee the desired quality of physical experience to achieve ubiquitous wireless connectivity are expected in 6G. This article first provides a foundational background on the evolution of different wireless communication standards to have a proper insight into the vision and requirements of 6G. Second, we provide a panoramic view of the enabling technologies proposed to facilitate 6G and introduce emerging 6G applications such as multi-sensory–extended reality, digital replica, and more. Next, the technology-driven challenges, social, psychological, health and commercialization issues posed to actualizing 6G, and the probable solutions to tackle these challenges are discussed extensively. Additionally, we present new use cases of the 6G technology in agriculture, education, media and entertainment, logistics and transportation, and tourism. Furthermore, we discuss the multi-faceted communication capabilities of 6G that will contribute significantly to global sustainability and how 6G will bring about a dramatic change in the business arena. Finally, we highlight the research trends, open research issues, and key take-away lessons for future research exploration in 6G wireless communicatio

Polarization reconfigurable air-filled substrate integrated waveguide cavity-backed slot antenna

The Internet of Things requires highly efficient ultra-wideband antenna systems that yield high performance at low manufacturing cost. Therefore, a novel ultra-wideband circular air-filled substrate-integrated-waveguide (AFSIW) cavity-backed annular slot antenna is proposed that enables straightforward integration into general-purpose materials by means of standard manufacturing techniques. The cavity top plane, serving as antenna aperture, contains two concentric annular slots, both split into two by shorting tabs that create a virtual electric wall. This enables the generation of a TE11; slot even mode in both parts of each annular slot, giving rise to a conical radiation pattern. By exciting two such modes and judiciously positioning their resonance frequencies, all the unlicensed national information infrastructure (U-NII) [5.15-5.85] GHz radio bands are covered. The annular slot antenna is then made polarization reconfigurable through an innovative excitation of the slot modes by replacing the shorting tabs with four pairs of the PIN diodes. These dynamically switch between two orthogonal linear polarizations by changing the dc control current at the antenna RF port through an external bias tee. This simple, yet effective, bias network enables the integration of all polarization control electronics inside the antenna cavity to protect them from environmental effects. A low-cost antenna substrate was realized through standard additive manufacturing in a 3D-printed substrate, while a standard high-frequency laminate was used to implement the upper conducting plane containing the radiating elements and the polarization reconfiguration electronics. The antenna features an impedance bandwidth of 0.93 GHz, a front-to-back ratio of 14 dB, a total antenna effiency higher than 95%, and 4.9 dBi gain for each polarization state

Overview of RIS-Enabled Secure Transmission in 6G Wireless Networks

As sixth-generation (6G) wireless communication networks evolve, privacy concerns are expected due to the transmission of vast amounts of security-sensitive private information. In this context, a reconfigurable intelligent surface (RIS) emerges as a promising technology capable of enhancing transmission efficiency and strengthening information security. This study demonstrates how RISs can play a crucial role in making 6G networks more secure against eavesdropping attacks. We discuss the fundamentals, and standardization aspects of RISs, along with an in-depth analysis of physical-layer security (PLS). Our discussion centers on PLS design using RIS, highlighting aspects like beamforming, resource allocation, artificial noise, and cooperative communications. We also identify the research issues, propose potential solutions, and explore future perspectives. Finally, numerical results are provided to support our discussions and demonstrate the enhanced security enabled by RIS.Comment: Accepted for Digital Communications and Networks(DCN