Combined Antenna Research Articles

Amine Functionalization Within Hierarchically‐Porous Zeotype Framework for Plasmonic Catalysis over PdAu Nanoparticles

AbstractPlasmonic catalysis has revealed improved product yield and selectivity in various chemical transformation reactions over the past decade. In this report, the effect of tertiary amine (‐NR3) functionalization on the surface of hierarchically‐porous zeotype (HP‐AlPO‐5) materials to enhance the plasmon‐mediated catalysis, utilizing a combination of the plasmonic antenna (Au) and catalytic reactor (Pd) nanoparticles (NPs) was investigated. The catalysts have been characterized using enhanced techniques such as HAADF‐STEM, FT‐EXAFS, and probe‐based FT‐IR to reveal the proximity and interaction between bimetallic NPs, and thermal stability of amines in the presence of Au or PdAu NPs. Interestingly, a four‐fold enhancement in the Suzuki‐Miyaura coupling reaction product yield was obtained over PdAu/HP‐AlPO‐5‐NR3 when compared with the analogous plasmonic catalyst with no amine functionalization under visible light irradiation. A range of amines were functionalized and their influence in the nucleation, uniform growth and stabilization of catalytic active site (Pd) and formation of electron‐rich species under visible light irradiation has also been investigated. The presence of tertiary amine in the nanostructured catalyst enhanced the turnover number (TON) significantly under light irradiation conditions in comparison to dark conditions. This study provides an enriched understanding of plasmon‐driven chemistry, where the maximized reaction rate enhancement requires the existence of active metal species and the formation of electron‐enriched species under light irradiation conditions.

Ultraviolet Nanophotonics Enables Autofluorescence Correlation Spectroscopy on Label-Free Proteins with a Single Tryptophan.

Using the ultraviolet autofluorescence of tryptophan amino acids offers fascinating perspectives to study single proteins without the drawbacks of fluorescence labeling. However, the low autofluorescence signals have so far limited the UV detection to large proteins containing several tens of tryptophan residues. This limit is not compatible with the vast majority of proteins which contain only a few tryptophans. Here we push the sensitivity of label-free ultraviolet fluorescence correlation spectroscopy (UV-FCS) down to the single tryptophan level. Our results show how the combination of nanophotonic plasmonic antennas, antioxidants, and background reduction techniques can improve the signal-to-background ratio by over an order of magnitude and enable UV-FCS on thermonuclease proteins with a single tryptophan residue. This sensitivity breakthrough unlocks the applicability of UV-FCS technique to a broad library of label-free proteins.

92 Mb/s Fat-Intrabody Communication (Fat-IBC) With Low-Cost WLAN Hardware.

The human subcutaneous fat layer, skin and muscle together act as a waveguide for microwave transmissions and provide a low-loss communication medium for implantable and wearable body area networks (BAN). In this work, fat-intrabody communication (Fat-IBC) as a human body-centric wireless communication link is explored. To reach a target 64 Mb/s inbody communication, wireless LAN in the 2.4 GHz band was tested using low-cost Raspberry Pi single-board computers. The link was characterized using scattering parameters, bit error rate (BER) for different modulation schemes, and IEEE 802.11n wireless communication using inbody (implanted) and onbody (on the skin) antenna combinations. The human body was emulated by phantoms of different lengths. All measurements were done in a shielded chamber to isolate the phantoms from external interference and to suppress unwanted transmission paths. The BER measurements show that, except when using dual on-body antennas with longer phantoms, the Fat-IBC link is very linear and can handle modulations as complex as 512-QAM without any significant degradation of the BER. For all antenna combinations and phantoms lengths, link speeds of 92 Mb/s were achieved using 40 MHz bandwidth provided by the IEEE 802.11n standard in the 2.4 GHz band. This speed is most likely limited by the used radio circuits, not the Fat-IBC link. The results show that Fat-IBC, using low-cost off-the-shelf hardware and established IEEE 802.11 wireless communication, can achieve high-speed data communication within the body. The obtained data rate is among the fastest measured with intrabody communication.

AMC-Based Low-Profile Dual-Band Slotted Patch Antenna for IoT Devices in the Healthcare System

An artificial magnetic conductor (AMC)-based patch antenna with a low profile is developed for wireless devices in IoT-based healthcare systems. The proposed antenna comprises two pairs of circular-shaped patches with circular-shaped slots and a dual-band 4 × 4 array of AMC reflectors with two zero-degree reflection responses to enhance the antenna's radiation performance. For the 2.45 GHz ISM and 5.4 GHz WLAN bands, the patch antenna has dimensions of 0.44λ0 × 0.52λ0 × 0.013λ0, with partial ground structures to improve radiation characteristics. Following that, a unique dual-band symmetrical AMC unit cell with dimensions of 22 × 22 × 1.6 mm3 is developed. There is a gap of 15 mm between the antenna and the AMC surface. The antenna is supported by a 4 × 4 AMC array that has a total dimension of 0.72λ0 × 0.72λ0 × 0.15λ0. The reflection coefficient values of less than − 10 dB in the 1.7–2.5 and 5.1–5.6 GHz bands, with a bandwidth percentage of 38 and 9.3%, respectively. The antenna's gains were 7.2 and 4 dBi inside the bands. Furthermore, the Specific Absorption Rate (SAR) value did not match the WHO's safety and health guidelines. The issue was solved by including an AMC surface in the proposed antenna. At 2.45 and 5.4 GHz, SAR values of 0.58 and 1.04 W/Kg were measured. Vector network analyser and anechoic chamber were used to test the performance of antenna and AMC surface prototypes. There is a substantial agreement among measured and simulated parameters of an antenna. Consequently, the developed antenna combination with the AMC structure is suited for wireless devices in ISM and WLAN bands, often used in IoT-based healthcare systems.

Wideband to narrowband/dual band characteristics of monopole antenna using frequency selective surfaces

SummaryA monopole antenna having desirable transmission characteristics with high gain is proposed. The monopole antenna comprises 45° tilted square shaped patch and modified rectangular metallic ground plane on FR4 dielectric substrate. The proposed monopole antenna operates from 2.6 GHz to 9.7 GHz with maximum peak gain of 2.3 dBi. Now, a dual‐layer aperture‐type FSS is designed having a passband from 5.9 GHz to 9.2 GHz and incorporated with the proposed monopole antenna. Thus, the combination only covers the selective frequency band from 5.5 GHz to 8.7 GHz with a stable gain of around 5 dBi. Second, another FSS is designed, which has one stop‐band from 4.1 GHz to 5.4 GHz and two passbands on the both sides of this stop‐band. This combination does not work from 4.1 GHz to 5.5 GHz but covers dual band from 2.48 GHz to 3.3 GHz with a peak gain of 5 dBi and 5.5 GHz to 10 GHz with a peak gain of 5.5 dBi. Therefore, without modifying the antenna design, any tunable transmission band can be achieved by the proposed combination. The proposed antenna and FSS combination structure may be suitable for military wireless applications for its band selection characteristics.

Efficacy of Environics Color Slides in Detecting the Color Deficiency and Healing

Chromotherapy, also called Color Therapy or Visible Range Radiation Therapy, is a non-pharmacological therapeutic modality that uses various wavelengths of electromagnetic radiation from within the visible spectrum (colors).
 Methods & Materials: The study was performed on 65 healthy participants from SGT University, Gurgaon, India. Full, free, and voluntary informed consent was obtained from all subjects and/or their legal guardian(s). Colour deficiency was diagnosed with the help of Environics Colour Slides and an Instrument called Lecher Antenna which works on the principle of resonance. The diagnosis results obtained from color slides and Lecher Antenna, (SBJ International, PARIS) were compared with the results obtained from the Es- Teck Complex, (LD Technology™, US) an FDA-approved Medical Software and Machine.
 Results: It was observed that 86.11% of participants showed improvement in their health conditions after using the Environics Colour Slides for the period specified during the diagnosis. It was also observed that there was an 87.69% correlation between the findings of the Environics Colour Slides / Lecher Antenna combination and the ES-Teck Medical Software in identifying the health condition of the participants.
 Conclusion: Chromotherapy will greatly benefit from this evidence base and help propagate this alternative treatment modality for the safe, and non-pharmacological treatment of many diseases [5].

Machine Learning Models Applied to a GNSS Sensor Network for Automated Bridge Anomaly Detection

Structural health monitoring (SHM) based on global navigation satellite systems (GNSS) is an interesting solution to provide absolute positions at different locations of a structure in a global reference frame. In particular, low-cost GNSS stations for large-scale bridge monitoring have gained increasing attention these last years because recent experiments showed the ability to achieve a subcentimeter accuracy for continuous monitoring with adequate combinations of antennas and receivers. Technical solutions now allow displacement monitoring of long bridges with a cost-effective deployment of GNSS sensing networks. In particular, the redundancy of observations within the GNSS network with various levels of correlations between the GNSS time series makes such monitoring solution a good candidate for anomaly detection based on machine learning models, using several predictive models for each sensor (based on environmental conditions, or other sensors as input data). This strategy is investigated in this paper based on GNSS time series, and an anomaly indicator is proposed to detect and locate anomalous structural behavior. The proposed concepts are applied to a cable-stayed bridge for illustration, and the comparison between multiple tools highlights recurrent neural networks (RNN) as an effective regression tool. Coupling this tool with the proposed anomaly detection strategy enables one to identify and localize both real and simulated anomalies in the considered data set.

Design Space Exploration of Antenna Impedance and On-Chip Rectifier for Microwave Wireless Power Transfer

This paper discusses a design methodology to efficiently determine the best combination of rectenna (rectifier and antenna) to minimize the input power under a given output condition for microwave wireless power transfer (MWPT) without any other external components, such as a matching network, for cost reduction. A linearized equivalent circuit model is expanded upon to include the microstrip line connecting the antenna and rectifier. Based on the model, the design flow is presented that has mainly three steps: (1) Determination of the equivalent rectifier input impedance and the amplitude of input voltage by running SPICE simulation, (2) Drawing contour plots of input power by rectifier candidate on the antenna impedance plane by conducting model calculation and impedance loci of antenna candidates on the contour plots, and (3) Selecting the combination of antenna and rectifier which gives the minimum input power for all the combinations. To validate the equivalent circuit model and design flow, a single-diode (SD) rectifier and a voltage-doubler (VD) rectifier were fabricated in 65 nm CMOS. The input power to generate 100 μA at 1 Vdc was measured and compared. The model, SPICE and measurement are in good agreement with each other that VD has 30–50% lower input power than SD does. In addition, the sensitivity of the parasitic elements, such as the microstrip line and the bonding wires and pads on the input power, are investigated to explore the design space for rectenna.

Joint Resource Allocation on Slot, Space and Power Towards Concurrent Transmissions in UAV Ad Hoc Networks

With innovative applications of unmanned aerial vehicle (UAV) ad hoc networks in various areas, their demands on broad bandwidth, large capacity and low latency become prominent. The combination of millimeter wave, directional antenna and time division multiple access techniques, which enables concurrent transmissions, is promising to deal with it. In this paper, we study the resource allocation problem in UAV ad hoc networks. Specifically, the slot assignment, antenna boresight and transmit power are jointly optimized to promote the network capacity. First, we formulate the optimization problem as the maximization of the fairness-weighted network capacity, subject to the constraint on priority guarantee. Then, because the formulated problem is a mixed integer non-linear programming problem (MINLP), which is NP-hard, two algorithms called dual-based iterative search algorithm (DISA) and sequential exhausted allocation algorithm (SEAA) are respectively proposed to efficiently solve it with acceptable complexity. DISA slacks the MINLP into a continuous-variable optimization problem and solves it with the Lagrangian dual method in an iterative manner. As a heuristic method, SEAA schedules links sequentially, i.e., from high-priority to low-priority ones. Numerical results demonstrate that both DISA and SEAA can efficiently allocate resources for UAVs, while guaranteeing the fairness and priority of links.

Novel space shift keying MIMO technique based on a Steiner triple system

A novel space shift keying (SSK) multiple–input multiple–output (MIMO) technique based on Steiner triple system is proposed and analyzed in this article. SSK attracted considerable research interest in the past few years driven by the several promised inherent advantages including low error probability, low computational complexity and a very simple hardware implementation with very low cost and power consumption. Yet, the spectral efficiency of SSK increases with a base two logarithm of the number of transmit antennas and high data rates are only viable with a massive and impractical number of transmit antennas. Alternatively, generalized SSK (GSSK) scheme is considered, where a combination of antennas is activated at each time instant. GSSK promises the use of arbitrary number of transmit antennas not necessarily a power of two integer. Also, GSSK can attain high data rate with low number of transmit antennas at the cost of substantial degradation in the error performance. In this study, a Steiner triple system is utilized to propose a tailored SSK scheme with substantial reduction in the required number of transmit antennas, without compromising the error probability. It is shown that the proposed Steiner–SSK (S–SSK) MIMO system achieves almost identical error performance to a conventional SSK system but with nearly 90% reduction in the number of transmit antennas. As well, the average bit error rate (ABER) of S–SSK is shown to outperform GSSK by at least 3dB. It is also reported that a S–SSK system accomplishes significant reduction in hardware cost, power consumption, and computational complexity as compared to conventional SSK scheme. Yet, GSSK is shown to marginally outperforms S–SSK in these metrics as it requires smaller number of transmit antennas per a target spectral efficiency.

Beam Focusing for Near-Field Multiuser MIMO Communications

Large antenna arrays and high-frequency bands are two key features of future wireless communication systems. The combination of large-scale antennas with high transmission frequencies often results in the communicating devices operating in the near-field (Fresnel) region. In this paper, we study the potential of beam focusing, feasible in near-field operation, in facilitating high-rate multi-user downlink multiple-input multiple-output (MIMO) systems. As the ability to achieve beam focusing is dictated by the transmit antenna, we study near-field signalling considering different antenna structures, including fully-digital architectures, hybrid phase shifter-based precoders, and the emerging dynamic metasurface antenna (DMA) architecture for massive MIMO arrays. We first provide a mathematical model to characterize near-field wireless channels as well as the transmission pattern for the considered antenna architectures. Then, we formulate the beam focusing problem for the goal of maximizing the achievable sum-rate in multi-user networks. We propose efficient solutions based on the sum-rate maximization task for fully-digital, (phase shifters based-) hybrid and DMA architectures. Simulation results show the feasibility of the proposed beam focusing scheme for both single- and multi-user scenarios. In particular, the designed focused beams provide a new degree of freedom to mitigate interference in both angle and distance domains, which is not achievable using conventional far-field beam steering, allowing reliable communications for uses even residing at the same angular direction.

Low-Complexity GSM Detection Based on Maximum Ratio Combining

Generalized spatial modulation (GSM) technology is an extension of spatial modulation (SM) technology, and one of its main advantages is to further improve band efficiency. However, the multiple active antennas for transmission also brings the demodulation difficulties at the receiver. To solve the problem of high computational complexity of the optimal maximum likelihood (ML) detection, two sub-optimal detection algorithms are proposed through reducing the number of transmit antenna combinations (TACs) detected at the receiver. One is the maximum ratio combining detection algorithm based on repetitive sorting strategy, termed as (MRC-RS), which uses MRC repetitive sorting strategy to select the most likely TACs in detection. The other is the maximum ratio combining detection algorithm, which is based on the iterative idea of the orthogonal matching pursuit, termed the MRC-MP algorithm. The MRC-MP algorithm reduces the number of TACs through finite iterations to reduce the computational complexity. For M-QAM constellation, a hard-limited maximum likelihood (HLML) detection algorithm is introduced to calculate the modulation symbol. For the M-PSK constellation, a low-complexity maximum likelihood (LCML) algorithm is introduced to calculate the modulation symbol. The computational complexity of these two algorithms for calculating the modulation symbol are independent of modulation order. The simulation results show that for GSM systems with a large number of TACs, the proposed two algorithms not only achieve almost the same bit error rate (BER) performance as the ML algorithm, but also can greatly reduce the computational complexity.

In situ time-zero correction for a ground penetrating radar monitoring system with 3000 antennas

The time-zero correction is an essential step in the data pre-processing of ground penetrating radar (GPR) measurements to obtain an accurate signal propagation time between transmitting and receiving antennas. For a novel custom GPR monitoring system with about 3000 antennas and corresponding transceiver structures placed around a soil sample (lysimeter), an in situ approach for the time-zero correction is required. In particular, unknown material properties between any pair of transmitting and receiving antennas prevent a conventional time-zero correction. We present and compare two calibration approaches, namely a pairwise and a mesh calibration, both utilizing the ability of the monitoring system to conduct reciprocal measurements between any pair of antennas. The pairwise calibration enables an individual calibration for any antenna pair, whereas the mesh calibration reduces the influence of the soil between antenna pairs compared to the pairwise calibration. The developed approach is verified by utilizing a mathematical model. Experimental results from a simplified setup show that the lysimeter filling has a negligible impact onto the calibration approach based on adjacent measurements for the mesh calibration. In addition, it is shown that a state of the art time-zero calibration can be used to measure the signal delays within the analog circuit of the measurement system with an accuracy of ±4 ps. The simulation results indicate that by using the developed concept, no prior air calibration between every possible antenna combination is necessary. Thus, this work provides a crucial contribution towards an automated in situ time-zero correction for 3D GPR monitoring systems with many antennas.

Coplanar Dual-Band Dual-Polarized Shared-Aperture Antenna Array For 4/5G Base Station Applications

A novel dual-band dual-polarized shared-aperture antenna array is presented for fifth generation wireless communication application. This novel antenna array is a combination of a low-band antenna and four high-band antennas. In order to simplify the design model while achieving broadband, antenna working on low-band (from 0.68 to 0.99 GHz) and antenna working on high-band (from 3.3 to 5.1 GHz) are both loop-shape radiator fed by Y-shape feed. Coplanar, dual-band and shared-aperture are resolved by embedding four HB antenna elements in the LB antenna. From simulation, the proposed coplanar antenna array respectively achieves 43% (from 0.68 to 0.99 GHz) and 37% (from 3.3 to 5.1 GHz) impedance bandwidth in the low-band and high-band.

Generalized Multistream Spatial Modulation Based on Frequency-Phase Modulated Signals

In this letter, we present an approach to building a new generalized multistream spatial modulation system (GMSM), where the information is conveyed by the two active antennas with signal indices and using all possible active antenna combinations. The signal constellations associated with these antennas may have different sizes. In addition, four-dimensional hybrid frequency-phase modulated signals are utilized in GMSM. Examples of GMSM systems are given and computer simulation results are presented for transmission over Rayleigh and deep Nakagami-<inline-formula> <tex-math notation="LaTeX">$m$ </tex-math></inline-formula> flat-fading channels when maximum-likelihood detection is used. The presented results indicate a significant improvement of characteristics compared to the best-known similar systems.

Enhanced generalized space shift keying with search field based iterative MLD for 6G

This paper proposes the novel enhanced generalized space shift keying (EGSSK) to improve the spectral efficiency (SE) and energy efficiency (EE). In conventional GSSK, all of antenna combinations are not used because of power-of-two form. To overcome this problem, we suggest to exploit spare antenna combination for cell-edge users (CEUs). Concurrently, we propose the search field based iterative maximum likelihood detector (SFMLD) to reduce the complexity at the receiver. The simulated and analytical results are shown in terms of SE, average bit error rate (ABER), complexity and EE.

A Broadband Low-RCS Circularly Polarized Meta-Antenna

A low-profile circularly polarized (CP) meta-antenna with a broadband low-RCS feature is proposed in this article. Our design is the combination of a CP antenna with a chessboard polarization conversion metasurface (CPCM) for balancing the radiation property and stealth feature. To relieve the adverse effect of the CPCM on the entire radiation performance, several redundant meta-atoms with the opposite phase state were removed to enhance the realized gain within the operation bandwidth (8.0–9.0 GHz). The proposed meta-antenna showed excellent radiation performance: −10 dB impedance relative bandwidth was 26.48% (6.78–8.85 GHz), and 3-dB axial ratio relative bandwidth was 22.03% (7.27–9.07 GHz). In addition, RCS reduction over 5 dB was achieved via our design from 8.5 to 21.5 GHz (86.67%) with the help of the deliberately designed CPCM. The final measured results demonstrate great consistency with the simulated ones.

A Study on Application of Dielectric Resonator Antenna in Implantable Medical Devices

Worldwide, a large number of patients are benefited every year due to technological advancement in implantable medical devices (IMDs) such as in hyperthermia and bio-telemetry. The combination of sensors and antennas defined the quality of the implantable device. Antenna communities strive hard to fulfill the needs of the medical world by introducing new designs and concepts in this field. The purpose of this study is to identify major existing challenges and provide suitable solution of these challenges for implant applications. Present implant antennas have faced inferior performance due to high metallic losses and varied implant depth. The human body is a combination of dielectric materials, regardless of whether it is liquid (eg. water), gels or hard bones. In this study, first time a dielectric resonator antenna (DRA) resonating at 2.45 GHz, has been proposed as an implantable antenna with no metallic losses, varied implant depth performance and bio-compatibility. The implant DRA is placed on a bio-compatible polyvinyl chloride (PVC) substrate with a thickness of 0.5 mm. The rectangular DRA excited by a coplanar waveguide feed is proposed and its performance is compared with the help of four phantoms given in the literature. A detailed link design study was also undertaken in view of the different applications.

Efficient Hardware Implementation of CORDIC-Based Symbol Detector for GSM MIMO Systems: Algorithm and Hardware Architecture

Aiming at providing an efficient hardware architecture for generalized spatial modulation (GSM) multiple-input multiple-output (MIMO) systems, in this paper a COordinate Rotation DIgital Computer (CORDIC) -based symbol detector is proposed. In the proposed detector, several CORDIC-based Givens rotation modules are conducted in parallel for the transmit antenna combinations (TACs) to facilitate QR-decomposition. After that, the proposed detector uses adders, shifters, and backward substitution mechanisms to currently estimate symbols for the corresponding TAC. At last, the estimated symbols and corresponding TAC index with the smallest distance measurement are chosen as the final solution. In particular, to achieve efficient hardware implementation, the architecture of the proposed detector has several features, including multiplication-free ranking mechanism, parallel CORDIC-based architectures, and shorter-bit-length multipliers. In addition, the overall architecture is pipelined to speed up the processing of the hardware. At last, simulation results reveal the proposed detector performs near to the optimal maximum likelihood (ML), but uses lower computational complexity. Additionally, the VLSI implementation results under the TSMC 90-nm CMOS technology show that the proposed hardware architecture requires 266K gates (KGEs), provides detection throughput 2.008 Gbps, works with pre-processing latency of 47 clock cycles, and has the hardware efficiency 7.54 (Mbps/KGEs) while operating at frequency 200.8 MHz. Moreover, implementation comparisons show the proposed architecture provides high throughput rate as well as hardware efficiency, and works with low pre-processing latency.

Novel RF energy harvesting using Rectenna

In this paper an experimental RF energy harvester using rectifying antenna (rectenna) to harvest ambient energy from cellular device operating at 900 MHz GSM band is proposed. The circuit is a combination of antenna and rectifying circuit using Schottky barrier diode for microwave (RF) to DC conversion. The performance results of the rectenna shows radiation efficiency of around 58.81%, gain of 3.9 dB and directivity of 5.972 dBi. The proposed rectenna design can prove to be a low cost device for wireless power transmission and RF energy harvesting. The prototype is fabricated with simulated and measured results in good agreement, having a return loss of 21 dB at frequency of around 885 MHz. The overall efficiency is enhanced by using ISS351-TB-E Schottky diode which is categorized by a low junction capacitance and a low threshold voltage to achieve higher conversion efficiency.