Periodic Slots Research Articles

A composite microstrip line and leaky wave antenna structure with self-diplexing characteristic

A novel structure is proposed for the dual-band self-diplexing integration of microstrip line and leaky wave antenna (LWA). Through introducing a mode selective transmission line (MSTL) to the antenna, the autonomous transition between transmission modes at varying operating frequencies is thus achieved. At the high-frequency band, such proposed antenna in the quasi-TE10 mode, the periodic slots, and patches are used as LWA. Meanwhile, at the low-frequency band, the baseband signal with quasi-TEM mode can be transmitted effectively. These experimental results demonstrate that this design strategy benefits the realization of transmission with an insertion loss of less than 3 dB below 5.5 GHz. Furthermore, this antenna enables continuous beam scanning of −1 space harmonics from 10.5 to 15.5 GHz, with a beam direction sweeping from −75° to + 54°. This study innovatively employs MSTL structure to solve the problem of radio frequency (RF) and baseband links operating independently in traditional communication systems. It provides a promising solution for multi-functional integrated applications in future wireless communications.

RL-ANC: Reinforcement Learning-Based Adaptive Network Coding in the Ocean Mobile Internet of Things

As the demand for sensing and monitoring the marine environment increases, the Ocean Mobile Internet of Things (OM-IoT) has gradually attracted the interest of researchers. However, the unreliability of communication links represents a significant challenge to data transmission in the OM-IoT, given the complex and dynamic nature of the marine environment, the mobility of nodes, and other factors. Consequently, it is necessary to enhance the reliability of underwater data transmission. To address this issue, this paper proposes a reinforcement learning-based adaptive network coding (RL-ANC) approach. Firstly, the channel conditions are estimated based on the reception acknowledgment, and a feedback-independent decoding state estimation method is proposed. Secondly, the sliding coding window is dynamically adjusted based on the estimates of the channel erasure probability and decoding probability, and the sliding rule is adaptively determined using a reinforcement learning algorithm and an enhanced greedy strategy. Subsequently, an adaptive optimization method for coding coefficients based on reinforcement learning is proposed to enhance the reliability of the underwater data transmission and underwater network coding while reducing the redundancy in the coding. Finally, the sampling period and time slot table are updated using the enhanced simulated annealing algorithm to optimize the accuracy and timeliness of the channel estimation. Simulation experiments demonstrate that the proposed method effectively enhances the data transmission reliability in unreliable communication links, improves the performance of underwater network coding in terms of the packet delivery rate, retransmission, and redundancy transmission ratios, and accelerates the convergence speed of the decoding probability.

Implementation of COVID-19 vaccination services in prison in six European countries: translating emergency intervention into routine life-course vaccination.

Evidence has shown that the risk of transmission of SARS-CoV-2 is much higher in prisons than in the community. The release of the COVID-19 vaccine and the recommendation by WHO to include prisons among priority settings have led to the inclusion of prisons in national COVID-19 vaccination strategies. Evidence on prison health and healthcare services provision is limited and often focuses on a single country or institution due to the multiple challenges of conducting research in prison settings. The present study was done in the framework of the EU-founded project RISE-Vac. It aimed to analyse the best practices and challenges applied in implementing COVID-19 universal vaccination services during the pandemic to support future expansion of routine life course vaccination services for people living in prison (PLP). Two online cross-sectional surveys were designed and piloted: survey1 on prison characteristics and (non-COVID-19) immunisation practices; survey2 on the implementation and coverage of COVID-19 vaccination with open-ended questions for thematic analysis. Each RISE-Vac project partner distributed the questionnaire to one or two prisons in their country. Answers were collected from eight European prisons' directors or medical directors between November 2021-May 2022. According to our findings, the implementation modalities of COVID-19 vaccination services in the surveyed prisons were effective in improving PLP vaccination coverage. Strategies for optimal management of the vaccination campaign included: periodic time slot for PLP vaccination; new staff recruitment and task shifting; distribution of informational material both to PLP and prison staff. Key challenges included continuity of care after release, immunisation information system, and vaccine hesitancy. To the best of our knowledge, this is the first study describing the implementation of COVID-19 vaccination services in European prisons, suggesting that the expansion of vaccination provision in prison is possible. There is no unique solution that will fit every country but commonalities likely to be important in the design and implementation of future vaccination campaigns targeting PLP emerged. Increased availability of vaccination services in prison is not only possible, but feasible and highly desirable, and can contribute to the reduction of health inequalities.

A segmented periodic slot array leaky‐wave antenna for beamforming applications

AbstractA segmented periodic slot array leaky‐wave antenna (LWA) is proposed for beamforming applications. The LWA consists of segments, each with a unique propagation constant achieved through varying periodicity and slot size. By using segments with different propagation constants, the proposed LWA can achieve beamforming such as flat‐top beams and side‐lobe level (SLL) reduction. The LWA is based on a substrate‐integrated waveguide with periodic double transverse slots in the broad wall of the waveguide. The double slots allow for reflection‐canceling to suppress the broadside stopband and hence can achieve beamforming capabilities in the backward, broadside, and forward directions. Full‐wave simulations are used to demonstrate the proposed concept for flat‐top beamforming in the mm‐wave band at 30 GHz. Experimental demonstration is conducted using two prototypes for flat‐top beams and SLL reduction, with good agreement with full‐wave simulations.

Cosecant-squared pattern synthesis of leaky-wave antenna using ridge waveguide

Antennas with a cosecant-squared pattern play a significant role in air-surveillance radar systems. In this article, a cosecant-squared pattern leaky-wave antenna (LWA) is synthesized using a ridge waveguide. The LWA consists of periodic shunt slots located at the broad wall of a ridge waveguide. To obtain the desired cosecant-squared pattern, the attenuation and the phase constant must be controlled properly along the antenna length. To this end, the slots offset and the ridge profile are properly tapered along the antenna. This adjustment is performed through an optimization algorithm such as a genetic algorithm (GA) optimization. Through the proposed antenna configuration, a cosecant-squared pattern LWA with a wide range of 10° to 40° together with low ripples (≤2 dB) in the shaped region and a low level of sidelobes (≤−18 dB) is synthesized, fabricated and measured. Apart from the good agreement between the simulation and the measurement results, such a design indicates a size reduction (about 47%) compared with the previous published work.

A novel reconfigurable H-plane Horn leaky wave Substrate Integrated Waveguide MIMO antenna for K band

In this paper a novel reconfigurable H-plane horn Multiple Input Multiple Output (MIMO) leaky wave substrate integrated waveguide (SIW) antenna is proposed. The antenna is operating at two resonant frequencies, 22.8 GHz and 26.32 GHz. The transverse periodic leaky wave slots are radiating power in the broadside direction at 22.8 GHz and pattern diversity is achieved at 26.32 GHz. Dielectric loading and an array of meta-material structures are used, which further improve gain of the antenna. The antenna achieves better matching with a return loss of –33.5 dB at 22.8 GHz and maximum isolation of −38.7 dB at 26.32 GHz is achieved between antenna elements. A 2x2 and 4x4 MIMO SIW antenna is designed and analyzed in this paper. All the MIMO performance measurement parameters have values within limits. The antenna achieves a maximum gain of 7.3 dBi and 8.1 dBi. The proposed antenna operates in the K band (18 GHz–27 GHz) region, making it suitable for automotive radars and short-range applications.

Large Frequency Ratio Antennas Based on Dual-Function Periodic Slotted Patch and its Quasi-Complementary Structure for Vehicular 5G Communications

Dual-function periodic slotted patch and its quasi-complementary structure in designing large frequency ratio antennas for vehicular 5G communications are presented in this paper. Firstly, a circular patch with periodic circular slots is employed as a partially reflecting surface (PRS) antenna in the millimeter-wave band. Simultaneously, the circular slotted patch is operated in the microwave band as a patch antenna, achieving dual functions. It is flexible to design the two antenna parts due to their polarization orthogonality. In the next place, with similar working principles, its quasi-complementary structure that contains periodic connected circular patches is also utilized for the large frequency ratio antenna design. As the proof of concept, two large frequency ratio antennas working in the 3.5-GHz and 28-GHz bands with a frequency ratio of 8 for 5G applications were designed. Finally, for verification, a periodic slotted patch antenna was fabricated and measured. Good agreement between the measured and simulated results is found. Measured -10-dB impedance bandwidths of 6.25% (3.41–3.63 GHz) and 20.57% (24.21–29.76 GHz), and measured peak antenna gains of 8.14 dBi and 14.04 dBi are obtained at the lower and upper bands, respectively. The antennas can be integrated solutions for vehicular-platform 5G microwave and millimeter-wave wireless communications.

A zone-based optical intra-vehicle backbone network architecture with dynamic slot scheduling

As Ethernet has a large bandwidth capacity, it is commonly proposed as a backbone for future intra-vehicle networks. However, satisfying the severe hardware reliability requirements of intra-vehicle networks while providing high-bandwidth and low latency by Ethernet may be costly. As a solution, we propose a novel optical intra-vehicle backbone network architecture that may have a lower cost and higher reliability in terms of hardware when compared to Ethernet. However, unlike traditional optical Ethernet architectures, only a single master node has transmitter laser diodes in the backbone of our architecture, so the gateway nodes cannot generate and send packets to the backbone links directly. As the gateways cannot inform the master node and request a slot when they have a new packet to send, a slot scheduling algorithm with polling is necessary to detect and transfer the new packets in the gateways, which may cause higher transmission delays compared to Ethernet. In this paper, we present our optical intra-vehicle backbone network architecture and propose two slot scheduling algorithms. We show that using a dynamic slot scheduling algorithm decreases packet delays when compared to fixed periodic slot scheduling in our architecture. We also evaluate the total delays including traffic shaping and processing delays in an optical TSN Ethernet backbone architecture as a reference. We show that the extra delays due to slot scheduling in our architecture may be negligibly low when compared with traffic shaping and processing delays.

A compact quad‐band circular cavity backed substrate integrated waveguide antenna for millimeter wave applications

AbstractIn this letter, a compact circular cavity‐backed, circularly polarized substrate integrated waveguide (SIW) multiband antenna is proposed. In the outer circular cavity, an array of two periodic metal slots, tilted at an angle, resonate at 25.32, 26.44, and 28.83 GHz, and the inner circular cavity's periodic slots radiate at 28.01 GHz. Two concentric SIW cavities are structured in such a distinct manner that no loss due to leakage takes place thus, achieving a maximum isolation of −43.8 dB at 28.83 GHz. The miniaturized antenna has dimensions of 2.2λo × 2.2λo × 0.1λo where λo is the operating wavelength. It achieves a maximum gain of 9.1 dBi at 26.44 GHz, and VSWR < 2 is achieved at all frequency bands. The antenna is circularly polarized at 26.44 and 28.01 GHz as well. The design results are plotted in the Ansys high‐frequency structure simulator version EM19.2 tool. The proposed antenna is fabricated and tested using an Anritsu Vector Network Analyzer version v4.0 with an anechoic chamber setup.

High-Power Supersymmetric Semiconductor Laser with a Narrow Linewidth

We have designed and fabricated a kind of supersymmetric slotted Fabry–Perot semiconductor laser near 1550 nm to achieve a single-mode, high-power, and narrow-linewidth operation. The structure of the laser is composed of an electrically pumped broad ridge waveguide in the middle to provide optical gain, a group of periodic slots etched near the front facet to suppress the extra longitudinal modes and achieve a narrow linewidth, and a pair of passive superpartner waveguides located on both sides to filter out the high-order lateral modes in the broad waveguide. The device measured under the temperature of 25 °C shows an output power of 113 mW, a single-lobe lateral far-field distribution with the full width at half maximum of 7.8°, a peak wavelength of 1559.7 nm with the side-mode suppression ratio of 48.5 dB, and an intrinsic linewidth of 230 kHz at the bias current of 800 mA. The device is a promising candidate for cost-effective light sources for coherent communication systems and LiDARs.

A Multi Stub Polygon Shaped Textile Antenna for Deformation Performance Using Aperiodic DGS

A compact fully flexible antenna with 1.22 as dielectric constant with 0.016 loss tangent is designed for wearable biomedical applications. It has dimensions of 40.5 x 23 x 0.97 mm3. The polygon-shaped patch is modified to achieve ultra-wideband frequencies using partial ground as 16.5mm and a periodic vertical slot of 13x2 mm2 structure in defected ground structure to enhance the wide bandwidth of 2.6-11.1 GHz. Using a transmission line equation and a microstrip line feeding method, the resulting antenna operates at a biomedical frequency in open space and on the body-worn case with multi band i.e. 3.1 and 5GHz. The deformation process works well for the proposed antenna without affecting its actual bandwidth with 20 to 60 mm radii. Additionally, the proposed antenna operates at 5GHz for Wi-Fi with 3.67dBi gain, -35.1dB as S11 which is suitable for commercial applications. CST Microwave Studio was used to simulate the antenna and fabricate it for testing.

Broadband filtering balun employing spoof surface plasmon polariton and substrate integrated waveguide

In this paper, two filtering baluns exploiting a combination of spoof surface plasmon polariton (SSPP) and substrate integrated waveguide (SIW) techniques are proposed. The characteristic of out-of-phase between two output ports can be achieved by employing the multilayered SIW structures. The sub-wavelength periodic slots in improved dumbbell-shapes are etched on the top and bottom surfaces of SIW transmission lines (TLs). The dispersion characteristics and transmission performance of the SSPP-SIW unit cells are meticulously investigated. The lower and upper cut-off frequency can be controlled independently by adjusting the physical sizes of the SIW and SSPP structures. For validation, two cases of filtering baluns are designed, fabricated and measured. The measured and simulated results have reached satisfactory agreements. The experimental results exhibit that the developed prototype can achieve a fractional bandwidth (FBW) of>66%. Furthermore, HMSIW is implemented to integrate with SSPP configuration to decrease the circuital area of SSPP-SIW filtering balun by 50%.

Simulation analysis of the near and far fields of an ARROW laser array with narrow slots.

We studied a periodic slot-based three-core antiresonant reflecting optical waveguide laser array structure. Periodic narrow slots are used to define functional areas in the array, which directly avoids the epitaxial regrowth in the fabrication of traditional antiguide arrays. A comparative study confirmed the feasibility of the scheme. Moreover, the calculation results show that, with the increase of the width of the antiguide core, the power ratio of the main lobe in the far field increases, and the divergence angle of the main lobe and the angle between the secondary lobe and the main lobe decrease. This law provides ideas for the optimization of the array structure.

Circularly Polarized High Gain Leaky-Wave Antenna for CubeSat Communication

In this work, a novel planar leaky-wave antenna (LWA) and its array are proposed and presented for CubeSat communication applications. Using the substrate-integrated waveguide (SIW) technology, the proposed LWA is implemented by etching periodic fan-shaped slots on top of an SIW. These novel fan-shaped slots exhibit extraordinary circular polarization (CP) radiation in high efficiency over a wide frequency band. Moreover, by switching the excitation ports, both left-handed (LH) and right-handed (RH) CPs are achieved in a wide beam steering range backward or forward. An SIW LWA prototype has been designed and tested with validate LHCP/RHCP steering beams ranging from –51° to 0° or from 51° to 0° in the elevation when the frequency varies from 27.4 to 37.3 GHz. In the 30% frequency band, the axial ratios (ARs) on the main beams are all less than 3 dB demonstrating the broadband CP characteristic. In this 1-D LWA, the realized gain varies from 12.4 to 17.9 dBi. However, it requires higher gain and a fixed beam but narrow bandwidth (BW) in some applications like CubeSats. Hence, a conformal LWA array is further introduced by combining the CP radiation of two LWAs deployed in two perpendicular surfaces of a one cubic unit (1U) CubeSat. Fed by an elaborated vertical transition, the conformal array is designed at 28 GHz with a high directive sum beam along the diagonal direction, requiring each LWA to radiate at ± 45°. As a result, the total gain is enhanced from 14.4 to 16.6 dBi with an AR of 1.8 dB and a sidelobe level (SLL) of −17.1 dB. The proposed compact planar LWA and its array provide promising CP radiation in terms of ARs, BW, polarization flexibility, impedance matching, efficiency, and gain, which reveals great potential for applications in satellite communication systems that demanding low profile, lightweight, dual CPs, and high directivity.

A 3D indoor positioning system based on common visible LEDs

We propose a realistic 3D positioning system for indoor navigation that exploits visible Light Emitting Diodes (LEDs), placed on the ceiling. A unique frequency tone is assigned to each lamp and modulates its intensity in periodic time slots. The Time Difference of Arrival (TDOA) is measured without the need of a synchronization system between the sources and the receiver, then it is used to accurately estimate the receiver position. We first describe the theoretical approach, then propose the model and characterize the possible sources of noise. Finally, we demonstrate the proof-of-concept of the proposed system by simulation of lightwave propagation. Namely, we assess its performance by using Montecarlo simulations in a common room and estimate the impact of the different implementation parameters on the accuracy of the proposed solution. We find that, in realistic conditions, the technique allows for centimeter precision. Pushing the device requirements, the precision can be further increased to a sub-centimeter accuracy.

Dual-Band Aperture-Shared Fabry–Perot Cavity-Integrated Patch Antenna for Millimeter-Wave/Sub-6 GHz Communication Applications

This letter presents a dual-band antenna with a large frequency ratio of 11.7 (2.4 GHz/28 GHz) by integrating an mm-wave Fabry–Perot cavity (FPC) antenna into a sub-6 GHz patch antenna. The patch with periodic slots functions as both the 2.4 GHz radiator and the partially reflective surface (PRS) of the 28 GHz FPC antenna. By properly tuning the length of the periodic slot, the PRS's reflection can be easily adjusted. As the periodic slot's length and width operating at 28 GHz are much smaller than the wavelength at 2.4 GHz, periodic slot operating at 28 GHz have little impact on the radiation of the patch. Furthermore, because of the Fabry–Perot resonance, the antenna can have a peak gain reaching 15 dBi at 28 GHz band with an easy feeding structure. For demonstration, a prototype is fabricated and experimentally verified. Note that the frequency ratio is not limited to the proposed design (11.7 for demonstration). It can be easily adjusted based on the same principle.

Circularly Polarized High Gain Coaxial Line Leaky Wave Antenna With Backfire Radiation

This communication presents a leaky wave antenna based on a standard rigid coaxial cable showing circular polarization (CP) in the backfire direction. Here, CP is achieved by using a sequential rotation scheme. Periodic slots are cut on the outer conductor of the cable leading to radiation from the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n = -1$ </tex-math></inline-formula> th fast space harmonic. The circular geometry of the coaxial cable allows to easily obtain space quadrature by rotating the successive slots by 90° about the cable axis. The required time quadrature for CP is obtained by slot-to-slot separation along the propagation direction. The antenna is designed and fabricated for X-band applications using a low-cost coaxial cable and is excited using a standard SMA connector. The measured gain is 20.26 dBic with 3 dB beamwidth of 14° at 10.26 GHz. The measured axial ratio of the left-handed CP antenna is below 1.8 dB in the backfire direction.

A substrate integrated waveguide based dual‐band leaky‐wave antenna fed by TE 10 and TE 20 modes

A dual-band leaky wave antenna (LWA) based on substrate integrated waveguide (SIW) is presented in this paper. The radiation elements are composed of a set of periodical transverse slots and a long longitudinal slot that can radiate scanning beams at two different bands under TE10-mode and TE20-mode excitation, respectively. The scanning beams in the two bands both cover the forward region, and polarizations are perpendicular. Under TE10 excitation, the proposed antenna radiates scanning beams in the low band (8.2 GHz ~ 9.1 GHz) with gain varying from 10.6 to 15.9 dBi. Under TE20 excitation, the beams of the proposed antenna scan in the high band of 18.8 GHz ~ 22 GHz with gain varying in 11.7 dBi ~ 16 dBi. The measured results of the fabricated prototype confirm the design theory and simulated results.

Circularly Polarized Leaky-Wave Antenna With Natural Curl Property

This letter proposes a novel leaky-wave antenna (LWA) based on low profile substrate integrated waveguide (SIW), which can operate in either left-handed circular-polarization (LHCP) or right-handed circular-polarization (RHCP) mode. Different from other kinds of literature, the proposed SIW LWA is capable of CP state switching without introducing multiple LWA elements, phase-correct couplers or polarization converter, which is a single LWA element with a simple coaxial feeding/matching structure. Specially, the periodic slots on its radiation aperture are Archimedean spiral slots which are curved slots with curl property. These curled slots can excite vortex fields in the waveguide channel of SIW, and the generated vortex field is capable of changing vortex direction by selectively exciting the port of LWA, making the CP features flexible. The final Archimedean spiral slotted SIW LWA realizes LHCP or RHCP (AR < 3 dB) in the wide CP band of 27.7–34.6 GHz (BW = 22%), and the LHCP scanning range is from −51° to −10° while the RHCP beam scans from 10° to 50°.

A compact circularly polarized half‐mode substrate integrated waveguide‐based leaky‐wave antenna array with wide range of dual‐beam scanning

In this article, a compact circularly polarized (CP) leaky-wave antenna (LWA) array based on half-mode substrate integrated waveguide (HMSIW) structure is proposed, which has the capability of dual-beam scanning in wide range through broadside. This array consists of two HMSIW LWAs with periodic π-shaped slots, which can excite-first space harmonic mode with CP waves, and an HMSIW power-recycling semicircular structure, which is designed between the end of the first LWA and the start of second LWA to generate two symmetrical scanning beams. Moreover, the structure of this array is optimized to make the two beams have similar gain values. The results validate that the proposed array has one CP beam scanning from −62 to 14° and another CP beam scanning from 60 to −16° when the operating frequency changes from 5.2 to 7.5 GHz. The measured gains and axial ratios are also given and show good agreements with the full-wave simulated results.