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This article presents a meticulously engineered MIMO antenna system tailored specifically for 26 GHz millimeter-wave applications. It integrates a compact planar-patterned metamaterial (MTM) structure, carefully designed with split square and hexagonal unit cells to realize an effective near-zero index (NZI) range for both permeability and permittivity. Comprehensive wave propagation analysis along the y-axis rigorously examines the MTM's characteristics. The antenna system showcases impressive technical attributes, including an extensive 8.7 GHz bandwidth, notably highlighting mu-near-zero (MNZ) characteristics spanning over 8.7 GHz wide frequency spectrum, and epsilon near zero (ENZ) properties covering 8 GHz (26–34 GHz). Notably, a 4-ports MIMO antenna design is adopted with each element meticulously crafted using a 4-unit cell array configuration. The designed 4 × 4 MIMO antenna is fabricated using Rogers RT/duroid 5880 substrate and it occupies a compact dimension of 45.5 × 45.5 × 0.8 mm3. Experimental validation reveals compelling performance metrics, including a bandwidth spanning from 24.3 to 30.9 GHz, isolation levels below − 25 dB, and a maximum peak gain of 15.48 dBi. Additionally, the antenna exhibits circular polarization characteristics, maintaining an axial ratio below 3 dB within the frequency bands of 25.35 to 28.05 GHz and 28.10 to 29.83 GHz. Furthermore, the fabricated MIMO antenna demonstrates outstanding diversity parameters, exemplified by a high diversity gain (DG > 9.99), low envelope correlation coefficient (ECC < 0.0001), minimal channel capacity loss (CCL < 0.5), and total active reflection coefficient (TARC < − 8 dB). The suggested MTM-based MIMO antenna system with sophisticated design and exceptional performance could be an exemplary choice for seamless integration into the evolving landscape of 5G NR networks, particularly those operating within the n257/n258/n261 bands. [ABSTRACT FROM AUTHOR]

Summary: In this communication, a dual port printed multi‐input and multi‐output (MIMO) antenna with high isolation of dimension 12 × 8.5 × 0.8 mm3 is designed, analyzed, and investigated for 28‐GHz 5G mm‐wave applications. The metasurface layer is suspended over the MIMO antenna to convert the linearly polarized (LP) wave to a circularly polarized (CP) wave. The unit cell of the metasurface consists of a square‐shaped conducting strip with one side of diagonal points interconnected. The conducting strip and rectangular gap between the strips etched on the substrate are capable of generating the π/2 phase shifted electric field components (Ex and Ey) resulting in polarization conversion from LP to CP. The machine learning concept is used to characterize the dimensional configuration of the antenna to achieve the optimum throughput. The MIMO diversity performance parameters and antenna essential results are validated by the measured counterparts. [ABSTRACT FROM AUTHOR]

Summary: A novel antenna system that utilizes multiple‐input and multiple‐output (MIMO) technology to suit the requirements of 5G applications is proposed in this article. The antenna has a wide operating bandwidth and high isolation in n257/n258/n261 5G bands. The suggested arc‐shaped MIMO antenna is composed of four similar patch units with modified ground planes arranged in a four‐port configuration and is made on a Rogers RT/duroid 5880 substrate, which measures 31.891 × 37.5885 × 0.508 mm3. The prototype of the suggested MIMO antenna is realized to confirm the obtained simulated results and validate the proposed design. The four‐port MIMO antenna features a broad frequency range of 7.3 GHz from 21.8 to 29.1 GHz, a peak gain of 5.76 dBi at 29 GHz, and a good isolation less than −18 dB. The proposed antenna's MIMO performance is evaluated by analyzing several diversity parameters. The findings of the evaluation demonstrate an envelope correlation coefficient (ECC) value of less than 0.001, a diversity gain (DG) value exceeding 9.995 dB, and an average mean effective gain (MEG) of −3 dB within the operational frequency band. The suggested MIMO antenna's compact size and impressive performance make it a suitable choice for intended n257/n258/n261 5G NR networks. [ABSTRACT FROM AUTHOR]

Summary This article analyses a substrate integrated waveguide (SIW) fractal koch surface (FKS) slot antenna performance for Ka‐band applications. This FKS slot shape is obtained by modifying the conventional rectangular slot with the first iteration of the FKS method. The resultant FKS slot behaves as a radiator in the provided space. A single‐ and two‐element FKS slotted SIW antenna characteristics are analysed on a 20 mil thick RT/Duroid 5880 substrate and compared with the conventional rectangular slot. The proposed antenna with dimensions 15×5×0.508$$ 15\times 5\times 0.508 $$ mm3 achieves an impedance bandwidth from 27.4 to 32.1 GHz with a fractional bandwidth of 15.79% and achieves a gain of 8.3 dBi in broadside direction by improving space filling factor in SIW structure. The prototype of the SIW‐fed FKS slotted antenna array measurement results is satisfactory with the simulation results. [ABSTRACT FROM AUTHOR]

This study presents a symmetrical two-element Multiple-Input Multiple-Output (MIMO) antenna that exploits a feasible spectrum for 5G millimetre structure on the ground plane.It is attained to one additional operating mode at 24 GHz. A Rogers RT5880 substrate material is used in the construction of the proposed MIMO antenna. This substrate material has dimensions of 0.064 λ × 0.012 λ (at 24 GHz), a thickness of 0.8 mm, and a dielectric constant of 2.2.The results of the testing suggest that the antenna has the potential to span a frequency range that stretches from 23.5 to 25.5 GHz (6.1%) and from 34.2 to 36.4 (8.2%) GHz. In addition, the antenna does not need the usage of a sophisticated decoupling structure in order to achieve an inter-port isolation of higher than 15 dB between the antenna components across both bands. This is possible since the antenna is dual-banded. The results that were obtained from the measurement of the antenna after it was put through its paces are as follows. The components that make up this diagram are merged together to form a single entity. An envelope correlation coefficient of less than 0.005 and a channel capacity loss of less than 0.315 bits/s/Hz are the results of analysing the diversity performance characteristics. These results are totally compatible with the criteria and norms that are taken into consideration to be acceptable as a whole. The findings demonstrate that the design can successfully transmit millimetre waves at 5G rates, which was the goal of the study. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive study of Class‐‐E/F2 and inverse Class‐‐F power amplifiers (PAs) designed for 35–42 GHz millimeter‐wave applications, utilizing a 130 nm CMOS process. The proposed RF PAs are well suited for wide frequency‐band millimeter‐wave and 5G radio transmitters. A comprehensive study of limiting factors in amplifier efficiency is presented in this paper. The study encompasses an analysis of all the factors that restrict the efficiency of the switched power amplifier. The first proposed power amplifier is based on the Class E/F2 architecture, comprising a parallel capacitor, second harmonic resonance circuit, and output matching network. Conversely, the second suggested power amplifier is constructed using the inverse Class‐‐F topology, which includes harmonic termination and matching networks. The harmonic termination circuit incorporates a second harmonic resonance network and utilizes a parasitic capacitor to control the harmonic components. Both the proposed Class E/F2 and inverse Class‐‐F architectures are employed to reshape the drain current and voltage waveforms, aiming to reduce the overlap between them and, consequently, improve efficiency. The suggested power amplifiers comprise a driver Class‐‐AB stage and a power stage constructed based on either the Class E/F2 architecture or inverse Class‐‐F topology, utilizing harmonic termination networks at the output load. Two new designs of high‐Q factor on‐chip finger capacitors have been implemented to improve efficiency and radio frequency performance. Achieving input matching and inter‐stage matching is facilitated by employing two novel on‐chip transformers designed for maximum power transfer. Additionally, an inter‐stage matching inductor is utilized in a cascode configuration to enhance the overall RF performance. The on‐chip transformers, inductors, and finger capacitors are designed using the HFSS software program. S‐parameter files (SNP files) of the designed on‐chip components are extracted and inserted into the simulation tool to ensure accurate results. The proposed Class E/F2 power amplifier achieves a constant power of 14.9 dBm, an extreme power added efficiency (PAE) of 11.7%, and a maximum gain of 13.74 dB. In contrast, the suggested inverse Class‐‐F power amplifier attains a constant power of 15.4 dBm, a peak PAE of 12.6%, and a maximum gain of 14.8 dB. The DC power consumption is 73 and 66 mW for the proposed Class E/F2 and inverse Class‐‐F PAs, respectively, while their active sizes are 0.14 and 0.2 mm2. [ABSTRACT FROM AUTHOR]

We present a compact, filtering power divider (FPD) using integrated passive device technology (IPD) for mm‐wave applications. Our proposed FPD design integrates quarter‐wavelength coupled‐resonator bandpass filters with a Wilkinson power divider, using size reduction techniques. Coupled coplanar waveguides provide excellent coupling while occupying a small area, and metal‐insulator‐metal capacitors offer the required λ/4 phase shift without length extension. The center frequency of the filtering power divider/combiner (FPD/C) is located at 30‐GHz. We demonstrate our FPD design by fabricating four prototypes with parameter variations. The insertion loss, fractional bandwidth, and size of the FPD/C designed in this study are from 2.56 to 3.3 dB, from 9.67% to 19.4%, and from 0.592 to 0.220‐mm2, respectively. In addition, the return loss of all models at the center frequency is 28.5 dB or more, and the isolation is 16.6 dB or more. [ABSTRACT FROM AUTHOR]

High‐performance frequency selective surfaces (FSSs) have gained attention for their spatial filtering characteristics in 5G communication systems. In this work, we propose an efficient and accurate design methodology for the FSS. Three different artificial neural network methods (ANN) are employed, and their performances are compared for analysis and synthesis purposes. Results show that GRNN has the highest performance for both training and test phase of ANN based FSS analysis and synthesis. A novel, compact, low‐profile triple band FSS unit cell is introduced, and the working mechanism is described. By applying ANN based design procedure, the unit cell dimensions to resonate at the 5G mm‐wave frequency band is extracted. A unit cell with the extracted physical dimensions is simulated with a full‐wave analysis tool. The simulation results show that the FSS has the filtering feature at the predetermined mm‐wave frequencies of the 5G communication. The prototype of the FSS is fabricated, as well. The simulations are verified experimentally with measurement results. The results show that proposed ANN based analysis and synthesis method can be an effective tool for the design of FSS band‐pass filter for 5G applications. [ABSTRACT FROM AUTHOR]

This manuscript presents comprehensive modal analysis of a compact, half-mode SIW-fed slot-coupled dual-band antenna. The Characteristic Mode Analysis (CMA) is investigated in detail and presented for the first time to analyze the radiation behavior and frequency domain characteristics of the proposed structure. The number of dominant operative modes supported by the antenna is decided based on the number eigen factors, its corresponding values, and the characteristic angles. The antenna operates at 33 and 38.14 GHz with a return loss of 20.5 and 19.5 dB, a gain of 7.9 and 6.7 dBi, and an efficiency of 90% and 88%, respectively. Measured results are in close resemblance with the CMA, considering the difference between the conventional cavity modes and the characteristic modes of the proposed planar cavity configuration. The methodology can be extended to characterize any arbitrary shape radiating geometry. [ABSTRACT FROM AUTHOR]

A wearable millimetre-wave radar antenna operating in 24.05–24.25 GHz for imaging applications in collision avoidance to assist visually impaired people is presented. Non-uniform excitation for the series end-fed 1 × 10 array antenna is optimized in simulation achieving a modified Dolph–Chebyshev distribution, which provides improved performance in terms of beam width, Side-lobe level and Gain. Commercial RO3003 and eco-friendly polypropylene (PP) are considered as substrates for comparison purposes, being the PP electromagnetically characterized for the first time at such high frequencies. Consistent agreement between simulation and measurement results is achieved for antenna prototypes on both dielectrics. The impedance matching bandwidth is analysed for the antenna on PP also under bent conditions. The overall size of the compact, low-cost, eco-friendly and flexible antenna on PP is 98.68 × 14.4 × 0.52 mm3 and, according to literature survey, it overcomes the state of the art on wearable radar antennas at 24 GHz. [ABSTRACT FROM AUTHOR]

This paper describes a four-port MIMO antenna array design featuring bow-tie-shaped slot-loaded patches with wideband capabilities that cover the frequency range from 24.2 GHz to 30.8 GHz. The proposed antenna design is printed on an FR4 substrate and occupies an area of 25 × 24 mm2. The MIMO antenna consists of four antenna arrays that are symmetrically placed in an upper-lower configuration. The bow-tie-shaped slots loaded radiators are separated horizontally by 3.48 mm and vertically by 5.94 mm. Each antenna array contains two elements that are separated by a distance of wavelength/4. The suggested MIMO antenna array delivers a high gain of 19.09 dB at 27.8 GHz and has a bandwidth of 6.6 GHz that covers the frequency band of 24.2–30.8 GHz. The research demonstrates the quality of the proposed MIMO antenna through various diversity parameters such as mutual coupling, port correlation, diversity gain, and data rate that can be transmitted over a communication medium. The simulation results are validated and found to be consistent with the experimental results. The presented antenna covers the entire bandwidth allocated to different regions, including Europe (24.25–27.5 GHz), Sweden (26.5–27.5 GHz), USA (27.5–28.35 GHz), China (24.25–27.5 GHz), Japan (27.5–28.28 GHz), and Korea (26.5–29.5 GHz). The proposed MIMO antenna design could be an excellent option for 26/28 GHz 5G NR n257, n258, and n260 bands under mm-wave wireless communication systems. [ABSTRACT FROM AUTHOR]

Summary: This article communicates a novel compact four‐element orthogonal cavity‐backed antenna for 5G applications with enhanced isolation. The proposed dumbbell‐shaped substrate integrated waveguide–multiple input/multiple output (SIW‐MIMO) antenna resonate at 5.25 GHz (sub‐6 GHz) based on vias and resonate at 27 GHz (mm‐wave) with copper filling vias using FR‐4 substrate. Both prototypes are separately designed, fabricated, and tested using same dimension (40 mm × 40 mm × 1.6 mm) as well as same radiating structure. Moreover, SIW MIMO antenna design performances are compared between FR‐4 and Rogers RT/Duroid substrate. Deployment of SIW technique in MIMO antenna minimizes the antenna footprint and mutual coupling without involving any decoupling structure. The antenna simulation characteristics of both operating bands are compared and validated with the measurement results. Furthermore, the MIMO diversity parameters are examined. [ABSTRACT FROM AUTHOR]

In this work, a compact, edge-fed modified rectangular patch size, monopole, and ultra-wideband antenna has been presented for their good suitability to millimeter (mm) wave and upper sub-6 GHz frequency range (FR2) for next-generation (5G and beyond) communications. The patch size enhancement approach has been utilized without affecting the original size of the substrate and rectangular patch. The technique provides better impedance matching at the designed frequency of 32.5 GHz. The minimum acceptable gain for an antenna to work well is 5 dBi. The proposed design achieves peak gain of 5.43 dBi and 10.86 dBi at two resonance frequencies of 32.5 GHz and 48.12 GHz within the specified ultra-wideband (UWB). The antenna has low loss as it is fabricated on a compact Rogers RT Duroid 5880 of thickness 1.6 mm. The measured reflection coefficients are found in good agreement with the simulated one. The resultant performance parameters like radiation pattern, reflection coefficient, peak gain, and − 10 dB bandwidth reveal that the antenna performs excellently within 26 to 40 GHz with excellent impedance matching at the resonance frequency. At higher frequencies, the time domain response of the proposed design is also presented. The RLC electrical equivalent circuit of the proposed design is presented at the end and validated using ADS software. [ABSTRACT FROM AUTHOR]

This work presents a parasitic wide band compact planar antenna for 5 G mm-wave applications. Besides having high bandwidth (5.22 GHz), the prospective antenna provides an enhanced gain of 5.23dBi which is achieved due to the reflector elements used in the design. The radiating element has a small planar rectangular geometry, with optimised dimensions of 0.342 λ0 × 0.199 λ0 × 0.005 λ0 at 28 GHz frequency of interest and has been designed and fabricated on a substrate of Rogers-RT/Duroid 5800 having a thickness of 0.147λ0 with loss-tangent of 9 × 10−4 and permittivity of 2.2. The proposed antenna operates in the frequency range of 24.71 to 29.93 GHz which falls under the n257 and n258 NR operating band of the FR2 band as defined by ITU for the millimetre wave 5 G spectrum. It is also affirmed in the study that the impedance bandwidth can be tuned by controlling the coupling gap between the radiating and parasitic patches. The measured results of the fabricated prototype of the patch are compared with the simulated results and the two results are in good agreement with each other. The pursuance of the proposed design in terms of gain, efficiency, radiation pattern, and wide bandwidth, qualifies the prototype as a viable option for mm-wave communication. [ABSTRACT FROM AUTHOR]

In this work, a novel multiple input multiple output (MIMO) array antenna system with a large bandwidth and high gain has been simulated, analyzed, fabricated, and measured. The proposed antenna is structured in 2 × 4 patch configuration along with a cross shaped ground plane loaded with four square and one circular shaped defect. The projected antenna occupies a total size of 4 3. 6 1 1 × 4 3. 6 1 1 × 0. 4 2 mm 3 . Several slots in an elliptic form have been added to the patches to achieve the required results in terms of wide bandwidth and high gain. The MIMO antenna array is fabricated and experimentally tested to confirm the simulation results. The suggested MIMO array antenna offers an impedance bandwidth of 22 GHz covering 22–44 GHz wide range of frequencies with a high peak gain of 17 dBi at 38 GHz. The designed MIMO antenna offers superior diversity performance and it supports several 5G NR bands n257/n258/n259/n260/n261 in the mm-wave spectrum. The suggested MIMO antenna supports 5G application bands that are deployed in UK, USA, China, Europe, Canada, India, and Europe. [ABSTRACT FROM AUTHOR]

This article presents a quad-element MIMO antenna designed for multiband operation. The prototype of the design is fabricated and utilizes a vector network analyzer (VNA-AV3672D) to measure the S-parameters. The proposed antenna is capable of operating across three broad frequency bands: 3–15.5 GHz, encompassing the C band (4–8 GHz), X band (8–12.4 GHz), and a significant portion of the Ku band (12.4–15.5 GHz). Additionally, it covers two mm-wave bands, specifically 26.4–34.3 GHz and 36.1–48.9 GHz, which corresponds to 86% of the Ka-band (27–40 GHz). To enhance its performance, the design incorporates a partial ground plane and a top patch featuring a dual-sided reverse 3-stage stair and a straight stick symmetrically placed at the bottom. The introduction of a defected ground structure (DGS) on the ground plane serves to provide a wideband response. The DGS on the ground plane plays a crucial role in improving the electromagnetic interaction between the grounding surface and the top patch, contributing to the wideband characteristics of the antenna. The dimensions of the proposed MIMO antenna are 31.7 mm × 31.7 mm × 1.6 mm. Furthermore, the article delves into the assessment of various performance metrics related to antenna diversity, such as ECC, DG, TARC, MEG, CCL, and channel capacity, with corresponding values of 0.11, 8.87 dB, −6.6 dB, ±3 dB, 0.32 bits/sec/Hz, and 18.44 bits/sec/Hz, respectively. Additionally, the equivalent circuit analysis of the MIMO system is explored in the article. It's worth noting that the measured results exhibit a strong level of agreement with the simulated results, indicating the reliability of the proposed design. The MIMO antenna's ability to exhibit multiband response, good diversity performance, and consistent channel capacity across various frequency bands renders it highly suitable for integration into multi-band wireless devices. The developed MIMO system should be applicable on n77/n78/n79 5G NR (3.3–5 GHz); WLAN (4.9–5.725 GHz); Wi-Fi (5.15–5.85 GHz); LTE5537.5 (5.15–5.925 GHz); WiMAX (5.25–5.85 GHz); WLAN (5.725–5.875 GHz); long-distance radio telecommunication (4–8 GHz; C-band); satellite, radar, space communications and terrestrial broadband (8–12 GHz; X-band); and various satellite communications (27–40 GHz; Ka-band). [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to present the design, fabrication and analysis of a wideband, enhanced gain 1 × 2 patch antenna array with a simple profile structure to meet the desired antenna traits, such as wide bandwidth, high gain and directional patterns expected for the upcoming fifth-generation (5G) wireless applications in the millimeter wave band. To enhance these parameters (bandwidth and gain), a new antenna geometry by using a T-junction power divider is presented. Design/methodology/approach: The theory behind this paper is connected with advancements in the 5G communications related to antennas. The methodology used in this work is to design a high gain array antenna and to identify the best possible power divider to deliver the power in an optimized way. The design methodology adopts several steps like the selection of proper substrate material as per the design specification, size of the antenna as per the frequency of operation and application-specific environment condition. The simulation has been performed on the designed antenna in the electromagnetic simulation tool (high-frequency structure simulator [HFSS]), and optimization has been done with parametric analysis, and then the final array antenna model is proposed. The proposed array contains 2-patch elements excited by one port adapted to 50 Ω through a T-junction power divider. The 1 × 2 array configuration with the suggested geometry helps to improve the overall gain of the antenna, and the implementation of the T-junction power divider provides enhanced bandwidth. The proposed array designed using a 1.6 mm thick flame retardant substrate occupies a compact area of 14 × 12.14 mm2. Findings: The prototype of the array antenna is fabricated and measured to validate the design concept. A good agreement has been reached between the measured and simulated antenna parameters. The measured results confirm its wideband and high gain characteristics, covering 24.77–28.80 GHz for S11= –10 dB with a peak gain of about 15.16 dB at 27.65 GHz. Originality/value: The proposed antenna covers the bandwidth requirements of the 26 GHz n258 band (24.25–27.50 GHz) to be deployed in the UK and Europe. The suggested antenna structure also covers the federal communications commission (FCC)-regulated 28 GHz n261 band (27.5–28.35 GHz) to be deployed in America and Canada. The low profile, compact size, simple structure, wide bandwidth, high gain and desired directional radiation patterns confirm the applicability of the suggested array antenna for the upcoming 5 G wireless systems. [ABSTRACT FROM AUTHOR]

Any wireless communication system's performance depends on channel parameters' accuracy. The classical Rayleigh and Nakagami-m research subjects remain vital even in the most modern millimeter-wave (mm-wave) applications. This research aims to create a generalized cumulative distribution function for describing random changes in wireless channels. It is vital to have a suitable channel representation model to represent varied fifth-generation applications to ease network implementation. This study provides mm-wave measurement data at 28 GHz carrier frequencies in line of sight and non-line of sight propagation. Lognormal, Nakagami, Gaussian, Weibull, and Rayleigh distributions outperform the proposed model's universal exponential density function. The experimental data verified the introduced method. [ABSTRACT FROM AUTHOR]

This work presents a symmetrical quad-element multiple-input multiple-output (MIMO) antenna that uses a feasible band for 5G millimeter waves at 38 GHz. The main radiator is a patch antenna with a rectangular shape, and the frequency it operates at is 38 GHz. Etching a three-element split-ring resonator (SRR) metamaterial unit cell onto the normal patch radiator allows for widening the resonance over the desired operating band. The suggested MIMO antenna is built on a Rogers RT5880 substrate material that measures 15 × 15 mm2, has a thickness of 0.8 mm, and has a dielectric constant of 2.2. The results of the measurements show that the antenna is capable of covering a frequency range from 37.3 to 39.3 GHz and can also achieve an inter-port isolation of greater than 20 dB between the antenna elements across both bands without the use of a complex decoupling structure. These are the results that were obtained when the antenna was tested. An equivalent circuit diagram of the electrical responses of the antenna is also presented to get insight into the proposed antenna. This schematic makes use of lumped components. The diversity performance parameters that were analyzed provide an envelope correlation coefficient that is less than 0.005, and a channel capacity loss that is less than 0.35 bits/s/Hz. All of these results fall well within the parameters that are considered acceptable norms. The findings provide evidence that the design is workable for the transmission of millimeter waves at 5G speeds. [ABSTRACT FROM AUTHOR]

Summary: This research suggests a compact uniplanar multiple‐input multiple‐output (MIMO) with four ports for n79/n46/millimeter‐wave (mm‐wave) applications. The size of the quad MIMO is only 30 × 30 × 0.8 mm3. MIMO system consists of four identical Z‐shaped radiators and common ground on the same plane and no decoupling structures are used for isolation. The system covers the bandwidth of 1.9 GHz (4.4–6.3 GHz) with a mid‐frequency of 5.6 GHz and also covers the high‐band frequencies ranging from 18 to 30 GHz with a bandwidth of 12 GHz. The suggested quad MIMO is fabricated on an FR‐4 board, and the measured outcomes are well in line with the simulated results. An isolation value of −11 dB has been achieved for mid‐band frequency and −24 dB has been attained for mm‐wave bands. Through the value of DG = 10 dB, ECC < 0.07, TARC < −3 dB, MEG < −5 dB, and the ratio of MEG = 1 dB, uniplanar quad MIMO shows acceptable MIMO diversity performance. The entire system was evaluated for the users' hand specific absorption rate (SAR) impacts and is within the limits. After the complete analysis of the miniature quad MIMO antenna, an 8‐port, and a 16‐port uniplanar MIMO are simulated for smartphone‐sized dielectric substrates and the performances were examined. The suggested MIMO system provides an efficient single‐layer MIMO antenna to 5G smartphones with high bandwidth and low SAR. The proposed quad MIMO systems are suitable for both the sub‐6 GHz band and the mm‐wave band. [ABSTRACT FROM AUTHOR]

In this article, a wideband aperture-coupled stacked-patch (ACSP) antenna on a flexible material for wireless applications at the WR-08 band is presented. It is shown that conventional designs of ACSP fail to achieve a large bandwidth at this frequency range, and a novel design methodology is proposed. We first propose a broadband impedance matching between the input port and the slot aperture based on two-section wideband distributed network (TWBDN). We also propose a TWBDN matched stacked patch (TMSP) network based on constant VSWR circles to attain broadband matching between the slot aperture and patches in an ACSP. To facilitate the measurements, a novel low-loss transition from a ground-signal-ground (GSG) port to a feedline is proposed. The proposed structure suppresses surface waves induced in the WR-08 band by placing via arrays around the feedline, which largely reduces unwanted resonance modes, thereby leading to uniformly high radiation efficiency across the band. The measured results of the fabricated antenna closely follow the simulations, and a measured peak gain of 7.95 dBi and $S_{11}\leq -10$ dB across a wide frequency range from 90 to 128.5 GHz is achieved. [ABSTRACT FROM AUTHOR]

This study presents a compact, wideband, 4 × 4 Butler matrix using a two‐metal‐layer thin‐film process for millimeter (mm)‐wave 5G radio applications. Size reduction techniques are thoroughly discussed for size and performance optimization. A size‐reduced quadrature coupler is designed with coplanar waveguide based length‐reduced branch lines using capacitive loading effect from the ground bridges. A compact crossover is designed for a return loss of 20 dB or more with negligible crosstalk over a wide frequency range. The circuit components are arranged in an optimized space, allowing negligible coupling between nearby elements. The Butler matrix is fabricated on a quartz substrate at the center frequency of 28 GHz. The fractional bandwidth is 15.4% at a 15‐dB return loss and insertion loss is measured in the range of 7.8–8.7 dB at the center frequency. The size of the core circuit is 3.375 × 2.100 mm2 ${\rm{m}}{{\rm{m}}}^{2}$, which corresponds to 0.469 × 0.292 λg2 ${\lambda }_{g}^{2}$. [ABSTRACT FROM AUTHOR]

In the mm-wave frequency band, the rectifier’s sensitivity is the bottleneck of a wireless-powered IoT transponder’s distance. At a meter’s distance, the received power is weak, and transistors in a front end of a wireless power receiver operate in the weak inversion region. This article presents a mathematical analysis of the mm-wave multi-stage rectifier in the low-power region. A design methodology of a 57–64-GHz fully integrated eight-stage rectifier with a bulk-drain connection in 40-nm CMOS technology is presented. Parasitic effects on a multi-stage rectifier are analyzed. Based on the analysis, an intrinsic threshold voltage modulation is applied to improve the sensitivity. A tree-type power splitter is also proposed for the RF power signal’s phase balance. With this method, the RF signal arrives at each stage with an equal phase, and its suppression at the output is improved by 16 dB. This mm-wave rectifier achieves −7.1-dBm input sensitivity at 57 GHz with 1-V dc output voltage. The overall sensitivity from 57 to 64 GHz is better than −4.5 dBm. Compared to other mm-wave silicon-based rectifier state of the arts, the proposed mm-wave rectifier achieves better sensitivity while maintaining a compact size. [ABSTRACT FROM AUTHOR]

This article describes a new compact parasitic patch-loaded transparent patch antenna with a copper ground plane for wireless-fidelity (Wi-Fi) and 5th generation (5G) millimeter-wave (mm-wave) applications. The proposed antenna uses two rectangular parasitic patches with a rectangular main radiation patch. The L-shaped strips are also added to the main radiation patch and one of the rectangular parasitic patches to cover both the sub-6 GHz and beyond 6 GHz mm-wave 5G frequency spectrums. The same transparent patch antenna with a solar ground plane is built, and its effect is parametrically studied alongside the integration of a polycrystalline silicon solar cell. The proposed antennas with a dimension of 42×30×2 mm3 are fabricated and experimentally validated for impedance and radiation characteristics. In terms of impedance bandwidth, the proposed copper ground plane antenna offers 36.89% (5.04-7.32 GHz), 5.15% (14.35-15.11 GHz), 6.23% (27.08-28.79 GHz), and 21.34% (31.64-39.81 GHz). The solar cell serves as both a photovoltaic generator and the ground plane of the transparent antenna. The same radiating patch with a solar ground plane offers impedance bandwidth of 36.03% (4.47-6.56 GHz), 14.4% (9.6-11.12 GHz), 2.55% (22.14-22.71 GHz), and 27.9% (28.79-39.05 GHz) for 5G applications. [ABSTRACT FROM AUTHOR]

In this paper, mm–wave low cost single and multiple input and multiple output (MIMO) planar microstrip antenna suitable for futuristic K–(18–26.5GHz), K a –band (26.5–40GHz) and local multipoint distribution systems (LMDS) applications is presented. The proposed structure achieves impedance bandwidth of 22.77 GHz (17.23–40GHz) with a peak gain of 13.69 dBi that notably covers the LMDS modern wireless communication application requirement. This achieves 5 dBi gain-bandwidth of 9.07 GHz (26.77–35.85GHz) and 17 GHz (19–36GHz) for single element and MIMO antenna with four elements in cascaded form respectively. The improvement in gain and impedance bandwidth is augmented after exciting multiple resonances of antenna by etching of two 3-armed H-shaped slots (3-AHSS) and inverted T-shaped slots (ITSS) symmetrically in the patch. With these etchings the copper losses and vertical components of current are controlled. The fabricated prototype of size 37 × 15 m m 2 is connected through a mm–wave supporting frequency connector of 2.92 mm and 50 Ω coaxial type to Vector Network Analyzer (VNA) Bench of modal number Rohde and Schwarz (ZNB–40) for measurement of performance parameters and it is found to be in good promise with simulated results. [ABSTRACT FROM AUTHOR]

A high-isolation wideband MIMO (Multiple-Input Multiple-Output) antenna, shaped like a palm tree, is designed for 5G wireless communication purposes. The propounded MIMO antenna is formulated on an FR4 substrate, featuring a quartet of ports and adhering to a precise dimension of 45 × 50 × 0.8 mm3. A detailed analysis of the proposed high isolation wideband palm tree shaped MIMO antenna, considering its bandwidth, gain, isolation, radiation patterns, and diversity performance metrics such as diversity gain, channel capacity loss, mean effective gain, and total active reflection coefficient, is presented. The results obtained from simulations and measurements demonstrate good agreement, indicating the antenna's effectiveness for intended applications. Indeed, an extensive bandwidth covering a range of 11.6 GHz from 23.4 GHz to 35 GHz is achieved by demonstrating superb reflection coefficient. Additionally, the design reports remarkable isolation and a peak gain of 12.4 dB, indicating its ability to enhance signal strength. One of the most notable features of this MIMO antenna is its coverage of multiple 5G bands, making it ideal for use in various geographical regions, including the USA and Canada (27.5–28.35 GHz, 37.0–37.6 GHz, and 37.6–40.0 GHz), China (24.75–27.5 GHz), Korea (28–39 GHz), Japan (27–29.5 GHz) and Sweden (26 GHz). [ABSTRACT FROM AUTHOR]

In this work, the automated design of a power amplifier circuit in a 130 nm BiCMOS technology operating in the 220 GHz to 260 GHz frequency range is presented. The design automation process is based on the RapidIP approach, which enables the evaluation, rating and optimisation of thousands of different circuit topologies within only a few minutes. In total 6. 13 ⋅ 1 0 5 optimisation steps and 2. 6 ⋅ 1 0 4 different circuit topologies have been explored within an overall runtime of 23 min. According to post-layout simulations, the amplifier achieves a saturated output power of 9 dBm with a peak power-added efficiency of 2.8% and a 3 dB-bandwidth of 55 GHz. [ABSTRACT FROM AUTHOR]

This paper presents a high-gain and ultra-wideband antipodal Vivaldi antenna (AVA) with vias-loaded linearized edges for 5G millimeter-wave applications. By replacing the traditional exponential tapered edge by linear tapered slot (LTS), the side-lobe is obviously descended. Moreover, metal vias are loaded on radiation edges, more energy in the main radiation direction is constrained and the antenna directivity and gain performance are improved. A prototype of the proposed antenna was designed, fabricated and measured. The measurements agree well with the simulations, which certify the new way for miniaturization and easier fabrication of the propose antenna. The measured results show that the antenna achieves a peak gain up to 12.1 dBi at 36 GHz and gain of 10.8 ± 1.3 dBi in the operating range from 22 to 40 GHz, where the reflection coefficient is less than −10 dB. The gain increment is up to 2 dB compared with the conventional AVA. Due to characteristics like high-gain, ultra-wideband, and compact size, it is highly well-suited for 5G millimeter-wave applications. [ABSTRACT FROM AUTHOR]

A phased-array fed reflector antenna system is presented which can be used for mm-wave base station applications. The proposed system is designed to support massive-multi-input–multi-output (MIMO) scenarios within a wide coverage ($\pm 30^\circ $) in the azimuth plane and a limited coverage at the elevation plane. A design and characterization methodology has been established to optimize the system for the operation in various line-of-sight conditions by adopting the maximum-ratio-transmission (MRT) and zero-forcing (ZF) MIMO algorithms. A two-user MIMO case study has been considered for the evaluation of the key system performance metrics, i.e., the effective isotropic radiated power, power consumption, signal-to-noise-ratio (SNR), and signal-to-interference-plus-noise-ratio (SINR). This study demonstrates that the phased-array fed reflector concept has a major advantage over traditional direct-radiating phased-array (DRPA) antennas to reduce energy consumption. In the present example, it requires 12–14 dB less transmitted power as compared with the MRT-beamformed DRPAs for the same SNR, and 26–27 dB less transmitted power relatively to ZF-beamformed DRPA systems for the same SINR. A prototype, employing a 55 cm diameter torus reflector and operating at 28 GHz-band, has been manufactured and tested. The measurement results agree well with simulations. [ABSTRACT FROM AUTHOR]

This research work presents the analysis, design, and characterization of a concept for an mm-wave divide-by-4 frequency divider utilizing an extended true single-phase clock (E-TSPC) and a TSPC divide-by-2 stage. The divider operates from 16 to 70 GHz from a 0.8-V supply with the highest power consumption of 0.35 mW. Operating frequencies up to 53 GHz were reached with a supply voltage of only 0.5 V at 0.12-mW power consumption. The self-resonance frequency of the circuit is adjustable through backgate biasing from 40 up to 70 GHz at 0.9-V supply, allowing a reduction in the required input power in this frequency range. Locking ranges up to 114% have been measured by changing only the backgate voltage. The circuit design is illustrated in detail and supported with original analysis and an explicit expression to calculate the self-oscillation frequency of the E-TSPC divider. The presented circuit was fabricated on a 22-nm fully depleted silicon-on-isolator complementary metal–oxide–semiconductor (CMOS) technology and occupies an active area of $3.4 ~\mu \text{m}^{2}$. The circuit requires the lowest power consumption and area among state-of-the-art RF frequency dividers, while it demonstrates the second widest adjustable operating frequency range and the second highest self-resonance frequency for CMOS D-flip-flop frequency dividers. [ABSTRACT FROM AUTHOR]

In this communication, a dual-band shared aperture antenna is presented. The proposed antenna achieves dual-band operation by housing both a low-frequency patch antenna array and a high-frequency reflectarray in the same aperture area. The two different antenna types are combined into a single-antenna product without any significant performance loss. The antenna has a layered structure that allows the low-frequency antenna array to have both a sufficient impedance bandwidth and realized gain. The antenna has a shared aperture since the high-frequency reflectarray has unit elements within the area of the low-frequency patch antenna array. This allows the antenna to achieve a good realized gain in the high-frequency band. The proposed antenna is fabricated and measured. The prototype is designed for S- and Ka-bands resulting in a frequency ratio of 7.37. The shared aperture size is 156 mm $\times156$ mm $\times4.624$ mm ($1.82\lambda \times 1.82\lambda \times 0.05\lambda $ at S-band and $13.4\lambda \times 13.4\lambda \times 0.40\lambda $ at Ka-band). Measurements show the impedance bandwidth to be 200 MHz (6%) and 5.1 GHz (20%) and the peak realized gain to be 13.70 and 27.65 dBi at 3.5 and 25.8 GHz, respectively. A very good agreement between the simulated and measured results is observed. [ABSTRACT FROM AUTHOR]

In this paper, a novel miniaturized planar antipodal Vivaldi antenna (AVA) with high gain and back radiation reduction for 5G millimeter‐wave (mm‐Wave) communication is presented. First, due to the use of the gradual corrugated edges (GCE), the operating band of the antenna is extended in the direction of lower frequencies and the overall gain is also improved as well. Second, its gain of the antenna is better enhanced at the high frequency band through I‐Shape Metal Director (IMD). Lastly, to further reduce the back radiation, the split ring resonance branches (SRB) are added to the ground. The antenna front‐back ratio has improved considerably to over 20 dB. Meanwhile the antenna gain is improved further. Furthermore, a prototype antenna array was fabricated and the measurement results clearly show that the antenna array gain varies in the range of 15.86–16.43 dB when operating in the 5G millimeter wave band (24.75–28.35 GHz). [ABSTRACT FROM AUTHOR]

• The dielectric properties of silicates are frequency independent from 5 GHz up to around 40 GHz • The dielectric properties of silicates show two resonances at higher frequencies - the boson peak around 2 THz and the Si-O-Si bending vibration around 13 THz • Constructing Cole-Cole plots at THz provided insight into the boson peak and ionic resonance relaxation dynamics [Display omitted] In this paper, a broadband measurement of the dielectric properties of silicates has been done to cover the seldom characterized mm-wave spectrum and the low THz spectrum. The dielectric properties, i.e. loss and permittivity, show a frequency independent response up to approximately 40 GHz and the loss monotonically increases to the THz frequency range. Two resonance peaks appear at THz frequencies: the first is the boson peak, and the second one corresponds to the ionic resonance of the network former, which in this case is silicon. Even though the materials belong to different groups in the silicate family (crystalline and non-crystalline, with different levels of purity), they seem to have the same overall tendency in the dielectric properties. Argand plots are used for the first time at THz frequencies to provide physical insight into the boson peak and ionic resonance. The complex plane analysis reveals details on the polarization mechanisms underlying silicate network vibrations through direct visualization of their characteristic signatures, and simplifies the process of modeling the dielectric response, leading to a better fit. [ABSTRACT FROM AUTHOR]

• Compact Tunable negative Metamaterial for enhanced 5G Communication. • Frequency-Tunable Tri-Square Split Ring Resonator for Bandwidth Optimization. • Empowering 5G with Double Negative (DNG) and epsilon metamaterial (ENG) Properties. • Implement the proposed metamaterial with a new Y-shaped antenna to improve the antenna performance. One of the leading candidates for the next fifth generation of (5G) and body-centric wireless communications is millimeter-wave frequencies. In this study, a wideband tunable metamaterial (MTM) consisting of T-H shaped symmetric resonator is presented for body-centric applications operating in the millimeter-wave frequency band centered at 28 GHz. The characteristics of the proposed MTM are examined through wave propagation in both Z and X directions. It has a wide operating frequency range of 5.6 GHz for waves travelling along the Z-axis, with DNG characteristics at 26.2 GHz resonance frequency. However, it represents a negative epsilon metamaterial (ENG) range during X-axis wave propagation in the 25–29.4 GHz frequency range. The metamaterial is constructed on a Rogers (RT-5880) substrate and has a compact size, with overall dimensions of 0.420 λ o × 0.420 λ o. A proposed Y-shaped antenna is developed with a compact size of 1.36 λ o × 1.82 λ o to cover the 5G at 28 GHz. The single-Y-shaped antenna consists of a radiating patch, Rogers substrate, full ground plane, air bandgap (ABG), and array of DNG MTM. Thus, the array of MTM has been applied to validate the effect in the overall antenna performance such as gain which has been increased from 5.5 dBi to 8.5 dBi. The experimental, simulated results, and equivalent circuit model using Advanced Design Software (ADS) for validation functions showed that the completed results are comparable. The proposed mm-wave metamaterial is expected to be a good candidate for modern 5G wireless communication system components, especially to enhance the antenna gain and isolation. The proposed antenna loaded with MTM is a suitable contender for the upcoming 5G mm wave mobile handheld devices. [ABSTRACT FROM AUTHOR]

Low relative permittivity plastic elliptical lenses in combination with integrated focal plane arrays are a promising solution to be used in the future mm- and sub-mm-wave systems. Their appeal lies in the availability of materials with moderate loss and lightweight, and the possibility to use cost-effective manufacturing techniques. However, the achievable scanning angular range is relatively small with low permittivity lenses. In this article, we explore the use of dielectric gratings with modulated height integrated in the lens material, with the aim of enlarging the steering angle. The dielectric gratings synthesize a tilted feed pattern, reducing the reflection loss and spillover when illuminating the lens off-focus. A quasi-analytic approach based on the Floquet mode analysis of the gratings is used to synthesize the grating profile. This method is combined with an analysis in reception of the lens antenna. A wideband prototype in $G$ -band (140–220 GHz) has been fabricated, achieving a field of view of ±25° with gain >30 dBi. [ABSTRACT FROM AUTHOR]

Stacked nanosheet nFETs considering a six-stack four-finger transistor array are studied and optimized by validated TCAD simulation. Stacked Si nanosheet (NS) nFETs have lower parasitics than nFinFETs in the same six-fin/stack four-finger transistor array layout. With the same electron mobility, back-end-of-line (BEOL), equivalent oxide thickness (EOT) of 1.4 nm, and gate length of 30 nm, the stacked Si NSs have $1.1\times $ cut-off frequency (240 versus 215 GHz) and $1.15\times $ maximum oscillation frequency (290 versus 251 GHz) when compared to FinFETs due to larger transconductance increase than capacitance increase and output conductance decrease. With the optimized EOT of 0.8 nm and gate length of 18 nm, the stacked Si NSs can achieve cut-off frequency of 340 GHz and maximum oscillation frequency of 370 GHz. Furthermore, considering the higher electron mobility on {100} surfaces of NSs than {110} sidewalls of FinFETs as suggested by the ${I} _{D}$ – ${V}_{\text {GS}}$ fitting, the cut-off frequency and maximum oscillation frequency of stacked Si NSs can reach 380 and 390 GHz, respectively. [ABSTRACT FROM AUTHOR]

All-metal 3D printing fabrication technologies provide an attractive alternative for direct manufacturing of waveguide components due to fast and cost-effective prototyping and the possibility to fabricate geometries which cannot be fabricated with traditional machining techniques. In radio astronomy, waveguide components in radio receivers are operated at cryogenic temperatures and inside a cryostat under vacuum conditions. In this paper, we report on the design, fabrication by 3D printing and testing at room and cryogenic temperatures of a corrugated horn to be used in astronomical receivers operating in the 35–50-GHz band. [ABSTRACT FROM AUTHOR]

A new scalable small‐signal model for 0.1 μm AlGaN/GaN HEMT up to 110 GHz is presented in this paper. The taps between the gate/drain manifold and fingers on the device has been investigated and included in the equivalent circuit. In addition, to ensure high scalability, a set of scaling rules are presented. A novel extraction procedure for extrinsic capacitances using full‐wave electromagnetic (FW‐EM) method has been introduced along with corresponding structures used for EM simulation. The nonlinear dependence of the extrinsic inductances on the gate‐width has been accounted for by a new scaling rule, which can be used to extract their value from measurement data. To guarantee the stability of the scaling coefficients, two devices with different gate‐width have been utilized for their generation. The proposed scalable model has been verified using 0.1 μm AlGaN/GaN HEMT devices with different gate‐widths and different gate‐fingers. The experiment results show good agreement between model and measurement S‐parameters up to 110 GHz. [ABSTRACT FROM AUTHOR]

In this work, a stochastic 3-D user shadowing model is presented, which can be used in the frequency range from 28 to 34 GHz. To characterize the user shadowing pattern, new metrics of shadowed cumulative distribution function (SCDF) and user shadowed intensity ratio (USIR) are proposed. The user shadowing model is based on measurements with 18 subjects of different heights and genders. For simplicity, the user shadowing pattern is divided into four regions based on the mean shadowing pattern obtained from the measurements. Each of the spatial regions is modeled as a stochastic process, which follows the Gaussian distribution. It has been shown that any horizontally polarized mobile antenna is compatible with the presented model. The proposed user shadowing pattern model can be directly used for fifth-generation (5G) mm-wave ray tracing or link simulations. [ABSTRACT FROM AUTHOR]

Superconducting qubits are widely used in quantum computing research and industry. We describe a superconducting kinetic inductance qubit (and introduce the term Kineticon to describe it) operating at W-band frequencies with a nonlinear nanowire section that provides the anharmonicity required for two distinct quantum energy states. Operating the qubits at higher frequencies may relax the dilution refrigerator temperature requirements for these devices and paves the path for multiplexing a large number of qubits. Millimeter-wave operation requires superconductors with relatively high Tc, which implies high gap frequency, 2Δ/h, beyond which photons break Cooper pairs. For example, NbTiN with Tc =15 K has a gap frequency near 1.4 THz, which is much higher than that of aluminum (90 GHz), allowing for operation throughout the millimeter-wave band. Here we describe a design and simulation of a W-band Kineticon qubit embedded in a 3-D cavity. We perform classical electromagnetic calculations of the resulting field distributions. [ABSTRACT FROM AUTHOR]

A new compact 1 × 4 microstrip patch antenna array design for future 5G applications is presented in this paper. The proposed antenna array consists of square slot loaded with four radiating patch elements. The corporate feed network has been implemented for the excitation of the array. The feed line is connected to the square slot patch through a quarter-wave transformer matching network. The proposed array is designed on an FR-4 substrate with a dielectric constant of 4.4, thickness of 1.6 mm and loss tangent (tan δ) of 0.02. It has a compact dimension of 9.590 × 17.802 × 1. 6 m m 3 . The proposed structure has been designed and simulated by using commercially available HFSS software. The simulated results (reflection coefficient, gain, efficiency, radiation pattern) are verified through the measurement process to confirm the validity of the design concept. The measurement results are in good agreement with the simulated results. The proposed structure resonates at 38.1 GHz with a − 10 dB impedance bandwidth of about 3700 MHz (36.5 GHz to 40.2 GHz). The reflection coefficient at 38.1 GHz is − 34 dB, with a maximum gain of 7.81 dB. The proposed square slot loaded patch antenna array is very promising for 5G communications at 38 GHz band (37–40 GHz). [ABSTRACT FROM AUTHOR]

Nowadays most discussed technology is mm-wave and 5G communication. The requirement of 5G technology is high bandwidth, high data rate, and low latency. To fulfil these requirements for the current growth in mobile communication multiple input multiple output antenna is used. This bibliometric paper throws light on the various methods used to improve mutual coupling between multiple antennas. Various mutual coupling reduction techniques that are used in MIMO antennas like Dielectric resonator antenna, Electromagnetic Bandgap Structure, Neutralization lines, Defected Ground Structures, Metamaterial, etc. are explained. Scopus database is used for this bibliometric review on mmwave MIMO 5G technology from the year 2016 to 20th December 2020. This paper elaborates, a bibliometric survey of MIMO antennas used in 5G technology for an mm-wave frequency range. [ABSTRACT FROM AUTHOR]

We investigate the realistic propagation conditions effects on wireless physical layer security, which are different from classical Rice and Rayleigh fading. Specifically, we study how the superposition of a number of dominant specular waves and diffusely propagating components impacts the achievable secrecy performance. We derive analytical expressions for the secrecy outage probability and the average secrecy capacity, which have similar complexity to other alternatives in the literature derived for simpler fading models. We provide very useful insights on the impact on physical layer security of (i) the number; (ii) the relative amplitudes and (iii) the overall power of the dominant specular components. We show that it is possible to obtain remarkable improvements on the system secrecy performance when: (a) the relative amplitudes of the dominant specular components for the legitimate channel are more unbalanced compared to those of the eavesdropper's channel, and (b) the power of the dominant components for the main channel is significantly larger than the power of the dominant components for the wiretap channel. [ABSTRACT FROM AUTHOR]

This article presents a reflectometer-based on-chip dielectric sensor with integrated transducers at 240 GHz. The chip simplifies the measurement of a vector network analyzer (VNA) to sense the incident and reflected waves by using two heterodyne mixer-based receivers with a dielectric sensing element. Radio frequency (RF) and local oscillator (LO) submillimeter waves are generated by two frequency multiplier chains, respectively. Two back-to-back identical differential side-coupled directive couplers are proposed to separate the incident and reflected signals and couple them to mixers. Both transmission line and coplanar stripline transducers are proposed and integrated with reflectometer to investigate the sensitivity of dielectric sensors. The latter leads to a larger power variation of the reflectometer by providing more sufficient operating bands for the magnitude and phase slope of $S_{11}$. The readout of the transducers upon exposure to liquids is performed by the measurement of their reflected signals using two external excitation sources. The experimental dielectric sensing is demonstrated by using binary methanol–ethanol mixture placed on the proposed on-chip dielectric sensor in the assembled printed circuit board. It enables a maximum 8 dB of the power difference between the incident and reflected channels on the measurement of liquid solvents. Both chips occupy an area of 4.03 mm2 and consume 560 mW. Along with a wide operational frequency range from 200 to 240 GHz, this simplified one-port-VNA-based on-chip device makes it feasible for the use of handle product and suitable for the submillimeter-wave dielectric spectroscopy applications. [ABSTRACT FROM AUTHOR]

A two element multiband multiple-input multiple-output (MIMO) antenna system with low specific absorption rate is proposed for Ka-band space satellite, millimeter-wave (mm-wave), fifth-generation (5G), and future sixth-generation (6G) wireless communication applications. The essential characteristics of both 5G and future 6G communications can be fulfilled by the proposed MIMO antenna design. The proposed MIMO antenna system has significant advantage of covering four relevant and usable frequency bands, i.e., 16 GHz, 25.5 GHz, 28 GHz, and 32 GHz used for the above mentioned applications. The design of the presented antenna looks like a vertical Yagi-Uda antenna with L-shaped ladder. Moreover, two circular slots and a slotted vertical stub are etched in a partially shared ground. The complete electrical dimension of the presented antenna is 6.8 λ 0 × 5. 7 λ 0 × 0. 068 λ 0 , calculated at resonating frequency 25.5 GHz, where λ 0 is wavelength in free space. The geometry of the presented antenna is fabricated using Rogers RO4350TM with dielectric constant (ϵ r) of 3.48, a loss tangent of 0.0025, and the substrate thickness of 0.8 mm. The presented MIMO antenna is excited with a 3 mm wide microstrip feed line having 50 Ω characteristics matched impedance. In terms of performance, the proposed antenna has achieved a reflection coefficient < - 10 dB, and isolation < -15 dB in all the resonating bands, radiation efficiency varies 72%–84%, impedance bandwidth of 4.6 GHz, 1.5 GHz, 1.11 GHz, and 7.5 GHz, and realized gain of 10.18, 12.05, 13.07, & 5.55 dBi is also achieved at frequencies 16 GHz, 25.5 GHz, 28 GHz, and 32 GHz. The achieved values for various MIMO matrices are envelope correlation coefficient > 0.0048, diversity gain of 9.98 dB, channel capacity loss < 0.00023 bits/s/Hz, and mean effective gain < -6 dB. The simulated results obtained by ANSYS I 2022 R2 (HFSS) and the experimental results measured by vector network analyzer (VNA) show a good agreement. [ABSTRACT FROM AUTHOR]

We present pure rotational transitions of the rare iron monoxide isotopologues. 57 F e 16 O , 58 F e 16 O and 56 F e 18 O in their lowest spin states 5 Δ 4 . For 57 F e 16 O , the rotational spectrum reveals hyperfine splitting due to the nuclear spin of I ( 57 F e) = 1 / 2. We use Dunham-like parameters to analyse the new laboratory data together with data from the literature. In particular, we are able to derive the Born–Oppenheimer breakdown parameters Δ U 01 F e = − 9.886 (24) and Δ U 01 O = − 10.761 (67) and the corresponding equilibrium bond length of r e B O = 1.6160302 (20) 10 − 10 m . With these new accurate molecular parameters line positions on a sub-MHz accuracy level can be calculated, including those of the radioactive isotopologue 60 F e 16 O . The new data allow for an astronomical search for the rare F e O isotopologues using sensitive radio telescopes, like the Atacama Large Millimetre/submillimetre Array. [ABSTRACT FROM AUTHOR]