A Low-Profile Circularly Polarized Millimeter-Wave Broadband Antenna Analyzed with a Link Budget for IoT Applications in an Indoor Scenario.

Broadband antennas with a low-profile generating circular polarization are always in demand for handheld/ portable devices as CP antennas counter multipath and misalignment issues. Therefore, a compact millimeter-wave antenna is proposed in this article. The proposed antenna structure comprises two circular rings and a circular patch at the center. This structure is further embedded with four equilateral triangles at a 90° orientation. The current entering the radiator is divided into left and right circular directions. The equilateral triangles provide the return path for current at the differential phase of ±90°, generating circular polarization. Structural development and analysis were initially performed through the characteristic mode theory. It showed that Modes 1 to 4 generated good impedance matching from 20 to 30 GHz and Modes 1 to 5, from 30 to 40 GHz. It also demonstrated the summation of orthogonal modes leading to circular polarization. The antenna-measured reflection coefficient |S11| > 10 dB was 19 GHz (23-42 GHz), and the axial ratio at -3 dB was 4.2 GHz (36-40.2 GHz). The antenna gain ranged from 4 to 6.2 dBi. The proposed antenna was tested for link margin estimation for IoT indoor conditions with line-of-sight (LOS) and non-line-of-sight (NLOS) conditions. The communication reliability with co- and cross-polarization was also studied under these conditions, and the results proved to be satisfactory.

Gender differences in association between expiratory dynamic airway collapse and severity of obstructive sleep apnea.

OBJECTIVES: Repetitive unbalances and tensions generated by inspiratory efforts against an obstructive upper airway during sleep predispose the development of expiratory central airway collapse. In addition, structures of the upper airway between men and women have differences and could be the reasons for differences in obstructive sleep apnea (OSA) prevalence between genders. The present study aimed to evaluate the association between parameters of expiratory dynamic tracheal collapse measured using chest multidetector CT and objectively measured OSA severity between men and women. MATERIALS AND METHODS: A total of 901 participants who underwent chest CT and overnight in-home polysomnography from the Korean Genome and Epidemiology Study were cross-sectionally analyzed (women: 46.2%). The participants were divided into three groups based on OSA severity by apnea-hypopnea index (AHI). Multivariate linear regression analysis was performed to determine the effects of central airway collapse after adjustment for cardiovascular-related covariates. RESULTS: In a multivariate analysis, percentages of expiratory lumen structure reductions involving area, diameter, and perimeter were associated with AHI (all p values < 0.05) and with OSA severity (moderate-to-severe OSA than no OSA: ß = 3.30%, p = 0.03; ß = 2.05%, p = 0.02; ß = 1.97%, p = 0.02, respectively) in women, whereas men had only a greater percentage of expiratory wall thickness reduction in moderate-to-severe OSA than no OSA (ß = 0.72%, p = 0.003). In addition, women with both mild OSA and moderate-to-severe OSA had higher expiratory tracheal collapse than men without OSA, and a moderate effect of sex was observed (p for interaction = 0.007). CONCLUSION: The expiratory dynamic tracheal collapse was independently associated with severity of OSA in women than in men. CLINICAL RELEVANCE STATEMENT: Differences of pharyngeal structures and inherent features of airways by genders may affect the dissimilarities in vulnerability to sleep apnea between men and women. KEY POINTS: • The expiratory dynamic tracheal collapse was independently associated with severity of OSA in women than in men. • Women with over mild OSA had higher expiratory tracheal collapse than men without OSA, and moderate effect of sex was observed. • Structural differences of airway may affect differences in susceptibility of sleep apnea between genders.

A Compact Dual-Band Millimeter Wave Antenna for Smartwatch and IoT Applications with Link Budget Estimation.

Advancement in smartwatch sensors and connectivity features demands low latency communication with a wide bandwidth. ISM bands below 6 GHz are reaching a threshold. The millimeter-wave (mmWave) spectrum is the solution for future smartwatch applications. Therefore, a compact dual-band antenna operating at 25.5 and 38 GHz is presented here. The characteristics mode theory (CMT) aids the antenna design process by exciting Mode 1 and 2 as well as Mode 1-3 at their respective bands. In addition, the antenna structure generates two traverse modes, TM10 and TM02, at the lower and higher frequency bands. The antenna measured a bandwidth (BW) of 1.5 (25-26.5 GHz) and 2.5 GHz (37-39.5 GHz) with a maximum gain of 7.4 and 7.3 dBi, respectively. The antenna performance within the watch case (stainless steel) showed a stable |S11| with a gain improvement of 9.9 and 10.9 dBi and a specific absorption rate (SAR) of 0.063 and 0.0206 W/kg, respectively, at the lower and higher bands. The link budget analysis for various rotation angles of the watch indicated that, for a link margin of 20 dB, the antenna can transmit/receive 1 Gbps of data. However, significant fading was noticed at certain angles due to the shadowing effect caused by the watch case itself. Nonetheless, the antenna has a workable bandwidth, a high gain, and a low SAR, making it suitable for smartwatch and IoT applications.

A Frequency Reconfigurable MIMO Antenna with Bandstop Filter Decoupling Network for Cognitive Communication.

A compact reconfigurable MIMO antenna was developed for cognitive radio applications in this research work. A bandstop filter-based decoupling network was employed in this MIMO antenna to keep mutual coupling at a minimum. A single PIN diode was connected in the filter configuration for the purpose of reconfiguration. Controlling the ON/OFF conditions of the PIN diode, it became possible to achieve a MIMO operating frequency of 4.75 GHz in mode 1 and 1.77 GHz in mode 2, respectively. At 4.75 GHz, isolation was 42.68 dB, while at 1.77 GHz, isolation was 26.52 dB. The proposed reconfigurable MIMO antenna achieved a peak gain and radiation efficiency of 6.63 dBi and 92.04 percent in mode 1 and 4.41 dBi and 89.64 percent in mode 2. MIMO characteristics such as an envelope correlation coefficient (ECC) less than 0.253, diversity gain (DG) greater than 9.675 dB, a mean effective gain (MEG) measurement ratio of less than 0.00388 dB, and channel capacity loss (CCL) of less than 0.06528 bits/s/Hz were measured for both operational frequency bands. To make it simple to integrate into small wireless devices, the overall size of the antenna is limited to 48 mm×24 mm 0.28 λ0×0.12 λ0.

Flexible Antennas for a Sub-6 GHz 5G Band: A Comprehensive Review.

The ever-increasing demand and need for high-speed communication have generated intensive research in the field of fifth-generation (5G) technology. Sub-6 GHz 5G mid-band spectrum is the focus of the researchers due to its meritorious ease of deployment in the current scenario with the already existing infrastructure of the 4G-LTE system. The 5G technology finds applications in enormous fields that require high data rates, low latency, and stable radiation patterns. One of the major sectors that benefit from the outbreak of 5G is the field of flexible electronics. Devices that are compact need an antenna to be flexible, lightweight, conformal, and still have excellent performance characteristics. Flexible antennas used in wireless body area networks (WBANs) need to be highly conformal to be bent according to the different curvatures of the human body at different body parts. The specific absorption rate (SAR) must be at a permissible level for such an antenna to be suited for WBAN applications. This paper gives a comprehensive review of the current state of the art flexible antennas in a sub-6 GHz 5G band. Furthermore, this paper gives a key insight into the materials for a flexible antenna, the parameters considered for the design of a flexible antenna for 5G, the challenges for the design, and the implementation of a flexible antenna for 5G.

Flexible UWB and MIMO Antennas for Wireless Body Area Network: A Review.

In recent years, there has been a surge of interest in the field of wireless communication for designing a monitoring system to observe the activity of the human body remotely. With the use of wireless body area networks (WBAN), chronic health and physical activity may be tracked without interfering with routine lifestyle. This crucial real-time data transmission requires low power, high speed, and broader bandwidth communication. Ultrawideband (UWB) technology has been explored for short-range and high-speed applications to cater to these demands over the last decades. The antenna is a crucial component of the WBAN system, which lowers the overall system's performance. The human body's morphology necessitates a flexible antenna. In this article, we comprehensively survey the relevant flexible materials and their qualities utilized to develop the flexible antenna. Further, we retrospectively investigate the design issues and the strategies employed in designing the flexible UWB antenna, such as incorporating the modified ground layer, including the parasitic elements, coplanar waveguide, metamaterial loading, etc. To improve isolation and channel capacity in WBAN applications, the most recent decoupling structures proven in UWB MIMO technology are presented.

Design and Analysis of Super Wideband Antenna for Microwave Applications.

In this article, a compact concentric structured monopole patch antenna for super wideband (SWB) application is proposed and investigated. The essential characteristics of the designed antenna are: (i) to attain super-wide bandwidth characteristics, the proposed antenna is emerged from a traditional circular monopole antenna and has obtained an impedance bandwidth of 38.9:1 (ii) another important characteristic of the presented antenna is its larger bandwidth dimension ratio (BDR) value of 6596 that is accomplished by augmenting the electrical length of the patch. The electrical dimension of the proposed antenna is 0.18λ×0.16λ (λ corresponds to the lower end operating frequency). The designed antenna achieves a frequency range from 1.22 to 47.5 GHz with a fractional bandwidth of 190% and exhibiting S11 < -10 dB in simulation. For validating the simulated outcomes, the antenna model is fabricated and measured. Good conformity is established between measured and simulated results. Measured frequency ranges from 1.25 to 40 GHz with a fractional bandwidth of 188%, BDR of 6523 and S11 < -10 dB. Even though the presented antenna operates properly over the frequency range from 1.22 to 47.5 GHz, the results of the experiment are measured till 40 GHz because of the high-frequency constraint of the existing Vector Network Analyzer (VNA). The designed SWB antenna has the benefit of good gain, concise dimension, and wide bandwidth above the formerly reported antenna structures. Simulated gain varies from 0.5 to 10.3 dBi and measured gain varies from 0.2 to 9.7 dBi. Frequency domain, as well as time-domain characterization, has been realized to guide the relevance of the proposed antenna in SWB wireless applications. Furthermore, an equivalent circuit model of the proposed antenna is developed, and the response of the circuit is obtained. The presented antenna can be employed in L, S, C, X, Ka, K, Ku, and Q band wireless communication systems.

Split Ring Resonator-Based Bandstop Filter for Improving Isolation in Compact MIMO Antenna.

The ever-growing expectation for high data rates has led to the introduction of multiple-input multiple-output (MIMO) technologies to wireless connectivity. Such a system requires an MIMO antenna with high isolation. At the same time, the MIMO dimension should not be compromised for achieving high isolation. Thus, isolation techniques that do not allow an increase in dimension need to be fostered for MIMO antenna design. In this paper, a novel low-profile, miniaturized MIMO antenna with high isolation was developed considering a split ring resonator (SRR)-based bandstop filter as a decoupling network. The bandstop filter was designed with a unit cell split ring resonator structure and was deployed between two closely spaced monopole MIMO antenna elements to obtain isolation as high as 39.25 dB at 2.61 GHz. Two open-circuit stub lines were attached with the MIMO feeding network to achieve good impedance matching at resonance frequency. The proposed antenna exhibited a peak gain of 3.8 dBi and radiation efficiency of 84%. It had a low envelop correlation coefficient (ECC < 0.12), high diversity gain (DG > 9.95 dB), low mean effective gain ratio (MEG 1/MEG 2 < 0.05 dB), and low channel capacity loss (CCL < 0.042 bits/s/Hz) at resonance frequency. The overall antenna dimension was restricted to 44 mm ×22 mm (0.38 λ0×0.19 λ0) for its easy integration in compact wireless devices.

Automated Detection of Covid-19 from Chest X-ray scans using an optimized CNN architecture.

The novel coronavirus termed as covid-19 has taken the world by its crutches affecting innumerable lives with devastating impact on the global economy and public health. One of the major ways to control the spread of this disease is identification in the initial stage, so that isolation and treatment could be initiated. Due to the lack of automated auxiliary diagnostic medical tools, availability of lesser sensitivity testing kits, and limited availability of healthcare professionals, the pandemic has spread like wildfire across the world. Certain recent findings state that chest X-ray scans contain salient information regarding the onset of the virus, the information can be analyzed so that the diagnosis and treatment can be initiated at an earlier stage. This is where artificial intelligence meets the diagnostic capabilities of experienced clinicians. The objective of the proposed research is to contribute towards fighting the global pandemic by developing an automated image analysis module for identifying covid-19 affected chest X-ray scans by employing an optimized Convolution Neural Network (CNN) model. The aforementioned objective is achieved in the following manner by developing three classification models, (i) ensemble of ResNet 50-Error Correcting Output Code (ECOC) model, (ii) CNN optimized using Grey Wolf Optimizer (GWO) and, (iii) CNN optimized using Whale Optimization + BAT algorithm. The novelty of the proposed method lies in the automatic tuning of hyper parameters considering a hierarchy of MultiLayer Perceptron (MLP), feature extraction, and optimization ensemble. A 100% classification accuracy was obtained in classifying covid-19 images. Classification accuracy of 98.8% and 96% were obtained for dataset 1 and dataset 2 respectively for classification into covid-19, normal, and viral pneumonia cases. The proposed method can be adopted in a clinical setting for assisting radiologists and it can also be employed in remote areas to facilitate the faster screening of affected patients.

An optimized convolutional neural network architecture for lung cancer detection.

Lung cancer, the treacherous malignancy affecting the respiratory system of a human body, has a devastating impact on the health and well-being of an individual. Due to the lack of automated and noninvasive diagnostic tools, healthcare professionals look forward toward biopsy as a gold standard for diagnosis. However, biopsy could be traumatizing and expensive process. Additionally, the limited availability of dataset and inaccuracy in diagnosis is a major drawback experienced by researchers. The objective of the proposed research is to develop an automated diagnostic tool for screening of lung cancer using optimized hyperparameters such that convolutional neural network (CNN) model generalizes well for universally obtained computerized tomography (CT) slices of lung pathologies. The aforementioned objective is achieved in the following ways: (i) Initially, a preprocessing methodology specific to lung CT scans is formulated to avoid the loss of information due to random image smoothing, and (ii) a sine cosine algorithm optimization algorithm (SCA) is integrated in the CNN model, to optimally select the tuning parameters of CNN. The error rate is used as an objective function, and the SCA algorithm tries to minimize. The proposed method successfully achieved an average classification accuracy of 99% in classification of lung scans in normal, benign, and malignant classes. Further, the generalization ability of the proposed model is tested on unseen dataset, thereby achieving promising results. The quantitative results prove the efficacy of the system to be used by radiologists in a clinical scenario.

A Compact MIMO Antenna Based on Modal Analysis for 5G Wireless Applications.

This article presents a planar, non-angular, series-fed, dual-element dipole array MIMO antenna operating at 28 GHz with the metasurface-based isolation improvement technique. The initial design is a single-element antenna with a dual dipole array which is series-fed. These dipole elements are non-uniform in shape and distance. This dipole antenna results in end-fire radiation. The dipole antenna excites the J1 mode for its operation. Further, with the view to improve channel capacity, the dipole array expands the antenna to a three-element MIMO antenna. In the MIMO antenna structure, the sum of the J1, J2, and J3 modes is excited, causing resonance at 28 GHz. This article also proposes a metasurface structure with wide stopband characteristics at 28 GHz for isolation improvement. The metasurface is composed of rectangle-shaped structures. The defected ground and metasurface structure combination suppresses the surface wave coupling among the MIMO elements. The proposed antenna results in a bandwidth ranging from 26.7 to 29.6 GHz with isolation improvement greater than 21 dB and a gain of 6.3 dBi. The antenna is validated with the diversity parameters of envelope correlation coefficient, diversity gain, and channel capacity loss.

Planar MIMO antenna for mmWave applications: Evolution, present status & future scope.

The increased traffic in e-commerce, cloud-based processing, social media, and online video streaming demands higher data rates. The current 4G has reached the bottleneck, due to which it may not be able to fulfill the high data demand, so the focus is drifting toward millimeter wave (mmWave). The mmWave spectrum ranging from 30 to 300 GHz offers wide bandwidth with low latency, which finds its application in various communication fields, including 5G cellular. Despite its atmospheric attenuation and non-line-of-sight (NLOS) propagation, most countries are currently adopting mmWave 5G at the 28/38 GHz band due to less atmospheric attenuation, low path loss exponent, and low signal spread at these bands. The single-element patch antenna is a compact solution for mmWave applications, but its performance is inferior in terms of bandwidth, gain, and radiation efficiency. The array antennas have overcome these demerits, as it has shown a significant increase in bandwidth, gain, and radiation efficiency. Still, it has a limitation on data rate support. As a result, Multiple-Input-Multiple-Output (MIMO) technology can increase the data rate to 1000 times through spatial diversity and multiplexing techniques. So, to refine the performance further, there is a need to comprehend the MIMO antenna structures designed so far at mmWave. This paper presents the planar MIMO antenna structures developed so far, categorized here as slot, coplanar waveguide, defected ground structures, tapered/Vivaldi, meta-surface/metamaterial, dielectric resonator, and flexible antennas. The performance of these designs is compared based on bandwidth, gain, isolation, efficiency, and radiation pattern. This article also discusses the effects of slots, partial ground, and decoupling structures on impedance matching, bandwidth, and isolation levels. Also, a thorough discussion of the design issues and future work to be undertaken is discussed in this here.

All-cause and major-cause mortality associated with sleep latency in the Korean Genome and Epidemiology Study (KoGES): a population-based prospective cohort study.

BACKGROUND: The all-cause and cause-specific mortality risk associated with sleep latencies in the general adult population is unknown. We aimed to investigate the association of habitual prolonged sleep latency with long-term all-cause and cause-specific mortality in adults. METHODS: The Korean Genome and Epidemiology Study (KoGES) is a population-based prospective cohort study comprising community-dwelling men and women aged 40-69 years from Ansan, South Korea. The cohort was studied bi-annually from April 17, 2003, to Dec 15, 2020, and the current analysis included all individuals who completed the Pittsburgh Sleep Quality Index (PSQI) questionnaire between April 17, 2003, and Feb 23, 2005. The final study population comprised 3757 participants. Data were analysed from Aug 1, 2021, to May 31, 2022. The main exposure was sleep latency groups based on the PSQI questionnaire: fell asleep in 15 min or less, fell asleep in 16-30 min, occasional prolonged sleep latency (fell asleep in >30 min once or twice a week in the past month) and habitual prolonged sleep latency (fell asleep in >60 min more than once a week or fell asleep in >30 min ≥3 times a week, or both) in the past month at baseline. Outcomes were all-cause and cause-specific (cancer, cardiovascular disease, and other causes) mortality reported during the 18-year study period. Cox proportional hazards regression models were used to examine the prospective relationship between sleep latency and all-cause mortality, and competing risk analyses were done to investigate the association of sleep latency with cause-specific mortality. FINDINGS: During a median follow-up of 16·7 years (IQR 16·3-17·4), 226 deaths were reported. After adjusting for demographic characteristics, physical characteristics, lifestyle factors, chronic conditions, and sleep variables, self-reported habitual prolonged sleep latency was associated with an increased risk of all-cause mortality (hazard ratio [HR] 2·22, 95% CI 1·38-3·57) compared to the reference group (those who fell asleep in 16-30 min). In the fully adjusted model, habitual prolonged sleep latency was associated with a more than doubled risk of dying from cancer compared to the reference group (HR 2·74, 95% CI 1·29-5·82). No significant association was observed between habitual prolonged sleep latency and deaths from cardiovascular disease and other causes. INTERPRETATION: In this population-based prospective cohort study, habitual prolonged sleep latency was independently associated with an increased risk of all-cause and cancer-specific mortality in adults (independently of demographic characteristics, lifestyle factors, chronic morbidities, and other sleep variables). Although further studies are warranted to investigate the causality of the relationship, strategies or interventions to prevent habitual prolonged sleep latencies might enhance longevity in the general adult population. FUNDING: Korea Centers for Disease Control and Prevention.

Characteristic Mode Analysis-Based Compact Dual Band-Notched UWB MIMO Antenna Loaded with Neutralization Line.

The advancement of electronic gadgets makes it possible for a device to be multipurpose, which calls for attributes such as compactness and larger bandwidth, with improved data transfer rate. This paper introduces the compact, closely placed two-port dual band-notched UWB antenna using a neutralization line as a decoupling structure. The projected antenna design comprised a circle and rectangle embedded monopole radiator with the defected ground structure to attain the UWB spectrum. Further dual notches are attained by carving the U-shape and inverted U-shape slots on the feedline and radiator. The dual band-notched UWB antennas are placed with the separation of 3.8 mm (0.04 λ; λ is computed using 3.4 GHz frequency). The coupling effect between the close proximity elements is decoupled using the neutralization line. The presented antenna has overall dimensions of 21.5 × 28 × 1.6 mm3 (0.24 × 0.31 × 0.01 λ3) and exhibits S11 below −10 dB from 3.4−11.9 GHz, with isolation better than 16 dB throughout the impedance bandwidth. The antenna also provides frequency band rejection of 4.5−5.3 GHz and 7.2−9 GHz covering the WLAN and entire X-band satellite communication. The projected antenna is explored through characteristic mode analysis, time-domain characteristics, and MIMO diversity features to analyze the effectiveness and usefulness of the antenna. The group delay is less than 1 ns except for the frequency rejection band and fidelity factor greater than 0.96. The projected antenna exhibits MIMO diversity metrics ECC < 0.3, DG > 9.6 dB, MEG < −3 dB, TARC < −10 dB, CCL < 0.3 bps/Hz, and ME < −2 dB across the operational frequency, except for the notched bands. The designed two-port antenna is validated by printing on an FR4 substrate. The simulated and measured findings are in line with and appropriate for MIMO wireless applications.

An Ultra-Compact 28 GHz Arc-Shaped Millimeter-Wave Antenna for 5G Application.

The 5th generation (5G) network was planned to provide a fast, stable, and future-proof mobile communication network to existing society. This research presents a highly compact arc shape structure antenna resonating at 28 GHz for prospective millimeter-wave purposes in the 5G frequency spectrum. The circular monopole antenna is designed with a radius of 1.3 mm. An elliptical slot on the radiating plane aids in achieving an enhanced bandwidth resonating at the frequency of 28 GHz. Including an elliptical slot creates new resonance and helps improve the bandwidth. The antenna has an ultra-compact dimension of 5 × 3 × 1.6 mm3, which corresponds to an electrical length of 0.46λ × 0.28λ × 0.14λ, where λ is free space wavelength at the resonant frequency. The projected antenna has an impedance bandwidth of 15.73 % (25.83-30.24 GHz). The antenna has a good radiation efficiency of 89%, and the average gain is almost 4 dB over the entire impedance bandwidth. The simulated and experimental S11 findings are in good agreement.

Cluster-ID-Based Throughput Improvement in Cognitive Radio Networks for 5G and Beyond-5G IoT Applications.

Cognitive radio (CR), which is a common form of wireless communication, consists of a transceiver that is intelligently capable of detecting which communication channels are available to use and which are not. After this detection process, the transceiver avoids the occupied channels while simultaneously moving into the empty ones. Hence, spectrum shortage and underutilization are key problems that the CR can be proposed to address. In order to obtain a good idea of the spectrum usage in the area where the CRs are located, cooperative spectrum sensing (CSS) can be used. Hence, the primary objective of this research work is to increase the realizable throughput via the cluster-based cooperative spectrum sensing (CBCSS) algorithm. The proposed scheme is anticipated to acquire advanced achievable throughput for 5G and beyond-5G Internet of Things (IoT) applications. Performance parameters, such as achievable throughput, the average number of clusters and energy, have been analyzed for the proposed CBCSS and compared with optimal algorithms.

A Compact Dual-Band Notched UWB Antenna for Wireless Applications.

This article presents the design and analysis of a V-shaped ultrawideband (UWB) antenna and dual-band UWB notch antenna. A rectangular slot is cut into a semicircular partial ground plane of the antenna to achieve ultrawide bandwidth. A U-shape slot is etched on a V-shaped patch that radiates, and an inverted U-shape parasitic resonator is placed beside the feedline to generate dual-band notch characteristics. The overall dimension of the proposed antenna is 28×23 mm2. The proposed UWB antenna has a gain of 9.8 dB, S11 < -10 dB, impedance bandwidth in the range of 3.4 to 12.3 GHz, response with a linear phase, group delay <1 ns, and stable radiation pattern. The UWB notch antenna shows strong rejection in the WLAN band from 5.15 to 5.8 GHz with a notch at 5.6 GHz and X band from 9.1 to 10.5 GHz with a sharp notch at 9.6 GHz, having a S11 < -10 dB impedance bandwidth ranging from 3.2 to 11.7 GHz. This antenna also exhibits a stable radiation pattern, group delay <1 ns, and linear phase response throughout the bandwidth except at the rejection frequencies.

Ultrawideband Antennas: Growth and Evolution.

Narrowband antennas fail to radiate short pulses of nano- or picosecond length over the broader band of frequencies. Therefore, Ultrawideband (UWB) technology has gained momentum over the past couple of years as it utilizes a wide range of frequencies, typically between 3.1-10.6 GHz. UWB antennas have been utilized for various applications such as ground-penetrating radars, disaster management through detection of unexploded mines, medical diagnostics, and commercial applications ranging from USB dongles to detection of cracks in highways and bridges. In the first section of the manuscript, UWB technology is detailed with its importance for future wireless communications systems. In the next section various types of UWB antennas and their design methodology are reviewed, and their important characteristics are highlighted. In section four the concept of a UWB notch antenna is presented. Here various methods to obtain the notch, such as slots, parasitic resonators, metamaterials, and filters are discussed in detail. In addition, various types of important notch antenna design with their technical specifications, advantages, and disadvantages are presented. Finally, the need of reconfigurable UWB notch antennas is discussed in the next section. Here various insight to the design of frequency reconfigurable notch antennas is discussed and presented. Overall, this article aims to showcase the beginnings of UWB technology, the reason for the emergence of notching in specific frequency bands, and ultimately the need for reconfiguring UWB antennas along with their usage.

A Multiband Antenna Stacked with Novel Metamaterial SCSRR and CSSRR for WiMAX/WLAN Applications.

This paper presents an innovative method for the design of a triple band meta-mode antenna. This unique design of antenna finds application in a particular frequency band of WLAN and WiMAX. This antenna comprises of a square complimentary split ring resonator (SCSRR), a coaxial feed, and two symmetrical comb shaped split ring resonators (CSSRR). The metamaterial unit cell SCSRR independently gains control in the band range 3.15-3.25 GHz (WiMAX), whereas two symmetrical CSSRR unit cell controls the band in the ranges 3.91-4.01 GHz and 5.79-5.94 GHz (WLAN). This design methodology and the study of the suggested unit cells structure are reviewed in classical waveguide medium theory. The antenna has a miniaturized size of only 0.213λ0 × 0.192λ0 × 0.0271λ0 (20 × 18 × 2.54 mm3, where λ0 is the free space wavelength at 3.2 GHz). The detailed dimension analysis of the proposed antenna and its radiation efficiency are also presented in this paper. All the necessary simulations are carried out in High Frequency Structure Simulator (HFSS) 13.0 tool.

A 20-44 GHz Wideband LNA Design Using the SiGe Technology for 5G Millimeter-Wave Applications.

This paper presents the design and implementation of a low-noise amplifier (LNA) for millimeter-wave (mm-Wave) 5G wireless applications. The LNA was based on a common-emitter configuration with cascode amplifier topology using an IHP's 0.13 µm Silicon Germanium (SiGe) heterojunction bipolar transistor (HBT) whose f_T/f_MAX/gate-delay is 360/450 GHz/2.0 ps, utilizing transmission lines for simultaneous noise and input matching. A noise figure of 3.02-3.4 dB was obtained for the entire wide bandwidth from 20 to 44 GHz. The designed LNA exhibited a gain (S_21) greater than 20 dB across the 20-44 GHz frequency range and dissipated 9.6 mW power from a 1.2 V supply. The input reflection coefficient (S_11) and output reflection coefficient (S_22) were below -10 dB, and reverse isolation (S_12) was below -55 dB for the 20-44 GHz frequency band. The input 1 dB (P1dB) compression point of -18 dBm at 34.5 GHz was obtained. The proposed LNA occupies only a 0.715 mm2 area, with input and output RF (Radio Frequency) bond pads. To the authors' knowledge, this work evidences the lowest noise figure, lowest power consumption with reasonable highest gain, and highest bandwidth attained so far at this frequency band in any silicon-based technology.