Search

In this paper, a broadband, polarization-independent metamaterial absorber for millimeter waves is proposed. Operating across the frequency range of 22.7 GHz to 37.2 GHz, our broadband, polarization-independent absorber demonstrates exceptional efficacy by capturing over 90% of incident wave power. Distinguished by an array of conductive square patches on a dielectric substrate, the proposed structure boasts a remarkably low thickness, measuring less than a quarter of the free space wavelength of the central point within its operational spectrum (excluding the ground layer thickness). Leveraging a combination of circuit modeling and transmission line theory, this paper presents the design of this absorber and also elucidates its underlying operating principles. The combination of broadband operation, low thickness, and systematic design is rarely seen in previous works. To validate the proposed approach, a physical prototype is realized using 3D printing technology, employing conductive polylactic acid (C-PLA) patches on a light polyvinyl chloride (L-PVC) substrate. The proposed absorber has various potential applications in communication, electromagnetic shielding, and satellite technologies. Finally, a comparison with recent works is performed to demonstrate the feasibility of the proposed structure for millimeter-wave applications. [ABSTRACT FROM AUTHOR]

In this paper, we investigate IRS-aided user cooperation (UC) scheme in millimeter wave (mmWave) wireless-powered sensor networks (WPSN), where two single-antenna users are wireless powered in the wireless energy transfer (WET) phase first and then cooperatively transmit information to a hybrid access point (AP) in the wireless information transmission (WIT) phase, following which the IRS is deployed to enhance the system performance of the WET and WIT. We maximized the weighted sum-rate problem by jointly optimizing the transmit time slots, power allocations, and the phase shifts of the IRS. Due to the non-convexity of the original problem, a semidefinite programming relaxation-based approach is proposed to convert the formulated problem to a convex optimization framework, which can obtain the optimal global solution. Simulation results demonstrate that the weighted sum throughput of the proposed UC scheme outperforms the non-UC scheme whether equipped with IRS or not. [ABSTRACT FROM AUTHOR]

We present a fully telemetric sensor concept for angle and position measurement. It is based on single-layer millimeter-wave metamaterials that exhibit an anisotropic resonant behavior in interaction with incident electromagnetic waves. The angle of rotation is determined from the reflected millimeter waves of the metamaterial target using a millimeter wave chip transceiver. We use a metamaterial geometry exhibiting anisotropic Fano-type resonant behavior. The Fano-type resonance shows a distinct minimum in the reflection spectrum, even with a single layer of metamaterial. The metamaterial target is manufactured on a printed circuit board (PCB) laminate with low-cost standard manufacturing methods. We present an analytical model estimating the resonance frequency of the metamaterial used. The model allows us to assess whether with the Fano-type metamaterial unit cell structure resonance frequencies in the millimeter wave regime are achievable and compliant with standard PCB manufacturing design rules. We performed proof-of-principle experiments with the metamaterial targets and a vector network analyzer, assisted by a detailed analysis of the sensor effect by means of finite-element method calculations. Finally, we implemented a demonstrator setup containing a state-of-the-art frequency-modulated continuous-wave (FMCW) radar chip and a metamaterial target manufactured with standard PCB manufacturing processes. [ABSTRACT FROM AUTHOR]

Traffic participant classification is crucial in autonomous driving perception. Millimeter wave radio detection and ranging radar is a cost-effective and powerful method to perform the task in adverse traffic scenarios, especially in bad inclement weather (e.g. fog, snow and rain) and poor lighting conditions. This paper presents an intelligent target classification algorithm for 77G radar based on correction data set. First, in order to handle the problem that the original data set may easily be interfered by obstacles, the angle information is filtered by analyzing the spatial information of radar signals, which means the interference clutter of obstacles can be effectively removed. Second, the primary data set is corrected using the significant difference between the micro-Doppler of the human body and car. Finally, the characteristic information of the radar signal is extracted, including distance, speed, orientation, micro-Doppler and reflection intensity, and the obtained data sets containing three types of targets (vehicles, human bodies and obstacles) are generated. The generated dynamic and static data sets are collected by sufficient experiments to construct deep learning classification models. The results show that the classification accuracy is improved by the measure of data set correction. [ABSTRACT FROM AUTHOR]

Small-scale motion detection using non-invasive remote sensing techniques has recently garnered significant interest in the field of speech recognition. Our dataset paper aims to facilitate the enhancement and restoration of speech information from diverse data sources for speakers. In this paper, we introduce a novel multimodal dataset based on Radio Frequency, visual, text, audio, laser and lip landmark information, also called RVTALL. Specifically, the dataset consists of 7.5 GHz Channel Impulse Response (CIR) data from ultra-wideband (UWB) radars, 77 GHz frequency modulated continuous wave (FMCW) data from millimeter wave (mmWave) radar, visual and audio information, lip landmarks and laser data, offering a unique multimodal approach to speech recognition research. Meanwhile, a depth camera is adopted to record the landmarks of the subject's lip and voice. Approximately 400 minutes of annotated speech profiles are provided, which are collected from 20 participants speaking 5 vowels, 15 words, and 16 sentences. The dataset has been validated and has potential for the investigation of lip reading and multimodal speech recognition. [ABSTRACT FROM AUTHOR]

4D millimeter wave (mmWave) imaging radar is a new type of vehicle sensor technology that is critical to autonomous driving systems due to its lower cost and robustness in complex weather. However, the sparseness and noise of point clouds are still the main problems restricting the practical application of 4D imaging radar. In this paper, we introduce SMIFormer, a multi-view feature fusion network framework based on 4D radar single-modal input. SMIFormer decouples the 3D point cloud scene into 3 independent but interrelated perspectives, including bird's-eye view (BEV), front view (FV), and side view (SV), thereby better modeling the entire 3D scene and overcoming the shortcomings of insufficient feature representation capabilities under single-view built from extremely sparse point clouds. For multi-view features, we proposed multi-view feature interaction (MVI) to exploit the inner relationship between different views by integrating features from intra-view interaction and cross-view interaction. We evaluated the proposed SMIFormer on the View-of-Delft (VoD) dataset. The mAP of our method reached 48.77 and 71.13 in the fully annotated area and the driving corridor area, respectively. This shows that 4D radar has great development potential in the field of 3D object detection. [ABSTRACT FROM AUTHOR]

The quality of the signal received at any location in communication channel depends on the degree of losses and attenuation experience along its path. The existing models are not suitable for 5G network propagation due to heavy channel interference and signal loss applicable at millimeter wave (mmWave) spectrum. The issues of Path Loss (PL) and signal interference in 5G New Radio (NR) network needs special attention. It is expected that 5G NR and 4G LTE-A networks will coexist for a very long time using the existing infrastructure. Hence, it is important to develop a good model to mitigate signal attenuation and co-channel interference that comes with the deployment of the 5G NR network. The existing models and measured data were compared to find out the closest model to the measured value. This paper proposed a modify Okumura-Hata (Ok-Hata) model for signal propagation in new 5G network. Also, an improved Autoregressive Particle Swarm Intelligent (APSI) algorithm was presented to enhance the proposed model for better performance. The modified Ok-Hata model outperformed all the existing models. The modified model has the potential to mitigate the effect of interference in 5G NR at 3.5 GHz frequency. The proposed new model has the capacity to solve some network issues such as; path loss, co-channel interference in 5G network. The result shows that there was no signal interference between the existing, and modified models. The result also shows that enhanced APSI is suitable for 5G NR network planning in Abuja, Nigeria. [ABSTRACT FROM AUTHOR]

This study offers a 5G substrate integrated waveguide (SIW) antenna with vertical S zigzag shape slot. The suggested antenna's radiating patch depends on the shape of the slot. Two types of slots have been used, straight and zigzag S shape slot with vertical and horizontal direction, slots are etched on the patch to increase the antenna's overall bandwidth and gain. The suggested straight and zigzag SIW S slot antennas both resonate at 28 GHz, and the overall structure size is 7.10×14.93 mm. The presented design could achieve high gain, efficiency, and minimal losses, which are all important concerns. The presented antenna may produce a gain of 9.48 dB, a 95% efficiency, and a wider bandwidth of no less than 3.25 GHz at 28 GHz. [ABSTRACT FROM AUTHOR]

Sixth-generation (6G) applications require ultra-speed and large-capacity wireless communication services. Millimeter wave technology can be used to satisfy these requirements, especially at 28 GHz. This paper study used the Ansys® high-frequency structure simulator (HFSS) to design and simulate rectangular and slotted rectangular microstrip patch antennas (MSPAs) at 28 GHz. The proposed designs contained a Rogers RT/Duroid® 5,880 substrate with a dielectric constant (er) of 2.2 and a loss tangent of 0.0009. The performance of both the proposed antennas was compared to determine which was more efficient. This present study also used an adaptive network-based fuzzy inference system (ANFIS) to determine the optimal frequency and gain. The main objective of the manuscript is to use artificial intelligence (AI) to obtain the best design results for MSPA. The results indicated, with the use of AI, the gain of the rectangular and slotted antennas, was 6.3943 and 6.3094 dB at an efficiency of 98.338% and 98.651%, respectively. [ABSTRACT FROM AUTHOR]

This study investigates the microwave dielectric properties of pure CoMoO4 ceramics prepared using the conventional solid-state reaction method. Sintering temperatures ranging from 600° to 720°C were employed, and the effects of partial substitution of Mg2 + on these properties, specifically the sintering temperature and microwave dielectric characteristics, were examined. X-ray diffraction patterns revealed the formation of a single solid solution of Co1-xMgxMoO4 (x = 0–0.09) with a monoclinic structure and space group C2/m. Pure CoMoO4 samples sintered at 690 oC displayed dielectric properties of εr = 8.27, Q×f = 64,000 GHz, and τf = –96 ppm/°C. The partial substitution of Co2 + with Mg2 + effectively enhanced the densification of ceramics and reduced their dielectric loss and sintering temperature, which was systematically investigated with respect to dielectric polarization, lattice energy, packing fraction, and bond valence. The Co0.95Mg0.05MoO4 ceramic sintered at 630 oC exhibited excellent dielectric properties with εr = 8.42, Q×f = 71,000 GHz, and τf = –62.27 ppm/°C, and demonstrated good chemical compatibility. Furthermore, this ceramic was employed as a substrate for a 4 × 4 dual-polarized array antenna, indicating significant potential for use in ULTCC applications, particularly in the high-frequency millimeter wave region. [ABSTRACT FROM AUTHOR]

The evolution to 5G millimeter wave (mmWave) is opening doors to many novel applications and services by leveraging the higher carrier frequency of 24 GHz and beyond. 5G mmWave promises to deliver extreme bandwidth, ultra-low latency, faster data speeds and responsiveness – thereby facilitating broadband connectivity to densely populated areas. Nevertheless, millimeter waves suffer from significant path loss, imposing severe range constraints. Beamforming is a promising technique to alleviate this impediment. Integrated photonics is sophisticated technology to realize cost-effective, compact, and power-efficient beamformers. In this paper, we propose photonically controlled continuously tunable single side coupled racetrack resonator based 1 × 8 broadband beamformer on CMOS-compatible silicon-on-insulator platform. A beam steering angle of 31.001˚ is achieved for 28 GHz mmWave wave signal. The proposed beamformer can provide maximum continuously tunable true time delay of 125 ps for delay bandwidth of 32.46 GHz. Therefore, the beam scanning range of 0–90° can be attained by properly tuning the coupling coefficient and resonance frequency of the racetrack resonator based delay element. [ABSTRACT FROM AUTHOR]

Millimeter wave radar has the advantage of all-day and all-weather capability for detection, speed measurement. It plays an important role in urban traffic flow monitoring and traffic safety monitoring. The conventional 2-dimensional Fast Fourier Transform (2DFFT) algorithm is performed target detection in the range-Doppler domain. However, the target motion will induce the range walk phenomenon, which leads to a decrease in the target energy and the performance of the target detection and speed measurement. To solve the above problems, this paper proposes a moving vehicle detection algorithm based on Keystone-2DFFT for a traffic scene. Firstly, this paper constructs and analyzes the Frequency Modulated ContinuousWave (FMCW) moving target signal model under traffic monitoring scenario's radar observation geometry. The traditional 2DFFT moving target detection algorithm is briefly introduced. Then, based on mentioned signal model, an improved moving vehicle detection algorithm based on Keystone-2DFFT transform is proposed. The method first input the echo, then the range walk is removed by keystone transformation. the keystone transformation is achieved via Sinc interpolation. Next is transform data into range-Doppler domain to perform detection and speed estimation. The algorithm is verified by simulation data and real data. [ABSTRACT FROM AUTHOR]

Millimeter wave (mmWave) and terahertz (THz) massive MIMO architectures are pivotal in the advancement of mobile communications. These systems conventionally utilize codebooks to facilitate initial connection and to manage information transmission tasks. Traditional codebooks, however, are typically composed of numerous single-lobe beams, thus incurring substantial beam training overhead. While neural network-based approaches have been proposed to mitigate the beam training load, they sometimes fail to adequately consider the minority users dispersed across various regions. The fairness of the codebook coverage relies on addressing this problem. Therefore, we propose an imbalanced learning (IL) methodology for beam codebook construction, explicitly designed for scenarios characterized by an imbalanced user distribution. Our method begins with a pre-clustering phase, where user channels are divided into subsets based on their power response to combining vectors across distinct subareas. Then, each subset is refined by a dedicated sub-model, which contributes to the global model within each IL iteration. To facilitate the information exchange among sub-models during global updates, we introduce the focal loss mechanism. Our simulation results substantiate the efficacy of our IL framework in enhancing the performance of mmWave and THz massive MIMO systems under the conditions of imperfect channel state information and imbalanced user distribution. [ABSTRACT FROM AUTHOR]

The role and applications of millimeter wave (mmWave) Reconfigurable Intelligent Surfaces (RIS) have been rapidly increasing by extending the signal coverage with energy and spectrum efficiency. However, the current RIS designs pose challenges like size and angular insensitivity with efficient beamforming functionalities. In this article, we propose a compact and angularly stable RIS unitcell with incident and polarization angle insensitivity in reflection mode. The footprint of the FR4 substrate is 10×10×1.6 mm3 in size. The unitcell structure consists of circular patch inner cuts as a top layer with a full ground. An AlGaAs pin diode is inserted in the middle of the top layer to get the beamforming. The switchable states provide peak resonance at 32.5 GHz (Bandwidth-444 MHz) and 33.6 GHz (Bandwidth-498 MHz) frequencies. Significant gain values of 11.5 and 13.7 dBi are achieved at the operating frequencies. The designed unitcell provides angular stability up to 90° oblique incidences and polarization angles. The AlGaAs pin diode is controlled by applying suitable bias levels using Arduino Uno. The numerical simulation results and experimental validation are performed with incident and polarization angles, which are suitable for adapting to the challenges in mmWave applications. [ABSTRACT FROM AUTHOR]

Multiple input multiple output (MIMO) system with Millimeter Wave spectrum is currently used in most wireless applications and all cellular system to provides high data rates. with using large antenna array which is possible by decrease the wavelength to achieve high beamforming gain and improve the spectral efficiency. in this paper, used low complexity with hybrid precoding at the transmitting side and combining at the receiver side with limited feedback system, by using the concept of orthogonal matching pursuit (OMP) in single and multi-user cases, and compared the results with analog only beasmstring. The results of simulation showed that when used Minimum Mean Square Error (MMSE) precoders performed better than other hybrid precoding approaches, in addition the MMSE hybrid precoding /combining technique offers higher spectral efficiency compared with analog only beamstring. [ABSTRACT FROM AUTHOR]

The bandwidth limitation is an arduous challenge to deploy the large-scale Internet of Things (IoTs) beyond fifth-generation (B5G) communication networks. Although the millimeter wave (mmWave) technology can provide greater bandwidth at the cost of complex processors in harsh environments, it can be a solution to establish large-scale IoTs. Still, its cost and power requirements become obstacles to widespread adoption. In this context, Reconfigurable Intelligent Surfaces (RISs) can be a crucial technology to meet this challenge. In this paper, we study the B5G RIS-assisted MIMO simultaneous wireless-information and power-transfer (SWIPT) mmWave large-scale IoTs, where active BS transmitted beamformer and passive RIS reflection vector are jointly optimized to maximize the minimum signal-to-interference-plus-noise-ratio (SINR) of all the information decoders (ID) and the minimum harvested power of all the energy receivers (ER) is maintained. The simulation result demonstrates the effectiveness of the proposed system. [ABSTRACT FROM AUTHOR]

Millimeter wave bands (30–300 GHz) are attracting a lot of research attention because they can possibly lead to data rates of nearly 10 Gbits/s, a lot of accessible bandwidth, narrow beam, good transmission quality, and excellent detection abilities compared to microwave frequencies which are restricted to 1 Gbits/s. This paper presents a comprehensive survey of the recent research developments on antenna designing specifically at 30, 60 and 120 GHz mmWave wireless communication bands along with their characteristics, applications, limitations, material selection, challenges, and proposed solutions. Several mmWave antennas published in the literature are covered in this study, including their type, characteristics, design challenges, and future research prospects. A comparison of various mmWave antennas published recently are analysed in terms of gain, bandwidth, efficiency, number of elements and type of antenna technology. At last, the design techniques such as Antenna-in-Package (AiP), Antenna-on-Chip (AoP) and various fabrication technologies are described including their merits as well as demerits. [ABSTRACT FROM AUTHOR]

This paper proposes a high isolation of single pole double throw (SPDT) PIN diode switch using switchable dumbbell-shaped defected ground structure (DGS). The proposed SPDT switch was designed for radio frequency (RF) front-end transceiver of antenna array multiple input multiple output (MIMO) in millimeter wave 28 GHz band. The switchable dumbbell-shaped DGS can be switched between allpass and bandstop responses where the bandstop response of the DGS can be utilized as a high isolation in the SPDT PIN diode switch circuit. A simple mathematical analysis is explained in this paper for the bandstop and allpass responses of the switchable dumbbell-shaped DGS. The propose SPDT switch was designed based on Roger RT/Duroid 5880 with 0.254 mm thickness and relative dielectric constant of 2.2. The simulated result showed that the proposed SPDT PIN diode switch produced an isolation of 36.36 dB at 27.3 GHz (center of 28 GHz band), which was 63% higher than the conventional SPDT design. [ABSTRACT FROM AUTHOR]

We have studied the interference caused by amplitude and phase distortions induced by rain in ultra-wideband communication systems designed for using amplitude modulation in GeoSurf future satellite constellations. The results concern radio links simulated with the synthetic storm technique at Spino d'Adda (Italy), Madrid (Spain) and Tampa (Florida), which are sites located in different climatic regions. The conclusions are (a) the three sites, although in different climatic zones, are practically indistinguishable; (b) the channel signal-to-noise ratio can be increased or decreased by interference with equal probability. Channel theoretical capacity loss, even in the worst case, is very limited and rain, therefore, does not cause significant linear distortions in ultra-wideband channels at millimeter waves; therefore, these channels could be used at millimeter waves. [ABSTRACT FROM AUTHOR]

In combination with the expected traffic avalanche foreseen for the next decade, solutions supporting energy-efficient, scalable and flexible network operations are essential. Considering the myriad of user case requirements, THz and mmW bands will play key roles in 6G networks. While mmW is known for short-rate LOS connections, THz transmission is subjected to even severe propagation losses, resulting in very short-range connections. In this context, we evaluate a dynamic multi-band user association algorithm to optimize connectivity in coexisting RF/mmW/THz networks. The algorithm periodically calculates association scores for each user–base station pair based on real-time channel conditions across bands, accounting for factors like signal strength, link blockage risk and noise. It then reassociates users in batches to balance loads while considering user priorities and network conditions. We simulate the algorithm's performance within a realistic propagation model, where high path loss, molecular absorption, blockage, and narrow beam widths contribute to lower coverage at higher frequencies. Results demonstrate the algorithm's ability to efficiently utilize network resources across diverse operating environments. In addition, our results show that the choice of frequency band depends on the specific requirements of the application, the environment, and the trade-offs between coverage distance, capacity, and interference conditions. [ABSTRACT FROM AUTHOR]

IntroductionGlioblastoma (grade IV) is the most aggressive primary brain tumor in adults, representing one of the biggest therapeutic challenges due to its highly aggressive nature. In this study, we investigated the impact of millimeter waves on tridimensional glioblastoma organoids derived directly from patient tumors. Our goal was to explore novel therapeutic possibilities in the fight against this challenging disease.MethodsThe exposure setup was meticulously developed in-house, and we employed a comprehensive dosimetry approach, combining numerical and experimental methods. Biological endpoints included a global transcriptional profiling analysis to highlight possible deregulated pathways, analysis of cell morphological changes, and cell phenotypic characterization which are all important players in the control of glioblastoma progression.Results and discussionOur results revealed a significant effect of continuous millimeter waves at 30.5 GHz on cell proliferation and apoptosis, although without affecting the differentiation status of glioblastoma cells composing the organoids. Excitingly, when applying a power level of 0.1 W (Root Mean Square), we discovered a remarkable (statistically significant) therapeutic effect when combined with the chemotherapeutic agent Temozolomide, leading to increased glioblastoma cell death. These findings present a promising interventional window for treating glioblastoma cells, harnessing the potential therapeutic benefits of 30.5 GHz CW exposure. Temperature increase during treatments was carefully monitored and simulated with a good agreement, demonstrating a negligible involvement of the temperature elevation for the observed effects. By exploring this innovative approach, we pave the way for improved future treatments of glioblastoma that has remained exceptionally challenging until now.

To meet the demand of noise reduction in millimeter‐wave human body security imaging, this paper proposes a new method for 3D segmentation denoising in millimeter‐wave images. The test results indicate that with the incorporation of 3D segmentation denoising technology, the noise in the background area of millimeter wave images has decreased by approximately 20–40 dB, significantly improving image quality. The detection rate has increased from 90% to 95%, while the false positive rate has decreased from 13% to 5%. This has important practical significance for real‐world applications. [ABSTRACT FROM AUTHOR]

Non-contact gesture recognition is a novel form of human–computer interaction. It has broad prospects in many applications, such as Augmented Reality/Virtual Reality, smart homes and intelligent medical systems. Therefore, it has become a research hotspot in recent years. This paper investigates a lightweight micro-motion gesture recognition method based on Multiple Input and Multiple Output millimeter wave radar. We employ TI's MMWCAS radar, comprising four cascaded AWR1243 radar boards, to collect gesture data. During the data pre-processing stage, we extract the Range-time Map, Doppler-time Map, Azimuth-time Map and Elevation-time Map of the dynamic gestures to characterize the dynamic motion features. These maps are then simplified into a one-dimensional vector to reduce data volume. We propose an 8HBi-GRU model, which combines the Bidirectional Gate Recurrent Unit (Bi-GRU) with a multi-head self-attention mechanism, to identify twelve types of micro-motion gestures using feature vectors. The model achieves an accuracy of 98.24 % , with precision and recall rates exceeding 0.97 and 0.98, respectively, for ten of the gesture types. Experimental results demonstrate that the proposed 8HBi-GRU model achieves lightweight gesture recognition rapidly and requires minimal storage space compared to image-based deep learning methods. [ABSTRACT FROM AUTHOR]

Key technologies in 5G and future 6G, such as millimeter wave massive multiple-input multiple-output (MIMO), relies accurate channel state information (CSI). However, when the number of base station (BS) antenna increases or the number of users is large, it is rather resource-consuming to obtain the CSI. Channel knowledge map (CKM) is an emerging environment-aware wireless communication technology, which stores the physical coordinates of BS and reference locations together with the corresponding channel path information. This makes it possible to obtain CSI with light or even without pilots, which can significantly reduce the overhead of channel estimation and improve system performance, especially suitable for quasi-static wireless environments with relatively stable channels and communication systems using millimeter waves, terahertz waves, visible light, and so on. The main challenge for CKM is how to construct an accurate CKM based on finite measurement data points at limited reference locations. In this work, we proposed a novel CKM construction method based on path matching and environmental partitioning (PMEP-CC) to address the above issues. Specifically, we first sort the propagation paths between reference locations, map them to a high-dimensional space to establish the path correlation coefficient between two reference locations. Then, the communication region are divided into different subregions based on its spatial correlation. Finally, the path information at locations where no measurements are available are estimated based on the known path information within the subregion to construct CKM. Numerical results are provided to show the performance of the proposed method over related studies. [ABSTRACT FROM AUTHOR]

In order to improve the quality of millimeter wave communication in indoor environment and ensure the maximum use of link resources. It is proposed to construct indoor communication transmission characteristics through multi sphere link model and indoor millimeter wave reflection blocking model. At the same time, the improved PMVC algorithm and CTRA algorithm are used to optimize the resource scheduling of links in indoor central scenes and edge scenes respectively. The simulation results show that compared with the original PVC algorithm and greedy algorithm, PMVC has a maximum link throughput of 5.01 Gbps under the optimized scheduling of the improved vertex coloring algorithm, while the maximum throughput of the traditional vertex coloring algorithm and greedy algorithm are 4.73 Gbps and 4.57 Gbps respectively. In the case of fixed link transmission beam width, as the number of link flows increases, the slot throughput of the link decreases continuously. Under the width of 30, the maximum slot throughput of PMVC algorithm is 2.75 Gbps, and the maximum slot throughput of greedy algorithm is 2.48 Gbps; When the beam width is 60, the maximum slot throughput of PMVC algorithm and greedy algorithm is 2.25 Gbps and 1.55 Gbps respectively. The proposed PMVC resource scheduling method can effectively alleviate the shortage of indoor spectrum resources and reduce indoor transmission interference of millimeter wave. [ABSTRACT FROM AUTHOR]

To improve the spectral efficiency and bit error ratio performance in the millimeter wave massive multiple input multiple output (MIMO) systems, a hybrid precoding optimization algorithm was proposed based on joint sparsity. According to the sparseness property of the millimeter wave channel in the angular domain, the lobe channel was reconstructed, and the hybrid precoding design was divided into multiple sub-problems for each lobe subchannel. To solve the sparse reconstruction problem with nonconvex constraints, the implicit sparse structure of digital precoding matrix was used to design the self-support set and common support set of analog precoding matrix for each data stream. Based on the correlation between analog precoding matrix and digital precoding matrix, the analog precoder and the digital precoder were jointly optimized. The computation complexity analysis and simulation analysis were completed. The results show that compared with the OMP algorithm, the proposed algorithm exhibits remarkable 91% or 93% reduction in computational complexity with enhancing spectral efficiency and bit error ratio performance when compared to the SLD algorithm. [ABSTRACT FROM AUTHOR]

Millimeter wave (MMW) frequencies are becoming vital as they bolster a large number of applications requiring higher data rates. In this paper, we have demonstrated a frequency multiplication technique based on external modulation for a 160 GHz MMW signal generation. The proposed scheme which uses a four-stage cascaded structure of polarization modulators proves to be a lucrative solution since the selected modulation index of 2.826 is phenomenally low. A precise choice of phase shifts between the cascaded stages ensures two eighth-order peaks spaced 160 GHz apart. This technique renders Radio Frequency Spurious Suppression Ratio and Optical Sideband Suppression Ratio of 45 and 65 dB, respectively. Simulation results are verified from a mathematical standpoint. The requirement of a Radio Frequency Local Oscillator with a higher frequency has been eliminated by a higher value of frequency multiplication factor. [ABSTRACT FROM AUTHOR]

Aiming at the high computational cost of traditional compressed sensing algorithms, this paper proposed a sparse imaging algorithm based on depth expansion model from the perspective of sparse signal recovery. Firstly, it constructed a complex sparse reconstruction network VAMP-Net. In VAMP-Net, it divided complex regressive echo signal into real part and imaginary part as input. Secondly, it substituted the input into the iterative block based on VAMP algorithm. Finally, it carried out the optimal nonlinear sparse transformation by convolutional neural module to obtain the recovered real part and imaginary part signals, and then merged them to obtain the restored target image. As for the proposed algorithm, this paper used artificial data sets to conduct simulation experiments under different target density, iteration times and noise environment, and compared with the traditional iterative shrinkage threshold algorithm and deep learning reconstruction algorithm. Then it used the measured data with different sparsity for field measurement verification. Experimental results show that the image reconstructed by this algorithm has better performance in NMSE, TBR, reconstruction speed and memory usage. [ABSTRACT FROM AUTHOR]

The hollow waveguides with angular deformation are widely used in high power millimeter wave system. In this manuscript, the cutoff wave number of the quad-polar waveguide with a boundary of R = R 0 (1 + h cos ⁡ 4 φ) is theoretically analyzed based on the perturbation analysis. Using the boundary condition and the orthogonal properties of the trigonometric functions, a determinant is obtained and then the exact closed-form expression of cutoff wave number is deduced from the determinant. Based on the cutoff wave number, the eigen field is calculated by nonlinear programming method. The values of the cutoff wavenumbers, eigen fields and surface currents for the first few modes are calculated and compared with the results obtained from simulation software. The high correspondence of the calculated values with the simulated results proves that the proposed method is an appropriate option for fast and precise analyzing quad-polar waveguides. [ABSTRACT FROM AUTHOR]

Passive millimeter-wave imaging systems (PMWIS) are employed for detecting concealed objects by mapping millimeter waves emitted from materials or living tissues. The emitted waves are measured by a receiver or radiometers without employing external wave sources. In this paper, a new super-heterodyne receiver front-end of a PMWIS at 35 GHz with an even order band pass filter is simulated and implemented. The receiver has a suitable temperature resolution for the use of hidden object imaging, is integrated and lightweight assembled on one-layer board. It has a bandwidth of 1.5 GHz, a noise figure (NF) of 2.2, and a temperature resolution of 0.126 K. The even order filter is implemented based on the substrate-integrated waveguide (SIW) technology, with Chebyshev response. The filters are designed at the central frequency of 35 GHz with the bandwidth of 1.5 GHz and one of them has controllable transmission zeroes. The filters are made by printed circuit board technology, employing SIW as resonators, having a high-quality factor of 23.33. Additionally, a triple-stage radio frequency (RF) low noise amplifier has been implemented having the specification of: RF 34.25–35.75 GHz; bandwidth 1.5 GHz; gain >60 dB; NF <2.3 dB, which are better indexes compared to some other works. [ABSTRACT FROM AUTHOR]

In a millimeter-wave terminal device, the use of a radome degrades the radiating performance of the broadside antenna, especially for the MIMO antenna system. In this study, a dielectric cover is de-signed and investigated to enhance the broadside gain of a millimeter-wave MIMO antenna, while keeping its wideband and high isolation performance. Firstly, a compact wideband ladder-shaped slot antenna is proposed with 21.9% bandwidth. The effectiveness of the dielectric cover design criteria over the wideband antenna is investigated. Then, this wideband antenna element is expanded to a 2 × 2 MIMO antenna by forming a center-symmetric structure and isolating it via the inserted metal vias. By loading the dielectric cover, this millimeter-wave MIMO antenna is verified with enhanced broadside gain for more than 2.1 dB. With the measured impedance bandwidth of 21.9% (57.0–71.0 GHz), peak broadside gain of 12.3 dBi, and high isolation over 15 dB, the proposed MIMO antenna is suitable for wireless gigabit terminal devices. [ABSTRACT FROM AUTHOR]

In this paper, a compact and simplified geometry monopole antenna with high gain and wideband is introduced. The presented antenna incorporates a microstrip feedline and a circular patch with two circular rings of stubs, which are inserted into the reference circular patch antenna to enhance the bandwidth and return loss. Roger RT/Duroid 6002 is used as the material for the antenna, and has overall dimensions of WS × LS = 12 mm × 9 mm. Three designs of two-port MIMO configurations are derived from the reference unit element antenna. In the first design, the antenna element is placed parallel to the reference antenna, while in the second design, the element is placed orthogonal to the reference element of the antenna. In the third design, the antenna elements are adjusted to be opposite each other. In this study, we analyze the isolation between the MIMO elements with different arrangements of the elements. The MIMO configurations have dimensions of 15 mm × 26 mm for two of the cases and 15 mm × 28.75 mm for the third case. All three MIMO antennas are made using similar materials and have the same specifications as the single element antenna. Other significant MIMO parameters, including the envelope correlation coefficient (ECC), diversity gain (DG), channel capacity loss (CCL), and mean effective gain (MEG), are also researched. Additionally, the paper includes a table summarizing the assessment of this work in comparison to relevant literature. The results of this study indicate that the proposed antenna is well-suited for future millimeter wave applications operating at 28 GHz. [ABSTRACT FROM AUTHOR]

Uplink communication across the water–air interface holds great potential for offshore oil surveys and military applications. Among the various methods available for implementing uplink communication, translational acoustic-RF (TARF) communication stands out due to its ability to withstand wave interference and exhibit low absorption losses. However, the physical processes underlying such systems are currently under-researched, and channel models for evaluating its communication performance indicators are lacking. Herein, we propose a signal-to-noise ratio (SNR) channel model for evaluating the performance metrics of an uplink communication system combining acoustic and millimeter waves for the first time and validate the accuracy of the proposed model through experiments. Specifically, in the process of model construction, the physical process of the communication system was deeply studied, and the corrections of multipath effects, box vibrations, and second-order nonlinear coefficients of the amplitude of the water surface were realized. The water-to-air cross-medium communication system was built, and communication experiments were conducted to validate the feasibility of combining acoustic and millimeter wave communication. This research provides a theoretical and experimental foundation for the design and evaluation of TARF communication systems, providing valuable guidance for enhancing the system's performance metrics and promising an innovative approach for modern seaborne communication. [ABSTRACT FROM AUTHOR]

At present, the traditional channel estimation algorithms have the disadvantages of over-reliance on initial conditions and high complexity. The bacterial foraging optimization (BFO)-based algorithm has been applied in wireless communication and signal processing because of its simple operation and strong self-organization ability. But the BFO-based algorithm is easy to fall into local optimum. Therefore, this paper proposes the quantum bacterial foraging optimization (QBFO)-binary orthogonal matching pursuit (BOMP) channel estimation algorithm to the problem of local optimization. Firstly, the binary matrix is constructed according to whether atoms are selected or not. And the support set of the sparse signal is recovered according to the BOMP-based algorithm. Then, the QBFO-based algorithm is used to obtain the estimated channel matrix. The optimization function of the least squares method is taken as the fitness function. Based on the communication between the quantum bacteria and the fitness function value, chemotaxis, reproduction and dispersion operations are carried out to update the bacteria position. Simulation results show that compared with other algorithms, the estimation mechanism based on QBFO-BOMP algorithm can effectively improve the channel estimation performance of millimeter wave (mmWave) massive multiple input multiple output (MIMO) systems. Meanwhile, the analysis of the time ratio shows that the quantization of the bacteria does not significantly increase the complexity. [ABSTRACT FROM AUTHOR]

Reconfigurable intelligent surface (RIS) is emerging as a promising technology to achieve coverage enhancement. This paper develops a tractable analytical framework based on stochastic geometry for performance analysis of RIS-assisted millimeter wave networks. Based on the framework, a two-step cell association criterion is proposed, and the analytical expressions of the user association probability and the coverage probability in general scenarios are derived. In addition, the closed-form expressions of the two performance metrics in special cases are also provided. The simulation results verify the accuracy of the theoretically derived analytical expressions, and reveal the superiority of deploying RISs in millimeter wave networks and the effectiveness of the proposed cell association scheme to improve coverage. Furthermore, the effects of the RIS parameters and the BS density on coverage performance are also investigated. [ABSTRACT FROM AUTHOR]

Wireless communications need antennas of different sizes, shapes, frequency-bands, bandwidths, and radiation patterns due to technical requirements, physical constraints, and FCC (Federal Communication Commission) regulations. For example, S-band antennas (2 GHz-4 GHz) are used in navigation, C-band antennas (4 GHz-8 GHz) used in Air-borne RADAR, X (8-12) band antennas used in Satellite communications, and millimeter wave (40 GHz and above) antennas used in autonomous vehicles. ultra-wideband (UWB) antennas of different frequency bands have also applications in different fields such as medical imaging, radar imaging, software defined radios, surveillance, and health monitoring of different equipment. Microstrip patch antennas of different gains, bandwidths, shapes, and radiation patterns will play a vital role in different wireless applications of future 6G systems. In this paper, we have discussed different novel designs of patch antennas at different frequency bands: V-shaped patch antenna @2.4 GHz, and hexagonal slotted half-circular patch antenna @4.29 GHz. We have designed antennas of different shapes for different frequencies since some applications require UWB; some applications require narrow band but higher gain; and some applications require different gain/radiation patterns at the same frequency. We have designed a patch antenna @2.4 GHz that can be used in Wi-Fi, and UWB patch @4.29 GHz with omnidirectional radiation pattern that can be used in energy harvesting or biomedical applications. In this paper, we have also discussed the prototype development and testing results of the novel hexagonal slotted half-circular patch antenna @4.29 GHz. [ABSTRACT FROM AUTHOR]

This study presents a parametric analysis of the steady-state temperature elevation in rat skin models due to millimeter wave exposure at frequencies from 6–100 GHz. The statistical data of the thickness of skin layers, namely epidermis, dermis, dermal white adipose tissue, and panniculus carnosus, were measured for the first time using the excised tissues of real male Sprague–Dawley rats. Based on the precise structure obtained from the histological analysis of rat skin, we solve the bioheat transfer equation to investigate the effects of changes in parameters, such as body parts and thermal constants, on the absorbed power density and temperature elevation of biological tissues. Owing to the notably thin dermal white adipose tissue layer, the surface temperature elevation in the rat head and dorsal skin at 6–100 GHz is 52.6–32.3% and 83.3–58.8% of the average values of different human skin models, respectively. Our results also reveal that the surface temperature elevation of rat skin may correlate with the tissue thickness and deep blood perfusion rates. [ABSTRACT FROM AUTHOR]

Crop divider toes are an essential device of sugarcane harvester. Moving forward against the ground is a critical way to improve the harvesting rate of lodged sugarcane. Height detection is the basis for precise control of crop divider toes moving forward against the ground. Due to the current problem of operating difficulties in manually adjusting the height of crop divider, a height detection system based on a millimeter wave radar sensor was designed to detect the height of crop divider toes from the ground. This paper proposed a height detection method of crop divider toes for sugarcane harvester based on Kalman adaptive adjustment. The data measured by the sensor was pretreated to determine whether the height had changed. Reset the Kalman filter and adjust the parameters when changes occur to improve the filter response speed and ranging accuracy. To adapt to the scenario of quickly adjusting the height of crop divider during the traveling process of sugarcane harvester. A one-way ANOVA test and a two-way ANOVA test were conducted on a simulated test platform. The results of the one-way ANOVA test showed that both forward speed and vegetation cover thickness had a significant effect on height detection accuracy. The results of the two-way ANOVA test showed that the interaction of forward speed and vegetation cover thickness did not have a significant effect on ranging accuracy. It was verified through experiments that both the ranging accuracy and the response speed of height change were significantly improved after the processing of the method in this paper. The mean square error after processing was lower than 2.5 cm. The feasibility of the height detection system was verified by field trials. The results of this study will provide a reference for the design of automatic elevation of crop divider. [ABSTRACT FROM AUTHOR]

In this paper, we present a systematic approach for the development of application-specific antennas for 5G millimeter-wave (mmWave) base stations. First, an in-depth analysis of 5G mmWave base stations considering the required antenna gain and antenna elements to address different equivalent isotropic radiated power requirements is presented. This is followed by an evaluation of the realistic impact of different factors, which affect mmWave communication, namely output power of power amplifiers, antenna gain, losses and weather condition (rain), on transmission ranges between base station and terminals, considering the link budget analysis for an Urban Macro cell with the Non-Line-of-Sight transmission, as an example. Finally, based on a comparative analysis of published dual-band dual-polarized 5G mmWave antennas, we propose a novel configuration of a dual-band dual-polarized antenna for 5G mmWave base station applications, which overcomes the limitations of conventional antennas in published literature. Our proposed antenna covers the specified 3 GHz bandwidths in the 5G mmWave n257 and n260 bands and reaches approximately 6 and 6.7 dBi, respectively in these bands. Furthermore, it exhibits at least 20 dB isolation between the polarizations and has dimensions of 1.8 3 1.8 3 1.2 mm. We modeled, simulated, fabricated, measured and analyzed this new antenna configuration. Excellent correlation is obtained between measurement and simulation results. [ABSTRACT FROM AUTHOR]