Military Radar Research Articles

Temperature-mechanically reconfigurable bidirectional multifunctional metasurface

In this paper, we propose a temperature-mechanically reconfigurable bidirectional multifunctional metasurface based on vanadium dioxide, which can operate in both forward and backward working modes and function as a reflective absorber in terahertz frequency range, as well as a reflective and transmissive polarization converter. In the forward mode, by mechanically rotating the top polarization modulation layer at the temperature of over 340 K, the metasurface can switch between reflective linear polarization (LP) converter and absorber. When the metasurface works as a reflective LP converter, the polarization conversion rate exceeds 90 % in 0.75–1.15 THz. Also, the LP wave can be converted to the right-handed circularly polarized (RHCP) wave at 0.56 THz; when the metasurface is utilized as an absorber, the absorptivity is above 90 % in 1.14–1.21 THz and reaches a peak of 95.6 % at 1.18 THz. In the backward mode, the metasurface can act as a transmissive polarization converter and an absorber at the room temperature. When the metasurface as a transmissive polarization converter, the LP wave is converted to the RHCP wave at 1.0 THz; when it works as an absorber, the absorptivity is over 90 % in 1.20–1.61 THz. Through temperature regulation and mechanical reconfiguration, the metasurface can achieve bidirectional multifunction including absorption, linear and circular polarization conversion, which is expected to be applied in antennas, electromagnetic stealth, military radar, terahertz communication, detection and other scenarios.

Statistical Signal Processing for Radar Systems

Through measurable models, "Factual Flag Handling for Radar Frameworks" goes into detail around the progressed procedures and strategies utilized to see at and progress radar information. This field employments thoughts from both measurable hypothesis and flag preparing to unravel difficult issues in radar framework execution, like finding targets, taking after them, and speculating what they are. This article talks approximately distinctive factual models and strategies that can be utilized with radar. These incorporate Bayesian gauges, versatile sifting, and theory testing. This paper talks around how factual apparatuses can be utilized to create radar frameworks more precise, dependable, and clear by mimicking and decreasing the impacts of commotion, impedances, and outside components. Creating factual flag preparing methods for lessening disarray, distinguishing targets, and estimating parameters are a few of the foremost critical subjects. Other imperative points incorporate ways to analyze and get it radar information in genuine time. It gives a careful see at both the hypothetical bases and real-world applications, appearing how measurable strategies can be utilized to make strides radar framework capabilities. There are case thinks about and real-life examples that appear how these strategies can be utilized totally different radar circumstances, such as military, flying machine, car, and climate radars. This book gives engineers and understudies the instruments they got to move forward radar framework plan and execution in settings that are getting more complicated and changing rapidly by combining factual flag preparing with radar innovation.

Evaluation of a double-lens dielectric radome using a microstrip patch antenna for electromagnetic applications

The advancement of increasingly powerful antennas has increased the complexity of radome electromagnetic (EM) design and analysis. The antenna systems are protected from environmental influences by radomes, which are dielectric and electromagnetically transparent structures. Because the presence of the radome affects the performance parameters of the antenna, such as the radiation pattern, reflected power, and side lobe level, its design should not be done independently of the antenna analysis. The great majority of ground-based hemispherical radomes are used for satellite communication antennas, commercial and military radars, telemetry systems, and other uses. Patch antennas, reflector antennas, phased array radars, and other antenna systems are used in these applications. The operational effectiveness of a radome architecture for housing multiple patch antenna systems is proposed and evaluated. The proposed line of work includes antenna-radome interaction analyses, electromagnetic designs for radome walls, and radiation patterns for reflector antennas. COMSOL Multiphysics was used to develop the EM radome and examine the antenna-radome interaction. The findings of a comprehensive analysis into the differences in radiation patterns produced by patch antennas with and without radomes are presented in this article. At a frequency of 1.62 GHz, a plot and investigation of the far-field gain of the microstrip patch antenna with and without radome were done. The radome is estimated to add 0.09 dBi to the gain boost experienced by the microstrip patch antenna.Abbreviations: EM, Electromagnetic; DSF, Dielectric space frame radome; IFR, Induced field ratio; RF, Radio frequency; VSWR, Voltage standing wave ratio; FEM, Finite element method; SRR, Split ring resonator; CATR, Compact antenna test range; DUT, Device being tested; LHM, Left-handed metamaterials; PML, Perfectly matched layer; PTFE, Polytetrafluoroethylene.

Automatic Extraction of VLF Constant‐Frequency Electromagnetic Wave Frequency Based on an Improved Vgg16‐Unet

AbstractConstant Frequency Electromagnetic Waves (CFEWs) refer to electromagnetic waves with a constant frequency. Man‐made CFEWs are mainly used in wireless communication, scientific research, global navigation and positioning systems, and military radar. CFEWs exhibit horizontal line characteristics higher than the background on spectrograms. In this study, we focus on Very Low Frequency (VLF) waveform data and power spectral data collected by the China Seismo‐Electromagnetic Satellite (CSES) Electromagnetic Field Detector (EFD). We utilize deep learning techniques to construct an improved Vgg16‐Unet model for automatically detecting horizontal lines on time‐frequency spectrogram and extracting their frequencies. First, we transform waveform data into time‐frequency spectrogram with a duration of 2 s using Short‐Time Fourier Transform. Then, we manually label horizontal lines on the time‐frequency spectrogram using the Labelme tool to establish the dataset. Next, we establish and improve the Vgg16‐Unet deep learning model. Finally, we train and test the model using the dataset. Statistical experimental results show that the error rate of line detection is 0, indicating high reliability of the model, with fewer parameters and fast computation speed suitable for practical applications. Not only do we detect lines through the model, but we also obtain their frequencies. Additionally, in batch‐generated power spectrogram of CFEWs, we discover some unstable phenomena such as frequency shifts and fluctuations, which contribute to understanding the propagation mechanism of CFEWs in the ionosphere and improving the accuracy of related systems.

Joint Antenna Scheduling and Power Allocation for Multi-Target Tracking under Range Deception Jamming in Distributed MIMO Radar System

The proliferation of electronic countermeasure (ECM) technology has presented military radar with unprecedented challenges as it remains the primary method of battlefield situational awareness. In this paper, a joint antenna scheduling and power allocation (JASPA) scheme is put forward for multi-target tracking (MTT) in the distributed multiple-input multiple-output (D-MIMO) radar. Aiming at radar resource scheduling in the presence of range deception jamming (RDJ), the false target discriminator is designed based on the Cramer–Rao lower bound (CRLB) in terms of the spoofing range, and the predicted conditional CRLB (PC-CRLB) plays a role in evaluating tracking accuracy. The JASPA scheme integrates the quality of service (QoS) principle to develop an optimization model based on false target discrimination, with the objective of enhancing both the discrimination probability of false targets and the tracking accuracy of real targets concurrently. Since the optimal variables can be separated in constraints, a four-step optimization cycle (FSOC)-based algorithm is developed to solve the multidimensional non-convex problem. Numerical simulation results are provided to illustrate the effectiveness of the proposed JASPA scheme in dealing with MTT in the RDJ environment.

Microwave assisted cobalt nickel ferrite as exhaust thrust sensor and EMI shield

Spinel ferrites have garnered an increasing share of attention in recent decades. The fact that these substances are employed in a wide range of applications, such as electromagnetic interference interference (EMI) shielding and sensor technology. Exhaust thrust sensors have an increasing demand in exhaust air circulator of automobile engine. In the present article Co0.5Ni0.5Fe2O4 (CNF) is synthesized by ceramic route and are sintered using microwaves. The structural, optical, magnetic and morphology are studied using X-ray diffraction, Ultraviolet (UV) visible, Vibrating sample magnetometer (VSM) and scanning electron microscopy (SEM). The magnetic initial permeability as a function of temperature has exhibited quasi single domain grain behaviour. Large stress response and exhaust pressure sensitivity are noticed for the bulk as well as micro inductor fabricated suggesting a plausible application as exhaust thrust sensor applications. The CNF exhibits a high total shielding effectiveness of 55.96 dB, suggesting that almost 99.999% of incoming electromagnetic radiation is effectively reduced by this material. Spinel ferrite CNF have excellent electromagnetic shielding in microwave region and making it very useful for military (radar and stealth) and electronic industries.

High‐Performance Fully Transparent Ultraviolet Photodetector Fabricated Using GaN‐Based Schottky Barrier Photodiode

Transparent electronics is a burgeoning field with exciting potential for next‐generation “see‐through” devices. The creation of high‐performance fully transparent ultraviolet photodetectors (PDs) is essential for enabling wearable and portable applications. In this study, metal–semiconductor–metal (MSM) type Al‐doped ZnO (AZO)/GaN/AZO and indium tin oxide (ITO)/GaN/ITO‐transparent ultraviolet PDs, are initially designed, utilizing AZO‐ and ITO‐transparent conductive electrodes. In these investigations, it is revealed that AZO and ITO form Ohmic and Schottky contacts, respectively, with GaN. Subsequently, building on these findings, a fully transparent Schottky barrier photodiode (SBPD) is developed for ultraviolet photodetection using AZO/GaN/ITO. The SBPD displays a high responsivity (R) of 1.41 × 103 A W−1, a detectivity (D*) of 6.85 × 1014 Jones, and a photo‐to‐dark current ratio exceeding 1 × 104 at a − 5 V bias. Furthermore, the SBPD demonstrates an ultrahigh responsivity of 1.18 A W−1 at 0 V bias, indicating its potential as a self‐powered device under extreme conditions. In these results, the tremendous potential of the high‐performance and fully transparent GaN‐based SBPD is demonstrated for environmental monitoring, optical communication, military radar, and other fields.

Theoretical and Experimental Investigation of N-Bit Reconfigurable Retrodirective Metasurface

The PIN diode-based N-bit reconfigurable retrodirective metasurface (N-bit RRDM) is a next-generation retro-reflector that offers the advantages of effective electronical control of the retro-reflection angle, low loss, and thin planar structure. However, since the unit cell of an N-bit RRDM is controlled by a quantized N-bit phase (360°/2<sup>N</sup>), it encounters operational errors, such as beam gain reduction and spurious beams. This can be a fatal disadvantage in military radar or satellite communication, which requires accurate beam tracking. This paper theoretically analyzes the operation of the N-bit RRDM by utilizing generalized Snell’s law and array factor theory. The analysis results present the design criteria for an N-bit RRDM that eliminates issues related to beam gain reduction and spurious beam errors. Furthermore, to verify the theoretical analysis results, High-Frequency Structure Simulator (HFSS) full-wave simulation and experimentation are conducted using the 1-bit RRDM.

Ongoing legacy contamination from a military radar station in Iceland: a case study

The Dew line radar station at Heidarfjall in 1958 (https://www.radomes.org/museum/acwgrnland.php).

Potential Effects of Anthropogenic Radiofrequency Radiation on Cetaceans

Cetaceans are cast to shore for a large number of reasons, although sometimes it is not clear why. This paper reviews the types and causes of cetacean strandings, focusing on mass strandings that lack a direct scientific explanation. Failure of cetacean orientation due to radiofrequency radiation and alterations in the Earth’s magnetic field produced during solar storms stand out among the proposed causes. This paper proposes the possibility that anthropogenic radiofrequency radiation from military and meteorological radars may also cause these strandings in areas where powerful radars exist. A search of accessible databases of military and meteorological radars in the world was carried out. Research articles on mass live strandings of cetaceans were reviewed to find temporal or spatial patterns in the stranding concentrations along the coast. The data showed certain patterns of spatial and temporal evidence in the stranding concentrations along the coast after radar setup and provided a detailed description of how radars may interfere with cetacean echolocation from a physiological standpoint. Plausible mechanisms, such as interference with echolocation systems or pulse communication systems, are proposed. This work is theoretical, but it leads to a hypothesis that could be empirically tested. Further in-depth studies should be carried out to confirm or reject the proposed hypothesis.

DESIGN OF A SPECIAL SYSTEM (TRANSMITTER-ANTENNA) FOR ANTENNA MEASUREMENTS USING A UAV

In civilian and military radars and communication systems, antennas of various purposes are used, in particular, in the meter range of waves. Meter-band antennas are large pieces of equipment, often covering areas of 30 meters or more. In the article, there are reasons for the need to measure antennas, their features and requirements for the equipment. The structure of the developed transmitter, circuit solutions, obtained parameters and their comparative analysis are presented. Conclusions are drawn regarding the use of the created facilities.

Ultra-Thin Fss Based Radar Absorbing Structure For X-Band Applications

Radar Absorbing Structures (RAS) are widely used in defense applications in order to reduce the electromagnetic reflections from predominant hotspots. With majority of military radars operating in X-band, thin frequency selective absorbers catering to this frequency range are the need of the hour especially for airborne platforms. In this regard, a novel ultra-thin Frequency Selective Surface (FSS) based RAS with superior absorption performance in the frequency range of 8GHz to 12GHz is presented. The absorption characteristics and radar cross-section (RCS) of the RAS has been analysed using commercially available EM simulation software. Further, the ultra-thin RAS, with a thickness of 0.053l at the centre frequency, has been fabricated and the performance parameters have been measured. The measurement results show that the percentage of power absorbed by the proposed RAS is greater than 90% over majority of X-band. In addition, it provides atleast 8dB RCS reduction (RCSR) in monostatic as well as bistatic modes of operation in comparison with its metallic counterpart of identical dimensions.

Electromagnetic attenuation displayed by La-Co substituted Ba-Sr hexaferrite nanoparticles and multiwall carbon nanotubes in polyaniline and polythiophene matrix

Our presented research aims to provide a systematic study of electrical, magnetic and microwave absorption properties of La-Co substituted Ba-Sr hexaferrite nanoparticles and MWCNTs, encapsulated in conductive polymer matrix. La-Co substituted Ba-Sr hexaferrite nanoparticles were produced using Sol-Gel auto combustion, whereas carrier fluid ultrasonication dispersion and in-situ polymerization were used to synthesize their composites with multiwall carbon nanotubes (MWCNTs) and conductive polymers. Structural investigations were accomplished using X-rays diffraction, secondary electron microscopy, Infrared and Raman Spectroscopy. The dielectric measurements revealed increased dielectric losses (4.86 at 1 GHz for pure nanoparticles, which increases up to 11.59 and 13.36 for ternary composites within PANI and PTh matrix), indicating good energy dissipation behavior. The decrease in magnetism was observed due to the weakening of exchange coupling or domain wall pinning at the interface of Ferrite-MWCNTs and Ferrite-Polymer, resulting in lowered saturation magnetization, remanence and coercivity values. The microwave absorption of our samples was evaluated as a function of frequency and thickness, revealing its dependence on the quarter wavelength phenomenon with maximum reflection loss of − 40.4 dB observed for ternary composite with Polythiophene matrix at 7.54 GHz resonance frequency. The dependence of reflection loss peaks on matching thickness was analyzed using calculated thickness profiles, revealing their close agreement with simulated thickness. The study highlighted the potential of synthesized samples for electromagnetic signature reduction, in both commercial and military applications. The resonance bands were found to coincide with the operating frequency of military radars for shipborne and airborne surveillance and navigation in the X band (8–12 GHz).

IMPLEMENTATION OF DIGITIZATION ELEMENTS AS A SOLUTION OF RISK MANAGEMENT IN MAINTENANCE OF RADIOLOCATION SYSTEMS

We increasingly identify in our lives the presence of devices equipped with recording cameras, as well as facial recognition to unlock devices. At the same time, we notice the increasing presence of technologies capable of identifying different objects, manoeuvres or actions, as well as detecting actions performed in error. This article highlights how these digital devices can be integrated to improve the quality of maintenance and to achieve effective risk management in this sensitive segment of military RaDaR technology and equipment. The data acquisition elements (CWB/AR) can produce records that can be uploaded to a secure government cloud, which can be accessed by teams of appropriately skilled and qualified technicians. An IA structure can be adequately trained to notice, highlight and alert in case of deviations from the maintenance protocol, thus achieving quality management of the monitored equipment.

Lightweight Co3O4/CC Composites with High Microwave Absorption Performance.

With the rapid development of electronic and communication technology for military radars, the demand for microwave-absorbing materials in the low-frequency range with thin layers is growing. In this study, flexible Co3O4/CC (carbon cloth) composites derived from Co-MOFs (metal-organic frameworks) and CC are prepared using hydrothermal and thermal treatment processes. The flexible precursors of the Co-MOFs/CC samples are calcined with different calcination temperatures, for which the material structure, dielectric properties, and microwave absorption performance are changed. With the increases in calcination temperature, the minimum reflection loss of the corresponding Co3O4/CC composites gradually moves to the lower frequency with a thinner thickness. In addition, the Co3O4/CC composites with the 25 wt% filler loading ratio exhibit the minimum reflection loss (RL) of -46.59 dB at 6.24 GHz with a 4.2 mm thickness. When the thickness is 3.70 mm, the effective absorption bandwidth is 3.04 GHz from 5.84 to 8.88 GHz. This study not only proves that the Co3O4/CC composite is an outstanding microwave-absorbing material with better flexibility but also provides useful inspiration for research on wideband microwave absorption materials below 10 GHz.

Encapsulation of Ba–Sr hexaferrite nanoparticlesand MWCNTs in conductive polymer matrix for improved dielectric spectroscopy, electromagnetic shielding and microwave absorption applications

Ba–Sr hexaferrite nanoparticles were produced using Sol-Gel auto combustion, whereas carrier fluid ultrasonication dispersion and in-situ polymerization were used to synthesize their composites with MWCNTs and conductive polymers. Structural investigations were accomplished using X-rays diffraction, secondary electron microscopy, Infrared and Raman Spectroscopy. The low frequency dielectric measurements revealed increased dielectric losses (304 at 100 Hz for pure nanoparticles, which increases up to 2721 and 7861 for ternary composites within polyaniline and Polythiophene matrix), indicating good energy dissipation behavior. The diminishing magnetism resulted from the weakening of exchange coupling or domain wall pinning at the interface of Ferrite-MWCNTs and Ferrite-Polymer, causing the shifting of magnetic resonance peak towards lower frequency in the shielding effectiveness (Absorption) plots. Increasing DC conductivity adds to the nominal increase of Shielding effectiveness (Reflection) values owing to the rise in charge carrier conduction. The maximum total shielding effectiveness, perceived for the composition of Ba0.5Sr0.5Fe12O19/MWCNTs/Polythiophene, was −34 dB and −33 dB at 8.1 GHz and 16.2 GHz, respectively. The microwave absorption of our samples was evaluated as a function of frequency and thickness, revealing its dependence on the quarter wavelength phenomenon with maximum reflection loss of −39 dB observed for ternary composite with Polythiophene matrix at 7.4 GHz resonance frequency. The resonance bands coincide with the operating frequency of military radars for shipborne and airborne surveillance and navigation in the X band.

Designing and Judd-Ofelt evaluation of versatile luminescent Eu (III) complexes sensitized with β-diketone ligand for multifarious applications.

The present research work entails synthesis of one binary and four ternary red light emitting Eu (III) based complexes with 3-benzylidene-2,4-pentanedione as main ligand and 1,10-phenanthroline, bathophenanthroline, neocuproine and 4,4'-dimethyl-2,2'-bipyridyl as auxiliary ligands. The Metal-Organic framework of the series was elucidated using EDAX, elemental analysis, FT-IR and 1 H-NMR. This Eu (III) series exhibit optimum thermal stability making them a promising candidate for OLED's. On the basis of emission spectra their optical parameters such as non-radiative and radiative decay rate, luminescence decay time, intrinsic quantum efficiency and Judd-Ofelt intensity parameter were determined. The mono-centric luminescence and Judd-Ofelt parameters reveals the non-existence of symmetry around the europium center. CIE chromaticity coordinates, CCT values, color purity and asymmetric ratios authenticate the color coordinates of complexes in red region. Optical band gap values lies within wide band gap semiconductors range revealing their utilization in military radars, biological labeling.

Switchable multifunctional terahertz metamaterial with slow-light and absorption functions based on phase change materials

Terahertz (THz) wave usually refers to the electromagnetic wave with a frequency between 0.1—10.0 THz. It has potential applications in wireless communication, biomedical image processing, nondestructive testing, military radar, and other fields. However, owing to function limitation of the natural material, multifunctional terahertz devices are difficult to design and fabricate, which becomes a bottleneck for THz technology. The emergence of metamaterials fills the gap in the electromagnetic materials in the THz frequency band, and now they are widely used in THz functional devices, such as THz modulators, THz absorbers, THz filters, THz sensors, and THz slow-light devices. However, the above-mentioned THz devices all have a single function. For practical application, multifunction integrated THz devices have broader application prospects. As is well known, the Ge<sub>2</sub>Sb<sub>2</sub>Te<sub>5</sub> (GST) is a typical phase transition material. Under excitation of light or electronic field, GST can realize a reversible phase transition between insulating state and metallic state. In order to achieve a switchable multifunctional THz device, in this work we design a THz metamaterial based on the phase transition material GST and realize a switchable function with slow-light and absorption functions. The THz metamaterial consists of a microstructure layer, which is composed of gold rings arranged periodically, and a GST thin film spaced by an SiO<sub>2</sub> dielectric layer. When GST is in an insulating state, the two gold rings are coupled to each other under the excitation of the THz pulse. Then, we can observe the EIT-like effect. The THz pulses propagating in the metamaterial we proposed can be slowed down, and a maximum group delay of the THz pulse can reach 3.6 ps. However, when GST is in a metallic state, we can observe two absorption peaks in the spectrum of the proposed THz metamaterial, and the absorption rate is 97% at a frequency of 0.365 THz and 100% at a frequency of 0.609 THz. Furthermore, we also investigate the polarization properties of the proposed THz metamaterial, and find that it has polarization insensitive characteristic. When the polarization angle of the incident THz light pulse changes from 0° to 90°, the slow-light and absorption properties of the THz metamaterial are unaffected. The proposed THz metamaterial has potential applications in THz biomedical image processing, THz optical switching, and THz optical buffer.

Vesper Flights: New and Collected Essays

This book comprises forty-one essays, some of them about solar eclipses, space stations, mushrooms, and refugees, but the majority focus on animals, mostly birds. Macdonald starts each piece with a personal recollection from childhood or adulthood. “Vesper Flights,” for instance—the essay that gives the book its title—begins: “I found a dead swift once, a husk of a bird under a bridge over the River Thames. . . . I picked it up, held it in my palm . . . and realised that I didn't know what to do.” The author continues by setting out the little that she did know, before that encounter, about swifts—she knew only that they are very difficult to observe individually because of the velocity and the height of their flights. To her, the swifts had always been like “aliens on earth.”Those birds are known for their peculiar flights at dusk, when they go up almost vertically into the sky. Scientists used to believe that they went up to sleep; but, at the end of the 1970s, in order to study the interaction between birds and airplanes, Luit Buurma of the Netherlands made radar observations that showed the swifts do not sleep at high altitude. The hypothesis of Buurma and other scientists is that they go up to forecast the weather. In the convective boundary layer, the winds are unaffected by geographic components, and, at that altitude, the swifts may also orient themselves better, thanks in part to the polarized light that is clearest at twilight. “What they are doing,” Macdonald summarizes these findings, “is flying so high they can work out exactly where they are, to know what they should do next.”Macdonald was trained in the history of science, which explains her taste for telling stories in which she explains how we come to know other animal species. She stresses the importance of technical devices in the construction of knowledge (without military radar, scientists would never have known where the swifts were flying). In each chapter, she also underscores the problem of what she aptly calls “multispecies social etiquette”: it is such a problem (how to avoid collisions with birds, a particular kind of social interaction) that moved scientists to study swifts in the first place. I much enjoyed reading these parts of each chapter. I was less convinced, however, by the morals that she draws from animal behaviors—for example: “Swifts are my fable of community, teaching us about how to make right decisions in the face of oncoming bad weather, in the face of clouds that sit like dark rubble on our horizon.” What makes me uncomfortable with such general conclusions is that they could as well be reached without the birds.

A Survey on Citizens Broadband Radio Service (CBRS)

To leverage the existing spectrum and mitigate the global spectrum dearth, the Federal Communications Commission of the United States has recently opened the Citizens Broadband Radio Service (CBRS) spectrum, spanning 3550–3700 MHz, for commercial cognitive operations. The CBRS has a three-tier hierarchical architecture, wherein the incumbents, including military radars, occupy the topmost tier. The priority access licenses (PAL) and general authorized access (GAA) are second and third tier, respectively, facilitating licensed and unlicensed access to the spectrum. This combination of licensed and unlicensed access to the spectrum in a three-tier model has opened novel research directions in optimal spectrum sharing as well as privacy preservation, and hence, several schemes have been proposed for the same. This article provides a detailed survey of the existing literature on the CBRS. We provide an overview of the CBRS ecosystem and discuss the regulation and standardization process and industrial developments on the CBRS. The existing schemes for optimal spectrum sharing and resource allocation in CBRS are discussed in detail. Further, an in-depth study of the existing literature on the privacy of incumbents, PAL devices, and GAA devices in CBRS is presented. Finally, we discuss the open issues in CBRS, which demand more attention and effort.