Radio Detection Research Articles

Optically transparent graphene-based cognitive metasurface for adaptive frequency manipulation

Optically transparent microwave absorbing metasurfaces have shown great potential and are needed in multiple applications environments containing optical windows owing to their ability to reduce backscattering electromagnetic (EM) signals while keeping continuous optical observation. Meanwhile, they are also required to have adaptive EM manipulation capability to cope with complex and capricious EM environments. As a general approach, distributed circuit components, including positive-intrinsic-negative diodes and varactors and sensing components, are integrated with passive absorbing metasurfaces to realize adaptive control of microwave absorption. However, these circuit elements generally require bulky electrical wires and complex control circuits to regulate the operating state, resulting in the absorbing structures being optically opaque. Hence, it is a great challenge to realize self-operating absorbers while maintaining optical transparency. Here, we report an optically transparent cognitive metasurface made of patterned graphene sandwich structures and a radio frequency detector, which can achieve adaptive frequency manipulation to match incident EM waves. As a proof-of-principle application example, we realize a closed-loop automatic absorber system prototype of the proposed graphene metasurface with self-adaptive frequency variation, without any human intervention. The approach may facilitate other adaptive metadevices in microwave regime with high-level recognition and manipulation and, more generally, promote the development of intelligent stealth technologies.

AGNs in post-mergers from the ultraviolet near infrared optical northern survey

ABSTRACT The kinematic disturbances associated with major galaxy mergers are known to produce gas inflows, which in turn may trigger accretion onto the supermassive black holes (SMBH) of the participant galaxies. While this effect has been studied in galaxy pairs, the frequency of active galactic nuclei (AGNs) in fully coalesced post-merger systems is poorly constrained due to the limited size or impurity of extant post-merger samples. Previously, we combined convolutional neural network (CNN) predictions with visual classifications to identify a highly pure sample of 699 post-mergers in deep r-band imaging. In the work presented here, we quantify the frequency of AGNs in this sample using three metrics: optical emission lines, mid-infrared (mid-IR) colour, and radio detection of low-excitation radio galaxies (LERGs). We also compare the frequency of AGNs in post-mergers to that in a sample of spectroscopically identified galaxy pairs. We find that AGNs identified by narrow-line optical emission and mid-IR colour have an increased incidence rate in post-mergers, with excesses of ~4 over mass- and redshift-matched controls. The optical and mid-IR AGN excesses in post-mergers exceed the values found for galaxy pairs, indicating that AGN activity in mergers peaks after coalescence. Conversely, we recover no significant excess of LERGs in post-mergers or pairs. Finally, we find that the [O iii] luminosity (a proxy for SMBH accretion rate) in post-mergers that host an optical AGN is ~0.3 dex higher on average than in non-interacting galaxies with an optical AGN, suggesting that mergers generate higher accretion rates than secular triggering mechanisms.

Radio source-component association for the LOFAR Two-metre Sky Survey with region-based convolutional neural networks

Context. Radio loud active galactic nuclei (RLAGNs) are often morphologically complex objects that can consist of multiple, spatially separated, components. Only when the spatially separated radio components are correctly grouped together can we start to look for the corresponding optical host galaxy and infer physical parameters such as the size and luminosity of the radio object. Existing radio detection software to group these spatially separated components together is either experimental or based on assumptions that do not hold for current generation surveys, such that, in practice, astronomers often rely on visual inspection to resolve radio component association. However, applying visual inspection to all the hundreds of thousands of well-resolved RLAGNs that appear in the images from the Low Frequency Array (LOFAR) Two-metre Sky Survey (LoTSS) at 144 MHz, is a daunting, time-consuming process, even with extensive manpower. Aims. Using a machine learning approach, we aim to automate the radio component association of large (>15 arcsec) radio components. Methods. We turned the association problem into a classification problem and trained an adapted Fast region-based convolutional neural network to mimic the expert annotations from the first LoTSS data release. We implemented a rotation data augmentation to reduce overfitting and simplify the component association by removing unresolved radio sources that are likely unrelated to the large and bright radio components that we consider using predictions from an existing gradient boosting classifier. Results. For large (>15 arcsec) and bright (>10 mJy) radio components in the LoTSS first data release, our model provides the same associations for 85.3% ± 0.6 of the cases as those derived when astronomers perform the association manually. When the association is done through public crowd-sourced efforts, a result similar to that of our model is attained. Conclusions. Our method is able to efficiently carry out manual radio-component association for huge radio surveys and can serve as a basis for either automated radio morphology classification or automated optical host identification. This opens up an avenue to study the completeness and reliability of samples of radio sources with extended, complex morphologies.

Design of RADAR Detection System Management with MATLAB

Abstract: Radio detection and ranging, that is, RADAR is a radio wave technique to determine the range, altitude, direction of objects. The radar dish or antenna transmits pulses of radio waves or microwaves which bounces off any object in their path. It works by launching a short pulse at the ear audible frequency, after that microcontroller listens for echoes. The information about the distance to the object is given at the time elapsed during transmission to the echo reception. The object returns a tiny part of the wave’s energy to a dish or antenna which is usually located at same site as the transmitter. High tech radar systems are associated with digital signal processing and are capable of extracting useful information from very high noise levels.

Discovery of 24 radio-bright quasars at 4.9 ≤ z ≤ 6.6 using low-frequency radio observations

High-redshift quasars (z > 5) that also shine brightly at radio wavelengths are unique signposts of supermassive black hole activity in the early universe. However, bright radio sources at z ≥ 5 are extremely rare and therefore we have started a campaign to search for new high-z quasars by combining an optical dropout selection driven by the g, r, and z bands from the Dark Energy Spectroscopic Instrument (DESI) Legacy Imaging Surveys with low-frequency radio observations from the LOFAR Two-metre Sky Survey (LoTSS). Currently, LoTSS covers a large fraction of the northern sky (∼5720 deg2) to such a depth (median noise level ∼83 μJy beam−1) that about 30% of the general quasar population is detected − which is a factor of 5–10 more than previous large sky radio surveys such as NVSS and FIRST, respectively. In this paper, we present the discovery of 20 new quasars (and the independent confirmation of four) between 4.9 ≤ z ≤ 6.6. Out of the 24 quasars, 21 satisfy the traditional radio-loudness criterion of R = f5 GHz/f4400 Å > 10, with the full sample spanning R ∼ 6–1000, thereby more than doubling the sample of known radio-loud quasars at z ≥ 5. Our radio detection requirement strongly decreases the contamination of stellar sources and allows one to select these quasars in a broad redshift range. Despite selecting our quasar candidates using fewer and less conservative colour restrictions, both the optical and near-infrared colours, Lyα emission line properties, and dust reddening, E(B − V), measurements of our quasar sample do not deviate from the known radio-quiet quasar population, suggesting similar optical quasar properties of the radio-loud and radio-quiet quasar population at high-z. Our campaign demonstrates the potential for discovering new high-z quasar populations through next generation radio continuum surveys.

Modulation leakage-free continuous-variable quantum key distribution

Distributing cryptographic keys over public channels in a way that can provide information-theoretic security is the holy grail for secure communication. This can be achieved by exploiting quantum mechanical principles in so-called quantum key distribution (QKD). Continuous-variable (CV) QKD based on coherent states, in particular, is an attractive scheme for secure communication since it requires only standard telecommunication technology that can operate at room temperature. However, a recently discovered side-channel created in the process of state preparation leads to a leakage of information about the transmitted quantum state, opening a security loophole for eavesdroppers to compromise the security of the CVQKD system. Here, we present a CVQKD system without this modulation leakage vulnerability. Our implementation is based on a baseband modulation approach and uses an in-phase and quadrature (IQ) modulator for state preparation and radio frequency heterodyne detection together with carefully designed digital signal processing for state measurement. We consider practical aspects in the implementation and demonstrate the generation of a composable secret key secure against collective attacks. This work is a step towards protecting CVQKD systems against practical imperfections of physical devices and operational limitations without performance degradation.

Mobility Sensing and V2X Communication for Emergency Services

The warning of traveling emergency response vehicles (ERVs) is performed through the help of both sound and lights when the ERV is approaching. This is not an ideal situation for, at least, two reasons: the information is received only when the ERV is very close to other vehicles; and the other vehicles cannot understand where exactly the ERV is, and which action is the best according to its location and direction. With the help of vehicular communications, this paper proposes a different approach for an ERV to be autonomously and preemptively detected. Based on the collected data through vehicle communication and sensors, primarily through Cooperative Awareness Messages (CAMs) and Radio Detection And Ranging (RADAR) data, a prediction of the ERV future location is performed in real-time, and warning messages are disseminated to vehicles just before the ERV arrival. Real-world evaluation tests, considering different warning dissemination scenarios, show that the warning messages lost during the process is significantly reduced from almost 80% down to 22%, especially when infrastructure-to-vehicle and vehicle-to-vehicle communications are used together. Moreover, 80% of the total warning messages are delivered in less than 100 ms.

Conditions for high-resolution bistatic radar observations of Apophis in 2029

ABSTRACT On 2029 April 13, asteroid Apophis will pass within six times of the Earth's radius (∼31 000 km above the surface) in the closest approach of this asteroid in recorded history. This event provides unique scientific opportunities to study the asteroid, its orbit, and surface characteristics at an exceptionally close distance. In this paper, we perform a novel synthetic geometrical, geographical, and temporal analysis of the conditions under which the asteroid can be observed from the Earth with a particular emphasis on the conditions and scientific opportunities for bistatic radar observations, the most feasible radar technique applicable during such a close approach. For this purpose, we compile a list of present and future radio observatories or radio facilities around the globe, which could participate in bistatic radar observation campaigns during the close approach of Apophis. We estimate signal-to-noise ratios, apparent sky rotation, surface coverage, and other observing conditions. We find that a global collaboration of observatories across Australia, Africa, Europe, and America will produce high-resolution delay-Doppler radar images with signal-to-noise ratios above 108, while covering ∼85 per cent of the asteroid surface. Moreover, if properly coordinated, the extreme approach of the asteroid might allow for radio amateur detection of the signals sent by large radio observatories, and citizen science projects could then be organized. We also find that for visual observations, the Canary Islands will offer the best observing conditions during the closest approach, both for professionals as well as for amateurs. The apparent size of Apophis will be 2–3 times larger than typically seeing, allowing for resolved images of the surface.

Status of the AugerPrime upgrade of the Pierre Auger Observatory

The Pierre Auger Observatory consists of a detector system to study ultrahigh-energy cosmic rays. These cosmic rays can be detected only through the observation of extensive air showers. The hybrid detection of air showers at the Observatory is based on the Surface Detector (SD) – an array of about 1660 water-Cherenkov detectors, and the Fluorescence Detector, with 27 telescopes overlooking the SD. Recently, an upgrade of the Observatory was initiated, called AugerPrime. The main purpose of the upgrade is to improve the mass composition sensitivity of the SD through precise measurements of the muonic and electromagnetic components of extensive air showers. For this purpose, additional scintillator and radio detectors are being installed on top of SD stations. The upgrade also includes updated SD electronics, and underground muon detectors. In this talk, the motivation and the current status of the upgrade will be reviewed.

Comparable Bulk Radar Attenuation Characteristics Across Both Martian Polar Layered Deposits

AbstractThe dust‐laden and predominantly water ice south polar layered deposits (SPLD) exhibit unique radar behavior at Shallow Radar (SHARAD) frequencies that is not seen in the NPLD. A vertically extensive scattering phenomenon leads to diffuse echoes that obscure radar stratigraphy within the SPLD, referred to as “fog.” Here, we use 2‐D and 3‐D SHARAD data to measure the areal extent in which the SPLD basal interface can be identified. We also measure reflected power of SPLD basal reflectors and compare those values to ice thickness, regional geomorphology, and the presence of radar echo scattering, to constrain any influence these factors may have on the propagation of radio waves and detectability of the base. Approximately 33% of the area in which the basal interface is observed in Mars Advanced Radar for Subsurface and Ionosphere Sounding data is also detected in SHARAD data. As expected, basal power shows a negative correlation with ice thickness, but the effects of radar fog are less clear. Areas of “column” radar fog patterns exhibit higher average basal power values than regions without radar fog, and areas with only near‐surface radar fog have the lowest average basal power values. Our study results suggest that these diffuse echoes may not be associated with radio wave attenuation. Average loss tangent for the SPLD (0.0019 ± 0.0012) indicates no distinguishable difference from previously reported NPLD values in terms of bulk loss properties. We speculate that the SPLD's infrequent reflections compared to the NPLD may be due to the former's dust being less densely packed together to facilitate radar detection.

Radio observations of the tidal disruption event AT2020opy: a luminous non-relativistic outflow encountering a dense circumnuclear medium

ABSTRACT Tidal disruption events (TDEs) occur when a star passes too close to a supermassive black hole and is destroyed by tidal gravitational forces. Radio observations of TDEs trace synchrotron emission from outflowing material that may be ejected from the inner regions of the accretion flow around the supermassive black hole or by the tidal debris stream. Radio detections of TDEs are rare, but provide crucial information about the launching of jets and outflows from supermassive black holes and the circumnuclear environment in galaxies. Here, we present the radio detection of the TDE AT2020opy, including three epochs of radio observations taken with the Karl G. Jansky Very Large Array, MeerKAT, and upgraded Giant Metrewave Radio telescope. AT2020opy is the most distant thermal TDE with radio emission reported to date, and from modelling the evolving synchrotron spectra we deduce that the host galaxy has a more dense circumnuclear medium than other thermal TDEs detected in the radio band. Based on an equipartition analysis of the synchrotron spectral properties of the event, we conclude that the radio-emitting outflow was likely launched approximately at the time of, or just after, the initial optical flare. We find no evidence for relativistic motion of the outflow. The high luminosity of this event supports that a dense circumnuclear medium of the host galaxy produces brighter radio emission that rises to a peak more quickly than in galaxies with lower central densities.

VLBA Reveals the Absence of a Compact Radio Core in the Radio-intermediate Quasar J2242+0334 at z = 5.9

High-resolution imaging is crucial for exploring the origin and mechanism of radio emission in quasars, especially at high redshifts. We present 1.5 GHz Very Long Baseline Array (VLBA) images of the radio continuum emission from the radio-intermediate quasar (RIQ) J2242+0334 at z = 5.9. This object was previously detected at both 1.5 GHz and 3 GHz with the Karl G. Jansky Very Large Array (VLA) as a point source. However, there is no clear detection in the VLBA images at both the full resolution of 10.7 mas × 4.5 mas (61.7 pc × 26.0 pc) and a tapered resolution of 26 mas × 21 mas (150 pc × 121 pc). This suggests that the radio emission from the quasar is diffuse on milliarcsecond scales with surface brightness fainter than the 3σ detection limit of 40.5 μJy beam−1 in the full-resolution image. The radio emission in the RIQ J2242+0334 is likely to be wind-like (i.e., diffuse) rather than in the form of collimated jets. This is different from the previous radio detections of the most luminous quasars at z ∼ 6 that are usually dominated by compact, high brightness temperature radio sources. Meanwhile, compared with RIQs at low redshifts, the case of J2242+0334 suggests that not all RIQs are beamed radio-quiet quasars. This optically faint RIQ provides an important and unique example to investigate the radio activity in the less powerful active galactic nuclei at the earliest cosmic epoch.

Spectroscopic Properties of the Astrochemical Molecules [Al, O, Si] x (x = 0, +1)

Aluminum and silicon are present in large quantities in the interstellar medium, making the triatomic species consisting of both elements intriguing with regard to the foundations of astrochemistry. Spectroscopic parameters have been calculated via high-level ab initio methods to assist with laboratory and observational detection of [Al, O, Si] x (x = 0,+1). All [Al, O, Si] x (x = 0,+1) isomers exist in the linear geometry, with linear AlOSi (X 2Π) and linear AlOSi+ (X 1Δ) being the most stable neutral and cationic species, respectively. Formation of the neutral species most likely occurs via reaction of AlO/SiO on an Si/Al dust grain surface, respectively. The cation molecules may form via ion–neutral reaction or as a consequence of photoionization. The rotational frequencies of linear AlOSi (X 2Π) have been calculated using vibrationally corrected rotational constants and centrifugal distortion to lead experimental and observational radio detection. The rotational frequencies are discussed for three temperatures indicative of various astronomical environments: the central circumstellar envelope (CSE) (100 K), outer CSE (30 K), and the interstellar medium (3 K). At 100 K, the lines originating from J′ > 30 are the best candidates for detection via ground-based telescope. Anharmonic vibrational analysis revealed various Fermi resonances that may complicate the vibrational spectrum of linear AlOSi (X 2Π). Finally, electronic spectroscopy may be the best means for laboratory detection of linear AlOSi (X 2Π), due to the presence of two overlapping electronic transitions with large oscillator strengths occurring at approximately 250 nm.

Deep-learning-based reconstruction of the neutrino direction and energy for in-ice radio detectors

Ultra-high-energy (UHE) neutrinos (>1016eV) can be measured cost-effectively using in-ice radio detection, which has been explored successfully in pilot arrays. A large radio detector is currently being constructed in Greenland with the potential to measure the first UHE neutrino, and an order-of-magnitude more sensitive detector is being planned with IceCube-Gen2. For such shallow radio detector stations, we present an end-to-end reconstruction of the neutrino energy and direction using deep neural networks (DNNs) developed and tested on simulated data. The DNN determines the energy with a standard deviation of a factor of two around the true energy (σ≈ 0.3 in log10(E)), which meets the science requirements of UHE neutrino detectors. For the first time, we are able to predict the neutrino direction precisely for all event topologies including the complicated electron neutrino charged-current (νe-CC) interactions. The obtained angular resolution shows a narrow peak at O(1°) with extended tails that push the 68% quantile for non-νe-CC (resp. νe-CC interactions) to 4°(5°). This highlights the advantages of DNNs for modeling the complex correlations in radio detector data, thereby enabling measurement of neutrino energy and direction.

Quantification of the purinergic P2X7 receptor with [11C]SMW139 improves through correction for brain-penetrating radiometabolites

The membrane-based purinergic 7 receptor (P2X7R) is expressed on activated microglia and the target of the radioligand [11C]SMW139 for in vivo assessment of neuroinflammation. This study investigated the contribution of radiolabelled metabolites which potentially affect its quantification. Ex vivo high-performance liquid chromatography with a radio detector (radioHPLC) was used to evaluate the parent and radiometabolite fractions of [11C]SMW139 in the brain and plasma of eleven mice. Twelve healthy humans underwent 90-min [11C]SMW139 brain PET with arterial blood sampling and radiometabolite analysis. The volume of distribution was estimated by using one- and two- tissue compartment (TCM) modeling with single (VT) and dual (VTp) input functions. RadioHPLC showed three major groups of radiometabolite peaks with increasing concentrations in the plasma of all mice and humans. Two radiometabolite peaks were also visible in mice brain homogenates and therefore considered for dual input modeling in humans. 2TCM with single input function provided VT estimates with a wide range (0.10–10.74) and high coefficient of variation (COV: 159.9%), whereas dual input function model showed a narrow range of VTp estimates (0.04–0.24; COV: 33.3%). In conclusion, compartment modeling with correction for brain-penetrant radiometabolites improves the in vivo quantification of [11C]SMW139 binding to P2X7R in the human brain.

The black hole X-ray binary MAXI J1348–630 in quiescence

ABSTRACT The properties of the disc/jet coupling in quiescent black hole low mass X-ray binaries (BH LMXBs) are still largely unknown. In this paper, we present the first quasi-simultaneous radio and X-ray detection in quiescence of the BH LMXB MAXI J1348–630, which is known to display a hybrid disc/jet connection that depends on the accretion rate. We performed deep X-ray and radio observations using the Chandra X-ray Observatory and the Australia Telescope Compact Array. MAXI J1348–630 is detected for the first time in quiescence at an X-ray luminosity LX = (7.5 ± 2.9) × 1030(D/2.2 kpc)2 erg s−1: one of the lowest X-ray luminosities observed for a quiescent BH LMXB, possibly implying a short orbital period for the system. MAXI J1348–630 is also detected in radio at LR = (4.3 ± 0.9) × 1026(D/2.2 kpc)2 erg s−1. These detections allow us to constrain the location of MAXI J1348–630 on the radio/X-ray diagram in quiescence, finding that the source belongs to the standard (radio-loud) track in this phase. This provides a strong confirmation that hybrid-correlation sources follow the standard track at low luminosities and down to quiescence, thus improving our knowledge of the disc/jet connection in BH LMXBs.

Radio monitoring of transient Be/X-ray binaries and the inflow–outflow coupling of strongly magnetized accreting neutron stars

ABSTRACT Strongly magnetized (B ≥ 1012 G) accreting neutron stars (NSs) are prime targets for studying the launching of jets by objects with a solid surface; while classical jet-launching models predict that such NSs cannot launch jets, recent observations and models argue otherwise. Transient Be/X-ray binaries (BeXRBs) are critical laboratories for probing this poorly explored parameter space for jet formation. Here, we present the coordinated monitoring campaigns of three BeXRBs across four outbursts: giant outbursts of SAX 2103.5+4545, 1A 0535+262, and GRO J1008–57, as well as a Type-I outburst of the latter. We obtain radio detections of 1A 0535+262 during ten out of twenty observations, while the other targets remained undetected at typical limits of 20–50 $\mu$Jy. The radio luminosity of 1A 0535+262 positively correlates with its evolving X-ray luminosity, and inhabits a region of the LX–LR plane continuing the correlation observed previously for the BeXRB Swift J0243.6+6124. We measure a BeXRB LX–LR coupling index of β = 0.86 ± 0.06 ($L_R \propto L_X^\beta$), similar to the indices measured in NS and black hole low-mass X-ray binaries. Strikingly, the coupling’s LR normalization is ∼275 and ∼6.2 × 103 times lower than in those two comparison samples, respectively. We conclude that jet emission likely dominates during the main peak of giant outbursts, but is only detectable for close-by or super-Eddington systems at current radio sensitivities. We discuss these results in the broader context of X-ray binary radio studies, concluding that our results suggest how supergiant X-ray binaries may host a currently unidentified additional radio emission mechanism.

Sensor-Based Prognostic Health Management of Advanced Driver Assistance System for Autonomous Vehicles: A Recent Survey

Recently, the advanced driver assistance system (ADAS) of autonomous vehicles (AVs) has offered substantial benefits to drivers. Improvement of passenger safety is one of the key factors for evolving AVs. An automated system provided by the ADAS in autonomous vehicles is a salient feature for passenger safety in modern vehicles. With an increasing number of electronic control units and a combination of multiple sensors, there are now sufficient computing aptitudes in the car to support ADAS deployment. An ADAS is composed of various sensors: radio detection and ranging (RADAR), cameras, ultrasonic sensors, and LiDAR. However, continual use of multiple sensors and actuators of the ADAS can lead to failure of AV sensors. Thus, prognostic health management (PHM) of ADAS is important for smooth and continuous operation of AVs. The PHM of AVs has recently been introduced and is still progressing. There is a lack of surveys available related to sensor-based PHM of AVs in the literature. Therefore, the objective of the current study was to identify sensor-based PHM, emphasizing different fault identification and isolation (FDI) techniques with challenges and gaps existing in this field.

Analysis of mobile phone radiation effect on human body using specific absorption rate

The use of mobile phones is rising everyday both in civic and rustic areas in Bangladesh. Every mobile phone disperses electromagnetic energy. This radiation or electromagnetic wave can penetrate into the human body. Specific absorption rate and change in temperature are the vital parameter to find the dominant effects assess on the human body. This paper explores the radiation impact of mobile phones. A mathematical equation is used to evaluate the local specific absorption rate and change in temperature at Skin, Fat, Bone, Brain, Eye, Muscle tissues at the frequency of 800MHz, 900 MHz, 1800 MHz, 2100 MHz, 2.5GHz, 2.6GHz, 3.4GHz, 3.5GHz, and 3.6GHz. The calculations are performed at different distances and exposure times of mobile phone. A simple radio frequency detection circuit has been designed to find the radiated power of different frequency. The highest specific absorption rate is calculated for skin, brain, eye tissue. Child tissue absorption rate is higher than the adult. When the radiated power of mobile phone is high the specific absorption rate for different tissue cross the safety limit. This paper also recommends the ways to diminish the effects of SAR. It is suggested that these methods will decrease the health risks. This work will be very helpful to understand the bad effect of using mobile phones and the way of reducing this effect.

Carbon-based radar absorbing materials: A critical review

With the development of radar (Radio Detection and Ranging) systems, the study of materials with the capability to block and reduce the reflected electromagnetic radiation to avoid or confuse detection systems, or to protect sensitive devices and living beings exposed to electromagnetic radiation, has become a topic of great interest. This review describes some concepts of the electromagnetic spectrum, radar systems, frequency bands, and radar applications based on their operating frequency, the radar cross-section, and the mechanisms to reduce it, as well as the microwave absorption theory. Furthermore, different carbon-based materials such as carbon black, carbon fibers, nanotubes, graphene, graphene oxide, reduced graphene oxide, and its composites have been used as electromagnetic absorber materials due to their remarkable intrinsic characteristics as lightweight, flexibility, and suitable electric and magnetic properties, are described. This review also explains the principal mechanisms by which these materials can attenuate the radiation. The review is concluded with a summary of the perspectives and challenges for future investigation of carbon-based materials and his electromagnetic characterization for radar signals absorption, interference protection and human security.