RCS Values Research Articles

Design of Engineered Reflectors for Radar Cross Section Modification

A technique is proposed for the design of engineered reflectors consisting of doubly periodic arrays printed on thin grounded dielectric substrates that reflect an incoming wave from a given incoming direction to a predetermined outgoing direction. The proposed technique is based on a combination of Floquet theory for propagation in periodic structures and reflect-array principles. A flat surface designed to reflect a TE polarized wave incident at 45° back in the direction of the impinging signal at 14.7 GHz is employed as an example. By means of full-wave simulations, it is demonstrated that the monostatic RCS of a finite reflector is comparable with the specular RCS of a metallic mirror of the same dimensions. It is further shown that comparably high monostatic RCS values are obtained for angles of incidence in the 30°-60° range, which are frequency dependent and thus open opportunities for target localization. A prototype array is fabricated and experimentally tested for validation. The proposed solution can be used to modify the radar cross section of a target. Other potential applications are also discussed.

수정된 HHT 기법을 이용하여 회전하는 프로펠러 날개에 의한 마이크로 도플러 신호의 해석

본 논문에서는 시간-주파수 동시 해석 기법 중 하나인 수정된 HHT 기법을 이용하여 회전하는 프로펠러의 날개에서 산란되는 마이크로 도플러 신호를 분석하였다. 프로펠러의 날개 모서리에 산란되는 산란파는 등가전류법(ECM)을 이용하여 구했다. 산란파의 시간 데이터를 얻은 후, 수정된 HHT 기법을 마이크로 도플러 신호의 해석에 적용하였다. 해석 결과는 실제 날개의 동특성에 잘 부합하였으며, 회전체로부터 발생하는 마이크로 도플러의 정편파적인 특성을 보였다. 수정된 HHT를 이용한 시간-주파수 동시 해석은 작은 레이더 단면적 값을 갖는 소형 비행체를 식별하기 위한 명확한 특성을 제공하였다. This paper has presented the analysis of the micro-Doppler signatures scattered from the blades of the rotating propeller using the modified HHT method, one of the joint time-frequency analysis methods. The field scattered from the blade edge of the propeller was calculated using equivalent current method(ECM). After the acquisition of the scattered field data in the time domain, the modified HHT method was applied to analyze the micro-Doppler signature. The analysis results showed not only a good agreement with the realistic dynamic characteristic of the blade but also sinusoidally varing characteristics of the micro-Doppler signatures generated from rotating objects. It could be concluded that the joint time-frequency analysis via the modified HHT provided the discriminative characteristics for recognizing a small aircraft target with small RCS value.

Application of Artificial Neural Network for Clutter Rejection

This paper deals with application of Artificial Neural Network (ANN) for Radar Clutter rejection, function approximation method of supervised ANN is applied here using back propagation algorithm. The database used for training and testing the ANN has been collected from simulating a moving vehicle in MATALAB(version 7.9) to obtain the RCS values at range and cross-range profiles. This work is validated by comparing received signal after clutter rejection with the received signal in no clutter condition.

RCS PREDICTION FROM PLANAR NEAR-FIELD MEASUREMENTS

It is well-known that, at low frequency, far-field RCS can be measured using a suitable implementation such as outdoor range or large anechoic chamber. The aim of this paper is to propose a new algorithm to predict RCS from near-field measurements. The comparison between RCS values obtained from the proposed method and those obtained from direct far-field values shows a good agreement between the two results.

NUMERICAL INVESTIGATION ON DYNAMIC RADAR CROSS SECTION OF NAVAL SHIP CONSIDERING OCEAN WAVE-INDUCED MOTION

In design phase of naval ships, the efiectiveness of RCS reduction means such as shaping, shielding and applying radar absorbing materials is assessed quantitatively via several times of numerical analyses. During the process, in general, the numerical analyses have been carried out only for the static case not considering ship motions in actual ocean environments in spite that ocean waves induce the ship motion of the object naval ship and distort RCS measures. In this study, the dynamic RCS characteristics of the naval ship considering the ocean wave-induced motion have been numerically investigated. For this purpose, a dynamic RCS analysis procedure so called \quasi-static approach has been adopted for considering the time varying ship motion. The results for two types of naval ships, a stealthy and a non-stealthy ship, show that the RCS of the object naval ships could be reduced or increased in mean value by the ship motion due to the ocean wave, compared to the static RCS value, and also the measures are considerably afiected by the various parameters, type of object ship, signiflcant wave height and incident angle of ocean wave, and incident angle of radar wave.

An ultra‐wideband fractal slot antenna with low backscattering cross section

AbstractIn this article, an ultra‐wide modified Koch fractal antenna is proposed.Simulated and measured results show that the bandwidth of −10 dB return loss is from 2.7 GHz to more than 15 GHz. The radiation patterns are comparatively symmetrical at both 3 and 8 GHz. Moreover, this novel antenna has low backscattering cross section compared with the initial square slot antenna. The backscattering cross section values of the two antennas with different load are also presented to make the achievement of the RCS values with arbitrary load possible. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1150–1154, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25915

급이 및 비급이 참돔의 색, 맛 및 영양성분 비교

Division of Marine Bioscience/Institute of Marine Industry, Gyeongsang National University, Tongyeong 650-160, KoreaAbstractFor the effective use of cultured red seabream, the muscle color, taste and nutrition components between red seabreams cultured by feeding and starving were compared. The proximate composition of red seabream muscle cultured by starving (RCS) was 72.7% moisture, 21.1% protein, 3.7% lipid and 1.4% crude ash. In comparison to red seabream muscle cultured by feeding (RCF), moisture and crude lipid of RCS were each 3% higher and 3% lower. No difference was, however, found in the other proximate compositions. The Hunter color value of RCS was 37.52 for L value, -1.47 for a value, 0.71 for b value and 59.33 for ΔE value, which was slightly higher in the L value than that of red seabream muscle cultured feeding (RCF); however, no differences were found in the other Hunter color values. TCA soluble-N content of RCS was 403.8 mg/100 g, which was higher than that of RCF (314.7 mg/100 g). In taste values, the major free amino acids of both RCS and RCF were glutamic acid, alanine, lysine and histidine. Total amino acid content of RCS was 21.2 g/100 g, which was higher than that of RCF. The mineral content of RCS was slightly higher in potassium than that of RCF, while lower in magnesium. According to the result of sensory evaluation, RCS was superior in taste and texture to RCF, while similar in color and flavor.Key words: red seabream, starved red seabream, sliced raw fish, starved fish

A practical millimeter-wave radar calibration target

A simple rectangular-plate millimeter-wave radar calibration target gives RCS values ranging from hundreds to thousands of square meters. This enable tests over extended ranges and with equipment having modest output power. Precise mechanical alignment mechanisms and an optical sight are mandatory, due to the narrow beamwidth. Absorber collars provide an easy way of adjusting the actual RCS according to specific mission requirements, and effectively reduce edge-diffraction effects. The measured V-band calibration uncertainty was less than 0.5 dB, and the pointing resolution was better than 0.05/spl deg/.

Digital communications using self-phased arrays

A new technique for full duplex digital communications using adaptive phase conjugation is presented in this paper. The technique is based on mixing the RF signal to an IF where it can be easily processed, and filtering the phase of the IF signal to separate the geometry phase and message phase. The retrodirective array automatically tracks communicating platforms and transmits a directive return signal without the use of phase shifters. A 6-GHz microstrip retrodirective antenna array was built, together with the signal IF processing needed for full duplex operation. The measured RCS values of a linear six-element array are in good agreement with theory and result in a 0- to -5-dB RCS for angles up to /spl plusmn/60/spl deg/. The measured RCS values of a circular array are much flatter and are 0 to -5 dB up to /spl plusmn/80/spl deg/. Two-way digital communications at a baud rate of 78 kb/s was also demonstrated with BER<10/sup -6/ for signal-to-noise ratios around 10 dB. The application areas are in high-performance digital mobile telecommunications for commercial and military applications.

Polarimetric characterization of debris and faults in the highway environment at millimeter-wave frequencies

In this paper, measurements and models for the polarimetric backscatter response of various paint targets on roads and road surface faults are presented. Of particular interest are debris and faults that could lead to fatal accidents and damage of property. A desired safety feature for automotive radar sensors is the capability of detecting such debris and faults. The detectability of a point target is evaluated by comparing its RCS value with the RCS threshold value defined by the backscatter response of the road surface. Extensive backscatter measurements at W-band were conducted to obtain the backscatter response of typical debris and faults on asphalt surfaces at near grazing incidence angles (76/spl deg/-86/spl deg/). On the other hand, theoretical models, based on diffraction from impedance wedges and scattering from impedance cylinders, respectively, as well as physical optics approximation, were developed to predict the backscatter response of road surface faults and targets with planar facets on road surfaces. Experimental results indicate that detectability in all cases is a function of target size, its azimuthal angle with respect to radar boresight, and the polarization state of the system. The measured backscatter response is used to verify the validity of the theoretical models. Angular polarimetric backscatter measurements of targets defining roadside boundaries such as a concrete curb, a guardrail, and a pebble surface are also presented. The results of these measurements could be used to alert fatigued drivers should their vehicles be heading sideward.

The optimizing research about radar absorbent material parameters

From the Physical Optics theory (PO) and Leontovich Impedance Boundary Condition (IBC), We research RCS reduction (RCSR) of multilayer dielectric and magnetic medium on different shape conductors such as plate, cuboid and cone by use of Matlab programs. Some available RCS data and graph results are given. These show the connection between Radar Absorbent Material (RAM) parameters and the number of layers. In the mean time, the relation between RAM optimized parameters and RCS value is also shown. It has better practical significance.

Combining the moment method with geometrical modelling by NURBS surfaces and Bezier patches

Induced current distributions on conducting bodies of arbitrary shape modelled by NURBS (non uniform rational B-splines) surfaces are obtained by using a moment method approach to solve an electric field integral equation (EFIE). The NURBS surfaces are expanded in terms of Bezier patches by applying the Cox-de Boor transformation algorithm. This transformation is justified because Bezier patches are numerically more stable than NURBS surfaces. New basis functions have been developed which extend over pairs of Bezier patches. These basis functions can be considered as a generalization of "rooftop" functions. The method is applied to obtain RCS values of several objects modelled with NURBS surfaces. Good agreement with results from other methods is observed. The method is efficient and versatile because it uses geometrical modelling tools that are quite powerful.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

On the derivation of bistatic RCS from monostatic measurements

The factors which govern bistatic scattering are discussed and the relations between bistatic and monostatic scattering are presented in terms of the combined effect of individual scattering centers on the target. The concept of reradiation lobe patterns of the individual scattering centers is used to define the bistatic pattern in terms of the monostatic pattern and the bistatic angle β. Analytical arguments then demonstrate that for small bistatic angles, the bistatic RCS is very closely approximated by the monostatic RCS measured on the bisector of the bistatic angle and measured at a frequency lower than the true frequency by the factor cos β/2. The limitations to this approximation which are based on the angular width of the lobe patterns reradiated from individual scattering centers are noted. The approximation is of particular value in translating measured monostatic RCS values into bistatic RCS for small bistatic angles.

New cryogenic container

The initial results of a two year simultaneous optical-radar meteor campaign are described. Analysis of 105 double-station optical meteors having plane of sky intersection angles greater than 5° and trail lengths in excess of 2 km also detected by the Middle Atmosphere Alomar Radar System (MAARSY) as head echoes was performed. These events show a median deviation in radiants between radar and optical determinations of 1.5°, with 1/3 of events having radiant agreement to less than one degree. MAARSY tends to record average speeds roughly 0.5 km/s and 1.3 km higher than optical records, in part due to the higher sensitivity of MAARSY as compared to the optical instruments. More than 98% of all head echoes are not detected with the optical system. Using this non-detection ratio and the known limiting sensitivity of the cameras, we estimate that the limiting meteoroid detection mass of MAARSY is in the 10−9–10−10 kg (astronomical limiting meteor magnitudes of +11 to +12) appropriate to speeds from 30 to 60 km/s. There is a clear trend of higher peak RCS for brighter meteors between 35 and −30 dBsm. For meteors with similar magnitudes, the MAARSY head echo radar cross-section is larger at higher speeds. Brighter meteors at fixed heights and similar speeds have consistently, on average, larger RCS values, in accordance with established scattering theory. However, our data show RCS ∝ v/2, much weaker than the normally assumed RCS ∝ v3, a consequence of our requiring head echoes to also be detectable optically. Most events show a smooth variation of RCS with height broadly following the light production behavior. A significant minority of meteors show large variations in RCS relative to the optical light curve over common height intervals, reflecting fragmentation or possibly differential ablation. No optically detected meteor occurring in the main radar beam and at times when the radar was collecting head echo data went unrecorded by MAARSY. Thus there does not appear to be any large scale bias in MAARSY head echo detections for the (comparatively) larger optical events in our dataset, even at very low speeds.