Target observability improvement in multi-static maritime forward scatter radar

The forward scatter signature of a target provides the radar systems designer with an alternative approach to the detection of 'very low radar cross section (RCS)' targets. This paper outlines the rationale for a forward scatter radar system, the forward scatter principle, and the architecture of a forward scatter radar systems performance model. This model has been developed to analyse the effect of variations in the choice of operating frequency, transmitter and receiver characteristics, detection and tracking algorithms. The paper discusses these aspects with results from modelling and performance predictions for target forward scatter signature, transmit and receive antenna designs, analogue to digital converter (ADC) performance and coverage for a forward scatter radar system operating in the ultra high frequency (UHF) band.

This letter presents a compact dual-polarized over-the-air testing antenna with low radar cross section (RCS) for the fifth-generation and emerging wireless communication systems. The proposed antenna design is achieved by slotting two orthogonal Vivaldi antennas in a cross-shaped form into a two-part three-dimensional printed radome and loading microwave-absorbing materials (MAMs) at the antenna's outer edges. The proposed antenna has a rocket-nest shape with a diameter of 63.4 and 113.68 mm length. The -10 dB impedance bandwidth (S11) is obtained from a range of 2.1 up to 6 GHz. The two-part radome is formed by polylactic acid and acrylonitrile butadiene styrene dielectric materials, respectively. Their respective dielectric constants are approximately 2.6 and 4.5 within the -10 dB impedance bandwidth. The MAMs geometry and distribution location are optimized to suppress induced current over the antenna. An antenna prototype has been fabricated and measured. The measured results agree reasonably well with the simulated results. The results show that the use of the two-part radome enables the achievement of low RCS with compact form factor. Furthermore, a low bistatic RCS of between 2 and 6 GHz is observed in simulation for angular ranges of θ ∈ [-30°, +30°] and Φ ∈ [-90°, +90°].

Radar detection of small maritime targets is of great interest in the context of coastal and port security for prevention of activities such as smuggling and piracy. Multistatic radar and forward scatter radar offer detection advantages compared with conventional monostatic systems, such as advantageous multi-perspective target view for the former and target radar cross-section enhancement for the latter. In this study, experimental results are presented to characterise simultaneous measurements investigating the detection of a small inflatable boat by a multistatic radar and a forward scatter radar. These results are believed to be the first example of simultaneous experimental comparison of such systems.

A shared aperture metamaterial (SA-MTM) with partially reflection and absorber characteristics is presented. The SA-MTM is composed of two metallic layers separated by a dielectric spacer; the top absorbing surface (AS) consists of oblique cross metallic pattern loaded with lumped resistances, and the bottom partially reflecting surface (PRS) consists of etched parallel slots in a metallic layer. An SA-MTM with partial reflection and absorption characteristics is fulfilled by making the absorbing surface and partially reflecting surface shared the same aperture in the vertical direction. The SA-MTM is applied to the waveguide slot antenna; the Fabry-Perot resonance cavity constructed by the PRS and the metallic ground layer of the waveguide slot antenna can achieve high gain, while the AS can obtain the low radar cross section (RCS) characteristic antenna by absorbing the incident wave. Simulation and experimental results demonstrate that the antenna with SA-MTM gain is enhanced above 3 dB in the operation frequency range, the backscattering RCS is obviously reduced in a frequency range of 2–9 GHz. This idea can help us design a high gain and low RCS antenna, which overcomes the conflict between scattering and radiation performance of antenna.

The use of a monostatic radar for the detection of cosmic rays was first suggested by Blackett and Lovell in 1941. Over the years that followed it became clear that this type of radar would require extremely high power transmitters and high gain antennas for its operation. The low Radar Cross Section (RCS) is due to the details of electromagnetic wave scattering by the ionization electrons in the dense terrestrial atmosphere. A less known type of radar, bistatic radar, exhibits a strong enhancement in the RCS at forward directions. We present results of expected received power calculations for a bistatic radar used in the detection of extensive cosmic ray showers. The rapid movement of the shower front followed by extinction of ionization by electronegative oxygen contributes to the formation of a phase modulated signal at the receiver. The signal frequency versus time signature is characteristic for the ionization produced by extensive cosmic ray showers and will provide an optimal discrimination against spurious events.

In this work, an anisotropic metasurface (MS) is proposed for independent wave manipulation of radiation and scattering, which realizes high gain radiation and low radar cross section (RCS) by the excitation of spoof surface plasmon polariton (SSPP). The presented MS consists of anisotropic unit cells, which exhibit reflected mode and transmitted mode for x and y polarization, respectively. Besides, x-polarized reflection phase and y-polarized transmission phase can be independently changed in a wide range by varying structural parameters of the unit cell. By integrating with a conventional microstrip antenna, the proposed MS realizes y-polarized high-gain radiation of 15.3 dB, gain enhancement of 8.84 dB, and RCS reduction of more than 10 dB from 22 to 26GHz by the excited SSPPs in the simulation.

Ground clutter rejection requirements imposed on the exciter transmitter-receiver units of multirole airborne radar are examined. Methods are given to determine the characteristics of the units, such as noise, spurious spectral lines level, and analog-to-digital converter (ADC) dynamics, in both high- and medium-pulse-repetition-frequency modes of operation. It is shown that the spectral noise does not depend on either the wave form or the Doppler bandwidth. The reference oscillator spectral noise must be about -155 dB/sub c//Hz. The level of spurious lines generally depends only on the duty cycle, and the requirement is -80 dB/sub c/ for each line. ADC requires 12 to 14 b. The high-frequency mode is the most promising for detecting targets with very low radar cross sections in head-on configuration (free clutter domain).< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

This communication presents an approach to design a beam-steerable dipole array with low radar cross section (RCS). A 2-D periodical array of dipole antennas is colocated with absorptive frequency-selective reflection (AFSR) structures to effectively reduce the out-of-band RCS and maintain high gain at the in-band frequencies. The AFSR structures consist of 3-D bandstop frequency-selective structure (FSS) and pyramidal-shaped absorbers to provide a reflection band for the dipole array with enhanced front-to-back ratio. Compared with the reference array, the radiation performance of the proposed array is maintained with an aperture efficiency of 70% and a measured peak gain of 21.5 dBi. The beam-steering angle is up to ±45°. Meanwhile, more than 10 dB two-sided out-of-band RCS reduction is achieved with a bandwidth of 96.5% and 30% for copolarization and 142% for cross polarization, and the in-band RCS is unchanged.

In this article, a planar wideband circularly polarized (CP) slot antenna array based on metasurface (MS) with low radar cross section (RCS) is proposed. The array is comprised of CP MS‐based antennas fed with a sequentially rotated feeding network. For each CP antenna, the CP radiation is achieved due to polarization conversion of the MS. Simultaneously, the total MS patches of the array can be viewed as checkerboard composed of MS array and mirror array. A phase difference between the MS units and the mirror units ensures RCS reduction. Simulated results demonstrate that about 34.6% operating bandwidth in the frequency of 4.3–6.1 GHz (both S11 –10 dB and AR &lt; 3 dB). In addition, over 5 dB RCS reduction is obtained in the entire operation band under normal incidence with respect to the array without MS for both x‐ and y‐polarizations. The simulated monostatic RCS less than −30.9 dBsm is observed at 5.0 GHz. A prototype of the array is fabricated and measured, which are in good agreement with simulated results.

This paper presents an analysis of the LFM pulse compression technique as an integral part of signal processing in surveillance radars. The theoretical analysis of the work rests on the concepts of intrapulse modulation and matched filter, essential elements for increasing the radar resolution. Simulations of dense Electronic Warfare scenarios were also conducted to evaluate the applicability of LFM pulse compression in surveillance radars by the investigation of their ability to distinguish very close targets with low radar cross sections. The results of the graphical analyzes allowed the confirmation of the high operational value of the technique.

This paper discusses the system concept for a compact three dimensional (3D) millimeter wave radar system for tracking fast moving objects with low radar cross section (RCS). The concept contains two orthogonally arranged two dimensional (2D) scanning radar frontends operating in a fast time-multiplexed mode. The 2D scanning is achieved by FMCW based operation of frequency steering meander-line antennas, which allow very fast generation of 2D scans of the monitored area. Both 2D scans are then combined into a three dimensional representation of the monitored area and therefore the tracking of fast moving objects in single target scenarios is possible.

A phase controllable rasorber, also named as phase controllable absorptive frequency-selective transmission (AFST) surface, is developed in this paper. It is composed of asymmetrical resonators with lumped resistors, achieving an absorption-transmission-absorption response. Compared with other reported rasorbers, the proposed one has an additional feature that is to realize a 1-bit phase change of its element within the transmission band by rotating the element by 90°. A low radar cross section (RCS) transmitarray is designed at 12.5 GHz with a peak realized gain of 24.4 dBi using the developed elements. The 10 dB RCS reduction bandwidths are 18% and 14% for the lower and upper absorption bands, respectively.

A variety of unmanned air vehicles (UAVs) have been developed for both military and civilian use. The typical large UAV is typically state owned, whereas small UAVs (SUAVs) may be in the form of remote controlled aircraft that are widely available. The potential threat of these SUAVs to both the military and civilian populace has led to research efforts to counter these assets via track, ID, and attack. Difficulties arise from the small size and low radar cross section when attempting to detect and track these targets with a single sensor such as radar or video cameras. In addition, clutter objects make accurate ID difficult without very high resolution data, leading to the use of an acoustic array to support this function. This paper presents a multi-sensor architecture that exploits sensor modes including EO/IR cameras, an acoustic array, and future inclusion of a radar. A sensor resource management concept is presented along with preliminary results from three of the sensors.

Detecting and tracking small drones is significant for security requirements, but is challenging since small drones typically have a low radar cross section (RCS), small size, and hovering ability. Polarimetric analysis of returned radio wave is of great significance in detection and track of small drones. In this letter, the polarimetric analysis based on RCS and micro-Doppler signature of small drone rotor blade is first studied in VHF/UHF band. Both the simulated and measured RCS results confirm that the horizontal–horizontal polarization is preferred for drone detection in low-altitude angles at this frequency band. Moreover, the method of moments, a rigorous numerical method based on integral equation, is implemented to simulate the micro-Doppler signature generated by the rotating blade in VHF/UHF band. The results show that it is feasible to obtain the rotating speed from the micro-Doppler measurement, which is also verified by the experiment.

Classifying buried and obscured targets of interest from other natural and manmade clutter objects in the scene is an important problem for the U.S. Army. Targets of interest are often represented by signals captured using low-frequency (UHF to L-band) ultra-wideband (UWB) synthetic aperture radar (SAR) technology. This technology has been used in various applications, including ground penetration and sensing-through-the-wall. However, the technology still faces a significant issue regarding low-resolution SAR imagery in this particular frequency band, low radar cross sections (RCS), small objects compared to radar signal wavelengths, and heavy interference. The classification problem has been firstly, and partially, addressed by sparse representation-based classification (SRC) method which can extract noise from signals and exploit the cross-channel information. Despite providing potential results, SRC-related methods have drawbacks in representing nonlinear relations and dealing with larger training sets. In this paper, we propose a Simultaneous Decomposition and Classification Network (SDCN) to alleviate noise inferences and enhance classification accuracy. The network contains two jointly trained sub-networks: the decomposition sub-network handles denoising, while the classification sub-network discriminates targets from confusers. Experimental results show significant improvements over a network without decomposition and SRC-related methods.