Classical Radar Research Articles

Noise vs. Deterministic Waveform Radar—Possibilities and Limitations

Classical radars use deterministic waveforms, such as linear frequency modulated pulses. Noise radars, on the other hand, use random waveforms, or waveforms that resemble random signals. The randomness of the signal provides certain advantages, such as limiting or avoiding range/velocity measurement ambiguity, or better resistance to jamming. This, however, comes at a price of more complicated system architecture and reduced detection range. In this article a comparison of classical deterministic waveform radars and their noise versions is carried out, showing their similarities and differences.

Entanglement Sustainability in Quantum Radar

In this study, some important parts of a quantum radar are designed using the quantum electrodynamics theory and significantly focused on entanglement conservation. Quantum radar is generally defined as a detection sensor that utilizes the microwave photons like a classical radar and simultaneously employs quantum phenomena to improve detection, identification, and resolution capabilities. However, the entanglement is so fragile, unstable, and difficult to preserve for a long time. Also, more importantly, the entangled states have a tendency to leak away due to the noise. The points mentioned enforces that the entangled states should be carefully studied at each step of the quantum radar detection processes such as the creation of the entangled photons in the tripartite system, the amplification of the photons, the propagation into the atmosphere, and the reflection from the target. At each step, the parameters related to the real mediums and target material can affect the entangled states to leak away easily. The results of simulations indicate that the features of the tripartite system and amplifier are so important to lead the detected photons to remain entangled with the optical modes. Nonetheless, it is found that a lot of entangled photons lose the related non-classical correlation.

The Quantum Illumination Story

Superposition and entanglement, the quintessential characteristics of quantum physics, have been shown to provide communication, computation, and sensing capabilities that go beyond what classical physics will permit. It is natural, therefore, to explore their application to radar, despite the fact that decoherence—caused by the loss and noise encountered in radar sensing—destroys these fragile quantum properties. This article tells the story of “quantum illumination,” an entanglement-based approach to quantum radar, from its inception to its current understanding. Remarkably, despite loss and noise that destroy its initial entanglement, quantum illumination does offer a target-detection performance improvement over a classical radar of the same transmitted energy. A realistic assessment of that improvement's utility, however, shows that its value is severely limited. Nevertheless, the fact that entanglement can be of value on an entanglement-breaking channel—the meta-lesson of the quantum illumination story—should spur continued research on quantum radar.

Millimeter wave imaging using sparse arrays

In this paper, we develop a theoretical framework for short-range millimeter (mm) wave radar imaging using a sparse array of monostatic elements, and validate it via experiments. The framework is a significant departure from classical radar, which largely focuses on long-range settings in which targets are well modeled as point scatterers. For sparse arrays, the point scatterer target model leads to grating lobes, and our central contribution is to demonstrate that a patch-based target model, suitably optimized for the sensor and scene geometry, suppresses such grating lobes. Key results include the following: (a) Characterizing the number of degrees of freedom (DoF) as a function of geometry, and showing that spatial undersampling (number of elements smaller than DoF) leads to grating lobes with the point target model; (b) showing that spatial aggregation via a patch-based dictionary suppresses grating lobes, and that patch size can be optimized based on estimation-theoretic criteria; (c) providing examples of the application, and adaptation, of patch-based dictionaries for sparse reconstruction.

Design and implementation of a high-frequency software-defined radar for coastal ocean applications

In 1955, Crombie [1] identified that when an electromagnetic wave is transmitted from a shore-based high-frequency (HF) radar, operating at 13.56 MHz, the Doppler spectrum of sea echo yielded a resonant backscatter phenomenon known as Bragg scattering, which results from coherent reflection of the transmitted energy by ocean surface waves (SWs) whose wavelength is exactly half as long as the transmitted radar waves. Around 17 y later, Barrick introduced the first- and second-order theory for deriving the HF ocean radar cross section, paving the way for using HF-SW radar (3–30 MHz) in remote sensing of the sea state [2]–[4]. Since then, design and implementation of classical HF radars have proliferated [5], with Coastal Ocean Dynamics Applications Radar and Wellen/Wave Radar (WERA) probably among the most popular [6], [7]. These radars use traditional, fixed, and dedicated hardware implementations. An outcome is that this approach limits the flexibility of these classical systems and potentially increases their cost.

Contribution of auxiliary coherent radar receiver to target's velocity estimation

Recent progress in bistatic radar techniques can be used to improve performances of classical monostatic radar. A prominent limitation of coherent radar is its inability to measure the complete velocity vector (magnitude and direction) of a detected target. A single coherent detection can provide range-rate only. At least two detections, separated in time, are needed to estimate the target's velocity vector. This study discusses how the velocity vector can be determined by two simultaneous detections spaced in distance. The second detection is obtained by an auxiliary distant bistatic coherent receiver; an approach proposed in the 1990s to enhance meteorological radar. Being a very simple case of a distributed radar system allows for a simple demonstration of how to calculate the target's position and velocity vector and how to analyse the estimation accuracy, including geometric dilution of precision plots of the velocity error. Also discussed are two methods to identify correct data association when more than one target is detected.

Experimental Study of the Hybrid Laser Radar

Objectives: The aim of this work was to perform experimental studies of hybrid laser radar as an intermediate option between the classical scanning pulsed laser radar and a system built in accordance with a 3D-Flash LADAR technology. Methods: The studies were performed on the ground optical track using modern equipment for the registration of measurement results. Modern methods of mathematical modeling were applied for data processing. Findings: Hybrid laser radar provided location frame frequency significantly greater than the frequency of the classical pulse radar, without the use of a matrix photodetector required for 3D-Flash LADAR. Frame frequency of 28 frames per second was obtained in the experimental settings with the view field of 20×20°. A signal/noise ratio was also determined imitating maximal operating range of 2 km on the ground track or of 5 km in space. Improvements: Hybrid laser radar can be used in robotic systems as a 3D technical vision system.

Influence of atmosphere attenuation on quantum interferometric radar

There has been aroused much interest in quantum metrology such as quantum radar, due to its applications in sub-Raleigh ranging and remote sensing. For quantum radar, the atmospheric absorption and diffraction rapidly degrade any actively transmitted quantum states of light, such as N00N and MM' states. Thus for the high-loss condition, the optimal strategy is to transmit coherent state of light, which can only provide sensitivity at the shot-noise limit but suffer no worse loss than the linear Beer's law for classical radar attenuation. In this paper, the target detection theory of quantum interferometric radar in the presence of photon loss is thoroughly investigated with the model of Mach-Zehnder interferometer, and the dynamic evolution of the quantum light field in the detecting process is also investigated. We utilize the parity operator to detect the return signal of quantum interferometric radar with coherent-state source. Then we compare the detection result of quantum radar with that of classical radar, which proves that the quantum radar scheme that employs coherent radiation sources and parity operator detection can provide an N-fold super-resolution, which is much below the Rayleigh diffraction limit; besides, the sensitivity of this scheme can also achieve the shot-noise-limit. Also, we analyze the effect of atmospheric attenuation on the performance of quantum radar, and find that the sensitivity is seriously influenced by atmospheric attenuation:only when the reference beam and the detection beam have the same transmissivity, will the sensitivity increase monotonically with increasing the photon number per pulse N, otherwise it first increases and then decreases with increasing N. Further, the sensivity is directly proportional to 1/N for the first case. In conclusion, we investigate the effects of atmospheric absorption on the resolution and sensitivity of quantum radar, and find that one can overcome the harmful effects of atmospheric attenuation by adjusting the transmissivity of reference beam to the atmospheric transmittance.

Application of Neural Network Enhanced Ground-Penetrating Radar to Localization of Burial Sites

The problem of searching for burial sites is an important issue for criminology, history, and archeology. The presently employed classical ground-penetrating radar (GPR) methods often yield equivocal results. Here, we report the results of our experimental study on the possible enhancement of the GPR methodology by introduction of the neural network to help localize the places of deposition of cadavers. The experiments, employing pig bodies as a model, yielded very promising results, but also indicated the problems that must be taken into account in further development of the methodology. Such problems include the influence of several circumstances on GPR signal and its computer-aided interpretation. Particularly important are: 1) the progressive decomposition of the body; 2) the dressing on the body—none, summer or winter garment, or wrapped in shroud or plastic foil; and 3) the size of the body. Based on the positive results of the preliminary survey the problems will be investigated using the prepared beforehand area with four burial sites and developed method for neural networks.

Analysis of classical incoherent integrator radar detectors in compound Gaussian clutter

The classical incoherent integrator is an important detection scheme in radar signal processing, owing to its simplicity and ease of implementation. In the context of compound Gaussian clutter, a new expression for the probability of detection is derived. This is applied to analyse the detector's performance in Pareto intensity clutter.

High resolution time of arrival estimation for a cooperative sensor system

Abstract. Distance resolution of cooperative sensors is limited by the signal bandwidth. For the transmission mainly lower frequency bands are used which are more narrowband than classical radar frequencies. To compensate this resolution problem the combination of a pseudo-noise coded pulse compression system with superresolution time of arrival estimation is proposed. Coded pulsecompression allows secure and fast distance measurement in multi-user scenarios which can easily be adapted for data transmission purposes (Morhart and Biebl, 2009). Due to the lack of available signal bandwidth the measurement accuracy degrades especially in multipath scenarios. Superresolution time of arrival algorithms can improve this behaviour by estimating the channel impulse response out of a band-limited channel view. For the given test system the implementation of a MUSIC algorithm permitted a two times better distance resolution as the standard pulse compression.

High-Resolution Radar via Compressed Sensing

A stylized compressed sensing radar is proposed in which the time-frequency plane is discretized into an N times N grid. Assuming the number of targets K is small (i.e., K Lt N <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ), then we can transmit a sufficiently ldquoincoherentrdquo pulse and employ the techniques of compressed sensing to reconstruct the target scene. A theoretical upper bound on the sparsity K is presented. Numerical simulations verify that even better performance can be achieved in practice. This novel-compressed sensing approach offers great potential for better resolution over classical radar.

Statistical Detection of Anomalous Propagation in Radar Reflectivity Patterns

Abstract The problem of anomalous propagation (AP) echoes in weather radar observations has become especially important now that rainfall data from fully automatic radar systems are sometimes applied in operational hydrology. Reliable automatic detection and suppression of AP echoes is one of the crucial problems in this area. This study presents characteristics of AP patterns and the initial results of applying a statistical pattern classification method for recognition and rejection of such echoes. A classical radar (MRL-5) station operates in central Poland performing volume scanning every 10 min. Two months of hourly data (June and September of 1991) were chosen to create learning and verification samples for the AP detection algorithm. Each observation was thoroughly analyzed by an experienced radar meteorologist. The features taken into account were visually estimated local texture and overall morphology of echo pattern, vertical echo structure, time evolution (using animation), and the general syno...

Multifunction rotating electronically scanned radar (RESR) for air surveillance

The system technical features of a new class of multifunction rotating electronically scanned radar systems (RESRSs), that electronically scan in both azimuth and elevation while rotating in azimuth, are described in terms of satisfying modern air defense needs. A brief comparison to classical radar solutions is followed by use of an illustrative example to indicate quantitatively as well as qualitatively the advantages inherent in an RESRS design. The concluding portion of the paper contains descriptions and photographs of a modern class of recently fielded RESRSs for tactical air surveillance.

Recognition of isotropic plane target from RCS diagram

The use of electromagnetic waves for the recognition of a structure represented by point scatterers is a fundamental problem. Much research is done on this subject, and the study of aircraft observed in the yaw plane gives interesting results. But to apply these methods it is necessary to use many sophisticated acquisition systems. In the letter, we give a new method which can be applied for plane structures composed of isotropic scatterers. This method is quite interesting because it uses power measurements only and necessitates only a classical tracking radar.