Radar: the evolution since World War II

Modern radar design has benefited from the evolution of specialized digital processing, allowing high resolution ground mapping, target identification, and target tracking under many conditions. Air-to-air interception makes use of complex decision processes to select from many modes that depend on the clutter backgrounds and flight profiles. Today's multimode radars provide this information for each task while minimizing distractions. Fire control radars support a wide selection of weapons, including cannons and guided missiles. This is possible because of advanced digital processing. In the interval since WW II, radar design evolved from vacuum tubes to semiconductors and then to massively integrated circuits. Computers specialized for fast Fourier transforms (FFTs) have revolutionized radar data processing. System reliability has improved from a few hours to hundreds of hours. Effective built-in test informs ground maintenance personnel of problems for easy maintenance and low failure rates reduce or eliminate field maintenance benches at forward locations. Airborne surveillance radars, such as AW ACS Joint Stars have changed the nature of warfare. Commanders have virtually full view of enemy and friendly forces. Radars, in combination with other remote sensors, provide precise weapon delivery, reducing collateral damage and making all weapons more effective     

Walker Model for Radar Sensing of Rigid Target Fields

The objective of this primarily tutorial item is to describe a general model for the observable data and the appropriate data processing involved in sensing rigid target fields with coherent radars. Any number of radars may be involved, and the scene and each radar may be in any kind of motion-with no restrictions on motion through resolution cells during the coherent processing time of the radars. The motions are assumed to be known. To some extent motion parameters can be estimated from the radar data, e.g., by adaptive parameter adjustments in the data processing; however, this subject is beyond the scope of this discussion. In large measure, the analysis in this item highlights the central conceptual result obtained by J.L. Walker as described in [1] -a major work in radar theory.     

Wind Farm Clutter Mitigation in Air Surveillance Radar

Windmills provide a renewable energy resource that could become major components of the power infrastructure in the United States, Europe, and Asia within the next decade. However, collections of windmills, known as wind farms, cause interference in radars that are critical to air defense and air traffic systems. Therefore, to maintain and, perhaps, improve air surveillance, methods that mitigate the inevitable performance degradation seen in radar systems must be proven and implemented to deal with wind farms as they become more prevalent. Herein, the authors discuss recommended techniques for wind farm mitigation, which are based on a UK Royal Air Force-sponsored demonstration on a Watchman radar, conducted at Clatter, South Wales. Specifically, false alarm and false track reductions will be quantified.     

Bayesian and Dempster-Shafer target identification for radarsurveillance

This paper considers the problem of target track identification in a radar surveillance system. To build a target identifier alongside a tracker, four features which are available for real-time processing in an air surveillance system are used here: target identity (TID) from a friend-and-foe identification (IFF) system, elevation measurement from the radar, target speed, and acceleration estimated by a tracker. These four features are combined to classify air targets into five different air target categories: friendly commercial, friendly military, hostile commercial (or unknown airline), hostile military, and false targets (clutter). Two popular statistic-based techniques, namely, the Bayesian and Dempster-Shafer methods, are applied to develop radar target identification algorithms for our application. Real-life as well as simulated air surveillance radar data are used to evaluate the practicality and effectiveness of this track identification approach in a radar surveillance system     

History of automotive anticollision radars and final experimentalresults of a MM-Wave car radar developed by the Technical University ofMunich

The history of development of automotive radars in different countries since 1972 is described using a short comparison of radar types. The authors indicate the planning of introduction of car radars in the near future according to information supplied by car companies. The purpose of the development of an automotive radar was to test different signal processing procedures both for distance and Doppler evaluation and also for a digital wavefront reconstruction to find out the angle position of a target. The block diagram, the main properties, the technical data of the radar system, the used antennas and the multiplexing of transmitting antennas is described. Finally some experimental results have been obtained under real traffic conditions     

Polish radar technology

Polish radar research and development since 1953 is reviewed, covering the development and production of surveillance radars, height finders, tracking radars, air traffic control (ATC) radars and systems, and marine and Doppler radars. Some current work, including an L-band ATC radar for enroute control, a weather channel for primary surveillance radar, signal detection in non-Gaussian clutter, adaptive MTI filters and postdetection filtering, and a basic approach to radar polarimetry, is examined.<>     

Monopulse Radars Excited by Gaussian Signals

This paper presents the theoretical probability densities of the outputs of both an amplitude-comparison monopulse radar and a phase-comparison monopulse radar when the monopulse radars are excited by Gaussian signals plus Gaussian noises. These probability densities are useful for studying the responses of monopulse radars to noise excitations. For example: Noise excitations arise when the monopulse radars are ?viewing? a noise source or a radar target consisting of randomly moving scatterers. The probability densities also serve as useful approximations for characterizing the outputs of monopulse radars when sinusoidal signals plus Gaussian noises excite the monopulse radars. Some special cases of the probability densities are presented in graphs.     

Radar target classification using doppler signatures of human locomotion models

The problem of target classification for ground surveillance Doppler radars is addressed. Two sources of knowledge are presented and incorporated within the classification algorithms: 1) statistical knowledge on radar target echo features, and 2) physical knowledge, represented via the locomotion models for different targets. The statistical knowledge is represented by distribution models whose parameters are estimated using a collected database. The physical knowledge is represented by target locomotion and radar measurements models. Various concepts to incorporate these sources of knowledge are presented. These concepts are tested using real data of radar echo records, which include three target classes: one person, two persons and vehicle. A combined approach, which implements both statistical and physical prior knowledge provides the best classification performance, and it achieves a classification rate of 99% in the three-class problem in high signal-to-noise conditions.     

FIREFINDER: Position Analysis System Advanced Development Model

The FIREFINDER Position Analysis System, FFPAS, provides FIREFINDER siting and operating personnel with a powerful tool. By automating the site selection and radar set-up processes, the FFPAS will significantly reduce the time and effort required to deploy FIREFINDER radars. Also, many radar effects that are difficult to include when calculations are performed manually, such as blind ranges and Doppler frequencies, variations in the target's radar cross sectional area (RCS), and the strength of the clutter return along a trajectory, can now be included in the radar siting and operational analyses. These capabilities will help the Army's FIREFINDER radars perform with maximum effectiveness on the modern battlefield     

Medium PRF Performance Analysis

A discussion of various types of x-band airborne radars is presented together with their systematic development through the years to the present time. Starting with simple, low pulse-repetition frequency (PRF) radars for measuring radar-target range, airborne radar development proceeded with more sophisticated high PRF Doppler radars where radar-target range and range rate were measured simultaneously. The use of Doppler (frequency) in signal processing allowed the separation of moving from nonmoving targets (ground), enabling the detection of moving targets in the presence of ground clutter. More recent developments in waveform generation and selection has resulted in the development of medium PRF radars, whereby a greater degree of tactical flexibility in target detection is achieved by combining the desirable features of both low and high PRF radars. Part of the available literature gives an overview, together with a specific example of the design and performance of an airborne medium PRF radar. Here, however, the systematic evolution of these radars is emphasized and the necessary theoretical background is developed for their performance calculations. Modern day airborne radars may be equipped with all three modes of operation, low, medium, and high PRF, allowing the operator to utilize the mode best suited for the tactical encounter. Low PRF and high PRF radars have been described elsewhere and are given here primarily for the sake of completeness and for the necessary background for developing medium PRF radar equations. They are also needed for developing the reasons why medium PRF radars came into being.     

国外机载海面监视雷达发展现状与趋势

首先对目前西方国家装备的较先进的机载海面监视雷达进行了介绍,总结了它们的技术特点。现役机载海面监视雷达具有多功能和多工作模式的特点,除增强了对高海况下的小目标检测能力外,还新增了气象探测、SAR/ISAR和HRRP等先进功能。最后指出了机载海面监视雷达未来发展趋势。     

Tracking Accuracies with Position and Rate Measurements

Tracking accuracies for the radial component of motion are computed for a track-while-scan radar system which obtains position and rate data during the dwell time on a target These results will be of interest to persons developing trackers for pulse Doppler surveillance radars. The normalized accuracies, computed for a two state Kalman tracking filter with white noise maneuver capability, are shown to depend upon two parameters, r = 4?0/?aT2 and s = ?dT/?0. The symbols ?0 and ?d are the position and rate measurement accuracies, respectively, ?a is the standard deviation of the white noise maneuver process and T is the antenna scan time. The scalar tracking filter equations are derived and numerical results are presented. Lower steady state tracking errors plus the earlier attainment of steady state accuracies are the direct consequence of incorporating the rate measurements into the tracking filter.     

Correlation Function for a 1/f Spectrum

The performance of ground surveillance radars depends on the spatial correlation, or spectrum, of the radar returns. Many radar terrain images are suspected to have a I/f spatial spectrum. This spectrum is thought to be difficult to handle mathematically in modeling and analysis because of its singularity at zero frequency and its infinite energy. A two-dimensional, band-limited I/f spectrum has neither of these problems: this is convenient for modeling and analysis in any practical system because the sensor measuring of an image always introduces band limiting, even if the natural phenomena are not band limited. Also shows the presence of terrain with a 1/f spectrum will not be readily apparent from the correlation function of the terrain image because the shape of the correlation function is largely determined by the sensor band limit and not by the underlying spectrum.     

Precision large scale air traffic surveillance using IMM/assignmentestimators

We present the development and implementation of a multisensor-multitarget tracking algorithm for large scale air traffic surveillance based on interacting multiple model (IMM) state estimation combined with a 2-dimensional assignment for data association. The algorithm can be used to track a large number of targets from measurements obtained with a large number of radars. The use of the algorithm is illustrated on measurements obtained from 5 FAA radars, which are asynchronous, heterogeneous, and geographically distributed over a large area. Both secondary radar data (beacon returns from cooperative targets) as well as primary radar data (skin returns from noncooperative targets) are used. The target IDs from the beacon returns are not used in the data association. The surveillance region includes about 800 targets that exhibit different types of motion. The performance of an IMM estimator with linear motion models is compared with that of the Kalman filter (KF). A number of performance measures that can be used on real data without knowledge of the ground truth are presented for this purpose. It is shown that the IMM estimator performs better than the KF. The advantage of fusing multisensor data is quantified. It is also shown that the computational requirements in the multisensor case are lower than in single sensor case, Finally, an IMM estimator with a nonlinear motion model (coordinated turn) is shown to further improve the performance during the maneuvering periods over the IMM with linear models     

Automated Tracking for Aircraft Surveillance Radar Systems

An improved moving target detector (MTD) (a digital signal processor) has been designed, constructed, and tested which successfully rejects all forms of radar clutter while providing reliable detection of all aircraft within the coverage of the radar. The MTD is being tested on both terminal and enroute surveillance radars for the FAA. This processor has been integrated with automatic tracking algorithms to give complete rejection of ground clutter, heavy precipitation, and angels (birds).     

Radar in the Soviet Union and Russia: a brief historical outline

This paper outlines the historical development of radar in the Soviet Union and Russia. Emphasis was given to only two classes of radars: surveillance radars for air defense (AD) systems; and radars for surface-to-air missile (SAM) systems.     

基于傅里叶变换的航迹对准关联算法

研究了在组网雷达存在系统误差情况下的目标航迹关联问题,理论分析了雷达系统误差对目标航迹的影响,并将该影响表示为目标航迹的旋转和平移量。在此基础上,提出了一种基于傅里叶变换的系统误差配准前航迹对准关联算法,该算法将组网雷达的航迹数据看做为一种整体信息,采用傅里叶变换理论来估计和补偿组网雷达目标航迹数据到融合中心航迹数据的相对旋转量和平移量,将雷达网中雷达上报的目标航迹数据对准到融合中心,从而不依赖于估计雷达网系统误差,实现了误差配准前的航迹准确关联,能够为后端的系统误差配准提供可靠的关联目标航迹数据。     

Multifrequency Imaging of Radar Turntable Data

In recent years synthetic-aperture radars (SAR) have proven to be very useful two-dimensional imaging tools in various fields. Based on the synthetic-aperture concepts, different imaging modes are possibe with various operating characteristics. We describe a special case where circular-projection radar data are coherently processed to yield both azimuth and range resoultion. Experiments are performed using data obtained from the radar target scatter site (RAT SCAT) radar cross-section facility. Fairly good results are obtained which illustrate the versatility of coherent syntheticaperture processing of pulse-to-pulse high-range-resolution radar returns. A discrete multifrequency stepped and pulsed waveform is the basic transmitted signal from which range-Doppler images are generated. The RAT SCAT turntable facility allows interesting model targets to be illuminated from which radar images can then be computed. One such application of the processing is described.     

Reacting to new air defence threats: a netcentric approach to the Hungarian air defence system augmented by VHF radars

Different types of distributed radar systems and data fusion centers are increasingly used by surface-based air defense systems. Besides the well-established airborne threats, new platforms for air surveillance and attacking devices have appeared and recognized air picture (RAP) production needs to be revised and modified following the events of September 11, 2001. From a military operational and logistic support point of view, it is well-known that not only the long range radars currently in operation, but also the recently procured radars, degrade in performance rapidly and their maintenance costs are high. Using the possibilities offered by emerging technical developments, the problem is to upgrade sensors and existing infrastructure in a way that exploits the information gathered optimally. It is the opinion of this author that one of the most promising approaches to emphasis net-centricity is the use of radar-triangle netcentric structures augmented by netted VHF radars to solve these tasks in a cost-effective manner. This work introduces an analysis of a solution that fully integrates newly required capabilities into the current long range radar net and infrastructure, keeping research and development (R&D) and maintenance at a low cost.