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This paper proposes a simple model for simulating quasi-coherent electronic countermeasures using multiple self-protection jammers. By studying the effects of time-difference of arrival between multiple signals at the radar receiverpsilas matched filter output, the probability of coherence is defined for determining probability of survival in mission planning. A theoretical derivation for probability of coherence between jamming pulse signals is postulated and the theoretical data is compared with empirical data extracted from flight simulation. The method is applied to a study of various tactical flight formations with respect to the victim radar. The proposed method allows one to determine probability of survival for the multiple jamming case by simply scaling established probabilities for the single-ship jamming case.

MTI radar systems and signal processing algorithms may be made more efficient if a wide range of perfect and background distorted Doppler signatures could be made available to test system hardware and algorithms. This paper addresses emulators of moving vehicle Doppler signatures. Measured Doppler spectra of tracked and wheeled vehicles are used to guide the development of moving target emulators made from ldquoswitchablerdquo reflectivity panels\. The geometry of the panels are electrically percolating surfaces The percolating patterns provide 10:1 bandwidths and thus satisfy UWB criteria for frequency response and they use minimal modulating elements. A potential problem is the number of modulating elements on a panel that are required to synthesize the complex Doppler waveform measured on a ground vehicle.

This paper develops the theory of both optimum and adaptive MIMO radar. It is shown that the optimum MIMO transmit-receiver pair consists of a coupled multidimensional eigensystem and whitening matched filter. Also introduced, is an design procedure for the clutter dominant case. After illustrating theoretical performance gains relative to conventional radar, we address the practical problem of adapting the transmit-receiver pair on-the-fly when the optimization must address multiple possible targets and/or signal (input) dependent noise (e.g., clutter). The resulting architecture combines the orthogonal transmit waveform MIMO radar with the aforementioned coupled transmit-receiver design pair with adaptive estimates for the radar channel.

A new method for interference mitigation which efficiently combines continuous-wave (CW) external-noise mitigation with transient and impulsive-noise mitigation in high-frequency over-the-horizon (HF OTH) radars is proposed in this paper. The efficiency of the method is demonstrated on real data collected by the JORN and SECAR HF OTH radars.

Cooperative coherent systems are well-known in radar and countermeasures communities where the transmitter and receiver antennas are co-located on the same platform; hence, the radio frequency (RF) sources are synchronized and the physical separation of coherent systems is limited or confined within the same platform. To improve the effectiveness of cooperative countermeasure systems, it is highly desired to significantly increase the physical separation between cooperative elements. In this paper, we study a non-coherent cooperative RF system where the cooperative elements are located on two separate platforms without hard-line connections to them. Hence, the cooperative signal exchange among multiple cooperative elements has to be transmitted via an RF link and the non-coherent cooperative system would allow the RF source to be located on a separate platform, thus increasing the physical separation. The two cooperative elements are operated with two separate local oscillators, which leads to large non-coherency between multiple platforms.

It has been remarked that interest in the subject of bistatic radar has varied cyclically, with a period of about fifteen years. The very first radars were bistatic, until T/R switches were invented. Interest was revived in the 1950s/1960s, with semi-active homing missiles and the SPASUR system, then died away. The second resurgence was in the mid-1970s to mid-1980s, with systems such as SANCTUARY and the first experiments in Passive Bistatic Radar. And the third resurgence started in the mid-1990s, and is still continuing. There are good reasons to believe that this time it is for real. The consequences of Moore’s law mean that digital processing power, which is essential to realise practical systems, increases inexorably. The advent of GPS solves many of the problems of timing and synchronization which were previously very difficult. Bistatic systems may be able to address new military and security operational requirements such as the detection and tracking of low-signature targets, and the increasing use of unmanned air vehicle (UAV) platforms is also well-suited to bistatic and multistatic configurations. There has been particular interest in bistatic radar exploiting broadcast, communications or radionavigation signals as illuminators - so-called passive bistatic radar (PBR).

Multicarrier Phase Coded signals have been recently introduced to achieve high range resolution in radar systems. As in single carrier phase coded radars, the conventional method for compression of these signals is based on using matched filter or indirect computation of an autocorrelation function. In this paper we propose a new method based on Fast Fourier Transform (FFT) that has lower computational complexity compared to the traditional approach. It has been approved that the proposed method is mathematically equivalent to matched filtering, so there is no processing loss. This approach can also be used to estimate the channel characteristics at any subcarrier frequencies.

Smart and powerful radar sensors for automotive applications require extremely high performance figures in measurement accuracy and resolution. A real technical challenge in this case is the simultaneous range, azimuth angle and velocity measurement, even in multiple target situations. These general requirements reflect especially the waveform design and azimuth measurement technique. Powerful automotive radar systems are currently under development or in a research stage for various applications, like Adaptive Cruise Control (ACC) that are already introduced into the market (e.g. Mercedes S class, Volkswagen Phaeton or Audi A8), stop-and go, driver assistance and even pre-crash systems. Linear frequency modulated continuous wave (LFMCW) radar sensors have the advantages of high resolution features in range and radial velocity but need a long measurement time. Therefore, some new intertwined waveforms, like FSK or combinations between FSK and FMCW will be discussed in detail to demonstrate the technical differences and advantages.

The progress of the late time response (LTR) method applied to the detection and identification of body-worn hidden weapons has been discussed in [1] and [2]. Efficiency of the target signature extraction and its correct interpretation depend on the system subcomponent characteristics as well as the processing algorithms used. Peculiarities in frequency domain (FD) measurements based on a stepped frequency radar technique introduce an ambiguity in the received signal interpretation. In this paper the real time domain (TD) experimentation system and new instant signal calibration procedure are described. Measurements were made in an anechoic chamber to provide complete signal control. Signal processing is based on adaptive filtering algorithms to provide equalization by a reference channel in order to remove any radio frequency (RF) system distortion of the received signal. A generalized matrix pencil-of-function (MPoF) approach is then applied to retrieve the parameters of LTR.

Multiple-Input, Multiple-Output (MIMO) radars enhance performance by transmitting and receiving coded waveforms from multiple locations. To date, the theoretical literature on MIMO radar has focused largely on the use of ldquoorthogonal waveforms.rdquo Practical approaches to approximate orthogonality (e.g., via waveforms characterized by low cross-correlation and low autocorrelation sidelobe levels) have also started to emerge. We show, however, that such waveforms can still perform poorly in adaptive systems. For adaptive MIMO radar systems, another factor is equally important; we call it ldquoMIMO Cancellation Ratio (CR).rdquo In this paper, we introduce MIMO CR and assess the performance of standard waveform classes (e.g., CDMA, TDMA and FDMA) with regard to this new metric. Then, we describe how to create new waveforms that facilitate higher performance adaptive cancellation. Finally, we apply our waveform design methodology to the problem of airborne MTI radar, in which STAP techniques are used to mitigate clutter.

Traditional radar systems rely on a predefined suite of waveforms and post-measurement signal processing to achieve such goals as target detection, classification, and tracking. Cognitive radar (CR) is a newly proposed framework in which the radar actively interrogates the propagation channel and adapts its operating parameters in order to maximize performance. We apply CR to a target classification problem by calculating custom waveforms that maximize the information received from the target echoes. A new MIMO waveform is proposed which maximizes the mutual information between a Gaussian random target and the received data under AWGN. The results indicate that the new frequency-domain formulation offers superior performance compared to both a non-adaptive approach and an ad hoc application of spectral waterfilling to the MIMO setting.

A scalable multifunction RF (SMRF) system allows the RF functionality (radar, electronic warfare and communications) to be easily extended and the RF performance to be scaled to the requirements of different missions and platforms. This paper presents the results of a trade-off study with respect to the combination or separation of the transmit and receive arrays of an active electronically scanned array (AESA) antenna as part of an SMRF system. The conclusion of a trade-off analysis is that the decision to separate or combine the transmit and receive function in a single antenna depends on the RF functions that are going to be combined. If only radar functions such as surveillance and target tracking are to be combined, there is a preference for combined transmit/receive antennas. If RF functions such as satellite communications and direction finding are to be combined with radar functions, there is an inclination towards separate transmit and receive antennas.

In modern surveillance radar, pulse compression is applied to achieve long range coverage while maintaining both low transmit peak power and desired range resolution. When there is a requirement to increase the radarpsilas range without a corresponding increase in the transmitted peak power it is required that a longer uncompressed pulse be used. As a consequence the blind range, associated with blanking the receiver whilst transmitting the pulse, will increase and short range coverage will be lost. In this paper we initially present a system of concatenated waveforms that provide simultaneous radar coverage for both near and far ranges. The solution incorporates a combination of longer sub-pulses for far range and shorter sub-pulses for near range. Although the concatenated waveforms have a number of attractive attributes, they present a challenging problem in that different sub-pulses will reflect back from different ranges and be received at the same time. Therefore since each sub-pulse is not separable at the RF front end a more complex sensitivity time control (STC) is required. In the second part of this paper we analyze this phenomenon and propose a STC scheme to address the issue.

Modern radar systems often have the conflicting requirements of a large phased array antenna for increased power-aperture product and/or angular resolution versus wide instantaneous signal bandwidth for fine range resolution. Pulse-to-pulse diversity may also be desired as a countermeasure against coherent repeater jammers. Using the multicarrier nature of orthogonal frequency-division multiplexing to encode wide instantaneous bandwidth pulses we propose a novel digital phased array architecture which mitigates dispersion effects experienced when the array main beam is electronically steered off broadside. The result is the ability to transmit and receive wideband pseudo-random phase coded pulses with a phased array antenna. Simulation results are used to quantify the benefit of the architecture. An overview of digital orthogonal frequency-division multiplexing waveform generation is also provided.

This paper deals with the problem of analyzing the RADAR scattering from small constructive details on low RCS platforms. Starting from the ILDC formulations of gaps and cracks, as proposed by Shore-Yaghjian and other authors, we have generalized its applicability exploiting numerical results arising from 2D simulations. The procedure is simple and straightforward and allows the analysis of shapes whose analytical results are not available. Typical application examples are door enclosures, gaskets, or quasi planar geometries with discontinuities in electrical conductivity and so on. This process, useful in preliminary design phases, dramatically reduces the simulation times, therefore allowing to analyze a lot of different situations. Validations have been performed resorting to numerical simulations as well as measurement activities. Results are provided for some simple cases, describing the capabilities and limitations of the approach. Comparisons between simulated and measured results on proper mock-up will be shown in the Conference presentation.

Multi beam antenna arrays are extensively used for 3D surveillance radar, providing a shaped beam in elevation and multiple beams in receive. Semi active multibeam antenna system employs 18 TR modules in elevation, feeding 18 linear arrays. The TR modules feed the 18 linear arrays in uniform amplitude and with required phase distribution in elevation to form the shaped beam and also steers the stack of beams in elevation. The required coverage pattern in transmit is attained through the phase alone synthesis. As the number of TR modules is very low and there is no amplitude control using the TR modules in transmit, failure of one TRM will prove catastrophic as far as radar coverage is concerned. Using genetic algorithm, phase only synthesis is used to mitigate the failure of the TRM, by loading the new synthesized phase values using beam steering computer while the radar is in operation. This paper details how genetic algorithm has been effectively utilized to mitigate the TR module failure of electronically steered portable surveillance radar.

This paper deals with an orthogonal pulse compression code set design problem in multistatic radar systems. Multistatic radar systems can improve radar performance by using a set of orthogonal waveforms with the same operating frequency. We provide the signal model for multistatic radar system using a set of orthogonal pulse compression codes. Moreover, a novel algorithm is proposed to obtain the set of orthogonal pulse compression codes. This algorithm minimizes the sidelobe peak of sum of autocorrelation and crosscorrelation function while maintaining the orthogonality of each code. Some of the designed results are presented by evaluating the characteristics of autocorrelation and crosscorrelation functions. In addition, the waveform diversity system and non-waveform diversity system are compared in terms of the probability of detection performance.

Traditionally, moving target indication (MTI) modes tailored to wide-area surveillance (WAS) have employed waveforms with bandwidths matched to the range extent of targets of interest. Matching range resolution to expected vehicle lengths serves to minimize interfering clutter returns while preserving available target power, thereby maximizing target probability-of-detection. Recent advances in waveform generator technology and high-speed digital signal processors for matched filtering have encouraged radar designers to consider wideband waveforms for WAS MTI needs. While providing information for identification and imaging, wideband waveforms complicate the detection process, as an extended target will be over-resolved; that is, returns from a vehicle will be distributed over multiple, fine-resolution range bins. Algorithms for combining these signal contributions are required for detection and angle estimation. Given such algorithms, one wonders whether over-resolving targets leads to detection and angle estimation performance losses as compared to narrowband operation. In this paper we evaluate methods for collecting energy from an over-resolved target for detection and angle estimation processing. We bound the performance of these techniques on typical ground targets and show that the probability-of-detection and angle accuracy is improved through the use of wideband waveforms at high signal-to-noise levels.

In previous work, frequency diversity has been shown to be an effective means of exploiting distributed radar apertures. Frequency diversity allows for each transmission to be isolated and processed independently of other frequencies. This paper presents an efficient implementation of a frequency diverse distributed radars, based on orthogonal frequency division multiplexing (OFDM), a concept borrowed from wireless communications. OFDM allows for frequency diversity to be implemented using only a single modulator/demodulator with the transformation, using a fast Fourier transform (FFT) to move between time and frequency domains as required. The resulting system is significantly simpler, but, as we will show, OFDM places a stringent constraint on the allowed sampling rate.

Genetic algorithms have proven to be useful tools in optimizing complex problems with large solution spaces. Radar waveform selection is a challenging problem that may benefit from the use of genetic algorithms. Furthermore, advances in the areas of waveform diversity, multistatic radars and knowledge-aided radars are making waveform selection even more challenging. As a design tool we used genetic algorithms to perform waveform selection utilizing the autocorrelation and ambiguity functions in the fitness evaluation. Monostatic, bistatic and multistatic notional examples are presented and early results indicate that genetic algorithms can provide a useful and effective tool in waveform selection for a variety of radar configurations.

We analyze the performance of a recently described class of two-dimensional autoregressive parametric models for space-time adaptive processing (STAP) in airborne radars on the DARPA side-looking radar model known as KASSPER Dataset 1. We investigate the trade-offs between signal-to-interference-plus-noise ratio (SINR) degradation (with respect to the optimal clairvoyant receiver) due to the mismatch between the observed covariance matrix and its parametric model, and the degradation due to the limited training sample volume. The impact of ground-clutter inhomogeneity on parametric STAP performance is demonstrated, as well as the significant superiority of parametric STAP over the conventional loaded sample-matrix inversion (SMI) technique.

In this paper, space-time adaptive processing (STAP) for clutter rejection in airborne radar is considered using a uniform circular antenna array. Indeed, this technique is usually employed in case of a uniform linear antenna array while the advantages of a circular antenna were recently highlighted [2]. Our contribution is two fold. We first analyze the effects of a circular antenna on the clutter properties and we then propose the use of a range recursive sub-space-based STAP algorithm of linear complexity to mitigate the potential range dependency of the neighboring snapshots. Simulations exhibit the high performance of the proposed approach to track the range non stationarity implied by the geometry of the antenna array and by the configuration of the radar: we here investigate both side looking and non side looking configurations.

The electromagnetic spectrum traditionally used by radar systems is under pressure from the growing global need for wireless communications services. Additional factors, such as the technology shift towards high duty-cycle solid-state transmitters and phased arrays using uniformly illuminated transmit apertures, are making the radar-to-radar electromagnetic interference problem more important than ever before. Such high-level electromagnetic interference (EMI) to radar can result in degraded performance, and for modern high-performance pulse doppler radars the problem is aggravated by the need to use coherent dwells of many pulses for coherent suppression of strong clutter returns. Just a few high-level EMI returns can severely desensitize the radar across many range cells in the pulse repetition interval (PRI) and even result in complete loss of information due to receiver saturation effects. This paper will describe a simple doppler repair technique for effectively reconstructing lost data within a pulse doppler radar coherent dwell and thus preserve clutter suppression and sensitivity in a severe EMI environment.

Recent work on electronic countermeasure (ECM) technique generation employed genetic algorithm optimization methods to define simple range-gate pull-off waveforms against a generic range-tracking radar simulation. This automated approach has potential to greatly reduce technique development time which is traditionally prolonged by manual experimentation. However, it also inspires a more generalized approach to optimization with hardware-in-the-loop configurations. This work investigates and develops the underlying mathematical and empirical framework for using optimization algorithms for hardware-in-the-loop simulation and testing. Unlike other reported radar/ECM optimization simulations, this approach uses a cost function library and scoring definition to separate simulation from the optimization algorithm, and is easily adapted to hardware-in-the-loop testing. In addition, effects from electromagnetic scattering and radar receiver processing may be measured, removing the need for completely defined objective functions. Finally, this approach nicely generalizes to multiple simultaneous cost function optimization. The method is demonstrated using the wellknown range-gate pull-off technique, but is adaptable to other ECM techniques. Future efforts will investigate specific optimization algorithms for the multi-objective problem.

Compared to traditional phased-array radar, multiple-input multiple-output (MIMO) radar can offer better parameter identifiability and higher resolution, enable the direct applicability of adaptive techniques for effective interference and jamming suppression, and allow for much flexibility for transmit beampattern design and waveform optimization. Reaping the full benefit of the superior performance enabled by the MIMO radar requires a novel design of its receive filters to minimize the impact of scatterers in nearby range bins on the received signals from the range bin of interest (the so-called range compression problem). Recently, an instrumental variables (IV) approach to MIMO radar receive filter design was proposed and shown to outperform the conventional matched filter approach. In this paper, we will present a least squares (LS) based MIMO radar receiver design. We will compare the performances of the IV and LS approaches with that of the matched filter method under a variety of test conditions.

The radar controller is a crucial, often over-looked, component of a radar system; allowing the transmitter to operate within a safe range and providing the flexibility to generate a variety of complex pulse schemes. Additionally, the radar controller provides precision timing to gate the radar systempsilas receiver(s) at regions of interest. Specifications for the design were chosen to match or exceed requirements for the 430 MHz transmitter at the Arecibo Observatory. Robustness, flexibility, and ease of use were the primary factors concerning software design, and open-source tools were used to promote re-use, sharing, and cost minimization within the community. We report an overview of system development, capabilities, and future plans and uses for the instrument.

Millimeter-wave band is the general trend for new communication, tracking radar and automotive systems. The crowd of RF frequency bands, the compactness of higher frequency radiating systems and the commercial availability of MMW components drive even more communications, tracking radars and automotive systems toward millimeter-wave band. Moreover, the antenna technology evolves from mechanical to full electronic systems and then phased-arrays are more and more widely employed for tracking radars and automotive systems. According to the general cost reduction trend, this paper describes some configuration of MMW phased-array antenna and presents theoretical and experimental results of a first demonstrator of passive phased-array designed in the frame of a research program funded by the Italian Minister of University and Science Research.

In recent work we introduced the notion of diversity in distributed radar systems and we evaluated the diversity order of fully distributed networks. Our long-term goal is to analyze the trade-off between distributed detection and detection using co-located antennas. In this paper, we extend our earlier analysis and we evaluate the diversity of joint detection for symmetric noise-limited systems. The Neyman-Pearson (NP) statistic for joint detection is shown to follow a Gamma distribution. We prove that the diversity order of large networks is on the order of radicK, thus outperforming the logarithmic diversity order of fully distributed detection. We finally provide simulations validating our theoretical analysis.

Electronically steerable antennas are expensive, whilst mechanically scanned antennas are of complex construction and hence are prone to failure. Based on the leaky-wave frequency-scanning principle, the spinning grating antenna (SGA) provides beam steering without the need of hinges. Whilst pulsed or stepped frequency waveforms may be implemented with this antenna, a frequency modulated continuous wave (FMCW) waveform allows close range operation at high speed, the possibility of excellent range-resolution, and low-cost signal processing. However, to implement FMCW with the SGA, the inherent scan-angle variation with frequency must first be overcome. Following on from an effort to develop a highly accurate radar system employing closed-loop linearisation to achieve 4 GHz of bandwidth centred at 94 GHz, this paper focuses on simultaneously achieving high angular resolution over a 20 degree scan range with good results.

A solid-state transceiver module for use in millimeter waves has been developed using HEMT GaAs technology. This module shown to have good performances in order to be used in active missile seekers. Despite the very good performances achieved, we show that itpsilas possible to increase them using GaN devices. This technology allows the realisation of high power, high efficiency power amplifiers, very good switches and LNA. We show that taking in account the actual trend of GaN research, itpsilas possible to foreseen the development of a such device in two or three years.

It is natural to approach multi-channel SAR in terms of spatial diversity concepts developed for multiple-input-multiple-output (MIMO) communications and recent advances in MIMO radar. We introduce the MIMO SAR concept in this paper, and the goal here is to research the concept and potential design of a new SAR application based on MIMO theory and techniques. MIMO technology which were develop originally for wireless communication, can improve the data rate and/or the reliability of communications over fading channels using multiple transmit and receive antennae. The proposed MIMO SAR exploits the independence between signals at the array elements as same as MIMO communication. By spacing the antenna elements at the transmitter and at the receiver such that the MIMO SAR can handle target RCS fading, scintillations and glint by virtue of the incoherent processing gain due to the spatial diversity of target scatterers opening the way to a variety of new techniques that can improve SAR performance.

Bistatic passive radar based on opportunity illuminators such as FM radio, is a hotspot in the domain of radar. The direct/multi-path signals cancellation techniques(DSC) have been discussed by many scholars. These considered algorithms adopt a single-stage adaptive filter processor frame, have sufficient performance in the cancellation of the direct/multi-path interference signals from the selected transmitter. In practice, because of the complicated atmospheric propagation influence (as maritime evaporation ducts), or the active radio jamming, the single-stage DSC would be invalid. In this paper, we propose a two-stage canceller to suppress the direct interferences and the jamming of the unknown radio at the same frequency. Field experiments and simulations validate our proposition. After direct/multi-path signals being cancelled in the first stage, the second stage of the canceller can improve the jamming suppression above 20 dB.

For high-accuracy radar-based range measurement two commonly applied radar principles are frequency-modulated continuous-wave (FMCW) and pulse radars. In many applications, e.g. liquid level gauging or short-range automotive applications, the latter radar principle is based on sequential sampling together with a cross correlation technique to alleviate the high demands on the sampling stage as well as the high power consumption of a standard pulse radar. The systempsilas mode of operation is well-known. In this paper we present a detailed derivation and discussion of the resulting intermediate frequency (IF) signal model. Furthermore, a derivation and comparison of the best possible round-trip delay time (RTDT) respectively range estimation variances using FMCW, standard pulse, and the advanced pulse radar concept is given by means of the corresponding Cramer-Rao lower bounds (CRLBs). Asymptotically optimal and suboptimal estimators are derived and compared regarding their range estimation variance, threshold level, and computational complexity. Simulation and measurement results show the applicability of the derived bounds and estimators in practice.

In recent years phased arrays have seen breakthroughs that lead to capabilities not possible in the past. This is exemplified by the development of GaAs integrated microwave circuits called monolithic microwave integrated circuits (MMIC). This integration has reached the point where it is possible to now build a low cost 35 GHz phased array for a missile seeker costing $30/element (total cost of array including all electronics divided by number of elements). This is made possible here because integration allows the whole T/R module to be put on a single chip. For some application it will be possible in the near future to put multiple receivers or transmitters on a single chip now. The advances provided by Moorepsilas Law has now made it is feasible to do digital beam forming (DBF) with all its numerous advantages. It is now possible to do DBF for a 2,500 element array at the element level, a major breakthrough. Also covered will be: the potential for GaN and SiC chips which have the capability of a factor of ten or more higher peak power than GaAs chips; arrays with instantaneous bandwidths of up to 33:1; SiGe low cost T/R modules; low cost MEMS passive arrays; a real radar application for multiple-input multiple-output (MIMO) as opposed to fantasy has been demonstrated by Lincoln Lab MIT which allows coherent combining of two radars to achieve a 9 dB increase in sensitivity; MIMO also makes possible the optimum removal of clutter in OTH and airborne radars by permitting adaptive control of the transmit antenna pattern in the receiver.

Due to the complex nature of electronically steerable phased arrays, higher operating frequencies, increased density requirements, and wider operating temperatures, there has been increased focus on technology development with thinner microwave laminate substrates to create a multi-layer boards that are phase stable with temperature and compatible with embedded resistors utilized for Wilkinson Power Dividers. These laminates can range from 0.003" to 0.010" in thickness with frequencies well into the Ka Band. This paper explores technical advances and technical considerations placed on these materials as they are required for these advanced systems. This paper also discusses the processing limitations placed on existing materials and technical developments to overcome these deficiencies.

Conformal arrays possess certain desirable characteristics for deployment on unmanned aerial vehicles and other payload-limited platforms: aerodynamic design, minimal payload weight, increased field of view, and ease of integration with diverse sensor functions. However, the conformal arraypsilas nonplanar geometry causes high adaptive losses in conventional space-time adaptive processing (STAP) algorithms. In this paper, we develop a conformal array signal model and apply it to evaluate the performance of conventional STAP algorithms on simulated ground clutter data. We find that array-induced clutter nonstationarity leads to high adaptive losses, which greatly burden detection performance. To improve adaptive performance, we investigate the application deterministic and adaptive angle-Doppler warping techniques, which align nonstationary clutter returns. Through the application of these techniques, we are able to nearly fully mitigate the nonstationary behavior yielding performance similar to that of a conventional planar array.

This paper describes an approach to high range resolution (HRR) by means of stretch processing by digital deramping. This approach offers advantages that are common for stretch processing, as a moderate data rate for signal processing in the presence of a high bandwidth waveform. In contrast to conventional analogue processing, deramping is realized digitally. The approach of digital deramping offers the possibility to combine the deramp processing with digital down modulation. Moreover, the digital deramping allows to measure and calibrate distortions in the analogue radar front-end. A calibration scheme is presented that incorporates calibration corrections into the digital deramp signal. The calibration scheme is of particular interest for applications in active phased array radars with multiple receive channels. The presented approach offers a number of advantages compared to analogue stretch processing and other approaches to high range resolution.

In the past decade many countries have launched programs to deploy wind turbines as alternative sources of electrical energy. When deployed in wind farms this technology has raised concerns from both air traffic control (ATC) and military authorities. This is due to the fact that the turbine blades return radar echoes that have the potential to distract and confuse the air traffic picture by creating false detections that can effectively mask genuine aircraft returns. Most of the mitigation solutions offered today are either primarily based on such measures as range-azimuth gating or inhibiting track initiation in the vicinity of wind farms. These draconian measures can result in a significant degradation in radar performance and potential air traffic control disruption. They may also require costly redesign of the existing radars. This paper presents a set of 'clean' solutions that mitigate, and in some cases completely eliminate the effect of wind turbine returns. The solution is based on the combination of discrimination techniques applied at the pre-detection, detection and post detection stages of the radar signal processing chain. The suit of mitigation solutions developed does not adversely affect aircraft detection, and can be readily retrofitted to the existing ATC primary surveillance radars (PSR).

In this paper we combine advanced STAP algorithms and concepts for adaptive guard channels with subarrayed planar arrays together with the theoretical results available in the field of adaptive detection (GLRT, AMF, ACE tests). The aim is to define a robust adaptive sidelobe blanking detector against combined impulse and CW interference as well as strong clutter discretes. For the selection of the thresholds, we utilize the detection margin introduced as a direction dependent tool, instead of the commonly used main and guard channel antenna patterns. Numerical results are then given for a generic airborne multifunction radar system.

Sidelobe blanking (SLB) devices are used within radar systems to reduce the number of false alarms due to impulsive interference incoming through the sidelobes. The aim of this paper is to study the effects of different jamming techniques on a phased array radar equipped with a SLB device. The entire system is modeled accounting for the mutual coupling among the antenna array elements, and two different configurations for the position of the SLB element are considered. The cases of co-polarized and cross-polarized jamming signals are investigated. The analysis is focused on both the jammer capability to produce false targets and on its ability to mask the useful echo.

Periodogram is a simple and efficient way to detect and estimate parameters of sinusoidal signals which is widely used in radar where we need to detect moving targets. In this paper, the detection performance of the periodogram and its variants such as Bartlett, Welch methods, and a proposed Bartlett-based method is evaluated. Performance evaluation through the receiver operating characteristics (ROCs) of the mentioned methods are presented and compared. Previous studies showed that, the standard periodogram used to give the best detection performance. In the present work, analytical derivation and simulation results showed that, the proposed method gives a better detection performance outperforming the standard periodogram at the expense of a tolerable reduction of the frequency resolution.

A method for utilizing wideband transmissions (>100 kHz) in OTHR is proposed. The technique involves the aggregation of multiple narrow band signals into a wideband composite through digital synthesis. The multi-channel signal is received digitally and after normal correlation and Doppler processing is recombined using Whitehead-Malekpsilas phase-frequency technique to provide an orthogonal micro-ranging dimension. The technique is described, and then modeled in an attempt to gauge its effectiveness. The demanding application of OTHR height finding is chosen in the modeling as it requires separation of ionospheric micro multi-path signals to be effective. The modeling shows that ionospheric dispersion limits a direct application of the micro-ranging technique when propagating through an IRI mid-latitude ionosphere with typical frequency selection rules. A simple method of estimating and removing the ionospheric dispersion is proposed and demonstrated to be effective in progressing the technique to provide range resolution approaching that expected with the wideband signal.

Frequency agility is an important feature when radar operates in jammed environments. With the development of the orthogonal frequency division multiplexing (OFDM) waveform in the communications, the opportunity for a new generation of digital agile radar rises. Old and expensive multi-channel analog agile front ends could be replaced by simpler and cost effective single channel transceivers where the coherent switches in frequency are done digitally. The novelty of the paper is to investigate an agile OFDM waveform so that Doppler can be solved despite the apparent frequency agility. The OFDM performance is assessed from the radar point of view, using the ambiguity function as a tool. Our approach considers a pulse burst, each pulse being implemented with OFDM chips. Three patterns for frequency agility from pulse-to-pulse are studied. Preliminary suggestions to accomplish coherent processing in an agile context are derived.

In this paper a doubly adaptive scheme is presented for detection and jammer cancellation by airborne monopulse radar, equipped with three receiving channels. An adaptive auxiliary selection technique is proposed to decide which is the most effective couple of auxiliary antennas in each condition, assuming a slowly changing jamming environment. This leads to a doubly adaptive jammer cancellation scheme: we first perform an adaptive selection of the best set of auxiliary beams, and then apply an adaptive scheme for jammer cancellation and target detection using only the best set of three receiving channels. This can be used also to obtain an adaptive ECCM as a retrofit on an existing 2D monopulse radar. This paper characterizes the performance of this approach, together with its limitations.

Orthogonal frequency division multiplexing (OFDM) radar signals, because of their prominent properties have been recently of interest of many researchers. But the large amplitude fluctuations of the OFDM signals makes it susceptible to system nonlinearities. This paper proposes a new concept of radar coding using OFDM signals which combines orthogonal frequency division multiplexing and phase modulation (OFDM-PM) or frequency modulation (OFDM-FM). The PM or FM creates a constant envelope signal which allows high power amplifiers to operate near saturation levels thus maximizing power efficiency and OFDM increases the robustness to multi-path fading and also range resolution capability. The feasibility of this signalling as a radar pulse compression technique is also studied, and some codes for constant envelope OFDM signals (CE-OFDM) with favourable autocorrelation functions are introduced.

In this paper we describe a joint waveform design methodology for distributed imaging RADARs using the concepts of compressive sensing. Compressive sensing is an active area of research that offers the promise of good object reconstruction with a sparse measurement set. The measurement set of the scene is based on a set of dasiaprobes,psila the radar waveforms. The set of measurements must satisfy the restricted isometry property and the scene being interrogated must be dasiacompressiblepsila meaning that it can be sparsely represented in some basis. We examine waveform and position considerations for a distributed radar system to satisfy these constraints and show their impact on waveform design and image reconstruction.

Future multi-mission / multi-mode sensors and radio frequency systems will have to operate in electromagnetically dense signal environments. Furthermore, a diverse cadre of concepts may result in a variety of fielded systems, all operating in close proximity to each other. While this ever growing collection of concepts bodes well for the rapid transition of new technology, these systems must share spectrum, measured data, and mission responsibility in order to perform in an economical and effective manor. Key to the successful fielding of these new sensors is knowledge based control of signal processing algorithms and radiated waveforms, as well as platform dynamics. In this tutorial, foundational technologies and their functional relationships will be presented in order to illustrate performance improvements relative to classical approaches. Knowledge Based STAP, Expert Systems CFAR, RF Tomography and Sensors as Robots technologies are presented as offering a way forward from a radar perspective.