The phase coded FMCW and its properties for joint sensing and communication are studied. Two different receiver structures for the sensing properties of this waveform are compared theoretically and experimentally. It is shown both by simulations and experiments that the phased coded FMCW combines communication capabilities of PMCW and sensing capabilities of FMCW while using a realizable hardware complexity for an automotive radar.@en

In this paper, we propose a method for continuous monitoring of vital signs-in particular, respiration frequency-with a commercial mm-wave radar. The nearly constant frequency (NCF) model is adopted to represent chest displacement due to respiration and simulate radar response. Based on this model, an extended Kalman filter (EKF) based estimator is developed to track the breathing frequency of a person. The impact of dynamic model parameters is investigated in numerical simulation. The possibility to track breathing frequency with the proposed method is demonstrated by experimental data processing.

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This paper presents an analysis of a new method of automotive radar self-calibration which uses targets of opportunity. While conventional offline calibration of a phased array antenna requires accurate knowledge of the positions of calibration targets relative to the radar, such information is not available in a dynamic scenario. To compensate for this, we have developed an estimation procedure based on an extended Kalman filter (EKF) to address the challenge of simultaneous localisation, mapping and calibration. The proposed technique makes it possible to compensate for moderate errors of amplitude and phase in the phased array response with just a few measured frames. A significant reduction in the sidelobe rejection of the array response, plus the ability to correct for angular steering errors, are demonstrated via numerical simulations and real data processing.

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Adaptive detection of fast moving targets by means of high range resolution radar is considered. It is assumed that a fast-moving target of interest has a few range cells migration during the coherent processing interval and the clutter power fluctuates rapidly along the range. Therefore, the target competes with the clutter responses in a few adjacent range cells, modeled by Compound-Gaussian process. The adaptive CFAR detector of range-migrating targets is designed and it is complemented by the algorithm for covariance matrix estimation from the reference data. The generalized approach for detection of range-extended migrating targets is provided. The performance of the proposed detectors is evaluated via numerical simulations, showing valuable improvement over the conventional techniques.@en

Modern surveillance radars are designed to detect moving targets of interest in an adverse environment, which can encompass strong unwanted reflections from ground or sea surface, clouds, precipitation, etc. Detection of weak and small moving targets in environmental clutter remains, however, a challenging task for the existing radar systems. One of the main directions for modern radar performance improvement is the application of wideband high-resolution waveforms, which provide detailed range information of objects in the observed scene. Together with such inherent advantages of wideband waveforms as multi-path separation, clutter reduction and improved target classification, additional benefits can be obtained by exploiting target range migration (range walk), essential for fast moving targets in the high-resolution mode. This thesis aims at the development of novel signal processing techniques for migrating target detection in wideband radars. It involves both resolving range-velocity ambiguities and improvement in target discrimination from ground clutter by accounting for target range migration. It is demonstrated that wideband radars can resolve range-velocity ambiguity by transmitting a single long pulse burst with low pulse repetition frequency (PRF) and exploring target range walk phenomena during the burst. The ambiguity function of such waveform still has strong residuals at the locations of ambiguities, called ambiguous sidelobes, which have to be considered in the processing of wideband data. The presence of ground clutter in the observation scene has a detrimental effect on the wideband radar performance. The impact of the clutter Doppler spectrum and waveform parameters on target detection at clutter ambiguities has been investigated. The improvement over the conventional waveform is demonstrated for narrow clutter Doppler spectrum; in the presence of clutter with a wide Doppler spectrum, the conventional staggered-PRF waveform is preferable. Performance degradation at ambiguous-to-clutter velocities is validated on the real data sets. Modern high-resolution parametric-free spectrum estimators – IAA (Iterative Adaptive Approach) and SPICE (Semi-Parametric Iterative Covariance-based Estimator) – are proposed for the reconstruction of the observed scene from wideband radar measurements with no velocity ambiguities. These algorithms demonstrate significant improvement in rejection of ambiguous sidelobes over the conventional techniques. For clutter-limited case, the covariance-aware SPICE is introduced with improved capability to discriminate targets from clutter. The advantages of the proposed methods are demonstrated in numerical simulations and real data processing. The ambiguous sidelobes can cause severe problems for detection of multiple targets located at similar ranges. A dedicated detector for a dense target scenario has been introduced. It can detect multiple closely spaced targets and mitigate false detections due to their ambiguous sidelobes, holding false alarm probability at the required level. The improvement over conventional processing is demonstrated. Special attention is then devoted to clutter suppression in the high range resolution mode. In meter or sub-meter range resolution, the observed ground clutter, modeled by a compound-Gaussian process, may have significant fluctuations over the range interval, elapsed by the target. An advanced detector for range-migrating targets in compound-Gaussian clutter is developed. It performs two-dimensional clutter filtering – in Doppler frequency and in the range – and benefits from clutter spatial diversity, obtained for a target passing over different patches of clutter. A significant improvement in the detection of fast moving targets in spiky clutter is achieved in comparison to the existing methods. The attained gain depends on clutter characteristics and target velocity: fast moving targets are easier to detect than slow ones with equal signal-to-clutter ratio. The generalized approach for detection of range-extended migrating targets is provided. The performed research provides some fundamental insight for implementation of new radar architectures with the utilization of wideband waveforms. @en

When designing a new radar system, standard resolution trade-offs play a major role, providing the basic parameters of the radar, such as size, update rate, and range. Besides, diversity has long been used for mitigating fading effects due to the fluctuation of targets and clutter. However, with the arrival of more flexible systems, using multiple parallel channels on transmit and receive, and wider instantaneous bandwidths, these standard trade-offs are becoming less simple—and more flexible. In this communication, we will analyse the benefits of diversity and its relations with range, Doppler, and angle, for detection and location of moving targets with wideband/wide-beam radar systems. The idea is to contribute to a better understanding of the real benefits of agile transmissions for detection/localization of moving targets, focusing on range, velocity, and angular measurement improvements, as well as on the benefits for detection of moving targets. Special attention will be given to the quality of the different wideband wide-beam sensor modes for long-range surveillance, and new results on detection of moving targets in clutter will be provided to demonstrate the effectiveness of these new architectures for small target detection at long range, in difficult environments.
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Wideband radars have been proposed for detection of moving targets, with unique capability of non-ambiguous detection due to range migration. Moreover, frequency diversity has long been used for mitigating the fading effects caused by target and clutter fluctuations. The real benefits of wideband radars are difficult to analyze, since they derive from the combined effects of target resolution in range, migration over successive cells of clutter, Doppler resolution and instantaneous bandwidth, and residual ambiguities in Doppler. In order to contribute to a better understanding of the benefits of agile transmissions for detection of moving targets, clutter cancelling performances of wideband radars are examined, demonstrating clear benefits from diversity on clutter and target, primarily – but not only – obtained through target migration effects. Special attention is given to long-range surveillance and tracking, and new results on detection of moving targets in clutter will be provided to demonstrate the effectiveness of these new architectures for small targets detection at long range, in difficult environments. Finally, recommendations for system designs that improve the discrimination of moving targets against fixed and diffuse clutter are presented.@en

In this paper, the problem of on-the-fly estimation of the radar state (self-diagnostics) is considered. We propose to use repetitive objects of the road infrastructure, such as lampposts, for continuous diagnostics of the radar state. The selected approach allows accounting for the external factors, such as water layer or dirt on the bumper, which can significantly affect radar performance, but cannot be retrieved with the internal calibration. The statistical model for RCS of repetitive targets is considered, and the estimator of the actual radar gain from the received data is derived. It is demonstrated that observing a few tens of targets is sufficient to provide a reasonable estimation of the radar performance within the operational mode.

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This paper deals with the problem of coherent radar detection of fast moving targets in a high range resolution mode. In particular, we are focusing on the spiky clutter modeled as a compound Gaussian process with rapidly varying power along range. Additionally, a fast moving target of interest has a few range cells migration within the coherent processing interval. Two coherent CFAR detectors are proposed taking into account target migration and highly inhomogeneous clutter. Both detectors involve solution of a transcendental equation, carried out numerically in a few iterations. The performance evaluation is addressed by numerical simulations and it shows a significant improvement in detection of fast moving targets in inhomogeneous heavy tailed radar clutter.@en

To improve the efficiency of surveillance radars, we describe a method using a single train of wideband (≈10% relative bandwidth) coherent pulses, rather than a sequence of several trains of narrow-band pulses. In this technique, target velocity is measured by both pulse-topulse (ambiguous modulo 2π) phase rotation and target distance variation (distance migration) along the pulse train. The modeling of the targets and clutter are first described, then the limitations of the matched filter processing (existence of residual ambiguities in the form of secondary lobes) are highlighted. An iterative adaptive approach makes it possible to remedy these faults, in simulation as well as on real experimental signals. Adaptive clutter suppression techniques are then examined: the influence of the echo spectrum spread and the influence of the bandwidth parameter are analyzed in detail, and an adaptive detector is developed, combining the elimination of clutter and the detection decision. In conclusion, the operational benefits of this detection by a single train of wideband pulses, compared to the usual technique combining a sequence of narrow-band pulse trains, are summarized, both in terms of sensitivity gains and in terms of velocity resolution and target analysis capability.@en

The problem of range-migrating target detection in a compound-Gaussian clutter is studied here. We assume a target to have a range-walk of a few range cells during the coherent processing interval, when observed by wideband radar with high range resolution. Two CFAR detectors are proposed assuming different correlation properties of clutter over range. The detectors' performance is studied via numerical simulations and a significant improvement over existing techniques is demonstrated.@en

In this paper the influence of clutter power spectrum on unambiguous radar target detection with single low pulse repetition frequency wideband waveform is analyzed. Impact of both stationary and diffuse clutter components for different signal bandwidths and coherent processing intervals (CPI) is studied. Exponential model of the ground clutter power spectrum for the diffuse component is used. For the first time, radar detection performance for wideband signals at ambiguous to clutter velocities is predicted as function of bandwidth and CPI.@en

In this paper the problem of unambiguous moving target detection using wideband radar is considered. Doppler ambiguities, which are present in the low pulse repetition frequency mode, are transformed into ambiguous sidelobes of targets and clutter using range migration effect. However, the level of these sidelobes is typically high, such that standard detectors suffer from false alarms generated by the ambiguous sidelobes of real targets. To remove these false alarms two new detectors assuming Gaussian distribution of clutter and exploiting high resolution spectral estimation are developed. These detectors are based on spectral estimation obtained with non-parametric Iterative Adaptive Approach from spectrum analysis and satisfy bounded false alarm condition. Approach to reduce the number of reference cells for covariance matrix estimation is discussed. The benefits of the proposed detectors are demonstrated via numerical simulations showing improvement over existing algorithms.@en