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In this paper, a radar signal processing system, which combines pulse doppler mode and stepped frequency mode, is proposed. The pulse doppler mode is used to detect targets and measure their velocity accurately, and then the stepped frequency mode is used to image the targets. The signal processing system has been implemented on the domestic Huarui No. 2 digital signal processor.

Distance measurement tasks in micromachine tools need to be performed with micrometer accuracy. For such tasks, frequency-modulated continuous-wave (FMCW) radars with a combination of frequency and phase evaluations are a good choice. However, the accuracy cannot be indefinitely increased as there are constraints on the target size and placement imposed by the limited space inside micromachines. This paper investigates the influence of target geometry and position on the accuracy of its range estimation using a W-band FMCW radar with a bandwidth of 25 GHz. A relation between target geometry and accuracy is established through the Cramér-Rao lower bound (CRLB). Based on the measurements of different targets, an optimal shape and size is proposed, which provides an average accuracy in the single digit micrometer range. Furthermore, the influence of different bandwidths on the accuracy is investigated. It is also demonstrated how the CRLB can be used to optimize the size of a target, when a certain accuracy is needed. In addition, antenna field regions are analyzed for suitable target placements. Finally, the radar system is implemented in a machine tool and measurements with accuracies in the micrometer range are carried out.

This paper presents a high sampling frequency pulse-Doppler radar that was constructed using commercially available components. The system architecture is explained with emphasis placed on the digital transceiver subsystem. A calibration technique is presented to mitigate range ambiguity due to digital latency variation between resets of the system. The pulse-Doppler operation of the system is then evaluated through the range-Doppler mapping of moving and stationary targets, confirming the radar's potential for synthetic aperture radar imaging.

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.

[EN] Multiple-input multiple-output (MIMO) radars have been shown to improve target detection for surveillance applications thanks to their proven high-performance properties. In this paper, the design, implementation, and results of a complete 3-D imaging frequency-modulated continuous-wave MIMO radar demonstrator are presented. The radar sensor working frequency range spans between 16 and 17 GHz, and the proposed solution is based on a 24-transmitter and 24-receiver MIMO radar architecture, implemented by timedivision multiplexing of the transmit signals. A modular approach based on conventional low-cost printed circuit boards is used for the transmit and receive systems. Using digital beamforming algorithms and radar processing techniques on the received signals, a high-resolution 3-D sensing of the range, azimuth, and elevation can be calculated. With the current antenna configuration, an angular resolution of 2.9° can be reached. Furthermore, by taking advantage of the 1-GHz bandwidth of the system, a range resolution of 0.5 m is achieved. The radio-frequency front-end, digital system and radar signal processing units are here presented. The medium-range surveillance potential and the high-resolution capabilities of the MIMO radar are proved with results in the form of radar images captured from the field measurements.

The first- and second-order high-frequency radar cross sections of the ocean surface are derived for an antenna on a floating platform. In this analysis, simulations are conducted for a more complicated platform motion than appear in earlier work and comparisons are made to model outputs for a fixed antenna. Results show that motion-induced peaks appear symmetrically in the Doppler frequency and have less energy in the second-order radar cross section than those in the first-order radar cross section. The magnitude and width of the Bragg peaks are seen to decrease and broaden, respectively, as compared to the case for a fixed antenna. The platform motion modulates the radar signals as a frequency modulator, and the modulation indices are related to the amplitudes of the platform motion. With a larger amplitude of platform motion, more energy is transferred from the Bragg peaks to the motion-induced peaks, and more motion-induced peaks need to be considered.

A new 94-GHz frequency-modulated continuous wave (FMCW) Doppler radar–radiometer system [Jülich Observatory for Cloud Evolution (JOYCE) Radar–94 GHz (JOYRAD-94)] is presented that is suitable for long-term continuous observations of cloud and precipitation processes. New features of the system include an optimally beam-matched radar–radiometer; a vertical resolution of up to 5 m with sensitivities down to −62 dBZ at 100-m distance; adjustable measurement configurations within the vertical column to account for different observational requirements; an automatic regulation of the transmitter power to avoid receiver saturation; and a high-powered blowing system that prevents hydrometeors from adhering to the radome. JOYRAD-94 has been calibrated with an uncertainty of 0.5 dB that was assessed by observing a metal sphere in the radar’s far field and by comparing radar reflectivities to a collocated 35-GHz radar. The calibrations of the radar receiver and the radiometric receiver are performed via a two-point calibration with liquid nitrogen. The passive channel at 89 GHz is particularly useful for deriving an estimate of the liquid water path (LWP). The developed retrieval shows that the LWP can be retrieved with an RMS uncertainty (not including potential calibration offsets) of about ±15 g m−2 when constraining the integrated water vapor from an external source with an uncertainty of ±2 kg m−2. Finally, a dealiasing method [dual-radar dealiasing method (DRDM)] for FMCW Doppler spectra is introduced that combines measurements of two collocated radars with different measurement setups. The DRDM ensures high range resolution with a wide unambiguous Doppler velocity range.

A compact-array high-frequency surface wave radar equipped with two crossed-loop/monopole receiving antennas has been established for vessel detection. Using two compact antennas of the same design, this system can obtain two extremely similar sets of radar range-Doppler spectra over the same period. To detect vessel targets efficiently, the spectra of two antennas are enhanced by performing a principle component analysis. A wavelet-based approach is then applied to suppress clutter and reduce noise. The signal-to-noise ratios and signal-to-clutter ratios of the echoes are thus improved. Finally, an adaptive threshold is used to extract targets. The real radar data detection results are compared with Automatic Identification System data as well as those from the conventional ordered-statistic constant false alarm rate method. The feasibility and the validity of method proposed here are thus demonstrated.

In this paper, sea surface wind direction and speed are obtained from X-band nautical radar images. A data control strategy is proposed to distinguish rain-free and rain-contaminated radar data. The radar data are decomposed by an ensemble empirical mode decomposition method into several intrinsic mode functions (IMFs) and a residual. A normalization scheme is applied to the first IMF to obtain the amplitude modulation (AM) component. Wind direction is determined from the residual for the rain-free and high-wind-speed rain-contaminated data, and from the AM portion of the first IMF for the low-wind-speed rain-contaminated data, based on curve fitting a harmonic function. Wind speed is determined from a combination of the residual and the AM part of the first IMF for both rain-free and rain-contaminated data using a logarithmic relationship. Results employing ship-borne radar and anemometer data collected in a sea trial off the east coast of Canada are presented. The root-mean-square differences for wind direction and speed measurements are 11.5° and 1.31 m/s, respectively, compared with reference values from anemometers.

Ionospheric sounding is a technique that provides real-time data on high-frequency ionospheric-dependent radio propagation. This letter presents a Universal Software Radio Peripheral-based ionospheric sounding radar, which relies on a basic system consisting of a synchronized transmitter and receiver. The radar has the advantages of miniaturization, modularization, low power, and low cost. The three most significant features of the radar system are that it is software-defined and universal platform-based and that it has low transmitting power. This novel software-defined vertical-incidence radar system can probe the ionosphere and obtain real-time plasma parameters according to the simulation. Ionograms that directly express probe results are generated by MATLAB after data processing and simulation. Successful development of such an ionospheric sounding software radar will allow universalization and miniaturization of an ionosonde radar system. This letter introduces the implementation of the novel ionospheric sounding radar.

Systems based on (sub-)millimeter-wave technology demand compact transceivers to be commercialized. We have developed a compact front-end for a three-dimensional imaging homodyne radar at 300 GHz where a commercial subharmonic mixer acts both as a transmitter and as a receiver, due to the finite isolation between the local oscillator and radio frequency ports of the mixer. This allows the radar electronics compactness and a reduction in power consumption and cost without sacrificing imaging quality, which is the fundamental figure of merit for this application.

Small boat detection under the influence of sea clutter is usually difficult, especially for the low-resolution pulse Doppler Radar, as the amplitude of the boat is covered by sea clutter in the time domain, and the spectrum of the boat and sea clutter overlap in the frequency domain. This paper proposes a new method for the detection task based on time-frequency analysis and YOLO V3 network. This method can automatically extract the characteristics of sea clutter and boat in time-frequency images and complete the classification task. The accuracy of the classification is 94.89 percent, which has an improvement of 14.39% than the accuracy of LeNet-5. The measured data verified the method.

This paper presents a technological demonstrator with traffic applications, which carries out three typical intelligent transportation system (ITS) tasks: traffic flow measurement, speed estimation, and vehicles classification. The proposed system is a frequency-modulated continuous wave radar working at 24 GHz, with side-looking installation. Two signal-processing modes, 1-D and 2-D, are introduced as detection scheme. Unlike other existing commercial systems, this demonstrator makes use of phase information from target echoes in order to perform clutter cancellation and target speed measurement. To this end, two different speed-estimating methods are proposed and compared by means of experimental results obtained from a complex scenario.

This paper presents a novel, simple method to correct reflectivity measurements of weather radars that operate in attenuation-influenced frequency bands using observations from less attenuated radar systems. In recent years radar systems operating in the X-band frequency range have been developed to provide precipitation fields for areas of special interest in high temporal (≤1 min) and spatial (≤250 m) resolution in complement to nationwide radar networks. However, X-band radars are highly influenced by attenuation. C- and S-band radars typically have coarser resolution (250 m–1 km and 5 min) but are less affected by attenuation.Correcting for attenuation effects in simple (non-Doppler) single-polarized X-band radars remains challenging and is often dependent on restriction parameters, for example, those derived from mountain returns. Therefore, these algorithms are applicable only in limited areas. The method proposed here uses measurements from C-band radars and hence can be applied in all regions covered by nationwide C- (or S-) band radar networks. First, a single scan of X-band radar measurements is used exemplary to identify advantages and disadvantages of the novel algorithm compared to a standard single radar algorithm. The performance of the correction algorithms in different types of precipitation is examined in nine case studies. The proposed method provides very promising results for each type of precipitation. Additionally, it is evaluated in a 5-month comparison with Micro Rain Radar (MRR) observations. The bias between uncorrected X-band radar and MRR data is nearly eliminated by the attenuation correction algorithm, and the RMSE is reduced by 20% while the correlation of ~0.9 between both systems remains nearly constant.

In this paper, we compare the performance of radar and optical (camera based) techniques in detecting vital signs such as respiratory rate (RR), heart rate (HR), and blood oxygen saturation (SpO2). Specifically, we investigate the application of ultrawideband stepped-frequency continuous-wave radar and imaging photoplethysmography (iPPG) techniques to measure vital signs. The radar performance can be enhanced by using phase information of backscattered signal instead of its amplitude. On the other hand, the iPPG system can be enhanced by using more than one camera and utilizing very selective narrowband filters coupled with good illumination. In either system, use of advanced signal processing is required to improve accuracy. Generally, HR and RR can be accurately read by either microwave radar or optical techniques with 500 lx illumination level to have < ±2% error up to 2 m distance between the subject and the system, but optical technique errors increase significantly to < ±15% for

An explicit expression for stochastic processes describing the dual-polarization weather radar echoes is presented. The probability distributions of the proposed model are defined in terms of the point values assumed by polarimetric and Doppler variables in the relevant radar sampling volume. The statistical properties of the model are discussed in order to verify its faithfulness as representative of real radar signals. The discussion considers the most general situation, i.e., it is not related to specific hydrometeor distributions or beam filling conditions.

A stepped-frequency radar that allows for adaptability in the radiated spectrum while maintaining high-resolution radar imagery has been developed. The spectrally agile frequency-incrementing reconfigurable (SAFIRE) radar system is a vehicle-mounted, ground-penetrating radar that is capable of producing high-resolution radar imagery for the detection of obscured targets (either buried or concealed surface targets). It can be easily transitioned between forward- and side-looking orientations. The SAFIRE system is capable of precisely excising subbands within its operating bandwidth, thus making the system “spectrally agile.” It is also highly reconfigurable thereby allowing for on-the-fly adjustment of many of the system parameters. The spectrally agile and reconfigurable aspects of the SAFIRE radar together with its enhanced IF processing scheme represent a novel contribution to the state of the art. This paper discusses the system design, implementation, and performance characteristics, and also presents preliminary high-resolution imagery.

The rising population of space debris poses an enormous threat to all space vehicles, including space shuttles and other spacecraft with operators aboard; and their detection, tracking, and identification are of great importance. Using the spinning motion and the translational motion component that is parallel to its major axis, we have established a 3-D spiral synthetic aperture radar (SAR) imaging geometry and its corresponding signal model for space debris in this letter. Spatial offsets and coupling in the along-track and altitude directions, caused by the spiral motion of the radar, are compensated in the frequency domain. With these compensation procedures, the spiral SAR is simplified as a cylindrical scan mode. Then, a 3-D wavenumber domain algorithm is proposed to realize coherent imaging. The real data processing results are presented to demonstrate the effectiveness of the proposed algorithm for imaging space debris.

This paper proposes an effective method of improving ship detection performance of a compact high-frequency (HF) radar system which has been primarily optimized for observing surface radial current velocities and bearings. Previously developed ship detection systems have been vulnerable to error sources such as environmental noise and clutter when they are applied in a compact HF radar optimized for observing surface current. In particular, the influences of error are reduced by applying a principle component analysis of the generated range-Doppler maps. A compact radar signal model is first developed by the data acquired from an operating compact HF radar site. The proposed method is then validated by comparing it to the conventional ship detection method in terms of detection and false alarm rates. The experimental results confirm that the proposed method shows superior performance in both simulated and practical environments.

When a pulse radar signal is implemented in a range-limited anechoic chamber for radar measurement, the transmitted and reflected signal will be coupled at the receiver. To solve this problem and equivalently simulate the whole process of pulse radar measurement in an anechoic chamber, the interrupted transmitting and receiving method is proposed in this letter based on interrupted sampling. The constraints of the transmitting and receiving parameters are deduced with the sizes of the anechoic chamber and target. The pulse compression of the proposed method is performed. Then, the window function is applied to extract the main peaks after pulse compression. Both the simulation and experimental results are provided to demonstrate the effectiveness of the proposed method in overcoming the coupling between the transmitted and reflected pulse signals.

In shipborne inverse synthetic aperture radar (ISAR), not only the target, but also the radar ship will have nonstationary 3-dimensional rotations induced by the irregular sea wave. Thus, how to compensate the radar ship’s rotations is the key problem in reconstructing the shipborne ISAR image of ship target successfully. In this letter, a novel received signal model of shipborne ISAR is proposed. On the basis of the proposed model, the Doppler frequency induced by the rotations of the target and the radar ship can be separated from the received signal, individually. An analysis of the effects of the radar ship’s rotations on the obtained image is given. Error analysis and imaging simulation are done and the results verified the correctness of the proposed model and the effects of the radar ship’s rotations.

Toward a maritime surveillance objective, many ship detection and tracking algorithms have been investigated but are faced with poor performance in practical ocean environments. Compact high-frequency (HF) radar has also faced critical issues due to its long coherent processing interval and varying response from its orthogonal antenna structure. Hence, a simulator based on compact HF radar is proposed in this letter to provide a guideline for effective assessment of ship detection and tracking algorithms while considering these practical issues. To validate the proposed simulator, the simulator generated data has been compared with real data obtained by the compact HF radar sites.

Based on the narrowband radar, an imaging method for space targets is proposed in this letter, which is named as single-range interferometric imaging. First, the theory of space target echo signal interferometric processing in narrowband radar is explained. Then, through conducting short-time Fourier transform on the echo signal received by three antennas, the curves on time-frequency plane correspond to different scatterers are effectively extracted and separated and the interferometric phase of different scatterers is obtained. Finally, 2-D imaging for space target is realized. Compared to existing methods, only a single multiantenna radar is needed to obtain the 2-D image of target with accurate scaling result. The simulation results under different occasions have confirmed the effectiveness of the proposed method.

This letter presents a two-tone radar sensor system that can concurrently detect both absolute distance and relative movement. In contrast to the traditional two-tone radar, the proposed radar sensor can measure both distance and vibration. Moreover, it is more accurate in predicting the phase shift by leveraging the accuracy of nonlinear phase demodulation in the digital domain. Unlike the frequency-modulated continuous wave radar, the proposed radar system has simpler system architecture and does not require broadband signals. With a tone difference of 40MHz, the radar system can detect a distance up to 1.875m without ambiguity. Experiments show that the proposed radar system was able to not only capture the delaying movement of a Newton's cradle but to measure the distance with mm accuracy as well. It successfully detected the gesture motion of virtual slider, making it promising for sensing action gestures for human-computer interaction.

The analysis and correction of the bias occurring in weather radar polarimetric measurements is a challenging problem. Polarization coupling due to the cross-polar radiation pattern of the radar’s antenna is known to be responsible for errors in the estimation of the polarimetric covariance matrix, and consequently in the hydrometeor classification and quantification, either when using the ATSR or the SHV method. An alternative method for Doppler and polarimetric measurements based on transmitting three different polarizations (3-PolD) has been proven to provide accurate polarimetric covariance matrix estimates without making any hypothesis about the target polarimetric response or its Doppler spectrum. This method does not reduce the Doppler capabilities or the unambiguous range of the radar despite alternately transmitting 3-PolD. These characteristics have encouraged evaluating the polarimetric parameter biases due to cross-polar radiation when this method is used. Biases are calculated considering reflector antenna systems as well as phased-array antenna systems. The results show that this method may guarantee a tolerable bias level even with a poor co- to cross-polar antenna pattern ratio.

A highly miniaturized and commercially available millimeter wave (mmw) radar sensor working in the frequency range between 121 and 127 GHz is presented in this paper. It can be used for distance measurements with an accuracy in the single-digit micrometer range. The sensor is based on the frequency modulated continuous wave (CW) radar principle; however, CW measurements are also possible due to its versatile design. An overview of the existing mmw radar sensors is given and the integrated radar sensor is shown in detail. The radio frequency part of the radar, which is implemented in SiGe technology, is described followed by the packaging concept. The radar circuitry on chip as well as the external antennas is completely integrated into an 8 mm $\times \,\, 8$ mm quad flat no leads package that is mounted on a low-cost baseband board. The packaging concept and the complete baseband hardware are explained in detail. A two-step approach is used for the radar signal evaluation: a coarse determination of the target position by the evaluation of the beat frequency combined with an additional determination of the phase of the signal. This leads to an accuracy within a single-digit micrometer range. The measurement results prove that an accuracy of better than $\pm 6~\mu \text{m}$ can be achieved with the sensor over a measurement distance of 35 mm.

Future weather radar systems will need to provide rapid updates within a flexible multifunctional overall radar network. This naturally leads to the use of electronically scanned phased array antennas. However, the traditional multifaced planar antenna approaches suffer from having radiation patterns that are variant in both beam shape and polarization as a function of electronic scan angle; even with practically challenging angle-dependent polarization correction, this places limitations on how accurately weather can be measured. A cylindrical array with commutated beams, on the other hand, can theoretically provide patterns that are invariant with respect to azimuth scanning with very pure polarizations. This paper summarizes recent measurements of the cylindrical polarimetric phased array radar demonstrator, a system designed to explore the benefits and limitations of a cylindrical array approach to these future weather radar applications.

Mobile radar platforms designed for observation of severe local storms have consistently pushed the boundaries of spatial and temporal resolution in order to allow for detailed analysis of storm structure and evolution. Digital beamforming, or radar imaging, is a technique that is similar in nature to a photograwphic camera, where data samples from different spaces at the same range are collected simultaneously. This allows for rapid volumetric update rates compared to radars that scan with a single narrow beam. The Atmospheric Imaging Radar (AIR) is a mobile X-band (3.14-cm wavelength) imaging weather radar that transmits a vertical, 20° fan beam and uses a 36-element receive array to form instantaneous range–height indicators (RHIs) with a native beamwidth of 1° × 1°. Rotation in azimuth allows for 20° × 90° volumetric updates in under 6 s, while advanced pulse compression techniques achieve 37.5-m range resolution. The AIR has been operational since 2012 and has collected data on tornadoes and supercells at ranges as close as 6 km, resulting in high spatial and temporal resolution observations of severe local storms. The use of atmospheric imaging is exploited to detail rapidly evolving phenomena that are difficult to observe with traditional scanning weather radars.

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.

An original 3-D radar imaging system is presented for radar cross section (RCS) analysis, i.e., to identify and characterize the radar backscattering components of an object. Based on a 3-D spherical experimental setup, where the residual echo signal is more efficiently reduced in the useful zone, it is especially adapted to deal with low-RCS analysis. Due to a roll rotation, the electric field direction varies concentrically while the scattered data are collected. To overcome this issue, a specific 3-D radar imaging algorithm is developed. Based on fast regularization inversion, more precisely the minimum norm least squares solution, it manages to determine, from a single pass collection, three huge 3-D scatterer maps at once, which correspond to HH, VV, and HV polarizations at emission and reception. The algorithm is applied successfully to real X-band datasets collected in the accurate 3-D spherical experimental layout, from a metallic cone with patches and an arrow shape. It is compared with the conventional 3-D polar format algorithm where the scatterer information is irretrievably mixed-up.

The design and test of a radio detection and ranging (Radar) sensor signal acquisition and processing platform is presented in this paper. The Radar sensor operates in real time and is suited for surveillance applications in transport systems. It includes a front-end with a continuous-wave frequency-modulated transceiver operating in X-band, with a single transmitter and multiple receivers, and a multichannel high-speed A/D converter. Sensor signal processing and data communication tasks with external hosts are managed by a field-programmable gate array. The signal processing chain includes region of interest selection, multidimensional fast Fourier transform, peak detection, alarm decision logic, data calibration, and diagnostic. By configuring the Radar sensing platform in low-power mode (7-dBm transmitted power), it is possible to detect still and moving targets with a covered range up to 300-m and 30-cm resolution. The measuring range can be increased up to 2 km by adding an extra 34.5-dBm power amplifier. The Radar sensing platform can be configured for a maximum detected speed of 200 km/h, with a resolution of 1.56 km/h, or a speed up to 50 km/h with a resolution of 0.4 km/h. The cross-range resolution depends on the number of receiving channels; a tradeoff can be found between cross-range resolution of the Radar sensor and its complexity and power consumption. With respect to the state of the art of surveillance Radar sensors and light detection and ranging, the proposed solution stands for its high configurability and for the better tradeoff that can be found in terms of covered distance and power consumption.

This paper presents an adaptive scan strategy concept for phased array weather radars (PAWR) with the objective of increasing the scan speed and capturing features of the storm system while maintaining the measurement accuracy. The adaptive scan strategy is developed based on the space–time variability of the storm under observation. Quickly evolving regions are scanned more often and the spatial sampling resolution is matched to the spatial scale. A model that includes the interaction between space and time is used to extract spatial and temporal scales of the medium and to define scanning regions. The temporal scale constrains the radar revisit time, while the measurement accuracy controls the radar’s dwell time. These conditions are employed in a task scheduler that works on a ray-by-ray basis and is designed to balance task priority and radar resources. The scheduler algorithm also includes an optimization procedure for minimizing radar scan time. The model and the scan strategy are demonstrated using simulation data. The results show that the proposed scan strategy can reduce the scan time significantly without compromising data quality.

The direct measurement of the angle rate of moving objects using a radar with a spatially diverse electric field pattern, a measurement analogous to the measurement of the range rate of a moving objects, represents, along with the measurements of range, range rate, and angle, a fourth basic radar measurement. Recently introduced and experimentally demonstrated, the theoretical accuracy of the direct measurement of angle rate is derived in this paper, and it is compared to the measurements of range, range rate, and angle in the context of the optimal signal forms for the best measurement accuracy. Signal forms achieving optimal accuracy for each measurement are discussed; example implementations of high-accuracy measurements are compared to the optimal forms; and the limitations of simultaneous measurements of pairs of measurements are derived. Combining the angle rate measurement with the three other standard radar measurements may provide future radar systems the capability to simultaneously and instantaneously measure the position and 3-D trajectory of moving objects without compromising the accuracy of any individual measurement.

Most applications of frequency-modulated continuous-wave radar described in the literature involve targets that are in relatively close proximity to the radar. In these cases, the round-trip travel time of the target’s radar signature is small relative to the transmit chirp duration, simplifying the processing required for range and velocity extraction. This is not the case for more distant targets, where much of the radar signature is received after the start of the subsequent transmit waveform. In this letter, we examine various signal-processing options for coping with this long-range condition. We analytically demonstrate how to retain both range and Doppler shift information for an arbitrary number of targets spaced anywhere from very near the target up to the radar’s unambiguous range. The motivation for this work is to develop a 95-GHz Doppler radar for measuring ice and dust particle dynamics in cometary jets. Simulations and experimental results are provided to validate our methods.

Frequency diverse array (FDA), which employs a small frequency increment across the array elements, is able to resolve range ambiguity. However, the frequency diversity results in angle-Doppler-defocusing of target especially at a high speed in space-time adaptive processing (STAP) radar, thus, causing serious detection performance degradation. In this paper, a robust adaptive beamforming approach is proposed for the FDA-STAP radar to enhance fast-moving target detection performance. In our solution, a large feasible region is employed to include the true steering vector of target. To avoid the trivial solution, an angle-Doppler-defocusing steering vector constraint is devised and incorporated into the large feasible region. The problem is formulated as a nonconvex quadratically constrained quadratic program which is efficiently solved via semidefinite relaxation technique. Because the retrieved steering vector of target is close to the true one, the performance is significantly improved. It is demonstrated via computer simulations that the proposed algorithm is superior to the state-of-the-art methods, which includes maintaining the mainlobe of the beampattern and improving the signal-to-clutter-plus-noise ratio performance.

This paper describes a method of processing marine radar signals for the purpose of generating phase-resolved surface elevation maps as well as statistical measures of ocean surface wave fields. The method is well suited to the processing of data collected by marine radars because it allows for the incorporation of effects dependent on the radar look direction relative to the propagation direction of ocean waves. Applications to Doppler radar and backscattered power measurements are described, and example results are presented using simulated radar data.

The optimal design of pulse compression waveform/filter pairs for use with near-nadir spaceborne radar in low earth orbit for the observation of clouds and precipitation is discussed. An optimization technique is introduced that considers performance metrics specific to the remote sensing of clouds and precipitation from such platforms. Specifically, the sensitivity of the radar to precipitation and clouds is maximized as close to the ground as required. The sensitivity of the radar near the surface is typically limited by the pulse compression range sidelobes from the surface’s echo. Optimization of the waveform/filter pair’s performance is facilitated by a time-domain radar scattering model to simulate radar reflectivity range profiles. The presented radar-scattering model accounts for the radar’s configuration constraints and platform motion, as well as the spatial distribution and relative motion of the scatterers. In this paper, the optimization of both linear frequency modulation (LFM) and nonlinear frequency modulation (NLFM) waveforms is considered. It is demonstrated that the LFMwaveforms provide superior performance over NLFM waveforms for application subject to unmitigated Doppler shifts.

TARA (Telescope Array Radar) is a cosmic ray radar detection experiment colocated with Telescope Array, the conventional surface scintillation detector (SD) and fluorescence telescope detector (FD) near Delta, Utah, U.S.A. The TARA detector combines a 40 kW, 54.1 MHz VHF transmitter and high-gain transmitting antenna which broadcasts the radar carrier over the SD array and within the FD field of view, towards a 250 MS/s DAQ receiver. TARA has been collecting data since 2013 with the primary goal of observing the radar signatures of extensive air showers (EAS). Simulations indicate that echoes are expected to be short in duration (~10 microseconds) and exhibit rapidly changing frequency, with rates on the order of 1 MHz/microsecond. The EAS radar cross-section (RCS) is currently unknown although it is the subject of over 70 years of speculation. A novel signal search technique is described in which the expected radar echo of a particular air shower is used as a matched filter template and compared to waveforms obtained by triggering the radar DAQ using the Telescope Array fluorescence detector. No evidence for the scattering of radio frequency radiation by EAS is obtained to date. We report the first quantitative RCS upper limits using EAS that triggered the Telescope Array Fluorescence Detector., Comment: 21 pages, 30 figures

Aiming at the influence of the complex electromagnetic environment to radar, a method of visualization for radar electromagnetic waves under the influence of electronic jamming is presented. Firstly, presenting the flow of visualization for radar electromagnetic. Secondly, modeling the radar detection range under the influence of electronic jamming. Finally, getting the 3-D visualization scene of radar electromagnetic wave under the influence of electronic jamming with STK and OpenGL.

In modern warfare, as a long distance detection equipment, a reconnaissance radar is crucial to monitor the sensitive regions and the intelligence of airborne targets. It is important for the opponent to identify the tactical information about the enemy’s reconnaissance radar. It has a great influence on the war. Scanning cycle of the monitoring radar is an important parameter for the counterreconnaissance of the hostile radar source in the electronic countermeasure. Since the pulse Doppler (PD) radar is one of the most widely used type in modern reconnaissance radar domains, this paper focuses on scanning cycle estimation of the reconnaissance radar (PD radar) using a single unmanned aerial vehicle (UAV). We propose an effective method to reconstruct the main-beam pattern (MBP) curve of the radar antenna based on the norm approximation algorithm, and then the reconstructed MBP curve of the radar antenna is exploited to estimate the scanning cycle of the reconnaissance radar. By hovering the UAV at the same place, the scanning cycle of the reconnaissance radar can be estimated according to the reconstructed MBP curve. In the simulation section, we check the validity and robustness of the proposed method through the performance comparison with the Cramer-Rao lower bound.

Civil marine radar, which operates at a low grazing-incidence angle and with horizontal polarization in transmitting and receiving, can be modified and used as a primary tool for surface wave monitoring. The high spatial resolutions of sea-clutter image sequences from X-band radar offer a means of deriving individual waves and wave field at low-cost. However, the performance of X-band radar is impaired under rainy conditions, which are usually accompanied by the severe weather at sea. In the present study, we examine the effectiveness of S-band radar for wave measurements under precipitation. The results of comprehensive comparative studies with sea-truth data show that S-band radar is capable of carrying out wave measurements in rainy conditions. Although the longer wavelength of the S-band leads to a coarser resolution of radar imagery, the S-band radar features at least the equivalent performance of the X-band system in non-rainy conditions, in terms of wave height measurement. The results suggest that the S-band and X-band could be complementary systems. In rainy conditions the S-band is more efficient but in the non-rainy periods the X-band gives more confident results. The relationship of significant wave height with radar signal-to-noise ratio (SNR), and the modulation transfer function (MTF) between radar spectrum and wave spectrum for the used X-band and S-band radars are established and discussed in this paper.

The aim of the radar systems is to collect information about their surroundings. In many scenarios besides static targets there are numerous moving objects with very different characteristics, such as extent, movement behavior or micro-Doppler spread. It would be most desirable to have algorithms that extract all information on static and moving object automatically, without a system operator. In this paper, we present measurements conducted with a commercially available high-resolution multi-channel linear frequency-modulated continuous-wave radar and algorithms that do not only produce radar images but a description of the scenario on a higher level. After conventional spectrum estimation and thresholding, we present a clustering stage that combines individual detections and generates representations of each target individually. This stage is followed by a Kalman filter based multi-target tracking block. The tracker allows us to follow each target and collect its properties over time. With this method of jointly estimating tracks and characteristics of each individual target in a scenario, inputs for classifiers can be generated. Which, in turn, will be able to generate information that could be used for driver assistance or alarm trigger systems.

In this letter, we propose a method for estimating the center of rotation on an experimental radar imaging. The experiment is performed with tomographic approach to obtain the radar cross section images of the target on a rotation table. In an ultrahigh-resolution imaging using tomographic reconstruction, precise knowledge of rotation center of the turntable position is necessary since this has a big influence on the image quality. The position of rotation center can be physically measured, but the result is not accurate due to the delay introduced by the RF components and cables. Thus, we present a method to precisely determine the rotation center based on the rotational symmetry of the received data. The proposed method is verified by doing imaging of several targets using ultrawideband radar with picosecond-length pulses. The system bandwidth is larger than 30 GHz, and the imaging results have subcentimeter resolution.

The frequency diverse array (FDA) has a range-angle-dependent transmit beampattern, which can provide the potential capability for novel radar application. However, the basic FDA's beampattern is periodic in range and coupled in range and angle dimensions, which limits the application of FDA in radar field. In this letter, we propose a novel FDA model with nonmonotone increasing frequency offset to form a narrow pencil beam, which eliminates the range periodicity and coupling of range and angle domains. Combining this new FDA with multiple-input–multiple-output radar, not only can multiple narrow pencil beams be formed to track multiple targets simultaneously, but also a flat-top transmit beampattern for targets searching can be synthesized. Simulation results show the effectiveness and outperformance of the proposed scheme compared to the existing Log-FDA, which uses the logarithmically increasing frequency offset.

Multiple-input-multiple-output (MIMO) radar image processing presents problems difficult to address by modifying conventional monostatic radar methods as Fourier range migration. When the distance between the transmitter and receiver is comparable to the target size, the single phase center approximation is not accurate. Furthermore, if the antenna radiation pattern significantly deviates from a spherical wave, the symmetries assumed in most range migration techniques are violated. We present a rapid Fourier-based MIMO reconstruction called Fourier accelerated multistatic imaging (FAMI) suitable for massively parallel computation that accounts for frequency-dependent radiation patterns, does not require the single phase center approximation, and is able to dynamically adapt to different target support volume shapes. FAMI is especially suitable for frequency-diversity antenna systems that use spectrally modulated coded spatial radiation patterns.

Although antennas have well-known power patterns that are commonly used to understand the quality of measurements, they also have phase patterns that are difficult to obtain and are seldom discussed in the radar meteorological community. This study presents the characteristics of the antenna phase pattern of the McGill S-band radar. Phase variations in azimuth and elevation with respect to the main beam axis are obtained using high-resolution scans of an isolated ground target and of an emission source. The two-way phase pattern is relatively constant within the radar main beam, but it changes rapidly at the power minima between the main beam and the first sidelobe. The effects of this phase pattern on ground and weather targets were evaluated and were found to be much more pronounced for point targets than for distributed targets. Nevertheless, proper knowledge of the phase pattern of the radar antenna would enhance the ability to better select ground targets for radar refractivity retrieval and to estimate the quality of radar data.

This letter proposes a novel pulse accumulation scheme via structured measurement matrix in compressive sensing radar for better detection performance in the presence of high-level additive noise. The measurement matrix allows radar accumulate pulses with both coherent and noncoherent accumulation. The range migration can be accurately compensated via time delay compensation matrix based on frequency domain weighting. A modified algorithm is derived to recover the structured joint sparse vectors. By implementing numerical simulations, it is demonstrated that better detection performance and more accuracy can be achieved through the proposed scheme.

A complete circularly polarized 210–270-GHz frequency-modulated continuous-wave radar with a monostatic homodyne architecture is presented. It consists of a highly integrated radio-frequency transceiver module, an in-house developed linear-frequency chirp generator, and a data acquisition chain. The radar front end featuring a fundamentally operated $\times$ 16 multiplier-chain architecture is realized as a single chip in 0.13- $\mu$ m SiGe heterojunction bipolar transistor technology with a lens-coupled circularly polarized on-chip antenna and wire-bonded on a low-cost printed circuit board. In combination with a 9-mm-diameter silicon lens, the module achieves an average in-band directivity of 26.6 dB. The measured peak radiated power from the packaged radar module is $+$ 5 dBm and the noise figure is 21 dB. For a 60-GHz frequency sweep, the radar achieves a range resolution of 2.57 mm after calibration, which is close to the theoretical bandwidth-limited resolution of 2.5 mm. With a simple scanning optical setup, this paper further demonstrates the 3-D imaging capability of the radar for detection of hidden objects with a remarkable dynamic range of around 50 dB.

We propose a polarization-sensitive directional borehole radar with a dipole array and loop antenna in a borehole (DALAB), along with an algorithm for radar signal processing. This radar enables us to discriminate between a vertical conducting cylinder and inhomogeneity in soil in 3-D space. The antenna configuration difference, antenna coupling, and borehole effects were calibrated using the method of moments (MoM) in the proposed algorithm. According to computer simulation, the magnitude of the polarization ratio (MPR) of the incident wave may be used for discrimination between signals from targets and background reflections. A prototype of the borehole radar with the DALAB was constructed and tested in laboratory and field experiments. In the laboratory, we confirmed that the DALAB can estimate the polarization state of an incident wave despite the presence of a water layer. In field testing, we confirmed that the MPR was nearly 0 dB, as theoretically estimated when the DALAB received electromagnetic waves radiated by a tilted dipole antenna. We also carried out single-hole measurements with the DALAB and found that the MPR of a reflected wave from a vertical conducting cylinder was more than 20 dB, whereas that from soil inhomogeneity was less than about 20 dB. This implies that we may discriminate between a conducting cylinder and soil inhomogeneity and determine target locations in three dimensions using the DALAB and the MPR.

Through-the-wall radar imaging systems are utilized for mapping buildings' interiors and detecting static and moving objects hidden behind the walls. The current techniques rely on large linear antenna arrays with directional radiation pattern for obtaining high cross-range resolution, and their imaging capability is limited by the low array processing gain and field of view. This paper introduces a new technique for through-the-wall radar imaging in which the linear array is replaced by a dense 2-D synthetic array formed by an ad hoc network of moving transceivers with omnidirectional antennas. Applying this method enables imaging of building interiors from outside or inside with 360° field of view. As receivers move, the direct and reflected signals from a stationary transmitter are sampled at different positions within the roaming domain, and by combining such signal samples using an appropriate beam-forming technique, a large and dense array is synthesized to provide an accurate radar map of the buildings' interiors and hidden objects in all directions. To increase the system dynamic range, the direct signals between the transmitter (Tx) and receiver (Rx) antennas are reduced, utilizing orthogonal polarizations for Tx and Rx. To improve the range resolution and reduce the background noise, a new method based on the generalized pencil of function method is proposed. This method can accurately detect the locations of the reflecting points within the image which, in combination with the standard back-projection focusing, provides high-quality radar images. A finite-element method for a simple building structure and ray tracing for a large 3-D building structure are used to evaluate the performance of the proposed method.