Radar Range Research Articles

Trapezium backed dual circularly polarised hepta-band monopole antenna

ABSTRACT This paper presents a hepta-band planar monopole antenna which exhibits circular polarization (CP) at two bands and linear polarization at other five bands. Combination of rectangular slots to form a single E-shaped structure has been introduced in half ground to excite hepta-band operations. Asymmetric trapezoidal parasitic element is also placed under the monopole radiator positioned at upper half ground plane of antenna. Due to asymmetric effect attained by the placement of trapezium, CP is achieved at 4.2 GHz and 10 GHz with 3-dB axial ratio bandwidth of 4.21–4.29 GHz and 9.92–10.01 GHz, respectively. The antenna acquires remaining five resonant modes at 2.4 GHz, 5.4 GHz, 7.2 GHz, 8.86 GHz and 11.8 GHz with 10-dB impedance bandwidth of 90 MHz, 160 MHz, 100 MHz, 200 MHz and 410 MHz, respectively. Sensitive study of the E slot and trapezoidal structured geometry is conducted. The proposed antenna is designed on low cost FR4 (εr = 4.4, tanδ = 0.02). To ensure the practicability, the proposed antenna design is fabricated and measured. A good agreement of simulation and measurement validates the proposed designed. The antenna has potential to cover frequency bands of IEEE802.11, Bluetooth, WLAN, WiMAX, Satellite Communication, Short Range RADARs and Radio band applications.

Multi-Subband Radar Signal Fusion Processing Based on Deep Neural Network in Low Signal-to-Noise Ratio

The traditional multi-subband radar signal fusion method based on pole information fits nonlinear signals via linear models. It is very important to accurately estimate the order of the pole model, as the wrong order will lead to errors in the resulting fusion signal. In the case of low signal-to-noise ratio (SNR), it is difficult to obtain accurate pole values. When a noise suppression method is included in the algorithm, the influence of noise on the pole order may be effectively avoided. However, traditional methods have many complex links, and only a few samples can be tested each time. Also, approximating a linear model onto a nonlinear signal will inevitably have errors. Therefore, this paper proposes a method based on the deep neural network (DNN) that applies nonlinear fitting of deep learning to complete the fusion process. The multi-subband distance envelopes are input into the DNN, and the fusion full-band distance envelopes are obtained as the output. Using DNN for subband fusion could improve the radar range resolution and obtain high-resolution one-dimensional range profiles.

Layered subsurface in Utopia Basin of Mars revealed by Zhurong rover radar

Exploring the subsurface structure and stratification of Mars advances our understanding of Martian geology, hydrological evolution and palaeoclimatic changes, and has been a main task for past and continuing Mars exploration missions1–10. Utopia Planitia, the smooth plains of volcanic and sedimentary strata that infilled the Utopia impact crater, has been a prime target for such exploration as it is inferred to have hosted an ancient ocean on Mars11–13. However, 45 years have passed since Viking-2 provided ground-based detection results. Here we report an in situ ground-penetrating radar survey of Martian subsurface structure in a southern marginal area of Utopia Planitia conducted by the Zhurong rover of the Tianwen-1 mission. A detailed subsurface image profile is constructed along the roughly 1,171 m traverse of the rover, showing an approximately 70-m-thick, multi-layered structure below a less than 10-m-thick regolith. Although alternative models deserve further scrutiny, the new radar image suggests the occurrence of episodic hydraulic flooding sedimentation that is interpreted to represent the basin infilling of Utopia Planitia during the Late Hesperian to Amazonian. While no direct evidence for the existence of liquid water was found within the radar detection depth range, we cannot rule out the presence of saline ice in the subsurface of the landing area.

High-Resolution Range Profile Feature Transformation Method Based on Amplitude-Phase Modulation Metasurface

Time-modulated metasurfaces have attracted much attention due to their flexible manipulation of electromagnetic waves. Time-varying response leads to spread-spectrum and reallocation of energy. Thus, an amplitude-phase joint modulation (TAJM) method is proposed based on a time-modulated active polarization conversion metasurface (APCM). Taking radar high resolution range profile (HRRP) as the object, the distance transformation and multi-target phenomena are further discovered. The proposed method achieves a flexible manipulation of target amplitude and phase. The relationship between the modulation parameters and HRRP feature is studied. It is revealed that the absorption depth is the dominant factor for the energy distribution of TAJM. The method can be applied to multi-target generation and target feature manipulation.

Intelligent radar HRRP target recognition based on CNN-BERT model

Stable and reliable feature extraction is crucial for radar high-resolution range profile (HRRP) target recognition. Owing to the complex structure of HRRP data, existing feature extraction methods fail to achieve satisfactory performance. This study proposes a new deep learning model named convolutional neural network–bidirectional encoder representations from transformers (CNN-BERT), using the spatio–temporal structure embedded in HRRP for target recognition. The convolutional token embedding module characterizes the local spatial structure of the target and generates the sequence features by token embedding. The BERT module captures the long-term temporal dependence among range cells within HRRP through the multi-head self-attention mechanism. Furthermore, a novel cost function that simultaneously considers the recognition and rejection ability is designed. Extensive experiments on measured HRRP data reveal the superior performance of the proposed model.

Temporal and altitudinal variability of the spread F observed by the VHF radar over Christmas Island

Abstract. The goal of this work is to study the time and altitude echo characteristics under different solar and seasonality conditions using the VHF radar range–time–intensity (RTI) images. The occurrence of equatorial spread F depends on the existence of conditions that can seed the Rayleigh–Taylor instability, and these conditions can change with solar flux, seasonality, longitude distributions, and day-to-day variability. So, the equatorial spread F is observed as its time and altitude occurrence. The VHF radar of Christmas Island (2.0∘ N, 157.4∘ W, 2.9∘ N dip latitude) has been operational in the equatorial region for some time, allowing long-term observations. The occurrence of echoes during solar minimum conditions is observed throughout the night since the post-reversal westward electric field is weaker than the solar maximum and the possibilities of the vertical plasma drift becoming positive are larger. On the other hand, echoes during solar maximum will be controlled by dynamics near the time of the pre-reversal peak (PRE). Our results indicate that the peak time occurrence of echoes along this period shows a well-defined pattern, with echoes distributed as closer to local sunset during solar maximum and around/closer to midnight during solar minimum conditions; meanwhile, the peak altitude occurrence of echoes shows a slightly regular pattern with higher-altitude occurrences during solar maxima and lower altitudes during solar minimum conditions.

Robust Distributed Rendezvous Using Multiple Robots with Variable Range Radars

This paper considers multi-robot systems, such that each robot has a radar for detecting its neighbor robots. We consider a practical scenario in which a radar sensor contains measurement noise, and the environmental disturbance generates process noise in a robot’s maneuvering. We consider a 3D scenario such that the network can be split initially. For instance, complete failures of one or more robots can split the network. Considering 3D environments, the goal of our paper is to let all robots rendezvous in a distributed manner so that the network connectivity can be recovered even after the network is split. Robust distributed rendezvous control is designed so that the network connectivity is maintained (or recovered) during the maneuvering of a robot. To recover the network connectivity, we adaptively control the robot’s radar footprint by increasing the transmission power level (adjust the amplifier in the transmitter). To the best of our knowledge, this paper is novel in applying a radar with a variable sensing range in order to make all robots rendezvous in 3D environments. We address MATLAB simulations to demonstrate the outperformance of our rendezvous approach with variable range radars by comparing it with the state-of-the-art in multi-robot rendezvous controls.

Optimal Configuration of Array Elements for Hybrid Distributed PA-MIMO Radar System Based on Target Detection

This paper establishes a hybrid distributed phased array multiple-input multiple-output (PA-MIMO) radar system model to improve the target detection performance by combining coherent processing gain and spatial diversity gain. First, the radar system signal model and array space configuration model for the PA-MIMO radar are established. Then, a novel likelihood ratio test (LRT) detector is derived based on the Neyman–Pearson (NP) criterion in a fixed noise background. It can jointly optimize the coherent processing gain and spatial diversity gain of the system by implementing subarray level and array element level optimal configuration at both receiver and transmitter ends in a uniform blocking manner. On this basis, three typical optimization problems are discussed from three aspects, i.e., the detection probability, the effective radar range, and the radar system equipment volume. The approximate closed-form solutions of them are constructed and solved by the proposed quantum particle swarm optimization-based stochastic rounding (SR-QPSO) algorithm. Through the simulations, it is verified that the proposed optimal configuration of the hybrid distributed PA-MIMO radar system offers substantial improvements compared to the other typical radar systems, detection probability of 0.98, and an effective range of 1166.3 km, which significantly improves the detection performance.

Analysis of ADAS Radars with Electronic Warfare Perspective.

The increasing demand in the development of autonomous driving systems makes the employment of automotive radars unavoidable. Such a motivation for the demonstration of fully-autonomous vehicles brings the challenge of secure driving under high traffic jam conditions. In this paper, we present the investigation of Advanced Driver Assistance Systems (ADAS) radars from the perspective of electronic warfare (EW). Close to real life, four ADAS jamming scenarios have been defined. Considering these scenarios, the necessary jamming power to jam ADAS radars is calculated. The required jamming Effective Radiated Power (ERP) is −2 dBm to 40 dBm depending on the jamming scenario. These ERP values are very low and easily realizable. Moreover, the effect of the jamming has been investigated on the radar detection at radar Range Doppler Map (RDM) and 2-Dimensional Constant False Alarm Rate (2D-CFAR). Furthermore, the possible jamming system requirements have been investigated. It is noted that the required jamming system will not require high-end technology. It is concluded that for the security of automotive driving, the ADAS radar manufacturer should consider the intentional jamming and related Electronic Counter Countermeasures (ECCM) features in the design of ADAS radars.

Detection of Electronic Devices Using FMCW Nonlinear Radar.

Nonlinear radars can be utilized to detect electronic devices, which are difficult to detect with conventional radars due to their small radar cross sections (RCS). Since the receiver in a nonlinear radar is designed to only receive harmonic or intermodulated echoes from electronic devices, it is able to separate electronic devices from non-electronic scatters (clutter) by rejecting their echoes at fundamental frequencies. This paper presents a harmonic-based nonlinear radar scheme utilizing frequency-modulated continuous-wave (FMCW) signals for the detection of various electronic devices at short range. Using a laboratory experiment setup for FMCW radar at S-band for Tx (C-band for Rx), measurements are carried out to detect electronic devices of various sizes. The results show that the detection of small electronic devices is possible with nonlinear FMCW radar when appropriate system parameters are selected. Furthermore, we also discuss the maximum detectable range estimation for electronic targets using the radar range equation for FMCW nonlinear radar.

TRAP: Traffic-Based Adaptive Ramp Packing for Blind Cancellation in Autonomous Vehicles

Autonomous Vehicles (AVs) rely on a set of radar sensors used to map surrounding environment. Most commonly used radar sensors for AVs use Frequency Modulated Continuous Wave (FMCW) ramps for object parameter (i.e., range and relative velocity) estimation. Due to large bandwidth requirement of FMCW radar, only a limited number of AVs can be operated in the available spectrum. Consequently, the co-existence of large number of AVs may lead to the problem of radar-to-radar interference, also referred to as radar blindness. Moreover, the problem becomes more severe in the higher traffic scenarios. In this work, we propose a Traffic-based Adaptive Ramp Packing (TRAP) scheme, which adapts radar range and assigns FMCW ramp parameters on the basis of inter-vehicular distance among AVs. Specifically, TRAP scheme allows to make effective use of the available time-frequency resource, and enables to pack more ramps in the dense traffic scenarios. Further, it is shown that adaptive radar range adoption may provide significantly more number of ramps in the given bandwidth. Furthermore, through simulation results, it is shown that TRAP significantly reduces the blind probability against state-of-the-art fixed range schemes.

Microwave absorption properties of carbonyl iron-based paint coatings for military applications

The paper explores the possibilities of using carbonyl iron in the form of a powder for the manufacture of radar-absorbing paints – reducing the radar signature of the objects that they cover. The attenuation values in the range of 4–18 GHz for various coating thicknesses, ranging from 0.5 to 2.00 mm with 0.5 mm increment, and for different absorber content −75% and 80%, as well as the use of two different binders in the form of epoxy resins with hardeners, were investigated. For the frequency of 18 GHz and a 1.5 mm thick coating with a 75% absorber content, Epidian 112 resin and Saduramid 10/50 hardener used as a binder, and the maximum attenuation level obtained equalled 20.2 dB at 16 GHz. Additionally, the absorber particle size ranging from 3 to 4 μm and its higher mass content resulted in achieving the reflection loss above −12 dB in the entire 8–12.5 GHz range for layers between 1- and 1.5 mm thickness. The qualitative assessment of the tested samples in the context of camouflage in the radar range was also performed, using statistical analysis.

Quantitative Prediction of Sea Clutter Power Based on Improved Grey Markov Model

The detection and prediction of sea clutter power is the basis of inversing atmospheric duct. At present, the technology of atmospheric duct within radar detection range is relatively perfect, but the long-distance inversion of atmospheric duct is limited by radar detection range, and the prediction of the echo power of the measured sea clutter is the basis of long-distance inversion of atmospheric duct. Based on the theory of weighted Markov model and grey Markov model, a weighted grey Markov model is constructed, and the sliding method is introduced to establish the sliding weighted grey Markov model. The relative error between the measured sea clutter power and predicted values of the above four models is calculated and analyzed using the experimental data collected. The results show that the sliding weighted grey Markov model has better accuracy not only in short-range prediction but also in long-distance prediction, which could provide data support for inversing atmospheric duct.

Millimeter-wave joint radar and communication system based on photonic frequency-multiplying constant envelope LFM-OFDM.

The joint radar and communication (JRC) system providing both large-capacity transmission and high-resolution ranging will play a pivotal role in the next-generation wireless networks (e.g., 6G and beyond) and defense applications. Here, we propose and experimentally demonstrate a novel photonics-assisted millimeter-wave (mm-wave) JRC system with a multi-Gbit/s data rate for communication function and centimeter-level range resolution for radar function. The key is the design of the intermediate-frequency (IF) JRC signal through the angle modulation of the linear frequency modulation (LFM) radar carrier using orthogonal frequency division multiplexing (OFDM) communication signal, inspired by the idea of constant-envelope OFDM (CE-OFDM). This IF angle-modulated waveform facilitates the broadband photonic frequency (phase)-multiplying scheme to generate mm-wave JRC signal with multiplied instantaneous bandwidth and phase modulation index for high-resolution LFM radar and noise-robust CE-OFDM communication. It is with fixed low power-to-average power ratio to render robustness against the nonlinear distortions. In proof-of-concept experiments, a 60-GHz JRC signal with an instantaneous bandwidth over 10-GHz is synthesized through a CE-LFM-OFDM signal encoded with a 2-GBaud 16-QAM OFDM signal. Consequently, a 1.5-cm range resolution of two-dimension imaging and an 8-Gbit/s data rate are achieved for both radar and communication functions, respectively. Furthermore, the proposed JRC system is able to achieve higher radar range resolution and better anti-noise communication, when using higher-order photonic frequency multiplying.

Требования к кодирующей матрице фазокодоманипулированного зондирующего сигнала с нулевой зоной автокорреляции.

Optimal discrete signals does not allow solving the problem of radar range resolution for echo signals overlapping in time with significantly different amplitudes. Also, these signals limit the possibility of improving the quality of the radar image in radar of different applications due correlation noise. Therefore, to solve the above problem, it is of interest to use a probing signal with a zero autocorrelation zone. To form an autocorrelation function with a zero sidelobes region, the probing signal must be a pulse train of two or more phase-code-manipulated pulses. It is analytically substantiated in the paper that in order to form a zero autocorrelation zone, a pulse train of pulses must be coded by an ensemble of complementary or orthogonal sequences. In this case, the probing signal will have a large number of pulses in a pulse train, which makes it difficult to use it in a radar with a common transmitting and receiving antenna. It is shown that when coding by an ensemble of complementary sequences, the complex envelopes of all discrete pulses in a pulse train must be equal. In this case, the compressed signal will have a sufficiently high sidelobe ratios in a zero autocorrelation zone with Doppler mismatch. It has also been analytically proved that in order to form a zero autocorrelation zone, a pulse train of pulses can be coded by rows of a block matrix, consisting of a set of mutually orthogonal matrices. Then the complex envelopes of discrete pulses in a pulse train can be different, which makes it possible to suppress the level of sidelobes in a zero autocorrelation zone with Doppler mismatch. The paper also contains the requirements for the coding matrix of a polyphase (p-phase, where р ≥ 2 – prime number) probing signal with a zero autocorrelation zone, consisting of a minimum number of pulses in a pulse train equal to p, called a coherent complemented signal.

A Comprehensive Review on Automotive Antennas for Short Range Radar Communications

A Comprehensive Review on Automotive Antennas for Short Range Radar Communications

Generalized Radar Range Equation Applied to the Whole Field Region.

Most terahertz (THz) radar systems can only work in the near-field region, because the THz source power is limited and the size of the target scattered near field is up to tens of kilometers. Such conditions will result in the conventional radar range equation being unsuitable. Therefore, the near-field radar cross section (RCS) formula is given according to the numerical simulation on different targets. By modifying the parameters in the near field, including the gain of radar antennas and the RCS of targets, the generalized radar range equation is proposed. The THz radar working efficiency in the whole range and the simulation of the near-field RCS simulation model were employed to validate its effectiveness. Through comparison with the radar range equation, it can be concluded that the calculation results of the proposed equation are smaller in the near field, and the outcomes in the far field are identical. The proposed generalized radar range equation can be applied to the whole radiation area including the near field and the far field. Furthermore, more complicated real targets are calculated according to the generalized radar range equation and it can be extended from the submillimeter wave band to a much wider band range. Finally, the near-field radar theory is established, which shows its potential application to the radar cross section estimation in the extremely high frequency and fine design of THz radar systems.

Ultra-Wide Band Double-Slot Podal and Antipodal Vivaldi Antennas Feed by Compact Out-Of-Phase Power Divider Slot for Fluid Properties Determination.

In this paper, double slot podal and antipodal ultra-wideband (UWB) microstrip antennas for a fluid property measurement system are proposed. Among different feeding techniques, out of phase uni-planner power divider approach is used. The performance verification of the proposed antenna is explained, along with a performance comparison of the antenna bandwidth, feeding, and the realized gain. The suggested podal antenna has an impedance bandwidth from 2.4 to 15.4 GHz, with a maximum gain of 11.3 dBi in the 12 GHz region while the antipodal antenna has a 2.8 GHz to 16 GHz impedance bandwidth, with a maximum gain of 10.4 dBi in the 10 GHz region. Within the intended band, the radiation pattern had an excellent directivity characteristic. The implementation of the proposed antenna is calibrated by measuring the propagated signals response via various liquid specimens using UWB radar, which might be applied for fluid sensing and prediction purposes. The proposed antenna was connected to an NVA-R661 module of Xethru Inc. for measuring the sample delay and peak-to-peak amplitude of the received signals passing through specimens. The measured parameters at a different radar frequency range of transmission are applied by drawing the fluid viscous analogy based on Poiseuille’s law hypothesis, showing clear differentiation between the test specimens.

Inverse synthetic aperture radar range profile compensation of plasma-sheath-enveloped reentry object

The scattering points in a plasma sheath characterized with coupled velocities can cause pulse compression mismatching, which results in displacement and energy diffusion in the one-dimension range profile. To solve this problem, we deduce the echo model of the plasma-sheath-enveloped reentry object. By estimating the coupled velocities, we propose a compensation method to correct the defocus of an inverse synthetic aperture radar (ISAR) image in range dimension to improve the quality of the ISAR images. The simulation results suggest that the echoes from different regions of the surface of the reentry object have various coupling velocities, and the higher the coupled velocity, the more serious the displacement and energy diffusion in the range dimension. Our proposed method can correct the range dimension aberration. Two measurement metrics were used to evaluate the improvement of the compensation method.

Atmospheric Propagation Studies and Development of New Instrumentation for Astronomy, Radar, and Telecommunication Applications in the Subterahertz Frequency Range

Current progress in the development of new subterahertz instruments discussed in this paper, including antennas, high-power gyrotrons, and low-noise receivers, provides a wide range of possible applications. Atmospheric absorption has now become a major limitation in the application of such high-performance subTHz systems, and the choice of the optimal location of antennas for astronomical, radar, and communication systems is important. The latest results of studying the microwave astroclimate in northern Eurasia are presented. Based on these studies, new perspectives and corrected plans for installing new antennas at the Suffa Plateau and in the Caucasus are formulated, and possible applications of new instruments such as radars for locating space debris and communication hubs for deep space communications, which are based on extremely-high-power gyrotrons and low-noise superconducting receivers, are discussed.