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In this paper, a method for nonlinear target recognition via machine learning is presented. The nonlinear radar environment used in this study was a frequency-modulated continuous-wave (FMCW) nonlinear radar with a transmit frequency band of 3.0∼3.2 GHz and received a frequency band of 6∼6.4 GHz corresponding to the second harmonics. Nonlinear radar measurements were performed using four types of electronic devices as nonlinear targets. Statistical parameters were extracted from the measured amplitude spectrum of the received harmonic responses for each target to successfully construct a classification algorithm. The extracted characteristic data were then used to construct and verify a support vector machine (SVM) classifier. The accuracy of the target classification by the trained SVM classifier was confirmed through verification data, and an accuracy of 85 % with 10-fold cross-validation was demonstrated. [ABSTRACT FROM AUTHOR]

FMICW radars detect and track targets using frequency information based on the distance and velocity of the target. Therefore, the phase noise of the received signal and the frequency resolution must be minimized to ensure detection and tracking accuracy of the radars. However, as the signal frequency increases, the phase noise degrades. Therefore, the design requirement of the phase noise is important for radar using high-frequency signals. In this study, the phase noise of the transmission signal (FTX), local oscillation signal (FLO1, FLO2), and reference signal (Fref) are analyzed for application to a W-band compact radar. Additionally, phase-noise require- ments are derived to increase the frequency resolution of the radar within a range that can be implemented in a W-band transceiver. [ABSTRACT FROM AUTHOR]

This study presents a Ka-band direct-conversion receiver using a 28-nm CMOS (Complimentary Metal Oxide Semiconductor) process for radar applications. The designed receiver includes a LNA (Low-Noise Amplifier), Mixer, and Baseband amplifier. The LNA adopts a two-stage cascode amplifier structure. Then, the mixer is a single-balanced passive mixer with low flicker noise. At the end, the baseband amplifier is a transimpedance amplifier with fat FET (Field-Effect-transistor) for low flicker noise and current-mode operation of the mixer. The LO (Local Oscillator) signal for driving the mixer is supplied externally. The performance of the receiver is tested using on-wafer probing and an air test is performed by integrating a microstrip antenna. The total conversion gain, noise figure, and 3 dB bandwidth are 28 dB, 6.1 dB, and 6 GHz, respectively. The chip size is 0.320 mm². [ABSTRACT FROM AUTHOR]

To map the surrounding environment using a radar sensor, both radar detection results and robot’s motion information are required. In general, an additional inertial sensor is required to acquire motion information of the robot. In this study, a method for estimating a robot’s ego position from radar detection results without the aid of other sensors is developed. First, the absolute positions of the detected targets are determined by comparing the radar detection results in two consecutive frames. Next, the position of the robot in the new frame is estimated based on the positions of the identified targets. Finally, the position of the robot obtained from the inertial sensor is compared with the position estimated by the proposed method, and the average position estimation error is found to be less than 0.33 m [ABSTRACT FROM AUTHOR]

To develop missiles to intercept short and medium-range rockets, the effectiveness of the air-to-air radar detector should be analyzed. In this study, to analyze the performance of a Ku- and Ka-band-based detector, we model the monopulse radar system, radar echo, and trajectories of the missile and rocket and perform numerical analysis for the radar cross section (RCS) of a computer aided design (CAD) model that is constructed based on an actual rocket. In addition, both the Swerling model and the analyzed RCS are considered in simulation to analyze the effect of the beam width of the monopulse radar and the power of received signals. As a result of the simulation, the Ka-band radar tracked the target relatively accurately in the presence of multiple targets, whereas the Ku-band radar had a higher probability of detection for low-RCS targets. [ABSTRACT FROM AUTHOR]

In this paper, we propose a classification method of pulsed radar signal attributes by applying machine learning to a convolutional neural network and a long short-term memory(CNN-LSTM) network when the radio frequency and pulse repetition interval of the signal changes with a long period. CNN has a function to extract data features, and LSTM shows good classification performance when sequential data are highly correlated. However, LSTM has a problem that performance is degraded when the length of the input data is long. In the proposed method, CNN is applied to extract compressed features from long-period data to reduce the length of inputs to LSTM. In simulation results, the proposed method shows more than 95% correct classification rate when the data drop rate is 10% for 182,516 total radar signal attribute combinations. [ABSTRACT FROM AUTHOR]

Ultra-wideband (UWB) technology appeared as a short-range wireless communication technology 20 years ago, but competing technologies, such as Wi-Fi, attracted more interest. However, UWB technology has recently been re-evaluated because it makes it possible to measure the distance between wireless devices. In particular, UWB chips were released by NXP and Qorvo, and, as Samsung and Apple began installing UWB technology in smartphones, it began to be popularized. It is expected that UWB technology will be used in connection with smartphones in various location-based fields, such as automobiles, smart factories, and smart homes. Although the importance of UWB technology is increasing in various fields, as described above, the research on the principles and characteristics of the latest UWB positioning technology has been inadequate. Therefore, to help readers systematically understand the latest UWB positioning technology, the principle of UWB positioning technology is explained, and the latest research and development, as well as commercialization trends, are described. [ABSTRACT FROM AUTHOR]

In this study, separate search areas are set in the threat area to maximize the operational efficiency of the multi-function radar, and a search operation method for multi-search areas according to their importance, is proposed. In particular, to satisfy the frame time required to fulfill the maximum detection range for each search area, a search ratio calculation method using the search times of each area is proposed. In addition, to satisfy the search ratio, a search operation method is proposed that can meet the requirements for multi- search areas by switching the search area based on the threshold for the search time, for each area. In this study, two search areas with different search waveforms were set, and the achievement of the requirement was mathematically verified. In addition, the suitability of the proposed method was confirmed through performance analysis under various simulation conditions. [ABSTRACT FROM AUTHOR]

This paper presents a high-efficiency power amplifier based on a harmonic control matching network. We proposed a harmonic control matching network based on a Chebyshev filter that can match the load to the optimum power matching impedance at fundamental and harmonic frequencies as well as block harmonic signals. The power amplifier applied to the proposed harmonic control matching network has high efficiency and excellent harmonic suppression performance without an additional low-pass filter. The fabrication and measurements were conducted to verify the proposed circuit. The implemented power amplifier achieved 61.3～76.3% drain efficiency in the frequency band of 2.8～3.2 GHz, and it was shown that a second harmonic suppression of under −46 dBc was achieved. [ABSTRACT FROM AUTHOR]

In this study, the feature attributes from a received pulse radar signal are defined and certain methods are proposed to classify the attributes using machine learning. The classifier is composed of a long short-term memory (LSTM) network and a fully-connected neural network. As inputs to the LSTM network, pulse repetition interval and radio frequency are used among the pulse description words. The outputs of the classifier can be organized into three types of attributes, i.e., the change pattern of the pulse repetition interval and radio frequency, the number of steps in a period, and the number of pulses in a step. Two classifier structures, single-input and multiple-input, are proposed according to the number of input types. The number of classes varies depending on the classifier structure and the multiple-input classifier classifies 22,410 radar signal attribute sets. The missing pulses, the introduction of any non-desired pulses and an error in measuring the pulse features are considered as the non-ideal characteristics of the pulse train. The simulation results show that the proposed method shows a high classification accuracy despite the large number of classification options. [ABSTRACT FROM AUTHOR]

The non-contact vital sign detection of an individual in indoor environments using a radar sensor has been widely researched by recent advances in the IoT industry. Most of these studies have been conducted by analyzing the spectrum of extracted phase variations in the echo signal of a motionless individual that has only micro-motion (that is, vital signs) caused by both the lung and the heart. However, in the case of a walking individual, the performance of the vital sign detection using conventional methods may be rapidly degraded owing to extreme phase fluctuations caused by the relatively large movement of the individual compared to the vital sign motions. To address this problem, we propose a new motion compensation method for the vital sign detection of a walking individual. First, we conduct a modeling of the echo signal for a walking individual using a radar and discuss problems in vital sign detection. Next, a new algorithm for real-time motion compensation is suggested based on a moving averaging filter and mode in statistics. In the experiments using an IR-UWB (Impulse-radio ultra-wideband) radar, we observed that the proposed method performed a successful real-time vital sign detection of a walking individual. [ABSTRACT FROM AUTHOR]

Photonics-based radar system is designed and fabricated for X-band frequency-modulated continuous-wave (FMCW) radar with optical devices, and it is demonstrated by conducting system integration and far-field tests. The photonics-based radar system generates broadband linear frequency-modulated (LFM) signals with a bandwidth that is 20% of the X-band of the center frequency for high-resolution inverse synthetic-aperture radar (ISAR) images by using an electro-optical modulator. It directly processes broadband target signals with photonics devices. To perform a field test using the proposed photonics-based radar transceiver system, the output powers for the long-range and short-range modes were designed to be 7 W and 100 mW, respectively. The far-field test confirmed a detection range of the simulated target with a 10-m² radar cross section (RCS). A drone ISAR image with a 7.5-cm high-range resolution is achieved by applying broadband LFM signals with a bandwidth that was 20 % of the X-band. The result of this study can enhance the ability to design photonics-based radar systems and assist the development of FMCW radar for detection, tracking, and ISAR images. [ABSTRACT FROM AUTHOR]

This paper presents the calculation of the radar cross-section (RCS) of an arbitrary scatterer with a perfect electric conductor by using the incremental theory of diffraction (ITD), a high-frequency technique. The reflected field at the surface of the scatterer is calculated using conventional shooting and bouncing rays (SBR), and the diffracted field at the edge is calculated using the ITD. The proposed method is verified by calculating the monostatic and bistatic RCS of a scatterer composed of two cubes of different sizes and comparing it with the simulation results from CST Microwave Studio. Furthermore, it is demonstrated by calculating the bistatic RCS for a simplified ship that the divergence problem in the physical theory of diffraction can be solved using the proposed method. [ABSTRACT FROM AUTHOR]

This paper proposes a three-dimensional 24 GHz frequency modulated continuous-wave (FMCW) radar transmitter for long-range detection. The proposed transmitter implements seven switched vertical fan beams from 15° to −15° for high effective isotropic radiated power (EIRP) and vertical angle detection. Instead of using lossy electronic switches and large passive beamforming networks, the beamforming transmitter is achieved by directly switching the power amplifier, which drives a sectoral series patch array antenna. The EIRP of each beam is approximately 48.676 dBm, and the size of the transmitter is 27.5 cm × 11 cm. [ABSTRACT FROM AUTHOR]

An eight-channel transmit/receive module (TRM) was designed for a wideband electronic warfare multiple threat jamming transceiver. In the system, the TRM amplifies a multijamming signal from a multibeam transceiver module and a small radio frequency (RF) signal from an antenna. In TX mode, it has an output power of more than 43 dBm for a continuous wave. In RX mode, it has a gain of more than 10 dB and noise figure of less than 5 dB. The voltage standing wave ratio is less than 2:1, and the TX and RX path isolation is 50 dBc or more. The RF signal amplitude and phase variation are less than 2 dB and 10°, respectively. True time delay and a digital attenuator are used to compensate for the signal amplitude and phase for each channel. [ABSTRACT FROM AUTHOR]

In this study, the design of a low-cost frequency-modulated continuous wave (FMCW) radar system at C-band using commercial off-the-shelf (COTS) components is presented. The proposed radar system consists of low-cost surface-mounting devices and monolithic ICs on a multi-layer FR4 PCB for system integrity. The Tx/Rx antennas (Cantennas) were fabricated with commercial cans based on waveguide dominant mode analysis. The proposed radar system is connected to the Arduino UNO platform, which transfers the received analog backscattered RF signal to MATLAB to display a range versus time intensity (RTI) plot. The designed radar has a maximum detection range of 56.3 m. [ABSTRACT FROM AUTHOR]

Factors that contribute to varying radar performance include internal causes such as equipment obsolescence, and external causes such as terrain and atmosphere. In particular, the atmosphere, which is a natural element, causes inevitable performance changes. The refractive index changes with atmospheric conditions in real time and affects the propagation environment, which affects the radar performance. Depending on the refractive index, atmospheric conditions are divided into super, sub, standard, normal, and trap, and the radar performance changes, such as the maximum detection range, occur differently during each atmospheric state. Therefore, it is important to predict and respond to changes in radar performance depending on the atmospheric conditions. In this study, the changes in the maximum detection range at low altitudes and detection performance at a long distance are analyzed using the M&S tool with respect to the refractive index. As a result, the maximum detection range decreases for a larger refractive index and vice versa, while the detection performance at a long distance changes because of abnormal atmospheric conditions. [ABSTRACT FROM AUTHOR]

Here, we propose an X-band dual-loop patch array with improved mutual coupling and durability. To reduce the radiator size and improve the bandwidth characteristics, individual elements of the proposed array antenna employ a dual-loop patch antenna that includes an indirectly fed structure. The proposed antenna includes a via cavity structure, which is advantageous for improving the isolation char- acteristics durability. To verify the performance of the proposed antenna, the measurement results are compared to the simulation results using FEKO, CST, and HFSS. The subsequent results demonstrate that the proposed antenna operates in the X-band with a VSWR less than 3:1. We also examine the VSWR in the scan range (0°<θ< 90°, 0°<φ< 360°) of the 3 × 3 array antenna, which exhibits active VSWRs less than 3.7 in all scan directions. [ABSTRACT FROM AUTHOR]

High-resolution compact radar in high-speed aerial vehicles can be exposed to vibration, and vibration can degrade the phase noise of crystal oscillators and other RF circuits. In this study, a laboratory experiment was conducted similar to the actual operating environment using a coherent frequency synthesizer, superheterodyne receiver realized by commercial RF circuits, an optical delay line with a maximum 20 km range delay, and a vibrator. After applying vibration to the frequency synthesizer, the phase noise was measured at each node of the receiver using a signal source analyzer. Consequently, it was confirmed that the effect of the phase noise suppression function depends on the range delay. The suppression function not only degrades the phase noise by frequency multiplication, but also degrades it by vibration. On the other hand, it has been shown theoretically and experimentally that the lower limit can be suppressed by the suppression function is determined by the higher level of the phase noise generated from the oscillator to the intermediate frequency signal or thermal noise. Finally, a transceiver architecture that has the advantage of suppressing phase noise is proposed for compact radar using high-resolution waveforms. [ABSTRACT FROM AUTHOR]

To accurately simulate signals scattered by multiple targets and received by Doppler radar, target motion under aerodynamic forces has to be modeled. We present a new technique for computing aerodynamic forces acting on flying mines of remote anti-armor mine systems (RAAMS). This weapon system is particularly attractive for detailed analysis of multiple clustered sub-munition systems, owing to their simple shape and relatively small number. The generated positions and velocities of multiple mines are then used to generate the radar echo signal received by the Doppler radar. [ABSTRACT FROM AUTHOR]

In a radar system, a clustering algorithm is mainly used to group adjacent cells using CFAR algorithm results. However, in closely spaced airborne targets, it is difficult to divide the targets using common clustering methods. Therefore, this paper proposes a clustering method using a monopulse rather than increasing the range and Doppler resolution. Even with adjacent hits, if the monopulse value is more than a specified threshold, the results are not grouped into one cluster. [ABSTRACT FROM AUTHOR]

We present a ground clutter reflectivity calculation method and a signal generation model of the simulated sea/land clutters of airborne radars using real navigation and radar operation information. The navigation and radar operation information were obtained by loading airborne radar on aircraft. The real navigation information and real sea/land clutters were obtained in the sea and land regions, and sea/land clutter reflectivity values calculated using the presented method were compared with the values of sea/land clutter reflectivity models of earlier studies. We confirmed the validity of the proposed sea/land clutter generation model by comparing real and simulated sea/land clutters. [ABSTRACT FROM AUTHOR]

A beam pattern of a radar is measured at a specific facility such as an anechoic chamber, and it is difficult and expensive to move a physically large radar from an operating environment to the facility. If a radar can measure beam pattern characteristics with landmark or celestial bodies in an operating environment, it can provide a cost effective maintenance. Sun is a celestial body which exists in an operating environment, and sun noise is easy to monitor automatically. However, interferences interfere with the automatic detection of noise. Therefore, in this study, we implemented and tested an automatic sun noise monitoring method and an effective interference suppression method in a radar operating environment. [ABSTRACT FROM AUTHOR]

Recent advance in low cost and light-weight drones has extended their application areas in both military and private sectors. Accordingly surveillance program against unfriendly drones has become an important issue. Drone detection and classification technique has long been emphasized in order to prevent attacks or accidents by commercial drones in urban areas. Most commercial drones have small sizes and low reflection and hence typical sensors that use acoustic, infrared, or radar signals exhibit limited performances. Recently, artificial intelligence algorithm has been actively exploited to enhance radar image identification performance. In this paper, we adopt machined learning algorithm for high resolution radar imaging in drone detection and classification applications. For this purpose, simulation is carried out against commercial drone models and compared with experimental data obtained through high resolution radar field test. [ABSTRACT FROM AUTHOR]

Digital adaptive beamforming is applied to the radar system to ensure system performance in an interference environment. For real time application to an actual radar system with a large number of antenna elements, the dimensions of the adaptive beamforming coefficient must be reduced. In this paper, we propose a beam domain localized adaptive beam forming algorithm based on linear constrained minimum variance (LCMV) that considers system applicability while maintaining the performance of fully adaptive beamforming. Jammer detection and angle estimation are performed using a passive listening signal, and the dimensions are reduced by localizing the signal to the beam domain based on jammer information and pre-determined linear constraints. Estimation of the interference covariance matrix and adaptive beamforming are performed in the reduced beam domain to ensure real-time operation and applicability. To verify the performance of the proposed algorithm, we analyzed the results compared to the fully adaptive beamforming in terms of signal-to-interference plus noise ratio (SINR) loss and maximum side lobe level in the presence of a jamming signal. [ABSTRACT FROM AUTHOR]

In radar operations, the detection performance is reduced owing to various external factors. These factors include interference and other targets, as well as losses from the atmosphere and terrain. Because of its geomorphic characteristics, radar operating in Korea is affected by interference, and its performance is degraded. This paper describes the simulation of the environment of near-radar interference and multiple targets. The modeling and simulation (M&S) tool was developed to predict and prevent the degradation in radar performance in advance. We validated existing constant false alarm rate (CFAR) detection algorithms by generating signals through the M&S tool and proposed a new CFAR algorithm to enhance the radar performance. Consequently, radar performance is enhanced by the new CFAR algorithm in radar interference and multiple target environments. [ABSTRACT FROM AUTHOR]

Ship can be placed in various sea condition during missions and is fluctuated by wave according to sea condition and the fluctuation get bigger as the sea condition gets worse. This not only reduces the radar performance but also limits the required operational capability. Therefore, unlike in the case of ground-based radar, the beam of radar operated in the naval vessel must be compensated according to ship motion. For a multi-function radar, the beam is compensated according to the attitude of the ship by electronic beam steering. Electronic beam steering would result in losses; however, if it is not employed, the target may be missed. The radar should be designed considering the margins by analyzing these phenomena in advance. Therefore, in this study, the modeling and simulation (M&S) tool was used to simulate ship motions according to various sea states and to analyze the variation in radar performance. Consequently, it was verified that the variation in radar performance increased as the sea state intensified. [ABSTRACT FROM AUTHOR]

During radar operation, changes in the radar cross section (RCS) of a target have an adverse effect on the radar detection performance. In particular, the RCS of a target with high maneuvering characteristics can be changed rapidly. Therefore, a precise prediction of the RCS change is essential for satisfactory radar detection performance. In this study, a modeling and simulation (M&S) tool was developed for the estimation of radar detection performance. The M&S tool comprises a radar model, target model, and wave propagation model. In particular, pre-obtained RCS simulation data were utilized to consider the effect of the RCS change of the target. Using the developed tool, the RCS based on the relative attitude is extracted from the RCS simulation data and the RCS processed data using the moving average method. The M&S model is verified by comparing the two test results with the radar received signal power. Consequently, we verified that when using the RCS manufacturing data, the signal power is more similar to the test data than the other RCS simulation methods. It is expected that the radar performance on the high-maneuvering target can be estimated using the developed M&S tool. [ABSTRACT FROM AUTHOR]

In this paper, we propose a widerange array microphone for lecturer tracked with Frequency Modulated Continuous Waveform (FMCW) radar sensor. Time Difference-of-Arrival (TDoA) is often used as audio tracking, but the tracking accuracy is poor because the frequency of the voice is low and the relative frequency change is large. FMCW radar has a simple structure and is used to detect obstacles for vehicles, and the resolution can be archived to several centimeter. It is shown that the sensor is useful for detecting a speaker in open area such as a lecture, and we propose an wide range 4-element array microphone beamforming system. Through some experiments, the proposed system is able to adequately track the location and showed a 8.6dB improvement over the selection of the best microphone. [ABSTRACT FROM AUTHOR]

In this paper, a compensation scheme of frequency selective IQ mismatch for high-performance radar systems based on commercial RFIC’s is proposed. Besides, an optimization model and its solution based on the dimension reduction scheme using singular value decomposition are also proposed to design the optimal IQ mismatch compensation digital filter with complex coefficients. The performance of the proposed method had been analyzed through experiments using the IQ mismatch measurement and compensation system implemented on an FPGA board with a target RFIC and compared with the previous method. The experiment result showed a performance improvement of the proposed method over the existing one without noticeable increments in complexities. These performance analysis results showed that the limitation of using commercial RFIC’s in high-performance radar systems due to the undesirable maximum SNR cap caused by their IQ mismatches could be overcome by employing the proposed method. [ABSTRACT FROM AUTHOR]

Accurately measuring elevation angles of sea-skimming targets via monopulse processing is difficult owing to the multipath signals of sea surfaces. For tracking and shooting down sea-skimming anti-ship missiles, this study presents a fine measurement method for elevation angles of targets under constrained conditions in terms of antenna beam widths of the close-in weapon system (CIWS) radar. This method is based on Eckersten’s implementation of the “complex angle”. We design a specific application and extension of Eckersten’s method, based on its limitations and scope for improvement, to the CIWS radar for estimating elevation angles of sea-skimming targets accurately and effectively. We also evaluate the performance of the proposed method through simulations under various antenna beam widths and transmission frequencies. [ABSTRACT FROM AUTHOR]

The design results of the polyphase codes used as noise radar waveforms are presented. The simulated annealing algorithm is applied to minimize the objective function, which is defined as the sidelobe level of the auto-correlation function of each polyphase code. Optimal codes are designed in a short computation time in the case of several code lengths and phase distinct numbers, and their relationship to the sidelobe level is analyzed. In particular, even if the code length is greater than 10,000, optimal codes can be obtained. In addition, by applying the characteristics of the phase shift caused by the Doppler shift of the moving target to the definition of the objective function, we can design the polyphase codes where sidelobes do not increase significantly in spite of the Doppler phase shift. [ABSTRACT FROM AUTHOR]

The modern active electronically scanned array (AESA) airborne radar features an interleaved mode, whereby situational awareness can be maximized via incorporation of the radar's electronic beam pointing capability. This interleaved mode can enable simultaneous operation of two or more modes, such as the air-to-air and sea surface-search modes, via the technique of time-sharing. One of the key requirements for successful realization of the interleaved mode is a beam scheduler design that facilitates effective control of the allocated resources for each mode. Thus, in this paper, we propose an effective beam scheduler that can control the allocated resources for each mode through the mode-switching option based on the radar's frames, bars, and beams. Furthermore, the proposed beam scheduler involves the mode-switching decision logic and calculates the processing ratio for each mode. [ABSTRACT FROM AUTHOR]

In this paper, Ultra Wide-Band(UWB) radar sensor is employed to detect flying drones and avoid collision in dense clutter environments. UWB signal is preferred when high resolution range measurement is required for moving targets. However, the time varying motion of flying drones may increase clutter noises in return signals and deteriorates the target detection performance, which lead to the performance degradation of anti-collision radars. We adopt a dynamic clutter suppression algorithm to estimate the time-varying distances to the moving drones with enhanced accuracy. A modified Constant False Alarm Rate(CFAR) is developed using an adaptive filter algorithm to suppress clutter while the false detection performance is well maintained. For this purpose, a velocity dependent CFAR algorithm is implemented to eliminate the clutter noise against dynamic target motions. Experiments are performed against flying drones having arbitrary trajectories to verify the performance improvement. [ABSTRACT FROM AUTHOR]

An active electronically scanned array radar is able to radiate the search beam and track beam more independently than a mechanically scanned array radar. However, as the scan angle increases, the detection performance degrades; as a result, the track-on target could be lost due to scan loss. To overcome the degradation of the tracking performance for off-boresight targets, the effective track-beam operation strategy is proposed to compensate for the scan loss by increasing the dwell time. Because this strategy increases the frame time, which affects the detection performance of the radar system, the detection and track maintenance performance are analyzed systematically. [ABSTRACT FROM AUTHOR]

Despite increasing threats from hostile drones, the conventional active radar system remains inappropriate for urban surveillance purposes. The digital video broadcasting-terrestrial (DVB-T) signal exhibits a wide bandwidth and high transmit power compared with FM or WiFi signals, and hence enables the design of simple, low-cost passive radar with wide coverage areas. In this paper, a DVB-T system is employed to construct a passive radar surveillance system, and its performance is assessed experimentally in terms of detecting airplanes and small drones. For this purpose, a simple passive radar is implemented using high-gain antennas and low-cost RF receivers. After the DVB-T signals received through passive channels are processed, target-detection scenarios are carried out for flying airplanes and drones. [ABSTRACT FROM AUTHOR]

This paper proposes a design for a photonics-based radar system for high-resolution inverse synthetic-aperture radar (ISAR) images. The proposed radar system can derive broadband characteristics using optical elements, such as phase modulator, laser source, and dual parallel Mach-Zehnder modulator (DPMZM). The detection performance and ISAR images for the target are observed according to the bandwidth of the radar system using modeling and simulation (M&S) for the proposed radar system. To verify the effectiveness of the bandwidth of the radar system, the proposed radar system are fabricated, and its performances are measured using a small drone in a practical environment. The results prove that the proposed FMCW radar system is a suitable candidate to overcome the limitations of bandwidth and high resolution. [ABSTRACT FROM AUTHOR]

In this paper, to analyze the dispersive characteristics of plasma, a dispersive model suitable for the finite-difference time-domain (FDTD) method is proposed. The dispersive characteristics of plasma with varying electrical properties according to frequency were accurately and efficiently expressed using the modified Lorentz dispersive model. The coefficient of the modified Lorentz dispersive model was extracted by applying complex curve fitting based on the weighted least squares method. The method of applying the modified Lorentz dispersion model to the FDTD is discussed. The plasma model based on the modified Lorentz dispersion model proposed in this paper was verified to match the data of the dielectric barrier discharge (DBD) plasma generator from dielectric slab equivalent modeling. The accuracy of the proposed FDTD algorithm based on the modified Lorentz dispersive model was verified by comparison with the results of the broadband radar cross-section (RCS) measurement experiment. [ABSTRACT FROM AUTHOR]

A method to improve the tracking accuracy of low-altitude sea targets is proposed using an adaptive beamforming algorithm in a multipath environment. It is confirmed that the target elevation can be estimated with relatively high accuracy without repetitive calculation using the proposed method in analog beamforming active electronically scanned array radar. The proposed method improves the tracking accuracy by adding a side-lobe suppression condition to the existing adaptive beamforming constraint for mono pulse inclination control while accounting for the characteristics of the low-altitude sea target with less elevation change. In addition, various adaptive beamforming algorithms were applied to the proposed method, and the results were compared and analyzed to optimize tracking accuracy. [ABSTRACT FROM AUTHOR]

The results of the fabrication of active electronically scanned array (AESA) antennas with low-profile, low-weight, wide-scan, and thermal stability characteristics for aircraft-mounted radar are described. To reduce the size and weight of the antenna, a transmit– receive block is constructed in a quasi-tile structure in which the radio-frequency circuit-related transmit–receive module is a brick type, which is a flat structure, and the control board is a tile type, which is a stacked structure, to reduce the depth of the front of the antenna. In addition, the depth of the rear part of the antenna was reduced by manufacturing power and plate-shaped control-related modules at the rear of the antenna. The reduced antenna depth maximizes the effective isotropic radiated power (EIRP) and gain to noise temperature (G/T) by enlarging the antenna aperture. The manufactured antenna can scan a wide angle of ±70°. The cooling efficiency is improved by using a dual cooling structure that allows the cooling water to pass through the front cooling plate and then through the rear cooling plate. The EIRP of the manufactured AESA antenna is 104.04 dBmi, and G/T is 7.46 dB/K in Taylor weighting. [ABSTRACT FROM AUTHOR]

In this study, a tapered slot antenna with a band-stop characteristic in the Ka-band is proposed and measured. A 4-layer liquid crystal polymer substrate with a thickness of 150 μm was used to implement the same substrate as a radar transmit-receive module. To stop the 28 GHz band used for 5G communication, a split ring resonator structure is added to the feed line and corrugations are formed on both sides of the antenna. Through these structures, the proposed antenna has a 28 GHz band-stop with a measured 1.8 dB return loss. In addition, the front-back ratio increases from 14.0 dB to 21.1 dB for the simulated results, and the measured radiation gain is 11.6 dBi. [ABSTRACT FROM AUTHOR]

A periodic aperture array structure combined with a lossy ground conducting layer was analyzed using the method of moments and was shown to produce near-perfect absorption. Rectangular aperture and rectangular loop aperture geometries were considered as exam- ples of a unit cell of aperture. The numerical results for the reflection coefficient for the case where the unit cell of the aperture was rectangular were compared with those obtained by using commercially available software, such as HFSS and CST MWS, to validate the analysis method. A method for solving the scattering problem using a planar lossy conductor was also considered. The accuracy of the solution provided by this method was better than or comparable to that of the commercially available software for an arbitrary thick conductor. In particular, the present structure composed of a combination of lossless FSS and lossy ground was observed to be useful in comparison with the previous structure composed of a combination of lossy FSS and perfect conducting ground from the view- point of the thickness minimization of the radar absorbing material in the case of a rectangular loop aperture. Notably, the present structure is the same as the basic architecture of photovoltaic devices. [ABSTRACT FROM AUTHOR]

An 3D radar system can detect the distance, azimuth, and altitude of targets. The radar acquires target information using an electronic or mechanically steered narrow antenna pattern. It calculates the target altitude using the detected information. In addition, angular accuracy is improved by applying various methods such as monopulse. The radar angular accuracy is affected by external factors such as multipath effects that are caused by various factors such as the radar installation environment and the flight altitude of the target. Radar systems apply various methods to improve the detection accuracy degradation caused by multipath effects. The squinted sum monopulse method can reduce the detection errors of the radar in a marine environment with a high frequency of multipath effects. The radar utilizes a different monopulse pattern that calculates an angular error with a sum pattern steered upwards of the detection beam. This is a method of minimizing the influence of the multipath received signal incident downward through a difference pattern in which the gain falls sharply below the detection beam. In this study, the effect of the squinted sum monopulse method was verified through simulation, and the effect was confirmed by applying it to an early warning radar installed in a sea environment condition. [ABSTRACT FROM AUTHOR]

The Ku-band (12～18 GHz) is mainly used for long-range satellite communications and radar applications. Because the signal power is weak in a long-range communication, it is important to reduce the loss of the transmitter and receiver. In this paper, we propose a low-loss compact 4×4 Butler matrix structure that operates in the range of 15.7～16.7 GHz. To achieve low-loss characteristics, a low-loss transmission line was designed based on the suspended transmission line. To miniaturize the structure, the internal circuit of the Butler matrix was designed as a 100 Ω system, and the input/output stage was matched at 50 Ω. The size of the Butler matrix circuit manufactured through the optimized design was 45×22×2.3 mm. The insertion loss, isolation between terminals, and return loss of each terminal measured within the operating frequency band were 1.36 dB (including connector loss), 20.5 dB, and 15.3 dB, respectively, demonstrating a performance similar to that of the simulated performance. The proposed 4×4 Butler matrix can be utilized as a low-loss beam-switching circuit for a 1×4 linear array antenna. [ABSTRACT FROM AUTHOR]

Stereo cameras have been widely employed for object and range detection in vehicular advanced driver assistance systems. However, camera sensors generally suffer from a lack of accuracy in terms of range detection when targets are further away from the sensors. In this study we present a fusion system composed of a 77 GHz frequency modulated continuous wave (FMCW) radar and a stereo camera, in which range information obtained by the camera is corrected by the radar data, a technique named target matching algorithm. Alternatively, the radar fed by the vision data can be equipped with the direction of arrival information that is not feasible with a single-channel FMCW radar. The measurement shows that the proposed technique is valid and effective. [ABSTRACT FROM AUTHOR]

In this study, we propose a 77 GHz radar transceiver implemented on an FR-4 substrate driving a horn antenna. The self-developed CMOS transmitter and receiver chips with on-chip feeders are used as active components. Instead of conventional metal cavity packaging, three FR-4 substrates were stacked to form a cavity and aperture to drive the WR-10 horn antenna. Three-dimensional electromagnetic simulation for FR-4 packaging confirms that the insertion loss from the chip to the waveguide aperture was 1.62 dB and the return loss from the waveguide aperture was less than −10 dB from 75 to 80 GHz. With a horn antenna of 24 dBi gain, a medium-sized vehicle located 81 m in front was detected, and the measured SNR was 28 dB. The proposed radar transceiver consumes a total of 371 mW DC power, and its size is 50 mm×80 mm×4.2 mm. [ABSTRACT FROM AUTHOR]

Anti-ship missiles used for destroying warships are significantly influenced by sea clutter. Accurate sea clutter information can be obtained from data that vary with variables, such as sea temperature, wave height, wind direction, and wind speed. In this study, we obtained the sea clutter radar cross-section (RCS) for a ship using a radar mounted on a high-level anti-ship missile for various flight techniques. The radar equation was used to analyze the effect of the surface clutter RCS on the signal received by the anti-ship missile radar antenna. [ABSTRACT FROM AUTHOR]

In search radar systems, one face of the antenna generally rotates. By contrast, multi-function radar systems operate with four faces in a fixed position. Four-face multi-function radar is operated independently and has the advantage of being able to operate a beam simultaneously using a phased array antenna. However, there are disadvantages in terms of interference between the faces during beam transmission. A search beam can avoid such interference by concurrently sending another beam that is not for tracking owing to differences in their waveforms and transmission times according to the target location and type. In this study, to overcome such disadvantages, we developed a resource management model that applies the concept of tracking synchronization for a simultaneous four-face operation. We analyzed the results of resource changes in the target #1,000 scenario using a resource management model we developed through a modeling and simulation (M&S) tool. As a result, the new resource management system operates the time resources efficiently and improves the radar performance. [ABSTRACT FROM AUTHOR]

Spectrum sensing, which is used for identifying the temporarily unoccupied frequency band by a primary user, is an essential component of the cognitive radio system. Various spectrum sensing techniques have been developed, and they are based on distinguishing features of a primary user signal. Thus, it is desirable to exploit additional characteristics to attain a higher spectrum sensing performance. Motivated by this purpose, for spectrum sensing in radar bands, we present a novel spectrum sensing approach in which multiple spectrum sensing methods are combined using a DNN. The considered spectrum sensing techniques include the energy detection, maximum-minimum eigenvalue ratio-based method, autocorrelation-based method, and generalized likelihood ratio-based method. Computer simulations demonstrate that the performance of the proposed scheme outperforms those of existing spectrum sensing methods. simulation demonstrates that the performance of the proposed scheme outperforms those of the existing spectrum sensing methods. [ABSTRACT FROM AUTHOR]

This paper proposes a signal processing technique that recognizes hand motions using a 60-GHz frequency-modulated continuouswave radar system. In the case of hand motion recognition with a radar, the recognition accuracy decreases owing to a clutter signal generated by the upper body and differences between the hand sizes of different people. To solve this problem, this paper proposes a moving target indicator filter with a weighted frequency for each frequency, which improves hand motion recognition accuracy, removes self-interference clutter signals, and uses a range profile and Doppler profile. Neural networks can recognize hand movements; hence, the proposed five hand gesture recognition techniques exhibited an 87.3% accuracy, regardless of the user. [ABSTRACT FROM AUTHOR]