Search

This paper presents an S-band power amplifier (PA) operating in the 2.9~3.2 GHz range for 2nd harmonic-based target detection radar. The input and output matching networks utilize transmission lines and λ/4 open stubs at 2nd harmonic frequencies to effectively match the load impedance to the optimal power matching contours at fundamental frequencies while achieving high 2nd harmonic suppression characteristics. This design achieves these goals without simultaneously introducing additional insertion losses at the input and output. Single measurements of the fabricated PA demonstrate a maximum saturated power exceeding 40 dBm, power gain ranging from 11.6 to 13.3 dB, and 2nd harmonic suppression level of 58.6 dBc or better across the 2.9~3.2 GHz range. When employed as a driver amplifier in the transmitter system, the PA exhibits a 2nd harmonic suppression level of 60 dBc or better within the 3.0~3.2 GHz range, affirming its suitability for 2nd harmonic-based target detection radar applications. [ABSTRACT FROM AUTHOR]

This study presents the design of a beam-splitting antenna using a magic-T feeding structure for wave detection radar systems. The proposed antenna demonstrates a technique for forming three different beams feeding at the three ports using a single-layer substrate. The strong coupling that occurs between the three ports is owing to the use of a single-layer substrate. An optimal arrangement of the slot lines located on the ground plane was designed to address this issue, achieving excellent isolation with values below -20 dB. The measured reflection and isolation coefficients agreed well with the simulation results, achieving reasonable results below -20 dB. The three expected beam pattern types were implemented, and the measured beam characteristics matched well with the simulated patterns. The two beams fed by port 1 exhibited a peak gain of 10.90 dBi, whereas the four beams fed by port 2 exhibited approximately 6.11 dBi. The single beam fed by port 3 exhibited a peak gain of 11.04 dBi. [ABSTRACT FROM AUTHOR]

Over-the-horizon (OTH) radar is a technology that propagates radar signals beyond the Earth's curvature along the horizon to detect and track a wide range of distant targets. This technology is crucial in addressing potential threats from neighboring countries; however, it has not been implemented domestically for practical use. The OTH radar system utilizes high frequencies (3∼30 MHz) to detect distant targets, resulting in a limited bandwidth and, consequently, reduced range resolution. To overcome these limitations, this study focused on enhancing the range resolution of narrow-bandwidth transmission pulse waveforms by constructing a hybrid least-squares reception filter. This filter combines the outputs processed using matched filters and the least-squares method to effectively maintain a high resolution while controlling noise. Finally, simulation results confirmed the improvement in the range resolution of the OTH radar through the application of this hybrid reception filter. [ABSTRACT FROM AUTHOR]

In this paper, we propose a radar module that can be applied to an X-band active phased-array radar. The radar module, with hardware scalability and software flexibility, is a basic block that can be freely configured according to system requirements. It generates radar waveforms using a digital-to-analog converter, frequency up-down conversion/amplification, baseband I/Q generation through an analog-to-digital converter or digital down converter, primary digital beamforming, and pre-signal processing functions. Because it has the same electrical performance and function, it has advantages such as reducing the development period, reducing the development budget, and improving maintenance and serviceability. This paper presents the radar module design and fabrication/test results applicable to X-band active phased-array radars. The hardware scalability and software flexibility of the proposed design were verified through a near-field test of a 3×3 array antenna. [ABSTRACT FROM AUTHOR]

This paper proposes a design method for a four-port phase-controlled antenna for wave detection radar systems for preventing coastal erosion and accidents caused by rip current waves. The proposed antenna is a new phase-control technology that implements the magic-T circuit structure, enabling the adjustment of the beam patterns and phases of the patch antenna based on the position of the feeding ports. Utilizing the phase control and high isolation characteristics of the magic-T circuit structure, we designed 2×4 patch array antennas with four ports. The proposed antenna achieved excellent design results with reflection coefficients and isolation between each port measuring below −20 and −30 dB, respectively. Based on phase control using the magic-T circuit structure, the study confirmed that the antenna exhibited excellent characteristics, radiating beam patterns ranging from one to four beams depending on the excitation to each port. Key words: Magic-T Circuit Structure, Patch Antenna, Wave Detection Radar, Phase Control, High Isolation. [ABSTRACT FROM AUTHOR]

This paper describes a 79 GHz frequency modulated continuous wave (FMCW) radar system with a sparse array to achieve high angular resolution with fewer Rx channels. The system consisted of one Tx channel and eight Rx channels placed in a nonlinear sparse array. The 79 GHz Tx and Rx chips were designed using a 65 nm CMOS process, and the measured transmission power was 10.93 dBm, conversion gain of the Rx was 30.1 dB, and noise figure is ∼13 dB at a 1 MHz IF signal. The Rx antenna array consisted of a 1×8 array of azimuth directions and a microstrip patch antenna with a simulation gain of ∼16.5 dBi was designed for the Tx and Rx antennas. The chirp time of the system is 100 μs, and the data was given a gain of 20 dB on the baseband board with filtering and sampled at a rate of 5 MSPS with an eight-channel 12-bit ADC. The corresponding ADC data were acquired by the FPGA, and the target distance and angle information were obtained based on the FFT. Subsequently, the distance and angle estimation of the target and angle resolution of the system were verified through measurements. [ABSTRACT FROM AUTHOR]

This paper presents the design and analysis of an LO chain implemented using the CMOS 65 nm bulk process. The LO chain was fabricated for driving the short-range radar IQ mixer in the 77∼81 GHz band. The LO chain comprised a poly phase filter (PPF), driver amplifiers to compensate for PPF losses, and a 3-bit 7-dB attenuator to ensure the appropriate power conditions. Measurement results indicated that the maximum gain within the target band was 8 dB, and the gain and phase difference between the IQ outputs were 0.5 dB and 74°, respectively. The LO chain consumed 74 mW of power at 1 V, and the size of the fabricated chip was 1.027×0.45 mm², including RF and DC pads. [ABSTRACT FROM AUTHOR]

In this study, a fixed-point-based beamforming coefficient calculator is proposed for the beamforming of a digital active array radar. Floating-point-based calculations enable precise calculations but have the disadvantages of high computational complexity and latency. To complement this, the proposed fixed-point-based beamforming coefficient calculation had a high signal to quantization noise ratio (SQNR) of 51.35 dB and the beam steering angle error was between −0.05° and 0.05° when compared with those of the floating-point calculation; these satisfied the system requirements. The proposed fixed-point-based beamforming coefficient calculator was implemented on a Xilinx Kintex UltraScale FPGA. It could reduce 54.94 % CLB register, 44.33 % CLB LUT, 60 % DSP slice, and −58.16 % latency than the floating-point calculator. Furthermore, at small beam pattern powers, the performance degradation of the calculator was less compared with previous research. [ABSTRACT FROM AUTHOR]

In radar, an extended target or structure is perceived as a collection of multiple point scatterers. For tracking radar, determining the weighted mean (or centroid) angle of these unresolved scatterers is crucial. Our study demonstrates that the monopulse angle estimate corresponds to the weighted circular mean of the angles of multiple scatterers, as supported by both analytical and simulation results. [ABSTRACT FROM AUTHOR]

This study proposes an effective method for detecting multiple targets in frequency-modulated interrupted continuous wave (FMICW) radar by using periodic signal characteristics and applying machine learning. FMICW radars are typically used for detecting a single target, but this method overcomes the challenges of range-Doppler coupling and spurious wave generation caused by the switching of transmit and receive signals, to detect multiple targets. The method first uses FMICW radar to generate an RD-Map by applying MLE (maximum likelihood estimation), and then enhances the targets by identifying the intersection of lines generated by range-Doppler coupling. Thus, by applying a machine-learning-based object detection algorithm to the enhanced images, multiple target detection be- comes possible. [ABSTRACT FROM AUTHOR]

Some monopulse radars on a ship require an altitude value of the radar relative to the sea level with error levels of several tens of centimeters (cm). In conventional methods, it is difficult to frequently measure the radar altitude relative to the sea level, which changes according to ship conditions, while maintaining error levels of several tens of centimeters. In this study, a monopulse radar irradiates a radar beam, measures the distance from the radar to the sea surface at the beam irradiation position, and presents a method for precisely measuring the radar altitude by considering the radar mounting error. The proposed method can be operated whenever necessary in a radar operating environment. We analyzed and verified the performance of the proposed method using simulations. [ABSTRACT FROM AUTHOR]

An inverse synthetic aperture radar (ISAR) is a radar system capable of forming high-resolution images regardless of weather conditions or light levels. The frequency-modulated continuous wave (FMCW) technique overcomes the system size limitations of pulse-based radars by significantly reducing the analog-to-digital conversion (ADC) sampling rate, consequently increasing the versatility of radar systems, leading to their widespread application in various fields. By separating the transmitter and receiver, bistatic radar can exploit the diverse scattering characteristics of targets and offers advantages such as improved resolution compared with monostatic radar. However, the operation of a bistatic FMCW radar must solve the problem of signal synchronization. This study presents the challenges of bistatic FMCW radar systems, proposes a master–slave structure to address synchronization issues, and demonstrates the formation of ISAR images in real-world scenarios. [ABSTRACT FROM AUTHOR]

The directionality and performance of radio waves are affected by the refractive index of the atmosphere, which varies in real time depending on the time and location. To reflect the domestic weather environment, we developed a radar modeling and simulation (M&S) analysis tool by constructing a refractive index generation model, APM, and radar model. We analyzed radar performance variations over the past five years using weather station data. For 220 nm-based radar designs, the performance variation ratios at 10 % above and below the design distance (i.e., 200 nm and 240 nm), were 0.78% and 1.45 %, respectively. The maximum detection range tended to increase in summer and then decrease in winter, with low standard deviations in both seasons. [ABSTRACT FROM AUTHOR]

Automotive radar can detect the distance, speed, and angle of a target from electromagnetic waves that are reflected back from a target on the road. During this time, the antenna radiates electromagnetic waves directly into the air. A radome, which physically protects the antenna from external environmental circumstances, is an essential part of the radar. Beam distortion analysis from the radome is very important during the radar development process when it is mounted on the radome. However, tier 1 suppliers mainly proceed with radome design by considering only the impedance of electromagnetic waves that are multiple-reflected in the normal direction. In this study, after modeling the thickness and spacing of the radome as design parameters, a radar platform simulation using a full-wave EM was performed with the thickness and spacing changed around the conventional design parameters. Therefore, the optimal design value of the radome for the multifunctional long-range radar under development can be obtained, and a database related to beam distortion characteristics has been constructed. Using these beam distortion analysis results, we proposed a method for the inverse design of the radome design parameters of the manufactured radar and an improved radar development method with a fast paces. [ABSTRACT FROM AUTHOR]

This paper presents the design results for a self-interference canceller (SIC) based on a symmetric delay-line radio frequency finite impulse response (RF-FIR) filter with a ladder structure. The proposed SIC effectively removes self-interference signals in the receiver caused by the low isolation of the circulator applied to the monostatic radar front end and the impedance mismatch of the antenna. Consequently, it enhances the isolation between the transmitter and receiver. The proposed filter consists of six taps with adjustable sizes and phases. The phase-delay values for each filter tap are implemented at a reference frequency of 3.1 GHz. The measurement results demonstrate that the proposed SIC achieves over 25 dB suppression of self-interference signals in the frequency range of 3.05 to 3.22 GHz. When applied to a monostatic radar transceiver with an RF circulator, it exhibits isolation strength of over 50 dB in the frequency range of 3.04 to 3.22 GHz. [ABSTRACT FROM AUTHOR]

This paper presents a low noise amplifier (LNA) for nonlinear radar applications combined with a composite right-handed and left-handed (CRLH) filter, a type of metamaterial. The proposed LNA consists of an input matching network, output matching network, and a CRLH filter combined. The LNA with a CRLH filter has advantages of broadband, low noise, and high frequency selectivity. It filters the harmonic frequency resulting in broadband operation and has a flat S-parameter value with a gain of more than 10 dBm in a wideband ranging from 4 GHz to 8 GHz. The noise figure value was measured at 1.521 dB and 1.682 dB at 4 GHz and 8 GHz, respectively, and 1.542 dB at 6 GHz, in middle frequency. [ABSTRACT FROM AUTHOR]

This paper discusses the design of a W-band down-conversion mixer, fabricated using a 65-nm bulk CMOS process. The mixer employs a passive double-balanced structure, resulting in no power consumption. It includes LC matching circuits for RF and LO input voltage amplification via resonance and RC filter circuits for precise IF signal separation. The manufactured mixer measured 0.614×0.25 mm², including RF and DC pads. Measurement results showed input return losses of more than 8 dB, a maximum conversion gain of －5.5 dB, and RF-IF isolation of 37.3 dB at 77–81 GHz. [ABSTRACT FROM AUTHOR]

In this study, we propose a two-step method to enhance pedestrian detection and driver safety in automotive radar systems. First, we assumed information regarding the range, velocity, and angle of pedestrians behind stationary vehicles using a frequency-modulated continuous wave radar system, with the cell-averaging constant false alarm rate algorithm employed to effectively distinguish between the target signals and noise components. Additionally, a multiple signal classification algorithm was used for the high-resolution angle estimation of the target. Subsequently, a long short-term memory network is applied to predict the movement of a pedestrian, with the results indicating an average error of 0.09 m between the predicted and actual points along the trajectory. [ABSTRACT FROM AUTHOR]

The interleaved mode has the effect of operating multiple modes simultaneously by operating two or more single modes in a time division using the agile beam steering capability of the AESA(active electronically scanned array) radar. During the air-to-ground/sea mode operation, the air-to-air mode is simultaneously operated for quick recognition and response to air threat targets. In this study, the processing unit was set differently according to the mode for an efficient interleaved mode. It is the design of the load-based beam operating algorithm that can maintain proper performance by designing to maintain a constant load. The resource usage of the proposed and existing algorithms was compared, and the flight test results were analyzed to verify the algorithm. [ABSTRACT FROM AUTHOR]

The spurious signals of the transmission signal (FTX) and local oscillation signal (FLO) for a receiver are the factors that reduce the SNR(signal-to-noise ratio) performance of a radar. In particular, a spurious signal with a high-power level causes the radar to falsely indicate a target. However, the spurious emissions of a frequency synthesizer are unavoidable because of the nonlinearity of the RF active elements on the FTX and FLO paths. In this study, spurious requirements are provided to ensure the SNR performance of a compact radar. Consequently, the spurious power level should be lower than −55 dBc to −28 dBc according to the offset frequency in the FMICW mode. In addition, it should be lower than −50 dBc to −40 dBc within a linear frequency modulation bandwidth (LFMM) in the MPRF mode, and the spurious that are out of the LFMM do not impact the signal processing results. [ABSTRACT FROM AUTHOR]

In this study, radar performance variations were analyzed using a modeling and simulation (M&S) model according to atmospheric conditions. The refractive index of each layer constituting the atmosphere was configured with different values depending on the time and place. Radio waves propagate differently depending on the refractive index and radar performance changes. Therefore, predicting and analyzing the radar performance reflecting the refractive index is crucial. An exponential model that reflects the domestic atmos- pheric environment and a measured data model using actual observed data (one year) was used to analyze the radar performance by reflecting atmospheric conditions. In addition, the variation in radar performance according to atmospheric conditions was analyzed using an advanced propagation model (APM), which analyzes the radio wave environment, radar, and target M&S models. As a result, the average and standard deviation of the maximum detection range were analyzed as about 227.30 NM (421 km), 3.64 NM (6.74 km) for the exponential model and about 220.31 NM (408 km), 8.99 NM (16.65 km) for the measured data model and the maximum detection range was analyzed longer in summer than in winter. [ABSTRACT FROM AUTHOR]

A static frequency-modulated continuous-wave (FMCW) radar imaging system uses different local oscillator (LO) and clock signals owing to the spatial separation of the transmitter and receiver, resulting in asynchronization problems of various factors that can deteriorate the quality of radar images. In this study, we defined signal models for bistatic FMCW asynchronization factors:1) the time difference between reference signals in the transmitter and receiver, 2) LO phase noise difference, 3) pulse repetition frequency mismatch, and 4) center frequency difference. We generated ISAR images of the point scatterer for each asynchronization factor to analyze the influence of asynchronization through the ISAR image in terms of quality parameters. [ABSTRACT FROM AUTHOR]

In this study, a 1 W W-band solid-state power amplifier (SSPA) was developed for application in a W-band compact pulse Doppler radar. The SSPA up-converted the X-band signal to a W-band signal with a multiplier (×8) and then amplified the high output using an amplifier. To apply the W-band compact radar, which transmits and receives signals using a single antenna, the SSPA noise was reduced by controlling the drain voltage of the SSPA according to the pulse repetition frequencies. The average power obtained was in the range of 31.7∼31.8 dBm, and stable operation was possible for more than 50 s. [ABSTRACT FROM AUTHOR]

Nonlinear detection is a technique that detects nonlinear interactions, such as harmonics and intermodulation, caused by semiconductor junctions, enabling the remote detection of nonlinear objects, such as small electronic devices with small radar cross-sections. The characteristics of such nonlinear radars enable the effective detection of targets equipped with small electronic devices in camouflaged and concealed environments, particularly in security and military applications. Therefore, this study constructs a nonlinear radar system utilizing FMCW to effectively detect the nonlinear response of small electronic devices at long distances. Using the constructed system, four small electronic devices, and manufactured nonlinear targets, successful detection was confirmed at a line-of-sight condition of 10 m, and even at a nonline-of-sight condition of 6 m. [ABSTRACT FROM AUTHOR]

Synthetic aperture radar (SAR) imaging is critical in military and national defense applications. Spaceborne SAR systems operate in fixed orbits, making them vulnerable to the jamming effects of ground radar signals. This study quantitatively analyzed jamming effects based on actual interference cases observed in the currently operational satellite SAR. Subsequently, various jamming scenarios were designed for hostile satellite SAR systems. SAR jamming simulations were conducted based on the ground radar specifications derived from real jamming cases by considering the jamming-to-clutter ratio (JCR) as a key metric for evaluating the jamming performance. The SAR image corruption was quantitatively analyzed for various ground jammers, with the results verified by comparison with real SAR jamming cases. This study attempted to understand the principles of satellite SAR jamming and contribute to the development of defense strategies against adversarial space surveillance systems in the near future. [ABSTRACT FROM AUTHOR]

his study proposes a 24 GHz FMCW radar system to detect the 3-dimensional location of a target. To determine the azimuth and elevation angles of a target, the proposed radar includes seven transmitters, illuminating seven elevation angles between −17.5° and 17.5° with a 5° resolution, and a receiver with a 2×4 array. Instead of using a conventional switch, beam steering is performed by directly switching the power amplifier of the transmitter. Experimental results show that the proposed radar system detects the location of the target with an RCS of −12.40 dBsm at a distance of 350 m with 20 dB SNR. [ABSTRACT FROM AUTHOR]

Simulating terrain clutter using a digital elevation model requires a long computational time, making it difficult to test and improve radar in a terrain-clutter simulation environment. This paper proposes a scheme for generating a received clutter signal after calculating in advance the distance and RCS of the terrain clutter according to the position and field of view of the radar. The beam-illuminated area was calculated using a digital elevation model of the radar conditions. The terrain clutter was modeled for the area where the beam was radiated. It was mapped to the radar field of view, and a scheme for generating the terrain clutter signal was developed. [ABSTRACT FROM AUTHOR]

A target-tracking method using the ground moving target indicator (GMTI) mode on active electronically scanned array (AESA) radar is proposed. The GMTI mode can operate in wide ground areas. However, the 3-dB beamwidth of the X-band radar is narrow, and a target is detected on multiple adjacent beams. To delete overlapping target plots, beam-to-beam processing considering a real-time system is proposed. In addition, a track while scan (TWS) multiple-target-tracking algorithm was constructed for the system. Through a flight test with true car mounted GPS, it was confirmed that the real-time processing ability and target-tracking performance of the GMTI algorithm were satisfactory. [ABSTRACT FROM AUTHOR]

This paper proposes a 32 GHz band radar receiver with an X8 multiplier. The Ka-band Rx chip used in the receiver was fabricated by using a 28-nm complimentary metal-oxide-semiconductor (CMOS) process and its built-in X8 multiplier enables the chip to driven by a low reference signal of 4 GHz. The designed Rx chip was attached to the ground plane of a microstrip patch antenna and connected to the feedline via the bonding wire. The impedance matching circuit was implemented along the antenna feedline by considering the impedance changes caused by the bonding wire. The reference input signal, intermediate frequency (IF) output, and bias of the receiver were supplied on an FR4 substrate with a cavity, which enabled easy implementation of the Ka-band receiver module without requiring expensive and precise packaging technology. The performance of the fabricated receiver module was verified in an over-the-air (OTA) test. [ABSTRACT FROM AUTHOR]

Low-altitude and high-speed targets that fly close to the sea level are generally detected using a single-band moving target indicator (MTI) technique. The MTI technique detects a moving target by filtering out the sea-clutter Doppler spectrum. However, when detecting a low-altitude, high-speed target flying close to the sea, blind speed problems can occur because of the fast maneuvering characteristics of the target. Moreover, multipath phenomena and false alarm may occur due to the influence of the sea. Such problems make detection difficult. In this paper, we propose a detector suitable for high-speed targets in sea conditions using dual-band radar. Low-altitude and high-speed targets were modeled by considering the maritime situation, and robust detection against blind speed and multipath phenomena was confirmed by applying the proposed technique to the average Doppler power of the received signal in each band. Finally, simulations for various speeds and distances of the target confirmed that the proposed method showed improved target detection performance than the existing single-band method when detecting low-altitude, high-speed targets in sea conditions. [ABSTRACT FROM AUTHOR]

Ship radar systems extract the distance, bearing, and altitude of a target and deliver three-dimensional tracking information to the combat system of the ship. In addition, high-resolution information about the target and B-Scope can be obtained using TWS (track while scan) tracking, and the information is used for naval gun firing. However, the normal B-scope is not formed if strong clutter signals from secondary reflection signals from the ground, coastal islands, or mountains are introduced during tracking. In such cases, it could be difficult to adjust the zero point and check the impact using the water column when firing the artillery. Therefore, in this study, a method is proposed to acquire a normal B-Scope by removing the secondary reflected signal, and the proposed method is verified by applying it to the actual Navy ships. [ABSTRACT FROM AUTHOR]

In this paper, we present a design and implementation method for a high-speed spectrum analyzer that can detect the spectrum of a received radar pulse signal in real time. To respond to an enemy's target search or tracking in an electronic warfare environment, it is first necessary to quickly detect the enemy radar signal. Signal search is mainly performed through spectrum analysis, and radar signals exist over a wide band of several tens of gigahertz (GHz). Therefore, signal detection is performed by dividing the entire band into several subbands and searching sequentially or in parallel. Because the search time can be reduced as the subband becomes wider, a searcher capable of processing the wideband in real time is required. In this paper, we design a digital searcher capable of detecting radar pulse signals within a 1 GHz bandwidth in real time and present a hardware implementation method. The requirements for real-time spectrum search for the hardware used are also presented. In the proposed method, the received signal is converted to digital through a high-speed analog-to-digital converter, and the spectrum of the signal can be searched in real time by performing an FFT that reflects the characteristics of the pulse signal. The spectrum analyzer was implemented on a Xilinx RFSoC board and its performance was examined. [ABSTRACT FROM AUTHOR]

Technology for classifying low probability of intercept (LPI) radar signals with speed and accuracy is critical for cognitive communication research. We used time-frequency analysis (TFA) and deep learning to classify 12 typical LPI radar signals. Traditional methods use the Choi-Williams distribution (CWD), which requires more than 500 times longer TFA generation time than the spectrogram method. In this paper, we show the trade-off relationship between classification accuracy and detection time using a spectrogram, Wigner - Ville distribution (WVD), and CWD as the training datasets. As a result, the CWD model showed higher accuracy than the spectrogram model, but the prediction time was more than 200 times longer. The accuracy difference was only 1 %p for an SNR over - 2 dB, but it reached 7.5%p for an SNR of - 10 dB. Therefore, a lower SNR shows a distinct trade-off between prediction time and accuracy, depending on the type of TFA. [ABSTRACT FROM AUTHOR]

This paper describes a 94 GHz FMCW radar system for unmanned vehicles using 94 GHz 1 Tx and 4 RX chips designed in a 65-nm CMOS process. The measured output power of the transmitter and the conversion gain of the receiver were 9.77 dBm and 26 dB, respectively. The simulated noise figure of the receiver chip was 8 dB. The Tx and Rx antennas were microstrip patch antennas with a gain of 11 dBi on a Duroid substrate. The chirp period of the sawtooth FMCW waveform was 50 μs. The baseband signal was bandpass-filtered with a passband gain of 26 dB and sampled at a rate of 50 MSPS with a 14-bit ADC. The output of the ADC was acquired using an FPGA. The distance and angle information of the target were calculated using the FFT-based algorithm. The processed results closely matched the calculated results based on the specifications of TRx chips and processing gain, which confirmed the validity of the developed radar system. [ABSTRACT FROM AUTHOR]

Recently, as global space development and space risk have increased, in Korea, considerable attention has been diverted to the development of space surveillance radar (SSR) capable of wide-area and full-time monitoring. For the efficient development of domestic SSR, which is usually expensive, it is necessary to appropriately derive the requirements for SSR based on analyses of overseas advanced cases. In this study, based on an analysis of the space fence surveillance radar in the USA, the field of view for the search fence was set. By deriving and analyzing the maximum number of observable targets per day and the cumulative distribution of the duration of detection, a method was developed to derive the requirements for the search fence when developing a domestic SSR in the future. [ABSTRACT FROM AUTHOR]

In this paper, a K-band complementary metal-oxide-semiconductor (CMOS) ultra-wide-band (UWB) radar is presented. Using an equivalent time sampling technique with a delay-locked loop (DLL), virtual 5 Gs/s high-speed sampling is implemented without using a high-speed analog–digital converter. The receiver comprises a low-noise amplifier, radiofrequency variable amplifier, mixer, and baseband analog, whereas the transmitter comprises switching and driver amplifiers. For the UWB signal, a voltage-controlled oscillator-based impulse generator provides a periodic pulse signal using a switching amplifier controlled by a DLL clock. The proposed UWB radar SoC is fabricated using a 65 nm CMOS wafer, and the measured conversion gain and noise figure of the radar receiver are 79 dB and 7.4 dB, respectively, at 24 GHz. Consequently, we confirm that the measurement of the 11.3 m standard sphere is feasible. [ABSTRACT FROM AUTHOR]

Herein, we implement a software-in-loop simulation (SILS) system for fighter radar systems. The implemented SILS system simulates fighter radar environments and hardware by mathematical modeling, generates radar-simulated digital signals, and stores/analyzes simulation results. It includes a personal computer (PC)-based virtual radar processing unit, which can be used to develop radar control and process algorithms and codes and can also examine the functions and performance of the software and code of actual radar processing equipment by connecting actual equipment. Because antenna and transceiver models are included, the performance of the initial hardware designs at the system level can be examined in the simulation environment, thereby increasing the hardware design and development speed. We demonstrate the validity and usefulness of the SILS system, implemented using the radar environment and hardware mathematical models obtained from the development of fighter radars for numerous years, through SILS-based test results. [ABSTRACT FROM AUTHOR]

An airborne radar echo signal includes signals returned from clutter and a target; thus, simulating the signal from the clutter may be crucial for predicting and analyzing accurate radar performance. Because it can be extremely difficult and expensive to obtain real measured signal data for various scenarios, an accurate signal generation method is required. Existing weather clutter and ground clutter simulators for an X-band airborne radar are combined to simulate the echo signal when two clutters exist simultaneously. The weather clutter effect becomes more significant with increasing frequencies, such as in the X-band. The proposed simulator can generate time-do- main signals by considering the random characteristics of the clutter signal and the Doppler effect caused by the movement of aircraft and clutter. In addition, a simple scheme is proposed for generating signals from artificial structures. Finally, the finite bandwidth of the transmitted chirp signal is calculated to improve the accuracy of the generated signal. [ABSTRACT FROM AUTHOR]

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]

The Active Protection System is a defense system that protects armored vehicles, such as tanks, from attacks by high-velocity projectiles such as anti-tank missiles, by actively neutralizing the projectile before it strikes the vehicle. Radars are essential for detecting and tracking threats approaching tanks at high speeds, and their tracking accuracy must be a few centimeters to precisely strike the target. However, when high-speed targets are tracked, range walk occurs owing to the target speed, resulting in a range tracking error proportional to the speed. In this study, we investigated a real-time speed compensation method by adjusting the NCO frequency in the signal pre-processing stage to secure the range tracking accuracy of radars suitable for active defense devices. To verify the performance of the algorithm, target signal simulation and signal processing were performed using MATLAB M&S. The final tracking performance was analyzed using CFAR and clustering for target detection and a Kalman filter-based tracking algorithm. [ABSTRACT FROM AUTHOR]

Recently, shipborne radars are being developed into fully-digital Active Electronically Scanned Array (AESA) multifunctional radars (MFR) that are capable of electronic beam steering, simultaneously detecting and tracking multiple targets in a complex maritime environment, and performing electronic countermeasure functions in real-time. However, because the development process of a radar is expensive owing to its high complexity, using Simulated Signal Generator (SSG) that can emulate the function of an antenna proves effective in radar development. In this study, we propose a real-time implementation method for SSG capable of simulating maritime battlefield environments and targets using fully digital-based antenna simulation. We propose a CPUand FPGA-based real-time system architecture, fixed-point operation, real-time channel noise generation method, and real-time beamforming structure to generate modeling results that are presented. [ABSTRACT FROM AUTHOR]

As numerous synthetic aperture radar (SAR) satellites have been launched to secure surveillance and reconnaissance capabilities, considerable research has focused on SAR jamming methods. In particular, methods that utilize the received SAR signals for deceptive jamming have drawn increasing attention. However, because these methods perform deceptive jamming after the SAR signal is received, they cannot create a false target ahead of the jammer along the range axis. Accordingly, as part of the research on deceptive jamming methods to overcome this limitation, this study aims to estimate the transmission time of the next SAR signal and the center frequency in real time from the received SAR signal. The proposed method precisely estimates these parameters using pulse compression and recursive least squares estimation, and the estimation results are confirmed through simulations. [ABSTRACT FROM AUTHOR]

In-vehicle seat occupancy detection sensors using ultra-wideband (UWB) technology has recently garnered increased attention. These sensors can be classified into two types: those that use UWB communication and those that use UWB radar. Each type has distinct advantages and disadvantages; therefore, an objective comparison of the performance differences between the two detection methods under the same conditions is meaningful from a practical application perspective. Accordingly, this study aimed to compare the perform- ances of these two methods. The two systems were installed within the same vehicle environment, ensuring maximum possible con- sistency between the installation. Their sensing performances were then compared using the same artificial intelligence (AI) algorithm. The results indicate that both methods could sense 16 in-vehicle seat occupancy situations with a high detection accuracy of over 99 %, except for minor discrepancies in the installation location and preprocessing method. [ABSTRACT FROM AUTHOR]

A radar system transmits radio waves and interprets the returned signal to perform a specific function. Radio waves traveling between the radar and an unknown target are affected by refraction as they travel through the atmosphere, which increases the possibility of errors in the interpretation of the results when the radar is operating. If it is possible to predict the extent to which radio waves are affected by refraction, this capability can be applied to radar operation to direct radio waves to an area where an unknown target is likely to be operating. In this study, a method for correcting the elevation angle of the antenna was investigated by analyzing a case in which the radio wave propagates along the elevation angle and a case in which it is refracted. It was confirmed that the main beam of the antenna can be set toward the target area by applying the correction method to four arbitrary positions. [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]

The purpose of an interleaved mode is to simultaneously provide two or more modes to the user. For this, the time resources allocated to each mode are reduced, and thus, the performance of each mode is degraded. Therefore, a scheduling method is required that can minimize the performance degradation of each mode by appropriately allocating resources. In the interleaved mode that operates the ground imaging and air-to-air search/track modes, the image update interval is longer than that of the single mode operation, and air-to-air tracking performance can be degraded; therefore, scheduling must be planned considering them. In this paper, to always obtain images above a certain proportion of the current search area while minimizing the degradation of air-to-air tracking performance, a scheduling algorithm that adaptively adjusts the image update interval by utilizing the posture and position change of the radar-mounted aircraft is proposed. [ABSTRACT FROM AUTHOR]

In deramped synthetic aperture radar (SAR) equipment that utilizes two or more different bands (different center frequencies), if different pulse repetition frequencies (PRFs) are employed when using a single receiver, owing to its economic feasibility, images of other bands may appear and become ghost images. In this study, to determine the exact location of a ghost image illustrated in inverse SAR images, mathematical formulas are adopted to determine the location of the ghost image in the multiband. Even if the bandwidth and PRF are the same, if Tu (unprocessed time interval) is different, we can observe that a ghost image appears near the actual image. If a time delay is noted, the ghost image appears at the same position as that in the absence of a delay. Thus, the effect of ghost images should be minimized by changing Tu. [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]

In this study, the radar cross-section (RCS) of a large structure is analyzed using the linear bounding volume hierarchy (LBVH), which is a representative acceleration algorithm of the ray-tracing technique. A ray-tracing technique, which is a high-frequency method, is used to analyze the electromagnetic properties of large structures, and bounding volume hierarchy (BVH), a binary tree structure, is applied to reduce the intersection search time. The improvement in the calculation speed is quantitatively analyzed by dividing an arbitrary scatterer into several triangles. The calculation results are compared with those of multilevel fast multipole method (MLFMM) and ray-launching geometrical optics (RL-GO) using the Feko commercial software to verify the accuracy. The proposed technique can be utilized for the efficient RCS calculations of large structures. [ABSTRACT FROM AUTHOR]

Aircraft inevitably experience motion caused by the flight environment in airborne synthetic aperture radar (SAR) systems. Therefore, motion compensation is essential. The real-time motion method is vital for high-resolution SAR image formation and onboard SAR signal processing. In this paper, an effective implementation scheme for a radar-timing signal generator is presented. This paper also describes a motion prediction method suitable for airborne SAR systems. The performance of the proposed real-time motion compensation scheme was evaluated using a captive flight test. [ABSTRACT FROM AUTHOR]