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If the same azimuth angle is maintained in phased-array radar, it is impossible to distinguish the range. To solve this problem, frequency-diverse array radar has been proposed; many studies have been conducted recently. If the phased-array radar arranges signals with different phases and projects a beam at one azimuth angle, the frequency-diverse array radar produces a two-dimensional beam that distinguishes range and angle by arranging signals with the same phase but different frequencies. Frequency-diverse array radar produces a beam directed to a target by changing the frequency offset between neighboring array elements. The beam pattern varies according to whether the frequency offset is constant or variable, and whether it is linear or non-linear. Compared to phased-array radar, there are significant advantages including target-detection accuracy; there are also several disadvantages. In this paper, we discuss frequency-diverse array radar and its future, considering research achievements and applications to improve performance and overcome its disadvantages. [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]

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]

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]

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 this paper, we propose an algorithm to remove false plots in the weather clutter for a low-altitude aircraft detection radar in heavy rain conditions. The proposed algorithm detected the signal being saturated by the weather clutter and removed the false plot after estimating the radial velocity of the weather clutter and calculating the range of speed of the false plot when the receiving signal was saturated. The proposed algorithm presented the result of the effectively removed false plots in the weather clutter for a real radar in heavy rain circumstances. [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]

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]

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]

Atmospheric conditions and terrain are representative elements of radar operating environments. The radar operating environment varies depending on the installation location and changes radar performance. In the case of the atmospheric condition, it changes every moment and changes radar performance, so it is not easy to supplement radar performance by reflecting it in real time. On the other hand, in the case of terrain, when radar is installed, the surrounding terrain information does not change significantly, so radar performance can be supplemented through analysis. In this paper, the radar performance variation was analyzed according to the beam steering angle reflecting the atmospheric measurement data of the past five years using the M&S analysis tool. As a result, when the beam was raised by 0.3° compared to the original angle, the maximum detection range increased by about 7.1 NM, and the standard deviation was reduced by about 1.2 NM. [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]

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]

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]

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]

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]

The atmosphere has different characteristics for each altitude and it changes with place and time. The beam propagated from the radar has a different path depending on the atmosphere, thereby changing the radar performance. So, it is necessary to analyze atmospheric conditions to prevent the radar performance degradation. In this paper, based on four weather data over the past seven years(`16~`22), the analysis methods and result of atmospheric conditions affecting the radar performance were described. As a result, the refractive index tended to increase over the years and it had a larger refractive index in the east than the west. Also, comparing the frequency of ducting occurrence, the west had about 5% higher incidence than the east during seven years. [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]

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]

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]

This paper presents a through-type harmonic transponder for S-band nonlinear radar. To increase the operating frequency range, a 2-stage L-shaped matching network was configured for the input and output matching networks. In previous studies, conventional har- monic transponders were configured with λ/4 stubs in the input and output matching networks to minimize the influence of these net- works because the impedance mismatch suppresses the second harmonic and fundamental signals. However, in this design, a λ/4 open stub was utilized at the output and configured with the output matching network to alleviate the insertion loss of the additional open stub. For verification, the proposed circuit was implemented with the circuit size of 37.6 mm×16.1 mm. The measurement results show that the conversion gain is maintained over −15 dB for frequencies between 2.8∼3.8 GHz at −5.5 dBm and −17.5~11 dBm at 3.1 GHz of input power. [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]

This study confirmed that the performance of elevation estimation using radar in a multipath environment varies depending on the receiving beam grid. For the analysis, a beam grid of 16 cases was used. First, three received beams and five two cases were compared. In addition, the two cases were compared when the reception beam overlap rates were 0, 15, 30, and 50 %. Finally, the relative position relationship between the reception beam and horizontal line was classified. In other words, the case where the center of the reception beam was placed on the horizontal line and that where the edge of the reception beam was placed on the horizontal line were compared. For each of these 16 cases, three target altitudes were analyzed. The RMSE according to the SNR was obtained to analyze the elevation estimation performance. A double-null algorithm based on 3D BDML was used. elevation estimation simulations were performed on low-altitude targets in a multipath environment to compare the performance of elevation estimation in various beam grids. [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]

Jammers are commonly employed in electronic warfare (EW) environments. A system that can respond according to the jamming signals emitted by jammers can be developed by predicting the affected radar detection range and burn through range. In this paper, we propose an M&S technique for calculating the received power by considering the actual terrain information and the curvature of the Earth, and analyze the burn through range with the specifications of the radar and jammer. The proposed M&S technique was applied by using the specifications of the experimented actual radar, and the burn through range was analyzed for targets with various radar cross sections. It was confirmed that the burn through range from the radar decreased as the radar cross section of the target decreased, and the effective isotropic radiated power of the jammer decreased. [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]

Owing to the increase in the use of radars in vehicles, FMCW-type radars are being widely used. Concerns regarding the exposure of the human body to electromagnetic waves by such vehicle radars are increasing. However, there is currently no standard for human body protection against FMCW waveforms in Korea. In this study, various types of FMCW waveforms were tested and measured to present basic data for human exposure assessment. [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]

Radars used by air-crafts have two important characteristics; First, they should have a real-time signal processing system finishing signal processing before deadline while getting and processing successive in-phase and quadrature data. Second, they can cover a lot of modes including A2A(Air to Air), A2G(Air to Gound), A2S(Air to Sea), and Ground Map(GM). So the structure of radar signal processing SWs in modern airborne radars are becoming more complicate. Also, the implementation of radar signal processing SW needs to reuse common code blocks between other modes for efficiency or change some of the code blocks into alternative algorithm blocks. These are the reason why the radar signal processing SW framework suggested in this paper is taking advantage of modular programming. This paper proposes an modular framework applicable on the airborne radar signal processing SW maintaining the real-time characteristic using the signal processing procedures for A2G/A2S as examples. [ABSTRACT FROM AUTHOR]

This paper presents a 915 MHz low-loss harmonic transponder for harmonic radar sensors. The proposed through-type harmonic transponder comprises an input and output matching network with an independent impedance control circuit. This control circuit enables the independent matching of the input and output loads. The circuit minimizes the impedance influence between the input and output matching networks, regardless of the impedance change of the input and output terminals according to the internal and external environments. The designed harmonic transponder was implemented and its performance was measured. The results show that the conversion gain of the proposed circuit is >-10 dB over a wide input power range of -20-0 dBm. Furthermore, the implemented circuit maintains the conversion gain of over -11.5 dB and the low fundamental output power of under -32.2 dBm in the frequency range of 900-930 MHz. [ABSTRACT FROM AUTHOR]

In this study, motion compensation for electronic beams in sea environments is proposed. Because the radar on a ship fluctuates according to the sea environment, it is necessary to compensate for the fluctuation to achieve accurate beam steering. Unlike the fluctuations in the pitch and yaw directions, where only compensation for the beam steering value is required, the fluctuation in the roll direction causes the beam to rotate. Therefore, compensation for the rotation of the beam in the roll direction is necessary. For this purpose, beam rotation and 2-D beam steering were performed. Finally, the proposed method is applied to a 20×20 array and verified. [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]

The meaning of crosswalks and traffic lights in modern society has changed a lot as the enforcement of traffic signal violations has been strengthened. In this paper, we present a new next-generation traffic light method using radar and Can-bus communication methods suitable for the new traffic signal enforcement system. This method is a system that prevents accidents by transmitting information on the entry of a person and a car to a traffic light in a place where a person and a car passing through a mutually invisible traffic light cannot be seen. Since this system has only been developed for a month, it may be somewhat lacking in experimentation. However, in just one month, there have been no incidents except for a few people where the system has been installed. [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]

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]

The non-contact vital sign estimation of an individual using radar sensors has been widely researched. However, in the case of an individual with undesirable rigid-body motion of the torso, non-contact vital sign estimation may fail owing to extreme phase fluctuations caused by the larger rigid-body motion of the torso than the micro motion of the vital sign. To address this problem, we propose a rigid-body motion compensation method using the complex echo signals of the IR-UWB radar for the vital sign estimation of an in- dividual with rigid-body motion. The proposed method extracts a complex signal vector using principal component analysis from com- plex echo signals in a radial range and pulse time domain. Next, compensation for the rigid-body motion is implemented by minimizing the entropy of the spectrum for the complex signal vector. In simulations using a point-scatterer model and experiments using IR-UWB commercial radar, we verified that our proposed method is capable of performing successful vital sign estimation of an individual with undesirable rigid-body motion. [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]

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]

Clutter is the radar noise signal that is reflected from the elements surrounding the targets. Since clutter degrades the radar system’s range and doppler frequency detection capability, clutter suppression is a critical signal-processing algorithm that can improve the performance of a radar system. This paper proposes a ground-clutter suppression method using denoising encoder-decoder deep learning network with dual encoding channels, residual connections, and skip connections. Radar signal dataset pipeline was generated using MATLAB in order to train the network. In this paper, deep learning-based clutter suppression method that can be applied in various operating conditions, is discussed. [ABSTRACT FROM AUTHOR]

This paper presents the calculation of the approximate peak power of an ultra-wideband (UWB) pulse based on average power and 10 dB bandwidth measured using a spectrum analyzer. The instantaneous peak power of the UWB pulse signal converted from the instantaneous peak voltage measured using an oscilloscope and the result of the proposed calculation method are compared and shown to be approximately equal. A 3∼5 GHz CMOS UWB radar sensor is used for verification. The center frequency, pulse repetition frequency, and bandwidth are 4 GHz, 10 MHz, and 10 dB, respectively. The center frequency and pulse repetition frequency are 4 GHz and 10 MHz respectively. 10 dB bandwidth can be adjusted in the range 500 MHz to 1 GHz. The test was performed while varying amplitude and 10 dB bandwidth of UWB pulse. And the resolution bandwidth of the spectrum analyzer was also varied. The result indicates an error of approximately 0.05∼1.7 dB. [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]

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]

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]

To increase the range resolution of OFDM radars, a wide bandwidth of the baseband signal is required, which increases the ADC/DAC sampling rate. Although radar signal processing with linear stepped-carrier (SC) OFDM waveforms has been developed to overcome it, the linear pattern in the subband allocation does not provide flexibility in spectrum utilization. In this study, we proposed the range-Doppler (RD) imaging method using SC OFDM waveforms with a nonlinear hopping pattern. In addition, we proposed a method for calibrating the Doppler estimation error owing to the nonlinear hopping pattern. Numerical simulations were used to verify that the proposed method yielded a similar RD map and MSE performance compared to the conventional linear SC OFDM, thereby providing flexibility in spectrum utilization. [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]

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]

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]