• ETRI Journal
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• v.40 no.5
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• pp.592-603
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• 2018

In order to obtain better target identification performance, an efficient waveform design method with high range resolution and low sidelobe level for orthogonal frequency division multiplexing (OFDM) multiple-input multiple-output (MIMO) radar is proposed in this paper. First, the wideband CP-based OFDM signal is transmitted on each antenna to guarantee large bandwidth and high range resolution. Next, a complex orthogonal design (COD) is utilized to achieve code domain orthogonality among antennas, so that the spatial diversity can be obtained in MIMO radar, and only the range sidelobe on the first antenna needs suppressing. Furthermore, sidelobe suppression is expressed as an optimization problem. The integrated sidelobe level (ISL) is adopted to construct the objective function, which is solved using the Broyden-Fletcher-Goldfarb-Shanno (BFGS) algorithm. The numerical results demonstrate the superiority in performance (high resolution, strict orthogonality, and low sidelobe level) of the proposed method compared to existing algorithms.

• Journal of the Korea Institute of Military Science and Technology
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• v.18 no.4
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• pp.369-375
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• 2015

In this paper, transparent circuit analog radar absorbing structure with angular stability for stealth aircraft canopy was proposed and designed. To obtain wideband electromagnetic absorption, optical transparency and smaller thickness, we proposed the novel FSS(Frequency Selective Surface) for X-band and implemented the resistive FSS and PEC(Perfect Electric Conductor) plane using ITO(Indium Thin Oxide) coating with optical transmissivity of 90 %. Reflection loss characteristics for different incident angles of both TE(Transverse Electric) and TM(Transverse Magnetic) polarizations are presented through simulations. We then fabricated the proposed structure to verify the simulation results. The comparisons between the simulation and measured results show good agreements. The results also show that the proposed radar absorbing structure can provide better frequency stability for different incidence angles and polarizations as well as optical transparency. We can apply this proposed structure to the canopy of stealth aircraft and other stealth applications for visible transparency.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.3
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• pp.433-444
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• 2020

This study proposes a method to improve the sleep stage and efficiency estimation of sleep apnea patients using a UWB (Ultra-Wideband) radar. Motion and respiration extracted from the radar signal were used. Respiratory signal disturbances by motion artifacts and irregular respiration patterns of sleep apnea patients are compensated for in the preprocessing stage. Preprocessing calculates the standard deviation of the respiration signal for a shift window of 15 seconds to estimate thresholds for compensation and applies it to the breathing signal. The method for estimating the sleep stage is based on the difference in amplitude of two kinds of smoothed respirations signals. In smoothing, the window size is set to 10 seconds and 34 seconds, respectively. The estimated feature was processed by the k-nearest neighbor classifier and the feature filtering model to discriminate between the sleep periods of the rapid eye movement (REM) and non-rapid eye movement (NREM). The feature filtering model reflects the characteristics of the REM sleep that occur continuously and the characteristics that mainly occur in the latter part of this stage. The sleep efficiency is estimated by using the sleep onset time and motion events. Sleep onset time uses estimated features from the gradient changes of the breathing signal. A motion event was applied based on the estimated energy change in the UWB signal. Sleep efficiency and sleep stage accuracy were assessed with polysomnography. The average sleep efficiency and sleep stage accuracy were estimated respectively to be about 96.3% and 88.8% in 18 sleep apnea subjects.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.1
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• pp.28-37
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• 2019

In this paper, we propose a real-time system for counting people. The proposed system uses an impulse radio ultra-wideband(IR-UWB) radar to estimate the number of people in a given location. The proposed system uses learning-based classification methods to count people more accurately. In other words, a feature vector database is constructed by exploiting the pattern of reflected signals, which depends on the number of people. Subsequently, a classifier is trained using this database. When a newly received signal data is acquired, the system automatically counts people using the pre-trained classifier. We validated the effectiveness of the proposed algorithm by presenting the results of real-time estimation of the number of people changing from 0 to 10 in an indoor environment.

• Journal of Advanced Navigation Technology
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• v.6 no.2
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• pp.97-103
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• 2002

A recent technology trends in synthetic aperture radar(SAR) requires the ultra high resolution performance in detecting and precisely identifying the targets. In this paper, as a technique for enhancing the radar range resolution, the wide band chirp connection algorithm is presented by stitching the several chirp modules with unit bandwidth based on the linear frequency modulated chirp signal waveform. The principles of the digital chirp signal generation and its architecture for implementation is described with the wide band chirp signal generator, modulator, and demodulator. The performance analysis for the presented algorithm is given with the simulation results.

• JSTS:Journal of Semiconductor Technology and Science
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• v.11 no.4
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• pp.238-246
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• 2011

A 3-5 GHz UWB radar chip in 0.13 ${\mu}m$ CMOS process is presented in this paper. The UWB radar transceiver for surveillance and biometric applications adopts the equivalent time sampling architecture and 4-channel time interleaved samplers to relax the impractical sampling frequency and enhance the overall scanning time. The RF front end (RFFE) includes the wideband LNA and 4-way RF power splitter, and the analog signal processing part consists of the high speed track & hold (T&H) / sample & hold (S&H) and integrator. The interleaved timing clocks are generated using a delay locked loop. The UWB transmitter employs the digitally synthesized topology. The measured NF of RFFE is 9.5 dB in 3-5 GHz. And DLL timing resolution is 50 ps. The measured spectrum of UWB transmitter shows the center frequency within 3-5 GHz satisfying the FCC spectrum mask. The power consumption of receiver and transmitter are 106.5 mW and 57 mW at 1.5 V supply, respectively.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.6
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• pp.27-31
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• 2017

A high-performance wideband transition from double-sided parallel-stripline (DSPSL) to coplanar stripline (CPS) is proposed. This transition is designed by consideration of gradual field transformation and optimal impedance matching between DSPSL and CPS. Clear design guidelines of proposed transition are provided to determine the ground shape and the transition length. The fabricated transition exhibits less than 0.7 dB insertion loss per transition for frequencies from 6.2 to 18.2 GHz, and less than 1.25 dB insertion loss to over 30 GHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.12
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• pp.986-991
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• 2018

In this paper, an A/D conversion module was designed and fabricated to improve the dynamic range of wideband digital receivers. The A/D conversion module for expanding the dynamic range converts signals into a digital signal by branching the input signal into the normal path and the amplification path according to the input signal level. Test results of the fabricated module show that the normal path of the A/D conversion module converts an input level of -57 dBm to -12 dBm into a digital signal, and the amplification path converts an input level of -30 dBm to +12 dBm into a digital signal without distortion. This translates to an input dynamic range characteristic of 69 dB. Moreover, it is confirmed that the constant output characteristic is exhibited at an instantaneous bandwidth of 100 MHz.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.6
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• pp.1111-1116
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• 2007

Antennas of the near field detection radar require little distortion in time domain caused by multi reflections between feed and open ends of the antenna, so that help to discriminate the target signal from the clutters. The resistive loading techniques have been used to reduce the late time distortions in order to prevent masking of target. In this paper, we design a microstrip antenna with two arms having sloted lines, which have inductance loading effect. Implemented antenna shows better performance on reducing late-time ringing, and the peak value of the received signal becomes 45% greater than the one by the antenna with two non-sloted lines.

• Journal of electromagnetic engineering and science
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• v.9 no.4
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• pp.202-210
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• 2009

In this paper, we have analyzed the effect of interference between ultra-wideband(UWB) and intelligent transport systems(ITS). The maximum possible UWB emission power and minimum possible distance between UWB devices and ITS are found. In order to analyze the interference, we employ the Monte-Carlo(MC) method. We consider six situations, which are indoor office line-of-sight(LOS), indoor office non-line-of-sight(NLOS), indoor residential LOS, indoor residential NLOS, outdoor rural LOS, and outdoor rural NLOS environments. From the simulation results, it is confirmed that coexistence between UWB and ITS devices can be realized in accordance with the emission mask of 19.3 dB for indoor application or 19.3 dB for an image system. And in the outdoors, coexistence between UWB and ITS devices can be realized if the emission mask is at least 1.6 dB for vehicles' radar systems.