• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.2
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• pp.138-141
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• 2018

In this paper, we describe the designed digital waveform of a linear frequency-modulated (FM) chirp signal using field-programmable gate arrays (FPGAs) for image radar, and this signal is modulated with an I-Q modulator, and multiplied by 24 frequency multipliers to obtain a 94-GHz W-band wideband chirp generator. The developed chirp generator is an FM signal with a 94-GHz carrier frequency and a 960-MHz bandwidth, and the flatness is less than 1.0 dB at intermediate frequency (IF) (3.9 GHz), 2.0 dB in the W-band, and it has a 0.3-W output power in the W-band.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.2
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• pp.131-138
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• 2016

In this paper, we studied the IRF performances of the chirp signal used in the SAR system. The most important factors that degrade IRF performances are amplitude and phase errors. Each factor can be represented to linear, quadratic, random and ripple terms. That can be extracted by a quadratic polynomial curve fitting of chirp waveform. We analyzed the IRF performances by the error terms and supposed the minimum value of RF non-linearity to meet the specification of the PSLR and ISLR.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.10
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• pp.69-80
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• 2012

In this paper, we studied the time-domain measurement and analysis techniques using a network analyzer for characterization UWB antenna link radiating impulse signal. For this purpose, we developed the CZT(Chirp z-Transform) algorithm which has characterized zoom-in function and transformed the acquired data from network analyzer to time domain format. Using the CZT algorithm, we proves that it would be better efficient and more faster than the DFT for analyzing the waveform and also be able to zoom-in the arbitrary region.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.484-489
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• 2002

This paper concerns the design and implementation of a Bandwidth Variable Digital Chirp Generator (DCG) for the radar altimeter. A double SRAM parallel structure is used to breakthrough the upper DCG bandwidth limited by the highest clock frequency of the digital chips. An experimental system working in the waveform storage method has been implemented. We show that the bandwidth changed according to the radar altimeter's requirement and the design released the stringent speed requirement of the chips fur making a variable wide bandwidth DCG.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.7
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• pp.761-768
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• 2010

This paper presents an effective method to achieve the wideband waveform for high resolution SAR(Synthetic Aperture Radar) using the frequency multiplication technique. And also this paper analyzes the root causes for the spectral regrowth due to 3rd-order intermodulation in chirp bandwidth expansion scheme using quadrature modulator and frequency multipliers. The amplitude and phase imbalance requirement are defined based on the simulation results in terms of quadrature channel imbalance. This minimizes the degradation of range resolution, peak sidelobe ratio and integrated sidelobe ratio. The wideband chirp generator using the frequency multiplier and memory map scheme was manufactured and the compensation technique was presented to reduce the spectral regrowth of SAR waveform by minimizing the amplitude and phase imbalance. After I and Q channel imbalance adjustment, the carrier level reduces －28.7 dBm to －53.4 dBm. Chirp signal with 150 MHz bandwidth at S-band expands to 600 MHz bandwidth at X-band. The sidelobe levels are reduced by about 8 to 9 dB by compensating the amplitude balance between I and Q channels.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.11
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• pp.949-958
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• 2016

This paper presents the new development result of the multi-band, the multi-mode SDR(Software Defined Radar) platform. The SDR hardware platform is implemented by using the reconfigurable multi-band RF transceiver and antenna modules of S, X, and K-bands, and a programmable signal processing module. The SDR software platform is implemented by using the multi-mode waveform generation of CW, Pulse, FMCW, and LFM Chirp as well as the adaptable algorithm library of signal processing and open API software modules. Through the integrated test of the SDR platform, the operational performance was verified in real-time. Also, through the field-application test, the ground target and air-vehicle drone target were successfully detected and their test results were presented.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.6
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• pp.43-49
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• 2022

FMCW(Frequency Modulated Continuous Wave) Radar is very useful for vehicle collision warning system and autonomous driving sensor. In this paper, the design and implementation of FMCW radar based on two chip MMIC developed as an autonomous driving sensor was described. Especially, generation of frame-based and chirp-based waveform generation and signal processing are mixed to have the strength of maximum detection speed and compensation of speed. This implemented system was analyzed for performance and commercialization potential through lab. test and driving test in K-city.

• ETRI Journal
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• v.44 no.4
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• pp.543-559
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• 2022

To determine a suitable waveform for Internet of Things (IoT) transmission over low-Earth orbit (LEO) satellites, this paper reports the results of a performance comparison between chirp spread spectrum (CSS)-based LoRa and direct sequence spread spectrum (DSSS)-based Ingenu. The performance of both waveforms was measured in terms of the packet error rate, throughput, and packet loss rate, considering the Doppler effect caused by the high speed of LEO satellites and the interference among multiple terminals. Simulation results indicate that the DSSS scheme is more suitable than the CSS scheme for high-traffic IoT services because of its robustness against interference among multiple terminals. However, the CSS scheme is more suitable than the DSSS scheme for high-mobility IoT services because of its robustness against the Doppler effect. We discuss various solutions, such as the preprocessing of Doppler effect and avoidance of packet collision, to enhance the performance of the DSSS and CSS schemes. The simulation results of the proposed solution show that the enhanced DSSS scheme can be a proper waveform in IoT transmission over LEO satellites for both the high-traffic and high-mobility services.

• Journal of the Korea Institute of Military Science and Technology
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• v.18 no.3
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• pp.253-259
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• 2015

This paper introduces a signal processing technique for discrimination of missile target. In order to detect and discriminate the target, a seeker radar makes use of chirp waveform and stretch processing to generate high resolution range profiles(HRRPs). RELAX(relaxation) algorithm, which is one of the spectral estimation techniques, was used to find scattering centers of a missile from HRRP. From the information on the distribution of one-dimensional(1-D) scattering centers on a target, we can discriminate the target without noise.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.2
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• pp.266-269
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• 2012

This paper introduces a signal processing technique for discrimination of ballistic missile's warhead. An interceptor missile to destroy the enemy's ballistic missile requires an information on the location of missile's warhead. In order to detect and locate the missile's warhead, a seeker radar in the interceptor missile makes use of chirp waveform to generate high resolution range profiles(HRRPs). We applied one of the well known spectral estimation technique called ESPRIT (Estimation of Signal Parameters by Rotational Invariance Technique) to these HRRPs to estimate scattering centers on the target. Using the information on the one-dimensional(1-D) scattering centers, we can find the location of the warhead by estimating the length of the missile, Simulation results show that the proposed signal processing technique is efficient in discriminating the warhead of an ballistic missile.