• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.11
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• pp.1417-1419
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• 2016

In order to improve the transmission performance of a chirp signal-based chirp spread spectrum system, the cross-correlation coefficient (CCC) should be carefully considered. In this paper, we derive the CCC for analyzing the transmission performance and propose the optimal chirp rate based on the analysis. The simulation results verify the mathematical derivations and show that the considered scheme can improve the performance by considering the CCC.

• 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.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.42 no.4
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• pp.53-62
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• 2005

In this paper, we implement a 40kbps narrowband powerline communication modem which is able to high transfer rate than conventional powerline communication technology by using the chirp technique that is one of the spread spectrum techniques. A modem that implement in this paper used the CEBus standard and a symbol that the linear variable frequency signal of 100$\sim$380kHz is kept for 25us. Experimental results, we verified the possibility that communication technology with the Chirp technique can make transfer rate more than 40kbps at narrowband communication.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.8
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• pp.104-108
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• 2006

There are range and azimuth direction resolution of synthetic aperture radar on the aircraft or satellite. Wide bandwidth chirp pulse generation technology is prerequisite for SAR image with fine resolution. There are two kinds of digital chirp pulse generation technology as arbitrary waveform generator(AWG) and direct digital synthesizer(DDS). In this paper, we design and implement a digital chirp pulse generator to generate 300MHz wide bandwidth linear FM chirp pulse for the fine resolution image with direct digital synthesizer. Implemented chirp pulse generator can be useful for the SAR sensors to make 50cm range resolution image.

• Journal of Electrical Engineering and Technology
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• v.9 no.2
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• pp.771-776
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• 2014

In this paper, an agile programmable chirp spread spectrum generator for wideband frequency-jamming applications from 20 MHz to 3 GHz is proposed. A frequency-mixing architecture using two voltage-controlled oscillators is used to achieve a wideband operating frequency range, and the direct digital synthesizer (DDS)-based chirping method with a two-point modulation technique is employed to provide a programmable and consistent chirp bandwidth. The proposed signal generator provides the various programmable FM signals from 20 MHz to 3 GHz with a modulation bandwidth from 0 to 400 MHz. The prototype successfully demonstrates arbitrary sequential jamming operation with a fast band-to-band hopping time of < 10 ${\mu}sec$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.10
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• pp.1957-1964
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• 1994

In this thesis, a Synthetic Aperture Rarar Processor that is possible real-time handling is implemented using CW(Continuose Wave) laser as a light source, CCD(charge Coupled Device) as a time integrator, and AOD(Acousto-Optic Device) as the space integrator. One of the advantages of the proposed system is that it does not require driving circuits of the light source. To implement the system, the linear frequency modulation(chirp) technique has been used for radar signal. The received data for the unit target was processed using 7.80 board and accompanying electronic circuits. In order to reduce the smear effect of the focused chirp signal which occurs Bragg diffrection angle of the AOD has been utilized to make sharp pulses of the laser source, and the pulse made synchronized with the chirp signal. Experiment and analysis results of the data and images detected from CCD of the proposed SAR system demonstrated that detection effect is degrated as the unit target distance increases, and the resolving power is improved as the bandwidth of the chirp signal increases. Also, as the pulse width of the light source decreases, the smear effect has been reduced. The experimental results assured that the proposed system in this papre can be used as a real time SAR processor.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.1
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• pp.69-73
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• 2011

In the defence wireless communications, conventional Anti-Jamming techniques(Frequency Hopping/Spread Spectrum or Direct Sequence/Spread Spectrum) are used to overcome a intentional interfering signals which are single/multitone or partial band jammer etc. DS/SS techniques is very strong on tone jamming signal but not to be on a partial band jammer. So FH/SS AJ performances are expected method of an substitution of DS/SS, however FH/SS could not have good performance on some BMTJ(Band Multi-tone Jammer). So this paper proposes FH-CSS (Frequency Hopped - Chirp Spread Spectrum) to get more robustness against jammers(BMTJ, PBNJ) and analyze the AJ performances.

• 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.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1782_1783
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• 2009

Reflectometry that has been used to localize faults on a cable is introduced. One of the key point of reflectometry is finding time delay between the incident and reflected signals. In this paper, we propose new reflectometry that use Gaussian enveloped linear chirp signal, and use Kalman filter to estimate frequency rate parameter of the chirp signal. From the estimated frequency rate parameter, we can measure the time delay. In a simulation assuming open ended cable, the proposed method is proved to give a good estimation results.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1543-1544
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• 2008

In this paper, we introduce a gaussian enveloped linear chirp signal that can change parameters for consideration of target material characteristics. Using the gaussian enveloped linear chirp signal, time-frequency domain reflectomety is able to detect fault location in power transmission line. we suggest design method of reference signal for power transmission line fault detection. This method is verified by locating fault in HIV low voltage power transmission line.