• ETRI Journal
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• v.29 no.3
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• pp.322-328
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• 2007

We propose a direct-sequence pulse-amplitude modulation (DS-PAM) ultra-wideband (UWB) system which employs a non-linear chirp waveform instead of the conventional Gaussian monocycle in this paper. In the approved frequency for UWB, there exist myriad narrowband interferers. Specifically, we focus on the mutual interference between UWB systems and 802.11a WLAN. This paper offers a method to suppress this in-band narrowband interference by introducing a kind of non-linear chirp waveform. Using the proposed non-linear chirp waveform, the effects of one or more narrowband interference sources with different frequencies can be suppressed. System performance of UWB systems in the narrowband interference environment can be improved. Computer simulations with additive white Gaussian noise successfully demonstrate an increase in performance with the proposed system as compared to traditional linear chirp systems.

• Proceedings of the KIEE Conference
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• 2004.07d
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• pp.2655-2657
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• 2004

기존의 DS-CDMA 방식은 잡음이 많거나 채널 왜곡이 심한 환경에서는 성능이 급속히 저하하는 현상이 나타난다. 이러한 문제점 해결을 위한 다양한 연구들이 현재 진행되고 있으며, 본 논문에서도 이에 대한 해결방안을 제시한다. Chirp 방식은 레이더와 같은 변복조 방식에 다양하게 사용되고 있으며, 원하는 주파수 대역으로 쉽게 이동할 수 있고. 구현이 용이하다는 장점이 있다. 본 논문에서는 다중 접속이 가능한 DS-CDMA 기술과 chirp 변복조 기술을 결합한 Binary Chirp DS-CDMA(BCDS-CDMA) 방식을 제안한다. 제안한 DS-CDMA 시스템 성능을 평가하기 위하여, 가우시안 환경에서 기존의 DS-CDMA 방식과 비교 실험을 하였으며, 실험 결과 chirp을 이용한 방식이 DS-CDMA 보다 개선된 성능을 지니고 있음을 알 수 있었다.

• Journal of the Korea Institute of Military Science and Technology
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• v.5 no.1
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• pp.119-126
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• 2002

본 논문에서는 chirp 변조를 이용한 통신 시스템의 LPI(low probability of intercept)와 AJ(anti-jamming)성능을 분석하였다. 인터셉터에 DAM(delay and multiplier)과 SC(squaring circuit)가 이용된 경우 CBPSK(Chirped BPSK)의 LPI 성능을 분석하였다. 스펙트럼 확산 방식의 CBPSK와 DS/BPSK 시스템에 대한 AJ 성능을 비교 분석 및 주파수 호핑 방식의 FH/CBFSK(Chirped BFSK)와 FH/BFSK, 그리고 FH/BCM(Binary Chirp Modulation) 시스템에 대한 AJ 성능을 분석하였다. LPI 결과로, CBPSK(Chirped BPSK)은 chirp 변수인 chirp 주기($T_3$가 커질수록 좋은 LPI 성능을 보인다. AJ 결과로, PBNJ(partial band noise jammer)환경에서 CBPSK 방식이 DS/BPSK 방식에 비하여 AJ 성능이 우수하고, 마찬가지로 FH/CBFSK 방식이 FH/BFSK 방식에 비하여 AJ 성능이 우수함을 시뮬레이션으로 확인하였다.

• 한국ITS학회:학술대회논문집
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• 2010.05a
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• pp.43-47
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• 2010

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.11
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• pp.1186-1193
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• 2009

In this paper, we propose DDS(Direct Digital Synthesizer) as a new implementation method of chirp LO(Local Oscillator) for compressive receiver applied for RFID signal detection in UHF band. We designed a receiver whose input frequency range is 908.5~914 MHz, DDL(Dispersive Delay Line) bandwidth is 6 MHz, and dispersion delay time is $13\;{\mu}s$. Chirp LO based on DDS is designed to meet $26\;{\mu}s$ sweep time and 12 MHz bandwidth for complete compressive mechanism. The measured 3 dB pulse width of the compressed signal of the fabricated receiver is 260 ns and the frequency resolution for simultaneous input signals is below 200 kHz. These performances indicate that the proposed chirp LO based on DDS and the compressive receiver is suitable for RFID signal detection in UHF band.

• 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.

• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.3
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• pp.256-265
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• 2017

In this paper, an ascheme is proposed for multiuser underwater acoustic communication by using the multi-chirp rate signals. It differs from the well known TDMA (Time Division Multiple Access), FDMA (Frequency Division Multiple Access) or CDMA (Code Division Multiple Access), by assigning each users with different chirp-rate carriers instead of the time, frequency or PN code. Multi-chirp rate signals can be separated from each other by FrFT (Fractional Fourier Transform), which can be regarded as the chirp-based decomposing, and superior to the match filter in the underwater acoustic channel. VTRM (Virtual Time Reverse Mirror) is applied into the system to alleviate the ISI caused by the multipatch and make the equalization more simple. Results of computer simulations and pool experiments prove that the proposed multiuser underwater acoustic communication based on the multi-chirp rate exhibit well performance. Outfield experments carrie out in Xiamen Port show that using about 10 kHz bandwidth, four users could communicate at the same time with 425 bps with low BER and can match the UAC application.

• 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.