• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.6 s.97
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• pp.603-614
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• 2005

In this paper, digital ultra-narrowband Walky-Talky using direct conversion method for CQPSK modulation scheme is implemented with satisfying the requirements of APCO P25. RF transceiver design and implementation scheme that minimize the influence of DC-offset and AC-coupling at ultra-narrowband is proposed. This scheme also minimizes the influence of nonlinear characteristic at power amplifier fir CQPSK modulation method. Test results of full system including DSP module and direct conversion RF transceiver show that FCC emission mask at 36.8 dBm PEP meets the standard requirements. The characteristic of receiver AGC by PWM control signal is linear at 40 dB dynamic range and voice communication at input power level of -116 dBm is successful. Also it is verified that the performance of BER versus frequency offset and versus SNR meets the standard requirements.

• Information and Communications Magazine
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• v.29 no.5
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• pp.3-9
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• 2012

본 논문에서는 재난 통신 및 네트워크 기술 그리고 앞으로의 발전 방향에 대해서 소개 하고자 한다. 제 1장에서는 주요 공공재난안전통신 기술들을 소개한다. 특히 동적 그룹통신기술(Push-To-Talk), 망 복구 및 생존성 향상 기술, 긴급호 구현 기술을 소개하며 또한 재난통신기술 표준화 필요성에 대해서 간단히 설명한다. 제 2장에서는 국내외 재난통신기술 동향을 살펴본다. 특히 미국, 유럽, 아시아에서 사용하는 주파수 대역 및 협대역 및 준광대역 주파수 공용 무선통신 기술인 TETRA(Terrestrial Trunked Radio), iDEN(Integrated Digital Enhanced Network) 및 APCO-P25(Association of Public Safety Communications Officials - Project 25)에 대해서 다룬다. 제 3장에서는 재난대비 미래 광대역 통신체계에 대해서 설명하며 마지막으로 제 4장에서는 본 논문의 결론을 맺는다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.5
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• pp.510-518
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• 2010

In this paper, the designed and implemented results of CFL linearization chip which can be used in mobile radio and TRS terminal of UHF band(380~910 MHz), using $0.6\;{\mu}m$ BiCMOS process based on Si, are shown. As gain control circuits for modifying transmit power are inserted not only in feedback path but also in forward path, the stability of CFL is maintained. And, DC-offset correction function of S/H structure, which is suitable for walkie-talkie PTT operation and is easily implemented, is realized. The performance test results of transmitter show that the regulation of FCC emission mask at PEP 3 W(34.8 dBm) is satisfied when the CQPSK modulated signal is fed and more than 30 dBc improvement of 3rd order IMD is achieved when two-tone signal is inputted.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.7 s.98
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• pp.671-680
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• 2005

The CFL linearisation chip which is one of key devices in ultra-narrowband mobile radio transmitter using CQPSK digital modulation method is designed and implemented with $0.35{\mu}m$ CMOS technology. The reduced size and low cost of transmitter are available by the use of direct-conversion and CFL ASIC chip, which improve the power effi챠ency and linearity of transmitting path. In addition, low power operation is possible through CMOS technology The performance test results of transmitter show -25 dBc improvement of IMD level at the 3 kHz frequency offset and then satisfy FCC 47 CFR 90.210 E emission mask in the operation of CFL ASIC chip. At that time, the transmitting power is about PEP(Peak-to-Envelope Power) 5 W. The main parameters to improve the transmitting characteristic and to compensate the distortion in feed back loop such as DC-offset, loop gain and phase value are interfaced with notebook PC to be controlled with S/W.