• Proceedings of the Korean Society of Broadcast Engineers Conference
• /
• 2013.06a
• /
• pp.338-341
• /
• 2013

본 논문에서는 동일 주파수 대역 내 DRM(Digital Radio Mondiale) Plus 신호와 FM(Frequeny Modulation) 신호가 모두 서비스 되는 Hybrid 방송 모드에 적합한 DRM Plus 신호 검출 기법을 제안한다. OFDM(Orthogonal Frequency Division Multiplexing) 신호의 Guard-Interval 상관 기법을 그대로 적용할 경우 DRM Plus 신호 검출 성능은 우수하나, FM 신호 수신 시 False Alarm 발생 확률이 증가하는 문제점이 발생한다. 제안한 방법은 Guard-Interval 상관 방법에 Reference 블록을 포함하고 있어, 약한 DRM Plus 신호에서도 판별 확률이 높고, 아날로그 FM 신호 수신 시 False Alarm이 발생할 확률이 낮은 특징이 있다. 모의 실험을 통하여 제안한 기법의 성능을 확인한다.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.13 no.3
• /
• pp.239-254
• /
• 1988

In this paper an exciter which performs modulation and amplification is composed of high power(30dBm) VCO(Voltage Controlled Oscillator) using push-pull circuit. Modulation is FSK using PLL(Phase Locked Loop). A single loop PLL synthesizer having sequency range of 42.5-100.5MHz, 25KHz channel spacing and switching time of 1msec converts down the exciter VCO frequency to 1.25MHz. This signal mixed with the FSK modulated signal coming in the phase detector of exciter. The acquisition time of exciter for frequency hoppng is less than 200usec, so the total acquisition time for transmission is less that 1.5msec. There is no need of additional power amplification because power amlifiction by high power VCO is high enough to communicate within near distance. The proposed frequency synthesizer is not complex so it is suitable for low cost slow frequency hopping spread spectrum communication.

• Proceedings of the KOSOMBE Conference
• /
• v.1995 no.11
• /
• pp.167-170
• /
• 1995

An frequency modulated (FM) DANTE pulse sequence generates a quadratic phase toward the transverse of image by an FM RF pulse. In the image of a serious susceptibility effect, the phase due to the difference of the susceptibility in the pixel occurs susceptibility error which arise signal loss. But the signal loss due to the susceptibility effect in the pixel is reduced when the quadratic phase adds in the pixel. In this paper, we have generated a quadratic function toward the transverse (X-Y) using FM DANTE sequence and the susceptibility effect is reduced in the gradient echo (GE) imaging. Computer simulation and experimental results is obtained by using a whole-body KAIS 2.0T NMR system.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.5 no.3
• /
• pp.221-228
• /
• 2000

본 논문에서는 전기·전자 장비의 활용이 확대되면서 더욱 더 관심이 고조되고 있는 전자파장해에 대하여 논하고자 한다. 기존 PWM 직류전원장치에서는 회로 소자 및 배치에 따른 기생소자와 갑작스런 전압/전류의 변화에 의해 전자파장해를 발생시킨다. 본 논문에서는 PWM 직류전원장치에서 발생하는 전자파장해의 특성을 고찰하고, 출력전압 조절에 큰 영향을 주지 않는 범위내에서 PWM 제어가 가능하면서 두 개의 고정된 스위칭주파수로 연속적으로 변조하는 Bi-FM 변조제어방식과 랜덤하게 변화하는 스위칭주파수 변조제어방식을 이용하여 전도잡음을 저감시킬 수 있는 변조방식을 논할 것이다. 또한 이들 변조 방식의 주파수 스펙트럼 특성을 비교·분석하여 설명하고, 제어기를 분석·설계하여 실험을 통하여 스위칭주파수와 그 고조파 주파수들의 측대역으로 전도잡음이 분산되고 전도잡음의 피크치가 감소됨을 확인하고자 한다.

• Electronics and Telecommunications Trends
• /
• v.9 no.4
• /
• pp.131-138
• /
• 1994

최근 무선통신의 활성화에 따라, V/UHF(very/ultra high Frequency) 대역에서 한정된 주파수를 효율적으로 이용하기 위한 방법의 하나로서, 점차 점유 주파수 대역의 폭을 축소하여 보다 많은 이용자를 수용하도록 무선 채널의 협대역화가 추진되고 있다. 본 고에서는 먼저 V/UHF 대역 무선 통신에서 채널의 협대역화에 관련된 기술 중에서 현재까지 사용되고 있는 FM(frequency modulation), AM(amplitude modulation) 변조 방식의 장,단점을 살펴본후, 새로운 LM(linear modulation) 변조 방식에 대한 기술적 배경 및 특성을 알아보았다. LM은 SSR(single side band)-AM이 발전한 것으로서, TTIB(transparent tone-in-band), CLT(Cartesian loop transmitter), FFSR(feed-forward signal regeneration), DSP(digital signal processing)등 4가지의 기술이 결합하여 만들어진 것이다. LM 방식에 사용된 4가지 기술을 소개하고, 기존의 변조 방식에 비해 개선된 사항에 대해 서술한다.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.57 no.11
• /
• pp.1981-1987
• /
• 2008

This paper proposed one of various acoustic resonance reduction technique for three kinds of ceramic lamps (CDM-150, HCI-150, CMH-150). To reduce the acoustic resonance in the HID lamps, the researched results showed that the frequency modulated signal with the triangle waveform is very effective in order to drive th LCC type half-bridge inverter for HID lamp. Experimental results proved that the acoustic resonance could be rejected, if the adequate switching frequency band is selected and the driving signal frequency is modulated with a triangle waveform.

• Journal of Electrical Engineering and Technology
• /
• v.9 no.2
• /
• pp.771-776
• /
• 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 ${\mu}sec$.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.11 no.6
• /
• pp.44-49
• /
• 1974

reactance modulator composed of multi-stage phase modulator utilizing VVC diodes as variable reactance elements and an oscillartor-modulator, utilizing a VVC diode as a tuning element, coupled to a crystal resonator through an artificial λ/4 network are introduced and their characteristics as FM modulator are compared mutually from the practical view points. especially, to get high modulation sensitivity of reactance modulators using VVC diodes, making a multi-stage modulation distortion characteristics of multi-stage modulator was necessary. The harmonic moj\dulationdistorion characteristics of multi-stage reactance modulator is analized in detall. Multi-stage reachance modulator is preferable to maintain sufficiently stable carrier frequency over the wide range of temperature and a mobile-transceiver was made through this method. On the other hand, FM-Quartz oscillator using a VVc diode is suitavle for handy-talkies of good quality were made through this method.

• Journal of the Institute of Convergence Signal Processing
• /
• v.7 no.4
• /
• pp.207-213
• /
• 2006

This paper presents the design and implementation of a video processor for the device of need TV-OUT function. The designed video processor satisfies the standard conditions of ITU-R(International Telecommunication Union-Radiocommunication) BT.470. Also, in order to apply various digital device, we concentrate upon hardware complexity. ITU-R BT.470 can be classified as NTSC, PAL or SECAM. NTSC and PAL use QAM(Quardarature Amplitude Modulation) to transmit color difference signals and SECAM uses FM(Frequency Modulation). FM must have antic-cloche filter but filter recommended by ITU-R BT.470 is not easy to design due to sharpness of the frequency response. So this paper proposes that the special quality of anti-cloche filter is transformed easy to design and the modulation method is modified to be identical with the result required at standard. The processor can control power consumption by output mode to apply portable digital devices. The proposed processor is experimentally demonstrated with ALTERA FPGA APEX20KE EP20K1000EBC652-3 device and SAMSUNG LCD-TV.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.8 no.2
• /
• pp.76-81
• /
• 1983

PCM-NRZ/FM Telemetry system is constructed on the basis of RF link with FM modulatedand NRZ-L binary coded PCM data are assumed to transmit through 5th-order Bessel filter. Upon demodulated by the limiter-discriminator at the receiver, the probability of bit error, which is important for performance estimation of digital system, is analyzed against SNR. The analysis based on the following parameters, that is bit rate 140kHz, frequency of pre-modulation filter f-100kHz, maximum frequency deviation of transmitter 2f=300kHz, was performed. As a result, when the telemetry system with the parameters above is designed, the probability of bit error is obtained as 10 along with fT=0.7 and h=2, T=2.