• Journal of the Korean Institute of Telematics and Electronics
• /
• v.9 no.4
• /
• pp.1-6
• /
• 1972

A super widely amplitude modulating AM modulator system, utilizing the impedance trasformation characteristics of transmission line is presented. The analyses and oscillograms obtained from the AM modulator systems using VHF tube, FET or VVC diode as an active element are added to verify the principle of the system.

• Journal of Internet Computing and Services
• /
• v.9 no.1
• /
• pp.21-32
• /
• 2008

In this paper, we propose new modulation schemes using the conventional CACB (Constant Amplitude Coded Multicode Biorthogonal) modulation with constant amplitude property. Also the proposed modulation schemes supports high transmission data rate by increasing the spectral efficiency, In order to obtain the high spectral efficiency, the $Q^2$AM (Quadrature-Quadrature Amplitude Modulation) and CA-$Q^2$AM (Constant Amplitude-$Q^2$AM) are used. We explain the simplest combining modulation scheme of CACB and $Q^2$AM (i.e., CACB-$Q^2$AM). However, this modulation scheme cannot support the constant amplitude property. Hence the first CACB-CA-$Q^2$AM (or CACB-CA-$Q^2$AM I) modulation scheme is proposed for the constant amplitude property. In the modulation scheme, the redundant constant amplitude encoding (spectral efficiency decrease) is required. Therefore, the second CACB-CA-$Q^2$AM (or CACB-CA-$Q^2$AM II) modulation scheme is proposed retaining the constant amplitude and the spectral efficiency. Computer simulations show that the proposed CACB-CA-$Q^2$AM II is the efficient modulation scheme.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.11a
• /
• pp.557-561
• /
• 2002

본 논문에서는 전자식 형광등의 직류구동과 AM 변조시 빛의 주파수 특성에 관하여 다루고 있다. 전자식 형광등을 구동하는 안정기 회로는 상용전원을 직류로 정류시켜 고주파로 변환하여 형광등을 구동시킨다. 형광동의 구동에 사용되는 안정기 회로의 내부 평활 컨덴서의 유.무와 각각 공급되는 전원을 상용전원인 경우, 상용전원을 정류한 경우, 상용전원을 정류하고 정현파를 AM 변조한 경우에 대해서 측정하였으며, 변조하여 입력되어진 정현파가 빛을 통해서 송신되는 것을 확인할 수가 있었다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.22 no.2
• /
• pp.182-190
• /
• 2011

A amplitude modulation(AM) range measuring system utilizes the phase difference of the modulated envelope of the reflected signal to measure the distance. It is known that the AM system has a problem in accuracy due to antenna leakage signals and spurious reflection signals, but an AM range measurement system using an active reflector, which shifts the frequency bands, has been proposed in order to minimize the measurement errors due to spurious signals. In this paper, a new phase measurement module for the AM range measurement system, which enables to measure long distance with good accuracy, is proposed. The modulation frequency is alternatively selected between 8 and 1 MHz, and the measured distance range with this module is up to 150 m within 2 cm accuracy. A JK flip-flop circuit is used for higher phase accuracy, and an XOR circuit is used to cover long distance.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.10 no.1
• /
• pp.49-56
• /
• 2006

In this paper, to overcome the effect of nonlinear power amplifier, CE-CPSK(Constant Envelope Continuous Phase Shift Keying)modulation method which has the constant envelope and continuous phase characteristics is proposed. The code acquisition performances of the CE-CPSK modulated system and BPSK system are analyzed. And the performance is evaluated in terms of mean acquisition time and detection probability with the output backoff of the amplifier in multiuser environment. Results performed in a channel having a high degree of AM nonlinearity(AM-to-AM conversion), have shown that the CE-CPSK signal, when passed through class C-nonlinear Amplifier, has a spectrum with greatly reduced sidelobes compared to the conventional BPSK signal. The code acquisition performance of a CE-CPSK modulation system is better than that of BPSK system with nonlinear amplified multiuser environments.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.19 no.10
• /
• pp.1096-1103
• /
• 2008

This paper proposes an individual order predistortion linearizer using intermodulation distortion(IMD) generator for cancellation the third and the fifth IMD of power amplifier. The IMD generator for controlling the third and the fifth IMD consist of common Emitter amplifier and Schottky diode. These signals are generated by series feedback of Schottky diode to obtain the inverse AM/AM and AM/PM characteristics of power amplifier. The individual order predistorters are consisted of individual IMD generator, power splitter and combiner. The test results show that the third and the fifth IMD can be improved by a maximum 13.5 dB and 0.9 dB in case of CW 2-tone signals. Also, the Adjacent Channel Leakage Ratio(ACLR) can be improved 2.3 dB, 2.5 dB at ${\pm}0.885$ MHz, ${\pm}1.23$ MHz offset frequency for CD-MA IS-95 2FA signals.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.22 no.2
• /
• pp.220-227
• /
• 2011

With the rapid development of mobile communication technology, the technologies based on the diverse digital modulation schemes have been used for the frequency range of over 800 MHz. The only radiation immunity has been tested using only AM signal based on IEC 61000-4-3 without any consideration of the influence of electromagnetic radiation in Korea. However, it has not been tested by wideband digital modulation signals such as cdmaone(IS-95), WCDMA and PM signal. The purpose of this study was to review the standards. In addition, the input signals were analyzed and tested considering the environments in Korea. The results showed that the devices were influenced by digital modulation signal or PM signal more than by AM signal.

• 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.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.7 no.8
• /
• pp.1612-1620
• /
• 2003

This papers describes a nonlinear transfer function modelling of designed GaAs FET power amplifier by measured and simulated values of designed PA amplifier for multi­carrier transmission system, With the results of PA nonlinearity characteristic, we can estimates AM­AM and AM­PM of designed PA. According to the estimated nonlinear characteristics, we can analysis the ACPR of PA for spectral regrowth, the error vector measurement(EVM) of constallation signals and bit error rate of QPSK and 64­QAM. The suggested nonlinear modelling results are used to get an accurate estimate of digital characteristics between PA amplifier and wireless multi­carrier transmission system using OFDM.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.10 no.1
• /
• pp.18-26
• /
• 1973

In AM detection system, when the ratio of the frequency of the carrier to that of the modulating signal becomes less than a ratio of approximately 10:1, AM detectors become unable to detect the impressed signal in a satisfactory waveform. The failure of detecting such a super wide-band AM signal resulting from charging and discharging transient phenomena in associated diode circuit during the detecting of AM signal, has been a cause of limiting the channel capacity in AM or FM super multiplexing systems. This Paper presents the "Poly-phase Envelope Detection System" as a suitable method to solve the problem and the analyses of the system suggested. This system will make it possible to take the envelope out of the impressed AM signal to any desired degree of accuracy even when the ratio of the frequency of the carrier to that of the modulating signal approaches unity. Experiments were carried out to verify the validity of the theory of Poly-phase Envelope Detection System by adopting the frequency conversion method from among the two proposals.proposals.