• ETRI Journal
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• 제45권1호
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• pp.150-162
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• 2023

The polar delta-sigma modulator (DSM) transmitter architecture exhibits good coding efficiency and can be used for software-defined radio applications. However, the necessity of high clock speed is one of the major drawbacks of using this transmitter architecture. This study proposes a low-complexity timeinterleaved architecture for the polar DSM transmitter baseband part to reduce the clock speed requirement of the polar DSM transmitter using an upsampling technique. Simulations show that using the proposed four-branch timeinterleaved polar DSM transmitter baseband part, the clock speed requirement of the transmitter is reduced by four times without degrading the signal-tonoise-and-distortion ratio.

• Journal of electromagnetic engineering and science
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• 제11권2호
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• pp.128-132
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• 2011

In interference tolerance based spectrum sharing systems, primary receivers (PRs) are protected by a predefined peak or average interference power constraint. To implement such systems, cognitive radio (CR) transmitters are required to adjust their transmit power so that the interference power received at the PR receivers is kept below the threshold value. Hence, a CR-transmitter requires knowledge of its channel and the primary receiver in order to allocate the transmit power. In practice, it is impossible or very difficult for a CR transmitter to have perfect knowledge of this channel state information (CSI). In this paper, we investigate the impact of imperfect knowledge of this CSI on the performances of both a primary and cognitive radio network. For fixed transmit power, average interference power (AIP) constraint can be maintained through knowledge of the channel distribution information. To maintain the peak interference power (PIP) constraint, on the other hand, the CR-transmitter requires the instantaneous CSI of its channel with the primary receiver. First, we show that, compared to the PIP constraint with perfect CSI, the AIP constraint is advantageous for primary users but not for CR users. Then, we consider a PIP constraint with imperfect CSI at the CR-transmitter. We show that inaccuracy in CSI reduces the interference at the PR-receivers that is caused by the CR-transmitter. Consequently the proposed schemes improve the capacity of the primary links. Contrarily, the capacities of the CR links significantly degrade due to the inaccuracy in CSI.

• Journal of Ecology and Environment
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• 제46권3호
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• pp.183-189
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• 2022

Background: Radio-telemetry is a useful method to investigate the spatial ecology of species in the wild, by tracking the signal of a transmitter attached to an individual. The method of attaching a transmitter to a snake is representatively divided into surgical implantation, and external attachment, which latter is often used in small snake species. Results: In this study, we evaluated and compared the utility of two external attachment methods, the nylon thread method and the tape method, applied to a small grassland snake species of approximately 50 cm snout-vent length, the Slender racer (Orientocoluber spinalis), on an island in the Republic of Korea. The nylon thread method and the tape method were applied to four and five individuals, and radio-tracked for an average of eight and eleven days, respectively. The nylon thread method caused individual injury and disturbed their movement, while using the tape method, the transmitter package sometimes dropped off, but no injury or movement problems occurred. Conclusions: Considering that poor understanding of how to attach the transmitter makes it difficult to investigate the spatial ecology of small snake species, the tape method, evaluated in this study, could be applied to attach a transmitter and to study spatial ecology of such snakes.

• Journal of electromagnetic engineering and science
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• 제2권2호
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• pp.93-99
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• 2002

The Cartesian loop chip which is one of key devices in narrow-band Walky-Talky transmitter using RZ-SSB modulation method was designed and implemented with 0.35 Um CMOS technology. The reduced size and low cost of transmitter were available by the use of direct-conversion and Cartesian loop chip, which improved the power efficiency and linearity of transmitting path. In addition, low power operation was possible through CMOS technology. The performance test results of transmitter showed -23 dBc improvement of IMD level and -30 dEc below suppression of SSB characteristic in the operation of Cartesian loop chip (closed-loop). At that time, the transmitting power was about 37 dBm (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.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 통신소사이어티 추계학술대회논문집
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• pp.293-296
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• 2003

This paper evaluates the RF transmitting parameters of User Equipment(UE) for W-CDMA system based on 3GPP specifications. The parameters of transmitter are derived from the aspect of RF. In order to keep UE in high performance, the transmitter requirements such as ACLR, EVM, Peak Code Domain Error, spectrum emission mask are considered. The UE transceiver is implemented on the basis of performance requirements and then tested for the analysis of RF transmitter characteristics through test scenarios.

• 한국광학회:학술대회논문집
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• 한국광학회 2006년도 하계학술발표회 논문집
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• pp.363-364
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• 2006

We developed 60 GHz analog optical transmitter modules for radio-over-fiber (RoF). They were consisted of an electroabsorption modulator (EAM), impedance matching circuit, and amplifier. The characteristics of fabricated modules were investigated by measuring the signal-to-noise ratio and the noise figure of the 60 GHz RoF link.

• 한국습지학회지
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• 제16권1호
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• pp.85-92
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• 2014

한국에 서식하는 뱀목(Squamata) 중 살모사과(Viperidae)에 속하는 쇠살모사(Gloydius ussuriensis)와 까치살모사(Gloydius saxatilis)를 대상으로 무선추적기법을 이용한 행동권 연구를 수행하기 위해 모든 개체에게 체중 대비 5% 이내의 발신기를 삽입하였다. 쇠살모사 5개체, 까치살모사 6개체 총 11개체를 대상으로 발신기 삽입수술을 시행한 결과 쇠살모사의 경우 체중 대비 발신기 무게 비율은 평균 4.2%였으며, 까치살모사의 경우 평균 2.2%였다. 발신기삽입 후 회복기간 동안 까치살모사는 모두 생존한 반면 쇠살모사는 전체 5개체 중 4개체가 생존하지 못해 생존율이 20% 밖에 되질 않았다. 이전의 선행 연구들에서는 체중 대비 발신기 무게 비율을 1-7%까지 다양하게 권고하고 있지만, 이번 연구결과는 쇠사모사와 까치살모사의 행동생태 연구에서 이용되는 몸무게에 대한 발신기 무게 비율은 최소 3.6% 이내로 정해야 안전하다는 것을 보여준다.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2009년도 정보통신설비 학술대회
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• pp.242-247
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• 2009

In this paper, we investigate interference between short-range radiocommunication devices (SRDs) with frequency hopping spread spectrum (FHSS) and direct sequence spread spectrum (DSSS) methods when they are in the same frequency bands. In order to analyze interference from unwanted emission of SRD with DSSS to that of FHSS, Monte-Carlo (MC) simulation method is employed and interference probabilities are calculated. We simulate interference scenarios in accordance with several duty cycles and bandwidths. It is also assumed that the propagation model is free space The effect of distance between interfering transmitter and victim receiver is analyzed and bit error rate (BER) is simulated. From the interference analysis results, it is shown that duty cycle affects compatibility more than bandwidth does. Also, we can make sure of the separation distance which satisfies BER criterion when there are only one interfering transmitter and multiple interfering transmitters.

• 한국ITS학회 논문지
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• 제7권2호
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• pp.81-91
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• 2008

현재 무선 환경통신에서 점차 고갈되어가는 주파수를 효율적으로 사용하기 위해서 새로운 접근 방법이 개발되었다. Cognitive Radio는 디바이스가 동작하는 환경의 정보에 근거하여 자신의 송수신 방법을 바꿀 수 있는 장비를 말한다. 현재 무선 모바일 디바이스를 대상으로 하는 무선통신표준들은 절전모드에 대해서 다루고 있으며, 대부분 전력절감을 위하여 데이터 송신과 수신에 대한 전원을 차단하는 방법을 이용한다. 하지만 Cognitive Radio 환경에서는 모든 디바이스들이 채널을 검색하기 위해서 Quiet Period를 두고 있으며, 기존의 에너지 절감 방법으로는 Cognitive Radio 환경에 응용하기에는 적합하지 않다. 본 논문에서는 Cognitive Radio 환경에서 무선 모바일 디바이스를 위한 에너지 효율적인 MAC 프로토콜을 제안하고, 시뮬레이션을 통하여 일반적으로 사용되는 에너지관리 방법과 제안한 방법을 비교하여 성능이 향상되었음을 확인한다.

• 한국산업정보학회:학술대회논문집
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• 한국산업정보학회 2008년도 추계 공동 국제학술대회
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• pp.629-633
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• 2008

Recently, there has been great interest in the application of short-range wireless communication system. In this paper, the miniaturized FM transmitter with low power is developed, and laboratory tests have been carried out. The FM transmitter uses FM radio waves to send sound from any system (MP3, PMP, PDA, MP3 Phone et.) to any nearby radio or stereo system. The transmitter is designed with $2.6cm{\times}2.6cm{\times}2.6cm$ system size. The operating voltage is 3.7 V and used the built-in storage battery. The system can use continuously during 7 hour with once charging. The transmission frequency can select one of 88.1 MHz, 88.3 MHz, or 88.5 MHz in compliance with utility condition. The channel separation ability is 40 dB. The operating temperature is $-10{\sim}+85^{\circ}C$, which use in the industry environment. Consequently, this system sis used conveniently with short distance information transmitter system at the industry field.