• 한국통신학회논문지
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• 제33권12A호
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• pp.1242-1250
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• 2008

본 논문에서는 AMPS 수신기에게 전파 간섭을 야기시킬 소출력 무선기기의 방사 전계강도를 예측하였다. 제시된 전계 강도 수치는 상호변조 간섭을 일으키지 않을 방사량의 상한치가 되며, 그 수치는 79.13[$dB{\mu}V/m$]이었다. 이 상한치의 타당성을 보이고자 상호변조에 근거된 이론 제시, AMPS 수신기의 모델링, 및 해당 IC에 대한 측정을 수행하였다. 그 결과 삼자 간의 수치들은 허용된 범위 내에서 잘 일치됨을 확인할 수 있었다.

• 전자공학회논문지
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• 제53권9호
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• pp.62-66
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• 2016

본 논문에서는 의료기기용 MedRadio 대역의 저전력 저잡음 증폭기를 제안한다. 제안한 저잡음 증폭기는 전류 재사용 저항 피드백 증폭기 구조를 채택하여 $g_m$을 증폭시키고 소스 인덕터 없이 입력 매칭을 가능하도록 하였다. 추가적으로 제안한 직렬 저항, 인덕터, 커패시터 입력 매칭 네트워크의 Q-factor를 통해 저잡음 증폭기의 전압 이득을 증가시켜 잡음 지수를 최소화 했다. 로드저항이 없는 구조를 채택하여 낮은 전원 전압으로 전력 소모를 줄였다. 제안한 MedRadio 대역 저전력 저잡음 증폭기는 $0.13{\mu}m$ CMOS 공정을 사용하여 설계하였고, 전원 전압 1 V에서 0.18 mA의 전류를 소모하면서 0.85 dB의 잡음 지수, 30 dB의 전압 이득, -7.9 dBm의 IIP3의 성능을 보인다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.1826-1829
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• 2005

Recent advancement in wireless communications and electronics has enabled the development of low power sensor network. Wireless sensor network are often used in remote monitoring control applications, health care, security and environmental monitoring. Wireless sensor networks are an emerging technology consisting of small, low-power, and low-cost devices that integrate limited computation, sensing, and radio communication capabilities. Sensor network platform for health care has been designed, fabricated and tested. This system consists of an embedded micro-controller, Radio Frequency (RF) transceiver, power management, I/O expansion, and serial communication (RS-232). The hardware platform uses Atmel ATmega128L 8-bit ultra low power RISC processor with 128KB flash memory as the program memory and 4KB SRAM as the data memory. The radio transceiver (Chipcon CC1000) operates in the ISM band at 433MHz or 916MHz with a maximum data rate of 76.8kbps. Also, the indoor radio range is approximately 20-30m. When many sensors have to communicate with the controller, standard communication interfaces such as Serial Peripheral Interface (SPI) or Integrated Circuit ($I^{2}C$) allow sharing a single communication bus. With its low power, the smallest and low cost design, the wireless sensor network system and wireless sensing electronics to collect health-related information of human vitality and main physiological parameters (ECG, Temperature, Perspiration, Blood Pressure and some more vitality parameters, etc.)

• Journal of electromagnetic engineering and science
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• 제14권4호
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• pp.353-359
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• 2014

Recently, the use of mobile devices has increased, and mobile traffic is growing rapidly. In order to deal with such massive traffic, cognitive radio (CR) is applied to efficiently use limited-spectrum resources. However, there can be multiple communication systems trying to access the white space (unused spectrum), and inevitable interference may occur to cause mutual performance degradation. Therefore, understanding the effects of interference in CR-based systems is crucial to meaningful operations of these systems. In this paper, we consider a long-term evolution (LTE) system using additional spectra by accessing the TV white space, where low-power devices (LPDs) are licensed primary users, in addition to TV broadcasting service providers. We model such a heterogeneous system to analyze the co-existence problem and evaluate the interference effects of LPDs on LTE user equipment (UE) throughput. We then present methods to mitigate the interference effects of LPDs by 'de-selecting' some of the UEs to effectively increase the overall sector throughput of the CR-based LTE system.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2009년도 정보 및 제어 심포지움 논문집
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• pp.290-292
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• 2009

With advance in technologies for wireless sensor networks(WSNs), 2.4 GHz band has become gradually attractive due to increase in low-power wireless communication devices. Especially ZigBee(IEEE 802.15.4-based) technology whose frequency band includes the 2.4GHz industrial, scientific and medical band providing nearly worldwide availability has been universally applicable to a various remote monitoring system and applications related home network system. However network throughput of these systems is significantly deteriorated due to this ISM band is a license-exemption used in a variety of low-power wireless communication devices. For instance, other IEEE 802 wireless standards such as Bluetooth, WLAN, Wi-Fi and others cause radio interference to ZigBee. The experiments was carried out to analyze radio frequency interference between heterogeneous devices using ISM bands to improve the limited frequency utility factor. Finally this paper suggests a frequency hopping-based adaptive multi-channel methods to decrease interference with empirical results.

• Smart Structures and Systems
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• 제14권4호
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• pp.617-641
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• 2014

The energy constraint is still a common issue for the practical application of wireless sensors, since they are usually powered by batteries which limit their lifetime. In this paper, a practical compound energy efficiency strategy is proposed and realized in the implementation of a real time wireless sensor platform. The platform is intended for wireless structural monitoring applications and consists of three parts, wireless sensing unit, base station and data acquisition and configuration software running in a computer within the Matlab environment. The high energy efficiency of the wireless sensor platform is achieved by a proposed adaptive radio transmission power control algorithm, and some straightforward methods, including adopting low power ICs and high efficient power management circuits, low duty cycle radio polling and switching off radio between two adjacent data packets' transmission. The adaptive transmission power control algorithm is based on the statistical average of the path loss estimations using a moving average filter. The algorithm is implemented in the wireless node and relies on the received signal strength feedback piggybacked in the ACK packet from the base station node to estimate the path loss. Therefore, it does not need any control packet overheads. Several experiments are carried out to investigate the link quality of radio channels, validate and evaluate the proposed adaptive transmission power control algorithm, including static and dynamic experiments.

• 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.

• 한국전자파학회논문지
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• 제17권6호
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• pp.574-586
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• 2006

최근 세계 무선 통신 환경은 선진국가별로 다양한 통신 기술에 대한 기준 마련 및 표준화가 진행되고 있다. 이에 따른 통신 환경 변화에 대처하기 위하여 국내에서도 여러 분야에 걸쳐 다양하게 기술 기준 및 표준화에 대한 연구가 진행되고 있다. 본 연구에서는 미약 무선국의 전계 강도(기술 기준)에 대한 현재 각국의 동향과 그 기준치를 연구 분석하고, 파악함과 동시에, 또한, 전자파 적합 등록에서 제시하고 있는 각국의 전계 강도 기준치와 연계하여 이에 적합한 국내의 비허가 무선 기기(미약 무선 기기)의 실질적인 도입 가능한 전계 강도의 기준치를 제시함을 목적으로 한다. 여기에서 제시한 전계 강도 허용치를 바탕으로, 미약 무선 기기의 보급과 발전에 기여할 것으로 예상되며 국내 통신 시장은 물론 국제 통신 시장에서 경쟁력을 갖출 수 있을 것으로 예상된다.

• 한국산학기술학회논문지
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• 제13권2호
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• pp.790-794
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• 2012

소출력 무선설비로부터 발사되는 전파로 인한 혼신으로부터 다른 무선국을 보호하기 위해 사용 주파수에 따라 출력 강도를 제한하고 있으며, 수신기의 경우에는 불요 발사 전력을 규제하고 있는데, 국내의 경우에는 1GHz이하의 소출력 무선설비의 수신기의 부차적인 전파 전력에 관한 규정은 -54dBm으로 규정되어, 1GHz 이상의 소출력 무선설비의 경우에는 아직 그 규정이 마련되어 있지 않고 있다. 현재 1GHz 이상의 기기들이 통신시장의 확대로 인해 서비스가 증가하고 있어 국내 기준이 필요 상태이다.

• International journal of advanced smart convergence
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• 제7권3호
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• pp.23-36
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• 2018

In wireless communication, efficient spectrum usage is an issue that has been an attractive research area for many technologies. Recently new technologies innovations allow compact radios to transmit with power efficient communication over very long distances. For example, Low-Power Wide Area Networks (LPWANs) are an attractive emerging platform to connect the Internet-of-Things (IoT). Especially, LoRa is one of LPWAN technologies and considered as an infrastructure solution for IoT. End-devices use LoRa protocol across a single wireless hop to communicate to gateway(s) connected to the internet which acts as a bridge and relays message between these LoRa end-devices to a central network server. The use of the (ISM) spectrum sharing for such long-range networking motivates us to implement spectrum sensing testbed for cognitive radio network based on LoRa and GNU radio. In cognitive radio (CR), secondary users (SUs) are able to sense and use this information to opportunistically access the licensed spectrum band in absence of the primary users (PUs). In general, PUs have not been very receptive of the idea of opportunistic spectrum sharing. That is, CR will harmfully interfere with operations of PUs. Subsequently, there is a need for experimenting with different techniques in a real system. In this paper, we implemented spectrum sensing for cognitive radio networks based on LoRa and GNU Radio, and further analyzed corresponding performances of the implemented systems. The implementation is done using Microchip LoRa evolution kits, USRPs, and GNU radio.