• 한국정보통신설비학회:학술대회논문집
• /
• 2009.08a
• /
• pp.242-247
• /
• 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.

• Proceedings of the KIEE Conference
• /
• 2003.11c
• /
• pp.476-479
• /
• 2003

Recently, Bluetooth has been regarded as a new technology for short-range wireless connection. Although initial application of Bluetooth technology has been focused mainly on replacing cables between hand-held devices due to a limited packet size and short-range, general wireless telecommunication such as PAN and Ad hoc networks via Bluetooth-equipped devices is expected to be one of the most popular applications. Wireless equipments have been used to exchange data between host and mobile unit. The exchanging data may be several bytes of control command and the value of sensors with ultra-sonic, vision sensor, and encoder from mobile robot. However, most wireless equipments have some drawbacks such as lack of authentication, large size and high price. On the other hand, the benefits of Bluetooth are small size, low power, low price except short-range. Especially, there are some difficulties when wireless modules are used in indoor environments. In this paper, a method of using wire network in Bluetooth network is investigated as a solution to overcome the short-range problem of Bluetooth and difficulty in indoor environment.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.18 no.3
• /
• pp.260-266
• /
• 2015

The warship is run based on the combat system which shares tactical information collected by target detection systems and navigation devices across a network, and conducts the command and control of weapons from target detection to kill assessment. The short-range air defense missile system defends a warship from anti-ship missiles, aircraft, helicopter and other threats in order to contribute to the survival of a warship and the success of missions. The short-range air defense missile system is applied to a various combat systems. In this paper, we have proposed the interface design between the short-range air defense missile and dissimilar combat systems. To employ the short-range air defense missile at dissimilar combat systems, each system is driven by independent processor, and the tasks which are performed by each system are assigned. The information created by them is exchanged through the interface, and the flow of messages is designed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.19 no.2
• /
• pp.271-279
• /
• 2008

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 band-width 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.

• ETRI Journal
• /
• v.32 no.1
• /
• pp.112-119
• /
• 2010

We present a useful design for a free access mat which supports two frequency bands of 2.4 GHz and 5 GHz. The free access mat is a sheet-shaped waveguide which consists of a tightly coupled double-layered microstrip resonator array. It provides easy access for devices in short-range wireless communications. Interference is a common problem with conventional applications which use free space transmission. Our proposed wireless access system uses a subsidiary waveguide, the free access mat. Wireless devices are proximately coupled to the free access mat through which the coupled electromagnetic (EM) wave transmits. The arrival domain of the EM wave of an application is therefore limited to an area close to the free access mat. Wireless devices can be coupled to the free access mat at an arbitrary position without contact. We previously presented a free access mat for a single frequency band. This paper presents a free access mat for the two frequency bands of 2.4 GHz and 5 GHz. The free access mat uses a ring patch resonator array which is easily excited by typical antennas and is resistant to interference. These characteristics are demonstrated by numerical simulation and confirmed by experiment.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.8 no.1
• /
• pp.45-54
• /
• 1996

An experimental investigation on the two-phase flow through tube orifices was performed with the refrigerant mixture of R32/125/134a(30/10/60). A series of tests were conducted to generate wide range of data at varying operation conditions with four short tubes. The tests include both single and two-phase flow conditions at the inlet of the short tube with different oil concentrations. Experimental data were presented as a function of major operating parameters and short tube diameter. Based on test results and data analysis, a semi-empirical flow model was developed to predict the mass flow rate through short tube orifices with a given set of conditions. The flow model was formed to cover both single and two-phase flow at the inlet of short tube with considering the effects of oil concentration.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.08a
• /
• pp.67-67
• /
• 2012

Graphene, two-dimensional one-atom-thick planar sheet of carbon atoms densely packed in a honeycomb crystal lattice, exhibits fascinating electrical properties, such as a linear energy dispersion relation and high mobility in addition to a wide-range optical absorption and high thermal conductivity. Graphene's outstanding tensile strength allows graphene-based electronic and photonic devices to be flexible, bendable, or even stretchable. Recently many groups have reported high performance electronic and optoelectronic devices based on graphene materials, i.e. field-effect transistors, gas sensors, nonvolatile memory devices, and plasmonic waveguides, in which versatile properties of graphene materials have been incorporated into a flexible electronic or optoelectronic platform. However, there are several fundamental or technological hurdles to be overcome in real applications of graphene in electronics and optoelectronics. In this tutorial we will present a short introduction to the basic material properties and recent progresses in applications of graphene to electronics and optoelectronics and discuss future outlook of graphene-based devices.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.7 no.6
• /
• pp.1138-1145
• /
• 2003

The Bluetooth wireless technology is the new short-range RF transmission standard for low-power, low-cost, short-range radio links between mobile devices and electric product. The technology can eliminate the confusion of cables, connectors and protocols confounding communications between devices. Mobile phones, pagers, laptops, PDAs, digital cameras and more, all now have a common structure for communicating across their product platforms. In this paper, we present the Bluetooth protocol stack and headset profiles for the communication between mobile phone and headset. And then, we construct application software which is embedded in the device that operates an application over the Bluetooth protocol stack Next we implement wireless headset using MSP430, not real time operating system.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
• /
• v.12 no.4
• /
• pp.13-23
• /
• 2001

Recently, the demands on the short range radio device has been highly increasing, with the advantage of its mobility and improvement of its reliability which has been ensured by development of digital communication techniques. This study suggests the direction for the improvement of the national regulations in the technical, administrative and regulatory aspects, discussing the present situation of the regulations. While suggesting to launch the study on spectrum source and RE environments, we expect that several proposals in this paper will give a satisfaction on the development of strategy for spectrum management, development of radio technology and booming the short range radio communication.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.8 no.2
• /
• pp.170-177
• /
• 2008

In the present work a methodology to minimize short channel effects (SCEs) by modulating the effective channel length is proposed to design 25 nm single and double gate-source/drain underlap MOSFETs. The analysis is based on the evaluation of the ratio of effective channel length to natural/ characteristic length. Our results show that for this ratio to be greater than 2, steeper source/drain doping gradients along with wider source/drain roll-off widths will be required for both devices. In order to enhance short channel immunity, the ratio of source/drain roll-off width to lateral straggle should be greater than 2 for a wide range of source/drain doping gradients.