• International Journal of Contents
• /
• v.7 no.2
• /
• pp.6-10
• /
• 2011

The directional MAC (DMAC) protocol improves the spatial reuse, but directional packets on the control channel cause the deafness problem. In this paper, we propose a tone dual-channel DMAC protocol for mobile ad-hoc networks. In the proposed MAC protocol, the use of omnidirectional transmissions using an omnidirectional out-of-band tone solves the deafness problem and decrease packet collisions on the control channel. The use of an omnidirectional out-of-band tone also mitigates the hidden terminal problem. We use the negative CTS (NCTS) mechanism to solve the exposed terminal problem. The throughput performance of the proposed MAC protocol is confirmed by simulations using the Qualnet simulator.

• 한국정보통신설비학회:학술대회논문집
• /
• 2008.08a
• /
• pp.30-34
• /
• 2008

In this paper, we analyze the performance of pulse position modulation-time hopping ultra wide band (PPM-TH UWB) systems with antenna diversity technique in indoor wireless channel. A modified Saleh and Valenzuela (SV) model is adopted as a UWB indoor channel model. Perfect synchronization between a transmitter and a receiver is assumed. Therefore, coherent equal gain combining (EGC) scheme to collect the energy available in the multipath components is investigated. It is shown that the performance is improved by increasing the number of antennas at the receiver. The results of this paper can be applied to the applications of UWB.

• 한국정보통신설비학회:학술대회논문집
• /
• 2008.08a
• /
• pp.39-42
• /
• 2008

In this paper, we analyze the performance of ultra wide band (UWB) systems in indoor wireless channel in accordance with the number of pulses per bit at transmit signals and the decision types of receiver. The indoor channel is modeled as the modified Saleh and Valenzuela (SV) model which has been proposed as a UWB channel model by the IEEE group, IEEE 802.15.SG3a. Two types of UWB signals are considered One is the pulse position modulation-time hopping (PPM-TH) signal. And the other is the pulse amplitude modulation-direct sequence (PAM-DS) signal. It is assumed that the receiver is an ideal receiver which can receive all signals of the multipath.

• Journal of Advanced Navigation Technology
• /
• v.2 no.1
• /
• pp.53-60
• /
• 1998

This paper describes some design concepts and design parameters of RZ-SSB which allows full carrier insertion into the single side band to overcome the severe fading in aeronautical telecommunication, and it is described in ARINC Spec. in the name of AME(AM Equivalent), and the necessary transmission bandwidth of RZ-SSB is similar to that of a aeronautical telecommunication. As an amplitude limiter manage to remove the amplitude fading without degrading the quality of output signal, the receiver acts like the FM demodulators. Using the digital Signal Processing(DSP) techniques in the design of transceiver systems has become a performance enhancement of the signal quality and reliability, and making use of DSP, it's able to design low cost, compact transceiver and reduce its weight. For avionics systems is able to eliminate the inherent disadvantages in RZ-SSB, the results of experimental tests suggest that the adoption of RZ concepts is suitable for aeronautical telecommunication transceiver systems use in HF band.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.45 no.8
• /
• pp.53-59
• /
• 2008

In this paper, a novel dual-band high-efficiency class-F power amplifier using the composite right/left-handed (CRLH) transmission lines (TLs) has been realized with one RF Si lateral diffusion metal-oxide-semiconductor field effect transistor (LDMOSFET). The CRLH TL can lead to metamaterial transmission line with the dual-band tuning capability. The dual-band operation of the CRLH TL is achieved by the frequency offset and the nonlinear phase slope of the CRLH TL for the matching network of the power amplifier. Because the control of the all harmonic components is very difficult in dual-band, we have managed only the second- and third-harmonics to obtain the high efficiency with the CRLH TL in dual-band. Also, the proposed power amplifier has been realized by using the harmonic control circuit for not only the output matching network, but also the input matching network for better efficiency. Two operating frequencies are chosen at 880 MHz and 1920 MHz in this work. The measured results show that the output power of 39.83 dBm and 35.17 dBm was obtained at 880 MHz and 1920 MHz, respectively. At this point, we have obtained the power-added efficiency (PAE) of 79.536 % and 44.04 % at two operation frequencies, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.21 no.5
• /
• pp.537-543
• /
• 2010

This paper presents a slot-shaped defected ground structure(DGS) which has multi-band rejection property. The proposed structure, in which the spiral slot-shaped defects with different size are aligned in the transverse direction to the guiding direction of the coplanar waveguide(CPW), provides multiple resonance frequencies. Compared with the simulated results, the band rejection characteristic is in good agreement with the measurement. Also, an equivalent circuit model of the proposed structure is presented, where the DGS on the ground plane is modeled as LC-resonators. This resonators are inductively coupled to the signal line through mutual inductance. From the equivalent circuit model, multi-band rejection property was derived.

• 한국정보통신설비학회:학술대회논문집
• /
• 2008.08a
• /
• pp.3-6
• /
• 2008

In this paper, we propose the folded PIFA with its made an alteration to a factor of resonance for L-slot PIFA. Proposed antenna maintain diminished size patch and improve each bandwidth of GSM(0.88$\sim$-0.96 GHz) and W-CDMA(1.92$\sim$2,17 GHz) for miniaturized repeater. The non-slot step folded PIFA's structure that design of essence was general L-slot PIFA for dual-band. It has no U-slot, multi band and the another slot. The parameters of proposed antenna were optimized for dual-band and compact size by folded singleness patch. Proposed antenna by using folded singleness patch take satisfaction main point, bandwidth of GSM and W-CDMA, compact patch size($39{\times}21{\times}13mm^3$). The antenna was designed by FDTD simulation tool and it was made from result of simulation. Measured data shown that the proposed non-slot step folded PIFA was strong possibility.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.13 no.7
• /
• pp.3201-3206
• /
• 2012

In this paper, the simplified design methodology for rotation of polarization plane using a square waveguide is proposed. In order to optimize the characteristics of $180^{\circ}$ polarizer operating from 14.3GHz to 14.8GHz in Ku-band, the modified mode matching method and piecewise power tower interpolation are applied to the polarizer design. The optimized results show that the frequency bandwidth in VSWR<2 has covered 500MHz in the Ku-band and phase difference between two orthogonal modes $TE_{10}$and $TE_{01}$ is $180^{\circ}{\pm}1^{\circ}$ in the range of 14.3GHz~14.8GHz. The cross polarization loss has obtained below 40dB and the insertion loss has 0.1dB in the passband. Therefore, the proposed polarizer is suitable for practical Ku-band system requiring the low VSWR and compact size.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.14 no.6
• /
• pp.169-173
• /
• 2014

In order to satisfy user's requirements of needs for various services and to efficiently use of frequency, a communication system using one platform can support many communication services. Tunable filters must be used in the front end of broadband communication systems which provide and support various communication methods. In this paper we design and implement a filter bank to verify the feasibility of cavity tunable filter with the operation frequency of 800 MHz ~ 1600 MHz. The filter bank is composed of five bandpass filters and each bandpass filter has the same operation frequency band of the tunable filter. The implemented filter bank has the maximum insertion loss of 0.326 dB, the bandwidth of 37 MHz ~ 84 MHz, and the attenuation of minimum 19.974dB and mximum 37.812dB at the band edge ${\pm}60MHz$ over the operating frequency band.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.16 no.11 s.102
• /
• pp.1164-1170
• /
• 2005

This paper presents a dual-band, dual-polarized microstrip patch antenna with simple dual-probe feed. The inter-port isolation and cross-polarization are greatly improved by designing feed structure with annular gap between patch and feed-probe. Measured results show that the antenna's inter-port isolation and cross-polarization in each -10 dB return loss bandwidth of $1.84\;GHz\~l.93\;GHz$ and $2.62\;GHz\~2.81\;GHz$ are greater than 21 dB, greater than 22.2 dB and greater than 27 dB, greater than 19 dB, respectively. The antenna gain is about 6.9 dBi in both frequency bands.