• Journal of Satellite, Information and Communications
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• v.10 no.3
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• pp.26-31
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• 2015

This paper deals with a size-reduced Ku-band waveguide limiter. Basically, it passes the signal from 16.125 GHz through 16.375 GHz, but when excessively high power is injected to the input port, it should change to a bandstop filter. Furthermore, it is required to change to bring attenuation by more than 20 dB and 50 dB over a narrow band and the entire passband, respectively. Therefore, in order to meet this requirement, a limiting device is implemented with multiple PIN-diode posts that enable the limiter to be the bandpass filter and stopband one at the off and on states of the PIN-diode switch, respectively. So, the design goes through the equivalent circuit modelling and the geometry is realized in the accurate electromagnetic analysis CAD tool. Finally, the result is discussed to shed light on whether it complies with the aforementioned requirement.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.4
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• pp.449-456
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• 2012

Herein, we design a wideband $8{\times}8$ waveguide Butler matrix in order to use in a multi-port amplifiers(MPAs) at Ka-band. To achieve the broadband characteristic, we design a binomial 6-slot 3 dB directional coupler which is used to configure the $8{\times}8$ Butler matrix. The measured results of the fabricated $8{\times}8$ Butler matrix have low insertion loss of less than 0.3 dB, good return loss of over 26 dB and high isolation of over 35 dB within the design bandwidth of 3 GHz.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.5
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• pp.971-978
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• 2018

This paper deals with the design and implementation of a limiter, which is a key component of the Ku-band radar system. The limiter design with the multi-pin diode switch was complemented by wideband signal attenuation, and realized the physical implementation. In the test result of implemented limiter, when the pin diode switch is all off, it is possible to transmit the incoming signal without distortion. Also when the pin diode switch is turned on sequentially, the input signal is attenuated about 20dB or more step by step. Finally when all of them were turned on, attenuation about 50dB or more were measured for a wide bandwidth(1000MHz) in Ku-band.

• The Journal of the Acoustical Society of Korea
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• v.43 no.4
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• pp.466-475
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• 2024

Matched-Field Processing (MFP) is a model-based approach that requires accurate knowledge of the ocean environment and array geometry (e.g., array tilt) to localize underwater acoustic sources. Consequently, it is inherently sensitive to model mismatches. In contrast, the waveguide invariant-based approach (also known as array invariant) offers a simple and robust means for source-range estimation in shallow waters. This approach solely exploits the beam angles and travel times of multiple arrivals separated in the beam-time domain, requiring no modeling of the acoustic fields, unlike MFP. This paper extends the waveguide invariant-based approach to shallow water environments featuring a shallow pit, where the waveguide invariant is not defined due to the complex bathymetry. An in-depth performance analysis is conducted using experimental data and numerical simulations.

• The Journal of the Acoustical Society of Korea
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• v.25 no.5
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• pp.239-245
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• 2006

Time-reversal processing (TRP) has been shown as an effective way to focus in both time and space. The temporal focusing properties have been used extensively in underwater acoustics communications. Recently. adaptive time-reversal processing (ATRP) was applied to the simultaneous multiple focusing in an ocean waveguide. In this study. multiple focusing with ATRP is extended to the underwater acoustic communication algorithm for multiple receiving locations. The developed algorithm is applied to the underwater acoustic communication to show, via simulation and real data, that the simultaneous self-equalization at multiple receiving locations is achieved.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.11
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• pp.1-9
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• 2003

The electromagnectic modal analysis method for the multiscreen structure with periodic slot array with including conductor thickness effect is presented. The multiscreen structure is seen to be exactly equivalent to a microwave guide closed by phase-shift walls. From this viewpoint, the entire generalized scattering matrix of the multiscreen structure is calculated by the cascade connection of the scattering matrices obtained by the modal analysis at guide junctions and the transmission matrices of guide region. The present method is verified in comparison with the results calculated by the previous method of moment for single screen structure. As an application example of the present method, the spatial filter having multiscreen structure is designed and the interesting characteristics such as transmission and reflection coefficient versus frequency & angle are investigated.

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

• The Journal of the Acoustical Society of Korea
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• v.25 no.6
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• pp.305-311
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• 2006

In this paper the performance of a array invariant method is evaluated for source-range estimation in horizontally stratified shallow water ocean waveguide. The method has advantage of little computationally effort over existing source-localization methods. such as matched field processing or the waveguide invariant and array gain is fully exploited. And. no knowledge of the environment is required except that the received field should not be dominated by purely interference This simple and instantaneous method is applied to simulated acoustic propagation filed for testing range estimation performance. The result of range estimation according to the SNR for the underwater impulsive source with broadband spectrum is demonstrated. The spatial smoothing method is applied to suppress the effect of mutipath propagation by high frequency signal. The result of performance test for range estimation shows that the error rate is within 20% at the SNR above 10dB.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.23 no.2
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• pp.163-168
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• 2023

In this paper, a novel platform for chemical sensing and biosensing is presented. The working principle is based on the coupling efficiency and interference properties of optical directional coupler (DC) and multimode interference coupler (MMIC). It has been realized using planar technology to allow integration on a silicon substrate. Firstly, the dispersion curves of DC and MMIC is described, and the design specification of an optimized slot optical waveguide to increase waveguide sensitivity is selected. Next, the sensor response to the refractive index change of sensing analyte is numerically simulated. The numerical results reveal that high effective index change per refractive index unit (RIU) change of analyte is obtained, and the sensitivity can be tuned using the DC and MMIC design technique.

• The Journal of the Acoustical Society of Korea
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• v.31 no.6
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• pp.373-383
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• 2012

The performance of underwater acoustic communication system is sensitive to the Doppler shift and ISI(Inter-Symbol Interference). Therefore, the simulation algorithm needs to consider time-spread due to multipath arrivals which cause the ISI, and time-varying Doppler shift along with moving source and receiver. For this purpose, VirTEX(Virtual Time series EXperiment) based on Ray model has been developed. In this paper, VirTEX is used to compare the characteristics of ocean waveguide from the experimental data and illustrate the performance. The CIR(Channel Impulse Response) that characterizes the multipath arrivals with representative time-spread due to multipath arrivals is compared between numerically simulated and experimental probe signal. Also, the communication performance analysis for BER(Bit Error Rate) is compared between numerically simulated and experimental data signal. As a result, VirTEX can be useful as a simulation tool for evaluating the performance of underwater acoustic communication system.