• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.2 s.105
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• pp.101-109
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• 2006

A broadband, DC to 40 GHz 5-bit MMIC digital attenuator has been developed. The ultra broadband attenuator has been achieved by adding transmission lines in the conventional Switched-T attenuator and optimizing the transmission line parameters. Momentum simulation was performed in design for accurate performance prediction at high frequencies and Monte Carlo analysis was applied to verify the performance stability against the MMIC process variation. The attenuator has been fabricated with $0.15\;{\mu}m$ GaAs pHEMT process. This attenuator has 1 dB resolution and 23 dB dynamic ranges. High attenuation accuracy has been achieved over all attenuation ranges and 40 GHz bandwidth with the reference state insertion loss of less than 6 dB at 20 GHz. The input and output return losses of the attenuator are better than 14 dB over all attenuation states and frequencies. The measured IIP3 of the attenuator is 33 dBm.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.6
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• pp.554-559
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• 2004

A novel miniaturized 2-pole band pass filter(BPF) is proposed and it has an overlapped hairpin and slot structure on the upper and bottom plane of microstrip lines. Due to the overlapped structure of a hairpin and a slot, the size of the proposed BPF is quite smaller than that of a general BPF having coupled lines. The size of the proposed BPF is reduced to 33 % comparing with the conventional λ/4 coupled BPF. The attenuation is improved by controlling the attenuation poles properly using the proposed structure. The proposed 2-pole BPF is fabricated with a narrow bandwidth(69 ㎒) at center frequency, 1.9 ㎓ which is difficult to make that narrow bandwidth in the conventional coupled lines due to impractical spacing. The design method in this paper can be applied to the design of other microwave circuits to reduce the size and improve the performances.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.8
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• pp.857-863
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• 2014

In determining interaction between plasma and electromagnetic wave, plasma frequency and collision frequency are two key parameters. They are derived from electron density and temperature, which vary in an extremely wide range, depending on a plasma generator. Because the parameters are usually unknown, traditional researches have utilized simplified electron density model and constant electron temperature approximation. Introduction of plasma fluid model to electromagnetics is suggested to utilize relatively precise time dependent variables for given generator. Dielectric barrier discharge(DBD) generator is selected due to its simple geometry which allows us to use one dimensional analysis. Time dependent property is analyzed when microwave is launched toward parallel plate DBD plasma. Afterwards, attenuation tendency with the change of electron density and temperature is demonstrated.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.6
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• pp.424-432
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• 2018

We herein analyze and study the shielding effectiveness characteristic of an open conveyor-belt-type microwave dryer that is widely used in industry. In particular, the electromagnetic wave leakage problem of the open-type conveyor belt dryer using a general-purpose 2.45-GHz magnetron was improved by applying the corrugated rectangular waveguide. We conducted the electromagnetic simulation of the optimal shielding effectiveness characteristic with regard to the proposed waveguide structure to analyze the attenuation characteristics of the corrugated rectangular waveguide. To verify the shielding effectiveness characteristic of the fabricated corrugated rectangular waveguide by IEEE standard 299, we achieved the shielding effectiveness of more than 30 dB in the practical microwave dryer with the proposed corrugated rectangular waveguide.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.7
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• pp.675-678
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• 2015

In this paper, we proposed a multi-function conversion block for microwave receiver. The proposed multi-function conversion block is composed of a broadband voltage controlled oscillator and a dual-mode mixer. Depending on whether the bias voltage is supplied, the first IF(Intermediate Frequency) output frequency(4,595 MHz/6,045 MHz) needed in microwave receiver is converted to 720 MHz and the another IF output frequency(720 MHz) for receiving Ku-band has the multi-functional operations of the dual mode that are bypass and attenuation without frequency conversion. Implementation and measurement results show that each intermediate frequency has conversion loss characteristic according to the LO power. The LO power conversion loss of 4,595 MHz at the LO levels from 2 dBm to 4 dBm is 13 dB, another of 6,035 MHz is 12 dB and the other of 720 MHz is 7.0 dB.

• Journal of electromagnetic engineering and science
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• v.8 no.2
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• pp.84-89
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• 2008

In a wireless channel above microwave frequency, rain attenuation is very important. In order to predict rain attenuation, 1-min. rain rate distribution is required. This paper discusses appropriate conversion methods to estimate 1-minute rain rate from that of other integration time. Based on the measurement data filed in ITU-R WP3J including ETRI data for 6 consecutive years, distributions of rain rate with 1-, 5-, 10-, 20-, 30-minute integration time were analyzed, both on the global and regional basis, and the parametric relationship between the statistical characteristics of 1-minute and other measurement data were investigated to deduce the conversion methods. It is shown that the global model works good with good accuracy for 5-, 10-, 20-min integration time, and the global model is also applicable globally with good accuracy for 5-, 10-, 20-min integration time. The global conversion model was adopted last year as an ITU-R document for new recommendation. The regional conversion model would also be very useful for locations of similar climatic zone.

• Journal of the Korea Institute of Military Science and Technology
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• v.12 no.4
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• pp.452-459
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• 2009

A 6-bit MMIC digital attenuator applicable to X-band TR module has been developed by using $0.5{\mu}m$GaAs pHEMT processes. The Switched-T attenuator scheme and the switched-path attenuator scheme were adopted to obtain low insertion loss and small phase variation, respectively. Resistors and transmission lines are optimized to achieve the digital attenuator with high attenuation accuracy and small phase variation. The digital attenuator has RMS error of 0.4dB, resolution of 0.5dB and dynamic range of 31.5dB. The measurement results show that in-out VSWRs are less than 1.5, phase variation is from -7 to +2 degrees and IIP3 is 36.5dBm.

• Journal of Advanced Navigation Technology
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• v.19 no.6
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• pp.607-613
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• 2015

In order to design M/W(microwave) short backhaul above 10 GHz to meet the increase in mobile traffic demand, the rain attenuation as well as the atmospheric conditions such as Earth bulge and Fresnel zone should be considered. In this paper, the path lengths have been estimated theoretically in various frequency bands using the Korean standard rain rate, and an example of path profile has been analyzed in urban area utilizing spectrum management intelligence system (SMIS). These derived minimum path lengths in various frequency bands are compared to the foreign them, and then will be proposed to improve the Korean minimum path length unitized to 10 km. This paper will provide useful information for microwave engineers in designing a M/W access link, and be utilized to make an efficient usage of high frequency bands for the short mobile broadband backhaul.

• Journal of the Korean Institute of Telematics and Electronics
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• v.21 no.1
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• pp.51-56
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• 1984

This paper describes the analysis and design of a GaAs FET distributed amplifier connecting a series capacitor to get a super wide bandwidth by reducing the gate line attenuation constant. In this approach a design example with a 300$\mu$ gate length FET devices is presented, and the abtained results are; that without series capacitors the bandwidth is 2-12 GHz, but with capacitors 2-20 GHz in flat gain.

• Journal of the Microelectronics and Packaging Society
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• v.9 no.1
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• pp.1-7
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• 2002

The purpose of this work is to develop High-Frequency Active Filter and super-miniaturation technology(SMD Type) of Filter which are essential for the key R/F Microwave components in the Mobile telecommunication system. The cut-off frequency of high frequency active filter for multimedia is 2.5 MHz, the gain is 0.5dB at 100 kHz, the passband ripple is 1.2 dB max at 100 kHz~2.0 kHz, GDT is 60 nsec at 100 kHz-2.0 MHz, the attenuation is 40 dB min at 3.75 MHz.