• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.3
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• pp.307-314
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• 2010

In this paper, a novel ultra-wideband microstrip-to-suspended stripline(SSL) transition is proposed, and SSL filters with low-loss and high selectivity have been realized using this transition. Since the proposed transition has low-loss and wide bandwidth characteristic, the design procedure of SSL filters become simplified. Additionally, the designed filters do not require extra time-consuming tuning. As design examples, SSL low-pass and high-pass filters have been implemented, and a implemented bandpass filter with connection of the low and high-pass filters performs 2.3~10.5 GHz bandwidth with less than 1.2 dB insertion loss and high selectivity.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.4
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• pp.494-500
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• 2020

This paper proposes a new distance estimation technique for indoor localization in ultra wideband (UWB) systems. The proposed technique is based on recurrent neural network (RNN), one of the deep learning methods. The RNN is known to be useful to deal with time series data, and since UWB signals can be seen as a time series data, RNN is employed in this paper. Specifically, the transmitted UWB signal passes through IEEE802.15.4a indoor channel model, and from the received signal, the RNN regressor is trained to estimate the distance from the transmitter to the receiver. To verify the performance of the trained RNN regressor, new received UWB signals are used and the conventional threshold based technique is also compared. For the performance measure, root mean square error (RMSE) is assessed. According to the computer simulation results, the proposed distance estimator is always much better than the conventional technique in all signal-to-noise ratios and distances between the transmitter and the receiver.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.10
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• pp.1290-1297
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• 2019

The paper proposes a distance estimation technique for ultra-wideband (UWB) systems using convolutional neural network (CNN). To estimate the distance from the transmitter and the receiver in the proposed method, 1 dimensional vector consisted of the magnitudes of the received samples is reshaped into a 2 dimensional matrix, and by using this matrix, the distance is estimated through the CNN regressor. The received signal for CNN training is generated by the UWB channel model in the IEEE 802.15.4a, and the CNN model is trained. Next, the received signal for CNN test is generated by filed experiments in indoor environments, and the distance estimation performance is verified. The proposed technique is also compared with the existing threshold based method. According to the results, the proposed CNN based technique is superior to the conventional method and specifically, the proposed method shows 0.6 m root mean square error (RMSE) at distance 10 m while the conventional technique shows much worse 1.6 m RMSE.

• Journal of information and communication convergence engineering
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• v.16 no.4
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• pp.252-257
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• 2018

A wideband double radiator circular disc annular monopole antenna is proposed is this work. The radiators are etched on the surfaces of two Taconic TLY-5 substrates with a circular hole cut out of each of the radiators initially at the centers of the radiators with subsequent downward displacement of the holes. The antenna is designed with a two-step feeding transformer system for impedance matching between the input power source supplied by a $50-{\Omega}$ SMA connector and the monopole radiators. The transformer system improves the bandwidth performance at higher frequencies. The proposed antenna achieves a wideband having the capability of working between 0.645 and 18.775 GHz, corresponding to a -10 dB bandwidth of 186.7% with gain ranging from 0.95 to 8.26 dBi. In comparison to other metal disc planar monopole antennas, the proposed antenna has a small total size width due to the size of the ground plane, which has a diameter 100 mm. The frequency range of the antenna provides applications in global positioning systems, mobile communications, ultra-wideband short distance communications, and wireless computer networks.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.11
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• pp.1178-1185
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• 2009

In this paper, a wideband ultra-high speed & high purity discrete frequency synthesizer having minimum 2.5 MHz step size was proposed. To achieve fast and wideband operation, discrete frequencies were synthesized by mixing of 3 different pre-synthesized 16 frequencies made from fixed PLL and frequency dividers. Frequencies with discrete 2.5 MHz step were produced in 710~1,610 MHz. The measured hopping response time was 350 nsec average, output level was 21.5 dBm average with 2.65 dB flatness, spurious and harmonics level were suppressed below -60 dBc, and phase noise was -94 dBc/Hz@100 Hz. Also, a new measurement method for synthesizer response time was described.

• Journal of Advanced Navigation Technology
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• v.24 no.6
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• pp.581-586
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• 2020

In this paper, the design process and method for a compact wideband loop antenna for terrestrial digital TV (DTV) and ultra high definition (UHD) TV applications was proposed. Horizontal slits were added on the two circular sectors of the proposed loop antenna in order to miniaturize the existing wideband loop antenna consisting of a square loop and two circular sectors. A CPW transmission line was inserted in the center of the lower circular sector as a feed line. The CPW feed line was designed using the 75 ohm port impedance for DTV and UHD TV applications, and a tapered center-signal line was designed to improve the impedance matching. The final designed antenna was fabricated on an FR4 substrate with a thickness of 0.8 mm. The experiment results show that the proposed compact loop antenna operates in the frequency band of 444.3-820.1 MHz for a VSWR < 2, which fully covers the DTV and UHD TV bands.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.12 s.115
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• pp.1156-1163
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• 2006

This paper presents an ultra wideband(UWB) direct conversion mixer for IEEE 802.15.3a applications with simulation and measurement results. Since the direct conversion mixing causes dc-offset and even-order distortion, the proposed mixer adopts an anti-parallel diode pairs(APDPs) to solve these problems. The proposed mixer consists of an in-phase wilkinson power divider over $3.1{\sim}4.8GHz$, a wideband $45^{\circ}$ power divider over $1.5{\sim}2.4GHz$, and miniatured band pass filters(BPFs) for RF-LO isolations. The conversion loss is optimized with impedance matchings between APDPs and wideband components. The measured mixer shows the conversion loss of 13.5 dB, input third-order intercept-point($IIP_3$) of 7 dBm, and 1-dB gam compression point($P_{1dB}$) of -4 dBm. Quadrature(I/Q) outputs have the magnitude difference of about 1 dB and phase difference of ${\pm}3^{\circ}$.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.10
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• pp.1837-1844
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• 2016

This paper proposes an antenna of the fork type structure that operates in the UWB (Ultra Wide Band) frequency band (3.1 ~ 10.6 GHz). The proposed antenna is attached a circular patch in order to obtain the UWB band characteristics to the fork-type patch antenna. The ground plane is implemented in a arc-shape configuration. The effect of various parameters of the modified fork type radiating patch and partial arc ground plane for UWB operation is investigated. The proposed antenna is made of $34.0{\times}50.0{\times}1.0mm^3$ and is fabricated on the permittivity 4.4 FR-4 substrate. The experiment results shown that the proposed antenna obtained the -10 dB impedance bandwidth 8200 MHz (2.7 ~ 10.9 GHz) covering the UWB bands. This result satisfied the characteristics of ultra-wideband and the proposed antenna will be applicable to an ultra wideband system.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.1489-1491
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• 2004

PD in air is accompanied by light, sound and electromagnetic wave. Light and sound can be prevented from blocking between PD sources and sensor but electromagnetic wave can be transferred to long distance without any interference an captured by antenna. This paper investigated the wideband antenna is appropriate for sensing Partial discharge in air. PD was generated from simulated PD source which consist of needle and flat electrode with small gap. Signals obtained from wideband antenna were diminished in both time and frequence region with the distance between PD source and antenna.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2002.11a
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• pp.413-422
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• 2002

A novel photonic bandgap(PBG) structure is proposed and measured for wide bandgap and compact circuit applications. The proposed structure realizes the ultra-wideband bandgap(2-octave) characteristics by superposing two different PBG structures into a coupled double-plane configuration. A low pass filter fabricated using 3-period of the PBG cells shows 2-octave 10 ㏈ stopband from 4.3 to 16.2 ㎓ and 0.2 ㏈ insertion loss in the passband. Moreover, we confirmed that 44∼70 % size reduction can be achieved using the proposed PBG structures. We expect this novel double-plane PBG structure is widely used for compact and wideband circuit applications, such as compact high-efficiency power amplifiers using harmonic tuning techniques.