• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.3 s.118
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• pp.305-314
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• 2007

In this paper, we suggested a CPW-fed UWB antenna with uni-planar sectoral structure. The area where radiation device face ground is designed to have the shape of tapered slot based on exponential function. We modified a rectangular bow-tie dipole structure antenna and thus formed a multi-resonant mode. From this, we expanded the impedance bandwidth and made a feature satisfying VSWR of less than 2 between $3.1\sim10.6GHz$. The test result showed that the return loss less than -10 dB was met in the full-band UWB system and maximum gain of $0.9\sim3.1dB$ was made with the half-power beamwidth of $40.1\sim89.9^{\circ}$ on XY plane(Theta, $Phi=90^{\circ}$) and the full band. By using CPW-fed structure with no ground on the back of the substrate, the suggested antenna is easy to design and its miniaturization is also possible.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.1C
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• pp.138-144
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• 2009

This paper proposes an efficient scheme to estimate the channel parameters such as channel gain and delay for the IEEE802.15.4a LR-UWB systems. Sliding window (SW) method is generally used for the channel estimation of LR-UWB systems, which extracts the channel parameters by performing the cross-correlation with the repeatedly transmitted signal. However, the SW method experiences the severe performance degradation because the cross-correlation is performed just once for the received signal. In this paper, we propose a novel channel estimation scheme, which can achieve a great performance gain by performing the cross-correlation repeatedly with the repeated receive signal. In order to verify the performance gain of the proposed scheme, we performed the intensive simulation with the Saleh-Valenzuela channel model. Simulation results show that the proposed scheme has a performance improvement of 4dB compared to the conventional SW channel estimation scheme.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.3
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• pp.275-281
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• 2011

In this paper, we proposed the small planar monopole antenna with modified ground plane for UWB communications. The proposed antenna not only shows Ultra-Wideband characteristic(3.1~10.6 GHz) suitable for UWB communications but has partially notched-band characteristic to reject 5 GHz WLAN band(5.15~5.35 GHz, 5.470~5.825 GHz). The proposed antenna improved impedance matching through two slits on ground plane, and the rejection band was induced by two ${\lambda}$/4 open stubs on center of two slits. Fabricated antenna satisfied VSWR${\leq}$2 in 2.88~10.83 GHz except for the band rejection of 5.08~5.83 GHz.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.8 no.1
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• pp.70-74
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• 2015

In this paper, we have illuminated the radiation modes of rectangular planar antennas to interpret the nature of the wideband characteristic upon which formulas for bandwidth prediction are presented. Rectangular planar antennas are being investigated by many researchers in virtue of relatively simple design and fabrication procedures to replace the cylindrical monopoles. But the design principle for rectangular planar antennas is still based on that of cylindrical monopoles, and the nature of the wideband characteristic and the formula to estimate the upper band frequency are not analyzed yet. In this research, we have shown the patterns of the radiation modes explaining the wideband characteristic and also proposed the upper band frequency with minor modification for the lower band frequency formula based on mode formation principles. Finally we have confirmed the validity of our results, within 10 % accuracy, by the application to some published results.

• Journal of Electrical Engineering and Technology
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• v.10 no.1
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• pp.338-343
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• 2015

In order to avoid the interference from existing narrowband communication systems, this paper proposes a compact band-notched UWB (ultra wideband) antenna with size of $12mm{\times}22mm{\times}1.6mm$. Transmission line model is applied to analyzing wide impedance matching characteristic of the modified base antenna, which has a gradual stepped impedance feeder structure. The proposed antenna realizes dual band-notched function by combining two biased T-shaped parasitic elements on the rear side with a window aperture on the radiation patch. The simulation current distributions of the antenna reflect resonant suppression validity of the two methods. In addition, the measured radiation characteristics demonstrate the proposed antenna prevents signal interference from WLAN (5.15-5.825GHz) and WiMAX (3.4-3.69GHz) effectively, and the measured patterns show the antenna omnidirectional radiation in working frequencies.

• Journal of the Korean Society of Marine Environment & Safety
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• v.14 no.4
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• pp.347-351
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• 2008

In this paper, a new co-planar waveguide ultra-wideband aperture is designed as wireless application in ships. The designed antenna consists of a rectangular aperture on a determined ground plane and a mushroom shaped stub. The mushroom-shaped stub, which is simple, convenient to analyze and optimise, has less parameters. This antenna has compact aperture size $21.1{\times}8.1mm^2$, designed on FR-4 substrate with dielectric constant of 4.3, thickness of 1.5mm. CPW fed planar antenna has the advantages of wide-bandwidth, low-cost and easy interaction with the radio frequency front end circuitry.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.9
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• pp.59-64
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• 2011

Ultra wideband radars attract considerable attention as a short range automotive radar because of its high range resolution. Radar signal reflected from a target often contains unwanted echoes called as clutter, so the detection of target is difficult due to clutter echoes. Therefore, it is important to investigate the radar detector for better detecting from the reflected signals. In this paper, the optimal detector is obtained for various mean and variance value in log-normal clutter environment. The types of non-coherent detectors used are square law detector, linear detector, and logarithmic detector. The performances of detectors are compared in log normal clutter environment and the suitable detector is determined for automotive short range radar application.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.303-307
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• 2008

In this paper, a new co-planar waveguide ultra-wideband aperture is designed. The designed antenna consists of a rectangular aperture on a determined ground plane and a mushroom shaped stub. The mushroom-shaped stub, which is simple, convenient to analyze and optimise, has less parameter. This antenna has compact aperture size $21.1{\times}8.1mm^2$, designed on FR-4 substrate with dielectric constant of 4.3, thickness of l.5mm. CPW fed planar antenna has the advantages of wide-bandwidth, low-cost and easy interaction with the radio frequency front end circuitry.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.3
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• pp.289-293
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• 2013

In the noncoherent methods for UWB-IR (ultra-wideband impulse radio), block coded modulation (BCM) is better than the transmitted reference (TR) systems in terms of the energy efficiency and data rate. However, even BCM suffers from the performance degradation in the presence of strong inter-frame interference and inter symbol interference. We propose the transmitted reference based on the BCM (TR-BCM) which is the hybrid system of TR and BCM. Performance evaluation shows that the performance of TR-BCM is better than that of BCM in the high SNR range.

• ETRI Journal
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• v.30 no.4
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• pp.526-534
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• 2008

This paper presents a fully integrated 0.13 ${\mu}m$ CMOS MB-OFDM UWB transmitter chain (mode 1). The proposed transmitter consists of a low-pass filter, a variable gain amplifier, a voltage-to-current converter, an I/Q up-mixer, a differential-to-single-ended converter, a driver amplifier, and a transmit/receive (T/R) switch. The proposed T/R switch shows an insertion loss of less than 1.5 dB and a Tx/Rx port isolation of more than 27 dB over a 3 GHz to 5 GHz frequency range. All RF/analog circuits have been designed to achieve high linearity and wide bandwidth. The proposed transmitter is implemented using IBM 0.13 ${\mu}m$ CMOS technology. The fabricated transmitter shows a -3 dB bandwidth of 550 MHz at each sub-band center frequency with gain flatness less than 1.5 dB. It also shows a power gain of 0.5 dB, a maximum output power level of 0 dBm, and output IP3 of +9.3 dBm. It consumes a total of 54 mA from a 1.5 V supply.