• Journal of electromagnetic engineering and science
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• v.10 no.1
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• pp.39-44
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• 2010

In this paper, a compact wideband antenna with a band-notch function is proposed. It operates over the UWB band with a band-stop characteristic. To increase the impedance bandwidth, a ring-shaped radiator is used. By attaching a circular stub to the ring-shaped radiator, the band-notch performance is obtained. The proposed antenna operates over a frequency range from 2.7 GHz to 11 GHz to satisfy the 10-dB return-loss requirement and provides band-stop performance in the frequency band from 5.15 GHz to 6.1 GHz. Experimental results reveal that the proposed antenna exhibits good radiation performance and is suitable for UWB applications.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.533-534
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• 2008

This paper presents a multi-phase ring VCO for low-cost, low-power GPS receiver. In the RF band used in GPS, L1 band is now in commercial-use and L2,L5 are predicting to be commercial-use soon. Thus Wide band PLL and Cost-effective IC solutions are required for future multi-band GPS receiver that received three types band at once. A new PLL architecture for multi-band GPS application is proposed. Ring VCO is even smaller than LC-VCO and a good alternative for low-cost solution. Proposed multi-phase ring VCO offers wide frequency range covering L1, L2, and L5 band, 20% reduction of area, 23% reduction of PLL power and can generate I/Q without extra I/Q generator.

• Journal of the Optical Society of Korea
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• v.19 no.6
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• pp.673-678
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• 2015

Terahertz dual-band frequency selective surface filters made by perforating two different rectangular holes in molybdenum have been designed, fabricated and measured. Physical mechanisms of the dual-band resonant responses are clarified by three differently configured filters and the electric field distribution diagrams. The design process is straightforward and simple according to the physical concept and some formulas. Due to the weak coupling between the two neighboring rectangle holes with different sizes in the unit cell, good dual-band frequency selectivity performance can be easily achieved both in the lower and higher bands by tuning dimensions of the two rectangular holes. Three samples are fabricated, and their dual-band characteristics have been demonstrated by a THz time-domain spectroscopy system. Different from most commonly used metal-dielectric structure or metal-dielectric-metal sandwiched filters, the designed dual-band filters have advantages of easy fabrication and low cost, the encouraging results afforded by these filters could find their applications in dual-band sensors, THz communication systems and other emerging THz technologies.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.1400-1402
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• 2003

The objective of this paper is to determine the suitable spectral bands for monitoring growth status change during a long period. The long-term ground-level reflectance spectra as well as LAI and biomass were obtained in xiaotangshan area, Beijing, 2001. The narrow-band NDVI type spectral indices by all possible two bands were calculated their correlation coefficients R$^2$ with biomass and LAI. The best NDVIs must have higher R$^2$ with both biomass and LAI. The reasonable band centers and band widths were determined by a systematically increasing bandwidth centered over a wavelength. In addition, the first 19 bands of MODIS were simulated and investigated. Each developed spectral indices was then validated by the biomass and LAI time series using the generalized vector angle. It turned out that six new NDVI type indices within 750-1400nm were developed. NDVI(811_10,957_10) and NDVI(962_10,802_10) performed best. No satisfactory conventional NDVI formed by red and NIR bands were found effective. MODIS_NDVI(band19, band17) and MODIS_NDVI(band19, band2) were much better than MODIS_NDVI(band2,band1) for growth monitoring.

• Proceedings of the KSRS Conference
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• 2007.10a
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• pp.258-261
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• 2007

Although there have been lack of studies using X-band SAR data particularly for forestry application as compared to C-, and L-band SAR data, it has a potential to distinguish tree species because most signals are backscattered on the top of canopy. This study aimed to compare signal characteristics of multi-band SAR data including X-band for classifying tree species. The data used for the study are SIR-C/X-SAR data (X-, C-, L-band) obtained on Oct. 3, 1994 over the forest area near Seoul, S. Korea. Thirty ground sample plots were collected per each tree species. Initial comparison of backscattering coefficients among three SAR bands shows that X-band data showed better separation of tree species than C- and L-band SAR data irrespective of polarization. The weak penetrating in canopy layer might be possible source of information for X-band data to be useful for the classification of forest species and cover type mapping.

• Journal of the Optical Society of Korea
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• v.16 no.3
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• pp.288-291
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• 2012

We designed an ultra-wide band-pass filter applicable to microwave reflectometry for KSTAR (Korea Superconducting Tokamak Advanced Research) and to microwave photonics. The proposed ultra-wide band-pass filter exhibits a metamaterial structure characterized by a wide band, low insertion loss, and high skirt selectivity. The proposed filter is applied to enhance the linearity of reflectometry at the output of a VCO (voltage controlled oscillator). The pass-band of the proposed filter is observed at 18~28 GHz, and the out-of-band rejection is below 20 dB. Further, we constructed an unwrapped negative phase of S(2, 1) to verify the characteristics of the metamaterial. The under- and upper-band at lower limits of the pass-band are left- and right-handed, respectively. The group delay of the filter is less than 0.5 ns.

• ETRI Journal
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• v.36 no.4
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• pp.690-693
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• 2014

Compact multi-band bandpass filters using quad-mode stub-loaded resonators are proposed in this letter. Firstly, a novel approach about the mode-splitting characteristics of the quadruple-mode resonator is investigated, which can provide dual-band behavior. Secondly, a quad-band filter is proposed and designed by cascading two quadruple-mode resonators; the upper one operates at 1.8/2.4 GHz (GSM- and WiMax-band) and the lower one at 1.57/2.1 GHz (GPS- and WCDMA-band). Finally, the proposed filters have been fabricated. Respectable agreement between simulation and measurement verifies the validity of this design methodology.

• Journal of electromagnetic engineering and science
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• v.16 no.1
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• pp.19-23
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• 2016

This paper presents a novel design for dual-band bandpass filters. The proposed filters are applicable to the carrier aggregation of the TV white space (TVWS) band and long-term evolution (LTE) band for cognitive radio applications. The lower passband is the TVWS band (470-698 MHz) whose fractional bandwidth is 40 %, while the higher passband is the LTE band (824-894 MHz) with 8 % fractional bandwidth. Since the two passbands are located very close to each other, a transmission zero is inserted to enhance the rejection level between the two passbands. The TVWS band filter is designed using magnetic coupling to obtain a wide bandwidth, and the LTE band filter is designed using dielectric resonators to achieve good insertion loss characteristics. In addition, in the proposed design, a transmission zero is placed with cross-coupling. The proposed dual-band bandpass filter is designed as a two-port filter (one input/one output) as well as a three-port filter (one common input/two outputs). The measured performances show good agreement with the simulated performances.

• ETRI Journal
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• v.23 no.1
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• pp.1-8
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• 2001

The performance of a long wavelength-band erbium-doped fiber amplifier (L-band EDFA) using 1530nm-band pumping has been studied. A 1530nm-band pump source is built using a tunable light source and two C-band EDFAs in cascaded configuration, which is able to deliver a maximum output power of 23dBm. Gain coefficient and noise figure (NF) of the L-band EDFA are measured for pump wavelengths between 1530nm and 1560nm. The gain coefficient with a 1545nm pump is more than twice as large as with a 1480nm pump. It indicates that the L-band EDFA consumes low power. The noise figure of 1530nm pump is 6.36dB at worst, which is 0.75dB higher than that of 1480nm pumped EDFA. The optimum pump wavelength range to obtain high gain and low NF in the 1530nm band appears to be between 1530nm and 1540nm. Gain spectra as a function of a pump wavelength have bandwidth of more than 10nm so that a broadband pump source can be used as 1530nm-band pump. The L-band EDFA is also tested for WDM signals. Flat Gain bandwidth is 32nm from 1571.5 to 1603.5nm within 1dB excursion at input signal of -10dBm/ch. These results demonstrate that 1530nm-band pump can be used as a new efficient pump source for L-band EDFAs.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.4
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• pp.772-779
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• 2015

In this paper,a reconfigurable multi-band mobile antenna with switching line for LTE band 13, GSM, K-PCS, WCDMA band. The proposed antenna is planar strip line design and composed of stub shorted to the ground plane and two switching line for proposed band operation. To obtain the optimized parameters, we used the simulator, Using the obtained parameters is fabricated. The numerical and experiment results demonstrated that the proposed antenna satisfied the -6 dB impedance bandwidth requirement while simultaneously covering when the state of sw1 and sw2 on for LTE band 13, the state of sw1 off and sw2 on for GSM, K-PCS, the state of sw1 off and sw2 off for WCDMA. Respectively and characteristics of gain and radiation patterns are determined for a reconfigurable multi-band mobile terminal.