• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.07b
• /
• pp.616-619
• /
• 2003

This work presents the design, fabrication and microwave performance of distributed analog phase shifter (DAPS) fabricated on $(Ba,\;Sr)TiO_3$ (BST) thin films for X-band applications. Ferroelectric BST thin films were deposited on MgO substrates by pulsed laser deposition. The DAPS consists of high impedance coplanar waveguide (CPW) and periodically loaded tunable BST interdigitated capacitors (IDC). In order to reduce the insertion loss of DAPS and to remove the alteration of unloaded CPW properties according to an applied dc bias voltage, BST layer under transmission lines were removed by photolithography and RF-ion milling. The measured results are in good agreement with the simulated results at the frequencies of interest. The measured differential phase shift based on BST thin films was $24^{\circ}$ and the insertion loss decreased from 1.1 dB to 0.7 dB with increasing the bias voltage from 0 to 40V at 10 GHz.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.30 no.2C
• /
• pp.10-15
• /
• 2005

In this paper, a simple but fast and reliable technique for the complex dielectric constant measurement of non-magnetic materials is introduced using a measured transmission coefficient (S21) and a genetic algorithm as an inversion process at microwave frequencies. In this experiment, it has been found that the transmission method is less susceptible with the measurement errors than that of the reflection method and the genetic algorithm can be efficiently used as a search technique. The suggested technique is validated with known and unknown conductor-loaded lossy materials and the conductor-loaded PCB at X-band.

• Journal of Electrical Engineering and Technology
• /
• v.13 no.1
• /
• pp.406-412
• /
• 2018

In this paper, we propose a narrow resonant waveguide probe that can improve the measurement sensitivity in near-field scanning microwave microscopy. The probe consists of a metal waveguide incorporating the following two sections: a straight section at the tip of the probe whose cross-section is a double-ridged rectangle, and whose height is much smaller than the waveguide width; and a standard waveguide section. The advantage of the narrow waveguide is the same as that of the quarter-wave transformer section i.e., it achieves impedance-matching between the sample under test (SUT) and the standard waveguide. The design procedure used for the probe is presented in detail and the performance of the designed resonant probe is evaluated theoretically by using an equivalent circuit. The calculated results are compared with those obtained using the finite element method (Ansoft HFSS), and consistency between the results is demonstrated. Furthermore, the performance of the fabricated resonant probe is evaluated experimentally. At X-band frequencies, we have measured the one-dimensional scanning reflection coefficient of the SUT using the probe. The sensitivity of the proposed resonant probe is improved by more than two times as compared to a conventional waveguide cavity type probe.

• Korean Journal of Remote Sensing
• /
• v.10 no.2
• /
• pp.17-35
• /
• 1994

A semi-empirical model for microwave polarimetric radar backscattering from bare soil surfaces was developed using polarmetric radar measurements and the knowledge based on the theoretical and numerical solutions. The microwave polarimetric backscatter measurements were conducted for bare soil surfaces under a variety of roughness and moisture conditions at L-, C-, and X-band frequencies at incidence angles ranging from 10` to 70`. Since the accrate target parameters as well as the radar parameters are necessary for radar scattering modeling, a complete and accurate set of ground truth data were also collected using a laser profile meter and dielectric probes for each surface condition, from which accurate measurements were made of the rms height, correlation length, and dielectric constant. At first, the angular and spectral dependencies of the measured radar backscatter for a wide range of roughnesses and moisture conditions are examined. Then, the measured scattering behavior was tested using theoretical and numerical solutions. Based on the experimental observations and the theoretical and numerical solutions, a semi-empirical model was developed for backscattering coeffients in terms of the surface roughness parameters and the relative dielectric constant of the soil surface. The model was found to yield very good agreement with the backscattering measurements of this study as well as with independent measurements.

• Korean Journal of Soil Science and Fertilizer
• /
• v.45 no.4
• /
• pp.503-510
• /
• 2012

Microwave radar can penetrate cloud cover regardless of weather conditions and can be used day and night. Especially a A ground-based polarimetric scatterometer operating at multiple frequencies can continuously monitor the crop conditions. We analyzed scattering characteristics of rice and soybean using pauli decomposition method. Surface scattering (${\alpha}$) is the dominant component over the entire stages for all bands and pauli decomposition value was the highest for L-band. Double bounce scattering (${\beta}$) and volume scattering (${\gamma}$) were approximately equal for C-band and volume scattering was higher than double bounce scattering for X-band in rice field. In soybean, double bounce scattering becomes higher than volume scattering during the R2 stage (DOY 224) and there was a significant difference between the two components after the R4 stage (DOY 242) for L-band. The maximum growth stage of soybean can also be detected using L-band double bounce scattering. The peak of double bounce effect coincides with the peak of growth biophysical variables on DOY 271. We found that pauli decomposition can provide insight on the relative magnitude of different scattering mechanisms during the rice and soybean growth cycle.

• Proceedings of the Acoustical Society of Korea Conference
• /
• autumn
• /
• pp.433-438
• /
• 1999

This paper describes Active Noise Cancellation/Control(ANC) method that removes the information of the unnecessary noise and doesn't remove the informations of the necessary noise(warning sound, operating sound etc.) for the induced noise of the mechanical system. In this paper, the noise source Is axial fan, and the Feedback Active Noise control method that can effectively control BPF generated from the axial fan is used, and the Filtered-X LMS algorithm for adaptive algorithms is used. The experiments are executed for two case(propagating noise in the duct, emission noise for exterior free field). The part to be removed is BPF noise, and the band-pass filter not to effect to the other frequencies is used. Also, to investigate the effect of the noise reduction for human, we are compared with the results that are controlled for using Loudness before and after. As a results, we are certified that the BPF is decreased only and frequencies outside of BPF are not affected, and we acquire the reduction effects of 6.7 dB Loudness Level, then the frequency to be removed is controlled. Therefore, we can be certified that sound pressure as well as loudness can be effectively decreased for human sound quality

• Journal of Astronomy and Space Sciences
• /
• v.34 no.4
• /
• pp.303-314
• /
• 2017

With increased human activity in space, the risk of re-entry and collision between space objects is constantly increasing. Hence, the need for space situational awareness (SSA) programs has been acknowledged by many experienced space agencies. Optical and radar sensors, which enable the surveillance and tracking of space objects, are the most important technical components of SSA systems. In particular, combinations of radar systems and optical sensor networks play an outstanding role in SSA programs. At present, Korea operates the optical wide field patrol network (OWL-Net), the only optical system for tracking space objects. However, due to their dependence on weather conditions and observation time, it is not reasonable to use optical systems alone for SSA initiatives, as they have limited operational availability. Therefore, the strategies for developing radar systems should be considered for an efficient SSA system using currently available technology. The purpose of this paper is to analyze the performance of a radar system in detecting and tracking space objects. With the radar system investigated, the minimum sensitivity is defined as detection of a $1-m^2$ radar cross section (RCS) at an altitude of 2,000 km, with operating frequencies in the L, S, C, X or Ku-band. The results of power budget analysis showed that the maximum detection range of 2,000 km, which includes the low earth orbit (LEO) environment, can be achieved with a transmission power of 900 kW, transmit and receive antenna gains of 40 dB and 43 dB, respectively, a pulse width of 2 ms, and a signal processing gain of 13.3 dB, at a frequency of 1.3 GHz. We defined the key parameters of the radar following a performance analysis of the system. This research can thus provide guidelines for the conceptual design of radar systems for national SSA initiatives.

• Biomedical Science Letters
• /
• v.1 no.1
• /
• pp.9-18
• /
• 1995

Genetic polymorphisms due to variation in the number of tandem repeats of DNA sequences(VNTRs) provides a useful means for discrimination between individuals. Allele and genotype frequencies of the highly polymorphic Human Thyroid Peroxidase(TPO) gene were determined in Korean population samples by using PCR followed by polyacrylamide gel electrophoresis, a procedure called the amplified fragment length polymorphism(Amp-FLP) technique. In 123 unrelated Korean individuals 10 different alleles and 29 genotypes were observed. The TPO gene demonstrated a heterozygosity of 0.707 and the power of exclusion(POE) was 0.945. The probability of having the same DNA band within two unrelated individuals was 14.6$\times10^{-2}$. The distribution of observed genotypes conformed to Hardy-Weinberg equilibrium($x^2$=4.48, 0.05

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.39 no.3
• /
• pp.140-149
• /
• 2002

This paper describes the characteristics of beam-tilting slot away waveguide antennas for mobile DBS reception. As a basic study of slotted waveguide array, design for 16 slot elements located on a broad-wall waveguide is considered. Design parameters such as slot length, space between each slot and cross slot angle of antennas with the beam-tilting characteristics are calculated by method of moments. Based on these results, the radiation waveguide antennas with 16-element $\times$16-array are designed and fabricated. The measured main beam direction angles of the fabricated antennas are 48$^{\circ}$to 50$^{\circ}$depending on the measured frequencies and it shows good agreement with prediction. The measured 3 dB beam width of elevation pattern is about 13$^{\circ}$, and the axial ratio and the gain measured at DBS band are observed 2.8 dB below and 24 dBi above, respectively. In order to evaluate a performance of the fabricated waveguide planar antenna, it is combined with the satellite tracking control system and the field performance test of antenna mounted on a mobile vehicle is carried out at highway. During the measurement, it was possible to watch television without a break signal in a driving vehicle and an excellent performance of the proposed antennas was demonstrated.

• Korean Journal of Agricultural Science
• /
• v.8 no.2
• /
• pp.203-211
• /
• 1981

Mechanization of rice transplanting operation is very important project not only to solve the labor shortage problem at the so-called labor demand peak seasons of the rice transplanting, but also to reduce the production cost of rice by reducing the labor requirements. For these reasons this study was carried out to find the basic data for encourage the project of mechanization of rice transplanting. 381 sample farms were surveyed with questionaries and interviewed with a considerable number of relative personels about the operation, selecting and ownership trend of the rice transplanter. Collected data was analized by computer of Chungnam National University computer center applied to frequencies, cross- tabulation, $x^2$-test. The analized results of this survey are summarized as follows; 1. About 76.09% of the farmers interviewed was individual ownership of rice transplanter but about 52.27% of the farmers who wanted to purchase it in 2 or 3 years supported the cooperative ownership and utilization. This fact suggested that cooperative system of village level should be thoroghly studied. 2. The 93.33% of respondents gave the answer that the yield of rice was not affected by the planting methods between machine and manual. 3. The farmers who had a rice transplanter owned 4- row type rice transplanter with mat type seedling but the 25% of the farmers wanted to purchase it in 2 or 3 years wanted to own a 4 row type rice transplanter with band type seedling. Therefore the introduction of the 4-row type rice transplanter with band type seedling to rural area should be considered again. 4. The percent of farmers who wanted the cooperative system of village level was 49.57-57.83% of the farmers who had it already and wanted to own it in near future. It was strengthened by this fact that seedling nursely work was technically supported by the governmental level.