• Journal of Positioning, Navigation, and Timing
• /
• v.5 no.1
• /
• pp.37-45
• /
• 2016

In this paper, design and implementation issues for a network-oriented RF emitter localization system with array antenna are discussed. For hardware, the problem of array mismatch and RF/IF channel mismatch are introduced and the calibration schemes for solving those problems are also provided. For software, it is explained how to overcome the drawback of conventional MUltiple Signal Identification and Classification (MUSIC) algorithm in a point of identifying the number of received signals and problems such as Data Association Problem and Ghost Node Problem in regard to multiple emitter localization are presented with some approaches for getting around those problems. Finally, for implementation, a criterion for arranging each of sensors and a requirement for alignment of array antenna' orientation are also given.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.26 no.7
• /
• pp.613-619
• /
• 2015

In this paper, we proposed a paper-based pattern-switchable antenna using inkjet-printing technology. The proposed antenna is composed of two bow-tie antennas and a switching network. The bow-tie antennas are inkjet-printed on paper using a low cost home printer. The switching network is built on a printed-circuit-board(PCB) and consists of a single-pole-double-throw(SPDT) switch and balun element. A double-sided parallel-strip line(DSPSL) can convert the unbalanced microstrip mode to the balanced strip mode. Two bow-tie antennas have different radiation patterns because of the different orientation of the reflectors. It is demonstrated from EM simulation and measurement that the radiation patterns of the proposed antenna are successfully switched by the SPDT.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2004.05a
• /
• pp.408-411
• /
• 2004

The presence of voids behind tunnel linings results in their deterioration. One proposed method of effectively detecting such voids by non-destructive means is radar. This research is devoted to quantitatively evaluating the efficiency of such non-destructive tests with radar. As a foundation to this ongoing research, which aims to acquire directional information and estimate the shape of specific voids using radar of three-dipole antenna type, an investigation of microwave polarization methods is carried out with various void orientations and void geometries. As the results, it is clarified that the response of microwave polarization modes depends on void geometry and thus there is a possibility of identifying the geometry and orientation of specific voids using radar of three-dipole antenna type.

• Journal of electromagnetic engineering and science
• /
• v.13 no.2
• /
• pp.86-92
• /
• 2013

The present paper defines diversity gain for stationary users. This deals in particular with gathering the received signal statistics over possible user positions and orientations in space rather than over time, and to define a meaningful diversity gain related to the cumulative improvement of the performances of the 1% users with the worst receiving conditions. The definition is used to evaluate diversity gain for some typical small antennas in an extreme environment with only line-of-sight (LOS). The LOS environment is regarded as user-distributed 3D-random LOS caused by the statistics of an ensemble of stationary users with arbitrary orientations in the horizontal plane (2D), and with arbitrary orientations of their wireless devices in the vertical plane. Thus, an overall 3D-random distribution of user orientation is assumed.

• Economic and Environmental Geology
• /
• v.57 no.1
• /
• pp.17-23
• /
• 2024

Ground penetrating radar (GPR) survey is a geophysical method that utilizes electromagnetic waves reflecting from a boundary where the electromagnetic property changes. As the frequency of the antenna is about 25 MHz ~ 1 GHz, it is effective to acquire high resolution images of underground pipe, artificial structure, underground cavity, and underground structure. In this study, we analyzed the change of signals reflected from the same underground objects according to the arrangement of transceiver antennas used in ground penetrating radar survey. The antenna used in the experiment was 200 MHz, and the survey was performed in the vertical direction across the sewer and the parallel direction along the sewer to the sewer buried under the road, respectively. A total of five antenna array methods were applied to the survey. The most used arrangement is when the transmitting and receiving antennas are all perpendicular to the survey line (PR-BD). The PR-BD arrangement is effective when the object underground is a horizontal reflector with an angle of less than 30°, such as the sewer under investigation. In this case study, it was confirmed that the transmitter and receiver antennas perpendicular to the survey line (PR-BD) are the most effective way to show the underground structure. In addition, in the case where the transmitting and receiving antennas are orthogonal to each other (XPOL), no specific reflected wave was observed in both experiments measured across or parallel to the sewer. Therefore, in the case of detecting undiscovered objects in the underground, the PR-BD array method in which the transmitting and receiving antennas are aligned in the direction perpendicular to the survey line taken as a reference and the XPOL method in which the transmitting and receiving antennas are orthogonal to each other are all used, it can be effective to apply both of the above arrangements after setting the direction to 45° and 135°.

• Journal of the Korea Concrete Institute
• /
• v.17 no.2 s.86
• /
• pp.221-227
• /
• 2005

The presence of voids behind tunnel linings is very likely to result in settlement or structural collapse. One proposed method of detecting such voids by non-destructive method is radar. More than effectively judging the existence of voids behind tunnel linings, this study aims to develop the analysis algorithm of radar capable of estimation of the shape of specific voids. To acquire directional information and estimate the shape of three-dimensional voids, the radar of three-dipole antenna type is used. As a foundation to this ongoing research, an investigation of microwave polarization methods using three-dipole antenna carried out with various void orientations and void geometries. As a result, it is clarified that the response of four microwave polarization modes depends on void geometry and thus there is a possibility of identifying the geometry and orientation (the shape) of specific voids using radar of three-dipole antenna type.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.24 no.7
• /
• pp.686-693
• /
• 2013

Based on a substrate integrated waveguide(SIW) and a complementary split ring resonator(CSRR), electrically small antennas are proposed in this paper. Antenna's electrical size is reduced by introducing both CSRR and the eighth-mode substrate integrated waveguide(EMSIW). The EMSIW occupies only 12.5 % of the conventional SIW at the same dominant resonant frequency. In addition, the resonant frequency of the antenna is varied by rotating the CSRR on the EMSIW while keeping the same radiation patterns. The resonant frequency is changed from 4.74 GHz to 5.07 GHz by varying orientation of the CSRR from 0 to 360 degree. Unidirectional radiation patterns are observed and the measured peak gains are from 4.50 to 5.92 dBi.

• Proceedings of the IEEK Conference
• /
• 2002.07b
• /
• pp.719-722
• /
• 2002

This paper reports the characteristics of a bidirectional antenna by using a planar array of a probe excited circular ring. The element of a bidirectional antenna is first designed to achieve the maximum directivity. The directivity can be further increased by arranging these elements to form the linear array. There are two types of linear array to be investigated i.e., on axis and off axis arrangement. On-axis linear array yields better directivity than off-axis linear array. Therefore, this orientation is further used to form the planar array. The radiation characteristics of this optimum planar array are rigorously reported. The proposed structure is very useful to extend the distance between the base station in PCT system.

• Geophysics and Geophysical Exploration
• /
• v.1 no.3
• /
• pp.176-182
• /
• 1998

The borehole radar reflection survey can image the underground structure with high resolution, however, we cannot get any information on the orientation of the reflectors with dipole antenna alone. The direction-finding antenna system is commonly used to give the solution to the problem. However, the interpretation of the data from direction- finding antenna may be time-consuming, and sometimes have ambiguities in the sense of precise determination of the azimuth. To solve the problem, we developed the automatic azimuth finding scheme of reflectors in borehole radar reflection data using direction-finding antenna. The algorithm is based on finding the azimuthal angle possibly showing the maximum reflection amplitude in the least-squared error sense. The developed algorithm was applied to the field data acquired in quarry mine. It was possible to locate nearly all of the reflectors in three dimensional fashion, which coincide with the known geological structures and man-made discontinuities.

• Journal of Institute of Control, Robotics and Systems
• /
• v.13 no.10
• /
• pp.949-955
• /
• 2007

This paper proposes an efficient localization algorithm in the RFID sensor space for the precise localization of a mobile robot. The RFID sensor space consists of embedded sensors and a mobile robot. The embedded sensors, that is tags are holding the absolute position data and provide them to the robot which carries a reader and requests the absolute position fur localization. The reader, it is called as antenna usually, gets several tag data at the same time within its readable range. It takes time to read all the tags and to process the data to estimate the position, which is a major factor to deteriorate the localization accuracy. In this paper, an efficient algorithm to estimate the position and orientation of the mobile robot as quickly as possible has been proposed. Along with the algorithm, a new allocation of the tags in the RFID sensor space is also proposed to improve the localization accuracy. The proposed algorithms are demonstrated and verified through the real experiments.