• Journal of the Korea Institute of Military Science and Technology
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• v.23 no.5
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• pp.459-465
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• 2020

In this paper, a compact antenna assembly for an amplitude comparison direction-finding(DF) method for a small flight vehicle is presented. Designed antenna assembly consists of four antennas and it is mounted on a radius of 1.45 λ_c where λ_c corresponds to the wavelength of the center frequency. To achieve compactness and robustness of the assembly, the elements are fed by end-launch feeding method and have modified aperture shapes of E- or H-sectoral horns. The feeding part consists of SMA connector, stepped impedance matching structure, and square waveguide of 0.6 λ_c × 0.6 λ_c. To achieve different main beam directions for every antenna which is required condition for amplitude comparison DF method, all apertures of the antennas are inclined and it makes the main beam direction of each antenna to top, bottom, left, and right with respect to the axis of the platform. To verify the validation of DF performance of the presented antenna assembly, amplitude comparison curves using measurement results are presented. The bandwidth of the antennas are above 3.2 % in Ku-band(VSWR ≤ 2:1).

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.23 no.1
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• pp.131-137
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• 2023

In this paper, a phase comparison direction finding method of circular array composed of 8 antennas considering polarization characteristics is analyzed. A broadband cavity-backed patch antenna operating in 6 ~ 12 GHz is used, and the antennas are arranged in radial direction to receive various polarization signals. For the phase comparison, widely spaced elements are used to obtain precise DOA(Direction of Arrival), and narrowly spaced elements are used to resolve ambiguity. Two dimensional direction finding is performed for ±20° in both azimuth and elevation, and the DOA error is less than 0.5° and 1.6° near the boresight and the ±15° region, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.4
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• pp.320-323
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• 2018

Herein, an ultrawideband spinning direction finding (DF) antenna was designed and fabricated for airborne applications. The proposed antenna is designed by dividing the low-band (UHF - L band) and high-band (S - Ka band) antennas to cover the ultrawideband frequency range (UHF - Ka band). For the high-band antenna, an LPDA antenna fed offset-parabolic-reflector antenna is applied. In the low-band antenna, two LPDA antenna elements are arrayed in front of the reflector of the high-band antenna without increasing to the full antenna size. The low- and high-band gains of the fabricated antenna were measured as 8.76 dBi and 24.55 dBi on average, respectively. The antenna was fabricated with the dimensions of 437 mm in diameter and 358 mm in height. Consequently, we confirmed that the designed antenna is appropriate for the spinning DF antenna in terms of the affordable size for installing on an airplane, as well as the high gain and narrow beamwidth.

• Journal of the Korea Convergence Society
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• v.6 no.5
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• pp.249-255
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• 2015

In this paper, we present an azimuth error analysis for the correlative interferometer direction finding. The correlative interferometer is a direction finding method that compares the theoretical and measured phase differences. The direction of the radio transmitter can be estimated by obtaining the maximum correlation between two data sets. We used a 5-element circular array antennas arranged in a circle. To derive the correlation function between antenna elements, we assume that the incident plane wave arrives from a certain angle and the phase difference of each antenna can be derived by comparing with the reference. The suggested direction finding gives a relatively accurate result even if the radio transmitter is located in the higher altitude.

• Geophysics and Geophysical Exploration
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• v.1 no.3
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• pp.176-182
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• 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 the Korea Institute of Military Science and Technology
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• v.11 no.6
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• pp.63-73
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• 2008

The helicopter position, heading data and the direction finding data of ESM are essentially required to compensate the parallax and analyze the direction finding accuracy of heliborne ESM in flight test phase. In the case of the long test range compared with small platform like as LYNX helicopter and Jisim Island test site, the parallax compensation for direction finding accuracy calculation and GPS position error can be neglected. In this paper, the direction finding accuracy on the basis of helicopter propeller was calculated by coordinate changing between helicopter and transmitting antenna from WGS84 coordinate to navigation coordinate using helicopter position and direction finding data.

• Journal of the Korea Institute of Military Science and Technology
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• v.10 no.3
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• pp.154-160
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• 2007

A direction finding system test-bed(DFSTB) at the electronic warfare communication-band is presented to efficiently evaluate and optimize the performance of the direction finding system through the indoor test setup. This test-bed gives a significant benefit to the designers of the direction finding system because it allows flexible test and design trade-off in the system design cycle. The system description and implementation of test-bed architecture, and the experiment results of direction finding accuracy according to modulation schemes are presented.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.4
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• pp.723-730
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• 2017

In this paper, we consider an online compensation algorithm considering the mutual coupling and suggest a new GPS antenna array to apply. To evaluate the anti-jamming performance for the proposed antenna array, ULA and URA, we divide direction finding of multiple jamming signals into environments. 1. there is no mutual coupling. 2. there is mutual coupling but no compensation. 3. mutual coupling is compensated. RMSE analysis showed that the online compensation algorithm works and that peak detection is possible for multiple jamming signals.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.9
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• pp.2157-2163
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• 2010

This paper includes the study of DOA(Direction of Arrival). CVDF(Correlative Vector Direction Finding) algorithm using at the phase difference each antenna needs to obtain ideal sinusoidal phase difference patterns. However, the phase difference patterns of circular array antennas may be interfered on a specific frequency band and to particular angle. The effect of installing each array antenna circularly and the effect of the interference by center pole (located in the center of a circular array antennas) may distort the phase difference patterns. This paper propose how to change the combination of antennas to measure phase difference patterns in real-time and how to use antenna beam patterns for minimizing the degradation phenomena with old CVDF algorithm. According to the test result, the capability of direction finding is improved.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.8
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• pp.913-921
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• 2007

In this paper, we propose a novel small antenna for direction finding applications. The proposed antenna employs a skirt type disk to eliminate the radiation null on the broad-side direction in the high frequency range. Additionally, the multi-section matching stub is used for impedance matching in the low frequency range, The size of the proposed antenna is reduced as a half of the 60cm dipole which has a same resonance frequency of 200MHz. The antenna maintains a donut shape radiation pattern with a broad beam width for a wide range of frequency while the 60cm dipole shows radiation nulls on the broad-side direction and the high side-lobe level from 700MHz to 1,300MHz.