• Proceedings of the KSRS Conference
• /
• 2007.10a
• /
• pp.504-507
• /
• 2007

The KOMPSAT-2 satellite is a push-broom system with MSC (Multi Spectral Camera) which contains a panchromatic band and four multi-spectral bands covering the spectral range from 450nm to 900nm. The PAN band is composed of six CCD array with 2528 pixels. And the MS band has one CCD array with 3792 pixels. Raw imagery generated from a push-broom sensor contains vertical streaks caused by variability in detector response, variability in lens falloff, pixel area, output amplifiers and especially electrical gain and offset. Relative radiometric calibration is necessary to account for the detector-to-detector non-uniformity in this raw imagery. Non-uniformity correction (NUC) is that the process of performing on-board relative correction of gain and offset for each pixel to improve data compressibility and to reduce banding and streaking from aggregation or re-sampling in the imagery. A relative gain and offset are calculated for each detector using scenes from uniform target area such as a large desert, forest, sea. In the NUC of KOMPSAT-2, The NUC table for each pixel are divided as HF NUC (high frequency NUC) and LF NUC (low frequency NUC) to apply to few restricted facts in the operating system ofKOMPSAT-2. This work presents the algorithm and process of NUC table generation and shows the imagery to compare with and without calibration.

• Journal of Positioning, Navigation, and Timing
• /
• v.12 no.2
• /
• pp.101-111
• /
• 2023

Many spoofing detection studies have been conducted to cope with the most difficult types of deception among various disturbances of GPS, such as jamming, spoofing, and meaconing. In this paper, we propose a spoofing detection scheme based on elevation masked-relative received power between GPS L1 and L2 signals in a system using a multi-band array antenna. The proposed scheme focuses on enabling spoofing to be normally detected and minimizes the possibility of false detection in an environment where false alarms may occur due to pattern distortion among elements of an array antenna. The pattern distortion weakens the GPS signal strength at low elevation. It becomes confusing to detect a spoofing signal based on the relative power difference between GPS L1 and L2, especially when GPS L2 has weak signal strength. We propose design parameters for the relative power threshold including beamforming gain, the minimum received power difference between L1 and L2, and the patch antenna gain difference between L1 and L2. In addition, in order to eliminate the weak signal strength of GPS L2 in the spoofing detection process, we propose a rotation matrix that sets the elevation mask based on platform coordinates. Array antennas generally do not have high usefulness in commercial areas where receivers are operated alone, but are considered essential in military areas where GPS receivers are used together with signal processing for beamforming in the direction of GPS satellites. Through laboratory and live sky tests using the device under test, the proposed scheme with an elevation mask detects spoofing signals well and reduces the probability of false detection relative to that without the elevation mask.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.13 no.5
• /
• pp.860-867
• /
• 2009

In this paper, we designed the array antenna for FMCW radar in X - band frequency, and we chose stacked structure for improvement of narrow bandwidth. The array antenna is implemented on the circuit board which is relative permittivity 2.33 and the stacked patchs are designed on the circuit board which is relative permittivity 4.6. A Foam which has a similar permittivity of air is added to keep the particular gap between array antenna and the stacked patch. The result of array antenna has characteristics that a half-power beam width is $10.6^{\circ}$ and antenna gain is 18.70 dBi and bandwidth is 1.25GHz at the design frequency of 9GHz. The result of the array antenna with the stacked structure has that the half power beam width is $15.17^{\circ}$ and the antenna gain is 15.85dBi and bandwidth is 2GHz. It is needed to improve the antenna gain as keeping bandwidth in same level.

• Journal of Advanced Navigation Technology
• /
• v.20 no.3
• /
• pp.218-225
• /
• 2016

Null steering and beam steering are known well as anti-jamming methods in GPS anti-jamming system. Null steering gets a noise attenuation effect for the direction of jamming and beam steering earns additional gain synthesis for the direction of satellite signals. According to the research in the article for signal processing, it expresses that the N array antenna is effective for N-1 number of jamming signal by math public interest, however, the two algorithms analysis is not unknown for the operating condition of the realistic vehicle. In this paper, we modeled anti-jamming system using 4 and 7 array antenna and showed the two algorithms performance (PM, LCMV) when considering the number of antenna array, jammers and vehicle position (horizontal, vertical). In result, we showed that the case of vertical position of the vehicle which has large tilt angle for the relative position of satellites and jammers, has about 10 dB gain more in comparison with one of vertical position in spite of same JSR condition.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.16 no.11
• /
• pp.1063-1070
• /
• 1991

A microstrip array antenna are designed to depend on the size of rectangular microstrip patch for the relative current destribution to be 1:2:2:1 or 1:1:2:2:1:1 using Tchebyscheff polynominals, and it consist of sharp beam pattern. Gain difference between the main lobe and sidelobe is calculated for theoritical values of 21.97 db or 29.54 db. The designed microstrip array antenna are measureed various characteristics, such as return loss, resonant frequency, radiation pattern, bandwidth, beamwidth, and agreed with each other and theoretical value. Also it is presented a process of phase variation of patch array antenna depend on relative current distribution for beam scanning.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2006.05a
• /
• pp.77-81
• /
• 2006

We report the performance of a four-element, 11.67 GHz, high-Tc superconducting (HTS) microstrip antenna array with corporate feed network and circular polarization for direct broadcasting satellite (DBS) system. Our array antennas were designed and built on a 0.5 mm thick MgO substrate. To compare the superconducting antennas with normal conducting counterpart, One antenna pattern was fabricated from gold thin film, and a second pattern was fabricated from $YBa_2Cu_3O_{7-x}$ (YBCO) superconducting thin film. To improve the axial ratio of circularly polarized arrays, sequential rotation technique were used. Efficiency, radiation pattern, return loss and bandwidth were measured for both antennas at room temperature and at cryogenic temperature. The array produced good circular polarization, and the gain of the array at 77 K, relative to a copper array at room temperature was approximately 1.54 dB. The measured return loss of our HTS antenna array was 35.79 dB at the resonant frequency of 11.67 GHz and The total effective bandwidth was about 3.4 %. The results showed that high-temperature superconductors, when used in microstrip arrays, improved the efficiency of the HTS antenna array for circularly polarization.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.17 no.7
• /
• pp.776-781
• /
• 2004

We report the performance of a four-element, 11.67 GHz, $high-{T}_c$ superconducting (HTS) microstrip antenna array with corporate feed network. The HTS antenna array used in this work had a circular polarization for direct broadcasting satellite (DBS) system. Our array antennas were designed and built on a 0.5 mm thick MgO substrate. To compare the superconducting antennas with normal conducting counterpart, One antenna pattern was fabricated from gold thin film, and a second pattern was fabricated from ${YBa}_2{Cu}_3{O}_7-x(YBCO)$ superconducting thin film. To improve the axial ratio of circularly polarized arrays, sequential rotation technique were used. Efficiency, radiation pattern, return loss and bandwidth were measured for both antennas at cryogenic temperature and room temperature. The array produced good circular polarization, and the gain of the array at 77 K, relative to a copper array at room temperature was approximately 1.54 dB. The measured return loss of our HTS antenna array was 35.79 dB at the resonant frequency of 11.67 GHz and The total effective bandwidth was about 3.4 %. The results showed that high-temperature superconductors, when used in microstrip arrays, improved the efficiency of the HTS antenna array for circularly polarization.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
• /
• v.4 no.2
• /
• pp.34-40
• /
• 1993

A microstrip antenna for mobile system are designed at the resont frequency 0.88 GHz. The microstrip array antenna are designed to depend on the size of rectanular microstrip path for the relative current distribution to be 1:4.69:1 using Tchebyscheff polynominals. Gain difference between the main lobe and sidelobe is calculated for theoritical values of 20 dB. The designed microstrip array antenna are mesureed various characteristics, such as return loss, radiation pattern, V.S.W.R, bandwidth, and agreed with each other and theoretical value. Also it is presented a process of phase variation of patch array antenna depend on relative current distribution for beam scanning.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.51 no.10
• /
• pp.21-25
• /
• 2014

Scan capabilities of Fabry-Perot cavity (FPC) antennas are investigated for the case of a $4{\times}1$ thinned array placed inside the cavity. The FPC array antenna has higher maximum gain and lower sidelobe level (SLL), but the maximum scan angle of the thinned array is 14-17% lower than the patch array alone, due to increased mutual coupling in the FPC structures. However, unlike the bare thinned array, the SLL of FPC array does not suffer from the grating lobe problem even though it has a relative large element spacing of more than $1.0{\lambda}_0$.

• Proceedings of the IEEK Conference
• /
• 2000.07a
• /
• pp.163-166
• /
• 2000

The design, numerical simulation, and an experimental implementation of two-element cross-shaped microstrip line-fed printed slot array antenna for IMT-2000 at the 2.0 GHz band is presented in this paper. The proposed antenna with relative permittivity 4.3 and thickness 1.0mm is analyzed by the Finite-Difference Time-Domain (FDTD) method. It was shown that the measured 2.0 VSWR bandwidth of one-element microstrip slot antenna is from 1.42 GHz to 2.69 GHz, which is approximately 61.8% and that of two-element microstrip slot array antenna is from 1.42 GHz to 2.56 GHz, which is approximately 57.3% And it was shown that the measured gain of one-element microstrip slot antenna is 2.75 dBi and that of two-element microstrip slot antenna is 4.75 dEi. The antennas were fabricated and tested. The measured results are in good agreements with the FDTD results.