• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.1
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• pp.93-100
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• 2012

A telemetry signal occurs the line-of-sight problem by the effect of geography in flight test. A fixed relay system or a mobile relay system is used to solve that problem in general but we propose an airborne telemetry relay system using aircraft in this paper. An airborne telemetry relay system receives the telemetry signal of the test vehicle and then retransmits it to the ground system. The receiving antenna which is a phased array antenna can be tilted to ${\pm}30^{\circ}$ beam direction by beam-forming and track the rapidly moving test vehicle in effect. The relay pod which is mounted to an aircraft consists of the front antenna and the side antenna. It receives S-band signal and then down-converts the frequency to L-band signal. As a result, that can remove the frequency interference on an aircraft while retransmitting.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.4
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• pp.643-650
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• 2020

The phased array antenna has an advantage enabling rapid beam aim without the mechanical rotation of the antenna, because it arranges multiple elements in a linear or planer (grid or circular) and electronically controls the phase for each element. The planar array antenna is generally used a grid array and a circular array, and the circular form has the higher resolution comparing to the grid form due to the its structural characteristics. However, a concentric circular array (CCA) or a concentric ring array (CRA) with multiple circular arrays which each has different radius is used in the limited area, because the entire radius should be increased for the circular array with a number of elements. In this paper, we introduce the angle-of-arrival (AOA) estimator for an adaptive beamforming satellite system based on CRA and provide the simulation results for performance evaluation. In addition, simulation results are compared and analyzed to the case for the circular array antenna.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.3
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• pp.214-224
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• 2018

Continuous space development increases the occurrence probability of space hazards such as collapse of a satellite and collision between a satellite and space debris. In Korea, a space surveillance network with optical system has been developed; however, the radar technology for an independent space surveillance needs to be secured. Herein, an L-band phased array radar system for the detection and tracking of space objects is proposed to provide a number of services including collision avoidance and the prediction of re-entry events. With the mission analysis of space surveillance and the case analysis of foreign advanced radar systems, the radar parameters are defined and designed. The proposed radar system is able to detect a debris having a diameter of 10 cm at a maximum distance of 1,576 km. In addition, we confirmed the possibility of using the space surveillance mission for domestic satellites through the analysis of the detection area.

• ETRI Journal
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• v.24 no.3
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• pp.197-204
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• 2002

This paper presents the results of the numerical simulation of a multibeam active phased array antenna for a High Altitude Platform Station (HAPS). The simulation takes into account the random errors caused by the non-identity of the array elements and the inaccuracy of the antenna calibration. The results of our statistical simulation show that the strict requirements on the sidelobe envelope for HAPSs can be met when the amplitude and phase distribution errors are minor, a condition which may be achieved by using digital beamforming.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.12
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• pp.976-985
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• 2018

Modern radars such as the phase array radar can handle various tasks by generating a beam from a phased array antenna. Radar can be used for miscellaneous applications such as surveillance, tracking, missile guidance etc. Previous radar systems could handle only one task at a time. As such, multiple radars were required to perform simultaneous tasks. Multi-function radars can perform many tasks using only one radar system. However, the radar's resources are limited in this instance. To efficiently utilize time, it is necessary to properly schedule tasks in the radar's timeline. In this report, we investigate the efficiency of different scheduling tasks.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.8
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• pp.1110-1116
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• 2021

In this paper, we propose a conformal Ku-band data link antenna to ensure low RCS of stealth UAV. As a phased array antenna with electrical beam steering function, a transmitter and a receiver were designed and manufactured for FDD communication, respectively. Each antenna is designed as a 12*12 planar array antenna and has a function to form a uni-directional pattern and a bi-directional pattern through phase control of unit elements. The beam steering range is designed to be able to steer up to 60 degrees in theta direction and 360 degrees in the phi direction. As a result of manufacturing and measurement, the conformal type radome has low transmission loss and meets the required specifications including system performance. The feasibility of mounting the stealth UAV has been confirmed, and future research directions such as interworking of baseband devices and conversion to digital beam steering function are suggested.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.2
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• pp.19-29
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• 2004

In this paper, the beam steering dipole phased array antenna systems for IMT-2000 base station have been designed. The designed beam steering dipole phased array antenna systems are constituted by the antenna part and the beam steering control system part. The antenna part is designed by the proposed flat dipole for the broadband characteristics, and the 8${\times}$8 dipole way antenna is constructed by the Proposed flat dipole for the directional radiation pattern. Besides the vertical Power divider is designed for the vertical power distribution. The beam steering control system part is designed the horizontal power divider for the horizontal power distribution, the 4-bit phase shifters and the driving circuit of phase shifters for the horizontal beam tilting. In order to evaluate a performance of the designed antenna systems, they were fabricated and the radiation characteristics were measured. From the measured results, we found that the horizontal beams were tilted by the each control signals, and the measured radiation characteristics showed good agreement with the design goals.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.5
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• pp.504-514
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• 2014

An MMIC multi-function chip with a low DC power consumption for an X-band active phased array radar system has been designed and fabricated using a 0.5 ${\mu}m$ GaAs p-HEMT commercial process. The multi-function chip provides several functions: 6-bit phase shifting, 6-bit attenuation, transmit/receive switching, and signal amplification. The fabricated multi-function chip with a compact size of $16mm^2(4mm{\times}4mm)$ exhibits a gain of 10 dB and a P1dB of 14 dBm from 7 GHz to 11 GHz with a DC low power consumption of only 0.6 W. The RMS(Root Mean Square) errors for the 64 states of the 6-bit phase shift and attenuation were measured to $3^{\circ}$ and 0.6 dB, respectively over the frequency.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.9
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• pp.1-12
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• 1998

We have implemented receiver for a 3 Dimensional Phased-Array Radar detecting the azimuth angle, the altitude, the range of a target on real time. This system consists of high frequency module, which protects receiver and controls sensitivity, intermediate frequency module, monopulse detector, IQ phase detector, AGC controller. A two-channel receiver with same function is implemented for increasing accuracy of target altitude data by amplitude comparison monopulse method. The TSS sensitivity of the receiver is -98dBm. The bandwidth of the receiver is 500 MHz. We can control the system gain manually by 100 dB when be AGC off. The gain and phase unbalance of two channels is 5 dB and 30 degree, respectively. The image rejection rate of the IQ detector is 30 dB. We used duroid substrate and package- type device.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.2
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• pp.130-136
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• 2009

Turbine, which is one of major components in nuclear power plants, requires reliable nondestructive inspections. But, accessibility of transducers is limited and interpretation of acquired signals is not easy at all due to the complication. So, in this study, we have fabricated mock-up specimens of real size and shape. we applied pulse-echo method and time-of-flight diffraction(TOFD) method for precise inspection of turbine key and wheel bore. And phased array ultrasonic testing method was adopted for wheel dovetail of turbines by using mock-up. Furthermore, an automatic scanner system was developed for in-service inspection of the developed methods.