• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.5
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• pp.355-365
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• 2017

In this paper, we propose the design of a dual-band GPS antenna using in-direct feeding pads. The antenna consists of an upper patch for the GPS L1 band, a lower patch for the GPS L2 band, and two pads on the middle layer for feeding the two radiating patches. A hybrid chip coupler with a phase difference of $90^{\circ}$ is employed at the two feeding ports for achieving a broad circular polarization (CP) bandwidth. The proposed antenna shows bore-sight gains of 3.0 dBic(L1) and 5.1 dBic(L2), and axial ratios of 3.3 dB(L1) and 0.3 dB(L2) by measurement. The active element patterns of the fabricated array with 7 elements show bore-sight gains of -0.4 dBic (L1) and -2.4 dBic(L2), respectively. It proves that the proposed antenna structure is suitable for use in GPS array applications.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2015.11a
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• pp.43-44
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• 2015

LTE-Advanced system has been deployed with 2 and 4 transmission antennas (Tx) while the specification supports up to 8Tx. Due to deployment space, antenna dimension and complexity, the needs of deploying 8Tx system has not been motivated by operators. Recently, three dimensional (3D) beamforming with active antenna has attracted significant attention in the wireless industry. By incorporating 2D active array into LTE-A systems, the system offers freedom in controlling radiation on elevation and horizontal dimension. When the number of antennas increases in the form of 2D arrangement, spatial separation can be realized simultaneously in horizontal and elevation domain and vertical beam-steering can increase SINR of UEs in high floors. In this paper, we study the system operations and implementations for supporting 3D beamforming with 8Tx antennas. In our schemes, by reusing the conventional CSI feedback framework, the system can operate 2D active array without harming the backward compatibility. Evaluation results show that 3D beamforming provides capacity boosting over the conventional 2D beamforming systems while keeping same antenna structure.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.7
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• pp.903-908
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• 1999

In this paper, it is proposed the phase shifter array active system to receive digital satellite broadcasting for vehicle. To receive satellite broadcasting data in vehicle, it is inevitable to have active antenna system, which traces the satellite in real time. Also if it is used in vehicle, it must be thin and light structure. To develop this type of antenna system, several techniques should be integrated properly. These are the design and manufacturing technique of high gain antenna, algorithm for tracking satellite and its manufacturing technique, controller design and manufacturing technique, system integration technique and so on. The validity of the proposed AVDBS system was confirmed by simulation and experimental results.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.1
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• pp.61-68
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• 2018

In this paper, we described about methods and results to verify the Tx/Rx beam characteristics of a planar active phased array antenna as using a near-field measurement. The near-field system can effectively measure multiple beams and predict the performance degradation due to the partial failure of individual elements. Also, it can accurately predict the EIRP relating to detection performance of the active phased array radar. We briefly described the near-field measurement method to verify the Tx/Rx beam characteristics, and then verified the effectiveness of measurement method by analyzing the measured results.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.535-539
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• 2010

This paper include to study DoA(Direction of Arrival) for radio collection and monitoring system. The direction finding calculated by applying the CVDF (Correlation Vector Direction Finding) algorithm for the five circular dipole antenna over V / UHF band. To improve the accuracy of direction finding by applying CVDF algorithm needs to obtain ideal phase difference each antennas. However, a circular array antenna phase difference pattern may be distorted on a specific frequency band or to particular direction. The effect of installing each array antennas circularly and the effect of the interference of center pole (located in the center of a circular array antenna mount) may make the distortion of phase pattern. If you use an active antenna instead of passive antenna to obtain good sensitivity, you would measure the more distortion. This paper propose how to change combination of antennas to measure the phase in real-time and how to use antenna beam patterns for minimizing the degradation phenomena at applying simple CVDF algorithm and increasing the direction finding capability.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.3
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• pp.158-160
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• 2014

Recently, owing to the development of active array antenna techniques, various sector beams can be applied to the LTE systems with vertical sectorization. In this paper, we evaluate the system performance and suggest an optimum beam combination and parameters by using a system level simulator

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.5 s.108
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• pp.461-475
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• 2006

In this paper, it is described about the tri-band mobile antenna system design to provide broadband multimedia and direct broadcasting services using goo-stationary Koreasat 3, simultaneously operated in Ka/K/Ku band. The radiating part of the antenna system with a fan beam characteristic in the elevation plane is composed of the quasi-offset dual shaped reflector and the tri-band feeder. The tri-band feeder is also composed of the Ka/K dual band feeder with the protruding dielectric rod, the circular polarizer, the ortho-mode transducer and the circular-polarized Ku band feed array. Especially, the Ka/K dual band circular polarizer was realized firstly using the comb-type structure. For fast satellite-tracking on the movement, the Ku band feed array has the structure of the $2{\times}2$ active phased array which can make electrical beams. And, the circular-polarized characteristic in the feed array was improved by $90^{\circ}$ rotating arrangement of four radiating elements polarized circularly by a $90^{\circ}$ hybrid coupler, respectively. Four beam forming channels to make electrical beams at Ku band are divided into the main beam channel and the tracking beam channel in the output, and noise temperature characteristics of each channel were analyzed on the basis of the contributions of internal sub_units. From the fabricated antenna system, the output power at $P_{1dBc}$ of Ka_Tx channel was measured more than 34.1 dBm and the measured noise figures of K/Ku_Rx channels were less than 2.4 dB and 1.5 dB, respectively, over the operating band. The radiation patterns with co- and cross-polarization in the tri-band were measured using a near-field measurement in the anechoic chamber. Especially, Ku radiation patterns were measured after correcting each initial phase of active channels with partial radiation patterns obtained from the independent excitation of each channel. The antenna gains measured in Ka/K/Ku band of the antenna system were more than 39.6 dBi, 37.5 dBi, 29.6 dBi, respectively. And, the antenna system showed good system performances such as Ka_Tx EIRP more than 43.7 dBW and K/Ku_Rx G/T more than 13.2 dB/K and 7.12 dB/K, respectively.

• ETRI Journal
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• v.38 no.3
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• pp.417-424
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• 2016

In this paper, an accurate characterization of a fabricated X-band transmit/receive module is described with the process of generating control data to correct amplitude and phase deviations in an active electronically scanned array antenna unit. In the characterization, quantization errors (from both a digitally controlled attenuator and a phase shifter) are considered using not theoretical values (due to discrete sets of amplitude and phase states) but measured values (of which implementation errors are a part). By using the presented procedure for the characterization, each initial control bit of both the attenuator and the phase shifter is closest to the required value for each array element position. In addition, each compensated control bit for the parasitic cross effect between amplitude and phase control is decided using the same procedure. Reduction of the peak sidelobe level of an array antenna is presented as an example to validate the proposed procedure.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.2
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• pp.77-85
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• 2014

Recently, utilization of MIMO(Multi-Input Multi-Output) system using array antennas is evaluated significantly according to the extension of high-capacity and high-speed communication services. However, MIMO system has disadvantages such as high-complexity and high-power-consumption, because RF(Radio Frequency) chain is required as antenna number, and several array antenna is used in conventional MIMO system. In order to solve these problems, research about beamspace MIMO system using ESPAR(Electronically Steerable Parasitic Array Radiator) antenna that has single RF chain by using one active antenna and several parasitic elements has been studied actively. Beamspace MIMO system using ESPAR antenna is possible to solve the problems of conventional MIMO system, because this system is composed by single RF chain. In this paper, in order to improve the system security, chaos communication algorithm that has characteristics such as non-periodic, non-predictability, easy implementation and initial condition is applied to QPSK (Quadrature Phase Shift Keying) modulated beamspace MIMO system. We design the chaos QPSK modulated beamspace MIMO system, and evaluate SER performance of this system.

• Journal of IKEEE
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• v.26 no.2
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• pp.211-218
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• 2022

This paper presents a S-band phased array antenna system for receiving LEO satellite telemetry signals. The proposed antenna, which is performed to be beam-tiled along the elevation direction, consists of 16 sub-array assemblies, 16 active circuit modules, a perpendicular feed network and a control/power unit. In order to precisely track an LEO satellite, the developed antenna is placed with its elevation axis along the projected trajectory of the satellite on the earth. The center of antenna aperture is facing to the maximum elevation angle in the LEO trajectory. The beam-tilted angles for tracking LEO satellite are obtained by calculating accurately satellite points. Satellite tracking measurements are carried out in the range of ±30° with the respect to the maximum elevation angle. The S/N ratio of 16.5 dB and the Eb/No of 13.3 dB at the maximum elevation angle are obtained from the measurements. The measured result agrees well with the pre-analyzed system margin.