• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.3
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• pp.233-238
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• 2013

In this paper, a novel diversity and directivity mode-switchable planar antenna array is proposed. For the diversity mode, four elements are unfolded on the plane and high isolation can be achieved. On the other hand, the antenna function is changed to the directivity mode when they are folded and stacked. Each element works such as a stacked Yagi-Uda antenna with high directivity. Especially, the curved feed line as well as the hybrid feeding method is used to improve performances. The simulation results agree well with measurement results and it is successfully demonstrated that two modes are properly working at 2.4 GHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.6
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• pp.628-636
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• 2014

This paper describes the design and analysis of five-element planar array antenna of an anti-jamming satellite navigation system. We propose a design of multi-layer patch antenna for Global Positioning System(GPS) $L_1/L_2$ dual bands. The proposed antenna has two ports feeding network with a hybrid chip coupler for a broad bandwidth with Right-Handed Circular Polarization(RHCP). The measurement results show the bore-sight gains of 1.10 dBic($L_1$) and 0.37 dBic($L_2$) for the center element. The bore-sight gains of an edge element are 0.99 dBic($L_1$) and -0.57 dBic($L_2$). At a fixed elevation angle of $30^{\circ}$, antennas show average gains of -2.08 dBic ($L_1$) and -5.33 dBic($L_2$) for the center element, and average gains of -0.40 dBic($L_1$) and -2.09 dBic($L_2$) for the edge elements. The results demonstrate that the proposed array antenna is suitable for anti-jamming applications.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.6
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• pp.518-521
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• 2019

In this paper, an active antenna module operating in the 60 GHz band is designed and fabricated by combining a commercial transmitter chip and patch array antenna. The designed module is composed of an antenna PCB and a PCB with a transmitter chip. The frequency-control and bias-control signals are applied to the transmitter chip, using an Arduino kit. A baseband I/Q signal is also applied to the chip. A ring hybrid balun converts the output of the transmitter module to a single output, which is the output of the transmitter chip that outputs a differential output. The output is delivered to the $2{\times}4$ microstrip patch array antenna PCB as a micro-computer connector. The radiation pattern of the millimeter-wave signal of the final output is compared with the simulation results. The measured radiation patterns of the fabricated active antenna module confirm that the positions of the 3 dB beam width and null point agree well with the simulation results.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.1
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• pp.52-57
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• 2016

We introduce a hybrid scheduling in a multi-path poor scattering full-duplex (FD) system, which consists of one multi-antenna FD base station and a large number of single-antenna half-duplex mobile stations. Our hybrid scheduling utilizes partial channel state information at the transmitter. In particular, unlike the conventional scheduling method using opportunistic transmission for both uplink and downlink, the proposed scheme combines a random transmit beamforming for downlink and a zero forcing beamforming for uplink. As our main result, via computer simulations, it is shown that the proposed scheme has a superior sum-rate performance than that of the conventional scheduling method beyond a certain signal-to-noise ratio regime.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.2
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• pp.274-279
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• 2021

Since conventional massive antenna systems require too many RF chains, they have disadvantages of high implementation cost and complexity. To overcome this problem, hybrid precoding schemes have been proposed. But, they are still of high implementation cost and complexity because RF chains are connected to all antenna elements. In this paper, we consider massive MIMO systems with overlapped sub-array (OSA) structure and then, propose a hybrid precoding scheme. In the overlapped subarray structure, RF analog precoding matrix has a sparse structure where many elements of RF analog precoding matrix are zeros. Using this sparse property, we propose a GTP-based precoder design method for RF and baseband digital precoding. Through simulation, we show that the proposed scheme has more than 85% of the spectral efficiency of the fully-connected structure while having 20~30% of complexity of it.

• 한국정보통신설비학회:학술대회논문집
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• 2007.08a
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• pp.427-431
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• 2007

Applications in present-day mobile communication systems particularly require miniaturized dimensions and low-profiles of antenna in order to meet the mobile units. Thus, size reductions and bandwidth enhancements are becoming crucial design considerations for practical applications of microstrip antennas. The motivation of further experiments have been stepped to follow those studies for achieving compact and broadband, even multiplied operation modes, which are greatly increased with much attentions recently. To obtain broadband, single-feed, circularly polarized characteristics of microstrip antennas, a design with feed-line ought to be a factor of two. Usually, diagonally balanced-line feeds with hybrid coupler are employed to attain circular polarizations. We firstly formulated DGS (Defected Ground Structures) based operation principles of the entire microstrip components and therefore were able to derive impedance variance of feed-lines. After verifying corresponding experimental results, we targeted the frequency bands of UHF RFID (Ultra High Frequency Radio Frequency IDentification) and approximately of 0.4-2.4GHz have exhibited remarkable two resonance amplitudes as a dual band antenna. Our secondary researches were aimed to design quad band microstrip antenna which represents four resonance characteristics within the identical frequency bands as well. Microstrip patch has been meandered to lengthen the electrical paths, and the other design criteria with respecting physical parameters including radiation patterns and impedance bandwidths measurements will be described for verification. Advisable applications of these antennas can be GSM850, GSM900, GPS (L1-1575 and L2-1227) and UMTS-2110 of cellular systems, which extremely desire multiband and minimum size.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.9
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• pp.769-776
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• 2015

In this paper, a broadband MIMO antenna using the metal cover that is one of the antenna radiators is designed and implemented on the PCB. The proposed antenna consists of a monopole and an IFA fed by the coupling structure and a metal cover radiator. Therefore, a monopole and an IFA with a metal cover radiator operate simultaneously through a hybrid form of operation. The antenna satisfies VSWR 3:1 at the bands of LTE class 13, class 14, CDMA, GSM900, DCS, PCS, WCDMA, LTE class 40 and WiFi. The maximum ECC of diagonally fed MIMO antenna is 0.186. The measured average gain and efficiency were -5.14~-1.28 dBi and 30.87~74.48 % over the desire bands, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.12
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• pp.5007-5014
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• 2010

Recently n Korea, the House of Commons and terrestrial broadcasting facilities integrated with FM radio and the satellite compulsory was amended to transfer MATV(Master Antenna Television) adjusted by SMATV(Satellite Master Antenna Television). While the SMATV was accepted by default in most other countries, our county did not accept it as the default for broadcast. Because domestic cable and satellite television service providers are conflicts with their interest. bAs a result, the hybrid amplifier for SMATV technology development and volume production for the state is insufficient. Therefore, terrestrial television broadcast bands (54 ~ 806Mhz) and FM radio broadcast band (88 ~ 108Mhz) band satellite with (950 ~ 2150Mhz) to amplify the development of a broadband amplifier with subsequent resolution of problems is also presented in this study.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.5 no.2
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• pp.20-28
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• 1994

Theoretical radiation patterns for the corrugated horn antenna are analyzed by vector integral method and quasi-optics. The formular of the radiated fields for the corrugated horn antenna can be obtained by the potentials derived the equivalent current sources from hybrid fields at horn aperture and also calculated by the expanded mode set of Gaussian - Laguerre based on the quasi - optics. From comparison of the radiation patterns between two methods for a corrugated horn antenna designed on 85-115 GHz frequency range, the results are coincided well at center frequency but have some errors at each side frequencies 85 and 115 GHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.6
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• pp.756-759
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• 2012

This paper presents the multibeam service coverage of GEO(Geostationary Orbit) satellite and the practical antenna scheme scenarios to provide the universal communication services on the Korean peninsula. The proposed antenna systems consist of the simplest scheme and feed network so that they can be mounted on satellites. The feed networks are effectively organized according to the frequency and polarization plan. Despite simple structure, all scenarios meet the electrical performance by the optimization of feed allocation and feed excitation.