• ETRI Journal
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• v.34 no.5
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• pp.767-770
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• 2012

This letter presents a novel compact circularly polarized patch antenna for Global Positioning System/Global Navigation Satellite System (GPS/GLONASS) applications. The proposed antenna is composed of a simple square radiating patch fed by a capacitive dual-feeder to increase the impedance bandwidth and a lumped element hybrid coupler to achieve the broadband characteristic of the axial ratio (AR). The realized antenna dimensions are $28mm{\times}28mm{\times}4mm$, which is the most compact size among the dual-band GPS/GLONASS antennas reported to date. The measured results demonstrate that the proposed antenna has a gain of 2.5 dBi to 4.2 dBi and an AR of 0.41 dB to 1.51 dB over the GPS/GLONASS L1 band (1.575 GHz to 1.61 GHz).

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.357-360
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• 2003

본 논문에서는 $90^{\circ}$ 하이브리드 결합기에 여파기 특성을 결합하여 전력분배와 하모닉 저지특성효과를 보여주고 있다. 일반적인 $90^{\circ}$ 하이브리드 결합기는 위상차를 갖고 전력을 분배, 합성하는 데에만 쓰이고 있기 때문에 비선형 소자와 결합함으로써 생기는 하모닉 성분을 억제하려면 여파기를 따로 설계해야 하는 단점이 있다. 그래서 본 논문에서는 하이브리드에 저역통과 여파기 특성을 결합함으로써 위상차와 전력분배는 물론 여파기 특성인 감쇠효과를 이용하여 하모닉 성분을 크게 감소시킬 수 있는 구조를 연구하였다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.66-70
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• 2003

In this paper a plannar singly balanced diode Miter for 24GHz band application is designed and implemented using a microstrip line and two schottky barrier beam lead mixer diodes. The implemented mixer have a conversion loss of 6 [dB], LO/RF isolation of 23 [dB], input 1dB compression point of 4 [dBm]. this diode mixer would be useful for homedyne radar.

• Proceedings of the IEEK Conference
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• 2000.07b
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• pp.1063-1066
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• 2000

ln this paper, a new active phase shifter is proposed using a vector sum method, and it is shown that the proposed phase shifter is more efficient than the others in size, power, number of circuits, and gain. Also a unique digital phase control method of the circuit is suggested. The proposed scheme was designed and implemented using a Wilkinson power combiner/divider, a branch line 3dB quadrature hybrid coupler and variable gain amplifiers (VGAs) using dual gate FETs (DGFETs). Furthermore, it is also shown that the proposed scheme is more efficient and works properly with the digital phase control method.

• Journal of the Korean Institute of Telematics and Electronics
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• v.21 no.2
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• pp.24-28
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• 1984

A new type of digital echo canceler for two-wire digital transmission is presented. The new principle estimates an echo signal by use of the arithmetic means estimate for each transmitted data pattern, which leads to relatively simple hardware. The principle is compared with adaptive digital filter methods through theoretical analysis and computer simulation. The results show that the proposed method has fast convergence property with respect to its hardware simplicity and that the convergence time is independent of echo level. Quantization effects are also analyzed.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.8
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• pp.1759-1764
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• 2015

In this paper, we considered a design method of a circular polarization (CP) antenna for UHF (ultra high frequency) RFID (Radio Frequency IDentification) readers. The antenna is a dual-fed circular microstrip patch which produces right-handed CP. Quadrature hybrid coupler is used for dual feeding. The outputs of the coupler and circular patch are connected through copper wires, and the inductive reactance produced by the connecting wires is compensated by a ring-shaped slot inserted inside the circular patch. The effects of the geometrical parameters of the proposed antenna on the antenna performance are examined, and the parameters are adjusted to be suitable for the operation in North American UHF RFID band (902-928 MHz), which includes domestic UHF RFID band. The antenna is fabricated, and the experiment results reveal a frequency band of 854-993 MHz for a voltage standing wave ratio < 2. The fabricated antenna is connected to a commercial RFID reader, and it showed a good performance of tag identification.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.6
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• pp.74-79
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• 2019

The military vehicle produces electric power through an engine-integrated serial hybrid generator that is connected to the engine and does not have a separate generator installation space. However, depending on the mechanical characteristics of the connection between the generator and the engine, iron oxide for internal rusting and lubrication grew scattered. The iron oxide is adhered to the starter to deteriorate the starting performance, and there is a problem that the noise of the leg due to wear of the gear is increased. To solve this problem, the connection spline material and the surface treatment of the engine were improved and the shape was changed to a grease sealing type to prevent the generation of iron oxide inside. As the shape of the generator connector composing the shafting system was changed, the integrity of the structure was confirmed through the torsional endurance test. In addition, through the actual vehicle load test, it was verified that no corrosion occurred during the target life span without internal corrosion. It was confirmed that the anti-scattering structure of the grease effectively suppresses the generation of iron oxide, thereby reducing the noise generated from the generator. In this paper, we propose a fundamental solution to the degradation of the starter and the noise generation by preventing the back corrosion caused by the serial hybrid generator installed between the engine and the transmission.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.11
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• pp.1281-1286
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• 2008

The PSK carrier signal recovery circuit using a six-port phase correlator was analyzed and the circuit structure is proposed in this paper. The proposed carrier signal recovery circuit that is made of reflection element and six-port phase correlator, which is comprised of a power divider and three hybrid branch line couplers, give a simple structure and can be fabricated without no difficulty. The circuit recovers the carrier signal of BPSK and QPSK modulation signal. The proposed scheme can be utilized as a basis structure for high-mode PSK carrier signal recovery. By simulation results, the recovered signal by the proposed circuit shows a good carrier signal characteristic with CW signal of a constant phase($23.4^{\circ}$) and ${\pm}0.8^{\circ}$ phase error due to glitch conditions.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.9
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• pp.907-915
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• 2002

In this paper, a compact digital phase shifter to be used an active phased array antenna system for satellite communications was proposed. The even and odd mode analysis for a given reflection-type phase shifter, which uses a folded hybrid coupler as a base element, was performed and the design parameters were derived. Also, to verify experimentally the electrical performances of the proposed structure, X-band 4-bit digital phase shifter was designed and fabricated using Teflon soft substrate $({\varepsilon}_r; =\;2.17)$. Its circuit size was less than 3.5 cm $\times$ 3.0 cm, and it exhibited at least 50 % size reduction as compared with the conventional unfolded configuration. The experimental results of the fabricated phase shifter showed that the average insertion loss and insertion loss variation were less than 3.5 dB, $\pm$ 0.6 dB within the operating band, 7.9 ~ 8.4 GHz, respectively. And, input and output return loss were more than 10 dB, respectively. Also, the phase response of the phase shifter showed 4-bit operation with $\pm$3$^{\circ}$ rms phase error.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.1
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• pp.231-238
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• 2019

In this paper, we have studied how to improve the amplifiers efficiency by minimizing the combining loss when several unit power amplifiers are combined to obtain high output power. Specifically, we have developed Ka-band Spatial Combining Amplifier. The fabricated Spatial Combining Amplifier is a Ka-band 20W class SSPA, which uses a 5W class unit amplifier module 8EA designed using a GaN bare die. We also combined The unit amplifier module using 8-way spatial divider and combiner with a hybrid radial structure. The output combining loss of the fabricated spatial coupler is about 0.334dB, which is about 92.6% efficiency. In this paper, we developed a Spatial Combining Amplifier with a maximum saturation output of 10W and a power addition efficiency of over 15%. As a result, we achieved the maximum saturation output of 30W and the power addition efficiency of 19%.