• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.66 no.2
• /
• pp.379-382
• /
• 2017

This paper proposes a $4{\times}4$ broadband phased array antenna using a Left-Handed Transmission Line (LHTL) based phase shifter. The phased array is constructed with sixteen quasi-Yagi antenna elements and the phase shifters, as well as four power dividers. A key component of the system, the LHTL based phase shifter is able to control a phase delay of incident waves linearly and continuously. The fabricated phased array antenna operate for a frequency range of 800 MHz (1.6 GHz~2.4 GHz). The beam scanning range of the $4{\times}4$ array antenna is ${\pm}27^{\circ}$ horizontally and vertically while the antenna gain is maintained with a variation of ${\pm}1.4dBi$.

• Electronics and Telecommunications Trends
• /
• v.37 no.3
• /
• pp.41-51
• /
• 2022

This article presents an overview of the key technologies in the communications payload of broadband LEO satellite communications systems. In recent years, new developments have been realized for LEO satellite communications. SpaceX's Starlink, a technology leader in this field, offers premium services with satellites carrying in-house developed communications payloads. OneWeb, Amazon, Telesat, and Boeing are also developing LEO satellite communications payloads. The communications payload consists of user link antennas, inter-satellite link communications equipment, feeder link antennas, and a digital processor. Highly sophisticated technologies of compact active phased array antennas for generating multiple hopping beams and light laser communication equipment for ultra-high-speed inter-satellite communication will be applied to next- generation payloads.

• Journal of Life Science
• /
• v.17 no.1 s.81
• /
• pp.82-90
• /
• 2007

In an attempt to establish the appropriate ventilation device for the bottle culture of king oyster mushroom (Pleurotus eryngii), we investigated carbon dioxide concentration and fruiting body formation according to the various ventilation systems within the mushroom house. In addition to, the efficiency of air circulation and growth rate as well as the appearance of physiologically abnormal phenotypes during their growth stage were also evaluated. four different ventilation devices, parallel-pressure type, positive-pressure type, negative-pressure type, and positive- and negative-pressure type were applied in this study. The positive-and negative-pressure type showed the highest efficiency of air circulation as $CO_2$ concentration was 800 ppm and the level of air current was relatively low compared to the other types (the $CO_2$ concentration of parallel-pressure type was 1,400 ppm). Moreover, the stipe length, the cap diameter, yield, and general quality grown in positive- and negative type ventilation device were also better than in the other three devices though it took slightly longer period for harvesting (18.4 days) than the others (17.6, 17.9 and 18.3 days). The appearance of physiologically abnormal phenotypes such as fruiting body lump, soft rot, and brown rot were significantly decreased in positive-and negative type compared to other types, while the appearance rates were not much different for other symptoms of bacterial ooze, stipe limb and stipe bumpy. In summary, we propose that the optimal ventilation system for the bottle culture of king oyster mushroom is positive- and negative type, and this device is expected to increase the total quality as well as yield all year around.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.51 no.7
• /
• pp.26-36
• /
• 2014

The needs of active phased arrays antenna system is getting more increased for IMT-Advanced system efficiency. The active phased array structure consists of lots of small transceivers and radiation elements to increase system efficiency. The minimized module of high efficiency transceiver is key for system implementation. The power amplifier of transmitter decides efficiency of base-station. In this paper, we design and implement minimized module of high efficiency transceiver for IMT-Advanced active phased array system. The temperature compensation circuit of transceiver reduces gain error and the analog pre-distorter of linearizer reduces implemented size. For minimal size and high efficiency, the implented power amplifier consist of GaN MMIC Doherty structure. The size of implemented module is $40mm{\times}90mm{\times}50mm$ and output power is 47.65 dBm at LTE band 7. The efficiency of power amplifier is 40.7% efficiency and ACLR compensation of linearizer is above 12dB at operating power level, 37dBm. The noise figure of transceiver is under 1.28 dB and amplitude error and phase error on 6 bit control is 0.38 dB and 2.77 degree respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.16 no.6 s.97
• /
• pp.549-555
• /
• 2005

This paper describes a microwave direction finding technology which is used for RF signal acquisition and monitoring systems. This paper suggests a direction finding method which use a combination of the amplitude-comparison technology and the phase-comparison technology. The amplitude-comparison technology uses the amplitude difference of the RF signals received from the array antennas of direction finding system and removes the ambiguity of wave incident bearing. The phase-comparison technology uses the phase difference of the RF signals received from the same nay antennas and makes a good direction finding accuracy. The suggested direction finding technology is designed to place 8 array antennas in a $45^{\circ}$ distance around the circle for $360^{\circ}$ azimuth angle. Also it is designed to use the phase difference of the received signals ken two nearby antennas to measure the signal incident direction accurately and to use the amplitude difference to remove the ambiguity of wave incident bearing. The simulation and measurement results are under $0.5^{\circ}$ bearing error in $2.0\~6.0$ GHz when SNR is 30 dB.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.38B no.9
• /
• pp.744-750
• /
• 2013

In this paper, we proposed new type of an artificial magnetic conductor(AMC) structure, which has a high impedance surface for realizing the meta-material characteristics. The designed AMC structure set a goal of 3.2GHz, and the reflector, which consists of periodically arrayed AMCs is fabricated and measured. The high impedance improves the reflection coefficient, decreases the system size and interference, and increases the antenna performance. The structure has embodied the high impedance by the thickness and relative permitivity of the dielectric substrate and the design configuration without the metallic via hole which connects the AMC to the GND. The bandwidth is 150% broader than the similar AMC structures. Also, the distance between the antenna and the AMC reflector is decreased by ${\lambda}/10$ as working as the metal(PEC) reflectors. The antenna radiation characteristics are 3dB increased at 10mm away from reflector by measurement. The proposed reflector could be inserted in the portable mobile devices, and the antenna's performance has improved by the reflector. The specific absorption rate is dramatically decreased over 94% because the back radiation of the antenna is shielded.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.18 no.6
• /
• pp.1015-1022
• /
• 2023

In this paper, we propose DLP(Dual Linear Polarization) antenna with aperture coupled feeding structure for private network. The proposed antenna has general aperture coupled structure and design two port between top and bottom layer to obtain the enhanced isolation. Also, The size of each substrate(top and bottom layer) is 34.0 mm(W)×34.0 mm(L), which is designed on the FR-4 substrate which thickness (h) is 1.0 mm, and the dielectric constant is 4.4. Also, the size of patch antenna is 12.70 mm(W2)×14.60 mm(L3), and it is located on the top layer. The size of feeding line is 24.0 mm(W2)×1.6 mm(L3), and is located at the bottom layer Also, rectangular slot is located on the ground plane between top layer and bottom layer. From the fabrication and measurement results, bandwidths of 300 MHz (4.52 to 4.82 GHz) for feeding port 1, and 170 MHz (4.65 to 4.82 GHz) for feeding port 2 are obtained on the basis of -10 dB return loss and transmission coefficient S21 is got under the -30 dB. Also, cross polarization isolation between each feeding port obtained

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.21 no.4
• /
• pp.417-426
• /
• 2010

This paper describes the 6-way power divider to be used as a feeding structure of the waveguide array antenna generating the plane wave at the near distance. The SMA connector has been connected at the center of the power divider in order to feed the radiating element. The six output ports made of waveguide are positioned on the peripheral of the divider. This paper proposes the method utilizing the inductive post in order to decrease the return loss. The height of the feeding pin, the diameter of the inductive post, and the distance between the feeding pin and inductive post have been investigated, and as a result, the power divider has been optimized. The simulated and measured results show the low return loss of about -40 dB. The calculated and measured transmission coefficients are -7.78 dB and -8.06 dB, respectively. The output power of the six waveguide port show equal-amplitude and equal-phase distribution. Since the power divider proposed in this paper can be expanded to the divider having several output ports, it could be easily applied to the various array antennas.

• Korean Journal of Optics and Photonics
• /
• v.16 no.3
• /
• pp.287-294
• /
• 2005

In this paper, an optical true time-delay (TTD) for two-dimensional (2-D) phased array antennas (PAAs), composed of a multi-wavelength optical source and a fiber optic delay line matrix consisting of $2\times2$ optical switches with optical fiber connected between cross ports, has been proposed. A 2-bit $\times4-bit$ optical TTD for 10-GHz 2-D PAAs has been implemented by cascading a wavelength dependent TTD (WD-TTD) and a wavelength independent TTD (WI-TTD). The unit time delay for WD-TTD and WI-TTD have been chosen as ${\Delta}T=12ps$ and $\Delta\tau=6ps$, respectively. Time delay have been measured at all radiation angles. The maximum delay error for WD-TTD was measured to be 3 ps due to jitter incurred from gain switching. For the case of WI-TTD, error was within ${\pm}\;1\;ps$. The proposed optical TTD for a 2-D PAA has the following advantages: 1) higher gain compared to one-dimensional linear PAAs, 2) stabilization of optical power and wavelength by using a multi-wavelength optical source, and 3) fast beam scan and simple operation due to electronic control of the $2\times2$ optical switches matrix on a column-by-column basis.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.23 no.1
• /
• pp.11-17
• /
• 2020

This study proposes a novel structure for the cross-eye, one of the representative jamming techniques of monopulse sensors. The proposed jammer tranceivers are composed of multi-channels with phased array antenna. We named this structure PRCJ(Phased array Retrodicetive Cross-eye Jammer). In this structure, formulas for calculating cross-eye gain and distance error are derived. We compare the properties of PRCJ with two-element retrodiredtive cross-eye jammer(TRCJ). PRCJ can achieve higher J/S because this structure can steer the spatially combined jamming signal in the direction of the incident monopulse signal. Because of the multiple channels in the phased array, it also increases the degree of freedom of channel matching. Finally, We preform a statistical analysis of the cross-eye gain according to the amplitude and phase errors. From this results, It has been found that PRCJ can get higher cross-eye gain than TRCJ.