• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.4
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• pp.651-658
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• 2017

This paper proposes an analysis method of performance degradation of antenna due to radio frequency interference between an antenna and adjacent noise sources using active scattering parameters. The radio frequency interference can be analyzed by the measured or simulated scattering parameters and by excited noise sources in the circuit as well. In this paper, a planar inverted-F antenna and a noise source are designed and fabricated to analyze radio frequency interference between the planar inverted-F antenna and noise source. The proposed analysis method uses active scattering parameters, of which verification is experimentally verified, and in simulation as well.

• ETRI Journal
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• v.22 no.1
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• pp.12-19
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• 2000

Wireless communication systems using airship have been proposed in worldwide. The airship will be located at the stratosphere about $20{\sim}23\;km$ above the sea level. The position of airship will vary within the station keeping range with time due to the drag of the wind in the stratosphere. When the earth station antenna has a high gain without the tracking function, the antenna performance may be degraded by a small variation of the airship. This means that variation of airship location could result in serious degradation of the system performance. In this paper, degradation in earth station's Equivalent Isotropic Radiated Power (EIRP) and Gain to noise Temperature ratio (G/T) due to the stratospheric platform movements has been derived by calculating the deviation angle of the main beam directions between the earth station and the platform antenna. In this case, the antenna of the earth station has been assumed circular and/or patch array antennas.

• Journal of electromagnetic engineering and science
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• v.11 no.1
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• pp.1-4
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• 2011

In this letter, we propose a novel tag antenna that has low performance degradation with nearby dielectric material. We obtained a stable reading performance and a broad matching bandwidth on nearby dielectric materials by employing a T-matching network with thick line width and capacitively slot-loaded arms. We then built the proposed antenna and measured the tag sensitivity to examine the reading characteristics with nearby dielectric materials. The measured results clearly demonstrate stable tag sensitivity with various nearby dielectric materials, such as foam, acrylic-plastic, glass, and ceramic plates. To more closely observe the antenna characteristics with nearby dielectric materials, we also examined the impedance variation and surface current distribution with respect to the dielectric constant of nearby target objects, which ranged from $1{\times}{\varepsilon}_0$ to $16{\times}{\varepsilon}_0$.

• Journal of electromagnetic engineering and science
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• v.12 no.2
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• pp.176-184
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• 2012

In this paper, the effects of a metal plane on the performance of a meandered slot RFID antenna are evaluated in a real environment, and 3 metal plane cases are considered (the most likely scenarios in which metal conductive materials are placed near the tag antenna). The metal plane effects can be categorized as matching degradation and antenna gain variation. First, matching degradation due to the antenna's induced mutual impedance is experimentally investigated. In addition, the gain variation is investigated to figure out the change in the radiation characteristics. With the derived antenna parameters, the read range is calculated with the Friis transmission equation and measured to analyze the effects of a metal plane on RFID system performance. The calculated and measured read range varies from 9.3 m to 19.1 m as the distance between the RFID antenna and the metal plane changes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.6A
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• pp.426-437
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• 2012

This paper proposes an array antenna assisted Doppler spread compensator with dummy elements which are placed on either end of a monopole array for a digital terrestrial television broadcasting (DTTB) receiver. An array antenna assisted Doppler spread compensator, proposed previously, has a major drawback in performance degradation owing to mutual coupling effect among array elements. In order to solve the mutual coupling problem, dummy elements, placed on both sides of the monopole array mitigate performance degradation of a Doppler spread compensator arising from the mutual coupling among monopole array elements. Computer simulation results show that the dummy elements can reduce this performance degradation as well as expand the operating bandwidth of a Doppler spread compensator.

• 전기의세계
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• v.29 no.9
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• pp.584-593
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• 1980

Conventional radar antenna systems are susceptible to performance degradation caused by unwanted signals received via the antenna sidelobes and/or mainlobes. Adaptive array systems offer possible solution to this interference problem by automatically steering nulls to unwanted signals providing significant system performance improvement. Another important andvantage of the adaptive array is its self-optimization capability which uses the collective incoming noise data for the nulling purposes. This paper provides a tutorial introduction to adaptive arrays as well as some new development of recent research in this area. Optimum link between the antenna theory and signal processing has been sought by illustrating the gain patterns and output signal-to-noise ratio. Signal acqusition methods are shown including a new attempt of the use of spread-spectrum techniques in conjuction with array systems.

• Journal of Astronomy and Space Sciences
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• v.28 no.4
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• pp.299-304
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• 2011

As more satellites are designed to downlink their observed image data through the X-band frequency band, it is inevitable that the occupied bandwidth of a target satellite will overlap with that of other X-band downlink satellites. For sun-synchronized low earth orbit satellites, in particular, it can be expected that two or more satellites be placed within the looking angle of a ground station antenna at the same time. Due to the overlapping in the frequency band, signals transmitted from the adjacent satellites act as interferers, leading to degraded link performance between target satellite and ground station. In this paper, link analysis was initiated by modeling the radiation pattern of ground station antenna through a validated Jet Propulsion Laboratory peak envelope model. From the relative antenna gain depending on the offset angle from center axis of maximum antenna directivity, the ratio of received interference signal level to the target signal level was calculated. As a result, it was found that the degradation increased when the offset angle was within the first point of radiation pattern. For a 7.3 m antenna, serious link degradation began at an offset angle of 0.4 degrees. From this analysis, the link performance of the coming satellite passes can be recognized, which is helpful to establish an operating procedure that will prevent the ground station from receiving corrupted image data in the event of a degraded link.

• Journal of Communications and Networks
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• v.5 no.2
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• pp.150-156
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• 2003

In this paper, an uplink MC-CDMA system incorporating multiuser detection and smart antennas has been considered. The performance of asynchronous as well as synchronous system is studied over a correlated Rayleigh multipath slow fading channel. A simplified array-processing algorithm suitable for slow fading situation is investigated to overcome the heavy computational complexity associated with Eigen solutions. The effect of variable data rate in the system performance is considered and effectiveness of antenna array to handle high data rate is discussed. A brief investigation on the system performance degradation due to correlated channel is also carried out. Based on the extensive simulation carried out, the performance of the asynchronous uplink system is found dramatically improved with antenna array and multiuser detection. Asynchronicity and channel correlation are found to affect the system performance significantly. The investigated simpli- fied algorithm produces similar results as Eigen solutions in slow fading situation with much reduced complexity.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2005.11a
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• pp.353-356
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• 2005

There have been many researches on the antenna performance degradation with the presence of the human body around the antenna structure to accomodate personal communication service [1][2]. To better understand the human body effects on the antenna resonance, radiation pattern, and input impedance, simulation was carried out with changing of the distance between antenna and lossy material. Effects on the antenna performance by the surrounding materials are also important in the case of the RFID system. It is desirable that the tag antennas for RFID system must reveal isotropic radiation pattern as well as attain the good impedance matching. In this paper, we investigated the antenna resonance and input impedance characteristic when there exist a lossy material sphere near various types of antenna at 900 MHz. In short antenna resonance was mostly affected by lossy material in the case of a rectangular loop antenna, and impedance variation was smallest in the case of a halfwave dipole.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.2
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• pp.208-216
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• 2014

Ground station in lunar mission is responsible to receive telemetry signal including sensor data from lunar orbiter and/or lander. At preliminary stage of developing this ground station, receiving performance such as antenna size and noise temperature should be designed on the basis of link budget analysis. When the antenna of ground station is pointing to the moon to communicate with lunar orbiter and/or lander, noise level is supposed to be increasing due to the lunar flux density. It means that the moon is working as a noise source to degrade receiving performance when antenna is pointing to the moon. Antenna noise temperature contributed by the moon was firstly calculated and secondary validated by using test configuration in this paper. Consequently, it was shown that antenna noise temperature caused by the moon was quietly matched with measured one and G/T degradation of receiving system in lunar mission can be calculated depending on antenna size and frequency.