• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.11 no.4
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• pp.401-407
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• 2018

The transmission bandwidth of shorted-monopole antenna in the frequency range of LF and MF was analyzed and the transmission mode considering the permissible data rate dependant on the transmission bandwidth was analyzed in this paper. Based on the required ERP, the output power of transmitter was deduced by considering the antenna efficiency. The analyses are for DGPS and time information transmission system in the frequency range of 283.5kHz and 65kHz respectively. The transmission antenna was modeled as TLM antenna that designed in the limited antenna site. The antenna equivalent circuit and antenna bandwidth were deduced based on the simulation analysis of antenna characteristics. The analyzed antenna bandwidth was compared with the simulated antenna bandwidth. Also the transmission mode for transmitter of LF and MF was proposed by considering the antenna bandwidth.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.4
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• pp.797-804
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• 2014

The experimental design method based-on the measured data in the several LF monopole antenna was used in MF monopole antenna design. The design technique is also utilized in MF DGPS antenna design. It is not possible to predict the antenna performance of the MF short-monopole antenna because of simple experimental antenna design. Furthermore, it is difficult to design and analyze the various wired short-monopole antenna. The antenna models for performance analysis of the DGPS antenna with the various wired short-monopole structure are proposed in this paper. Based on the proposed antenna models, also, the antenna performance and design data of the wired short-monopole antennas are presented. To evaluate the validity of the analyzed antenna models, the wired short-monopole antenna for 100 kHz are modeled and analyzed. The antenna performance of the wired short-monopole antenna are compared with those of the previously presented LF antenna performance. Based on the evaluation for proposed antenna analyzing models, the DGPS wired short-monopole antennas are modeled and analyzed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.12
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• pp.1053-1058
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• 2016

The eLoran(enhanced Long Range Navigation) transmitting antenna is analyzed for co-location with an AM transmitting antenna in an MF transmitting site. To compensate for the loading effect, the umbrella-type loading is applied for eLoran antenna. The validity of the co-location between the MF antenna and the eLoran antenna is verified through the simulation results of the radiation pattern and the return loss. Also, coupling including antenna matching circuit is analyzed to verify the effect of the transmitting circuit. The coupling between the LF and eLoran antenna is -53.3 dB at 100 kHz and -64.8 dB at 1,053 kHz, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.1A
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• pp.41-46
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• 2003

A MF/HF marine whip antenna with side whips, which are connected at an angle with the straight main whip, has reported In this paper, the effects of side whips on the antenna are simulated by using NEC-WIN and a novel MF/HF ship antenna with side whips is designed First of all, the gain, return loss, and radiation pattern of the antenna on infinite perfect conductor plane are simulated as function of the parameters of the side whip, such as the number, the location, the length of the side whip and the angle with the main whip. After that, the size of the antenna is decided and set up on an experimental ship in Korea Maritime University. The antenna on the ship are simulated and the simulated input impedances are good agreement with the measured results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.5
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• pp.572-579
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• 2008

To predict the system coverage in the middle frequency(MF) band, it is required to know the antenna efficiency at a base station. However, calculating the accurate efficiency is difficult since the efficiency may change according to the area where the antenna is installed. Thus, this paper proposes a method to obtain the antenna efficiency of a base station in the MF band from the measurement. This method uses the measured field strengths and the attenuation model in the MF band. Therefore, an attenuation model which is used in the proposed method is presented at first. Then, the process of the proposed method is followed using detailed explanations. Finally, antenna efficiencies of base stations which are currently operating are obtained by applying the proposed method and the usefulness of the obtained results are verified by comparing with ideal efficiencies.

• Journal of information and communication convergence engineering
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• v.9 no.4
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• pp.363-368
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• 2011

The DGPS transmits the enhancement signal to GPS using the medium frequency band. The NDGPS service that covers the Korean peninsula has been started since 2009. The service area of ocean-based DGPS(maritime-DGPS) reference stations covers the 100NM, but land-based DGPS(land-DGPS) covers 80km service area less than that of maritime DGPS. The DGPS's antenna has the top-loaded monopole antenna type. Top-loaded monopoles are the logical antennas to be used in order to get a low profile antenna and a performance according to the broadcaster and communication needs. The antenna needs to get the ground plane with good conductivity characteristics and flat ground plane without obstacle near to the transmitting antenna. In this paper, the radiation characteristics of an equivalent MF antenna are analyzed in view points of the ground conductivity and the ground plane with obstacle near to the antenna.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.18-22
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• 2003

In this thesis, Middle frequency wave propagation modeling is studied for the varies mountain geography the experimented middle frequency propagation model is researched in a shot time to analyze the broad area that consists of mountains. Due to the Sommerfeld - Norton model which is used broadly the middle frequency propagation model to analyze the broad area in a short time is proposed introducing the newly attenuation parameter of the experimental results on the basis of actual experiments at the mountain configuration regardless of the area of mountain, plane, sea etc.

• Geophysics and Geophysical Exploration
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• v.4 no.1
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• pp.8-18
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• 2001

To delineate the inhomogeneities including fractures and to estimate the freshness of rock borehole radar consisting of the reflection and tomography methods, and GPR surveys were conducted at a granite quarry mine. The borehole reflection survey using the direction finding antenna was also conducted to get the spatial orientations of reflectors. 20 MHz was adopted as the central frequency for the borehole radar reflection and tomography surveys and 100 MHz was for GPR. Through the interpretation of borehole reflection data using dipole and direction finding antenna as well as GPR images, which are good agreement with each other, we could determine the orientation of the major fractures in three dimensional way. Parts of travel time curves of tomography data showed the anisotropy, which is uncommon in granite quarry. By comparing the tomography data and TeleViewer images, the anisotropy effect in this area are closely related to fine fissures aligned in the same direction. The area confined by the two fractures, MF2 and MF5, might consist of the most fresh granite in the surveyed area, which was concluded from the borehole radar tomography, and GPR images as well as the distribution of anisotropy.

• Journal of Positioning, Navigation, and Timing
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• v.11 no.4
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• pp.245-250
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• 2022

As location-based services using the Global Navigation Satellite System (GNSS) are diversified, concerns about the vulnerability of GNSS to radio disturbance and deception are also growing. Accordingly, countries that own and operate GNSS, such as the United States, Russia, and Europe, are also developing additional navigation systems that can compensate for GNSS' weaknesses. Among them, an R-Mode system that transmits navigation signals using an infrastructure that transmits differential GNSS (DGNSS) information using signals from the medium frequency band currently in operation is being developed in Europe and Korea. Since 2020, Korea has improved four DGNSS transmission stations, including Chungju, Eocheongdo, Palmido, and Socheongdo, to transmit R-Mode signals and test navigation performance in some parts of the West Sea. In this paper, we intend to establish a testbed for measuring the distance of R-Mode signals currently being transmitted and analyze the results. It is confirmed that the distance measurement performance varies depending on the antenna type, diurnal variation, and propagation path of the signal.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.1144-1153
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• 2015

The resonant mechanism of reradiation interference (RRI) over 1.7MHz from power transmission lines cannot be obtained from IEEE standards, which are based on researches of field intensity. Hence, the resonance is ignored in National Standards of protecting distance between UHV power lines and radio stations in China, which would result in an excessive redundancy of protecting distance. Therefore, based on the generalized resonance theory, we proposed the idea of applying model-based parameter estimation (MBPE) to estimate the generalized resonance frequency of electrically large scattering objects. We also deduced equation expressions of the generalized resonance frequency and its quality factor Q in a lossy open electromagnetic system, i.e. an antenna-transmission line system in this paper. Taking the frequency band studied by IEEE and the frequency band over 1.7 MHz as object, we established three models of the RRI from transmission lines, namely the simplified line model, the tower line model considering cross arms and the line-surface mixed model. With the models, we calculated the scattering field of sampling points with equal intervals using method of moments, and then inferred expressions of Padé rational function. After calculating the zero-pole points of the Padé rational function, we eventually got the estimation of the RRI’s generalized resonant frequency. Our case studies indicate that the proposed estimation method is effective for predicting the generalized resonant frequency of RRI in medium frequency (MF, 0.3~3 MHz) band over 1.7 MHz, which expands the frequency band studied by IEEE.