• Journal of the Korea Convergence Society
• /
• v.8 no.1
• /
• pp.1-6
• /
• 2017

In this paper, we propose a new method for a correlative phase comparison direction finding(DF) which detects the arrival direction of radio waves by data fusing the calculated phase difference and the measured phase difference between the antennas when the radio waves are incident on the circular array antenna composed of 7 antennas respectively. The correlation type phase comparison method uses a uniform circular array(UCA) and a linear array method. The phase difference data calculated formally and the phase difference data measured in the test environment are fused with a correlation function, therefore, it is superior to the currently used phase comparison direction detection method. When the signal-to-noise ratio (SNR) of the received signal is 20dB and the inter-antenna distance to the wavelength of the received signal($L/{\lambda}$) is 0.5, the accuracy of the correlative DF is $1.7^{\circ}$ while measurement phase comparison's is larger than $2.5^{\circ}$, It can be used for electromagnetic signal monitoring and military direction detection.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.14 no.9
• /
• pp.2157-2163
• /
• 2010

This paper includes the study of DOA(Direction of Arrival). CVDF(Correlative Vector Direction Finding) algorithm using at the phase difference each antenna needs to obtain ideal sinusoidal phase difference patterns. However, the phase difference patterns of circular array antennas may be interfered on a specific frequency band and to particular angle. The effect of installing each array antenna circularly and the effect of the interference by center pole (located in the center of a circular array antennas) may distort the phase difference patterns. This paper propose how to change the combination of antennas to measure phase difference patterns in real-time and how to use antenna beam patterns for minimizing the degradation phenomena with old CVDF algorithm. According to the test result, the capability of direction finding is improved.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.12 no.1
• /
• pp.97-105
• /
• 2009

In this paper, the performance of AP(Alternating Projection) and EM(Expectation Maximization) algorithms is investigated in terms of detection of multiple signals, resolvability of coherent signals and the efficiency of sensor array processing. The basic idea of these algorithms is utilization of relaxation technique of successive 1D maximization to solve a direction finding problem by maximizing the multidimensional likelihood function. It means that the function is maximized over only for a single parameter while the other parameters are fixed at each step of the iteration. According to simulation results, the algorithms showed good performance for both incoherent and coherent multiple signals. Moreover, some advantages are identified for direction finding with very small samples and fast convergence. The performance of AP algorithm is compared with that of EM using multiple criteria such as the number of sensor, SNR, the number of samples, and convergence speed over uniform circular array. It is resulted AP algorithm is superior to EM overally except for one criterion, convergence speed. Especially, for EM algorithm there is no performance difference between incoherent and coherent case. In conclusion, AP and EM are viable and practical alternatives, which can be applied to a direction under due to the resolvability of multi-path signals, reliable performance and no troublesome eigen-decomposition of the sample-covariance matrix.

• Journal of the Korea Convergence Society
• /
• v.10 no.1
• /
• pp.1-6
• /
• 2019

In this paper, we have studied a direction finding method of the radio signal by comparing the phase difference and its pattern from the uniform circular array antenna. In the phase comparison direction finding, if the length of the antenna baseline is longer than 0.5 wavelength of the incident signal, azimuth ambiguity occurs in which two or more azimuth angles are calculated in the same phase difference. The azimuthal ambiguity is removed by fusing the phase difference of the 5 antennas. The developed ambiguity elimination technology reduces the azimuth error where the antenna baseline is shorter than 1.236 wavelength in the uniform circular array with five antennas. This algorithm is very useful for the design of direction finder of an electronic information system.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.25 no.2
• /
• pp.117-124
• /
• 2022

Single-ring circular array antennas can be applied to direction finding systems in order to use nose-section in other purposes, and the interferometry is a proper direction finding method to those systems. We usually make the interferometer baseline long enough to achieve good angular accuracy. However, an interferometer with baseline longer than a half-wavelength has the ambiguity problem. In this paper, we present a novel method for solving the ambiguity problem in interferometry systems. This technique is based on the amplitude comparison method and the space division table, and it can place a target within the angular region in which the ambiguity problem does not occur by roughly estimating direction-of-arrival. The Monte Carlo simulation results show that proposed method can effectively remove the ambiguity problem in the system.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2010.05a
• /
• pp.535-539
• /
• 2010

This paper include to study DoA(Direction of Arrival) for radio collection and monitoring system. The direction finding calculated by applying the CVDF (Correlation Vector Direction Finding) algorithm for the five circular dipole antenna over V / UHF band. To improve the accuracy of direction finding by applying CVDF algorithm needs to obtain ideal phase difference each antennas. However, a circular array antenna phase difference pattern may be distorted on a specific frequency band or to particular direction. The effect of installing each array antennas circularly and the effect of the interference of center pole (located in the center of a circular array antenna mount) may make the distortion of phase pattern. If you use an active antenna instead of passive antenna to obtain good sensitivity, you would measure the more distortion. This paper propose how to change combination of antennas to measure the phase in real-time and how to use antenna beam patterns for minimizing the degradation phenomena at applying simple CVDF algorithm and increasing the direction finding capability.

• Journal of the Korean Data and Information Science Society
• /
• v.22 no.5
• /
• pp.961-966
• /
• 2011

Circular variables are those that have a period in its range. Their examples include direction of animal migration, and time of drug administration, just to mention a few. Statistical analysis of circular variables is quite different from that of linear variable due to its periodic nature. In this paper, the author proposes new circular regression models using geodesic lines on the surface of the sample space of the response and the predictor variables.

• Proceedings of the KSR Conference
• /
• 2007.05a
• /
• pp.620-625
• /
• 2007

According to 'Metropolitan Traffic Network Plan' announced in 2001, radial railways which connect Seoul with satellite cities around Seoul appear gradually. And followed by this, social demand for circular metropolitan railways that can connect the radial railways horizontally is increasing. But existing plans about circular metropolitan railways has limits to propose only passing cities of the railways. If there is no detailed guideline for circular metropolitan railways, the each railway for circular line will be constructed individually and then it will be not effective circular railways totally. Additionally that railway project will be easily interrupted by popular complaints. Therefore "The basic plan for circular metropolitan railways" is needful to guide a right direction for circular metropolitan railways. In this paper, rough track diagram of 'node' station for circular metropolitan railways is proposed. It is essential part of the basic plan. If the track diagram of a node is publicized in advance and individually lines of circular metropolitan railways is enforced to followed it, all lines will has rich circular functionality. Finally, effective circular metropolitan railways can be built.

• The Journal of the Acoustical Society of Korea
• /
• v.30 no.6
• /
• pp.308-314
• /
• 2011

This paper presents techniques for estimating directions of multiple sound sources ranging from $0^{\circ}$ to $360^{\circ}$ using circular probability distributions having a periodic property. Phase differences containing direction information of sources can be modeled as mixtures of multiple probability distributions and source directions can be estimated by maximizing log-likelihood functions. Although the von Mises distribution is widely used for analyzing this kind of periodic data, we define a new class of circular probability distributions from Gaussian and Laplacian distributions by adopting a modulo operation to have $2{\pi}$-periodicity. Direction estimation with these circular probability distributions is done by implementing corresponding EM (Expectation-Maximization) algorithms. Simulation results in various reverberant environments confirm that Laplacian distribution provides better performance than von Mises and Gaussian distributions.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.9 no.2
• /
• pp.17-23
• /
• 1972

In this paper, the radiation characteristics of a large circular loop antenna with sinusoidal current distribution is studded in a moving media with a constant velocity much less than the speed of light. The diameter of the circular loop antenna is comparable with or larger than wave length. In studing the radiation characteristics, vector potential for the antenna is derived and relative field pattern is plotted from the vector potentials. Finally the field patterns are compared with those of stationary media. It is found that maximum directivities are shifted to the direction of the velocity of the media, and the field intensities are decreased in that direction and increased in opposite direction by the velocity component paralell to the loop plane. It is also found that the deviations for the pattern are proportional to the velocity of the media, the frequency of the distributed current, the diameter of the loop antenna, and the daviation depends only upon the parallel component of the velocity to the loop plane.