• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.555-559
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• 2003

Recently, in accordance with the commercialization of novel radio frequency utilization technologies, the radiated power must be rigorously limited for the purpose of protection of wireless facilities against frequency jamming or interference and for maintaining the quality of communication service. At present, the output power is measured from the conducted power for the domestic measurement criterion but is not a real radiated power and inaccurate. So, it is peformed to survey the more precisely accurate measurement scheme and analyze its criterion and methodology in comparison with foreign one. As a result of surveying and analyzing, it is concluded that the U.S. and E.U. is actually using the measurement method in consideration of terms of the Equivalent Isotropic Radiated Power(EIRP) and Effective Radiated power(ERP). In case of the frequency below 1 GHz, the half wave-length dipole antenna is used to measure the ERP and above 1 GHz the horn antenna as a reference antenna is used to measure the EIRP. Therefore, for the domestic purpose it is also necessary to take EIRP and ERP into consideration as a measurement criterion in order to make an accurate measurement and regulation.

• Journal of the Korea Society of Computer and Information
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• v.16 no.5
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• pp.101-107
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• 2011

The optimum weight vector is studied to remove interference and jamming signals in adaptive array antenna system. The optimum weight vector is calculated to apply a minimum variance algorithm and cost function in linearly constrained conditions, and accurately estimates target's signal. Adaptive array antenna system is the system which improves signal to noise ratio(SNR) and decreases interference and jammer power. Adaptive array antenna system delays at tap output of antenna array element. Each tap finally makes the complex signal of one in multiplier complex weight. In order to obtain optimum's weight calculation, optimum weight vector is used in this paper. After simulation, resolution is increased below $3^{\circ}$, and sidelobe is decreased about 10 dB.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.14 no.5
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• pp.531-541
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• 1989

To protect VHF FM radio receiver from the strong interference signal, the study of antenna processor causes a strong interference signal(CW, AM, FM) to be suppressed a level below a weaker desired signal by pointing a spatial null(effective attenuation = 35dB) in the direction of the interference against a stational jamming signal.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.3
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• pp.380-386
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• 2013

This paper represents an adaptive beamforming technique to suppress interference or jamming signals in wideband. In order to maintain low side lobe level(SLL) at an antenna element level, Taylor-weighting was used. Also, to make a nulling beam pattern toward jammer's directions in wideband, we used the modified Loaded Sample Matrix Inversion(LSMI) algorithm and Tapped Delay Line(TDL). To verify the proposed algorithm, we applied it to a rectangular array antenna. Finally, the results show beam pattern with low SLL and jammers suppression.

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

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.11
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• pp.1217-1224
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• 2009

This paper newly proposes a methodology towards computing antenna element weights which are satisfying asymmetric sidelobe levels(SLLs) specified arbitrarily on both sides of the main beam pattern, in the linear phased array antenna pattern synthesis problem. Opposite to the conventional methods in which the element weights are directly optimized from the array factor, this method is based on the optimum perturbations of complex roots inherent to the Schelkunoff's polynomial form which is described for the array factor. From the proposed methodology, the capability of nulling the directions of multiple jammers is also possible by independently perturbing only the complex roots corresponding to each jamming direction, hence allowing an enhancement of the simplicity of the numerical procedure by means of a proper reduction of the dimension of the solution space. The complex weights over the array are then easily computed by substituting the optimally perturbed complex roots to the Schelkunoff's polynomial. Some examples are examined and numerically verified by substituting the extracted weights into the array factor equation.

• Journal of Satellite, Information and Communications
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• v.8 no.4
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• pp.37-42
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• 2013

In this paper, we propose a compensation method of a non-ideal antenna array and a computationally efficient estimation method of the direction of arrival (DOA) for the antenna array. For DOA estimation, an antenna array is essential. By using the phase difference between the output signals of antennas, we can derive the DOA. In practice, however, mutual coupling between the elements of an antenna array change the beam pattern of each element and degrade the performance of DOA estimation. In the proposed method, we first estimate the DOA for the mid-subarray of the array, where all elements undergo relatively same coupling effect. We use the estimation of signal parameters via rotational invariance techniques (ESPRIT) algorithm to estimate the DOA. Then, we expand the array based on the estimated DOA by compensating the coupling effect. Simulation results show that the proposed method is effective when jamming to noise power ratio (JNR)is relative low.

• Journal of Convergence for Information Technology
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• v.10 no.5
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• pp.30-35
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• 2020

In this paper, we analyzed the tracking error for the monopulse radar by controlling the phase difference, amplitude ratio and engagement angle of the cross-eye jammer. Cross-eye jamming is an important jamming method for monopulse radars, which causes a displacement in the radar receiving antenna input and misleads the radar's tracking angle. As a result of analyzing the tracking distance error of the radar while changing the engagement angle between the monopulse radar and jammer, the maximum distance error occurs when the engagement angle is 0° and the phase difference is 180°. It was confirmed that the error decreased to 70% or less of the maximum distance error into 45°~135°. In order to increase the efficiency of jammers, it is necessary to study rotary jammers or multi-channel jammers. This study will be very useful for the design of cross-eye jammers for aircraft and ships.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37C no.12
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• pp.1245-1255
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• 2012

There are various anti-jamming algorithms for the GNSS system which is vulnerable to jamming, and the methods using array antenna show the best performance. Among them, the DOA estimation algorithms to identify the location of the jammer is very important. However, in case of the rotorcraft, the wireless channel which amplitude and phase changes with time is generated by the rotation of the rotor and it affects the performance of existing anti-jamming algorithms. In this paper, we modeled the effect of the rotor in four scenarios according to the correlation of antennas and assured that the performance of DOA estimation algorithms are degraded and saturated regardless of JNR due to the rotor effect. When we use the averaging method to solve this problem, the performance is improved as increasing samples for estimating. And in case of using moving average method with averaging, it shows similar performance. In addition, it reduces the required memory and moderates the variation of DOA estimation.

• Journal of Positioning, Navigation, and Timing
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• v.12 no.2
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• pp.101-111
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• 2023

Many spoofing detection studies have been conducted to cope with the most difficult types of deception among various disturbances of GPS, such as jamming, spoofing, and meaconing. In this paper, we propose a spoofing detection scheme based on elevation masked-relative received power between GPS L1 and L2 signals in a system using a multi-band array antenna. The proposed scheme focuses on enabling spoofing to be normally detected and minimizes the possibility of false detection in an environment where false alarms may occur due to pattern distortion among elements of an array antenna. The pattern distortion weakens the GPS signal strength at low elevation. It becomes confusing to detect a spoofing signal based on the relative power difference between GPS L1 and L2, especially when GPS L2 has weak signal strength. We propose design parameters for the relative power threshold including beamforming gain, the minimum received power difference between L1 and L2, and the patch antenna gain difference between L1 and L2. In addition, in order to eliminate the weak signal strength of GPS L2 in the spoofing detection process, we propose a rotation matrix that sets the elevation mask based on platform coordinates. Array antennas generally do not have high usefulness in commercial areas where receivers are operated alone, but are considered essential in military areas where GPS receivers are used together with signal processing for beamforming in the direction of GPS satellites. Through laboratory and live sky tests using the device under test, the proposed scheme with an elevation mask detects spoofing signals well and reduces the probability of false detection relative to that without the elevation mask.