• Journal of Positioning, Navigation, and Timing
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• 제9권1호
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• pp.7-13
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• 2020

As a countermeasure against the threat of jamming which can disrupt operation of the Global Positioning System (GPS) receivers, various kinds of technique to estimate the Direction-Of-Arrivals (DOAs) of incoming jamming signals have been widely studied, and among them, the MUltiple SIgnal Classification (MUSIC) algorithm is known to provide very high resolution. However, since the previous studies regarding the MUSIC algorithm does not consider the orientation of each antenna element of antenna arrays, there is a possibility that DOA estimation performance degrades in the case of a misaligned antenna array whose antenna elements are not oriented along the same direction. As an effort to solve this problem, there exists a previous work which presents an MUSIC-based method for DOA estimation. However, the error between the real and measured values of each antenna orientation is not taken into consideration. Therefore, in this paper, the effect of the aforementioned error on the DOA estimation performance in the case of a misaligned antenna array is analyzed by simulations.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1999년도 학술발표대회 논문집 제18권 2호
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• pp.165-168
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• 1999

This paper concerns a least square approach to optimizing a thinned antenna array with respect to antenna spacing to improve the sidelobe performance. A least square method based on a modified version of the modified perturbation method is proposed to efficiently synthesize an optimum pattern in a thinned array. It is demonstrated that the array performance improves with the proposed method, compared with the conventional method.

• 전기의세계
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• 제29권9호
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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.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2006년도 하계종합학술대회
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• pp.191-192
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• 2006

An orthogonal antenna is presented for reader applications of radio frequency identification (RFID) at 433 MHz. The antenna is composed of two $1{\times}2$ sub-arrays orthogonally placed on a ground plane. Two different feeding networks are introduced to control horizontal and vertical radiation current flows for each sub-array, respectively. An inverted-F structure is used as a radiation element with vertical and horizontal currents flowing on the radiator, thereby obtaining two linear polarizations. Antenna gains are 3.71 and 3.43 dBi and isolation between the two input ports is less than 25dB.

• 한국정보통신학회논문지
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• 제19권2호
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• pp.393-400
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• 2015

최근 국내에서도 교통정보시스템의 보급 및 개발이 확산되고 일부 서비스가 시범사업을 거쳐 상용화되면서 활용도가 높은 DSRC에 대한 관심이 높아졌으며 노변기지국과 차량 설치장비용 안테나가 연구되고 있다. 차량용 안테나의 경우 크기의 소형화가 요구되어 단일패치를 이용하였으나 대부분의 경우 소형화로 인하여 성능의 저하가 있었다. 또한, 기존에 연구되고 있는 안테나는 배열을 이용하여 성능을 높이는 방법이 일부 사용되고 있으나 배열을 사용하는 경우 안테나의 크기가 커지는 단점이 있다. 그러므로 본 논문에서는 DSRC의 OBU에서 사용할 수 있는 소형이며 제작이 용이한 단순한 구조의 CPW 급전을 이용한 마이크로스트립 패치 안테나를 설계 하였다.

• Journal of Positioning, Navigation, and Timing
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• 제9권2호
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• pp.59-63
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• 2020

The antenna arrays are known to be effective for GPS anti-jamming and the performance can be improved further if a dual-polarized antenna array is used. However, when the Minimum Variance Distortionless Response (MVDR) beamformer is used as a signal processing algorithm for the dual-polarized antenna array, the anti-jamming performance can degrade in the presence of errors in the steering vector that is a key factor of the MVDR beamformer. Therefore, in this paper, the effect of the steering vector error on the anti-jamming performance of the dual-polarized antenna array is analyzed by simulations and the result is compared to that of the single-polarized antenna array.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2005년도 종합학술발표회 논문집 Vol.15 No.1
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• pp.289-292
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• 2005

Two planar inverted-F antenna (PIFA) arrays are proposed as an alternative model to generate input and radiation characteristics of two orthogonal oriented circular loops, which has polarization diversity, but inherent mechanical instability of two orthogonal loops, in particular, in installation and operation conditions. Two $1\times2$ PIFA sub-arrays are orthogonally placed on a ground plane and two different feeding networks are applied to control horizontal and vertical radiation current flows for each sub-array, respectively. Equivalence of scattering parameters and radiation patterns between two antennas are validated by the available commercial simulator.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권4호
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• pp.1292-1306
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• 2014

This paper proposes a space-polarization division multiple access (SPDMA) system that has limited feedback channels. The system simultaneously serves data streams to multiple mobile users through dual-polarized antenna arrays, by using pre-determined sets of precoding vectors that are orthogonal in both space and polarization domains. To this end, a codebook whose elements are sets of the precoding vectors is systematically designed based on the discrete Fourier transform (DFT) matrix and considering the power imbalance of polarized channels. Throughput of the SPDMA system is evaluated and compared to that of space division multiple access (SDMA) system, according to the various parameters including cross polarization discrimination (XPD). The results show that the throughput of SPDMA system outperforms that of SDMA in the environments of high XPD with many mobile users.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2002년도 춘계종합학술대회
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• pp.238-242
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• 2002

In this paper. we consider an OFDM system with cochannel interference and the use of adaptive antenna arrays to suppress such interference. Based on the conventional RLS criterion, we derive a new Recursive Least Square (RLS) adaptive beamforming algorithm for antenna arrays applied in an OFDM system. Computer simulation shows that. when applied to the OFDM system. the proposed algorithm is capable of combating cochannel interference in both AWGN channel and multipath Rayleigh fading channel with AWGN.

• Current Optics and Photonics
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• 제7권2호
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• pp.157-165
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• 2023

We propose a highly directional waveguide grating antenna for an optical phased array, achieving high directionality of more than 97% by interleaving the trenches with different etching depths in the silicon nitride layer, and adopting a multilayered structure. Meanwhile, the multilayered structure reduces the perturbation strength, which enables a centimeter-scale radiation length. The beam-steering range is 13.2°, with a wavelength bandwidth of 100 nm. The 1-dB bandwidth of the grating is 305 nm. The multilayered grating structure has a large tolerance to the fabrication variation and is compatible with CMOS fabrication techniques.