Earticle

본 논문에서는 GPS용 패치 안테나를 이용하여 안테나 빔의 방사패턴을 조정하는 방법에 대해 기술되었다. 안테나는 5개의 세라믹 기판에 구현된 전형적인 원형편파 패치 안테나를 사용 하였으며 PCB기판위에 배열 안테나로 제작 되었다. 안테나 배열은 가운데 하나의 요소가 배치되고 4개의 요소는 각 코너에 배치되는 구조이다. 특정한 방 향으로 GPS방해 신호가 도래 한다고 가정하고 그 방향의 안테나 방사 전력을 최소화 하는 방법을 제시하였다. CST MWS를 이용하여 시뮬레이션 하였으며 이를 기초로 안테나가 제작 되었고 기본적인 특성들이 측정되었고 그 결과가 제시되었다. 본 연구의 결과들을 살펴보면 방해전파 송신기로부터 방사되는 특정 방향의 방해신호를 본 연구에서 제 안하는 안테나를 사용하여 충분히 제거 할 수 있는 것을 알 수 있다.

In this paper, the implementation of a null-steering antenna array using GPS patch antennas is suggested. The antenna array consists of five patch antenna elements fabricated on the ceramic substrate. The antenna element proposed here is a typical circular polarization patch and a prototype patch array antenna is manufactured on the PCB. The antenna has one reference element located at the center and other four elements are placed at the corners. A null in the direction of the jamming signal can be produced by changing the phases of 4-elements. Simulation results of the array antenna by CST MWS are presented and discussed. The basic performances are measured and the results are shown. The results show that the antenna presented here can be used to remove the signals from the directions of any jammers.

본 논문에서는 상관형 위상비교(correlative interferometer) 방향탐지의 방위각 오차에 대해서 기술하였 다. 상관형 위상비교 방식은 잡음이 없는 이상적인 환경에서 계산한 위상과 잡음이 있는 실제 환경에서 측정한 위상 을 상호 비교하여 상관계수가 가장 큰 방위각을 전파 발신기의 방향으로 추정하는 방식이다. 5개의 안테나를 원형으 로 배치하는 원형 배열안테나(circular array antenna)를 이용하여 각 안테나 사이의 상관함수를 유도하여 잡음에 의한 방향탐지 오차를 유도하였다. 이 방법은 잡음에 대한 방탐오차가 매우 작고, 특히 전파 발사체와 방향탐지 장 치의 고도 차이가 큰 경우에도 방향탐지 오차가 작은 것으로 나타났다.

In this paper, we present an azimuth error analysis for the correlative interferometer direction finding. The correlative interferometer is a direction finding method that compares the theoretical and measured phase differences. The direction of the radio transmitter can be estimated by obtaining the maximum correlation between two data sets. We used a 5-element circular array antennas arranged in a circle. To derive the correlation function between antenna elements, we assume that the incident plane wave arrives from a certain angle and the phase difference of each antenna can be derived by comparing with the reference. The suggested direction finding gives a relatively accurate result even if the radio transmitter is located in the higher altitude.

This paper considers a broadband multicell system with key characteristics that base-stations and relays employ beamforming via large antenna arrays, as well as in-band full duplex relay operation. The signal to interference plus noise ratio gain (which is in excess of the maximum required for such a system) could be exploited either for reducing self-interference or the backhaul and access link transmitted powers. The presented results indicate that with a moderate front-to-back-ratio scenario for the antenna array, “small” antenna arrays with 8 elements can lower the requirement of full duplex self-interference cancellation by up to 55 dB, while large antenna arrays of 1024 elements will produce 100 dB reduction. Alternatively, for the same scenario, both the backhaul and access transmitted powers could be reduced by ∼55 dB and ∼25 dB with 1024 elements.

Steering vector and covariance matrix estimation mismatch along with moving jammer/platform, can affect the performance of null-steering beamformer. In this paper, by utilizing null-widening, null-deepening and diagonal loading shrinkage in space?time adaptive processing (STAP) structure, two methods for nullifying GNSS (global navigation satellite system) jamming/interference in cruise moving platforms are introduced. The enhanced performance of the proposed methods is investigated through numerical simulations. The results indicate improvement in the number of acquired GNSS satellites, in heavy jamming (GNSS denied) scenario, by reconstructing and acquiring at least 87% of satellites.

This paper provides a space temporal interference cancellation method for ultra wide-band (UWB) communication systems based on combination of tapped delay line array antenna and orthogonal matched filter. In order to reduce the interference from the other system using overlapping frequency band, space domain signal processing such as an array antenna has been proposed. However, principal array antenna cannot be applied to impulse radio (IR) UWB because IR-UWB does not have carrier signal. In this paper, we propose a novel tapped delay line array antenna combined with orthogonal matched filter detector. From the numerical evaluation, we show that the proposed system can make null direction to face to the interference signal direction. Additionally, we show that the proposed system can reduce interference signal even if the interference signal has equivalent pulse shape and equivalent incoming direction.

Since most studies for estimating an angle-of-arrival (AOA) based on the antenna array have considered the antenna array with a single configuration, they are not proper to simultaneously estimate AOAs of multiple signals with various frequencies. In this paper, we introduce a cascade AOA estimation technique consisting of CAPON and Beamspace Multiple Signal Classification (MUSIC), based on a Combined Array Antenna (CAA) with Uniform Rectangular Frame Array (URFA) and Uniform Circular Array (UCA), for enhancing the above problem. In addition, we provide the computational complexity analysis for showing the low computational complexity of this technique comparing to the conventional technique.

This paper newly proposes a direct antenna array control approach to reduce channel spatial correlation for multiuser spatial multiplexing. Conventional rectangular arrays can form three dimensional beams and have superior signal separation performance compared to linear arrays. However, when the arrival angles of some signals are close, the signal separation (interference cancellation) performance deteriorates since the projection points onto horizontal/vertical axes of several antenna elements overlap and spatial resolution along each axis is degenerated. The key proposal is to improve signal separation performance by mechanically changing the positional relationship of antenna elements. The proposed scheme can achieve better Bit Error Rate (BER) performance by searching the optimal antenna rotation angle.

Adaptive smart antenna arrays are used for cellular communication. This paper presents a comparative study of beamforming techniques for adaptive smart antenna using hybrid algorithms like Simple Matrix Inversion with Recursive Least Square (SMI-RLS) and Least Mean Square with Recursive Least Square (LMS-RLS) algorithm. The results are compared on the basis of null depth and error plot for different signal –to-noise (SNR) values, ranging from high to low values of SNR for heavily faded case..

위성방송수신 및 위성 양방향 인터넷, VSAT 등의 위성통신서비스를 차량 이동 시에도 이용할 수 있기 위해서는 차량에 탑재하기 용이하도록 소형이며 높이가 낮은 안테나 구조가 요구된다. 또한 중위도 지역에서 평면 안테나 상태로 45도 틸트 특성을 갖고, Ku 밴드의 위성통신용으로 충분한 고이득을 얻기 위해, 빔폭이 좁고 사이드로브가 적으며 저손실 구조의 배열안테나 개발이 필요하다. 본 논문에서는 이러한 성능을 만족시키기 위해, 진행파형 누설파 모드를 기초로 한 수직 편파로 동작하는 도파관 종방향 슬롯 배열안테나를 제안하였다. 16개 누설파 소자의 배열안테나 이득은 30 dBi 이었으며, 빔폭은 4.9도, 사이드로브 레벨은 -20 dB 이하, 중심주파수에서 빔틸트 각도는 45도를 얻었다. 급전선로는 도파관의 병렬급전 방식으로 설계하여 광대역, 저손실 특성을 얻을 수 있었다.

Small size and low profile antenna for mobile vehicular-top-mounted is needed in satellite communication services such as DBS, Satellite Internet and VSAT. In middle latitudes, the development of an array antenna which has the conformal, low profile and 45 degree beam tilted configuration, and has the high gain with sharp beamwidth, low sidelobe and low loss is required for Ku-band satellite communication. In this paper, in order to meet with these performances, an array antenna consisting of the vertical polarized waveguide longitudinal slots based on the leaky-wave mode of traveling wave antenna is proposed. An array antenna consisting of 16 leaky-wave elements is showing 30 dBi of gain, 4.9 degree of beamwidth, below than -20 dB of sidelobe level, 45 degree of beam tilt angle in center frequency. Feed network designed by waveguide cooperated feed shows good performance of wideband and low loss.

The structure of MMSE receiver front-ended by CMA(Constant Modulus Array) array working in CDMA forward link which is applicable to LEO spread spectrum satellite communication system is proposed. By using the despreaded pilot signal of forward link as a reference signal, the CMA array can capture multi-path signals securely even in severely faded LEO satellite channel. The remaining MAI (Multiple Access Interference) is cancelled by the cascaded MMSE receiver. Besides theoretical development, through relevant computer simulation, it is proved that the proposed system shows much better BER performance than any other possible candidate systems. As a spatio-temporal receiver mounted on a mobile vehicle, the proposed system also reduces implemental cost and complexity by adopting the simplest algorithm for its spatial and temporal domain processing.

본 논문에서는 본 논문에서는 GPS 주파수 블록 중 L1블록인 1.575GHz에서 동작하는 GPS 수신 안테나를 설계하였다. 기존 GPS 수신 안테나는 고정·광역빔으로 차량이나 탑재체에서 이동할 경우 빔의 적응성이 다소 떨어지는 단점을 보인다. 이를 보완하기 위하 여 안테나의 이득을 높이고 전기적 위상을 조절해 빔을 조향할 수 있도록 하여 빔의 적응성이 생기도록 하였다. 설계한 안테나는 마이크로스트립 패치 안테나로서 방사소자를 배열형태로 확장하여 이득을 높이고 이에 CRLH 위상변위기를 결합하여 각 방사소자 에 위상차 급전이 가능하도록 하였다. 또한 제시된 CRLH 위상변위기는 단일 모델에서 가변 C의 조정으로 여러 가지 위상출력이 가능하도록 설계하여 버랙터 다이오드와 결합시 실시간으로 빔을 조정할 수 있어 항 재밍 기능도 갖출 수 있음을 보였다.

This paper presents an approach to enable a typical GPS receiver to be much less susceptible to intentional disruption such as jamming and change in link environment. In order for the GPS receiver to cope with jamming and to get adaptivity, a 4x4 beamforming antenna is designed using metamaterials. The design results show the antenna gain much higher than 5 dBi and the movable beam.