Adaptive Array Antenna System Research Articles

Microwave Loaded Line Phase Shifter Design for Beam-steering Applications in Adaptive Array Antenna System

In this scholarly work, we present innovative design for Loaded Line Phase Shifter (LLPS) which is tailored for the dynamic requirements of beam-steering adaptive antenna arrays. This phase shifter plays a pivotal role by installing a precise 90o phase shift into the elements of the adaptive array, enabling beam switching in diverse directions. In the absence of the Loaded Line Phase Shifter, the S-Parameter values, specifically S11 and S21, are recorded at 158.88o and -23.72o, respectively. Upon integrating the LLPS into the transmission line, a remarkable transformation occurs with S11 and S21 values transitioning to -143.28o and -53.03o, correspondingly. These results hold great promise for the practical applications of adaptive antenna arrays.

Optical Adaptive Antenna Array for Multiuser Mobile Optical Communication

In this paper, an optical adaptive antenna array system for multi-user optical mobile communication is studied. A coherent signal source is embedded in a spherical optical phased cell array with an external spherical lens system. The system can predict the signal power of the receiving end according to the channel transfer matrix and perform power compensation when transmitting the signal. Correspondingly, a pure phase lossless desired light field recovery algorithm is proposed and used for space division multiple access and free power allocation of antenna array systems. A small-scale optical adaptive antenna array experimental system is built and tested with good performance and consistent with the expected results.

Estimating Angle of Arrival (AOA) for Wideband Signal by Sensor Delay Line (SDL) and Tapped Delay Line (TDL) Processors

Angle of arrival (AOA) estimation for wideband signal becomes more necessary for modern communication systems like Global System for Mobile (GSM), satellite, military applications and spread spectrum (frequency hopping and direct sequence). Most of the researchers are focusing on how to cancel the effects of signal bandwidth on AOA estimation performance by using a transversal filter (tap delay line) (TDL). Most of the researchers were using two elements array antenna to study these effects. In this research, a general case of proposed (M) array elements is used. A transversal filter (TDL) in phase adaptive array antenna system is used to calculate the optimum number of taps required to compensate these effect. The proposed system uses a phase adaptive array antenna in conjunction with LMS algorithm to work an angle of arrival (AOA) estimator for wideband signals rather than interference canceller. An alternative solution to compensate for the effect of signal bandwidth is proposed by using sensor delay line (SDL) instead of fixed delay unit since it has variable time sampling in the time domain and not fixed time delay, depending on the angle of arrival of received signals. The proposed system has the ability to estimate two parameters for received signals simultaneously (the output Signal to Noise Ratio (SNR) and AOA), unlike others systems which estimate AOA only. The comparison of the simulation results with Multiple Signal Classification (MUSIC) technique showed that the proposed system gives good results for estimating AOA and the output SNR for wideband signals. (SDL) processor shows better performance result than (TDL) processor. MUSIC technique with both (SDL) and (TDL) processors shows unacceptable results for estimating (AOA) for the wideband signal. 

Hybrid Amplitude Control Antenna Array System for Energy Efficient W-CDMA Network with Adaptive Coverage and Capacity

This paper introduces a novel technique and mathematical formulation of two dimensional elastic footprint variations and adaptive sector configuration variations by using a hybrid adaptive amplitude control antenna array system. The antenna array system can control the elevation beam-widths from 6.84° to 13° and the azimuth beam-widths from 33° to 93° for obtaining the adaptive capacity and coverage. The work illustrates the application of the antenna array system in the energy efficient W-CDMA network. The antenna array half-power beam width variation is achieved by using the antenna array amplitude control and co-located multiple antenna array switching. The Node-Bs can adaptively switch to three, four, five, six and non uniform sector configurations with the antenna array beam width control and adaptive neighbor relations. Sector configurations will vary according to the pre-defined specific traffic loading percentages out of Node-B’s total channel capacity to reduce the energy consumption of the entire network. The paper introduces an adaptive footprint overlaps shifting technique, where the sector with less traffic load will expand its footprint towards the sector with higher traffic load and the sector with higher traffic load will shrink its footprint by maintaining a fixed footprint overlaps to improve the coverage and the capacity of the network. The footprints overlap shifting is applicable only for the active sector antennas facing each other. The results confirm that the proposed antenna array system outperforms the automatic tilt optimization and can control coverage, capacity and improve the energy efficiency of the W-CDMA network.

이동 목표물 추정 정확도를 향상시키기 위한 고 분해능 최적 빔 지향 패턴에 관한 연구

Method a target estimation in spatial are mobile wireless communication using network cell and GPS. It have much error that mobile wireless communication depend on cell size. GPS method can't find a target in shadow and inner area. In this paper, we estimate a target as direction of arrival method using adaptive array antenna system. Adaptive array antenna system can obtain desired signal to remove other signal This paper studied digital beamforming method in order to estimation a target. Proposed method is modified optimum weight and antenna error correction to estimation an optimal receive signal. Digital beamforming method decided a signal phase and amplitude from received signal on array antenna element. But if it is not to do error correction of received signal, system performance have decreased. Firstly, we proposed modified optimum weight in order to finding desired target. Secondly, we are error correction of antenna incident signals by optimal weight before digital beamforming method. Thirdly, throughly simulation, we showed that system performance of proposed method compare proposal method with general method. It have improved resolution of estimation target to good performance more proposed method than general method.

향상된 신호 추정을 위한 안테나 오차 보정 과 수정된 최적 가중치를 이용한 디지털 빔 형성 성능 분석에 관한 연구

Method a target estimation in spatial are mobile wireless communication using network cell and GPS. It have much error that mobile wireless communication depend on cell size. GPS method can`t find a target in shadow and inner area. In this paper, we estimate a target as direction of arrival method using adaptive array antenna system. Adaptive array antenna system can obtain desired signal to remove other signal This paper studied digital beamforming method in order to estimation a target. Proposed method is modified optimum weight and antenna error correction to estimation an optimal receive signal. Digital beamforming method decided a signal phase and amplitude from received signal on array antenna element. But if it is not to do error correction of received signal, system performance have decreased. Firstly, we proposed modified optimum weight in order to finding desired target. Secondly, we are error correction of antenna incident signals by optimal weight before digital beamforming method. Thirdly, throughly simulation, we showed that system performance of proposed method compare proposal method with general method. It have improved resolution of estimation target to good performance more proposed method than general method.

Review ofFuzzy Logic based Adaptive Antenna Array system

Review ofFuzzy Logic based Adaptive Antenna Array system

선형 제한 조건의 최적 가중 벡터에 대한 연구

본 논문에서는 적응 배열 안테나 시스템에서 간섭 및 재밍 신호를 제거하기 위해서 최적 가중 벡터를 연구하였다. 최적 가중 벡터는 선형 제한 조건에서 최소 분산 알고리즘과 비용함수를 적용시켜 구하였고, 목표물의 신호를 정확히 추정하였다. 적응 배열 안테나 시스템은 간섭 및 재머전력을 감소시키고 신호대 잡음비를 향상시키는 시스템이다. 적응 배열 안테나 시스템은 각 안테나 배열 소자의 출력이 탭(Tap)을 거쳐 지연되고 각 탭에 복소 가중치가 곱해져서 최종적으로 하나의 복합신호를 만든다. 최적의 가중치를 구하기 위해서 본 논문에서는 입력 공분산 행렬의 최적 가중벡터를 이용하였다. 본 논문에서 제안된 알고리즘으로 모의 실험한 결과 분해능은 <TEX>$3^{\circ}$</TEX>이하로 향상되었으며 부엽은 약 10 dB 감소하였음을 입증하였다. 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 <TEX>$3^{\circ}$</TEX>, and sidelobe is decreased about 10 dB.

A New On-Line/Off-Line Adaptive Antenna Array Beamformer for Tracking the Mobile Targets

An adaptive antenna array system adjusts the main lobe of radiation pattern in the direction of desired signal and points the nulls in the direction of undesired signals or interferers. The essential goal of beamforming is to reduce the complexity of weighting process and to decrease the time needed for adjusting the antenna radiation pattern. In this article a new adaptive weighting algorithm is proposed for both least mean squares (LMS) and constant modulus (CM) algorithms. It is appropriate and applicable for antenna array systems with moving targets and also mobile applications as well as sensor networks. By predicting the relative velocity of source, the next location of the source will be estimated and the array weights will be determined using LMS or CM algorithm before arriving to the new point. For the next time associated to the new sampling point, evaluated weights will be used. Furthermore, by updating these weights between two consecutive times the effects of error propagation will be eliminated. Therefore, in addition to reduction in computational complexity at the time of weight allocation, relatively accurate weight allocation can be obtained. Simulation results of this investigation show that the angular error related to both LMS-based and CM-based algorithms is less than the conventional LMS and CM algorithms at different signal to noise ratios (SNRs). On the other hand, due to considering off-line process, online computational complexity of new algorithms is slightly low with respect to previous ones.

상관성 간섭에서 표적의 입사각 추정 방법에 대한 연구

적응 배열 안테나 시스템은 간섭신호 방향으로 영점을 형성하여 표적신호를 추정한다. 그러나 적응 배열 안테나 시스템에 상관성 간섭신호가 입사된다면 표적신호를 간섭신호로 간주하여 시스템의 성능이 급격히 감소되고, 지향 오차에 민감하여 주빔이 표적신호의 입사방향을 지향하지 못한다. 본 논문에서는 고차제한조건과 지향오차수정방법을 결합하여 빔형성 알고리즘을 제안하였다. 그리고 제안한 알고리즘으로 자유도 손실을 최소화하고 간섭신호와 지향오차를 감소시켰다. 모의실험을 이용하여 제안 알고리즘과 기존 알고리즘의 성능을 비교 분석하였다. 본 논문에서 제안한 알고리즘은 신호 입사각을 정확히 추정하지만 기존의 알고리즘은 약 <TEX>$0.8^{\circ}$</TEX>의 오차가 발생하였다. Adaptive array antenna system estimates target signal, as making a null pattern toward the interference signal. However, receiving a coherent interference signal at adaptive array antenna system, as target signal is regarded as interference signal, the performance of system rapidly decreases. The main beam does not direct an incidence direction of target signal due to sensitivity in directivity error. This paper proposes beamforming algorithm which combines high order limit condition and directivity error modify method. And it minimizes degree of freedom and decreases interference signal and directivity error using proposed algorithm. This paper compares and analyzes the performance of proposed algorithm and general algorithm using simulation. In this paper, the proposed algorithm correctly estimates an incident angle, but general algorithm occurs an error of about <TEX>$0.8^{\circ}$</TEX>.

고유 공간 빔형성 알고리즘을 이용한 AT-DMB 수신 방법

고전송률 지상파 디지털멀티미디어 방송 즉 Advanced T-DMB 방송 (이하 AT-DMB)은 기존 T-DMB와 역호환성을 유지하면서 전송률을 최대 2 배로 높이기 위한 방법의 하나로 개발 되고 있다. AT-DMB 시스템은 T-DMB의 DQPSK 변조신호에 새로운 변조가 적용된 신호를 중첩하는 계층변조를 적용 한다. AT-DMB의 계층변조에는 새로 추가하는 향상 계층신호로 이동성에 강한 BPSK 신호를 더하는 B 모드와 보다 많은 데이터 전송을 위한 QPSK 신호를 더하는 Q 모드가 있다. T-DMB와 역호환성 유지 및 방송권역 축소를 최소화하기 위해 향상 계층의 신호를 작게 유지 해야 한다. 이 때문에 새로 추가된 향상계층 신호는 전송채널에 존재하는 페이딩에 의해 쉽게 왜곡될 수 있다. 이를 위해 향상 계층의 신호에는 기존의 길쌈 부호 보다 에러 정정 능력이 뛰어난 터보 부호를 채용하고 있다. 그러나 AT-DMB의 경우 기본계층과 향상계층 사이에 존재하는 QEF(quasi error free) SNR(signal to noise ratio) 차이로 인해 방송권역에 차이가 발생할 수 있다. 따라서 본 논문에서는 별도의 송신 출력의 증가 없이 AT-DMB 신호를 안정적으로 수신할 수 있는 빔형성 이득과 다이버시티 이득을 동시에 얻을 수 있는 고유 공간 빔형성 기법을 적용한 AT-DMB 수신 방법을 제안한다. 제안한 고유 공간 빔형성 기법이 적용된 AT-DMB 수신 방법에 대해 컴퓨터 시뮬레이션을 통해 성능을 검증하였고 그 적용성을 제시하였다. AT-DMB system has been developed to increase data rate up to double of conventional T-DMB in the same bandwidth while maintaining backward compatibility. The AT-DMB system adopted hierarchical modulation which adds BPSK or QPSK signal as enhancement layer to existing DQPSK signal. The enhancement layer signal should be small enough to maintain backward compatibility and to minimize the coverage loss of conventional T-DMB service coverage. But this causes the enhancement layer signal of AT-DMB susceptible to fading effect in transmission channel. A turbo code which has improved error correction capability than convolutional code, is applied to the enhancement layer signal of the AT-DMB system for compensating channel distortion. However there is a need for other solutions for better reception of AT-DMB signal in receiver side without increasing transmitting power. In this paper, we propose adaptive array antenna system with Eigen-space beamforming algorithm which benefits beamforming gain along with diversity gain. We analyzed the reception performances of AT-DMB system in indoor and mobile environments when this new smart antenna system and algorithm is introduced. The computer simulation results are presented along with analysis comments.

이동형 위성 관제를 위한 위성 위치 파악 및 빔 성형 기법

본 논문은 이동 위성 관제 시스템을 위한 적응 배열 안테나 시스템에서 위성의 위치 파악과 빔 성형 기법에 관하여 서술한다. 이동시 위성 관제를 수행하려면 이동체에 대한 위성의 상대적 위치를 실시간적으로 파악하여 적응형 어레이 안테나 주 빔(main beam)을 위성으로 향하게 하여 위성 관제를 수행하여야 한다. 이를 위해서 고 해상도 전파 방향 탐지 알고리즘 중의 하나인 MUSIC(Multiple Source Idetification) 알고리즘을 사용하였고, 이에 대한 성능 분석과 아울러 구현시 위상 변환기의 양자화에 따른 영향에 대하여 분석하였다. 본 논문은 위상 배열 안테나를 이용하여 이동 위성 관제 시스템을 구현할 수 있음을 보여줌으로써 국내의 이동 위성 관제 시스템을 개발에 중요한 자료가 될 수 있다. This paper describes the technique of satellite direction finding and main beam steering of the adaptive array antenna system which is used for mobile TT&C(Tracking Telemetry&Command) system. To be able to control the satellite on mobile vehicle while moving, the relative directional information of the satellite to the mobile vehicle is necessary to make main beam to the direction of satellite. To do this MUSIC, which is one of the super-resolution algorithm of wave direction finding, is used and then the performance analysis and quantization problem of phase shifter are addressed. This paper is valuable in the respect of showing feasibility of designing the moble TT&C using adative array antenna system.

Experiment and Simulation Results of Adaptive Antenna Array System at Base and Mobile Stations in Mobile Environment

In a time division duplex (TDD) based adaptive antenna array (AAA) and space division multiple access (SDMA) systems, array weights determined from the up-link signals can be applied to the down-link signal transmission because of the channel reciprocity. However, under time-varying fading conditions, for example that created by a rapidly moving mobile station (MS), the channel change between the array weight determination time in the up-link and the down-link signal transmission degrades the accuracy of the array weight. Thus, the spectral efficiency of the system degrades in the down-link. In this paper, we introduce a prototype of an MS with a 2-element antenna array and present the down-link mobility performance results of computer simulations and field experiments in a field trial system of i-Burst, which is a TDD based wireless broadband system employing the AAA/SDMA techniques at the base station. Both results show that adaptive antenna processing at an MS is effective in improving the down-link mobility performance of TDD-AAA/SDMA systems.

Performance of Feedback-Type Adaptive Array Antenna in FDD System with Rake Receiver

The performance of a feedback-type adaptive array antenna (AAA) system placed only at a base station (BS) in an FDD/DS-CDMA system remains insufficiently clear. We evaluate the performance of this system by considering the effect of a rake receiver, spacing distance between antennas, the maximum Doppler frequency (f d ), and control delay time (T d ) on BER performance. In this system, the mobile station (MS) determines optimum weights of antenna elements and sends them back to BS as feedback information. We assume that the optimum weights are not quantized. Thereby, we estimate the performance degradation of 3GPP transmit diversity system, where the feedback information is quantized using a few bits. Computer simulation results show that the rake receiver achieves better BER performance because of the time diversity effect with rake receiver. The AAA with a wide antenna spacing gives high diversity gain for the received signals. For a high value of f d T d , BER performance becomes worse because weighting factors cannot follow the changing speed of channel characteristics. The degradation in performance of a 3GPP system is clarified.

LMI-Based Design of LMS Adaptive Array Antenna Systems

LMI-Based Design of LMS Adaptive Array Antenna Systems

Enhancement of Data Throughput in the AMC-Employed DS-CDMA Systems through Suppression of Channel Frequency Selectivity by a MTMR Antenna System

SUMMARY In this paper, a new algorithm for MTMR adaptive array antenna (AAA) system combined with analog-type transmit power control (TPC) is proposed for DS-CDMA systems in order to employ high level modulation schemes like 64 QAM in wireless multimedia services. A conventional AAA system considering the strongest path as a target path cannot work effectively when angular dispersion between the strongest path and other delayed paths is large, that is, beam selectivity is so small due to severe frequency selective multipath fading. So, in order to solve such a beam selectivity problem, a beam directivity control scheme using a path manipulation technique is introduced for the BS and MS AAA combining in this paper, along with analog-type TPC. It utilizes virtual delay profiles which are modified from the measured complex delay profile and selects a desired path giving the maximum DUR with an optimized weight vector for BS and MS beamforming. We will show through computer simulation that the proposed scheme is very effective in enhancing the data throughput at the downlink of wideband DS-CDMA systems as compared with the conventional system.

Data throughput enhancement by frequency selectivity suppression in downlink DS-CDMA beamforming systems

A novel multi-transmit and multi-receive (MTMR) adaptive array antenna (AAA) system combined with analogue-type transmit power control (TPC) to suppress channel frequency selectivity is proposed. This technique increases throughput with adaptive modulation and coding (AMC) employed at the downlink of direct-sequence code division multiple access (DS-CDMA) systems. The proposed scheme employs beam directivity control using a path manipulation technique. Its superiority over the conventional AAA systems is demonstrated by computer simulation.

New adaptive beamforming algorithm employing forward/backward averaging and signal enhancement schemes

We introduce the new adaptive beamforming algorithm which improves the performance of an adaptive antenna array system through a forward/backward averaging scheme of the post-correlation signal vector and a signal enhancement scheme using Hermitian Toeplitzation of an array covariance matrix in DS/CDMA. A forward/backward averaging scheme decorrelates the received correlated signal after despreading in a matched filter and the Hermitian Toeplitzation scheme enhances the performance of the received signal by removing the undesired effect obtained from an array covariance matrix estimation. It is shown through simulation results that the performance of the proposed algorithm is very superior to that of the conventional Wiener maximal ratio combining (MRC) algorithm.

Combinations of an adaptive array antenna and a canceller of interference for direct-sequence spread-spectrum multiple-access system

In the realization of code-division multiple access based on a spread-spectrum communication system, i.e. spread-spectrum multiple access (SSMA), reduction of cochannel interference is an important problem. An adaptive array antenna system is proposed that includes a cancellor of cochannel interference, which can improve performance by a combination of temporal and spatial filtering. While the adaptive array suppresses interference sources with arrival angles different from those of the desired user, the adaptive digital filter-canceller rejects those whose arrival angles are the same as those of the desired user. The proposed system can achieve stable acquisition and low error rate of demodulated data even in a heavy-interference channel where a conventional array antenna system cannot achieve satisfactory acquisition.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Performance of a modified feedback loop adaptive array with TVRO satellite signals

Performance of an experimental adaptive antenna array system is evaluated using television receive-only (TVRO) satellite signals. The experimental system is a sidelobe canceller with two auxiliary channels. Modified feedback loops are used to enhance the suppression of weak interfering signals. The modified feedback loops used two spatially separated antennas, each with an individual amplifier for each auxiliary channel. Thus, the experimental system uses five antenna elements. Instead of using five separate antennas, a reflector antenna with multiple feeds is used to receive signals from various TVRO satellites. The details of the earth station are given. It is shown that the experimental system can null up to two signals originating from interfering TVRO satellites while receiving the signals from a desired TVRO satellite.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>