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Interferometry And Synthesis In Radio Astronomy

The development of light detection and ranging, Radar, camera, and other advanced sensor technologies inaugurated a new era in autonomous driving. However, due to the intrinsic limitations of these sensors, autonomous vehicles are prone to making erroneous decisions and causing serious disasters. At this point, networking and communication technologies can greatly make up for sensor deficiencies, and are more reliable, feasible and efficient to promote the information interaction, thereby improving autonomous vehicle’s perception and planning capabilities as well as realizing better vehicle control. This paper surveys the networking and communication technologies in autonomous driving from two aspects: intra- and inter-vehicle. The intra-vehicle network as the basis of realizing autonomous driving connects the on-board electronic parts. The inter-vehicle network is the medium for interaction between vehicles and outside information. In addition, we present the new trends of communication technologies in autonomous driving, as well as investigate the current mainstream verification methods and emphasize the challenges and open issues of networking and communications in autonomous driving.

Networking and Communications in Autonomous Driving: A Survey

An efficient method based on bees algorithm (BA) for the pattern synthesis of linear antenna arrays with the prescribed nulls is presented. Nulling of the pattern is achieved by controlling only the amplitude of each array element. Numerical examples of Chebyshev pattern with the single, multiple and broad nulls imposed at the directions of interference are given to show the accuracy and flexibility of the BA.

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Amplitude-Only Pattern Nulling of Linear Antenna Arrays with the Use of Bees Algorithm

This article covers recent advances in the fusion of metasurface antenna design and computational imaging (CI) concepts for the realization of imaging systems that are planar, fast, and low cost. We start by explaining the operation of metamaterial antennas which can generate diverse radiation patterns. Their advantages and distinctions from previous antennas are elucidated. We then provide an intuitive overview of the CI framework and argue that metamaterial antennas are a near ideal platform for implementing such schemes at microwave frequencies. We describe two metamaterial antenna implementations: frequency diverse and electronically reconfigurable. The tradeoffs governing the design and operation of each architecture are examined. We conclude by examining the outlook of metamaterial antennas for microwave imaging and propose various future directions.

/pdf/review-of-metasurface-antennas-for-computational-microwave-27eqb4fdgx.pdf

Review of Metasurface Antennas for Computational Microwave Imaging

The use of large-size antenna arrays to implement pencil-beam forming techniques is becoming a key asset to cope with the very high throughput density requirements and high path-loss of future millimeter-wave (mm-wave) gigabit-wireless applications. Suboptimal beamforming (BF) strategies based on search over discrete set of beams (steering vectors) are proposed and implemented in present standards and applications. The potential of fully adaptive advanced BF strategies that will become possible in the future, thanks to the availability of accurate localization and powerful distributed computing, is evaluated in this paper through system simulation. After validation and calibration against mm-wave directional indoor channel measurements, a 3-D ray tracing model is used as a propagation-prediction engine to evaluate performance in a number of simple, reference cases. Ray tracing itself, however, is proposed and evaluated as a real-time prediction tool to assist future BF techniques.

Ray-Tracing-Based mm-Wave Beamforming Assessment

In this article, an efficient method for the pattern synthesis of the linear antenna arrays with the prescribed null and multi-lobe Beamforming is presented. Multi-lobe pattern and adaptive nulling of the pattern is achieved by controlling only the phase of each array element. The proposed method is based on the Sequential Quadratic Programming (SQP) algorithm and the linear antenna array synthesis was modelled as a multi-objective optimization problem. Multi-objective optimization is concerned with the maximization (or minimization) of a vector of objectives functions in the directions of desired signal that can be subject of a number of constraints (in our case, the constraints can be imposed as the null in the direction of interfering signal). To verify the validity of the technique, several illustrative examples of uniform excited array patterns with the main beam is placed in the direction of the useful signal and null is placed in the direction of potential interferers, and multi-beam patterns are demonstrated.

/pdf/smart-antenna-array-patterns-synthesis-null-steering-and-2q2a8fahj2.pdf

Smart antenna array patterns synthesis: null steering and multi-user beamforming by phase control

A compact multiband antenna system using a dielectric resonator antenna (DRA) is presented in this paper. Designed to be integrated in a tablet, it is not only heavily miniaturized (λ0/15×λ0/38×λ0/94 at 800 MHz), but also able to cover three frequency bands for different wireless applications (DVB-H, WiFi and WiMAX). Since a reconfigurable radiation pattern can result in an improved quality and reliability of wireless links, two DRAs have been integrated to implement this feature on the three frequency bands. These improvements are demonstrated by the presentation of the correlation coefficient and the effective diversity gain, both measured in a reverberation chamber. The experimental measurements are in very good agreement with the simulated ones. Good overall performances are obtained, and the requirements of all three applications are perfectly met. Moreover, the antenna operative frequencies are independent of the ground plane dimensions, making this system a very good candidate for all kinds of mobile devices.

Compact and Multiband Dielectric Resonator Antenna With Pattern Diversity for Multistandard Mobile Handheld Devices

Recent work proved the effectiveness of a new concept, namely compressive synthetic aperture interferometric radiometer, which aims to reduce the number of RF chains of an interferometric radiometer by means of a passive microwave component The device is used for coding $M$ antenna signals into $N$ ( $N~\ll ~M$ ) measured waveforms Thereafter, a decoding process is applied to retrieve the antenna signals necessary to compute the basic observables of an interferometer, namely complex visibilities Initially, a Fourier algorithm was applied to reconstruct the images, and nonetheless, this kind of imaging algorithm ignores the visibility observation errors, which cause blurring and distortion effects in the images Herein, a generalized visibility equation is given while considering $M$ antennas associated with $N$ receivers Then, a linear relationship between these visibility samples and the noise source brightness temperature is established, and a regularization method is applied to compute the source image Furthermore, the impact of the device on the reconstructed images is studied by means of numerical analysis as well as by experiment measurements performed in the $S$ -band (2–4 GHz) The results confirm that the computational approach provides accurate reconstructed images compared with those obtained with the Fourier algorithm

Computational Imaging for Compressive Synthetic Aperture Interferometric Radiometer

Emulation methodology of multiple clusters channels for evaluating wireless communication devices over-the-air (OTA) performance is investigated. This methodology has been used along with the implementation of the SIMO LTE standard. It consists of evaluating effective diversity gain (EDG) level of SIMO LTE-OFDM system for different channel models according to the received power by establishing an active link between the transmitter and the receiver. The measurement process is set up in a Reverberation Chamber (RC). The obtained results are compared to the reference case of single input-single output (SISO) in order to evaluate the real improvement attained by the implemented system.

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3GPP Channel Model Emulation with Analysis of MIMO-LTE Performances in Reverberation Chamber

In a previous work, a novel technique for angle of arrival (AOA) measurement was proposed. This technique consists of sweeping the angular domain with one antenna, step by step, such that at each measurement step the received signal voltage at the rotating antenna (sensor) is measured. The signal voltage vector is the convolution between the antenna electric field pattern and the AOAs (magnitude and phase) of the incident wave. In this letter, a denoising CLEAN algorithm is modified and applied to this technique in order to eliminate spurious peaks and accurately find the AOAs of incoming waves. A set of measurements is made to evaluate the proposed algorithm. The results show the effectiveness of the denoising algorithm in reducing the noise level; a high angular precision in measured AOAs is noticed.

Moctar Mouhamadou

Papers

Smart antenna array patterns synthesis: null steering and multi-user beamforming by phase control

Compact and Multiband Dielectric Resonator Antenna With Pattern Diversity for Multistandard Mobile Handheld Devices

Computational Imaging for Compressive Synthetic Aperture Interferometric Radiometer

3GPP Channel Model Emulation with Analysis of MIMO-LTE Performances in Reverberation Chamber

A New CLEAN Algorithm for Angle of Arrival Denoising