Antenna Beam Direction Research Articles

Multi-Beam Satellite Seeking and Acquisition Method for Satcom-on-the-Move Array Antenna on a High Maneuverability Carrier

When the carrier of the Satcom-on-the-Move (SOTM) antenna is in a high maneuvering state of motion, the accuracy of the array antenna beam pointing towards the satellite may decrease, which may cause a decline in communication effectiveness for SOTM or even cause the antenna to deviate from the target satellite and lead to communication interruption. This paper proposes a multi-beam searching and capturing method for SOTM array antennas, which divides the array antenna into multiple parts to form multiple independent and controllable sub-beams. When the SOTM carrier is in a high maneuvering state of motion, multiple sub-beams are obtained by dividing the array antenna, thus obtaining multiple points in the radiation pattern. We designed an optimal pointing analyzer, which calculates the SOTM array antenna beam direction based on whether the SOTM antenna is pointing towards the satellite and utilizes different approaches for processing. Experimental verification was conducted for the proposed scheme. The experimental results show that if the antenna beam does not lose the satellite, the proposed scheme can obtain better communication quality compared to conventional schemes. If the SOTM antenna beam loses the satellite and causes communication interruption, the proposed scheme in this paper can capture the satellite faster than conventional schemes. The experimental results demonstrate the effectiveness of the proposed scheme.

Joint Direct Estimation of Emitter Location and Antenna Beam Direction Based on Baseband Reconstruction

This paper addresses the problem of locating a stationary noncooperative emitter using multiple moving receivers. A signal baseband reconstruction based algorithm is proposed to locate the emitter directly from the received signals, without assuming static delay and Doppler shift in any observing interval. Besides the information of time-differences-of arrival (TDOA) and frequency-differences-of-arrival (FDOA), the received signal strength (RSS) information is further utilized when the source emits signals in free space with an omni antenna. In a more complex scenario where the emitter adopts a directional antenna, an iterative algorithm is proposed to jointly estimate the emitter location and its antenna beam direction, where a traditional direct position determination (DPD) method is used to initiate the iteration. The Cramér-Rao lower bounds (CRLBs) of the emitter position and the beam direction are derived. Three numerical cases are included to investigate the performance of the proposed algorithms. The signal baseband reconstruction based DPD algorithm shows improved applicability when the assumption of static time delay and Doppler shift is inappropriate and performs similarly with the classical DPD methods when the assumption holds. In case of free space propagation, it shows that the localization accuracy can be improved when RSS is further utilized. When the transmitting beam is directional, however, simply ignoring the directivity characteristics would lead to nonnegligible localization biases. By jointly estimating the emitter location and antenna beam direction, the RSS information can be effectively utilized to improve the localization accuracy, and a much more accurate estimation of beam direction can be obtained simultaneously.

Aerial Clutter Suppression in a Wind Profiler Radar With Antenna Subarrays

Undesired echo from a flying object (aerial clutter) significantly contaminates the received signal of a wind profiler radar (WPR) because it has high intensity and spreads over a wide Doppler velocity range. In this study, results of aerial clutter mitigation obtained by applying adaptive clutter suppression (ACS) to a 1.3-GHz WPR are shown. The 1.3-GHz WPR used in this study has a main antenna comprising 13 antenna subarrays (MSAs). five-element Yagi-Uda antennas were also used as antenna subarrays for detecting clutters from low elevation angles (CSAs). The CSAs were used only in reception and installed so that they covered most of the horizontal directions and the horizontal and vertical polarizations. The directionally constrained minimization of power (DCMP) method was used as the adaptive signal processing to mitigate clutter. By the DCMP method, the weighted sum of the signals collected by 13 MSAs and 11 CSAs was computed so that the power of output signals was minimized under the constraint of constant gain in the antenna beam direction. Results of a case study for an aerial clutter from a low elevation angle at 17:04:37 on October 1 2020 showed that an overlap of the aerial clutter over a desired echo (i.e., clear-air echo) was solved by decreasing the aerial clutter whose peak intensity was ~24 dB greater than that of the clear-air echo. In a case study at 09:30:27 on September 18 2020, effects of the DCMP method on the processed results were discussed.

Radio Channel Capacity with Directivity Control of Antenna Beams in Multipath Propagation Environment.

The basic technology that will determine the expansion of the technical capabilities of fifth generation cellular systems is a massive multiple-input-multiple-output. Therefore, assessing the influence of the antenna beam orientations on the radio channel capacity is very significant. In this case, the effects of mismatching the antenna beam directions are crucial. In this paper, the methodology for evaluating changes in the received signal power level due to beam misalignment for the transmitting and receiving antenna systems is presented. The quantitative assessment of this issue is presented based on simulation studies carried out for an exemplary propagation scenario. For non-line-of-sight (NLOS) conditions, it is shown that the optimal selection of the transmitting and receiving beam directions may ensure an increase in the level of the received signal by several decibels in relation to the coaxial position of the beams. The developed methodology makes it possible to analyze changes in the radio channel capacity versus the signal-to-noise ratio and distance between the transmitter and receiver at optimal and coaxial orientations of antenna beams for various propagation scenarios, considering NLOS conditions. In the paper, the influence of the directional antenna use and their direction choices on the channel capacity versus SNR and the distance between the transmitter and receiver is shown.

Plasmonic leaky wave antenna based on modulated radius of cylindrical graphene waveguide

In this paper, the concept, analysis, and synthesis of a novel plasmonic leaky wave antenna (LWA) based on the modulated radius of a cylindrical graphene waveguide (CGW) at the terahertz band are presented. Devices based on the planar graphene waveguide (PGW) suffer from high attenuations, which significantly limit the radiation efficiency and beam width of LWAs. It is shown here that the LWA based on CGW compared to PGW can decrease the beam width from 55° to 12° and increase the radiation efficiency from 20% to 50%. A sinusoidally modulated graphene surface is employed to excite the leaky wave antenna. A sinusoidally modulated reactance surface is realized by the modulation of the radius of the cylindrical waveguide. In comparison to other structures, the proposed antenna can be implemented by applying a single voltage to graphene sheets. As a result, the antenna beam direction can be readily changed by varying the applied voltage.

A study of antenna beam direction estimation for dynamic spectrum sharing

A study of antenna beam direction estimation for dynamic spectrum sharing

Oriented beamformig of a multi-mode antenna based on characteristic mode analysis

In this paper, a method is presented for antenna beamforming based on characteristic mode theory. A multi-mode antenna with two elements and four significant orthogonal modes is presented in 5 GHz. Feed positions of the proposed antenna to excite its four characteristic modes are determined; Then with the help of characteristic mode analysis and the reciprocity theorem, amplitude and phase of the excitation coefficients of the proposed antenna are found to change the antenna beam direction in whole azimuth plane. Moreover, changing the weights of the antenna feeds enables elevation beamforming of the proposed antenna.

Adaptive 3D Imaging for Moving Targets Based on a SIMO InISAR Imaging System in 0.2 THz Band

Terahertz (THz) imaging technology has received increased attention in recent years and has been widely applied, whereas the three-dimensional (3D) imaging for moving targets remains to be solved. In this paper, an adaptive 3D imaging scheme is proposed based on a single input and multi-output (SIMO) interferometric inverse synthetic aperture radar (InISAR) imaging system to achieve 3D images of moving targets in THz band. With a specially designed SIMO antenna array, the angular information of the targets can be determined using the phase response difference in different receiving channels, which then enables accurate tracking by adaptively adjusting the antenna beam direction. On the basis of stable tracking, the high-resolution imaging can be achieved. A combined motion compensation method is proposed to produce well-focused and coherent inverse synthetic aperture radar (ISAR) images from different channels, based on which the interferometric imaging is performed, thus forming the 3D imaging results. Lastly, proof-of-principle experiments were performed with a 0.2 THz SIMO imaging system, verifying the effectiveness of the proposed scheme. Non-cooperative moving targets were accurately tracked and the 3D images obtained clearly identify the targets. Moreover, the dynamic imaging results of the moving targets were achieved. The promising results demonstrate the superiority of the proposed scheme over the existing THz imaging systems in realizing 3D imaging for moving targets. The proposed scheme shows great potential in detecting and monitoring moving targets with non-cooperative movement, including unmanned military vehicles and space debris.

Design and simulation analysis of THz wave parabolic antenna with beam deflection

In THz wave detection, such as in the imaging and communication technology applications, it is often necessary to deflect the antenna beam direction to achieve beam steering or antenna orientation characteristics. In this work, the design, fabrication, simulation and analysis of two different kinds of 360 GHz THz wave parabolic antennas is presented. The antenna beam is deflected in a specified direction by using the deflection of the reflector. The directional deflection of the antenna beam is obtained by deflecting the reflector of the antenna. The simulation results and analysis performed in this work provides an insight into the theoretical and practical basis for the future applications of THz wave technology.

A low-delay information sharing algorithm for multiple-radio-per-platform networking

In order to ensure the strong real-time information sharing of Aerial Ad hoc Network, a low-delay information sharing algorithm for multiple-radio-per-platform networking is proposed based on the directional transmission capability of phased-array antenna. The algorithm introduces virtual nodes and virtual links in the process of topology generation first. By extracting topology information and choosing link grouping, it can effectively reduce redundant transmission and transmission latency of information sharing. Then, it is verified through simulation that the algorithm can reduce the latency by up to 49.8% and eliminate transmission redundancy. In addition, a direction selection algorithm is proposed for the variation of antenna beam direction. Simulation results show that the algorithm can further reduce the latency of information sharing and ensure the real time of information sharing, thus further improving the network performance.

A Radiation Pattern Reconfigurable Fabry–Pérot Antenna Based on Liquid Metal

A new beam controllable Fabry–Perot (FP) antenna utilizing a liquid-metal partially reflective surface (PRS) is investigated. The proposed PRS can be divided into three different liquid-metal-filled areas. By injecting the liquid metal into specific zones, the antenna beam direction and 3 dB beamwidth can be controlled separately, providing an easy control method for the radiation pattern reconfigurable FP antenna. The experimental results demonstrate that the proposed antenna works at 5.1 GHz. Five beam directions in the elevation plane ( $\varphi = 90^{\circ }$ ) and four antenna horizontal beam widths can be obtained. The FP antenna is simple in design and is easily fabricated as well. It will be a good candidate antenna for future wireless communication systems.

Retrieval of temperature profiles using radio acoustic sounding system (RASS) with the equatorial atmosphere radar (EAR) in West Sumatra, Indonesia

The radio acoustic sounding system (RASS) with the equatorial atmosphere radar (EAR) at Koto Tabang, Indonesia was adapted to test the effects of the acoustic source location and acoustic frequency range on the continuous measurement of height profiles of temperature in the tropical troposphere. We installed the acoustic transmitting system by using six high-power horn speakers and four subwoofers. We developed a three-dimensional ray-tracing method of acoustic waves to predict the shape of acoustic wavefronts, accounting for the effects of the background winds on acoustic wave propagation. Then, we selected the appropriate antenna beam directions for EAR that satisfy the Bragg condition between the radar and acoustic wave propagation vectors. We carried out eight campaign observations in 2016, testing the performance of EAR–RASS. We found that the location and acoustic frequency range affected the RASS echoes. We also tested the compensation method of the background wind velocity with EAR to obtain the true sound speed. We intensively analyzed the RASS results from August 29 to September 3, 2016, when radiosondes were launched 12 times from the EAR site. We successfully retrieved the temperature profiles from RASS from 2 to 6–14 km with time and height resolutions of about 10 min and 150 m, respectively. Some temperature profiles were obtained up to about the tropopause at 17 km, although the observation period was short. During the RASS campaign, we detected a few interesting events regarding temperature variations as well as large perturbations in the three components of wind velocity.

Beam steering by using a gradient refractive index metamaterial planar lens and a gradient phase metasurface planar lens

AbstractMetamaterials are composed of periodic or quasi‐periodic subwavelength structures, having electric and/or magnetic responses. Metamaterials can arbitrarily tailor the refractive index by artificially tailoring the unit‐cell geometries and dimensions. Recent years, as the two dimensional equivalent of bulk metamaterials, metasurfaces have caused considerable attentions due to the lower profile and simpler to fabricate than bulk metamaterials. Metasurfaces can impart discontinuities on electromagnetic wavefronts and can achieve the arbitrary transmission phase of the whole period range. Metamaterials and metasurfaces have led to the realizations of novel electromagnetic properties and functionalities through tailoring subwavelength structures and integrating functional materials. In this letter, two planar lenses are respectively proposed to control the beam direction of the horn antenna by using a gradient refractive index (GRIN) metamaterial and a gradient phase (GRPH) metasurface. It is shown that the antenna beam direction can be steered by controlling the refractive index of the GRIN metamaterial or the transmission phase of the GRPH metasurface. The differences between the two planar lenses for controlling the antenna beam are illustrated.

5G: MIMO BDMA System Trends and Technology

Beam Division Multipleaccess(BDMA) is The last techniquecame to create the fifth-generation (5G) and solving the problem in the fourth generation (4G). In which base station (BS) allocates private beam to the mobile station (MS) in the system, to increase the capacity and bandwidth of system. For that antenna beam is divides according to the speed and location of mobile stations. In mobile wireless communication the important thing is how to increased limited frequency of the system, improve data rate and good quality of services for user etc. This paper presents information about BDMA and explain the differenttechnologies,and which we want to making future mobile with more powerful and more in demand.Useful thing in BDMA technique is the large number of users to connect at the same time by direction of orthogonal beam from BS by giving multiple access to MS, and increasing the ability of system to be established very big channel. Direction of antenna beam goes off the desired location of MS, and void are placed in undesired direction depend on work environment.

PATL: A RFID Tag Localization based on Phased Array Antenna

In RFID systems, how to detect the position precisely is an important and challenging research topic. In this paper, we propose a range-free 2D tag localization method based on phased array antenna, called PATL. This method takes advantage of the adjustable radiation angle of the phased array antenna to scan the surveillance region in turns. By using the statistics of the tags’ number in different antenna beam directions, a weighting algorithm is used to calculate the position of the tag. This method can be applied to real-time location of multiple targets without usage of any reference tags or additional readers. Additionally, we present an optimized weighting method based on RSSI to increase the locating accuracy. We use a Commercial Off-the-Shelf (COTS) UHF RFID reader which is integrated with a phased array antenna to evaluate our method. The experiment results from an indoor office environment demonstrate the average distance error of PATL is about 21 cm and the optimized approach achieves an accuracy of 13 cm. This novel 2D localization scheme is a simple, yet promising, solution that is especially applicable to the smart shelf visualized management in storage or retail area.

The Research on Phantom-Bit Technology of Digital Phase Shifters for Satellite Tracking System of Phase Array

Phased array satellite platform self-tracking system is for the stability between the missiles and other high-speed movement of the platform and the relay satellite two-way information transmission needs to carry out the self-tracking technology research of onboard platform-dimensional active phased array satellite. The system uses a sub-array correlation method for accurate measurement of the angle of the satellite signal. Receiving array is divided into four 4 * 4 sub-array, each antenna signal combining unit 4 sub array for 4-way A / D to be converted, through down-conversion, filtering, extraction and other processes to get a digital baseband signal, the baseband digital signal processing is to extract the angle error information into digital beam orientation system for tracking filtering operation, thereby ensuring that the transceiver has been aligned with the satellite antenna beam direction. In this paper ,phantom-bit technology for satellite tracking system under the condition of minimum beam displacement is researched for satellite tracking system.

Algorithms of neighbor discovery in wireless networks with directional antennas

To improve the efficiency of neighbor discovery in wireless networks with directional antennas,a busy-tone aided algorithm was proposed.With the help of omni-directional busy-tones,the problems of collision and idleness in wireless communication were effectively resolved;as a result,the channel utilization ratio was increased.The direction of antenna beam was adjusted according to the Direction of Arrival(DOA) of busy-tones.Through this strategy,communication efficiency was improved.The experimental results show that,compared with the conventional ALOHA-like algorithm and the neighbor discovery algorithm based on the feedback mechanism,the proposed algorithm has a better performance.

Self-Consistency of Marine Surface Wind Vectors Observed by ASCAT

Marine surface wind vectors observed by the Advanced Scatterometer on the MetOp-A satellite are evaluated by assessing their self-consistency. Global statistics on wind speeds and directions were calculated from the data for a period of one year. The wind speed histograms exhibited a clear dependence on the cross-track wind vector cell (WVC) location, which corresponds to the incidence angle. This trend was reflected in the higher order statistics (standard deviation, skewness, and kurtosis) of the wind speed distribution. The histograms of the wind directions relative to the satellite flight direction clearly showed systematic errors relative to the antenna beam directions. The number density of the wind directions exhibited a systematic pattern relative to the antenna beam directions, and the pattern varied with wind speed and cross-track WVC location. These systematic errors in the wind speed and direction may affect the divergence/convergence and rotation of the wind field. The results of this study suggest the need for further refinements of the wind retrieval algorithms and the C-band geophysical model function. It was also confirmed that the evaluation technique based on the statistical distributions of scatterometer-derived vector winds is effective for identifying systematic errors in the wind speeds and directions.

TRMM PR Standard Algorithm 2A23 and its Performance on Bright Band Detection

This paper presents the statistical properties of bright band (BB) measured by the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR). Since BB is detected by PR standard version 6 (V6) algorithm 2A23 V6, this paper first outlines 2A23 V6, which classifies rain into three main categories: stratiform, convective, and other. This paper studies BB from the viewpoint of algorithm development. It demonstrates that the detected BB count strongly depends on the antenna scan angle. The BB height (HBB) detected by the PR is compared with the 0°C height computed using the National Centers for Environmental Prediction-Department of Energy Atmospheric Model Intercomparison Project-II reanalysis (NCEP2) data. On average, the BB height is about 500 m below the 0°C height, which is computed from the NCEP2 data. However, a large difference between the above two heights is sometimes observed, mainly due to the false detection of BB. The reliability of BB detection by the current PR algorithm 2A23 V6 could be increased by introducing a simple filter that rejects BBs by regarding them as false when the number of BBs detected in one antenna scan (consisting of 49 antenna beam directions) is less than or equal to 5. An improved version of the filter is planned to be installed in the coming 2A23 V7. Statistics of 10 years of PR data indicate a small but discernible effect of the August 2001 boost of the altitude of the TRMM satellite on the rain type statistics and on the BB statistics. The zonal mean of the maximum value of reflectivity factor in the BB peak (ZmaxBB) over water is almost constant in latitude, but the zonal mean of ZmaxBB over land is less at latitudes above 20 degrees in the northern hemisphere. The width of BB increases as ZmaxBB increases. The zonal mean of the BB width in mid latitude exhibits a small but smooth decrease as the latitude increases.

Development of radio acoustic sounding system (RASS) with Gadanki MST radar – first results

Abstract. A high-power acoustic exciter was designed and developed for the Gadanki MST Radar to facilitate observations in the Radio Acoustic Sounding System (RASS) mode. Sweep range of acoustic signal frequencies was set to 94–125 Hz so as to satisfy Bragg matching condition for temperature range of −90°–40°C between surface and the tropopause (about 17 km). Raytracing of acoustic wave propagation was used to predict the antenna beam directions along which optimum RASS echoes could be obtained. During the RASS observation period of about 18 h on 23–24 July 2006 height profiles of atmospheric virtual temperature were obtained between 1.5 km and 10 km and occasionally up to 14 km. In comparison with the three simultaneous radiosonde launches, RASS derived temperature profiles had the r.m.s. discrepancy of about 1 K, although deviation of the RASS results sometimes appeared when the radial wind velocity was not fully available for the correction of apparent sound speed. This study has successfully demonstrated capability of the RASS application with the Gadanki MST radar, which will be used for continuous monitoring of the temperature profiles in the troposphere and lower stratosphere region in the tropics.