Antenna Beam Research Articles

An All-Metal, Circularly Polarized Reflectarray Antenna for High-Power Microwave Applications

In order to improve the performance of the existing high-power microwave (HPM) antenna, an all-metal circularly polarized (CP) reflectarray (RA) antenna is proposed in this article. The proposed antenna has 2-D beam-steerable capability up to 60° elevation angle. The RA element employs an H-shaped slot and can be mechanically rotated to obtain continuous 360° phase coverage with negligible element loss. By rotating the individual element, the RA antenna can achieve the dynamical control of the antenna beam. The maximum antenna gain is 33.05 dBi, corresponding to an aperture efficiency of 58.76%. In addition, the simulation results show that the power handling capacity of the RA antenna is over 5 GW/m2 under vacuum condition, which can be applied to the HPM applications.

Directional link attenuation in millimeter-wave range based on empirical model modification

The upcoming fifth and next generation mobile phone systems will use not only the frequencybands of sub-6 GHz but also the millimeter-wave and terahertz bands. From a practical viewpoint,this approach requires the use of directional antennas or beamforming systems. To ensure greaterenergy efficiency of the wireless link, the radio beams on the transmitting and receiving sides shouldbe aligned ones. Path loss models are commonly used for designing the radio communication systemsand networks. However, in the literature, there are no adequate methods of attenuation modellingavailable for the cases of misalignment of antenna beams. In this paper, a method of modifying the pathloss model, based on a multi-elliptical propagation model, is proposed. For this purpose, dedicatedsoftware was developed in the MATLAB environment, which was used to conduct simulation tests.In the remainder of the paper, exemplary results of the adaptation of empirical path loss models inthe range of millime-ter-waves are presented, which were obtained using the developed program.Keywords: wireless communication, radio wave propagation, path loss models, multi-ellipticalpropagation model, directional antennas, directional radio link, millimeter waves, 5G systems,simulation studies

SAR Antenna Pattern Measurement by Internal Calibration Method for GF-3 Satellite

GF-3 is the first C-band multipolarization synthetic aperture radar (SAR) satellite in China. The SAR system is equipped with an active phased array antenna to electronically generate various antenna beams. The accuracy of SAR antenna patterns is of main importance for precise SAR image processing. The traditional method for antenna pattern measurement is the near-field method but it is unable to satisfy the demand for fast measuring in-orbit. In order to measure the SAR antenna pattern quickly with high accuracy, we propose the internal calibration method. The internal calibration uses calibration signals which are routed along the nominal signal path in SAR systems, thus monitoring the gain and phase variations for each T/R channel is possible. This paper will focus on this method, including its principle, operation steps, and results, compared to the near-field method. The internal calibration method provides a valuable solution for SAR antenna pattern measurement.

A constant phase stable over the wideband for beam steering antenna applications

A K-band wideband self-compensating phase shifter based on gap waveguide is presented. The traditional waveguide phase shifter cannot easily achieve a stable phase shift over wideband due to the dispersion effect. Accordingly, a short-circuit structure and a slow-wave structure are designed in this paper, and their phase shifts show a positive-slope and a reverse-slope with respect to frequency. The two structures are realized using the tuning screw technology, and different phase shifts of 0–140° are realized by adjusting the number of screws. Besides, two structures are combined with a high-isolation power divider to realize a phase shifter with high phase and amplitude stability. The phase shifter is manufactured and measurement results of the eight phase shifts of the phase shifter show that the bandwidth of the phase changes within ±5° was greater than 30%. Finally, a four-way feeding network has been designed, which is used to form a four-element linear array. Generally, when the antenna beam is steered, the main-beam directions of different frequencies are not consistent. Therefore, by compensating the slope of the phase shifter with respect to the frequency, an array antenna whose main-beam direction does not change with respect to frequency is designed.

Non-Ionizing Radiation Measurements for Trajectography Radars.

This work presents a Non-Ionizing Radiation (NIR) measurement campaign and proposes a specific measurement method for trajectography radars. This kind of radar has a high gain narrow beam antenna and emits a high power signal. Power density measurements from a C-band trajectography radar are carried out using bench equipment and a directional receiving antenna, instead of the commonly used isotropic probe. The measured power density levels are assessed for compliance test via comparison with the occupational and general public exposure limit levels of both the International Commission on Non-Ionizing Radiation Protection (ICNIRP) and the Brazilian National Telecommunication Agency (Anatel). The limit for the occupational public is respected everywhere, evidencing the safe operation of the studied radar. However, the limit for the general public is exceeded at a point next to the radar’s antenna, showing that preventive measures are needed.

Effects of Receiver Beamforming for Vital Sign Measurements Using FMCW Radar at Various Distances and Angles.

Short-range millimeter wave radar sensors provide a reliable, continuous and non-contact solution for vital sign extraction. Off-The-Shelf (OTS) radars often have a directional antenna (beam) pattern. The transmitted wave has a conical main lobe, and power of the received target echoes deteriorate as we move away from the center point of the lobe. While measuring vital signs, the human subject is often located at the center of the antenna lobe. Since beamforming can increase signal quality at the side (azimuth) angles, this paper aims to provide an experimental comparison of vital sign extraction with and without beamforming. The experimental confirmation that beamforming can decrease the error in the vital sign extraction through radar has so far not been performed by researchers. A simple, yet effective receiver beamformer was designed and a concurrent measurement with and without beamforming was made for the comparative analysis. Measurements were made at three different distances and five different arrival angles, and the preliminary results suggest that as the observation angle increases, the effectiveness of beamforming increases. At an extreme angle of 40 degrees, the beamforming showed above 20% improvement in heart rate estimation. Heart rate measurement error was reduced significantly in comparison with the breathing rate.

On the Functionality of Radar and Laser Ocean Wave Sensors

Ocean wave design criteria are required for the design of offshore platforms and floating systems, which are derived using in situ measurements. However, there is uncertainty regarding the performance of the instruments used for the in situ measurements. The main instruments used by the offshore industry are the Datawell Directional Waverider buoy and Rosemount WaveRadar, with Laser instruments also having been used for specific studies. Recent reports indicate measurements from these three instruments differ in the order of 10% but given the quite disparate nature of the measurements made by these instruments, it is far from clear what the source of this difference is. This paper investigates the wave measurement principles of Radar and Laser instruments using linear wave field simulations to better understand how the instruments perform. The Radar and Laser simulations include modeling electromagnetic signal beam reflections from water surfaces of an area equal to their footprint sizes, considering their beam characteristics and antenna pattern. The study confirms that the Radar underestimates spectral levels at frequencies above 0.5 Hz due to its significantly larger footprint at the water sea surface compared to the Laser (5.25 m vs. 0.15 m). The Laser performs well for almost the entire frequency range for all the cases considered.

Assessment of SAR in Road-Users from 5G-V2X Vehicular Connectivity Based on Computational Simulations.

(1) Background: Cooperative Intelligent Transportation Systems (C-ITS) will soon operate using 5G New-Radio (NR) wireless communication, overcoming the limitations of the current V2X (Vehicle-to-Everything) wireless communication technologies and increasing road-safety and driving efficiency. These innovations will also change the RF exposure levels of pedestrians and road-users in general. These people, in fact, will be exposed to additional RF sources coming from nearby cars and from the infrastructure. Therefore, an exposure assessment of people in the proximity of a connected car is necessary and urgent. (2) Methods: Two array antennas for 5G-V2X communication at 3.5 GHz were modelled and mounted on a realistic 3D car model for evaluating the exposure levels of a human model representing people on the road near the car. Computational simulations were conducted using the FDTD solver implemented in the Sim4Life platform; different positions and orientations between the car and the human model were assessed. The analyzed quantities were the Specific Absorption Rate on the whole body (SARwb), averaged over 10 g (SAR10g) in specific tissues, as indicated in the ICNIRP guidelines. (3) Results: the data showed that the highest exposure levels were obtained mostly in the head area of the human model, with the highest peak obtained in the configuration where the main beam of the 5G-V2X antennas was more direct towards the human model. Moreover, in all configurations, the dose absorbed by a pedestrian was well below the ICNIRP guidelines to avoid harmful effects. (4) Conclusions: This work is the first study on human exposure assessment in a 5G-V2X scenario, and it expands the knowledge about the exposure levels for the forthcoming use of 5G in connected vehicles.

Research on Mono-Pulse Beam Angle Tracking Algorithm of Phased Array Antenna Based on CKF

Phased array antenna beam tracking and communication system based on mono-pulse system is an alternative satellite-to-earth communication technology solution for future planetary spacecraft, which meets the mission requirements of agile scanning, multimode, wide field of view, and small size. This paper firstly outlines the technical scheme of mono-pulse angle tracking based on the planar phased array antenna. A simplified mathematical model of angle measurement is summarized. Secondly, the beam pointing of the spacecraft communication antenna is frequently affected by the attitude and presents a nonlinear dynamic change. A robust two-dimensional angular tracking filtering algorithm based on cubature Kalman filter (CKF) is proposed, in order to solve this complex high-order nonlinear dynamic estimation problem. Finally, the comprehensive performance of the proposed algorithm is simulated and analyzed under two conditions of stable flight and high dynamic flight of the spacecraft. When the angular velocity is within 4°/s, the tracking accuracy can be better than 0.65°, and the tracking accuracy will be better than 1° when the angular velocity is within 8°/s. Compared with the basic CKF algorithm, the robust CKF tracking accuracy is significantly improved, while the resource consumption is slightly reduced. The research results can provide reference for the engineering implementation of related fields in the future.

Smart Antennas for Various Applications

The paper presents about smart antennas for advancement in wireless and mobile communication. Smart antennas also called adaptive array antennas with better signal processing & can be used to calculate beam forming vectors which helps in tracking & locating antenna beam of target. Smart antennas are helpful in health monitoring in covid-19 pandemic and provides better service quality. Smart antenna is one of the rising innovations which can satisfy the prerequisites. Smart antennas are being used for controlling, monitoring and analyzing real time systems for various applications In smart antennas spatial division of the signal is used as compared to spectrum division, it can be beneficial for improving the performance of wireless communication. This paper describes how switched beam & adaptive array antennas differ from basic antennas.

Static and Reconfigurable Huygens’ Metasurfaces: Use in Antenna Beamforming and Beam Steering

In this article, we review recent advances in static and reconfigurable Huygens’ metasurfaces (HMSs) for antenna beamforming and beam steering. First, the fundamental theory of HMSs is summarized along with basic approaches for their physical realization. Subsequently, precise antenna beamforming without feeding networks by utilizing static HMSs is described. This is followed by the description of using HMSs as radomes for extending the scan range of phased arrays. Finally, several strategies are described for realizing reconfigurable HMS by means of electronic control devices.

A Conical Beam Antenna Using a Monopole Wire and Rectangular Copper Probe with Four Parasitic Sleeves for UMTS/WLAN Applications

This paper aimed to present a wideband monopole antenna for base station applications of indoor reception for UMTS (B1) and WLAN (IEEE 802.11b) systems. The operating frequency was ranged from 1.92 GHz to 2.5 GHz. The proposed antenna was made up of a probe and four connecting parasitic sleeves from the upper copper circular patch to the ground. The rectangular probe structure technique was used to extend the frequency band and effectively improve the matching conditions. The results from simulation and measurement showed that the presented antenna had a proper matching impedance of |S11| (dB) lower than -10 dB in the frequency band from 1.71 GHz to 3.72 GHz and also from 1.58 GHz to 2.98 GHz, respectively. The percentage of bandwidth was 74.03% and 61.40%, respectively. The antenna had a conical radiation pattern. The simulated and measured gains were 2.93 dBi to 3.6 dBi and 2.58 dBi to 3.54 dBi, respectively.

High-resolution subglacial topography around Dome Fuji, Antarctica, based on ground-based radar surveys over 30 years

Abstract. The retrieval of continuous ice core records of more than 1 Myr is an important challenge in palaeo-climatology. For identifying suitable sites for drilling such ice, knowledge of the subglacial topography and englacial layering is crucial. For this purpose, extensive ground-based ice radar surveys were carried out over Dome Fuji in the East Antarctic plateau during the 2017/18 and 2018/19 austral summers by the Japanese Antarctic Research Expedition, on the basis of ground-based radar surveys conducted over the previous ∼ 30 years. High-gain Yagi antennae were used to improve the antenna beam directivity, thereby significantly decreasing hyperbolic features of unfocused along-track diffraction hyperbolae in the echoes from mountainous ice–bedrock interfaces. We combined the new ice thickness data with the previous ground-based data, recorded since the 1980s, to generate an accurate high-spatial-resolution (up to 0.5 km between survey lines) ice thickness map. This map revealed a complex landscape composed of networks of subglacial valleys and highlands. Based on the new map, we examined the roughness of the ice–bed interface, the bed surface slope, the driving stress of ice and the subglacial hydrological condition. These new products and analyses set substantial constraints on identifying possible locations for new drilling. In addition, our map was compared with a few bed maps compiled by earlier independent efforts based on airborne radar data to examine the difference in features between datasets. Our analysis suggests that widely available bed topography products should be validated with in situ observations where possible.

A model predictive control for attitude stabilization and spin control of a spacecraft with a flexible rotating payload

Many Earth Observation missions, implementing space-based microwave sensing techniques for collecting surface information, employ spinning sensors to cover large swaths of terrestrial areas, thus improving the rate at which global maps of those measured data are generated. These spacecraft (as Soil Moisture Active Passive (SMAP) developed by NASA or Copernicus Imaging Microwave Radiometer (CIMR) currently under development by Thales Alenia Space) consist of a main non-spun platform and a rotating part composed of an antenna boom, a deployable reflector and a rotation mechanism. As the reflector is designated to rotate about the nadir axis producing conically scanned antenna beams with precise surface incidence angle, the payload pointing accuracy needs to be addressed at both spin subsystem and platform level. In this work, a representative model of the dynamic behaviour of SMAP satellite is developed as a study case to design the proposed control strategies; in particular, a SMAP-like payload structural model is built using FEM commercial codes. The spacecraft is equipped with a Reaction Wheels Assembly (RWA) to accomplish both momentum compensation for the spun element and three-axis attitude control and a motor for the spin mechanism. The objective of the study is to develop the spacecraft control architecture in the frame of Model Predictive Control (MPC) theory. MPC refers to a class of algorithms in which the control action is obtained by computing an open-loop optimal sequence of control moves over a predefined time horizon; moreover, the ability to set constraints on process inputs and outputs directly in the problem formulation allows to account for actuators’ limits. In the study two operative phases of the satellite are addressed: the Spin-up, in which the 6-meter diameter antenna is spun-up to the operative condition of 14.6 RPM, and the Science Phase, in which precise nadir pointing and stability of the flexible system must be kept for acquiring high-resolution measurements. To this purpose, control–structure interaction between attitude/spin control system and flexible dynamics, as well as system’s imbalances, are carefully addressed by the proposed control architecture. The nonlinear in-orbit dynamics of the flexible spacecraft is then used to evaluate the performance of the MPC controller in terms of pointing accuracy and robustness to uncertainties.

Super Directional Antenna—3D Phased Array Antenna Based on Directional Elements

This paper describes an antenna design approach for achieving super directivity in an AESA (Active Electronic Scanned Array) radar using an unconventional 3D phased array (PA) antenna concept based on directional Yagi–Uda elements. The proposed scheme is shown to have a wider scanning feature, with higher directivity in comparison to the same geometry dipole array without increasing the element number. The antenna’s microwave design includes an antipodal Yagi–Uda antenna element that is implemented efficiently on a microstrip PCB using a balun (balance–unbalance)-fed network. This type of antenna is valuable in restricted aperture scans for achieving a narrow antenna beam that increases the angular resolution and measurement precision of tracked targets and also enlarges the detection range or, alternatively, achieves the same performance with a lower number of elements—meeting the goal of low-cost production. The notable result of the high antenna directivity was obtained by both the element and the array architecture, which allowed for improvements in the Array Factor (AF) directivity by increasing the element’s spacing and broadening the scan sector, achieved via the suppression of the element’s Grating Lobe (GL). Another important benefit of this antenna design is the superior coupling reduction caused by its enlarged element distances, which are very significant in electronic scans. An outstanding opportunity to exploit this low coupling can be found in separated MIMO radar architecture. Other benefits of this design’s architecture are the support of a combined module and antenna on a unified board thanks to the End-Fire radiation pattern, its low frequency sensitivity, and its low-cost manufacturing.

Bayesian data analysis for sky-averaged 21-cm experiments in the presence of ionospheric effects

ABSTRACT The ionosphere introduces chromatic distortions on low frequency radio waves, and thus poses a hurdle for 21-cm cosmology. In this paper, we introduce time-varying chromatic ionospheric effects on simulated antenna temperature data of a global 21-cm data analysis pipeline, and try to detect the injected global signal. We demonstrate that given turbulent ionospheric conditions, more than 5 per cent error in our knowledge of the ionospheric parameters could lead to comparatively low evidence and high root-mean-square error (RMSE), suggesting a false or null detection. When using a constant antenna beam for cases that include data at different times, the significance of the detection lowers as the number of time samples increases. It is also shown that for observations that include data at different times, readjusting beam configurations according to the time-varying ionospheric conditions should greatly improve the significance of a detection, yielding higher evidences and lower RMSE, and that it is a necessary procedure for a successful detection when the ionospheric conditions are not ideal.

Sporadic micro-meteoroid source radiant distribution inferred from the Arecibo 430 MHz radar observations

ABSTRACT This work presents the result of sporadic meteor radiant density distribution using the Arecibo 430 MHz incoherent scatter radar (ISR) located in Puerto Rico for the first time. Although numerous meteor studies have been carried out using the Arecibo ISR, meteoroid radiant density distribution has remained a mystery as the Arecibo radar cannot measure vector velocity. A numerical orbital simulation algorithm using dynamic programming and stochastic gradient descent is designed to solve the sporadic meteoroid radiant density and the corresponding speed distributions of the meteors observed at Arecibo. The data set for the algorithm comprises over 250 000 meteors from Arecibo observations between 2009 and 2017. Five of the six recognized sporadic meteor sources can be identified from our result. There is no clearly identifiable South Apex source. Instead, there is a broad distribution between +/−30° ecliptic latitude, with the peak density located in the North Apex direction. Our results also indicate that the Arecibo radar is not sensitive to meteors travelling straight into or perpendicular to the antenna beam but is most sensitive to meteors with an arrival angle between 30° and 60°. Our analysis indicates that about 75 per cent of meteoroids observed by the Arecibo radar travel in prograde orbits when the impact probability is considered. Most of the retrograde meteoroids travel in inclined low-eccentricity orbits.

Antenna beam characterization for the global 21-cm experiment LEDA and its impact on signal model parameter reconstruction

ABSTRACT Cosmic dawn, the onset of star formation in the early universe, can in principle be studied via the 21-cm transition of neutral hydrogen, for which a sky-averaged absorption signal, redshifted to MHz frequencies, is predicted to be O(10–100) mK. Detection requires separation of the 21-cm signal from bright chromatic foreground emission due to Galactic structure, and the characterization of how it couples to instrumental response. In this work, we present characterization of antenna gain patterns for the Large-aperture Experiment to detect the Dark Ages (LEDA) via simulations, assessing the effects of the antenna ground-plane geometries used, and measured soil properties. We then investigate the impact of beam pattern uncertainties on the reconstruction of a Gaussian absorption feature. Assuming the pattern is known and correcting for the chromaticity of the instrument, the foregrounds can be modelled with a log-polynomial, and the 21-cm signal identified with high accuracy. However, uncertainties on the soil properties lead to percentage changes in the chromaticity that can bias the signal recovery. The bias can be up to a factor of two in amplitude and up to few per cent in the frequency location. These effects do not appear to be mitigated by larger ground planes, conversely gain patterns with larger ground planes exhibit more complex frequency structure, significantly compromising the parameter reconstruction. Our results, consistent with findings from other antenna design studies, emphasize the importance of chromatic response and suggest caution in assuming log-polynomial foreground models in global signal experiments.

Sing-Ant: RFID Indoor Positioning System Using Single Antenna with Multiple Beams Based on LANDMARC Algorithm

RFID localization methods have been widely used in indoor positioning systems (IPS). Most localization techniques involve the use of multiple antennas and the placement of antennas and readers in order to ensure accurate positioning results. However, most localization techniques are complex and require high overhead costs in terms of needing multiple antennas and RFID readers. In this paper, we proposed a method to use a single antenna to perform all the reads and rely rather on the antenna beams to acquire multiple positioning data. A single array of antennas is configured to have multiple angles of operation and rely on different power levels as compared to regular antennas. By manipulating the beam pattern, direction and power, multiple sub-antennas can be conceived and the method utilizes antenna beams and relies mainly on one antenna to realize two-dimensional localization.

5G array antenna substrate for electromagnetic beam splitting via cobalt-substituted zinc molybdate low temperature co-fired ceramics

A novel Zn1-xCoxMoO4 (ZCMO) (x = 0.03) ceramic with low-dielectric constant, low-loss, and low-sintering temperature for 5G electromagnetic beam splitting is developed by solid-state reaction method. This ceramic exhibits excellent microwave dielectric properties with εr = 8.0, Q × f = 57682 GHz, τf = − 54.9 ppm/°C at a sintering temperature of 825 °C. An array antenna for electromagnetic beam splitting at 5.4 GHz is designed by using this ceramic for the first time. The highest efficiency and the best electromagnetic beam splitting effect can be jointly controlled by the dielectric constant and dielectric loss of the ceramic. The normalized reflection amplitude of each array unit cell is above 98 %, and the reflection phase covers 360°. The function of electromagnetic beam splitting is verified by the far-field pattern of the electric field. This work helps to promote the development of LTCC and broaden the application scope of microwave dielectric ceramics.