Antenna Rotation Research Articles

Highway Tunnel Defect Detection Based on Mobile GPR Scanning

In order to overcome the difficulty in rapid detection for expressway tunnels, the coherence calculation of dual-frequency radar signal in the time domain is proposed to suppress the interference. A dual-frequency (400 MHz and 900 MHz) GPR and a manipulator are developed. In the horizontal direction, it has a −90°~90° range, a vertical rotation range from 0 to 90°, a length range from 5~9.5 m, and an antenna rotation between −40°~40°. The mobile scanning has been realized in the expressway tunnel, taking the vehicle as the mobile carrier. The research shows that: This equipment realizes the rapid detection of the tunnel without affecting the expressway’s opening. The imaging algorithm recognizes the structural thickness, reinforcement distribution characteristics, and structural diseases. According to the detection carried out in Zhejiang, China, the spacing between reinforcement in the second lining is 4 cm, and the thickness of the structure is about 0.55 m. However, the reinforcement has deformed badly, and the defects are also discerned in the structure. Compared with the traditional handheld radar detection, the equipment dramatically reduces the labor demand, time, and cost and can meet engineering needs. With the proposed method, the detection time is reduced to 12 min/km from 0.5 d/km, and the cost is reduced by more than two times. Furthermore, during the detection, the traffic can be maintained normally.

Ultra-Wideband Imaging via Frequency Diverse Array with Low Sampling Rate

Imaging systems based on millimeter waves (mm-waves) are advancing to achieve higher resolution and wider bandwidth. However, a large bandwidth requires high sample rates, which may limit the development of ultra-wideband imaging systems. In this letter, we introduce the concept of frequency diverse array (FDA) into mm-wave imaging systems. In particular, we propose an ultra-wideband imaging method based on the FDA configuration to reduce sampling rates. In the proposed method, the required sampling rate of an imaging system with N transmit elements is only one-Nth of the conventional systems. Hence, the proposed method can significantly reduce the sampling rate. Unlike compressed-sensing-based sampling methods, the proposed method does not require repeated observations, and is easier to implement. Thanks to the FDA concept, the proposed method can scan the space without phase-shifters or rotation of antennas. We perform matched filtering process in the frequency domain to obtain frequency-delay-dependent vectors. By discretizing the scene, we establish a dictionary covering the imaging scene. Accordingly, a convex optimization problem with measured results and the dictionary based on sparse reconstruction are formulated to realize super-resolution imaging. Compared to conventional methods, the proposed method can distinguish smaller target intervals with low sampling rate in an easy-to-implement way. The proposed method provides a different perspective for the development of ultra-wideband imaging systems.

Towards the optimal orchestration of steerable mmWave backhaul reconfiguration

Future generations of mobile networks will require increased backhaul capacity to connect a massive amount of small cells (SCs) to the network. Since having an optical connection to each SC might be infeasible, mmWave links are an interesting alternative due to their large available bandwidth. An advantage of a wireless backhaul is that the topology can be reconfigured to adapt to changing traffic demands, new operator policies, or to rapidly overcome network failures. In this work, we investigate the problem of orchestrating the reconfiguration of mmWave wireless backhaul networks with mechanically steerable antennas assuming green backhaul operation where nodes are turned off when not in use. The orchestration involves scheduling and coordinating the powering on/off of nodes, the rotation of antennas to achieve alignment for link establishment, and setting up and tearing down links to minimize packet loss during the reconfiguration. We model the problem as a Mixed Integer Linear Program (MILP) for optimal orchestration and propose a sub-optimal reduced MILP for larger instances. Numerical results for different topologies using a realistic traffic trace indicate that optimizing reconfiguration orchestration can significantly reduce packet loss in comparison to a straightforward reconfiguration approach, enabling a smooth transition between target mmWave backhaul topologies.

A Compact Multimode OAM Antenna Using Sequentially Rotated Configuration

For multiplex beams of orbital angular momentum, we propose a two-looped concentric uniform circular array consisting of sequentially rotated circular polarization (CP) triangle patches. Generally speaking, the rotation of the CP antenna makes feeding networks free of narrowband phase shifters. Further investigations also reveal that CP performances of elements and the rotation parameters (including directions and centers) are critical factors. Moreover, adopting the triangle patches makes the array compact and wideband. A demonstration with 12 elements is designed and fabricated, whose radius is only 0.76 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> . Simulations and measurements suggest that it could emit circularly polarized vortex waves of modes −1 and −2 at the X-band simultaneously, and its bandwidth is about 8.7%.

Differences in Spectrum Width Estimates Between Electronic Scans and Mechanical Scans With a Phased Array Weather Radar

This letter presents differences in spectrum width estimates between electronic scans and mechanical scans with a cylindrical polarimetric phased array radar (CPPAR). Theoretical formulation of spectrum width estimates considering the transverse wind, shear, and turbulence within the radar&#x2019;s resolution volume is described. Cross correlation function between two resolution volumes is derived based on wave scattering by randomly distributed scatterers. Spectrum width estimates of ground clutter and weather scatterers with the CPPAR in electronic scans and mechanical scans are presented and compared. It is shown that instead of antenna rotation, the transverse wind, shear, and turbulence within the radar&#x2019;s resolution volume, which were previously ignored for narrow beams, contribute the most to the differences in spectrum width estimates between mechanical scans and electronic scans for the CPPAR with a wide beam.

Low-cost azimuth and elevation antenna rotator for LEO satellite tracking

Connectivity is increasing at a rapid rate these days. Satellites play a key role in communication and are one of the best ways to share information across a wide distance within fraction of seconds. Establishing communication with satellites requires a properly tuned antenna to the satellite’s uplink and positioning of the antenna also plays a key role. Directional antennas are considered to be most suited for this purpose but positioning the antenna is very crucial to obtain an optimum strength of signal reception. Tracking of Low Earth Orbit (LEO) satellites with directional antennas require speed and precision to ensure the required signal strength for further data processing. Low-cost ground stations are economical and save huge space. In the present study, a setup has been proposed consisting of DC motors controlled through Arduino and GY511 compass module to rotate the antenna and track the satellites using a computer. Further, the data received has been post processed to interpret the meaningful weather forecast of the Cyclone Tauktae during the period of May 14 to May 17, 2021.

Preliminary Results of an Astri/UWM EGNSS Receiver Antenna Calibration Facility.

In 2019, the University of Warmia and Mazury in Olsztyn, in cooperation with Astri Polska, started a European Space Agency (ESA) project. The purpose of the project is the development and implementation of a field calibration procedure for a multi-frequency and multi-system global navigation satellite system (GNSS). The methodology and algorithms proposed in the project are inspired by the “Hannover” concept of absolute field receiver antenna calibration; however, some innovations are introduced. In our approach, the antenna rotation point is close to the nominal mean phase center (MPC) of the antenna, although it does not coincide with it. Additionally, a National Marine Electronics Association local time zone (NMEA ZDA) message is used to synchronize the robot with the GNSS time. We also propose some modifications in robot arm movement scenarios. Our first test results demonstrate consistent performance for the calibration strategy and calibration procedure. For the global positioning system (GPS) L1 frequency, the calibration results show good agreement with the IGS-type mean values. For high satellite elevations (20°–90°), the differences do not exceed 1.5 mm. For low elevation angles (0°–20°), the consistency of the results is worse and the differences exceed a 3 mm level in some cases.

Vibration Error Compensation With Helicopter-Borne Rotating Synthetic Aperture Radar

As a new imaging framework, the rotating synthetic aperture radar (ROSAR) derives a synthetic aperture through antenna rotation instead of traditional linear platform motion. The rotational synthetic aperture is sensitive to high-frequency vibrations aboard helicopters. The vibration causes severe phase error in signal echoes and imaging degradation. Unlike traditional synthetic aperture radar (SAR) imaging where range-Doppler algorithm (RDA) maybe applied for autofocus to improve the imaging performance, vibration phase errors cannot be estimated via conventional imaging algorithms due to severe range and azimuth couplings. A new ROSAR imaging procedure is proposed to compensate the phase error resulting from high-frequency vibrations of helicopters. A vibration model of ROSAR signal echo is established. The double Doppler keystone transform (DDKT) is adopted to correct the range cell migration (RCM) induced by slant range history and vibration errors. Analytical echo expression with range-independent vibration phase error is also derived in greater details. The focused image can then be obtained via classical autofocus algorithms. The effectiveness of the proposed technique is sufficiently demonstrated through simulation studies.

A new area-based primary protection method with received power-based 3D antenna rotation range prediction for dynamic spectrum access

A new area-based primary protection method with received power-based 3D antenna rotation range prediction for dynamic spectrum access

A New Primary Protection Method With Received Power-Based 3D Antenna Rotation Range Prediction for Dynamic Spectrum Access

We propose a new primary protection method for Dynamic Spectrum Access (DSA), in which a secondary system uses a frequency band assigned to a primary system. Following a DSA implementation plan in Japan, we take care of a practical scenario where a primary system's transmission station (PTS) moves along a predefined course or area, and a corresponding primary reception station (PRS) keeps its antenna boresight facing towards the moving PTS. For accurate interference calculation from the secondary to the primary systems in this scenario, the proposed method takes the movement of the PTS into account and predicts a range of angle variation of the PRS's antenna boresight based on received signal powers from the PTS to the PRS. We conducted computer simulations in three different practical scenarios to demonstrate the effectiveness of the proposed method. The simulation results show that the proposed method can increase the number of available secondary base stations (SBSs) by up to 1.93 times compared to a conventional method.

Measurement of frequency characteristics of disturbance torque in the process of satellite antenna rotation

As an important equipment for satellite signal reception and transmission, the satellite antenna needs to be rotated in real time to achieve real-time tracking of the target and complete signal transmission during applications. Antenna driving mechanism is generally composed of motor and other components, which will cause some structural vibration during rotation. For high-stability satellite applications, the vibration disturbance torque is a major factor affecting the satellite stability. In order to study characteristics of the disturbance torque, the disturbance data from the antenna under different rotation conditions should be measured. In this paper, the frequency characteristics of disturbance torque of a rotating satellite antenna using stepper motor as driving motor is tested and discussed.

Спосіб розпізнавання типів трьохкоординатних радіолокаційних станцій оглядового типу засобами повітряної радіотехнічної розвідки

Розглядаються способи розпізнавання типів оглядових радіолокаційних станцій в станціях повітряної радіотехнічної розвідки на основі використання апріорних відомостей про параметри огляду простору радіолокаційних станцій. Розпізнавання базується на аналізі виміряних первинних параметрів зондуючих сигналів, а саме періодичних моментів опромінення станції радіотехнічної розвідки, діапазону робочих частот, тривалості зондуючих імпульсів та ін. Аналізуючи ці параметри, можливо однозначно визначити тип джерела випромінювання. Розглядається теоретичні аспекти алгоритму розпізнавання, що засновано на перекритті густин розподілу параметрів відношення правдоподібності.

Mathematical modelling of the spatial excitation system of a cylindrical active phased antenna array with electronic commutation

This article discusses the excitation system of a cylindrical active phased antenna array with a spatial power supply system for the emitters. A brief historical comparison of the presented system with those based on the use of mechanical antenna rotation and a conformal phased antenna array with a matrix excitation system was performed. The advantages of an active phased antenna array with a spatial excitation system, its operational principles and the results of mathematical modelling are presented.

Ultrasonic tomograph for reconstruction of spatial distributions of sound speed and absorption coefficient

Ultrasound tomograph designed to reconstruct spatial distributions of sound speed and absorption coefficient in soft biological tissues (primarily in mammary gland) is presented. Distinctive feature of the tomograph is sparse annular antenna array with irregular arrangement of receiving-transmitting transducers. When an object is tomographed by its layers, 26 transducers in combination with antenna rotation allow providing the same data set as in case of nonrotating array with 256 transducers. Two-step processing algorithm uses both ray methods to reconstruct large-scale details of the required spatial distributions and wave methods to reconstruct small details. High degree of algorithm parallelism allows to reduce the time of experimental data processing by CUDA GPUs to several minutes per an image layer. Results of processing both model data and experimental data obtained for phantom objects are presented. Disadvantages of reconstruction at the first step of the algorithm with low resolution (0.5–1 cm) are analyzed. The high resolution (not worse than 1 mm), achieved at the second step of reconstructing the small details is illustrated. It is shown that these small details, which are the most informative for medical diagnostics at early stage of neoplasm, cannot be reconstructed without preliminary reconstruction of large-scale details.

Calibration of a Polarimetric MIMO Array With Horn Elements for Near-Field Measurement

Polarimetric multiple input and multiple output (MIMO) radar is capable of acquiring target’s high-resolution images and polarization scattering matrix (PSM). In this article, calibration of a polarimetric MIMO array of an instrumentation radar for near-field measurement is achieved at ${X}$ -band by using a rotatable double-antenna polarimetric active radar calibrator (RODAPARC) and a metal cylinder quickly and accurately. The theoretical PSM of the RODAPARC with different antenna rotation angles is derived from Huygens’ radiation electric field which is applicable to different bistatic angles. A polarimetric signal model is adopted to reduce the impact of the RODAPARC on calibration. Experimental studies are conducted on a polarimetric MIMO array which is measured and divided into quasi-monostatic and bistatic transceiver channels for assessment on the calibration performance. Promising calibration results are obtained with a polarization isolation improvement of about 16 dB and great reduction of the polarization channel gain error less than ±0.5 dB in amplitude and ±3° in phase. The calibrated polarization signatures for classic objects are consistent with the theoretical results.

Numerical Simulation of 2-D Underground Magnetic Resonance Tomography by Using Rotating Antenna and Sector Scanning

Magnetic resonance sounding (MRS) has been applied to underground constructions, such as tunnels and mines, to detect and forewarn groundwater sources hidden in front of the mine face, also named disaster water sources. Disaster water sources are mostly found in 2-D or 3-D structures; as such, their spatial distribution characteristics are difficult to reflect accurately by conventional 1-D MRS results. This letter proposes a method for sector-scanning magnetic resonance tomography (MRT) measurement using rotating antennas for 2-D water-bearing structures, such as water-filling conduits, faults, and goafs to obtain the 2-D distribution image of water content and relaxation time ( $T_{2}^{*}$ ) in front of the face by inversion. Through the numerical simulation of conduits, we analyzed the 2-D sensitivity, resolution, and inversion results of the rotating antennas. The imaging result at a high noise level was improved by increasing the number of antenna rotations. We also determined the effects of 2-D MRT on the faults and goafs and discussed the minimum cross-sectional area and maximum distance for reliable imaging of conduits.

User Influence on Polarization Characteristics in Off-Body Channels

This article investigates the impact of the user's body on wearable antenna radiation characteristics and the consequent effects on the off-body channel, with the focus on the polarization aspect. The impact on antenna gain and polarization is analyzed for different antenna placements and separations from the body, based on electromagnetic simulations with numerical phantoms at 3, 4 and 5 GHz. Results show a strong influence of the body on the antenna efficiency, gain, and polarization. The excess losses due to body-shadowing suppress the antenna radiation behind the body by more than 20 dB, while its polarization changes from vertical in free space, to an elliptical one when placed on the body. The obtained radiation characteristics are then employed for off-body channel simulations using a geometry-based polarized channel model, which employs an analytic mobility model for wearable antennas based on Fourier series. The antenna rotation due to changes in user's posture is seen as one of the main sources of off-body channel degradation. The polarization mismatch losses imposed by antennas' physical misalignment, are observed to yield periodic fades of the Line-of-Sight component, with more than 30 dB drops in the received power level.

Correction of Channel Sounding Clock Drift and Antenna Rotation Effects for mmWave Angular Profile Measurements

Proper characterization of the millimeter-wave (mmWave) propagation channel requires measuring the power angular-delay profile of the channel which includes angle-of-departure and angle-of-arrival of the multipath components (MPCs). In this paper, we first describe in detail our rotating directional antennas-based 28 GHz channel sounder. Then, for this specific sounder class, we describe and address the following two problems in extracting the MPCs from the measurements: 1) For long-distance channel measurements, triggering signal cannot be generated for the TX and the RX using a single clock (SICL). This necessitates the use of separate clocks (SECLs) which introduces a random timing drift between the clocks. 2) As positions of the antennas change during scanning, total distance traveled by the same MPC differs at each measurement. These problems together cause missing some of the MPCs and detecting MPCs that do not exist in reality. We propose an algorithm to correct the clock drift and MPC delay errors due to the rotation of the antennas. We compare the MPCs from the SICL measurement and the corrected SECL measurements using a Hungarian algorithm based MPC matching method. We show that the percentage of the matched MPCs increases from 28.36% to 74.13% after the correction process.

ЧИСЛОВИЙ МЕТОД ВИЗНАЧЕННЯ ЕЛЕКТРОМАГНІТНОГО ПОЛЯ В ОБЛАСТІ ФОКУСА ПАРАБОЛОЇДА ОБЕРТАННЯ ДЗЕРКАЛЬНОЇ АНТЕННОЇ СИСТЕМИ

When analyzing antennas, and especially when developing new ones, including mirrors, there is a problem of calculating their basic parameters. For this purpose it is necessary to study the electromagnetic field excited in the focus region of the paraboloid of rotation, which is irradiated by the horn irradiator. At present, such calculations are made using modern computer simulation software. They are based on common numerical methods for solving Maxwell's equations and are presented as a finished product without disclosing internal content. So, estimating the error of calculations with the help of such programs is almost impossible. Due to the mathematical complexity of even the simplest scattering and diffraction problems, it is rarely possible to obtain closed-form solutions that are convenient for the direct calculation of virtually useful physical characteristics. Thus it is necessary to allow a certain degree of approximation when forming boundary conditions, solving equations, or at all stages. The previously obtained calculation algorithms have the disadvantage that they can be implemented only by numerical methods, since the integrals obtained are not tabular and cannot be reduced to such. There is a need to simplify the expressions for the field scattered by the horn by approximating and obtaining simple formulas. The paper proposes to determine the electromagnetic field in the focus area of the paraboloid of the rotation of the mirror antenna and on the axis of the mirror by solving the integral equations by a numerical method with the normal polarization of the incident wave. The novelty is the use of a new numerical method for determining the scattered electromagnetic field, irradiated by a horn irradiator, which is located in the focus of the antenna system's rotational paraboloid in order to improve the tactical and technical characteristics of the radio stations at which they are installed. Finite expressions, albeit approximate ones, are obtained, from which the physics of the phenomenon of re-reflection is understood.

A Channel Model for Polarized Off-Body Communications With Dynamic Users

This paper presents an off-body channel model for polarized communications with dynamic users. The model is based on Geometrical Optics and Uniform Theory of Diffraction and accounts for free space propagation, reflections, and diffractions. It allows for arbitrary antennas’ polarizations and gain patterns and supports a number of on-body antenna placements. In order to take the influence of users’ motion into account, a mobility model for wearable antennas on dynamic users is used. Signal depolarization mechanisms are identified, and simulations are performed to analyze the influence of user dynamics on the channel. The results show that significant polarization mismatch losses occur due to wearable antenna rotations, resulting in received power variations up to 37.5 dB for the line-of-sight component and 41.4 dB for the scattered one. The importance of taking signal polarization into account is demonstrated by comparing the simulation results between polarized and nonpolarized channel models in a free space propagation scenario, where a difference up to 53 dB in between the two is observed.