Narrow-beam Antennas Research Articles

Waveform of the Reflected Impulse at the Oblique Sounding of the Sea Surface

The height of sea waves is one of the most important characteristics describing the wave climate of the ocean. At the present, the main radar for remote measurement of wave heights is an altimeter. Measurements are performed at the vertical sounding (incidence angle equal to zero). The Brown model was developed to describe the waveform of the reflected impulse at the vertical sounding. There is no theoretical model for the case of oblique sounding. In the Kirchhoff approximation, the theoretical task about waveform of the reflected impulse at oblique sounding was considered. In the result of the investigation, the analytical formula for the waveform of the reflected impulse for oblique sounding at the small incidence angles (< 12◦) for a microwave radar with a narrow antenna beam was obtained. The waveform of the reflected impulse depends on the width of antenna beam, incidence angle, impulse duration, significant wave height (SWH), altitude of the radar, mean square slopes of large-scale, in comparison with radar wavelength, sea waves. It is shown that possibility exist to retrieve SWH using waveform the reflected impulse at the oblique sounding.

Waveform of the Reflected Impulse at the Oblique Sounding of the Sea Surface

The height of sea waves is one of the most important characteristics describing the wave climate of the ocean. At the present, the main radar for remote measurement of wave heights is an altimeter. Measurements are performed at the vertical sounding (incidence angle equal to zero). The Brown model was developed to describe the waveform of the reflected impulse at the vertical sounding. There is no theoretical model for the case of oblique sounding. In the Kirchhoff approximation, the theoretical task about waveform of the reflected impulse at oblique sounding was considered. In the result of the investigation, the analytical formula for the waveform of the reflected impulse for oblique sounding at the small incidence angles (< 12◦) for a microwave radar with a narrow antenna beam was obtained. The waveform of the reflected impulse depends on the width of antenna beam, incidence angle, impulse duration, significant wave height (SWH), altitude of the radar, mean square slopes of large-scale, in comparison with radar wavelength, sea waves. It is shown that possibility exist to retrieve SWH using waveform the reflected impulse at the oblique sounding.

The wireless communications systems in subterahertz frequency range

Background. The subterahertz and terahertz frequency ranges are very promising for development of high speed wireless communications systems because of possibility to get the bandwidth about some tens of GHz, which provides the high channel capacity. However fast signal attenuation at its propagation in atmosphere complicate the operation of communications systems in these ranges.
 Aim. Use of fixed narrow-beam antennas with high antenna power gain allows to provide the direct surface communications distance to some kilometers. The communications distance limitation can be partially removed decreasing the frequency down to 200 GHz and narrowing the channel bandwidth down to some GHz.
 Methods.The model of transmitter-receiver system (200-220 GHz) based of modern semiconductor devices is described in the manuscript. Results. The possibility of digital signals transmission with speed up to 1 Gbit/s at the distance of 1 km is experimentally shown.
 Conclusion. According to calculations the output power of transmitter about some hundreds mW is enough for data transmission at the distance up to 1.5 km with antenna power gain of no less than 50 dB.

A fast simulation method of ground clutter for airborne wideband radar based on measured SAR image

Ground clutter simulation is a key factor in the design and development of air-to-ground wideband radar. In this paper, the ground clutter simulation technology of stepped frequency airborne wideband radar is studied, and a fast simulation method of ground clutter based on SAR image is proposed. Firstly, the segmented area of high-resolution SAR image according to the radar illumination region is used as the input of the ground scattering coefficient to improve the fidelity of clutter simulation. Then, the antenna pattern is constructed by the uniform plane phased array, by which the power gain of the clutter point is modulated. Thirdly, the clutter echo of stepped-frequency radar is calculated according to the equidistant circle principle which improves the efficiency of computation. Finally, the proposed method is verified via computer simulation. The results show that the method can simulate ground clutter of radial space-variation effect induced by narrow antenna beam, verifying the effectiveness of the method. This method is applicable to various scenarios.

Handover optimisation for high-capacity low-latency 5G NR mmWave communication

In millimetre wave (mmWave) networks, due to the limited communication range and to the narrow antenna beams, traditional handover techniques might not fully comply with the requirements of high-capacity Ultra Reliable Low Latency Communications (URLLC) applications, such as autonomous vehicles. In this paper, we propose an optimal solution that sets performance boundaries for handover mechanisms. We compare the Fifth Generation (5G) handover mechanism performance with the proposed optimal solution in terms of number of handovers, ping-pong effect ratio, and delay. Our assessment indicates that the 5G handover can be improved to meet the novel applications’ tight constraints, evidenced by a ping-pong effect average reduction of 61%, a 5% increase in average capacity, and at least 17% and 15% increases in the number of messages received before delay expiration for 1 ms and 3 ms delay tolerance, respectively.

Formation-of-Arrays Antenna Technology for High-Throughput Mobile Non-Terrestrial Networks

Effective integration of terrestrial and non-terrestrial segments is one of the key research avenues in the design of current and future wireless communication networks. To this aim, modern communication-satellite constellations intend to attain sufficiently high throughput in terms of bit rate per unit area on the ground by rather aggressive patterns of spatial frequency reuse. This goal calls for on-board narrow-beam antennas, whose size turns out to be in many cases incompatible with the size/mass and accommodation constraints of the hosting satellite. This paper investigates the attainable performance of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">large distributed arrays of antennas</i> implemented as the ensemble of a few to many simpler sub-antennas of smaller sizes, carried by one (small) satellite each. The sub-antennas can in their turn be implemented like (regular) 2D arrays of simple radiating elements, realizing an overall (distributed) antenna architecture that we call “formation of arrays” (FoA). The satellites that implement this radiating architecture need to be relatively close to each other and constitute a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">formation</i> of flying objects, to be coordinated and controlled as a whole. In this paper, we develop a theoretical analysis of an FoA antenna, and we show how to take advantage of this new technology to improve network throughput in a multi-beam S-band mobile communication network with low-earth or geostationary orbiting satellites directly providing 5G-like communication services to hand-held user terminals.

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.

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.

An Ultra-Wideband Vivaldi Antenna System for Long-Distance Electromagnetic Detection

Enlarging or reducing the antenna beam width of antennas can improve the positioning capability of detection systems. A miniaturized and easily fabricated ultra-wideband (UWB) antenna system for long-distance electromagnetic detection is proposed in this article. Two ultra-wideband Vivaldi antennae were designed. One was the transmitting antenna with a beam width of 90° or above, the other was a narrow beam antenna array with beam width less than 10°, as a receiving antenna. Both proposed antennae feature broadside gain diagrams with stable radiation patterns and wideband impedance matching in the frequency range between 2.5 GHz and 4 GHz. After detecting their frequency and time-domain behaviors, the detection system can achieve measurements covering a radius of 30 m.

Clutter Reduction by Estimation of Echoes Direction of Arrival in Distributed Radar Sounders in Formation Flying

Spaceborne radar sounders are High Frequency (HF) / Very High Frequency (VHF) nadir-looking sensors devoted to subsurface investigations. Their data interpretation can be severely hindered by off-nadir surface clutter. Recent literature showed that the clutter suppression capabilities of this class of systems can be greatly enhanced by deploying an array of orbiting sensors in formation flight synthesizing a narrow radar antenna beam. In this paper, we assess the capability of distributed radar sounding to discriminate clutter from subsurface returns by exploiting Direction of Arrival (DOA) estimation techniques. This is achieved by first outlining an approach for designing and evaluating the distributed radar sounder DOA estimation performance as function of the radar system parameters (e.g, inter-sensor distance) and external noise factors such as ionospheric scintillations. Then, the theory is complemented by radar simulations of several acquisitions over Greenland assuming a variety of subsurface geometries. The simulations confirm that clutter discrimination through DOA estimation is a viable approach to further improve the array capability in disambiguation of subsurface echoes from surface ones.

INVESTIGATION OF A MILLIMETER-WAVE RADIO LINK CHARACTERISTICS OF IEEE 802.11AD STANDARD IN URBAN AREAS

Background. The explosive growth in the use of mobile broadband is significantly increasing the bandwidth requirements. Millimeter-wave spectrum is necessary for 5G networks to achieve data transfer rates of the order of Gb/s, in particular, for the provision of 3D video services, and the use radio modules for millimeter-wave frequencies as picocells in the streets will expand the capabilities of existing cellular networks and provide an increase in bandwidth. Therefore, the study of the characteristics of this spectrum is an urgent task today.&#x0D; Objective. The purpose of the paper is to present the results of studying the characteristics of a millimeter-wave radio link to ensure high-speed user access to IP data transmission networks and the possibility of using the IEEE 802.11ad standard in open areas.&#x0D; Methods. Structural and functional methods of constructing a millimeter-wave wireless network in urban areas based on IEEE 802.11ad standard hardware are investigated.&#x0D; Results. The studies were carried out using a test bench with a point-to-point topology deployed in an urban environment (Kiev) with the line of sight without significant obstacles. The studies tested the possibility of using for millimeter-wave hardware technologies of the IEEE 802.11ad standard, which is used indoors, for applications in urban areas.&#x0D; The use of a narrow beam antenna based on an antenna array allows adaptive control of the radiation pattern to bypass small obstacles blocking direct transmission, which allows reducing interference and receive/transmit a signal.&#x0D; Conclusions. Experimental testing of the hardware capabilities of the IEEE 802.11ad standard has been carried out. Scenarios for constructing a millimeter-wave radio link under various weather conditions have been worked out.&#x0D; Keywords: millimeter-wave; bandwidth; IEEE 802.11ad standard; 5G networks

A Novel Hook-Shaped Antenna Operating at 28 GHz for Future 5G mmwave Applications

To address atmospheric attenuation and path loss issues in the mmwave portion of the spectrum, high gain and narrow beam antenna systems are essential for the next generation communication networks. This paper presents a novel hook-shaped antenna array for 28 GHz 5G mmwave applications. The proposed antenna was fabricated on commercially available Rogers 5880 substrate with thickness of 0.508 mm and dimensions of 10 × 8 mm2. The proposed shape consists of a circle with an arc-shaped slot on top of it and T-shaped resonating lengths are introduced in order to attain broad band characteristics having gain of 3.59 dBi with radiation and total efficiency of 92% and 86% for single element. The proposed structure is transformed into a four-element array with total size of 26.9 × 18.5 mm2 in order to increase the gain up to 10.3 dBi at desired frequency of interest. The four-element array is designed such that it exhibits dual-beam response over the entire band of interest and the simulated results agree with fabricated prototype measurements. The proposed antenna array, because of its robustness, high gain, and dual-beam characteristics can be considered as a potential candidate for the next generation 5G communication systems.

一种窄波束天线自动捕获模型的设计与实现

一种窄波束天线自动捕获模型的设计与实现

Cell Partitioning Antenna System Performance in Multi-User Scenarios for mmWave Communications

Fixed-beam, high-gain antenna systems can be used for a finer partitioning of the currently used cell-sectoring. This partitioning has the benefit of reducing the number of users seen per antenna beam, which reduces interference. Furthermore, the high antenna gain allows for a high effective isotropic radiated power while keeping the transmit power low. In this paper, we study the performance of such a fixed-beam, high gain antenna system design for millimeter-wave mobile communications. The antenna system is designed to keep the inter-sector interference in a multi-site scenario low. The performance is analyzed for single- and multi-user environments. In single-input single-output mode, the 50th percentile of the signal-to-interference-plus-noise ratio lies between 12.5 dB to 39.7 dB if 3 to 0 interferers are present, respectively. For multiple-input multiple-output transmission using zero-forcing, the signal-to-interference-plus-noise ratio increases and the 50th percentile ranges from 36.1 dB to 43.3 dB if 3 to 0 interferes are present, respectively. By using maximum ratio transmission, the best performance is achieved with no interferers present, while a plunge in performance is observed with interferers. Furthermore, the study revealed that the narrow beam antenna system can also provide a clear signal separation for small spatial separations. In the given example, the signal-to-interference-plus-noise ratio is larger than 32.1 dB with 11 active antenna elements, where 2.8 meters separate the users. Hence, the paper shows that the cell-partitioning antenna systems provide coverage in the desired area while keeping the inter-sector interference low, and the considered transmission techniques can be used for situation optimized mobile communication links.

Position Location for Futuristic Cellular Communications: 5G and Beyond

With vast mmWave spectrum and narrow beam antenna technology, precise position location is now possible in 5G and future mobile communication systems. In this article, we describe how centimeter-level localization accuracy can be achieved, particularly through the use of map-based techniques. We show how data fusion of parallel information streams, machine learning, and cooperative localization techniques further improve positioning accuracy.

Frequency Domain Panoramic Imaging Algorithm for Ground-Based ArcSAR.

The ground-based arc-scanning synthetic aperture radar (ArcSAR) is capable of 360° scanning of the surroundings with the antenna fixed on a rotating arm. ArcSAR has much wider field of view when compared with conventional ground-based synthetic aperture radar (GBSAR) scanning on a linear rail. It has already been used in deformation monitoring applications. This paper mainly focuses on the accurate and fast imaging algorithms for ArcSAR. The curvature track makes the image focusing challenging and, in the classical frequency domain, fast imaging algorithms that are designed for linear rail SAR cannot be readily applied. This paper proposed an efficient frequency domain imaging algorithm for ArcSAR. The proposed algorithm takes advantage of the angular shift-invariant property of the ArcSAR signal, and it deduces the accurate matched filter in the angular-frequency domain, so panoramic images in polar coordinates with wide swath can be obtained at one time without segmenting strategy. When compared with existing ArcSAR frequency domain algorithms, the proposed algorithm is more accurate and efficient, because it has neither far range nor narrow beam antenna restrictions. The proposed method is validated by both simulation and real data. The results show that our algorithm brings the quality of image close to the time domain back-projection (BP) algorithm at a processing efficiency about two orders of magnitude better, and it has better image quality than the existing frequency domain Lee’s algorithm at a comparable processing speed.

Channel model for simultaneous backhaul and access for mmWave 5G outdoor street canyon channel

Millimeter waves (mmWaves) with very wide frequency bands are proposed for 5G new radio to deliver higher data-speed and capacity. Transmission using mmWaves suffers significant path loss and can be compensated by employing directional antennas. The narrow-beam directional antennas act as spatial filters that filter out multipaths falling outside their beam area. This, together with the insignificance of diffraction and diffused scattering in urban outdoors causes mmWave outdoor channel multipath to be spatially sparse with few specular reflections, posing unique requirements on channel modeling. In this paper, we have derived a low complexity mmWave directional channel model based on ray tracing for the urban microcell street canyon environment. A comprehensive characterization of outdoor links in various realistic scenarios including, line of sight (LOS)/non-LOS, beam aligned/unaligned and road canyon with/without crossroads is presented. The model captures azimuth and elevation directions of propagation in 3D plane by using a highly directional horn antenna design. Atmospheric absorption loss of mmWave is also modeled to enhance the model’s accuracy and generality. The model is validated against measurements reported in the literature. Furthermore, the channel is studied for varying propagation conditions, antenna beamwidths and polarizations, transmitter/receiver heights and positions, and street deployment parameters. Additionally, we propose a metaheuristic algorithm called particle swarm optimization to simultaneously optimize the deployment parameters that minimize path loss as the objective function. The proposed model helps in mmWave system evaluation without the necessity for any costly measurement setup or complex off-the-shelf ray tracing model.

Antenna Tracking Techniques for Long Range Air-to-Ground Communication Systems Using a Monopulse Method

In this paper, we consider long range air-to-ground (AG) communication systems which support airborne platforms including unmanned aerial vehicles (UAVs) for real-time applications. In this system, we design tracking techniques for directional ground antennas which enable reliable AG communication regardless of dynamic maneuvers of the UAV. We apply a simple monopulse method and a fixed gain filtering algorithm to develop a single channel monopulse tracking system with an angular estimation filtering, which exploits a downlink signal without requiring a dedicated channel. Through the AG communication prototype and realistic flight tests, we evaluate the tracking accuracy performance at the distance of hundreds of kilometers and demonstrate the auto-tracking capability of the angular estimation filter. The flight test results show that the tracking accuracy of our proposed system is sufficient for long range transmission with a narrow beam antenna. Also, in the absence of the downlink signal, it is observed that the ground prototype can resume the monopulse tracking procedure, and successfully maintains the tracking accuracy.

Narrow-Beam Antenna for Short-Distance Non-Destructive Sensor in Fruit-Ripeness Monitoring

Radiation pattern subtraction is a useful technique for narrowing a receiving antenna’s radiation pattern in a short-distance, non-destructive sensor. The sensor’s antenna was developed to be compact and light-weight as well as to operate in real-time. This work applied the principle of radiation pattern subtraction to narrow the beamwidth of an antenna. Our experimental data demonstrated that a simple narrow-beam three-element antenna with a 35° half-power beamwidth and a small size of $5.9\times 6.5\,\,\textrm {cm}^{2}$ could be realized. In the experiment, the radiation pattern of an array antenna (consisting of two halfwave dipoles with a reflector) was subtracted from the radiation pattern of an element antenna (consisting of a halfwave dipole with a reflector) for the three-element antenna to achieve a narrow beamwidth and compact size. The antenna had a simple feeding network that operated at 10.525 GHz and 35° half-power beamwidth. The angular resolution of the receiving antenna was tested with mango fruits: it was able to resolve an 80 mm separation between the fruit of interest and the nearby fruit, which was sufficient, in terms of practicality, for mitigating the interfering effect of nearby fruits to the fruit of interest. This type of antenna is useful as a short-distance, non-destructive sensor such as a pre-harvest sensor.

Rework the Radio Link Budget for 5G and Beyond

The 5th generation of mobile communication system (5G) enables the use of millimeter wave frequency bands and beamforming with narrow-beam directional antennas for mobile communication. Accurate estimation of radio link budget which enables direct assessment of achievable cell range or maximum throughput and facilitates network parametrization before deployment is one of the most challenging problems in radio network planning. In contrast to traditional cellular systems, where omni-directional or sectoral antennas are deployed with half-power beam-width much larger than angular spread of the radio channel, the beam-width of antenna arrays assumed for 5G in sub-6GHz and millimeter wave bands can be comparable to or smaller than channel angular spread in scattering environment. Since the effective antenna pattern is determined jointly by the nominal antenna pattern and channel angular spread, it is no longer appropriate to use nominal pattern in radio link budget analysis or system level simulations. Simplified approach, where nominal pattern is assumed for all typical propagation conditions, results in overestimation of the signal power in serving links and underestimation of interference, which in consequence gives erroneous estimation of link budget and leads to unsatisfactory network design and deployment. To avoid inaccurate calculation of link budget while maintaining simplicity it is proposed to modify the simplified approach by using effective antenna patterns. On the other hand, effective antenna pattern can be further optimized by matching its half-power beam-width to the angular spread of the radio channel. It is demonstrated via simulations how to rework the radio link budget for accurate estimation of system performance in high bands for 5G and beyond, along with benefits of effective antenna pattern optimization.