Antenna Placement Research Articles

A cost-effective beam forming structure for global navigation satellite system multipath mitigation and its assessment

AbstractArray antenna beam forming has high potential to improve the performance of the global navigation satellite system (GNSS) in urban areas. However, the widespread application of array antennas for GNSS multipath mitigation is restricted by many factors, such as the complexity of the system, the computation load and conflicts between required performance, cost budget and limited room for the antenna placement. The scope of this work is triplicate. (1) The pre-correlation beam forming structure is first suggested for multipath mitigation to decrease the system complexity. (2) With the pre-correlation structure, the equivalence of adaptive beam forming to quiescent beam forming is revealed. Therefore, the computational load for beam forming is greatly decreased. (3) A theoretical model is established to link the benefits of beam forming with GNSS performance improvement in terms of pseudorange quality. The model can be used by industry to balance the aforementioned restrictions. Numerical results with different array settings are given, and a 2 × 2 rectangle array with $0.4\lambda $ element spacing is suggested as a cost-effective choice in GNSS positioning applications in urban canyon areas.

Reducing the radar cross section while maintaining the performance of a coplanar waveguide-fed antenna with an absorptive metasurface

The paper presents, for the first time, an analysis of the optimum arrangement of a coplanar waveguide-fed monopole antenna and a metasurface absorber (MSA), aiming to reduce the antenna’s in-band radar cross section (RCS) without perturbing its radiation properties. The proposed arrangement will show that the efficiency of the antenna, of great interest in many applications (such as the internet of things), can be preserved, contrary to results of previous papers focused on combining these structures. Moreover, the final structure will be easily embeddable (with an optimum number of unit-cells) as well as conformable. A proper analysis of the losses and currents on the structure will be provided for a better understanding of the interaction phenomena that arise. Good agreement between simulation and measurement results can be observed, corroborating the proper performance of the structure. Furthermore, bistatic reductionis obtained as well as monostatic RCS reduction, due to the angular stability of the employed MSA. Finally, it will be shown that the introduction of loaded resistors will be preferable to the use of a lossy dielectric to improve the RCS reduction whilst maintaining the antenna performance.

Percutaneous Microwave Ablation: Applications for Liver; Recommendations for COVID-19 Patients

Microwave ablation (MWA) is an alternative to surgical resection of solid tumors and plays an essential role in the treatment of malignancies and is widely used for hepatic tumors. This paper reviews all the commercial devices and the most recent noncommercial designs and principles behind them alongside the recent ly reported developments and issues of MWA. The paper also provides microscopic insights on effects of microwave irradiation in the body. Based on our review we conclude that MWA is a safe and effective minimally-invasive method with high ablation completion rates. However, for large tumors the completion rates slightly decrease, and recurrences increase. Thus, for large tumors we suggest using multiple antenna placements. Some comparisons between the two common ablation frequencies 915 MHz and 2.45 GHz have shown inconsistent results mainly due to non-identical conditions. This review suggests that 915 MHz devices are more effective for ablating large tumors and the theory behind MWA effects corroborates this proposition. For small tumors or tumors adjacent to vital organs, however, 2.45 GHz is suggested due to its more localized ablation zone. Among the antenna designs, the double-slot antenna with metallic choke seemed more effective by localizing the radiation around the tip of the antenna and preventing the backward radiation towards the skin. MWA should be considered for COVID-19 patients with hepatic tumors as a fast treatment with a short recovery time. As liver injury is one of the risk factors for COVID-19 patients, liver function tests including ALT and AST, and bilirubin measurements are recommended. Moreover, the patient treated with drugs including remdesivir, tocilizumab, lopinavir, chloroquine and hydroxychloroquine need more intensive monitoring. Considering MWA for all patients is highly suggested during pandemics when the clinical resources are stretched to capacity. Funding: This research was financially supported by the Natural Sciences and Engineering Research Council of Canada and by University of Guelph COVID-19 Research Development and Catalyst Fund.Conflict of Interest: The authors declare that they have no conflict of interest.

Experimentally Analyzing Diverse Antenna Placements and Orientations for UAV Communications

A vast array of potential applications is emerging for drones and other devices to collaborate from disaster relief and search and rescue missions to smart agriculture and IoT systems. As drones move across multiple altitudes, they must have the ability to communicate across any direction in a three-dimensional (3D) space. However, due to the heterogeneous nature of the drone body and its interaction with the mounted antennas, different antenna positions on the drone can result in variations in the radiation pattern. While there have been a fair number of airborne communication works, few consider the role that antenna positioning has on the resulting transmission along the azimuth and elevation planes. In this work, we study the effects of the drone body and various antenna placements on the radiation pattern and fading of drone-based channels. Through systematic anechoic chamber and in-field measurements, we show that the drone body alters the radiation pattern of the mounted antennas, rendering the common assumption of a constant azimuth radiation pattern invalid. In addition, the body increases polarization mixing of drone-based channels, resulting in significant degradation of the cross-polarization discrimination (XPD). Hence, we propose using effective radiation pattern and XPD values instead of relying on measurements and/or assumptions that disregard drone-antenna interaction. We then analyze the shadowing and losses associated with the drone body for many antenna setups at various elevation angles and show that when mounted on the opposite side from the ground transmitter, shadowing increases with relatively-higher drone elevations. To account for these body-induced effects, we introduce rotational loss that results in better prediction results of the large-scale fading behavior compared to conventional models that neglect these body effects. Then, we analyze the small-scale fading for various antenna setups and show that the Rician K-factor is strongly dependent on elevation for polarization-matched vertical links, while it is approximately flat for cross-polarized links. To do so, we conduct a set of drone-to-drone (DtD) experiments at high altitudes with no surrounding reflectors and compare results to those obtained by our ground-to-drone (GtD) measurements. We find that, while at low elevations the ground can reduce the K-factor by 10 dB, at higher elevations, small-scale fading is dominated by the antennas, not the ground.

An Analysis of Free-hand Targeting in Laparoscopic Liver Microwave Ablation.

Recently, new technologies have been developed for antenna placement in laparoscopic liver tumor ablation (LLTA). At this point, it is important to analyze the efficacy of free-hand targeting to identify deficiencies and opportunities for improvement. This was an institutional review board-approved retrospective study. Video recordings of 30 consecutive patients with 77 lesions who underwent LLTA were reviewed. Tumor-specific anatomic and targeting-related parameters were analyzed using χ2, t test, and regression analyses. Neuroendocrine metastasis was the dominant tumor type, with median tumor size 1.4 cm (range, 0.5 to 5.2). In total, 41 (53%) tumors were superficial and 36 (47%) deep. In 68 lesions (88%), an optimal targeting was achieved with first attempt, without a need for repositioning; whereas 9 lesions (12%) required repositioning of antenna. For 37% (15/41) of superficial and 56% (20/36) of deep lesions, a straight avascular needle trajectory was not present, requiring steering of the antenna around vascular and biliary structures. All procedures were completed laparoscopically without bleeding or biliary complications. Local treatment recurrence rate in follow-up was 10% (n=8). This study shows that in experienced hands, LLTA through free-hand technique is safe and efficacious, providing an accurate targeting with the first pass in 90% of tumors. Although newer technology is being developed to guide less-experienced surgeons in needle targeting, it should be kept in mind that a straight trajectory is not available for 1/3 of superficial and half of deep lesions. Hence, ablation surgeons need to develop free-hand skills to avoid possible hemorrhagic and biliary complications in LLTA.

Current-controlled magnon propagation in Pt/Y3Fe5O12 heterostructure

We present a dynamic spin wave (SW) modulation technique using direct current (DC) to manipulate the magnetic properties of an ultralow-damping Y3Fe5O12 thin film. The microwave excitation and detection technique with two coplanar waveguide antenna arrangements on the Y3Fe5O12 (YIG) surface is used to characterize the SW. An additional platinum (Pt) stripe connected to a current source is integrated between the coplanar waveguide pair to demonstrate the SW resonant frequency and amplitude modulation by current induction. We selected a Pt stripe due to its significantly lower spin wave absorption property. The application of current through the Pt stripe generates local joule heating that modifies the magnetic properties of the YIG film. Temperature variation through local heating modifies the saturation magnetization of the YIG film, which, in turn, modulates the SW frequency. Moreover, the amplitude of the SW spectra is found to be tuned by the current amplitude. This phenomenon is mainly described by magnon–magnon scattering induced by the spin Seebeck effect in the case of local heating. Furthermore, the group velocity of the proposed device is also found to be responsive to the current, which has been explained by both magnon–magnon and magnon-phonon scattering.

Asynchronous electric field visualization using an integrated multichannel electro-optic probe

The higher the frequency, the more complex the scattering, diffraction, multiple reflection, and interference that occur in practical applications such as radar-installed vehicles and transmitter-installed mobile modules, etc. Near-field measurement in “real situations” is important for not only investigating the origin of unpredictable field distortions but also maximizing the system performance by optimal placement of antennas, modules, etc. Here, as an alternative to the previous vector-network-analyzer-based measurement, we propose a new asynchronous approach that visualizes the amplitude and phase distributions of electric near-fields three-dimensionally without placing a reference probe at a fixed point or plugging a cable to the RF source to be measured. We demonstrate the visualization of a frequency-modulated continuous wave (FMCW) signal (24 GHz ± 40 MHz, modulation cycle: 2.5 ms), and show that the measured radiation patterns of a standard horn antenna agree well with the simulation results. We also demonstrate a proof-of-concept experiment that imitates a realistic situation of a bumper installed vehicle to show how the bumper alters the radiation patterns of the FMCW radar signal. The technique is based on photonics and enables measuring in the microwave to millimeter-wave range.

Reconfigurable ULAs for Line-of-Sight MIMO Transmission

This paper establishes an upper bound on the capacity of line-of-sight multiantenna channels over all possible antenna arrangements and shows that uniform linear arrays (ULAs) with an SNR-dependent rotation of transmitter and/or receiver can closely approach such capacity—and in fact achieve it at low and high SNR, and asymptotically in the numbers of antennas. Then, as an alternative to mechanically rotating ULAs, we propose to electronically select among multiple ULAs having a radial disposition at either transmitter or receiver, and we bound the shortfall from capacity as a function of the number of such ULAs. With only three ULAs, properly angled, 96% of the capacity can be achieved. Finally, we further introduce reduced-complexity precoders and linear receivers that capitalize on the structure of the channels spawned by these configurable ULA architectures.

On the Optimal Placement of Base Station Antennas for Distributed Antenna Systems

In this letter, we aim to optimize the placement of base station (BS) antennas for maximizing the average ergodic sum capacity of a multi-user distributed antenna system (DAS). Different from previous studies where deterministic optimization approaches were usually taken, we formulate the BS antenna placement as a stochastic optimization problem, and propose a stochastic-gradient-descend-based algorithm to effectively solve it. Simulation results demonstrate that the proposed algorithm converges fast and provides significant gains in average ergodic sum capacity over the existing representative BS antenna placement schemes.

Ruggedized Surface-Mount Omnidirectional Antenna for Supersonic Aerial Platforms

A rugged metal protected antenna that produces an omnidirectional radiation pattern is proposed in this letter. The omnidirectionality is achieved by using a cavity enclosed printed circuit board (PCB) with λ/4 transformers and ground shortening pins combination. The slotted cavity filled with ablative material is designed to maintain the radiation characteristics of the enclosed PCB and provide strength for the antenna arrangement, which can be effectively used on high-speed aerial platforms. The simulated and measured results demonstrate that the proposed antenna possesses a stable omnidirectional radiation pattern; its horizontal gain is higher than -1.5 dB, the azimuthal gain ripple is within ±0.7 dB, and the antenna efficiency exceeds 85% over the entire operational frequency band. In addition, the conformal, tapered, nonprotruding, low-profile, and dc-grounded design makes winged antennas a superior candidate for supersonic (Mach > 1) airborne applications.

Mathematical model of optimization of preventive maintenance of transmitting active phased antenna arrangements of multifunctional radars

In the article, the authors discuss the issues of determining the reliability indicators and maintenance of transmitting active phased array antennas (AFAR) of multifunctional radars. The analysis of the existing models of reliability and maintenance of AFAR radar. It is shown that the most interesting models of transmitting AFAR reliability are the reliability model with a two-level block diagram of the AFAR and the reliability model according to the criterion of permissible reduction of the maximum radar range. Among the AFAR maintenance models, the most interesting ones were identified: the AFAR optimal preventive maintenance (ON) model with a single-level structure and the AFAR maintenance model by technical condition. Using the results of the analysis, models of reliability and optimal preventive maintenance of a multi-functional radar transmitting AFAR are constructed. The analytical expressions of the reliability indicators of a two-level AFAR are presented: the average operating time to failure and the probabilities of failure-free operation of the antenna transmitting sublattice and the transmitting AFAR as a whole. Analytical expressions are constructed for the criteria for the effectiveness of optimal software (coefficient of technical use and mathematical expectation of specific operating costs) and the criteria for gaining from software optimization. The work considers an illustrative example of calculating the reliability and optimal software of a two-level AFAR, including 6400 microwave emitting channels, arranged in 100 sublattices with 64 channels each. The mean operating time to failure and the optimal periodicity of the AFAR software were determined for three versions of the reliability indicators of the emitting channels. The graphs of the probability of failure-free operation, the coefficient of technical use and the mathematical expectation of the specific operational costs of the AFAR were constructed and analyzed. The values of the optimal periodicity and the gain from optimization are obtained. It is shown that the results of optimal software should be used at the initial stage of operation of radars with AFAR — at the stage of warranty service. At further stages of operation - the stages of post-warranty service, it is recommended to use the AFAR maintenance method according to the technical condition. The models proposed by the authors can be useful to engineers and scientists developing radars with AFAR and employees of operating organizations.

Optimal Antenna Arrangement for Self-Interference Cancellation in Short-Range Full-Duplex MIMO

A self-interference cancellation (SIC) method is presented for short-range full-duplex multiple-input-multiple-output (MIMO) communication. The proposed SIC consists of the following steps. First, each peer has multiple transmitting (Tx) and receiving (Rx) antennas optimally arranged to form a one-rank self-interference (SI) matrix between Tx and Rx. The optimal antenna arrangement is derived using a geometric model. Second, null steering is performed by eigenmode beamforming excluding the primary eigenmode of the SI matrix. This realizes powerful SIC at the cost of processing just a single degree of freedom. The effectiveness of the proposed SIC is evaluated by electromagnetic simulations. The results confirm that it reduces the SI level by 22.76 dB. In addition, it is shown the proposal offers achievable rates 1.50 times those of the half-duplex scheme in line-of-sight (LOS).

Optimization of discharge antenna turn and modulation of EEPFs and plasma parameters in dual-frequency cylindrical ICP source at different gas pressures

This paper deals with the optimization of the number of discharge antenna turns N, mainly including the effect of N on the plasma parameters [plasma density ne, effective electron temperature Teff, plasma potential Vp, power transfer efficiency η, and electron energy probability function (EEPF)] in cylindrical inductively coupled plasma (ICP) source, and compares axial and radial distribution of ne with different antenna arrangement topologies, mainly referring to the non-interleaved and interleaved antenna arrangement in cylindrical dual-frequency (DF) ICPs. It is found that the cylindrical DF-ICPs with interleaved antenna arrangement can produce a higher ne due to the superposition effect of the high-frequency (HF) and low-frequency (LF) discharge region. Furthermore, based on the above optimized parameters, an optimized cylindrical DF-ICP with an interleaved antenna arrangement is employed, and the modulations of EEPFs and plasma parameters (ne, Teff, and Vp) in the case of (1) fixed HF power and varying additional LF power and (2) fixed LF power and varying additional HF power correspondingly are investigated and compared at different gas pressures of 1, 15, and 60 mTorr systematically. With the wide gas pressure range from 1 to 60 mTorr considered in a combination with two discharge frequencies of 2 and 13.56 MHz, the DF discharge covers discharge maintenance under different conditions with respect to electron heating mechanisms, e.g., collision-less and collision heating. This is a relatively comprehensive work about cylindrical DF-ICPs, which will provide some insights into the design and plasma parameters modulation of cylindrical DF-ICPs.

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The main features of an efficiency evaluation of positional (stationary and autonomous) sonar systems at the design stage and deciding on the coordinates of the antenna installation site based on modeling and visualization of the expected surveillance zones using intelligent geographic information systems are considered in the paper. The issues of intellectual decision support for the rational spatial distribution of receiving antennas are considered. The influence of the information support quality of geographic information systems on the calculations accuracy of expected surveillance zones of the sonar systems under the various hydrological and acoustic conditions is assessed. A new performance indicator in the form of spatial volume of the expected surveillance zone is proposed. A method for solving the optimization problem of finding the maximum volume of the illuminated space as a coordinates function of the antenna placement within a given observation area, with fixed technical characteristics of the monitoring system and given noise conditions, acoustic characteristics of the detection object and the observation time has been developed. The proposed approach to selecting the rational variant of the receiving antennas location of positional hydroacoustic facilities and systems in the interests of dispatching geospatial processes using as a mean of intelligent support the modern hardware and software complex realizing the specified selection by such efficiency indicator as volume of illuminated space, in the conditions of a two-dimensionally inhomogeneous model of medium, close to real hydrological-acoustic conditions, allows to increase the accuracy of assessing the illumination efficiency of underwater environment of positional hydroacoustic means and systems and significantly reduce the design and development time as compared with the traditional approach, requiring expensive field observation over a long period of time.

Метод попереднього планування безпроводової локальної мережі стандарту IEEE 802.11

Examines various approaches of planning in the design of wireless network standard IEEE802.11 inthe premises. The article gives formulas and the calculation method of tasks a fixed number of users on point, and the results of simulation designing Wi-Fi network based on the program D-Link Wi-Fi Planner Pro. The program is designed for the initial analysis of the floor plan with the aim of placing it on the access points Wi-Fi. She focused on the use of the equipment D-Link, to allow for the different room settings, in particular, not only the actual floor space, but the type, material and number of partitions. In addition, D-Link Wi-Fi Planner Pro allows you to conduct calculations similar to automatic access point placement or manual. When the AP placement is very important to determine what materials are made of walls, floors, structural elements and furniture in the room, and had given this to hold equipment placement and selection of antennas to be used with access points. Keep in mind that the effective distance has a value, which will decrease the radius of action after the passage of the relevant obstacles compared to open space, and the fact that the signal decreases proportional to the square of the distance, so speed comes naturally as the distance from the access point. D-Link Wi-Fi Planner Pro showed that the audience need to install 1 (2.4 GHz) access point and 3 (in the 5 GHz band) to provide a coating with a signal level not worse than -65 dBm (for providing students with only Internet access). As can be seen, results of analytical and simulation planning only partially coincide, so when planning Wi-Fi networks need to plan the placement of access points with specialized software, not forgetting to reduce the power of each of the access points to the power level of the WiFi chip built into the tablet student.

Antenna Placement in a Compressive Sensing-Based Colocated MIMO Radar

Compressive sensing (CS) has been widely used in multiple-input-multiple-output (MIMO) radar in recent years. Unlike traditional MIMO radar, detection/estimation of targets in a CS-based MIMO radar is accomplished via sparse recovery. In this article, for a CS-based colocated MIMO radar with linear arrays, we attempt to improve the target detection performance by reducing the coherence of the associated sensing matrix. Our tool in reducing the coherence is the placement of the antennas across the array aperture. In particular, we choose antenna positions within a given grid. Initially, we formalize the position selection problem as finding binary weights for each of the locations. This problem is highly nonconvex and combinatorial in nature. Instead, we find continuous weight values for each location and interpret them as the probability of including an antenna at the given location. Next, we select antenna locations randomly according to the obtained probability distribution. We formulate the problem for the general case of a MIMO radar with independent transmit and receive arrays for which we propose an iterative algorithm. For the special case of a transceiver array, the solution is obtained through a convex optimization approach. Our experiments show that the proposed method achieves a superior detection performance compared to a uniform random placement of the antennas within the array aperture.

Spurious radiation suppression in microstrip monopulse antenna

Purpose This paper aims to introduce a new novel microstrip monopulse comparator system to reduce the spurious radiation from the comparator and the feed network for achieving better radiation performance. Design/methodology/approach Two substrate layers have been used for the microstrip monopulse comparator system. The feed network and the comparator circuits are on the first substrate layer and the microstrip array antenna is on the second layer. The elements of the array antenna are novel square four-sided narrow rectangular slot antennas built on a conducting plane. A commercially available computational software, CST microwave studio, has been used for the analysis of the system. Findings Two substrate layers have been used for the microstrip monopulse comparator system. The feed network and the comparator circuits are on the first substrate layer and the microstrip array antenna is on the second layer. The elements of the array antenna are novel square four-sided narrow rectangular slot antennas built on a conducting plane. A commercially available computational software, CST microwave studio, has been used for the analysis of the system. Practical implications The system is proposed for tracking moving targets. Originality/value Novel slot radiators are introduced as radiating elements in this paper. The antenna arrangement shields the comparator and the feed network circuits, reducing the spurious radiation significantly.

Massive MIMO Antenna Arrangement Considering Spatial Efficiency and Correlation between Antennas in Mobile Communications

Massive MIMO Antenna Arrangement Considering Spatial Efficiency and Correlation between Antennas in Mobile Communications

Implementing an IoT based Remotely Controlled Antenna Positioning System

wireless communication systems rely on antennas for signal reception. Proper placement of antennas is important to achieve successful wireless communication according to satellites / transmitters. Manual antenna changes are often risky in a way that usually results in unexpected accidents and can lead to death. To determine its position, the sensors are mounted on the antenna, and the motors change their position. Because the location of a transmitting station changes over time, antenna path must also be changed accordingly. This system will track the location of the antennas and provide new coordinates for the antenna positioning. Correctly position antenna is done by this system. We are therefore proposing an IOT based antenna positioning system that enables antennas to be placed remotely based on IOT. The paper explains how to implement the current and evolving technologies in Antenna Positioning. We can essentially use this device to place antennas respectively in the desired direction using IoT.

An improved aperiodic OPA design based on large antenna spacing

In practical large-scale optical phased array (OPA) design, large antenna spacing is required to accommodate the device size and the routing area. Therefore, under the traditional uniform antenna arrangement, grating lobes result in very limited field of view (FOV). Fortunately, the grating lobes limiting the FOV can be suppressed by aperiodic OPA. Here, we analyze the performance of the aperiodic OPA with large spacing, and propose an improved aperiodic OPA design by proper antenna arrangement to increase the side mode suppression ratio (SMSR). For a 512-channel aperiodic OPA whose antenna spacing is larger than 10λ and smaller than15λ, >15dB SMSR is achieved.