Omnidirectional Antenna System Research Articles

Model-Free Radio Map Estimation in Massive MIMO Systems via Semi-Parametric Gaussian Regression

Accurate radio maps will be very much needed to provide environmental awareness and effectively manage future wireless networks. Most of the research so far has focused on developing power mapping algorithms for single and omnidirectional antenna systems. In this letter, we investigate the construction of crowdsourcing-based radio maps for 5G cellular systems with massive directional antenna arrays (spatial multiplexing), proposing an original technique based on semi-parametric Gaussian regression. The proposed method is <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">model-free</i> and provides highly accurate estimates of the radio maps, outperforming fully parametric and non-parametric solutions.

Analysis of Omnidirectional Antenna Systems Using Cavity Model

Vertically polarized omnidirectional antenna system (VPOAS) and horizontally polarized omnidirectional antenna system (HPOAS) are designed and theoretically analyzed at 2.2 GHz for NAG-Missile telemetry. Theoretical formulations of far-zone field patterns are derived using the cavity model in conjunction with array theory, equivalence theorem, and image theory. The derived radiation patterns are plotted using MATLAB software. The proposed antenna is simulated using CST software and fabricated to validate the derived results. The proposed antenna systems are resonating at 2.22 GHz with 32 MHz impedance bandwidth and peak gain of 4.15 and 5.37 dBi for VPOAS and HPOAS, respectively.

Design and simulation of an adaptive beam smart antenna using MATLAB

&lt;span id="docs-internal-guid-ad3b6b0d-7fff-2d92-685e-3d423ac2713f"&gt;&lt;span&gt;Signals transmitted over a long range of distance may pass through several obstacles and scatter, taking multiple paths to reach the receiver. Beamforming antennas are controlled electronically to adjust the radiation pattern following the first received signal. This allows the antenna to maximize the received signal and consequently, suppress the interfering signals received. A smart antenna should be able to diminish noise, increase the signal to noise ratio, and have better system competence. The adaptive beam makes use of the spacing of the several antennas and the phase of the signal of each antenna array to control the shape and direction of the signal beam. This paper focuses on the use of smart antennas using an adaptive beam method as a better system for the transmission of signals. A simulation between the existing Omnidirectional antenna system and the smart antenna system will be made and compared. The paper will discuss the corresponding advantages that a smart antenna system has compared to the Omnidirectional antenna system.&lt;/span&gt;&lt;/span&gt;

Switchable Filtering Circuit With Single- and Multi-Channel Operations

In this brief, we proposed a switchable filtering circuit with single- and multi-channel operations. It is a six-port circuit, consisting of three sections, namely, a switchable single- and quad-channel filtering circuit, a reconfigurable impedance matching network (IMN), and a single-pole double-throw (SPDT) switch. Two of the ports can be switched to satisfy the requirement of a time division duplexer sub-system, while other four ports can be reconfigured to transmit or receive signals in one channel or four channels. The presented switchable circuit can be utilized as the feeding network of a switchable directive and omni-directional antenna systems by using only directive antennas, while the omni-directional antenna can be eliminated. The design methods and experimental results of the presented switchable filtering circuits are given to verify the proposed ideas.

Novel Switchable Filtering Circuit With Function Reconfigurability Between SPQT Filtering Switch and Four-Way Filtering Power Divider

In this article, we propose a circuit model for designing the switchable filtering circuit with reconfigurable functions between a single-pole quad-throw (SPQT) filtering switch (State 1) and a four-way filtering power divider (State 2) without additional switchable impedance matching network (IMN). The proposed circuit model can be utilized as the feeding network of a switchable directive and omni-directional antenna system to eliminate the omni-directional antenna in conventional solutions to reduce the size and cost. It consists of four filter channels with a common port. In State 1, it works as a SPQT filtering switch, where only one channel is turned on to realize good filtering responses and the impedances at the other three channels are adapted to infinity to realize high isolation. The four channels are turned on simultaneously in State 2 to work as a four-way filtering power divider, and the input impedance of the common port is the same as that in State 1. Thus, a switchable IMN is not required for port matching when switching between the two states. Transmission zeros are generated to enhance the skirt selectivity. For verification, the filtering circuit is constructed using high-$Q$ coaxial resonators. Experimental results show excellent performance in both states acting as a SPQT filtering switch and a four-way filtering power divider.

Design Method for Capacity Enhancement of Pattern-Reconfigurable MIMO Vehicular Antennas

This letter presents a novel design and evaluation procedure for capacity-enhancing multiple-input–multiple-output (MIMO) antenna systems for mobile communication. Based on channel simulations, optimized patterns are defined prior to an antenna design. A multiple-antenna system is proposed, which switches between patterns covering desired directions. This antenna system is then evaluated in an urban environment at 2.49 GHz based on 2 × 2 MIMO channel simulation and measurement results. An improvement of the channel capacity exceeding 1 b/s/Hz compared to an omnidirectional antenna system is confirmed by both simulation and measurement.

Passive CubeSats for remote inspection of space vehicles

Remote inspection can supplement instrumentation to holistically characterize vehicle state, but for space vehicles in flight, inspection is often either risky or costly. We propose using passive inspection CubeSats (PICs) to reliably and affordably image the launch vehicle with fine resolution, moderate coverage, and rapid response. The PICs mission, developed by Brigham Young University undergraduate students and manifested for launch in 2019, is designed to demonstrate this approach using two redundant CubeSats. Each CubeSat uses a spherical array of six cameras, 12 light-emitting diode flash units, and a field-programmable gate array to rapidly boot after separation and capture spherical images of its entire surroundings, including the launch vehicle and other released CubeSats. The PIC bus system includes several custom components, including a compact 3500-mAh battery system, 1 to 2 W solar power system, chassis, omnidirectional antenna system, radio, and a small integrated remove-before-flight-pin and system access port. Preliminary test results suggest the PICs are able to boot within 1.1 s of separation and inspect 1-mm features on each other and their launch vehicle, regardless of the spin developed at separation.

High altitude airborne cellular base stations antenna analysis

Obtaining continual mobile communication coverage over two or more disparate regions from an airborne platform utilizing a deployable cellular base station has proven to be challenging due to the resulting signal spatial structure and signal gain observed from the mobile ground users. A two-dimensional aircraft simulation environment has been developed to evaluate the optimal link budget of an antenna system coupled with a Code Division Multiple Access (CDMA) base station positioned above 45,000 feet in a designated elliptical orbital pattern in an effort to acquire broader and longer communication coverage. This will analyze the signal excess results of both an omni-directional conventional antenna system (CAS) and a switched-beam smart antenna system (SBSAS) with multiple mobile ground users present. Collectively, these results constitute a basis for low-risk implementation for a high altitude airborne deployable cellular base station.

Random Sensory Networks: A Delay Analysis

A fundamental function performed by a sensory network is the retrieval of data gathered collectively by sensor nodes. The metrics that measure the efficiency of this data collection process are time and energy. In this paper, we study via simple discrete mathematical models, the statistics of the data collection time in sensory networks. Specifically, we analyze the average minimum delay in collecting randomly located/distributed sensors data for networks of various topologies when the number of nodes becomes large. Furthermore, we analyze the impact of various parameters such as size of packet, transmission range, and channel erasure probability on the optimal time performance. Our analysis applies to directional antenna systems as well as omnidirectional ones. This paper focuses on directional antenna systems and briefly presents results on omnidirectional antenna systems. Finally, a simple comparative analysis shows the respective advantages of the two systems.

Adaptive antenna arrays for the reverse link of CDMA cellular communication systems

The use of an antenna array in the reverse link of cellular communication systems is proposed. A recursive least squares (RLS) algorithm is used to adjust the weight coefficients of the array. The improvement in performance is quantified by comparison with the omnidirectional antenna system using realistic simulations.

Effects of correlated shadowing signals on channel reuse in mobile radio systems

The authors present a study to evaluate the cochannel interference probability for the desired and interference signals which are correlated due to shadowing. The effects of correlation on the normalized reuse distance are investigated. A generalized expression for the cochannel interference probability is derived by combining uncorrelated (fast) Rayleigh fading and correlated (slow) log-normal signals. The cochannel interference probability for sectorized cell layouts is compared with the lower bound of cochannel interference probability for omnidirectional antenna systems. It is found that omnidirectional cell layouts cause the highest level of cochannel interference probability. An omnidirectional system requires a higher cluster size than a directional system to maintain acceptable cochannel interference.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

UHF omnidirectional antenna systems for large aircraft

This paper discusses the problem of obtaining omnidirectional coverage from antennas operating between 1,000 and 3,000 megacycles on large aircraft. Electromagnetic modeling was used to determine the limitations of several single antenna sites on typical commercial aircraft. Considering all azimuth angles and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\pm30</tex> in elevation to be equally important, the best coverage obtainable from a single radiator is equivalent to the radiation from a free-space dipole for 50 per cent of the time. To improve this, dual antenna systems must be used. Dual antenna requirements depend on whether or not the airborne equipments know when they should be receiving a signal. The distance-measuring equipment (DME) is a typical system that knows when it should be receiving a signal, while radar safety beacon equipment does not know when or from what direction it is being interrogated. Direct parallel feed, the least complicated method of operating dual antennas, allows simple hybrid multiplexing to be used. With this type of operation interference occurs where the individual patterns overlap. Performance in this region is investigated on a probability basis for beacon operation and found favorable; for DME this region is uncertain. In addition, performance is predicted when the RF voltage in one of the dual antennas is (a) shifted periodically in phase, (b) delayed, and (c) interrupted periodically. Considerations involved in an antenna system common to DME and beacon are discussed.