Antenna Radiation Pattern Measurement Research Articles

Measurement technique for increasing the allowable dimensions of antennas tested in a collimator installation

Large collimator setups are often in use for antenna radiation pattern measurements. Their quiet zone size limiting the allowable dimensions of the antenna under test, as a rule, do not exceed a half of the collimator’s profile. Retrieving ARP from measurements in a non-ideal environment can be a means to expand the working area. The subject of the article is such a technique based on of the representation of a real field by a converging cluster of plane waves. It turned out that at the stage of studying the field of the collimator, despite the requirements of the uniqueness theorem, measurements may be carry out on a certain limited area of the boundary surface. Acceptable results are obtained when the working area is up to 90% of the collimator cross section.

Relay-Aided Wireless Sensor Network Discovery Algorithm for Dense Industrial IoT Utilizing ESPAR Antennas

Industrial Internet-of-Things (IIoT) applications require reliable and efficient wireless communication. Assuming dense wireless sensor networks (WSNs) operating in a harsh environment, a concept of a time-division multiple access (TDMA)-based WSN enriched with electronically steerable parasitic array radiator (ESPAR) antennas is proposed and examined in this work. The utilized antenna provides one omnidirectional and 12 directional radiation patterns that can be electronically switched by the sensor node. We introduce a relay discovery algorithm, which selects those sensor nodes with an ESPAR antenna capable to act as relay. The selection of the relay nodes is based on a certain link quality threshold that algorithm uses as input. The outcome is a reduction in the number of layers or hops with a guaranteed Quality of Service (QoS). To emphasize the physical aspect of the wireless propagation, we introduce the measured antenna radiation patterns and consider two different path-loss propagation models representing blockage-free and blockage-prone industrial environments. A number of network simulations were performed and signal-to-noise ratio (SNR) as a link quality measure was examined with respect to the network density and different measured radiation pattern settings. The main outcomes show a tradeoff between SNR per link and the percentage of nodes that can serve as relays. As a result, we propose network design guidelines that take under consideration the QoS range with respect to SNR together with an optimal number of antenna radiation patterns that should be selected as a tradeoff between latency, energy consumption, and reliability in a network.

On Actual Maximum Exposure From 5G Multicolumn Radio Base Station Antennas for Electromagnetic Field Compliance Assessment

The traditional approach of radio frequency electromagnetic field exposure compliance assessment is highly conservative when applied to radio base station antennas implementing dynamic beamforming. In this article, an analytical model based on the queuing theory with a hyperexponential service distribution time is developed to assess the time-averaged actual maximum downlink exposure of 5G multicolumn radio base station antennas by taking into account the effects of beam scanning over time in free space. Using the measured antenna radiation patterns, the 5G downlink antenna precoding codebook, and assuming a conservative user equipment distribution, the ratio of the actual maximum exposure to the theoretical maximum exposure with 100% traffic load and 75% time-division duplex downlink duty cycle is found to be less than 0.5 and 0.3 for four-transmitter and eight-transmitter radio base station antennas, respectively. These results show that assuming constant peak power transmission in a fixed direction leads to an overestimate of downlink exposure also from conventional antennas characterized by only a few transmitters in addition to massive multi-input multi-output products.

Analysis of the operating conditions for UAV-based on-board antenna radiation pattern measurement systems.

Communications, navigation, and other related systems need to have a well-defined antenna radiation pattern. In onboard vessel systems, the radiation pattern can be much different than the one obtained for an isolated antenna (because of the vessel’s structure and other nearby radiating systems interference). Finding out the onboard antenna’s radiation pattern is a well-known problem for any shipbuilder/owner. The conventional method consists of measuring radiation patterns from a fixed antenna on the coast while the ship is navigating in circles. Recent electronic systems in the market now allow for an alternative method: keeping the ship static while an unmanned aerial vehicle (UAV) circles it, measuring the antenna’s transmitted power. This research paper examines the airspace volume and optimal flight path of an off-the-shelf UAV system for measuring the onboard antenna’s radiation pattern in the presence of physical constraints such as the vessel’s dimensions, safety zone, distance to base, Fresnel’s and multipath distances, and considering the loss due to polarization decoupling between the antenna under test and UAV’s antenna.

Generation of Radiation Patterns Equivalent to In-Flight Measurements

Comparison of in-situ measured antenna radiation patterns (RPs) to modeled ones is vital for validation of both. Inflight measured RPs do not always produce a standard conic or elevation cut (constant θ or ϕ angle, respectively), but rather Great Circle (GC) cuts at the aircraft bank angle of interest. WIPL-D’s post-processing routines, on the other hand, do not produce GC cuts in normal setups. A manipulation of the aircraft orientation in xyz-coordinates is required to accomplish this task. Under standard conditions in WIPL-D, the fuselage is positioned parallel to the x-axis and the wings parallel to the y-axis. A model rotation of 90° with respect to the y-axis allows for the generation of GC cuts, where θ and ϕ swap roles. This makes comparison between in-flight measurements and computed data cumbersome. This paper investigates several options to produce non-standard RPs in WIPL-D and MATLAB (using WIPL-D results) that are equivalent to those of in-flight measurements.

Study on Impedance Matching of 2.4 GHz Dipole Antenna

Understanding on matching impedance between feedline and load is important in many aplication. Theoritically, matching impedance can be calculated easily if charateristic impedances both load and line is known. Practically, when we do impedance matching at certain frequency we face a problem if the impedance of the feedline and antenna are unknown. by using vector network analyzer and anechoic chamber we tried to study and to approach the impedance match through measurement of return loss, VSWR, and antenna radiation pattern. The results of studies have shown that adjusting dipole antennas to lines can be done by optimizing antenna and lines length and subsequently optimizing the use of balun. In this reasearch we optimized 2.4 GHz dipole antenna and matched it to feedline by using bazooka and balun 1 : 1. To achieve good matching, the antenna length is 0.35 λ and the feedline length multiplies 0.5 λ. The length of the bazooka and balun for the best impedance adjustment are 0.25 λ and 0.2λ.

Preliminary design of the implementation of automatic antenna radiation pattern measurement: Study of Yagi antenna radiation pattern

The radiation pattern is an important parameter of the antenna performance. This parameter needs to be measured not only accurately but also as fast as possible. For this purpose, the automatic measurement system has been developed. In this research, the system is implemented to analyze the radiation characteristic of a Yagi antenna by measuring its radiation pattern. The measurement result of the patterns is compared to those of the table characteristics of the Yagi antenna as well as a computer simulation. For this purpose, a Yagi antenna is designed and realized as the radiation pattern measurement object. Then, the students experiment to measure and analyze the effect of parasitic elements on the radiation pattern performance of the antenna. The questionnaire is carried out as the method of the research and directed to the students of the Telecommunication Study Program, Bandung State Polytechnic, to get the perception of the object performance.

Antenna Radiation Pattern Measurement in a Reverberating Enclosure Using the Time-Gating Technique

This letter describes an original approach to measure the radiation pattern of an antenna within reverberating enclosures. In such kinds of enclosures creating a multipath environment, the key point is to distinguish the line-of-sight (LOS) path between the antenna under test and the measuring antenna from all the other indirect paths. This is made possible by taking advantage of the time-gating technique, considering that the LOS path arrives the first on the measuring antenna. With respect to the existing methods proposed recently, the method leads to significantly simplify the measurement setup and shorten the measurement time (similar to the one obtained in anechoic chamber) as no stirring process or any movement of the antenna under test (apart of course from the rotation on itself) is required. Moreover, the accuracy of this method is presumably better in reason of the ability of the time-gating technique to discard the influence of the indirect paths. The proposed technique tested for the first time within reverberating enclosures is experimentally validated on a broadband horn antenna from 1.5 to 12 GHz. The main parameters influencing the result (the measurement bandwidth, the frequency resolution, the time-gating window width, and the effect of loading the enclosure) are discussed.

Millimeter-Wave Base Stations in the Sky: An Experimental Study of UAV-to-Ground Communications

This paper adopts a systems approach to study how millimeter wave (mmWave) radio transmitters on UAVs provide high throughput links under typical hovering conditions. With Terragraph channel sounder units, we experimentally study the impact of signal fluctuations and sub-optimal beam selection on a testbed involving DJI M600 UAVs. From the hovering-related insights and the measured antenna radiation patterns, we develop and validate the first stochastic UAV-to-Ground mmWave channel model with UAVs as transmitters. Our UAV-centric analytical model complements the classical fading with additional losses expected in the mmWave channel during hovering, considering 3-D antenna configuration and beamforming training parameters. We specifically consider lateral displacement, roll, pitch, and yaw, whose magnitude vary depending on the availability of specialized hardware such as real-time kinematic GPS. We then leverage this model to mitigate the hovering impact on the UAV-to-Ground link by selecting a near-to-optimum pair of beams. Importantly, our work does not change the wireless standard nor require any cross-layer information, making it compatible with current mmWave devices. Results demonstrate that our channel model drops estimation error to <inline-formula><tex-math notation="LaTeX">$\approx$</tex-math></inline-formula> 0.2 percent, i.e., 18x lower, and improves the average PHY bit-rate by <inline-formula><tex-math notation="LaTeX">$\approx$</tex-math></inline-formula> 10 percent when compared to existing state-of-the-art channel models and beamforming methods for UAVs.

Synthesis of a Radiator in the Frequency Range of 0.9…5.8 GHz

Introduction. In this work, we consider the problem of a radiator synthesis with the 50-Ohm port at the input in the frequency range of 0.9…5.8 GHz. At present, this frequency range is the most relevant for the electromagnetic environment analysis due to information exchange with the on-board equipment of unmanned aerial vehicles is most often realized in this frequency range.Objective. The main objective of this work is the synthesis of a radiator for an ultra-wideband antenna array in the frequency range of 0.9…5.8 GHz.Materials and methods. In this work, the method of full-wave electromagnetic simulation is used for the broadband radiator synthesis. The characteristics of the radiator are optimized by simulation and confirmed by experimental investigations of the radiator model. The antenna radiation pattern measurements are carried out in the anechoic chamber and standing wave ratio (SWR) is calculated by using the network analyzer.Results. A non-analytical method of the model parametric optimization considering the SWR&lt;2 criterion and using the latest tools of the full-wave electromagnetic simulation is proposed. The examples of the designed optimized model with the final values of all parameters are reported. The calculated distributions of the electric field over the antenna, calculated radiation patterns at several frequency points, and calculated SWR of the model are presented. The radiator model is made taking into account simulation and optimization results. The measured main cross-sections of the radiation pattern and SWR of the model are shown. Conclusion. In the present work, the broadband radiator model in the frequency range of 0.9…5.8 GHz is designed. The machining and brief comparative analysis of the calculated and measured antenna characteristics is carried out and demonstrated a good agreement. The advantages of the proposed method and designed radiator model are described. The results of this work are relevant in the tasks of observation, direction finding and signals reception from unmanned aerial vehicles. Key words: ultra-wideband antenna, Vivaldi antenna, microwave range, full-wave electromagnetic simulation&gt;&lt;2 criterion and using the latest tools of the full-wave electromagnetic simulation is proposed. The examples of the designed optimized model with the final values of all parameters are reported. The calculated distributions of the electric field over the antenna, calculated radiation patterns at several frequency points, and calculated SWR of the model are presented. The radiator model is made taking into account simulation and optimization results. The measured main cross-sections of the radiation pattern and SWR of the model are shown.Conclusion. In the present work, the broadband radiator model in the frequency range of 0.9…5.8 GHz is designed. The machining and brief comparative analysis of the calculated and measured antenna characteristics is carried out and demonstrated a good agreement. The advantages of the proposed method and designed radiator model are described. The results of this work are relevant in the tasks of observation, direction finding and signals reception from unmanned aerial vehicles.

A printed expanded graphite paper based dual band antenna for conformal wireless applications

A flexible paper based and dual-band antenna is designed for UMTS service (1.9 GHz) and WiMAX services (5.8 GHz). Flexible paper is used as a substrate for the printed antenna. Expanded graphite ink is used to enable printing the antenna on the substrate. The antenna has been designed, simulated, fabricated, and measured. Steps of preparing the conductive printed ink and fabrication of the antenna have been discussed. The conductivity of the printed antenna is measured to be 1 × 104 S/square and the thickness is also measured with an average of 30 µm. Through the whole paper, good agreement between simulated and measured results is satisfied. In addition to the achieved flexibility, the antenna has demonstrated good measurement results. First, the antenna has a bandwidth of 300 MHz at 1.9 GHz and 400 MHz at 5.8 GHz with fractional bandwidth of 15.7% and 6.8% at the both bands, respectively. Second, the measured antenna radiation pattern has indicated that it is omnidirectional at 1.9 GHz and approximately omnidirectional at 5.8 GHz. Third, The antenna gain is 1.266 dB and 0.512 dB at the two bands, respectively. Finally, the antenna’s efficiency at the both bands is 35% and 55%.

Spatial modulation based on reconfigurable antennas: performance evaluation by using the prototype of a reconfigurable antenna

In this paper, we study the performance of spatial modulation based on reconfigurable antennas. Two main contributions are provided. We introduce an analytical framework to compute the error probability, which is shown to be accurate and useful for system optimization. We design and implement the prototype of a reconfigurable antenna that is specifically designed for application to spatial modulation and that provides multiple radiation patterns that are used to encode the information bits. By using the measured antenna radiation patterns, we show that spatial modulation based on reconfigurable antennas works in practice and that its performance can be optimized by appropriately selecting the radiation patterns to use for a given data rate.

A Tunable Single-Feed Triple-Band LTE Antenna With Harmonic Suppression

This paper presents a single-feed planar inverted-F antenna (PIFA) that operates at three resonant frequencies within the LTE frequency range which would result in the enhancement of the antenna bandwidth and the increase of the data-rate speed. The antenna is designed to satisfy the requirements of carrier aggregation systems (intraband non-contagious type) cell-phone applications. The three resonant frequencies are independently tunable within the low-band (0.7-1 GHz), mid-band (1.6-2.1 GHz), and highband (2.1-2.7 GHz), respectively, using varactor diodes as tuning devices. Each varactor diode represents a variable capacitor controlled by biasing dc voltage. A parallel LC harmonic-trap filter is built inside the antenna to suppress the harmonics generated by the low-band resonance, which enhances the tuning capabilities at the high-band. The antenna has a size of 375 mm2, which is considered to be a low-profile design and placed on a 100 × 66 × 3.154 mm 3 RO4003C (e r = 3.55) printed circuit board. The measured antenna radiation patterns in each band are nearly isotropic as expected from the PIFA and the measured antenna radiation efficiency is 25-80% within the entire LTE frequency bands.

Phase interpolation Fourier transform beamforming for spatial division applications

The spatial division represents an efficient approach to increasing data throughput in wireless networks. It can be implemented by spanning the channel in spatial domain with orthogonal beams generated by a Fourier transform (FT) beamforming network and using each beam to simultaneously convey an independent data stream from the base station (BS) to several users. This study presents a feasibility study of a simplified BS front-end architecture based on a spatial discrete FT beamforming network, with the number of the output ports being lower than the number of the elements in the antenna array. It is shown that connecting each output port of the FT network via power dividers to several array elements, thus implementing a `sample-and-hold' phase interpolation, preserves the orthogonality, gain and beam-width in a narrow scanning sector. Therefore, in applications where few orthogonal beams are required to span a narrow spatial sector, the proposed approach can offer a reduction of the hardware complexity. The simulated radiation patterns for a phase interpolation Fourier beamforming network are demonstrated. The measured antenna radiation patterns are reported for the architecture implemented with a Fourier Rotman lens and Wilkinson power dividers feeding a microstrip antenna array, which confirm the simulated trends.

Antennas and propagation course in education

In this paper, an approach for teaching basic antenna theory and propagation to senior level undergraduate students for electrical engineering related fields is proposed and described. The method combines mathematical and theoretical studies with antenna design and laboratory measurements to reinforce the subject’s theoretical and practical aspects together. Topics discussed in lectures include performing antenna radiation calculations, learning how to make antenna radiation pattern measurements, and designing of antennas such as microstrip patch antenna. The education is based on teaching these principles and enabling students to make some antenna measurements. At the end of the semester, an analysis on learning outcomes of the course was performed and feedback from students was taken. The feedback from students showed that there was a huge satisfaction in terms of achieving the goals in learning outcomes. The course structure proposed can be a good example for instructors who teach antennas and propagation courses.

Synthesis of Shaped-Beam Radiation Patterns at Millimeter-Waves Using Transmit Arrays

Transmit arrays have been mostly used for beam collimation applications, either with fixed or scanning beam capability. But transmit arrays can also be used to synthesize power radiation patterns complying with power pattern templates. A new analytical formulation is presented here to obtain a phase-only correction function corresponding to a given power template. The transmit-array transforms the known power radiation pattern of the primary source into a desired output power pattern. The proposed formulation, specialized for axial-symmetric structures, is based on geometrical optics and provides the solution directly from the evaluation of two closed-form first-order differential equations. As a proof of concept, a sec2 with a roll-off at 45° is defined as the target power pattern, at the 30 GHz Ka-band. A 10.8 dBi radiation pattern with the circular polarization is used to illuminate a 180 mm $\times \,\, 180$ mm transmit array with 60 mm focal distance. Previously designed 3.35 mm thick phase-delay unit cells are used as an example to implement the calculated phase distribution over the transmit-array aperture. The measured antenna radiation pattern matches quite well the template, with a steep fall of the radiation at the roll-off angle and low cross-polarization. This validates the concept, the formulation, and the fabricated prototype.

3-D Antenna Radiation Pattern Reconstruction in a Reverberation Chamber Using Spherical Wave Decomposition

It has been shown that the correlation between the radiation patterns of two antennas can be measured in a reverberation chamber (RC). In this paper, it is shown that the self-correlation coefficient of an antenna, defined as the correlation between the radiation pattern of an antenna under test (AUT) and a transformed version of itself, can also be measured in an RC. It is found that the 3-D radiation pattern of the AUT can be reconstructed from the measured self-correlation coefficient by using spherical wave decomposition. Moreover, the axial ratio of the AUT can also be measured efficiently in the RC, when the pattern is directional. Numerical simulations and measurements in the RC and in an anechoic chamber have been undertaken. Good agreement is obtained, which confirms the validity of the proposed method. Thus, this novel method can become a very useful, cost-effective, and efficient method for 3-D antenna radiation pattern measurement.

Design and Measurement of a Differential Printed Antenna for a Wireless Sensor Network Node

This letter presents the design and measurement of an antenna integrated into an agricultural sensor network node operating on the 2.4-GHz ISM band using the ZigBee protocol stack. The novel structure, coined bowtie-shaped folded dipole (BSFD) , has a differential 100- $\Omega$ input impedance matching a particular controller widely used in wireless sensor network (WSN) applications. This letter also presents a survey of existing WSN antennas to which the proposed design compares favorably. The challenges of testing a differential antenna using conventional single-ended equipment are addressed regarding antenna impedance and radiation pattern measurements. The differential antenna input impedance was confirmed with four different test setups using a conventional vector network analyzer. The radiation pattern of the proposed antenna was measured in-prototype resorting to a spectrum analyzer. The measured patterns show that the proposed antenna has a maximum received power over 4 dB compared to two early versions of the WSN node that used commercial off-the-shelf antenna solutions. The performance was also confirmed in a field test where a BSFD-equipped prototype achieved close to a 300-m range, tripling that typical for ZigBee applications.

Studying the Influence of Opening Angles of Planar Short Slot Microwave Antennas on Their Electrodynamic Characteristics

We study the characteristics of planar symmetric slot antennas with linearly expanding openings, whose dimensions are comparable with a radiation wavelength of 30 mm. The radiation patterns of the antennas under consideration are calculated experimentally, measured experimentally, and analyzed for opening angles of 60°, 90°, and 120°. The influence of the antenna opening angle on the directivity of the antennas is revealed. The experimentally measured antenna radiation patterns are found to agree well with the developed mathematical models at the frequencies (10 ± 2) GHz.

Simplified human phantoms for narrowband and ultra-wideband body area network modelling

Purpose – The purpose of this paper is to compare the properties of simplified physical and corresponding numerical human body models (phantoms) and verify their applicability to path loss modeling in narrowband and ultra-wideband on-body wireless body area networks (WBANs). One of the models has been proposed by the authors. Design/methodology/approach – Two simplified numerical and two physical phantoms for body area network on-body channel computer simulation and field measurement results are presented and compared. Findings – Computer simulations and measurements which were carried out for the proposed simplified six-cylinder model with various antenna locations lead to the general conclusion that the proposed phantom can be successfully used for experimental investigation and testing of on-body WBANs both in ISM and UWB IEEE 802.15.6 frequency bands. Research limitations/implications – Usage of the proposed phantoms for the simulation/measurement of the specific absorption rate and for off-body channels are not within the scope of this paper. Practical implications – The proposed simplified phantom can be easily made with a low cost in other laboratories and be used both for research and development of WBAN technologies. The model is most suitable for wearable antenna radiation pattern simulation and measurement. Social implications – Presented results facilitate applications of WBANs in medicine and health monitoring. Originality/value – A new six-cylinder phantom has been proposed. The proposed simplified phantom can be easily made with a low cost in other laboratories and be used both for research and development of WBAN technologies.