Aircraft Antenna Research Articles

Research on the Strengthening Mechanism of MWCNTs-Cuf Composite Interlayer for Si3N4/TC4 Brazed Joints

With the rapid development of aerospace technology, the high-quality brazing connection between Si3N4 ceramic and TC4 titanium alloy has become a key factor in advancing the development of aircraft antenna covers. To improve the mechanical strength of the joints, this study used the electrophoretic deposition method to prepare a multi-walled carbon nanotubes-foam copper (MWCNTs-Cuf) composite interlayer and selected the optimal deposition parameters. The most suitable brazing parameters under this interlayer were also determined. The joints’ formation mechanism and fracture mode were revealed to elucidate the synergistic strengthening mechanism of the composite interlayer. The results showed that MWCNTs, based on their phase characteristics, produced high-density dislocations and fine crystal strengthening effects during the brazing cooling process. This effectively resisted the corrosion of the brazing material on the foam copper (Cuf), protected the integrity of the foam copper framework, and exerted the excellent plastic deformation ability of foam copper (Cuf). It reduced the residual stress in the joints, resulting in the highest shear strength of the MWCNTs- Cuf composite interlayer, reaching 96.23 MPa. Compared with only adding Ag-Cu-Ti active brazing filler metal and adding ordinary foam copper interlayer, the shear strength increased by 78.2% and 44.7%, respectively.

Method of characteristic modes

In recent years, the number of works on the method of characteristic modes and problems solved with its help has increased significantly, which indicates an awareness of its potential and, in connection with this, a growing interest in this approach. The attractiveness of this method lies in the fact that it provides a clear physical picture of the occurring phenomena and the ensuing opportunity to build on this basis methods for creating structures with the required parameters and combating undesirable phenomena. Unfortunately, in the Russian-speaking segment of applied electrodynamics, very few researchers are engaged in the development and application of the approach under consideration. The purpose of this work is to increase the interest of Russian-speaking researchers in the method of characteristic modes. A review of publications devoted to the method of characteristic modes, both early, fundamental and already classic, associated with the names of R.J. Garbacz and R.F. Harrington, and those which have appeared in recent years and offer generalizations of the method for various electrodynamic structures, has been carried out. This includes composite structures consisting of a set of metal and dielectric bodies of various configurations. In addition, variants of the method for antenna arrays of both infinite periodic and finite sizes have been considered. Issues related to modal tracking problems, orthogonal properties of characteristic modes and improving the convergence of solutions have been considered. Much attention is paid to works containing solutions to specific practical electrodynamic problems using the method of characteristic modes. The works have been shown, in which simple and effective approaches based on the method of characteristic modes are given for the design of a ship's HF antenna system, on-board aircraft antennas in the short-wave region, antennas placed on the platform of a battle tank, and the concept of designing an antenna for an electrically small-unmanned aerial vehicle has been presented. Options for solving the problem of reducing the mutual coupling of elements in antenna arrays have been shown. Attention is paid to MIMO antennas, antennas for smartphones, systems with specified radiation zeros, antennas using metasurfaces. According to the authors, the characteristic mode method, taking into account the increasing possibilities of its application, will make it possible to take the next step in the development, analysis or synthesis of new antenna structures that meet ever-increasing modern requirements.

Preparation of ZrP2O7-CePO4 composite porous ceramics and their excellent thermal insulation and wave-transmission performance for supersonic aircraft

In this study, a two-step method combining the direct foaming process with the control of solid content and heat treatment temperature was employed to prepare ZrP2O7-CePO4 composite porous materials with varying porosities. The results indicate that an increase in solid content and heat treatment temperature leads to a reduction in porosity and average pore size while simultaneously improving the mechanical properties. The porosities, compressive strengths, thermal conductivities, ε and Tanδ ranged from 63.2 to 85.3 vol%, 19.43 to 0.99 MPa, 0.089 to 0.088 W/(m·K), 1.64 to 2.72, and 0.88 × 10−3 to 1.99 × 10−3, respectively. Electromagnetic simulations have validated that ZrP2O7-CePO4 composite porous ceramics, when used as the core layer material for A-sandwich antenna radomes, exhibit excellent transmittance properties. This suggests the potential application of these materials for supersonic aircraft antenna radomes.

Analysis of AMS(R)S VHF Communication and Voice Communication Simulation Using Mathematical Programming Language

To expand the coverage of current aviation VHF communication services, it is necessary to develop a satellite-based VHF communication system. This research aims to analyze the satellite link budget calculations for VHF AMS(R)S frequencies using a Low Earth Orbit (LEO) satellite at an altitude of 600 km, in accordance with the studies conducted by ICAO and ITU. The link budget calculation, using parameters such as aircraft antenna gain = -1 dBi, satellite antenna gain = 8 dBi, RF power of the aircraft = 16 watts, and RF power of the satellite = 85 watts, results in satellite receiver sensitivity between -107 dBm - 25.56 dB, as well as aircraft receiver sensitivity between -93 dBm - 38.65 dB. When simulating an end-to-end link budget (loopback: aircraft-satellite-aircraft between 14.92 dB - 14 dB. Simulations were also carried out for voice communication using an AWGN channel illustration with an Eb/No of 10 dB, resulting in the performance of the VHF audio link.

An Effective Antenna Array Diagnosis Method via Multivalued Neural Network Inverse Modeling Approach

Failure of element (s) in antenna arrays impair (s) symmetry and lead to unwanted distorted radiation pattern. The replacement of defective elements in aircraft antennas is a solution to the problem, but it remains a critical problem in space stations. In this paper, an antenna array diagnosis technique based on multivalued neural network (mNN) inverse modeling is proposed. Since inverse analytical input-to-output formulation is generally a challenging and important task in solving the inverse problem of array diagnosis, ANN is a compelling alternative, because it is trainable and learns from data in inverse modelling. The mNN technique proposed is an inverse modelling technique, which accommodates measurements for output model. This network takes radiation pattern samples with faults and matches it to the corresponding position or location of the faulty elements in that antenna array. In addition, we develop a new training error function, which focuses on the matching of each training sample by a value of our proposed inverse model, while the remaining values are free, and trained to match distorted radiation patterns. Thereby, mNN learns all training data by redirecting the faulty elements patterns into various values of the inverse model. Therefore, mNN is able to perform accurate array diagnosis in an automated and simpler manner.

Airport Spatial Usability in Measuring the Spherical Antenna Properties on Small Aircraft

The strict safety requirements of air transport for nonstandard placement of electronic onboard systems require an innovative approach to the experimental verification of the placement of these devices. Particular attention is required to the location of these electronic devices’ antenna systems on the fuselage. A prerequisite for determining the location of the antenna and verifying its radiation is a thorough knowledge of the radio communication transmission of onboard electronic systems in cooperation with terrestrial or satellite systems. From this point of view, this article focuses on an innovative method of verifying the spherical radiation characteristics of the antenna of an onboard rescue system emergency locator transmitter (ELT) to assess its communication link with the Cospas-Sarsat satellite system. The measurement is performed on a small sports two-seater aircraft with an antenna placed in an unusual place in the aircraft’s cabin, between the seats. It was impossible to use a suitable nonreflective attenuation chamber for the measurement, so we present a method and procedure for this type of measurement in the open space of an airport. The achieved results prove the plausibility and reproducibility of the measurement. Furthermore, combining several polar radiation characteristics makes it possible to obtain an idea, even if only a part, of the spatial (spherical) radiation characteristic. This article presents a simple method of measuring the characteristics of aircraft antennas when it is not possible to use a suitable professional nonreflective attenuation chamber for measurements for various reasons. This method can also be used on other larger means of transport or other objects that experience the same problem.

E ‐band high aperture efficiency reflector antenna with adjustable beamwidth

This paper presents an E-band axial displaced ellipse (ADE) reflector antenna with the characteristics of both high aperture efficiency and adjustable beamwidth. Optimization of slightly shaping the subreflector is adopted for a higher aperture efficiency of the entire antenna. Defocusing effect of moving the subreflector can effectively increase the beamwidth, and half-power beamwidth (HPBW) is adjusted by axially moving the subreflector. The reflector antenna is simulated, fabricated and measured. The aperture efficiency is increased to approximately 75% after optimization. The measured gain of 45.6 ± 1 dBi from 71 to 86 GHz agrees well with the simulation. Also, the measured HPBW achieves an increase of more than five times changing from 0.88° to 4.4° at 71GHz, 0.86°-5° at 86GHz. It is the first time to achieve high aperture efficiency ADE reflector antenna with adjustable beamwidth, which is of great significance for compact aircraft antenna applications.

An offset surface to reduce radar cross section for airborne antenna out‐band

To meet the needs of modern electronic warfare in better stealth performance of the weapon platform, we design an offset surface with metasurface structure, which greatly reduces the radar cross section for airborne antenna. The relation between surface unit size and attenuation frequency guides the design of offset surface that can work in the L-band. The original strategy performed as cross-array structure that plays well throughout the band at different angles, except 30° to 35°. An undesired reflection occurs at this angle gap. Therefore, we attempted to modify the structure as parallel-array structure with same unit size. The results show that modification performs well at all angles in the passband, which meets the design requirements. We processed an offset surface sample and performed a joint test with an aircraft antenna to verify the superiority of the design.

航空天线罩吸波透波一体化设计

航空天线罩吸波透波一体化设计

Microstructural Characterization of Failed Aircraft Antenna

This paper presents the failure analysis of aircraft antenna which is a sub-assembly of Traffic Collision Avoidance System (TCAS) used with Air Traffic Control (ATC) transponder. The base of the damaged antenna (metallic part) is made from Al-based alloy. The micrographs exhibit the typical solidification microstructure consisting of Al-rich matrix along with Si- and Mg-Si-Fe- rich phases. The antenna is coated with the paint consisting of three layers. First and third layers display the presence of Ti and C while second layer consists of Si, Cr and C elements. The small amount of oxygen is also present in all the three layers. The cracks are appeared in the central region of the fin due to impact of external objects (appears to be blankings and particles). Three types of foreign object damage particles are observed on the damaged / hit area. The antenna appears to be damaged during gale as a result of hitting of the large particles lying in aircraft parking area and aircraft engine blankings.

Air-Ground Channel Characterization for Unmanned Aircraft Systems—Part IV: Airframe Shadowing

Applications of unmanned aircraft systems (UAS) are expected to expand dramatically in the coming decades. In order to provide safe and reliable links for UAS, NASA Glenn Research Center sponsored a measurement campaign in 2013 to characterize air-ground (AG) channels. In the first three of our AG channel characterization series papers, path loss, small scale fading, stationarity distance, root mean square (RMS) delay spread, spatial correlations, and tapped delay line models were presented for a range of ground site environment. In this paper, we expand the results to a unique and little-studied characteristic of the AG channels—airframe shadowing—for a medium-sized aircraft. Airframe shadowing occurs when the line-of-sight signal is obstructed by the airplane itself in some specific maneuvers. Based on over 200 aircraft wing/engine shadowing events in both C-band (5060 MHz) and L-band (968 MHz) collected in the measurement campaign, shadowing depth, duration, multiple antenna diversity gain, and small scale fading results and their statistics are reported. Algorithms are proposed to simulate a random shadowing event based upon shadowing depth and duration cumulative density functions. Airframe shadowing characteristics are independent of the local ground site conditions and link distance. The shadowing loss is modeled as a function of aircraft roll angle, but shadowing loss and duration are essentially uncorrelated. The maximum shadowing loss measured was over 35 dB and the duration was up to 74 s. As expected, deployment of multiple aircraft antennas is shown helpful to mitigate this shadowing.

Air–Ground Channel Characterization for Unmanned Aircraft Systems—Part III: The Suburban and Near-Urban Environments

Applications for unmanned aircraft systems (UAS), or “drones,” are increasing rapidly. In order to provide safe and reliable links to integrate UAS into the National Airspace System (NAS), control and nonpayload communication (CNPC) system requirements are being specified. A comprehensive knowledge of the air-to-ground (AG) channels in the bands of interest (C-band and L-band) plays an essential role. The NASA Glenn Research Center has sponsored an AG channel measurement campaign for most of the typical ground site (GS) local environments, including over water [8] , hilly/mountainous [9] , suburban, and near-urban. As a continuation of our prior study, this paper addresses the suburban and near-urban scenarios. Our developed AG channel models include path loss, small-scale fading Ricean K factors, spatial and interfrequency correlations for multiple aircraft antennas, root-mean-square (RMS) delay spread, and wideband tapped delay line (TDL) models. The path loss is described by either log-distance or two-ray models, with small corrections for flight direction. The K factors were 12 (14) dB in L-band and 27.4 (28.5) dB in C-band in near-urban (suburban) environments. The interband signals were uncorrelated, but the intra-band signals were highly correlated, with the median correlation coefficient greater than 0.85. The C-band RMS delay spread was on average 10 to 60 ns, with maximum of approximately 4 μs. The TDL models are composed of the line-of-sight (LOS) component, a ground reflection, and up to seven intermittent multipath components (MPCs). Relative power, phase, occurrence probability, duration, and excess delays for these intermittent MPCs are quantified. An algorithm to simulate the AG channel impulse response (CIR) via the TDL models is provided.

Air–Ground Channel Characterization for Unmanned Aircraft Systems Part II: Hilly and Mountainous Settings

The use of unmanned aircraft systems (UAS) is expanding rapidly. For safe and reliable integration of UAS into the National Airspace System (NAS), control and nonpayload communication (CNPC) system requirements are being developed. The air-to-ground (AG) channel characteristics essentially determine CNPC link performance. The National Aeronautics and Space Administration (NASA) Glenn Research Center has sponsored a comprehensive AG channel measurement campaign in 2013 in both the Land C-bands recently allocated for UAS. These measurements covered nearly all typical ground site (GS) local environments, including over water, hilly, mountainous, suburb, and near urban. As a continuation of results reported for the over-water scenarios, a description of the measurement campaign, measured results, and complete AG channel models for hilly and mountainous terrains are provided in this paper. The path loss is modeled by a modified log-distance path loss model with a correction for flight direction; path loss results are close to those of free space. A strong ground reflection was observed only for some small portions of some of the flight paths. The small-scale fading is well modeled by the Ricean distribution with a K-factor of 29.4 dB in the C-band and 12.8 dB in the L-band. The interband signals are uncorrelated. The spatial correlation for the two intraband channels with an aircraft antenna separation of 1.8 m is greater than 0.85. The C-band root-mean-square delay spread (RMS-DS) is 10 ns most of the time, with a maximum of 1 μs in hilly terrain and 180 ns in mountainous terrain. Tapped delay line (TDL) models accounting for the line of sight (LOS) and up to seven intermittent multipath components (MPCs) were developed, including the MPCs' probability of occurrence, relative power, phase, duration, and excess delay.

Mechanical demodulation of aircraft antenna signal

Presented paper concentrates on accidentally identified, specific method of mechanical vibration demodulation, radiated high-frequency signal of aircraft communication antenna, located directly on the aircraft. It describes the structure and solution of the designed laboratory workplace at which it is possible to evoke mechanical vibration demodulation as a specific phenomenon. The aim is to analyze possible physical electric characteristics of antenna as a source of mechanical vibration on “Monopole“ type of antenna. Next, transfer amplitude frequency characteristics of the antenna, as a mechanical vibration demodulator, are analyzed. As this is a basic research of this accidentally identified phenomenon, an observation method of experiment results is used to find out the analogies by the form of their comparison with a classical amplitude demodulator. The results show that if the mechanic influence of artificial ground is suppressed, the transfer amplitude frequency characteristics of such demodulated signal has minimal distortion in frequency range 200Hz to 3.5kHz. The paper presents brief summary of measured basic values on the base of which obtained results are analyzed and brief conclusions of observed phenomenon are defined. They are the first outputs of the phenomenon observations on the base of which it can be concluded that it is reasonable to deal with this problem. At the same time this is not just the antenna characteristics analysis but also the analysis of mechanical oscillations of the antenna from the viewpoint of its more secure fixing at the aircraft fuselage. Because the concurrent influence of two kinds of vibrations, primary – as a result of aerodynamic circumfluence of antenna during the flight in collaboration with the secondary – as a result of its radiation, places higher requirements on its mechanical fixation. Presented facts mean the increase of air traffic operation.

In situ non-destructive evaluation of an aircraft UHF antenna radome based on pulse-echo ultrasonic propagation imaging

Most aircraft antennas are protected by radomes made of composite materials. However, antenna radome structures are easily damaged by external forces and internal manufacturing defects. To detect damage in the composite antenna radomes while in service, a full-field pulse-echo ultrasonic propagation imaging (PE UPI) system is proposed as an in situ non-destructive inspection technique, which is mobile inside a hangar. The radome is generally a double-curvature structure, and thus, a curvature compensation algorithm is also developed to increase damage visibility. The proposed hardware and software have been tested by detecting a resin rich region formed between the E-glass/epoxy plies. To visualize the damage, PE ultrasonic wave propagation imaging has been performed, and ultrasonic energy mapping has also been applied. A curvature compensating algorithm has been newly developed and compared for its performance in damage visibility improvement. To verify the size of the real defects of a UHF antenna radome, destructive testing has been performed by cutting the defect area, polishing the cross section and investigating the section using a 50× microscope. The results have shown the feasibility of the proposed PE UPI system and the inspection strategy as an in situ non-destructive evaluation technique for radome structures.

Defect visualization of aircraft UHF antenna radome using full-field pulse-echo ultrasonic propagation imaging system

Most of aircraft antennas usually have various types of radome made of composite materials for protecting antenna structures. However, these antenna radome structures, which are installed on the outside of airplane, are easy to be damaged by external forces such as drag, foreign object, bird strike and others. In this study, full-field pulse-echo ultrasonic propagation imaging (PE UPI) system is proposed as the non-destructive inspection technique to visualize manufacturing defects in composite antenna radome. Based on the results of the sample case study, it is shown that the ultrasonic wave propagation imaging (UWPI) that is generated by the proposed full-field PE UPI system is able to highlight the intact internal condition of antenna structure and its defect area. Additional damage visualization techniques like ultrasonic energy mapping (UEM), variable time window amplitude map (VTWAM) and also ultrasonic spectral imaging (USI) algorithms are applied to improve the reliability of the damage visualization. It can be concluded that the proposed PE UPI system is an effective non-destructive inspection technique for the composite radome structures.

Realization of High Speed All-Optical Logic Gates based on the Nonlinear Characteristics of a SOA

Objectives: In this paper the method to overcome the bit rate limitations caused by dual conversion of the signal has been examined. Taking this phenomenon as base for this paper, a novel and potentially integrable circuit design is proposed for the realization of all-optical logic gates based on non-linear properties of SOA. Methods/Statistical Analysis: For this purpose a relatively new method to achieve larger transmission capacity and longer transmission distance with high data rates by employing many logic XOR, AND, OR, NOT gates based on non-linear characteristics of Semiconductor Optical Amplifier (SOA) in optical communication systems is used. Findings: This is done by eliminating the need of optoelectronics conversions and therefore the data remains in the optical domain. This XOR, AND, OR and NOT gate can be executed on 60 gigabits per second on any bit sequence in order to achieve such a high data rate. Application/Improvement: Its application includes Agile radar aircraft antenna system, control of electronic automatic RF attenuator, Automotive courtesy light etc.

Emission analysis of large number of various passenger electronic devices in aircraft

Abstract. The ever increasing use of PEDs (passenger or portable electronic devices) has put pressure on the aircraft industry as well as operators and administrations to reevaluate established restrictions in PED-use on airplanes in the last years. Any electronic device could cause electromagnetic interference to the electronics of the airplane, especially interference at receiving antennas of sensitive wireless navigation and communication (NAV/COM) systems. This paper presents a measurement campaign in an Airbus A320. 69 test passengers were asked to actively use a combination of about 150 electronic devices including many attached cables, preferentially with a high data load on their buses, to provoke maximal emissions. These emissions were analysed within the cabin as well as at the inputs of aircraft receiving antennas outside of the fuselage. The emissions of the electronic devices as well as the background noise are time-variant, so just comparing only one reference and one transmission measurement is not sufficient. Repeated measurements of both cases lead to a more reliable first analysis. Additional measurements of the absolute received power at the antennas of the airplane allow a good estimation of the real interference potential to aircraft NAV/COM systems. Although there were many measured emissions within the cabin, there were no disturbance signals detectable at the aircraft antennas.

CREATE: Software Engineering Applications for the Design and Analysis of Air Vehicles, Naval Vessels, and Radio Frequency Antennas

Today, rapid product innovation is essential to remain competitive. To help spur innovation in the acquisition of major defense systems and reduce their cost, time, and risks, the US Department of Defense launched the Computational Research and Engineering Acquisition Tools and Environments (CREATE) program in 2006 to develop and deploy physics-based, high-performance computing software applications for the design and analysis of military aircraft, ships, and radio frequency antenna systems (and more recently, ground vehicles) through the construction and analysis of virtual prototypes. Code development began in 2008, and eight years later, CREATE is already beginning to accomplish these goals.

A Risk-Based, Practice-Centered Approach to Project Management for HPCMP CREATE

The Department of Defense's High Performance Computing Modernization Program Computational Research and Engineering Acquisition Tools and Environments Computational Research and Engineering Acquisition Tools and Environments (CREATE) program is developing and deploying multiphysics high-performance computing software applications for engineers to design and make accurate performance predictions for military aircraft, ships, ground vehicles, and radio frequency antennas. When CREATE started (2007), no commonly recognized set of successful software project management practices existed for developing multiphysics, HPC engineering software. Based on lessons learned from the HPC and computational engineering communities, CREATE leadership developed and implemented a risk-based, practice-centered strategy to organize and manage the highly distributed program. This approach led to a good balance between ensuring a sufficiently structured workflow and accountability and providing the flexibility and agility necessary to create new sets of engineering tools with the capabilities needed to design next-generation weapon systems.