Low-frequency Analysis of multiconductor transmission lines for crosstalk design rules

For early risk assessment in the design of cabling in an aircraft, as well as cable bundle optimization, efficient crosstalk estimations, and dependency of crosstalk with respect to designable parameters are required. A low-frequency technique for analyzing crosstalk in multiconductor transmission lines is presented. The result of this analysis is a closed-form expression for crosstalk in a specific cabling configuration. The technique has been validated via measurements and is used in two examples comprising two wire pairs close to a ground plane and in free space. Low-frequency closed-form expressions for near-end crosstalk are derived for both situations, which directly relate any designable parameter to crosstalk levels. Moreover, these expressions clearly show differences between the cases with and without a ground plane. Specifically, with the ground plane, the decrease in crosstalk when doubling the separation distance is 24 dB for pairs close to the ground, while it is 12 dB in free space. The closed-form expressions are utilized to create an overview of sensitivities of crosstalk to all designable parameters for both configurations. Finally, the low-frequency approximations of the chain parameters are applied to more complex nonuniform transmission lines, yielding more than 20 times faster computations when compared with complete MTL simulations

VHF Antenna Integrated into a Classical Fibre Metal Laminate Fuselage Panel

Replacement of protruding antennas by integrated alternatives will reduce the energy consumption and NOx and CO2 emissions of an aircraft. This paper proposes and integrated VHF cavity backed slot antenna that is suitable to replace blade antennas. To reduce the size of the cavity a parallel plate resonator is used. The slot is integrated into a fibre metal laminate fuselage panel. A bookleafing principle is used to reinforce the panel at the position of the slot, making sure the material quality is not reduced. Measurement results of a demonstrator antenna show the feasibility of the proposed antenna. Moreover, the paper discusses several electromagnetic and structural design trade-offs for this integrated antenna

Mixed-Mode S-Parameter Measurements for Determination of Cable Coupling

Single-ended S-parameters are used to quantify electromagnetic coupling, or crosstalk, between cables. The use of this measurement technique is demonstrated on a case where crosstalk occurs between two wire pairs above ground. S-parameter measurements involve no elements that introduce frequency restrictions, such as baluns or current clamps. Moreover, by measuring or simulating all combinations of S-parameters and converting these to mixed-mode S-parameters, not only differential-mode (DM), but also common-mode (CM) and mode-conversion S-parameters are obtained. When only the coupling between a specific combination of cables is desired, it is sufficient to measure only a small subset of all S-parameters. Finally, the relation between crosstalk as defined in the standards and the obtained S-parameters is discussed

Automated equivalent circuit extraction of impedance curves using a Gauss-Newton algorithm

In this study, an algorithm has been implemented to automate the extraction of passive component values from impedance curves. The method has been applied to a Common Mode (CM) filter. The novelty of this paper lies in the possibility to fit any equivalent circuit to any impedance curve with a relative efficient algorithm. This allows for back-annotation of fields into equivalent circuit simulators

Multiconductor Transmission Line Modeling of Crosstalk between Cables in the Presence of Composite Ground Planes

Modern transportation systems, such as aircraft, are increasingly replacing metal body parts for composite materials, such as carbon-fiber reinforced plastics. Despite the multiple advantages in terms of weight, size, and fuel consumption, this trend is posing a challenge for protection of cables against electromagnetic interference. Early risk assessment and optimization of cable design in modern aircraft require reliable methods that can quickly and accurately estimate crosstalk behavior in the presence of lossy ground planes. This article presents two novel methods to incorporate such lossy ground planes into the crosstalk modeling of cable bundles. The first method considers the ground plane as a discrete collection of cylindrical conductors. In the second method a ground impedance matrix is derived for lossy ground planes with a finite thickness. Results of both methods are compared to full-wave simulations and measurements, yielding excellent results in terms of accuracy and computation times. The discretized ground plane method is also applied to the case of wire pairs that are enclosed by two ground planes, both aluminum and carbon–fiber reinforced plastic, as a first step towards investigation of wiring that is embedded in thermoplastic material. Once more simulations and measurements are in good agreement

A crosstalk sensitivity analysis on bundles of twisted wire pairs

Uncertainties in the geometry of complex cable bundles highly complicate crosstalk predictions. A change in for instance the position or the twist rate of individual cables in a bundle might have an impact on crosstalk levels. Application of sensitivity analyses can indicate which model parameters are most sensitive, and in which cabling configurations. In this paper, the efficient Stochastic Reduced Order Models (SROM) method is used to perform such a sensitivity analysis. It is applied to two cable bundles with two and seven twisted wire pairs, respectively. Monte Carlo simulations are performed to determine the accuracy of the SROM method. The sensitivity of parameters like inter-pair and intra-pair separation distance and the twist rate is determined in two different cases. Moreover, the effects of bundle twist and cable meandering to parameter sensitivities is investigated

Comparing Various Measurement and Simulation Techniques for Estimating Crosstalk

A comparison between crosstalk measurement techniques is made to investigate their applicability and efficiency for determining crosstalk between cables above a ground plane made of copper or carbon-fibre reinforced plastic (CFRP). Cost effectiveness, accuracy, speed and complexity of the methods are evaluated. All measurements are performed on two PCBs containing two pairs of copper traces. The techniques that are considered include balanced Vector Network Analyzer (VNA) measurements, balanced Spectrum Analyzer (SA) measurements, balanced EMI receiver (EMI-R) measurements, single-ended VNA measurements converted to mixed-mode S-parameters, and finally measurements with a signal generator (SG) and an oscilloscope (OSC). For verification, measured results are also compared to three simulation techniques, involving a Method of Moments simulation and two different transmission line models

Mitigating Radiated Emissions of Power Feeders On-board Electric Aircraft

The implementation of all-electric aircraft (AEA) will face several engineering challenges mainly due to its high power requirements. At its core lies the electric powertrain, consisting of the battery, inverter, and motor. Non-ideal behavior of components, cables, and other structures will act as a propagation path for Electroagnetic Interference (EMI). The analysis of EMI in the design phase is considerably complicated due to structural and geometric design, thus, hard to predict. This paper is a first step towards proposing the attenuation of radiated emissions from power feeders by optimizing the switching behavior of converters. Thus, contributing to the overall attenuation level and reducing the performance requirements of power line filters