Impact of In-Situ Radome Lightning Diverter Strips on Antenna Performance

Lightning diverter strips are commonly used to protect the antenna and sensitive equipment within an airborne radome. This paper compares the impact of solid metallic and segmented diverter strips on the radiation properties of the enclosed antenna. Solid metallic and segmented diverter strips of different segment profiles, i.e., square, circular and diamond, are considered. The paper reports how the placement of diverters on the radome and their geometric detail affect the antenna parameters, namely reflection coefficient and far field pattern. Furthermore, the surface electric field intensity on segmented diverter strips is analyzed for different shapes, sizes and separations between the metallic segments

Coupled electrothermal two-dimensional model for lightning strike prediction and thermal modeling using the TLM method

This paper presents a fully coupled two-dimensional (2-D) multiphysics model for predicting the location of the arc discharge and lightning channel, and modeling its thermal and electrical behavior as a highly conductive plasma channel. The model makes no assumptions on the physical location of the lightning channel but predicts its appearance purely from the electromagnetic (EM) field conditions. A heat diffusion model is combined with the time-varying nature of the EM problem where material properties switch from linear air material to a dispersive and nonlinear plasma channel. This multiphysics model is checked for self-consistency, stability, accuracy, and convergence on a canonical case where an arc channel is established between two metal electrodes upon exposure to an intensive electric field. The model is then applied to the 2-D study of a diverter strip for aircraft lightning protection

Stretched-coordinate PML in 2D TLM simulations

A novel implementation of the stretched coordinate perfectly matched layer (PML) is presented for the two-dimensional (2D) transmission line modelling (TLM) method. The formulation offers a unified approach and is based on the mapping of the TLM node to a complex stretched domain for which the resulting transformation of the constituent RLC transmission line components is elaborated. The transformation is shown to modify the TLM connect-scatter algorithm. The absorption performance is demonstrated by simulating a canonical waveguide test case. Unlike the existing split-field based TLM-PML implementations, which are better suited to lossless media, the numerical results obtained show the proposed PML formulation is effective in the termination of both lossy and lossless media

Statistical Characterization of Wireless MIMO Channels in Mode-Stirred Enclosures

We present the statistical characterization of a 2x2 Multiple-Input Multiple-Output wireless link operated in a mode-stirred enclosure, with channel state information available only at the receiver (agnostic transmitter). Our wireless channel measurements are conducted in absence of line of sight and varying the inter-element spacing between the two antenna elements in both the transmit and receive array. The mode-stirred cavity is operated: i) at a low number of stirrer positions to create statistical inhomogeneity; ii) at two different loading conditions, empty and with absorbers, in order to mimic a wide range of realistic equipment level enclosures. Our results show that two parallel channels are obtained within the confined space at both the operating conditions. The statistical characterization of the wireless channel is presented in terms of coherence bandwidth, path loss, delay spread and Rician factor, and wideband channel capacity. It is found that the severe multipath fading supported by a highly reflecting environment creates unbalance between the two Multiple-Input Multiple-Output channels, even in presence of substantial losses. Furthermore, the channel capacity has a multi-modal distribution whose average and variance scale monotonically with the number of absorbers. Results are of interest in IoT devices, including wireless chip-to-chip and device-to-device communications, operating in highly reflective environments

Practical limitation on operation of nonlinear parity-time Bragg gratings

The paper analyses the operation of PT Bragg gratings when the dielectric material is considered to be both dispersive and nonlinear and gain and loss are saturable. The paper demonstrates the application of the nonlinear PT Bragg Grating as an optical logic gate and an optical switch

Installed antenna performance in airborne radomes of different profiles

In this paper, broadband interactions between an antenna and a radome are modelled using a full wave numerical solver. By accurately describing both the antenna and the radome geometry with a single numerical method, a comprehensive prediction of the performance of the coupled antenna and radome installation is provided. The paper compares how different airborne dielectric radome profiles affect the antenna performance, predicting effects not seen in uncoupled simulations

Practical limitation on operation of nonlinear parity-time Bragg gratings

The paper analyses the operation of PT Bragg gratings when the dielectric material is considered to be both dispersive and nonlinear and gain and loss are saturable. The paper demonstrates the application of the nonlinear PT Bragg Grating as an optical logic gate and an optical switch

Modelling of dispersive PT-symmetric Bragg grating

This paper reports on the time-domain numerical model of a parity-time Bragg grating with saturated and dispersive gain. The model is compared against the ideal PT scenario where the gain is constant and unsaturated for all frequencies