The design is presented for a broadband high-impedance surface (HIS) and this technology is applied in the field of aircraft EMC. The HIS is analysed by means of a lumped-element equivalent circuit model and a parametric study is undertaken to understand the effect of each parameter on the resonant frequency and bandwidth of the structure. The design of a structure with a bandgap of 2–6 GHz (100% bandwidth) is detailed. TLM simulation and measurement validation of the structure's reflection phase and surface current suppression characteristics show good agreement with each other. An application for the proposed structure, employed on the nacelle of an aircraft, protecting against the penetration of surface currents into sensitive areas, is also discussed.

Some critical avionic systems require cooling air via vents on the side of the aircraft, thus creating leakage points for high-intensity electromagnetic radiation. This paper presents a novel application of high-intensity radiated field (HIRF) shielding using a rectangular waveguide array, while maintaining cooling airflow requirements. Signal attenuation versus frequency and depth of the array has been calculated using closed-form equations. The simulation and measurement results are in good agreement with the calculated values. (C) 2004 Wiley Periodicals, Inc.

Digital avionics systems are increasingly under threat from external electromagnetic interference (EMI). The same avionics systems require a thermal cooling mechanism and one method of providing this is to mount an air vent on the body of the aircraft. For the first time, a nacelle-mounted air vent that may expose the flight critical full authority digital engine controller (FADEC) to high intensity radiated fields (HIRF) is examined. The reflection/transmission characteristics of the vent are reported and the current shielding method employed is shown to provide a low shielding level (5 dB at 18 GHz). A new design has been proposed, providing over 100 dB of attenuation at 18 GHz. To the authors' knowledge this is the first time this shielding method has been applied to aircraft air vents.

The shielding effectiveness of two woven carbon fibre composite (CFC) materials has been calculated using plane wave shielding theory and effective medium theory. Both methods provide the same shielding result. Measurements of the shielding effectiveness using an X-band waveguide show similar levels of shielding to that of aluminium. The high shielding level is due to the large concentration of carbon in both composite samples (50.5%).

The attenuation/transmission characteristics and hence High Intensity Radiated Field (HIRF) immunity of a jet engine nacelle air vent, called a NACA Scoop, are reported. For the first time, results from simulations using a TLM based solver and measurements of the NACA Scoop in an anechoic chamber are discussed and compared.

Radiation incident on aircraft can cause high intensity radiated fields (HIRF) to be present close to electronic systems. This threat is made more serious by the fact that some electronic systems need to be cooled via air ducts on the side of the aircraft, creating leakage points for electromagnetic radiation. One such electronic system is the Full Authority Digital Engine Controller (FADEC). The FADEC is cooled from airflow through a duct called a NACA (National Advisory Committee for Aeronautics) Scoop, located on the side of the engine nacelle. This paper examines the electromagnetic characteristics of the duct and determines the efficiency of existing HIRF protection. The paper also proposes a new method for HIRF protection and considers other applications for the method.

An air vent mounted on the side of a jet engine nacelle provides cooling for on-board electronics. This paper investigates the geometry of the air vent and predicts the effect the geometry has on incident electromagnetic radiation. Simulations using 3D-TLM were performed to provide power density plots at 3 GHz and 8 GHz for two bounding areas of incident radiation. The field plots were used to predict how radiation was entering the vent. The return loss of the vent has also been calculated for the two bounding areas.