A two-phase airframe shielding performance study using ultra-wideband measurement systems

Electromagnetic airframe penetration measurements of a Beechraft Premier IA

“…Averaging the penetration data reduces the complex cavity variations and highlights systematic coupHng effects. These effects are discussed in detail in references [1][2][3].…”

“…For anisotropic laminated composites [20] bands [2]. The frequency bands that correspond to our measured data are: (1) 200 MHz to 400 MHz, (2) 400 MHz to 700 MHz, (3) 700 MHz to 1000 MHz, (4) 1000 MHz to 2000 MHz, (5) 2000 MHz to 4000 MHz, (6) 4000 MHz to 6000 MHz, (7) 6000 MHz to 8000 MHz, (8) 8000 MHz to 12000 MHz, and (9) …”

“…Since the reference and airframe measurements were typically carried out at different distances, a distance correction {DC) was applied: (4) where D is the distance in meters from the aperture of the transmitting antenna to the geometric center of the aircraft and D,^/ is the distance between the reference antennas. A detailed description of this procedure is given in reference [3]. Thus, our definition of penetration is based on a comparison of a direct antenna-to-antenna coupling and signal transmission through the airframe.…”

“…The raw frequency data were first filtered to maximize signal-tonoise ratio and to minimize effects from the low-frequency cut-off of our electro-optic link. (3) where SAiigated reference) is the antenna-to-antenna coupling with environmental effects gated out, and S^iigated airframe) is the airframe transmission with gating appUed to minimize noise. Since the reference and airframe measurements were typically carried out at different distances, a distance correction {DC) was applied: (4) where D is the distance in meters from the aperture of the transmitting antenna to the geometric center of the aircraft and D,^/ is the distance between the reference antennas.…”

“…Shielding values were obtained by taking the ratio of the gated amplitude spectra of the aircraft measurement and the gated amplitude spectra of the references. Data smoothing is performed using the frequency-averaging of signal power over a specified bandwidth as described in reference [3], (2) Shielding data were obtained with a receiving antenna located in one of three internal compartments: (1) This report is divided into five main sections: (1) a description of the measurement system, (2) an overview of the measurement technique, (3) an overview of the signal processing, (4) a summary of results obtained for the three different aircraft compartments and various internal measurements, and (5) an uncertainty analysis. Six appendices discuss the impact of time gating, signal and noise, an equipment list, maximum penetration as a ftanction of the HIRF specified frequency bands, the gain characteristics of the ultra wideband antennas that were used, and a discussion of the physical properties, fabrication, and electrical properties of carbon-fiber composite materials.…”