Abstract-Aircraft skins manufactured from carbon fibre reinforced plastic (CFRP) can simultaneously support structural load and act as antennas. This offers the potential for disproportionately large antenna elements and arrays, and thus enhanced aircraft capability. The efficient design of such structures requires that the link between CFRP microstructure and electromagnetic performance be established. This paper presents a method of predicting the electromagnetic attenuation of waveguides manufactured from CFRP. The method considers both the orthotropic, complex conductivity of CFRP, high in the fibre direction and low transverse to it, and the local electric fields in waveguides, which vary with location and frequency. The method was validated experimentally using waveguides manufactured from aerospace grade IM7/977-3 prepreg tape with [
This letter presents an improved image-based coherent Doppler tomography (CDT) technique for near-field radar cross-section measurement. The present formulation, developed using the back-projection algorithm, explicitly incorporates the network analyzer calibration in the near-field to far-field transformation. Experimental measurements and computer simulations are presented to validate the improved CDT technique.
Carbon fibers are finite conductors with a weak diamagnetic response in a static magnetic field. When illuminated with a high-frequency alternating electromagnetic wave such that the skin depth is greater than the fiber diameter, carbon-fiber composites are shown to exhibit a strong dynamic diamagnetic response. The magnetic susceptibility (χm) is controlled by the polarization angle (θ), which is the angle between the incident electric field and conductor direction. A closed form solution for this behaviour was derived using Maxwell's equations and an understanding of the induced conductor currents. The equation was verified using simulation and free space “wall” and waveguide measurements on unidirectional IM7/977-3 carbon fiber reinforced polymer laminates. The measured responses ranged from non-magnetic at θ = 90°, χm = 0, up to strongly diamagnetic at θ = 30°, χm = −0.75, over the 8-18 GHz bandwidth. The experimental results are in good agreement with theoretical predictions and computational simulations.
An electrically small, metamaterial-inspired Egyptian Axe Dipole (EAD) antenna has been investigated for use in structural composite materials. The EAD antenna consists of a differentially-fed dipole element integrated with a near-field resonant parasitic (NFRP) EAD element. These elements have been adapted to these materials resulting in a system that is impedance matched and radiates efficiently at 307 MHz. Three cases have been identified and investigated to ascertain the performance of the manufacturing techniques and material properties used to build these electrically small antennas (ESAs), as well as their performance characteristics. Uniquely, an embroidered conductive thread and a new carbon fiber based, non-woven mat have been investigated for use as the conducting elements. Both cases are compared with a copper variant of the EAD antenna. All three prototypes were tested. Measurements confirm that both the non-woven mat and the embroidered versions of the EAD antennas perform similarly, with maximum realized gains ranging from 1.72 -1.90 dBi.
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