Abstract-Several popular metallic bistatic calibration objects are investigated, including a sphere, long and short cylinders, dihedral, trihedral, circular disk and wire mesh. Comparisons are made between the advantages and disadvantages of various objects for calibration. The analysis addresses sensitivity to object alignment error, availability of accurate radar cross section (RCS) calculations and bistatic RCS levels. Both theoretical concepts and practical considerations are discussed based on measurements accomplished at the European Microwave Signature Laboratory (EMSL) of the EC Joint Research Center (JRC) in Ispra, Italy. This facility has the capability to produce far-field fully polarimetric precision bistatic measurements in a 30 cm diameter quiet zone, suitable for comparing different calibration objects.
The Poisson sum formula provides an efficient method for transforming many slowly converging infinite summations into equivalent, but more rapidly converging infinite summations. Electromagnetic applications for this result come in the analysis of infinite arrays of periodic scatterers, such as frequency selective surfaces. However, in some applications, such as when one desires the radiation of a semi-infinite array of periodically spaced currents, the original form of the Poisson sum formula is inappropriate. For such applications, we derive a one-sided version of the formula and apply it to the radiation from a semi-infinite array of line sources with currents dictated by Floquet's theorem. The one-sided Poisson sum transformation yields enhanced convergence characteristics for certain regions of application as a result of the inverse bandwidth relationship between Fourier transform pairs. The application of it to a semi-infinite line source array also provides a plane wave representation for the fields, which makes for an extension of the solution to geometries with stratified dielectric media.
The field electron emission of carbon nanotubes has been heavily studied over the past two decades for various applications, such as in display technologies, microwave amplifiers, and spacecraft propulsion. However, a commercializable lightweight and internally gated electron source has yet to be realized. This work presents the fabrication and testing of a novel internally gated carbon nanotube field electron emitter. Several specific methods are used to prevent electrical shorting of the gate layer, a common failure for internally gated devices. A unique design is explored where the etch pits extend into the Si substrate and isotropic etching is used to create a lateral buffer zone between the gate and carbon nanotubes. Carbon nanotubes are self-aligned to and within 10 microns from the gate, which creates large electric fields at low potential inputs.Initial tests confirm high field emission performance with an anode current density (based on total area of the device) of 293 µA cm -2 and a gate current density of 1.68 mA cm -2 at 250 V.
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