# TD-UTD Solutions for the Transient Radiation and Surface Fields of Pulsed Antennas Placed on PEC Smooth Convex Surfaces

**ABSTRACT** A time-domain formulation of the uniform geometrical theory of diffraction (TD-UTD) is developed for predicting the transient radiation and surface fields of elemental pulsed antennas placed directly on a smooth perfectly conducting, arbitrary convex surface. The TD-UTD solution is obtained by employing an analytic time transform (ATT) for inverting into time the corresponding frequency domain UTD (FD-UTD) solution. An elemental antenna on the convex surface is excited by a step function in time and a TD-UTD solution is obtained first. The TD-UTD response to a more general pulsed excitation of the elemental current is then found via an efficient convolution of the TD-UTD solution for the step function excitation with the time derivative of the general pulsed excitation. In particular, this convolution integral is essentially evaluated in closed form after representing the time derivative of the general pulsed excitation by a small sum of simple signals whose frequency domain description is a sum of complex exponential functions. Some numerical examples are presented to illustrate the utility of these TD-UTD solutions for pulsed antennas on a convex body.

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**ABSTRACT:**A time-domain (TD) analysis of ellipsoidal reflector antennas is presented to predict the transient scattered fields when it is illuminated by a cosine-tapered and transient-step feed radiation whose phase center is located at the nearby focus. A transient-step function of the feed's radiation is considered because it will produce an impulsive response near the second focus of the reflector as interested in the applications of impulse-radiating antennas. This TD solution is in a closed form and remains valid both near and far from the reflector, and can be used via the convolution theorem to efficiently obtain the early time transient fields generated by the same ellipsoidal reflector antenna when it is illuminated by a realistic finite-energy pulse which emanates as a spherical wave from the focus. Numerical results are presented for the transient fields both near and far from the reflector.IEEE Transactions on Antennas and Propagation 01/2012; 60(1):328-339. DOI:10.1109/TAP.2011.2167919 · 2.46 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**This paper presents an analytical and closed-form solution, using a time domain (TD) physical optics (PO), for the fast analysis of transient scattering from a finite and perfectly conducting ellipsoidal surface when it is illuminated by a transient-step plane wave. The advantage of ellipsoidal shapes to resemble a variety of realistic surfaces such as spherical, parabolic or planar surfaces allows the developed solution applicable to model a realistic scattering object such as an aircraft in an effective fashion. Physical appealing interpretation of wave phenomena in terms of reflection and diffraction mechanisms is also provided in the solution. Numerical examples are presented to demonstrate its physical phenomena of scattering mechanisms.IEEE Transactions on Antennas and Propagation 01/2012; 60(1):340-350. DOI:10.1109/TAP.2011.2167930 · 2.46 Impact Factor -
##### Conference Paper: A solution for the transient field diffracted by an obtuse-angled dielectric wedge

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**ABSTRACT:**A solution is proposed in the time domain framework for evaluating the field diffracted by an obtuse-angled penetrable wedge in the case of pulsed plane waves orthogonally impinging on the edge. It takes advantage of the knowledge of a uniform asymptotic solution based on a Physical Optics approximation for the surface currents involved in the radiation integral. The corresponding frequency domain diffraction coefficients are used to determine the time domain counterparts in closed form via the inverse Laplace transform. Numerical tests and comparisons with Finite Difference Time Domain results confirm the effectiveness of the solution.Radar Conference (EuRAD), 2012 9th European; 01/2012