Electromagnetic Modeling of an Aperture-Coupled Patch Array in the N-Port Layered Waveguide for Spatial Power Combining Applications

Abstract

An integral equation formulation is proposed for the analysis of waveguide-based aperture-coupled patch arrays for use in spatial power combining systems. A method of moments discretization is used to reduce a coupled set of integral equations t o a matrix system resulting in the Generalized Scattering Matrix (GSM) for the Nport waveguide transition. In addition, the GSM for a rectangular waveguide taper is obtained using a mode-matching technique. Receiving and transmitting waveguide modules are cascaded to obtain the GSM of the entire passive structure. The proposed electromagnetic algorithm has been incorporated in a modeling environment for the analysis of complete waveguide-based aperture-coupled patch amplifier arrays, including passive elements and active devices. Introduct ion In recent years, an increased interest in open and waveguide-based spatial power combining systems [1,2] has created opportunities for the modeling and design of efficient high-power combiners and for a better understanding of power combining mechanisms in free space. This includes full-wave electromagnetic modeling of passive guided-wave structures, field-circuit interfacing techniques (i.e. active devices coupled into the electromagnetic environment), and the modeling of multimoding, coupling and radiation effects. In this paper, we present a full-wave integral equation formulation of an aperturecoupled patch array in the layered N-port waveguide transition. This is developed for the analysis of a complete waveguide-based amplifier array, which includes receiving and transmitting waveguide tapers, N-port patch-to-slot waveguide transitions, and amplifier networks [3]. The analysis of the N-port waveguide transition (geometry shown in Fig. 1) is based on the method of moments integral equation formulation for electric and magnetic currents induced on the surface of the patch array and slot apertures coupled to single-mode waveguides. The GSM of the transition is obtained for all propagating and evanescent T E and TM modes, taking into account a coupling of all ports. A rectangular waveguide taper (shown in Fig. l), approximated by double-plane stepped junctions, is analyzed using the mode-matching technique similar to [4]. The GSMs of waveguide tapers and N-port waveguide transitions are cascaded to obtain the overall response of the entire passive structure. Numerical results are presented for a single patch-to-slot waveguide transition, two cascaded waveguide-based patch-to-slot transitions (patch-slot-patch), and two cascaded 2 x 3 patch-to-slot arrays with rectangular waveguide tapers. Theory Consider the N-port waveguide transition (Fig. I), which contains a patch array SL at the interface Sd of adjacent dielectric layers with permittivities €1 and €2 in the overmoded waveguide (regions VI and Vz, respectively), slot apertures Si at the ground plane S,, and N-1 singlemode waveguides coupled to the patch array through an array of slots (regions Vj of the dielectric permittivity €3). A coupled set of integral equations is obtained by enforcing the boundary condition on the tangential components of the electric field on the conductive surfaces S& This work is supported by the U S . Army Research Office through Clemson University as a Multidisciplinary University Research Initiative on Quai-Optical Power Combining, Agreement Number DAAG55-97-K-0132. Sean Ortiz is also supported by a NSF Graduate Fellowship. 0-7803-6369-8/00/$10.0

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Cite this paper

@inproceedings{Oakar2004ElectromagneticMO, title={Electromagnetic Modeling of an Aperture-Coupled Patch Array in the N-Port Layered Waveguide for Spatial Power Combining Applications}, author={M R Oakar and Michael B. Steer}, year={2004} }