Mete Ozkar

Global coupled EM-electrical-thermal simulation and experimental validation for a spatial power combining MMIC array

The first fully coupled electromagnetic-electro-thermal global simulation of a large microwave subsystem, here a whole spatial power combining MMIC array, is described. The modeling effort is supported by parallel developments in electro-optic and thermal measurement. The CAD tools and experimental characterisation described, provide a unique capability for the design of quasi-optical systems and for the exploration of the fundamental physics of spatial power combining devices.

A waveguide-based aperture-coupled patch amplifier array-full-wave system analysis and experimental validation

In this paper, the full-wave analysis and experimental verification of a waveguide-based aperture-coupled patch amplifier array are presented. The spatial power-combining amplifier array is modeled by the decomposition of the entire system into several electromagnetically coupled modules. This includes a method of moments integral equation formulation of the generalized scattering matrix (GSM) for an N-port waveguide-based patch-to-slot transition; a mode-matching analysis of the GSM for the receiving and transmitting rectangular waveguide tapers; and a finite-element analysis of the waveguide-to-microstrip line junctions. An overall response of the system is obtained by cascading GSMs of electromagnetic structures and the S-parameters of amplifier networks. Numerical and experimental results are presented for the single unit cell and 2/spl times/3 amplifier array operating at X-band. The results are shown for the rectangular aperture-coupled patch array, although the analysis is applicable to structures with arbitrarily shaped planar electric and magnetic surfaces.

State-variable-based transient analysis using convolution

A state-variable-based approach to the impulse response and convolution analysis of distributed microwave circuits is developed. The state-variable approach minimizes computation time and memory requirements. It allows the use of parameterized nonlinear device models, thus improving robustness. Soliton generation on a nonlinear transmission line is considered as an example.

Electromagnetic modeling and optimization of spatial power combiners/dividers with hard horns

A generalized scattering matrix (GSM) approach, which utilizes finite-difference time-domain (FDTD) with a modified unsplit PML (perfectly matched layer) and mode matching techniques, is used to analyze spatial power combiners/dividers with hard horn feeds. The simulation results are experimentally verified for a 1:9 spatial power dividing system. Furthermore, the effects of various design parameters on the overall performance of a 1:9 divider is investigated.

Fault tolerance analysis and measurement of a spatial power amplifier

The performance degradation due to device failures in a spatial power combining system is presented in this paper, including analysis and measurement. For this study, a 5/spl times/5 amplifier array, employing 17 dBm (P1 dB) MMIC amplifiers, has been designed and tested. Individual unit cells have been turned off in order to represent a system with device failures. Results for both simulated and measured array performance versus device failures are given.

Analysis and design of an inhomogeneous transformer with hard wall waveguide sections

A new inhomogeneous waveguide transformer with hard walls is presented. Mode matching technique along with an optimization routine is used to design the transformer. The generalized scattering matrix (GSM) of the whole block is calculated which can be used to predict the fields at the output given the incident excitations. An example of a three-section transformer, which replaces a tapered hard horn, is shown. The transformer has better performance in the bandwidth of interest compared to the tapered hard horn having twice the length of the transformer. This type of transformer could be useful for excitation of quasi-optical amplifiers and reflector feeds.

A modified unsplit PML formulation for evanescent mode absorption in waveguides

In this letter, a modified unsplit perfectly matched layer (PML) formulation for the absorption of evanescent waves in waveguides is presented. The proposed formulation combines the advantages of the stretched coordinate and unsplit D - E - H PML formulations, which separates PML conductivities from the properties of the physical materials in the FDTD mesh. Results show that the proposed boundary outperforms the traditional unsplit PML in the evanescent region by 20 to 40 dB.

Electromagnetic modeling of an aperture-coupled patch array in the N-port layered waveguide for spatial power combining applications

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 to a matrix system resulting in the generalized scattering matrix (GSM) for the N-port 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.

Circuit level modelling of spatially distributed mm and sub mm-wave systems

Modelling of millimeter-wave and submillimeter-wave systems have generally been developed from a circuit perspective with the effect of the electromagnetic environment modeled essentially as lumped elements. Recent developments in steady-state and transient analyses integrating circuit and electromagnetic modeling are presented.

Numerical and experimental investigation of losses in a tray based spatial power amplifier

This paper presents experimental and numerical investigations on a 49-element Ka-band amplifier array. This study is aimed at determining the origin of various losses in the amplifier array. Passive simulation data confirms that the load seen by the active devices is well matched and that most of the power is coupled to the LSE/sub 10/ mode. This means that coherent power combining should take place if there is no phase and amplitude variation due to the active devices and phase correcting dielectric lenses.