Adam Lamecki

Equivalent SPICE Circuits With Guaranteed Passivity From Nonpassive Models

In this paper, a new fast technique of passivity enforcement of a nonpassive rational model is introduced. The technique disturbs poles of the model to restore passivity in such way that the frequency response of a device being modeled is preserved. The passivity enforcement procedure is defined as an optimization routine with the gradients of the cost function evaluated using the theory of matrix perturbation. The rational model can be based either on passive (electromagnetic simulations, measurements) or nonpassive (surrogate models) data. In the second case, the proposed technique can lead to a parameterized SPICE networks. Some advanced examples are given to show the application of proposed approach in interconnect, packaging, and signal integrity analysis

A Memory Efficient and Fast Sparse Matrix Vector Product on a GPU

This paper proposes a new sparse matrix storage format which allows an e-cient implementation of a sparse matrix vector product on a Fermi Graphics Processing Unit (GPU). Unlike previous formats it has both low memory footprint and good throughput. The new format, which we call Sliced ELLR-T has been designed speciflcally for accelerating the iterative solution of a large sparse and complex-valued system of linear equations arising in computational electromagnetics. Numerical tests have shown that the performance of the new implementation reaches 69 GFLOPS in complex single precision arithmetic. Compared to the optimized six core Central Processing Unit (CPU) (Intel Xeon 5680) this performance implies a speedup by a factor of six. In terms of speed the new format is as fast as the best format published so far and at the same time it does not introduce redundant zero elements which have to be stored to ensure fast memory access. Compared to previously published solutions, signiflcantly larger problems can be handled using low cost commodity GPUs with limited amount of on-board memory.

Efficient implementation of the Cauchy method for automated CAD-model construction

An efficient and stable implementation of the multidimensional Cauchy method for creating high quality multivariate models of microwave circuits from electromagnetic (EM) simulation data is presented in this paper. The algorithm uses the total least squares method to solve the ill-conditioned interpolation problem and automatically determines the model order and distribution of support points in the parameter space in such a manner that instabilities are prevented. Numerical tests show that the method requires fewer support points to achieve similar accuracy as the rational function models published previously. The utility and accuracy of the technique is demonstrated on a filter design example involving three- and five-dimensional models.

Finite Element Matrix Generation on a GPU

This paper presents an e-cient technique for fast gener- ation of sparse systems of linear equations arising in computational electromagnetics in a flnite element method using higher order ele- ments. The proposed approach employs a graphics processing unit (GPU) for both numerical integration and matrix assembly. The per- formance results obtained on a test platform consisting of a Fermi GPU (1x Tesla C2075) and a CPU (2x twelve-core Opterons), indicate that the GPU implementation of the matrix generation allows one to achieve speedups by a factor of 81 and 19 over the optimized single- and multi-threaded CPU-only implementations, respectively.

GPU Acceleration of Multilevel Solvers for Analysis of Microwave Components With Finite Element Method

The letter discusses a fast implementation of the conjugate gradient iterative method with E-field multilevel preconditioner applied to solving real symmetric and sparse systems obtained with vector finite element method. In order to accelerate computations, a graphics processing unit (GPU) was used and significant speed-up (2.61 fold) was achieved comparing to a central processing unit (CPU) based approach. These results indicate that performance of electromagnetic simulations can be significantly improved thereby enabling full wave optimization of microwave components in more manageable time.

Coupled-Resonator Filters With Frequency-Dependent Couplings: Coupling Matrix Synthesis

This letter presents a novel technique for synthesis of coupled-resonator filters with inter-resonator couplings varying linearly with frequency. The values of non-zero elements of the coupling matrix are found by solving a nonlinear least squares problem involving eigenvalues of matrix pencils derived from the coupling matrix and reference zeros and poles of scattering parameters. The proposed method was verified by numerical tests carried out for various coupling schemes including triplets and quadruplets for which the frequency-dependent coupling was found to produce an extra zero.

Tuning a Hybrid GPU-CPU V-Cycle Multilevel Preconditioner for Solving Large Real and Complex Systems of FEM Equations

This letter presents techniques for tuning an accelerated preconditioned conjugate gradient solver with a multilevel preconditioner. The solver is optimized for a fast solution of sparse systems of equations arising in computational electromagnetics in a finite element method using higher-order elements. The goal of the tuning is to increase the throughput while at the same time reducing the memory requirements in order to allow one to process very large complex or real systems in single and double precision using commodity graphic processing units (GPUs). A threefold memory footprint reduction is achieved by means of a new format of storing sparse matrices. The acceleration is achieved by optimizing a sparse matrix-vector product on a GPU by applying new features of the Fermi architecture. Further improvements are obtained by introducing more levels into the preconditioner and the application of a fast sparse direct solver for the operations executed on a CPU. Numerical results for a setup consisting of a Fermi GPU (GTX 480) and a Xeon six-core CPU showed that the proposed approach allows one to handle systems involving millions of unknowns and reach the speedup factor of almost 4 compared to the CPU-only implementation.

A Substrate Integrated Waveguide (SIW) Bandpass Filter in A Box Configuration With Frequency-Dependent Coupling

This letter presents the design of a microwave bandpass filter with frequency-dependent coupling implemented in substrate integrated waveguide (SIW) technology. The proposed filter implements a four-pole generalized Chebyshev filtering function with two transmission zeros. Resonators are arranged in an extended box configuration with dispersive coupling on a main signal path, which produces an extra zero in comparison to classical approaches. The frequency-dependent coupling is implemented as a shorted stub with an additional septum made from via-holes. Such modification allows better control of the positions of the resonant frequencies of coupled SIW cavities, as well as of the position of the transmission zero. The filter was fabricated in SIW technology and good agreement was achieved between the simulated results and those measured.

Coupled-Resonator Waveguide Filter in Quadruplet Topology With Frequency-Dependent Coupling – A Design Based on Coupling Matrix

This letter presents an application of a recently developed coupling matrix synthesis technique to design of coupled-resonator filters with dispersive inter-resonator couplings. This technique is used to design a novel coupled-cavity bandpass filter. Measurements validate the design and confirm effectiveness of the synthesis method. The filter is a four-pole generalized Chebyshev filter with three transmission zeros. Resonators are arranged in a quadruplet configuration and employ a single dispersive cross coupling to produce an extra zero in comparison to classical approaches. Frequency-dependent coupling was realized via a rectangular waveguide iris with an incomplete height conducting post.

Design of Microwave Lossy Filter Based on Substrate Integrated Waveguide (SIW)

In this letter, we propose a lossy three-pole Chebyshev filter centered at 5.15 GHz, based on the substrate integrated waveguide (SIW) with scattering characteristics shifted down by 5.68 dB. The filter is composed of three directly coupled SIW cavities with three lossy couplings between nonadjacent resonators. These additional couplings are realized using mixed coupled slot and microstrip lines connected with metal electrode leadless face (MELF) resistors. The filter was fabricated using a standard printed circuit board (PCB) process, and good agreement between the simulated and measured results has been achieved.