Adrian Bekasiewicz

Efficient Multi-Objective Simulation-Driven Antenna Design Using Co-Kriging

A methodology for fast multi-objective antenna optimization is presented. Our approach is based on response surface approximation (RSA) modeling and variable-fidelity electromagnetic (EM) simulations. In the design process, a computationally cheap RSA surrogate model constructed from sampled coarse-discretization EM antenna simulations is optimized using a multi-objective evolutionary algorithm. The initially determined Pareto optimal set representing the best possible trade-offs between conflicting design objectives is then iteratively refined. In each iteration, a limited number of high-fidelity EM model responses are incorporated into the RSA model using co-kriging. The enhanced RSA model is subsequently re-optimized to yield the refined Pareto set. Combination of low- and high-fidelity simulations as well as co-kriging results in the low overall optimization cost. The proposed approach is validated using two UWB antenna examples.

Structure and Computationally Efficient Simulation-Driven Design of Compact UWB Monopole Antenna

In this letter, a structure of a small ultra-wideband (UWB) monopole antenna, its design optimization procedure as well as experimental validation are presented. According to our approach, antenna compactness is achieved by means of a meander line for current path enlargement as well as the two parameterized slits providing additional degrees of freedom that help to ensure good impedance matching. For the sake of reliability, the antenna design process (simultaneous adjustment of multiple geometry parameters) is carried out using high-fidelity EM analyses. Surrogate-based optimization involving an auxiliary coarse-discretization EM model it utilized to accomplish the design in practical timeframe. Penalty function approach allows us to reduce the antenna footprint (to only 15.8 × 22 mm2) while maintaining acceptable reflection in the UWB frequency range. Experimental validation of the design is also provided.

Fast EM-Driven Size Reduction of Antenna Structures by Means of Adjoint Sensitivities and Trust Regions

In this letter, a simple yet robust and computationally efficient optimization technique for explicit size reduction of antenna structures is presented. Our approach directly handles the antenna size as the main design objective, while ensuring satisfactory electrical performance by means of suitably defined penalty functions. For the sake of accuracy, the antenna structure is evaluated using high-fidelity EM simulation. In order to maintain computational efficiency of the design optimization process, it is carried out using cheap adjoint sensitivities and trust region framework utilized as convergence safeguard. Our technique is illustrated through a design of a compact quasi-isotropic dielectric resonator antenna and a UWB monopole. Numerical results are supported by physical measurements of a fabricated prototype.

Expedited EM-Driven Multiobjective Antenna Design in Highly Dimensional Parameter Spaces

A technique for low-cost multiobjective optimization of antennas in highly dimensional parameter spaces is presented. The optimization procedure is expedited by exploiting fast surrogate models, including coarse-discretization electromagnetic (EM) antenna simulations and response surface approximations (RSA). The latter is utilized to yield an initial set of Pareto nondominated designs that are further refined using response correction methods. Efficient handling of multiple geometry parameters is realized by the initial reduction of the solution space. Our approach is demonstrated using a 13-parameter triple trapezoidal, planar ultrawideband (UWB) monopole antenna.

Rapid EM-Driven Design of Compact RF Circuits By Means of Nested Space Mapping

A methodology for rapid design of RF circuits constituted by compact microstrip resonant-cells (CMRCs) is presented. Our approach exploits nested space mapping (NSM) technology, where the inner SM layer is used to correct the equivalent circuit model at the CMRC level, whereas the outer layer enhances the coarse model of the entire structure under design. We demonstrate that NSM dramatically improves performance of surrogate-based optimization of composite CMRC-based structures. It is validated using four examples of UWB microstrip matching transformers (MTs) and compared to previous attempts to surrogate-based compact structure design.

Fast Multiobjective Optimization of Narrowband Antennas Using RSA Models and Design Space Reduction

A computationally efficient technique for multiobjective design optimization of narrowband antennas is presented. In our approach, the corrected low-fidelity antenna model [obtained through coarse-discretization electromagnetic (EM) simulations] is enhanced using frequency scaling and response correction, sampled, and utilized to obtain a fast response surface approximation (RSA) antenna surrogate. The RSA model is constructed in the reduced design space. The initial set of Pareto-optimal designs is then utilized to confine the design space further by identifying designs that satisfy minimum requirements with respect to antenna reflection response. The updated RSA model set up in the confined space is subsequently optimized to yield the final Pareto set at the low computational cost.

Rapid Multi-Objective Simulation-Driven Design of Compact Microwave Circuits

A methodology for rapid multi-objective design of compact microwave circuits is proposed. Our approach exploits point-by-point Pareto set identification using surrogate-based optimization techniques, auxiliary equivalent circuit models, and space mapping as the major model correction method. The proposed technique is illustrated and validated through the design of a compact rat-race coupler. A set of ten designs being trade-offs between electrical performance of the structure and its size (layout area) is obtained at the cost corresponding to less than thirty high-fidelity EM simulations of the circuit. Experimental verification of three selected designs is provided.

Design of a Planar UWB Dipole Antenna With an Integrated Balun Using Surrogate-Based Optimization

A design of an ultrawideband (UWB) antenna with an integrated balun is presented. A fully planar balun configuration interfacing the microstrip input of the structure to the coplanar stripline (CPS) input of the dipole antenna is introduced. The electromagnetic (EM) model of the structure of interest includes the dipole, the balun, and the microstrip input to account for coupling and radiation effects over the UWB band. The EM model is then adjusted for low reflection over the UWB band by means of fast simulation-driven surrogate-based optimization. This approach allows us to obtain the final design at low computational costs and at a high-fidelity level of structure description. Measurements of the manufactured optimal design validate the use of the balun as well as the design approach.

Multiobjective Antenna Design By Means of Sequential Domain Patching

A simple yet robust methodology for rapid multiobjective design optimization of antenna structures has been presented. The key component of our approach is sequential domain patching of the design space, which is a stencil-based search that aims at creating a path that connects the extreme Pareto-optimal designs, obtained by means of single-objective optimization runs. The patching process yields the initial approximation of the Pareto set representing the best possible tradeoffs between conflicting design objectives. It is realized-for the sake of computational efficiency-at the level of coarse-discretization electromagnetic (EM) simulation model. The final Pareto front is subsequently obtained using surrogate-assisted optimization where the EM simulation data acquired at the initial design stage is reused.

A Structure and Simulation-Driven Design of Compact CPW-Fed UWB Antenna

In this letter, a structure of a miniaturized ultrawideband (UWB) coplanar waveguide (CPW)-fed antenna and its design procedure are presented. The antenna is a modified version of the design previously proposed in the literature, with additional degrees of freedom introduced in order to improve the structure flexibility. The small size is achieved by executing a rigorous optimization procedure that consists of two stages: 1) smart random search carried out at the level of coarse-mesh electromagnetic (EM) simulation model that aims at finding an initial design featuring small size and reasonable return loss, and 2) surrogate-assisted optimization exploiting variable-fidelity EM simulations and response correction techniques for expedited design tuning. The final design exhibits return loss below - 13.2 dB in the entire UWB band and a small size of 418 mm2. Simulation results are supported by physical measurements of the fabricated antenna prototype.