Implicit Space Mapping Research Articles

A compact microstrip second‐order lossy bandpass filter with improved simplified composite right‐/left‐handed zeroth‐order resonator

AbstractA novel compact microstrip second‐order lossy bandpass filter (BPF) based on an improved simplified composite right‐/left‐handed zeroth‐order resonator (ISZOR) is presented in this paper. The microstrip ISZOR (MISZOR) features miniature topology and ample adjustable physical parameters accompanied by its easily controllable zeroth‐order base mode and first harmonic. Its layout can be quickly generated by applying the implicit space mapping technique. By virtue of the lossy coupling matrix synthesis method, the finite unloaded quality factor of the MISZOR can be taken into account in advance to foretell the insertion loss level. A new definition of the external quality factor as well as its full‐wave extraction method is introduced, enabling the targetted second‐order lossy BPF to be directly implemented as in the classical lossless design, despite the existence of the parallel resistor loaded nonresonant node at each terminal. A succinct inductive coupled microstrip corner is conceived to achieve the relatively strong terminal coupling strength. The exemplified lossy BPF centers at 3.1 GHz with a fractional bandwidth of 5%, which is automatically optimized with the Nelder–Mead simplex algorithm. A prototype measurement is carried out, and good agreement is achieved with simulation, testifying the proposed design concept.

A Rapid Matching Network Layout Synthesis and Optimization Method for High-Performance MMIC PAs Using Modified Implicit Space Mapping

In this brief, a new systematic approach of matching network (MN) layout synthesis and optimization for power amplifiers (PAs) is proposed based on implicit space mapping (ISM). Commonly, the performance discrepancy between schematic and initial layout is huge, especially for millimeter wave (mmWave) PAs. To address this issue, the proposed modified ISM can shift the optimization work to the circuit schematic simulations by calibrating carefully-selected auxiliary parameters in the circuit based on EM data. To validate the proposed method, an eligible dual-band inter-stage MN layout is rapidly optimized with only 10 runs of EM-simulations, while a corresponding 16/26.5 GHz concurrent dual-band PA is implemented in a 0.15- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> GaAs pHEMT technology. It exhibits a measured small-signal gain of 21.7/14.1 dB, peak power-added efficiency of 30.2%/40.5%, and saturated output power of 24.8/28.1 dBm with a compact chip size of 2.4 mm2.

An improved simplified composite right‐/left‐handed zeroth‐order resonator and its application to design a compact microstrip bandpass filter with enhanced upper stopband

AbstractAn improved simplified composite right‐/left‐handed (SCRLH) zeroth‐order resonator (ISZOR) is introduced, comprising two lateral parallel capacitors and a centred T‐type inductor circuit. Starting from the lumped circuit of the ISZOR, its miniature microstrip layout can be generated with on more than three times full‐wave simulations by virtue of the implicit space mapping technique. Multi‐solutions of the microstrip ISZOR with identical fundamental mode are obtained by sweeping key physical and electrical parameters, uncovering the relationship among physical sizes, resonant modes, unloaded quality factors and circuit elements. A three‐pole microstrip Chebyshev bandpass filter (BPF) with ultra‐wide upper stopband is further designed. By choosing the constituent ISZORs with identical base frequency but different higher resonant frequencies and applying the over‐coupled I/O terminals, wideband spurious response suppression in the upper stopband is achieved. The target BPF centers at 3.1 GHz with a relatively bandwidth of 5%, which is optimised through a customised aggressive space mapping iterative process. The optimal BPF layout dimensions are automatically obtained with just a few time‐consuming full‐wave simulations. A prototype measurement shows the BPF features good bandpass selectivity in a simple and easy‐to‐fabricate structure, with a transversal size reduction of more than 65% compared to a former counterpart and a rejection level better than 15 dB over 40.0 GHz.

Improved SCRLH ZOR‐based compact microstrip bandpass filter with wide upper stopband

AbstractA novel compact microstrip bandpass filter (BPF) based on an improved simplified composite right‐/left‐handed (SCRLH) zeroth‐order resonator (ZOR) is presented in this paper. The improved SCRLH ZOR (ISZOR) can substantially simplify the filter configuration and shrink the filter size as well as ensure a wide upper stopband. A certain orientation of two ISZORs allows a larger gap to produce the specified interstage capacitive coupling, easing the requirement for fabrication precision. Starting from the purely lumped circuit model, the microstrip ISZOR is efficiently generated by utilizing the implicit space mapping technique, with which the microstrip BPF is then constructed and optimized by the Nelder–Mead simplex algorithm. A three‐pole filter with a center frequency of 3.1 GHz and a relative bandwidth of 5% is exemplified to illustrate the design process. The measurement shows that the filter is of good bandpass selectivity, with a transversal size reduction of more than 64% compared to a former counterpart and a rejection level better than 30 dB up to 11.76 GHz (close to 4f0).

Implicit Space Mapping for Variable-Fidelity EM-Driven Design of Compact Circuits

Space mapping (SM) belongs to the most successful surrogate-based optimization (SBO) methods in microwave engineering. Among available SM variations, implicit SM (ISM) is particularly attractive due to its simplicity and separation of extractable surrogate model parameters and design variables of the circuit/system at hand. Unlike other SM approaches, ISM exploits a set of preassigned parameters to align the surrogate with the high-fidelity EM model. However, application of ISM is challenging if equivalent network model of the structure is unavailable or of poor quality. In this letter, a modified ISM that exploits variable-fidelity EM simulation models is proposed. Here, preassigned parameters are introduced in the coarsely discretized EM surrogate by dividing the substrate below selected components of the structure into segments with different permittivity and common thickness. The proposed method has been verified (also experimentally) using a rat-race coupler and favorably compared with state-of-the-art SBO methods.

Design and Optimization of SIW Center-Fed Series Rectangular Dielectric Resonator Antenna Array With 45° Linear Polarization

The modeling, design, and optimization of a new substrate integrated waveguide middle-fed series rectangular dielectric resonator antenna array with 45° linear polarization are presented. The implicit space mapping technique is applied for the optimization of the antenna array. A tunable circuit model is built, which serves as the coarse/surrogate mode, and a full-wave solver is used as the fine model. High design and optimization efficiency is demonstrated using an eight-element array. The reflection coefficient of the array antenna is optimized with only two iterations. The experimental data for the eight elements antenna array, operating at the millimeter-wave band (34–36 GHz), are used for the validation of both performance of the design and modeling techniques. The measured radiation pattern demonstrates a broadside beam with a maximum radiated gain of 13.55 dB over an operating impedance bandwidth of 2.2 GHz.

Reliable low‐cost surrogate modeling and design optimisation of antennas using implicit space mapping with substrate segmentation

In this work, a reliable methodology for fast simulation-driven design optimisation of antenna structures is proposed. The authors' approach exploits implicit space mapping (ISM) technology. To adopt it for handling antenna structures, they introduce substrate segmentation with separate dielectric permittivity value assigned for each segment as ISM preassigned parameters. At the same time, the coarse model for space mapping is established by reducing discretisation level of the EM analysis of the antenna structure at hand. Further, the proposed approach is generalised to permit execution of ISM in case of dielectric resonator antennas (DRAs), which is realised by segmentation of the DR and appropriate assignment of permittivity values. The discussed methodology is demonstrated through optimisation of a bandwidth-enhanced patch antenna and a triangular DRA. Comparison with state-of-the-art surrogate-assisted design methods, here, frequency and output space mapping, as well as conventional optimisation using pattern search, is also provided.

Rapid Simulation-Driven Multiobjective Design Optimization of Decomposable Compact Microwave Passives

In this paper, a methodology for fast multiobjective optimization of the miniaturized microwave passives has been presented. Our approach is applicable to circuits that can be decomposed into individual cells [e.g., compact microstrip resonant cells (CMRCs)]. The structures are individually modeled using their corresponding equivalent circuits and aligned with their accurate, EM simulated representations, by means of implicit space mapping (ISM). The ISM-corrected cells are then assembled into the entire structures and their Pareto-optimal solutions (here, representing the best possible tradeoffs between the structure size and electrical performance) are obtained using evolutionary methods. The refinement is then carried out for the selected structure realizations using, again, SM. The latter stage is necessary, because the cell-based equivalent circuit models do not account for EM cross-couplings between the cells. The proposed methodology allows for rapid identification of compromise geometries concerning size-performance tradeoffs and, more importantly, permits quality comparison of particular CMRC realizations from the point of view of their suitability for a given compact circuit implementation. Our approach is demonstrated using several variations of the three-section wideband impedance matching transformers consisting of two types of CMRC structures. Numerical validation of the results is provided.

On the low-cost design of abbreviated multisection planar matching transformer

A numerically demanding wideband matching transformer composed of three nonuniform transmission lines (NUTLs) has been designed and optimized at a low computational cost. The computational feasibility of the design has been acquired through the exploitation of low-fidelity NUTL models in most steps of the design procedure and an implicit space mapping optimization engine, providing high accuracy results with only a handful of EM simulations. The final design offers an enhanced functionality, that is, a 42% length diminution and has been acquired at the total cost of 12 EM evaluations of the entire structure. The method proposed has been experimentally validated, showcasing its usefulness for numerically demanding design problems of microwave circuits with complex topologies. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:521–525, 2015

A robust design of a numerically demanding compact rat‐race coupler

ABSTRACTA fast and accurate design procedure of a computationally expensive microwave circuit has been presented step‐by‐step and experimentally validated on the basis of a compact rat‐race coupler (RRC) comprising slow‐wave resonant structures. The final compact RRC solution has been obtained by means of a sequential optimization scheme exploiting the implicit space mapping algorithm. A well‐suited surrogate optimization starting point as well as a considerable limitation of the surrogate optimization variables contribute significantly to the numerical efficiency of the method proposed. The final design, offering 85% size reduction together with a satisfactory performance, has been obtained with only a handful of EM simulations. The experimental validation of the method has been successfully conducted. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1259–1263, 2014

A simple method to design dielectric resonator-based filters and diplexers using implicit space mapping technique

We present the design of a six pole Chebyshev filter and a cascaded quadruple dielectric resonator DR filter using space mapping technique. Implicit space mapping technique is used throughout and the design emerges within few iterations in both the cases. Finite element method based HFSS is used in constructing the fine model and Agilent ADS is used in constructing the coarse model. Fine details such as tuning screws are included in the fine model. The same technique is also applied to a DR-based diplexer and is explained. In all the cases, the results obtained with the hardware match well with the analyzed results. The same procedure can be applied in designing much more complex structures such as multiplexers. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:204-216, 2014.

Application of Implicit Space Mapping in Aid of Design of Sub-harmonic Mixer with CMRC Filter

In recent years, the CMRC filter has been an attractive candidate for use in mixer and frequency multiplier circuits to improve the performance due to its low-insertion loss, sharp rejection, shorter size and wider stop-band. However, complex structures, too much variables and inefficient design method hindered its widespread use. In this study, we report on the application of the implicit space mapping algorithm in design of CMRC filter to greatly improve the design efficiency. Finally, a mixer with CMRC filter is designed and fabricated based on Rogers substrate process. The measured performance of this mixer is sufficient for engineering applications.

New approach to a fast and accurate design of microwave circuits with complex topologies

A robust simulation-driven design methodology of microwave circuits with complex topologies has been presented. The general method elaborated is suitable for a wide class of N-port unconventional microwave circuits constructed as a deviation from classic design solutions. The key idea of the approach proposed lies in an iterative redesign of a conventional circuit by a sequential modification and optimisation of its atomic building blocks. The speed and accuracy of the method presented has been acquired by solving a number of simple optimisation problems through surrogate-based optimisation (SBO) techniques, which offer a satisfactory approximation of the optimal design solution. Two exemplary designs have been supplied to verify the method introduced. An abbreviated wideband quarter-wave impedance matching transformer and a miniaturised hybrid branch–line coupler have been developed. Diminished dimensions of the circuits under construction have been achieved by means of compact microstrip resonant cells. As an SBO engine, an implicit space mapping technique has been utilised. The final results have been acquired in only a fraction of time that is necessary for a direct electromagnetic (EM) optimisation to generate competitive results. An experimental validation of the method proving its high utility has been provided.

A New Implicit Space Mapping with High Convergence for Microwave Filter Design

A New Implicit Space Mapping with High Convergence for Microwave Filter Design

IMPLICIT SPACE MAPPING APPLIED TO THE SYNTHESIS OF ANTENNA ARRAYS

This paper introduces a novel technique for efficiently combining implicit space mapping (ISM) with method of moments (MoM) for the synthesis of antenna arrays and explores several example applications of the ISM approach. The antenna arrays geometric parameters are extracted to be optimized by ISM, and a fitness function is evaluated by MoM simulations to represent the performance of each candidate design. A coarse-mesh MoM and a fine-mesh MoM solver are used for the coarse and the fine models, respectively. To achieve the parameter extraction, the auxiliary parameter is selected and the approximation between the two models is accomplished by particle swarm optimization (PSO). The results show that the running time of the ISM algorithm is 2 ∼ 3 times faster than that of other optimization algorithms (e.g., PSO).

Implicit space mapping with adaptive selection of preassigned parameters

Implicit space mapping is one of the latest developments in space mapping (SM) technology. Its advantage is that the variables (the so-called preassigned parameters) used to adjust the surrogate model to have it match the fine model are typically separate from the design variables. Also, implicit space mapping offers greater flexibility in creating and enhancing surrogate models. Still, choosing the proper model as well as the right set of preassigned parameters - both being critical for the performance of the space mapping algorithm - is an open problem. Here, the authors apply suitable assessment techniques that help in automatically making the right selection of the model and, consequently, its associated parameters. The assessment is embedded into the SM algorithm so that the choice of the most suitable model is performed before each iteration of the algorithm. Our approach is verified using several microwave design optimisation problems. The authors also present a modified version of the adaptive SM to improve performance. Our examples are repeated using the modified adaptive SM and compared with the basic adaptive SM.

Space Mapping Design Framework Exploiting Tuning Elements

Inspired by the ideas of ¿simulator-based¿ tuning, implicit space mapping, and surrogate optimization, we propose an implementable microwave design framework. In this framework, we alter an electromagnetic (EM) model by embedding suitable tuning elements. The resulting tuning model is aligned with the original unaltered EM model. We then designate the aligned tuning model as surrogate for design optimization purposes. We illustrate our tuning space mapping framework using a simple microstrip line example. Several microwave examples, including a low-temperature co-fired ceramic filter demonstrate the framework's implementation and robustness.

Microstrip Low-Pass Elliptic Filter Design Based on Implicit Space Mapping Optimization

It is a time-consuming and often iterative procedure to determine design parameters based on fine, accurate but expensive, models. To decrease the number of fine model evaluations, space mapping techniques may be employed. In this approach, it is assumed both fine model and coarse, fast but inaccurate, one are available. First, the coarse model is optimized to obtain design parameters satisfying design objectives. Next, auxiliary parameters are calibrated to match coarse and fine models’ responses. Then, the improved coarse model is re-optimized to obtain new design parameters. The design procedure is stopped when a satisfactory solution is reached. In this paper, an implicit space mapping method is used to design a microstrip low-pass elliptic filter. Simulation results show that only two fine model evaluations are sufficient to get satisfactory results.

Space mapping

In this article we review state-of-the-art concepts of space mapping and place them con- textually into the history of design optimization and modeling of microwave circuits. We formulate a generic space-mapping optimization algorithm, explain it step-by-step using a simple microstrip filter example, and then demonstrate its robustness through the fast design of an interdigital filter. Selected topics of space mapping are discussed, including implicit space mapping, gradient-based space mapping, the optimal choice of surrogate model, and tuning space mapping. We consider the application of space mapping to the modeling of microwave structures. We also discuss a software package for automated space-mapping optimization that involves both electromagnetic (EM) and circuit simulators.

Combining Coarse and Fine Models for Optimal Design

In this article we reviewed the implicit space mapping concept. We illustrated it using a simple tapped-line microstrip filter example. We demonstrated the robustness of our approach by performing an accurate design of a microstrip hairpin filter. A detailed and easy-to-follow design optimization procedure was provided and the Agilent ADS implementation of the algorithm was described. A good electromagnetically validated design in Sonnet em was obtained in a few fine model simulations. Implicit space mapping is a simple approach to combine a circuit-theory based CAD model and an EM simulator model to achieve fast and accurate optimal design and modeling.