Aggressive Space Mapping Optimization Research Articles

Automated design for a hybrid lumped and distributed dual‐band stub using aggressive space mapping

AbstractA dual‐band stub (DBS) in a hybrid lumped and distributed configuration is presented in this paper, which comprises one lumped kernel circuit unit cell (KCUC) centered between two uniform transmission lines. Image parameter theory is imposed to extract the DBS phase and impedance bandwidth properties. An odd‐even mode resonant frequency ratio is defined, capable of determining all the DBS element values as well as regulating the DBS size and its second working bandwidth. By converting the lumped KCUC into a quasi‐lumped microstrip topology, a purely planar DBS is automatically implemented by employing the aggressive space mapping (ASM). Through the customized ASM process, the finalized DBS dimensions can be generated within just a few full‐wave simulations. The relatively high accuracy and efficiency of the ASM are affirmed by comparing its performance to those of the traditional direct optimization algorithms. As an example, a DBS with WLAN dual frequencies and extended bandwidth is designed and fabricated. The measured results agree well with the simulated results, justifying the DBS properties and its ad hoc ASM optimization technique.

Automated Design of Common-Mode Suppressed Balanced Wideband Bandpass Filters by Means of Aggressive Space Mapping

The automated and unattended design of balanced microstrip wideband bandpass filters by means of aggressive space mapping (ASM) optimization is reported in this paper. The proposed filters are based on multisection mirrored stepped impedance resonators (SIRs) coupled through quarter-wavelength transmission lines, acting as admittance inverters. Such resonant elements provide transmission zeros useful for the suppression of the common mode in the region of interest (differential filter pass band) and for the improvement of the differential-mode stopband (rejection level and selectivity). Due to the limited functionality of the inverters, related to the wide fractional bandwidths, the automated filter design requires a two-step process. With the first ASM, the filter schematic satisfying the required specifications (optimum filter schematic) is determined. Then, the layout is synthesized by means of a second ASM algorithm. Both algorithms are explained in detail and are applied to the synthesis of two filters, as illustrative (and representative) examples. With this paper, it is demonstrated that the two-step ASM optimization scheme (first providing the optimum schematic and then the layout), previously applied by the authors to wideband single-ended filters, can be extended (conveniently modified) to common-mode suppressed differential-mode bandpass filters. Thus, the value of this two-step ASM approach is enhanced by demonstrating its potential for the unattended design of complex filters, as those considered in this paper.

Efficient Design of Compact Contiguous-Channel SIW Multiplexers Using the Space-Mapping Method

A planar compact contiguous-channel substrate integrated waveguide (SIW) multiplexer (MUX) is proposed in this paper. To reduce the size of the MUX, the output channels are closely aligned to each other through the use of a compact SIW power combiner. To develop the proposed MUX with high efficiency and high accuracy, a systematic design procedure using an aggressive space-mapping (ASM) optimization algorithm is presented. The fine model established in the full-wave simulator HFSS, the coarse model established in the circuit simulator ADS, and the ASM optimization algorithm are combined in the design procedure, and circuit elements are determined through suitable parameter-extraction procedures. As demonstrations, a Ku-band SIW four-channel MUX prototype is designed and verified by experiments.

Design of Planar Wideband Bandpass Filters From Specifications Using a Two-Step Aggressive Space Mapping (ASM) Optimization Algorithm

This paper is focused on the automated and unattended optimization of a type of planar wideband bandpass filters by means of aggressive space mapping (ASM). The considered filters are microstrip filters implemented through a combination of shunt connected stepped impedance resonators (SIRs) and grounded stubs coupled through admittance inverters. The most relevant and novel aspect of this paper is the fact that the filter layout is automatically generated from filter specifications, i.e., central frequency, fractional bandwidth, in-band ripple and order, without the need of any external aid to the design process. To achieve this layout generation, filter optimization has been divided into two independent ASM processes. The first one generates the filter schematic (circuit element values) providing the required specifications. This first iterative process is necessary since, due to the narrow band operation of the admittance inverters, the target specifications are achieved by compensating the effects of such narrow band operation. The purpose of the second ASM algorithm is to automatically generate the layout from the filter schematic resulting from the first ASM process. To validate the new two-step ASM optimization tool, two sets of filter specifications (inputs of the developed tool), are considered. The generated filter layouts exhibit frequency responses that satisfy the specifications, and are in excellent agreement with the responses of the schematics.

Synthesis of Split-Rings-Based Artificial Transmission Lines Through a New Two-Step, Fast Converging, and Robust Aggressive Space Mapping (ASM) Algorithm

This paper is focused on the synthesis of artificial transmission lines based on complementary split ring resonators (CSRRs). The considered structures are microstrip lines with CSRRs etched in the ground plane and microstrip lines loaded with both CSRRs and series capacitive gaps. An aggressive space mapping (ASM) optimization algorithm, able to automatically generate the layout of these artificial lines, has been developed. The tool has been optimized in order to achieve fast convergence and to provide accurate results. The main relevant aspects of the proposed algorithm (based on a novel two-step ASM optimization approach) are: 1) the capability to provide the implementable circuit elements of the equivalent circuit model of the considered artificial lines and 2) the ability to converge in a few (unprecedented) iteration steps, due to a new procedure to generate the initial layouts (which are very close to the final ones). First, the software is tested through the synthesis of several CSRR-based microstrip lines, and then some practical application examples of such artificial lines are reported to illustrate the potential of the proposed synthesis tool.