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

Abstract

A 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.

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

“…Figure 1 shows the MISZOR layout and its lumped circuit model, in which the low‐impedance line with width $${w}_{1}$$ and the high‐impedance line with width $${w}_{2}$$ correspond to $${C}_{{\rm{R}}}$$ and $${L}_{{\rm{R}}}$$, respectively, while the short‐circuited stub with length $${l}_{3}$$ is equivalent to $${L}_{{\rm{L}}}$$. Figure 1C shows its typical dispersion characteristics extracted from the periodic Bloch theory, 13 in which $${\beta }_{s}$$ is the propagation constant, $$p$$ is the physical length of a single unit cell, resulting in $${\beta }_{s}p$$ the dispersive phase shift and $${R}_{{\rm{B}}}$$ is the real part of the Bloch impedance. $${\omega }_{{\rm{e}}}$$ (full circle) is the zeroth‐order frequency, where $${\beta }_{s}p={0}^{\circ }$$, and $${\omega }_{{\rm{o}}}$$ (empty circle) is the Bragg frequency, where $${\beta }_{s}p={180}^{\circ }$$.…”

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

“…The unconstrained Nelder-Mead simplex algorithm (fminsearch in Matlab) is chosen as the optimization engine, and resorting to the HFSS VBScript programming, the optimization at this stage can be carried out in a fully automatic way. 12 The fitness function is the absolute error between the objective coupling coefficients and those extracted with the extraction method in Meng and Wu. 13 A personal computer with Intel I7-4790K CPU and 32 GB RAM was used as the computing platform.…”

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

“…Finally, the whole ISZOR-based BPF is optimised by a customised aggressive space mapping (ASM) maneuver, where the coarse model (CM) is the coupled matrix extracted from the full-wave simulated S parameters [17], and the fine model (FM) is the time-consuming full-wave simulation. The ASM iterative process is fully automatic without any need of the artificial intervention, controlled by VBScripting codes executed in Matlab [18]. The finalised ISZOR-based BPF featuring good passband selectivity with observably expanded upper stopband is experimentally verified.…”