Compact cell topology selection for size-reduction-oriented design of microstrip rat-race couplers

Abstract

In this work, we address the problem of compact cell topology selection for miniaturization of rat‐race couplers. The principal objective of the design process is to achieve the smallest possible footprint of the coupler, while maintaining the required levels of electrical parameters imposed on its components. Our approach permits identification of the minimum achievable coupler area, provided that the circuit is composed of a given compact cell and folded lines. This allows for the quantitative assessment of a set of considered cells with respect to the miniaturization capabilities they exhibit under certain design specifications. The proposed method is validated using 6 different cells with unified parameterization to identify the smallest rectangular‐like rat‐race coupler described by 2 design specifications. The obtained results attest that circuit topology and electrical parameters of the reference design are critical factors determining the final miniaturization rate. The proof‐of‐concept prototype devices occupy merely 8% of the conventional coupler area, while preserving fractional bandwidths (20% and 13.5%) of their conventional counterparts. The experimental results confirm the claims inferred from the numerical data.

Numerically efficient algorithm for compact microwave device optimization with flexible sensitivity updating scheme

“…S 41 correspond to the minima of | S 11 | and | S 41 |, respectively, whereas β j , j = 1, 2, 3, denote penalty coefficients. The formulation is a convenient way of handling computationally expensive constraints, commonly occurring in the optimization of EM simulation models …”

“…Nowadays, full‐wave electromagnetic (EM) analysis is a necessity in the design closure of microwave components and devices . This especially applies to miniaturized structures: due to significant cross‐coupling effects present in the densely arranged layouts, simplified representations (eg, equivalent networks) either cannot be relied on or simply do not exist . The examples of such structures include compact microstrip couplers, power dividers, impedance transformers, and filters .…”

A novel trust‐region–based algorithm with flexible Jacobian updates for expedited optimization of high‐frequency structures

“…S 41 refer to the frequencies of the minima of | S 11 | and | S 41 |, respectively, whereas σ k , k = 1, 2, 3, denote the penalty coefficients. The presented penalty function concept (cf ()) allows for efficient handling of the expensive constraints, particularly if both the objective function and the constraints come from EM simulation …”

“…EM simulation models can deliver an adequate level of performance evaluation accuracy . Furthermore, they are often the only way to ensure sufficient reliability, especially for topologically complex structures for which the existing theoretical models are highly inaccurate . Typically carried out as the last stage of the design process, EM‐driven parameter adjustment aims at the improvement of selected performance figures, such as impedance matching, bandwidth, gain, or achieving a required power split ratio, to name just a few.…”

Efficient Gradient-Based Algorithm with Numerical Derivatives for Expedited Optimization of Multi-Parameter Miniaturized Impedance Matching Transformers

“…Another issue pertinent to compact components is an increased number of geometry variables. For example, a typical compact microstrip resonant cells (CMRC) unit is described by five or more parameters versus two for the conventional transmission line (TL) it is replacing [15]. Similarly, miniaturized antennas may require as many as twenty to thirty parameters to describe their geometry versus just a few for basic topologies.…”