Microwave Circuit Design Research Articles

Review of RF and Microwave Circuit Design: Theory and Applications [Book/Software Reviews

<i>Review of</i> RF and Microwave Circuit Design: Theory and Applications [Book/Software Reviews

Frequency Shift in Microwave Circuits Manufactured with Circuit Board Plotters: Case Study of a Parallel Coupled Lines Filter

Board milling is one of the most widespread methods for manufacturing printed circuit boards from low frequencies to the microwave and millimeter wave range. In this contribution, the detrimental effect of defects typical of printed circuit board plotters has been investigated. In detail, a systematic frequency shift in the circuit performance has been observed both in terms of S21 and S11 parameters. The performance degradation has been analyzed and attributed to the inaccurate milling depth, which is typical of many plotters, particularly for less recent models. After the conductor removal step, the unwanted milling of dielectric material changes the electrical properties of the microstrip structure, in turn affecting the circuit performance. This circumstance has been investigated by means of electromagnetic simulations performed on the real case study of a parallel coupled lines filter. Therefore, a filter prototype has been realized and measured to confirm the simulated results. This study can be beneficial to those professionals involved in the design and realization of microwave and millimeter waves circuits with board milling machines.

Revolutionizing Microwave Circuit Design with Machine Learning: Challenges and Opportunities

Revolutionizing Microwave Circuit Design with Machine Learning: Challenges and Opportunities

A Review of Electromagnetics-Based Microwave Circuit Design Optimization

A Review of Electromagnetics-Based Microwave Circuit Design Optimization

Optimizing MMIC performance: The synergy of AI models and heterogeneous integration process

AbstractThis study presents a novel approach for optimizing the parameters of monolithic microwave integrated circuit (MMIC) functional units using machine‐learning techniques and multi‐objective optimization algorithms. We utilize advanced machine‐learning methods, including random forest, artificial neural networks (ANNs), and recurrent neural networks (RNNs), to construct highly accurate models that predict the performance of these units. These models are subsequently integrated with a multi‐objective optimization algorithm, specifically the multi‐objective particle swarm optimization (MOPSO), to generate inverse design solutions for both the geometric designs of the units and the fabrication parameters of the heterogeneous integration process. Our approach, which has been validated through chip fabrication and testing, has demonstrated its robustness as a tool for achieving optimal MMIC designs. It not only reduces the design time but also enhances the manufacturability of MMICs, thereby opening new avenues in microwave and RF circuit design.

Coplanar Waveguide (CPW) Loaded with Symmetric Circular and Polygonal Split-Ring Resonator (SRR) Shapes

This paper investigates the performance of coplanar waveguide (CPW) structures loaded with symmetric circular and polygonal split-ring resonators (SRRs) for microwave and RF applications, leveraging their unique electromagnetic properties. These properties make them suitable for metamaterials, sensors, filters, resonators, antennas, and communication systems. The objectives of this study are to analyze the impact of different SRR shapes on the transmission characteristics of CPWs and to explore their potential for realizing compact and efficient microwave components. The CPW-SRR structures are fabricated on a dielectric substrate, and their transmission properties and spectrogram are experimentally characterized in the frequency range of 4 GHz to 10 GHz with the rotation angles of the SRR gap. The simulation results demonstrate that the resonant frequencies and magnitude of the transmission coefficient of the CPW-SRR structures are influenced by the geometry of the SRR shapes and the rotation angles of the SRR gap, with certain shapes exhibiting enhanced performance characteristics compared to others. Moreover, the symmetric circular and polygonal SRRs offer design flexibility and enable the realization of miniaturized microwave components with improved performance metrics. Overall, this study provides valuable insights into the design and optimization of CPW-based microwave circuits utilizing symmetric SRR shapes, paving the way for advancements in the miniaturization and integration of RF systems.

Development of a New Equivalent Circuit of DGS with Ideal Transformer

In this paper, a new equivalent circuit of a rectangular dumbbell‐shaped defected ground structure (DGS) with an ideal transformer is proposed. The proposed circuit incorporates a parallel resistor in the DGS gap, enabling the extraction of the coupling coefficient of DGS occurring in the narrow line gaps. Both circuit simulations and measurements demonstrate excellent agreement, confirming excellent performance compared to the measured results. Unlike the conventional equivalent circuit, which consists only of the lumped element, this one has an accuracy of only DGS units. In the proposed circuit, an ideal transformer has higher accuracy for the DGS in parallel with a resistor. We observed that increasing the resistance of the parallel resistor on the DGS unit leads to a decrease in the coupling coefficient and, conversely, decreasing the resistance prompts an increase in the coupling coefficient. The goal of this study is to develop a new equivalent circuit for a DGS unit with the ideal transformer, especially to find the coupling coefficient that occurred in the DGS gap. Here, we analyzed that the structure of the DGS unit had a gap, and the coupling coefficient must be built into any value. To demonstrate the effectiveness of the proposed circuit, DGS was used to design and conduct fabrication and measurement. The advantages of the proposed circuit analysis of the DGS behavior can be used to develop the attenuation pole as a one‐pole low‐pass filter, paving the way for future applications and developments in microwave and RF circuit design.

Compact Microwave Circuit Design With Short Wavelength on Via-Guided Microstrip Lines

Compact Microwave Circuit Design With Short Wavelength on Via-Guided Microstrip Lines

Calibrated microwave reflectance in low-temperature scanning tunneling microscopy.

We outline calibrated measurements of the microwave reflection coefficient from the tunnel junction of an ultra-high vacuum low temperature scanning tunneling microscope. The microwave circuit design is described in detail, including an interferometer for an enhanced signal-to-noise ratio and a demodulation scheme for lock-in detection. A quantitative, in situ procedure for impedance calibration based on the numerical three-error-term model is presented. Our procedure exploits the response of the microwave reflection signal due to the change of the tunneling conductance caused by sub-nm variation of the tunneling distance. Experimental calibration is achieved by a least-squares numerical fit of simultaneously measured conductance and microwave reflection retraction curves at finite conductance. Our method paves the way for nanoscale microscopy and spectroscopy of dielectric surface properties at GHz frequencies and cryogenic temperatures. This opens a promising pathway even for dielectric fingerprinting at the single molecule limit.

Bio-inspired intelligence for minimizing losses in substrate integrated waveguide

This paper presents a study of various types of losses in substrate-integrated waveguides (SIW) using a genetic algorithm. Three main types of losses are considered and examined separately: conductor loss, dielectric loss, and radiation loss. Furthermore, the current analysis allows for a physical understanding of the loss impacts as well as the creation of design guidelines to reduce losses at 10 GHz frequency while keeping the miniaturized size of the SIW. Validation results obtained using the software Ansys HFSS, verify that the attenuation constant of the SIW can be significantly reduced to 0.4 dB/m, the Insertion loss S21 to -0.2 dB and the return loss to -38 dB if the geometric parameters are chosen properly. This study enables us to identify the source of losses in a SIW and, as a result, eliminate any type of dispersion. That demonstrates the usability of SIW technologies in the design of microwave circuits used in Internet of things applications.

An Early History of Optimization Technology for Automated Design of Microwave Circuits

This paper outlines the early history of optimization technology for the design of microwave circuits—a personal journey filled with aspirations, academic contributions, and commercial innovations. Microwave engineers have evolved from being consumers of mathematical optimization algorithms to originators of exciting concepts and technologies that have spread far beyond the boundaries of microwaves. From the early days of simple direct search algorithms based on heuristic methods through gradient-based electromagnetic optimization to space mapping technology we arrive at today's surrogate methodologies. Our path finally connects to today's multi-physics, system-level, and measurement-based optimization challenges exploiting confined and feature-based surrogates, cognition-driven space mapping, Bayesian approaches, and more. Our story recognizes visionaries such as William J. Getsinger of the 1960s and Robert Pucel of the 1980s, and highlights a seminal decades-long collaboration with mathematician Kaj Madsen. We address not only academic contributions that provide proof of concept, but also indicate early formative milestones in the development of commercially competitive software specifically featuring optimization technology.

THE STUDY OF THE ELECTROMAGNETIC FIELD FROM THE SHIELDED MICROSTRIP LINE USING THE ELECTRODYNAMIC METHOD

The present article is the first from a series of three papers which will be published in this journal, and which provides a brief presentation of the book, “Microwave - numerical solutions”, written by the same author. The main objective of the present article is to describe the development of rigorous mathematical models for the optimal design of microwave circuits which use microstrip lines. The models will use real input data regarding the propagation characteristics of the electromagnetic field and the configuration of all existing wave modes in the line and will provide useful results for customer specific microwave applications.

Scalable modeling of grounded coplanar waveguide for MMICs design using neural network with an effective sampling strategy

In this paper, a scalable model of millimeter-wave grounded coplanar waveguide (GCPW) based on back propagation (BP) neural network is proposed. The relationship between sampling strategy and generalization accuracy is investigated, and the modeling idea of segmental sampling is proposed. The established multi-size GCPW model is first simulated using the electromagnetic simulation software High Frequency Structure Simulator to obtain the corresponding electrical characteristic parameters. Then different sampling strategies are used to obtain training data respectively, and the training data are used to train the neural network. The MSE of the GCPW neural network model obtained by using 30 sets of data was 0.0424, while the MSE of the neural network model obtained by using only 8 sets of training data were 0.43165 and 0.28671 respectively. The results show that the model established in this paper has high model accuracy and modeling efficiency, as well as good dimensional scalability and high generalization ability. The trained neural network model can be scaled to include a wide range of dimensions, and only the dimensions and frequency of the GCPW need to be used as input, and the neural network model can accurately output the corresponding electrical parameters. In addition, segmented modeling not only reduces the amount of training data and improves modeling efficiency, but also maintains accuracy. The neural network model proposed in this paper has high accuracy and can be used for accurate and rapid design and analysis of microwave circuits. The method can also be applied to the modeling of other transmission lines and can provide insight into the modeling of high frequency passive devices.

Bayesian Learning for Uncertainty Quantification, Optimization, and Inverse Design

Design of microwave circuits require extensive simulations, which often take significant computational time due to design complexity. This can be addressed through neural networks (NNs) that provide predictive capability. Predictions often come with uncertainties that need to be quantified. Moreover, optimization and inverse designs are better done using probabilities. This article describes the use of Bayes theorem and machine learning (ML) for solving complex microwave design problems.

A Robust Bayesian Optimization Framework for Microwave Circuit Design under Uncertainty

In modern electronics, there are many inevitable uncertainties and variations of design parameters that have a profound effect on the performance of a device. These are, among others, induced by manufacturing tolerances, assembling inaccuracies, material diversities, machining errors, etc. This prompts wide interests in enhanced optimization algorithms that take the effect of these uncertainty sources into account and that are able to find robust designs, i.e., designs that are insensitive to the uncertainties early in the design cycle. In this work, a novel machine learning-based optimization framework that accounts for uncertainty of the design parameters is presented. This is achieved by using a modified version of the expected improvement criterion. Moreover, a data-efficient Bayesian Optimization framework is leveraged to limit the number of simulations required to find a robust design solution. Two suitable application examples validate that the robustness is significantly improved compared to standard design methods.

High-Tc Superconducting Microwave and Millimeter Devices and Circuits—An Overview

High temperature (high-Tc) superconductors (HTS) have found many applications in the last two decades. To microwave researchers and engineers, the ultra-low surface resistance of the thin-film HTS materials at microwave and millimeter frequencies and the highly non-linear Josephson junctions are of particular interest. The former can be exploited in the design and fabrication of passive microwave components and circuits with superior performance, and the latter can be exploited to create many novel active HTS devices. This paper provides an overview of the state-of-art development of HTS devices and circuits for microwave and mm-wave communication front-end receiver systems. The paper is particularly focused on the latest advancement of HTS Josephson junction based active devices, monolithic microwave integrated circuits (MMIC), and whole receiver systems integrated with cryocoolers.

Performance Degradation Investigation for a GaAs PHEMT High Gain MMIC PA Taking into Account the Temperature

In order to comprehensively grasp the performance changes for the monolithic microwave integrated circuit (MMIC), this paper proposes that the complete temperature reliability tests for a 2.4–4.4 GHz gallium arsenide (GaAs) pseudomorphic high electron mobility transistor (pHEMT) high gain power amplifier (PA) should be investigated. The performance for this MMIC PA at different temperatures has been presented effectively. The results show that the direct current (DC) characteristics, small-signal gain (S21), and radio frequency (RF) output characteristics for this MMIC PA decrease and the output third-order intersection point (OIP3) increases with the rising temperature. The main factor influencing the performance is analyzed in detail. For further applications of this MMIC PA, several measures can be utilized to remedy the performance degradation. This paper can provide significant engineer guidance for the reliability design of RF microwave circuits.

A Novel Coupled Line Directional Coupler Design For L-Band Wireless Applications

Directional couplers are commonly used in microwave circuit design. Therefore, miniaturization of these components is very important. This paper presents the miniaturized microstrip coupled line directional coupler (CLDC) for L-band wireless applications. The coupled line directional coupler presented in the article was designed and simulated. In this paper coupler line directional coupler has been proposed with a low coupling factor. The proposed CLDC operates at the L-band and it is designed for use in mostly wireless applications. High and low impedance transmission lines are used to miniaturize the CLDC. The CLDC has been designed using a substrate material of FR-4 with a dielectric constant of 4.3 and substrate thickness of 1.57 mm. The size of the designed CLDC is 33.4 x15.05 〖mm〗^2. This is 58 % less than are of the conventional coupled line directional couplers. Also, The reflection coefficient and isolation level are in the permissible level in order for the proposed CLDC to be utilized in L-band wireless applications. The coupling factor of the designed coupled line directional coupler is between 28 dB and 21 dB at the L-band. The measured return loss value is better than 19 dB. Same time the isolation value is better than 23 dB at L-band.

Implementation of Microwave Circuits Using Stereolithography.

In this work, the use of additive manufacturing techniques through stereolithography for the manufacture of high-frequency circuits and devices is presented. Both the resin and the 3D printer used in this research are general-purpose commercial materials, not specifically intended for the implementation of microwave networks. The manufacturing and metallization procedures used to produce substrates for the design of planar microwave circuits are described, introducing the characterization process carried out to determine the electrical properties of the resin used. The ultrasonic techniques that allow the structural analysis of the manufactured substrates are also described. The electrical characterization provides a relative dielectric permittivity of 3.25 and a loss tangent of 0.03 for the resin used. In addition, the structural analysis shows a homogeneity and a finish of the manufactured parts that is not achievable using fused deposition modeling techniques. Finally, as a proof of concept, the design and manufacture of a complex geometry stepped impedance filter on a multi-height substrate using stereolithography techniques is presented, which allows for reducing the size of the traditional implementation of the same filter while maintaining its high-frequency response performance.

Approach for Extreme Learning Machine-Based Microwave Power Device Modeling

The nonlinear representation of active devices plays an important role in microwave circuit design. Whereas, it takes a long time to extract a large amount of large signal data, and the problem of memory resource and CPU occupancy becomes significant. In order to address the problems in traditional large-signal modeling methods, in this paper an X-parameter modeling method for microwave power devices based on extreme learning machine (ELM) is proposed. To demonstrate the effectiveness of this method, a double layer back propagation (BP) neural network model is established. Then, harmonic balance simulations are used to verify the accuracy of these two models. After comparisons, it is proved that the three harmonic errors of double layer BP neural network model are 9.525dBm, 1.309dBm and 14.593dBm, respectively, and the three harmonic errors of ELM model are 0.673 dBm, 0.314 dBm, 3.09 dBm, respectively. Furthermore, the three harmonic modulus errors of double layer BP neural network model are 0.031, 0.002, 7.665e-4, respectively, and the errors of ELM model are 0.005, 0.001, 8.38e-5, respectively. Finally, in order to verify the accuracy of the predicted model in circuit design, the predicted X-parameter is used in the design of power amplifier. Moreover, the errors of the double layer BP neural network prediction model at 2.5 GHz, 5 GHz and 7.5 GHz are 1.142 dBm, 1.436 dBm and 2.294 dBm, respectively. The output power error of the ELM model at 2.5 GHz, 5 GHz and 7.5 GHz are 0.089 dBm, 0.311 dBm and 0.309 dBm, respectively. These experimental results demonstrate that the established ELM model is an efficient and valid approach for modeling GaN high electron mobility transistor types of nonlinear microwave devices.