Passive Microwave Circuits Research Articles

Expedited re-design of multi-band passive microwave circuits using orthogonal scaling directions and gradient-based tuning

Geometry scaling of microwave circuits is an essential but challenging task. In particular, the employment of a given passive structure in a different application area often requires re-adjustment of the operating frequencies/bands while maintaining top performance. Achieving this necessitates the utilization of numerical optimization methods. Nonetheless, if the intended frequencies are distant from the ones at the starting point, local search procedures tend to fail, whereas global search algorithms are computationally expensive. As recently demonstrated, a combination of large-scale concurrent geometry parameter scaling with intermittent local tuning allows for dependable re-design of high-frequency circuits at low CPU costs. Unfortunately, the procedure is only applicable to single-band structures due to synchronized modifications of all operating bands under scaling. This article discusses a novel procedure that leverages a similar overall concept, but allows for independent control of all center frequencies. To achieve this goal, an automated decision-making procedure is developed in which a set of orthogonal scaling directions are determined based on their effect on individual circuit bands, and using auxiliary optimization sub-problems. The scaling range is then automatically computed by solving an appropriately-defined least-square design relocation problem. The methodology introduced in the work is illustrated using two planar passive devices. In both cases, wide-range operating frequency re-design has been demonstrated and favorably compared to conventional gradient-based tuning. Furthermore, the presented procedure has been shown to be computationally efficient. It is also easy to implement and integrate with a variety of gradient-based optimization procedures of a descent type.

Planar Mercator Smith Chart: An Alternative Approach for Active and Passive Microwave Circuits

This letter proposes a Planar Mercator Smith chart (PMSC), which can be used to design and analyze both active and passive microwave circuits on a 2-D flat surface. The entire surface of the 3-D Smith chart comprises of whole impedance plane, which includes all possible loads is projected to the 2-D flat surface of the PMSC using the mathematical principle of Mercator projection. This eliminates the need for CAD software to be used as a design tool or visualization aid unlike a 3-D Smith chart, and it may be a useful graphical chart for solving microwave problems involving any type of load.

Computationally-efficient statistical design and yield optimization of resonator-based notch filters using feature-based surrogates

Modern microwave devices are designed to fulfill stringent requirements pertaining to electrical performance, which requires, among others, a meticulous tuning of their geometry parameters. When moving up in frequency, physical dimensions of passive microwave circuits become smaller, making the system performance increasingly susceptible to manufacturing tolerances. In particular, inherent inaccuracy of fabrication processes affect the fundamental operating parameters, such as center frequency or bandwidth, which is especially troublesome for narrow-band structures, including notch filters. The ability to quantify the effects of tolerances, and—even more—to account for these in the design process, are instrumental in making the designs more reliable, and to increase the likelihood that adequate operation is ensured despite manufacturing errors. This paper proposes a simple yet computationally efficient and reliable procedure for statistical analysis and yield optimization of resonator-based notch filters. Our methodology involves feature-based surrogate models that can be established using a handful of training data points, and employed for rapid evaluation of the circuit fabrication yield. Furthermore, a yield optimization procedure is developed, which iteratively sets up a sequence of feature-based models, constructed within local domains relocated along the optimization path, and uses them as predictors to find a robust (maximum yield) design at a low computational cost. The presented approach has been demonstrated using two complementary split ring resonator (CSRR)-based notch filters. The cost of statistical design is about a hundred of EM simulations of the respective filter, with yield evaluation reliability corroborated through EM-based Monte Carlo analysis.

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.

Dual-Band Design Techniques for Microwave Passive Circuits: A Review and Applications

The introduction of new technology in the wireless communication industry increases the number of frequency bands in the communication environment. Therefore, a communication system capable of functioning over several frequency bands, known as a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">multiband communication system</i> , is required. In addition, multiband communication systems support technology upgrades by smoothly bridging the migration from the existing technology to a newer technology. A multiband communication system can be developed with the help of two approaches. The first approach is a multiband communication system that contains multiple microwave circuits, with each circuit optimized for a single band; for example, a dual-band communication system has two low-pass filters and two power amplifiers. But this approach increases not only the size but also the cost of the system. In the second approach, rather than using a separate power amplifier and filter for each frequency band, a single power amplifier, filter, and other components are used that can support more than one frequency band. These circuits are known as <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">multiband microwave circuits</i> . Multiband circuits not only minimize size but also reduce the cost of designing the multiband communication system.

A novel design of a reconfigurable power divider with stubs for mobile applications

&lt;p&gt;&lt;span&gt;Nowadays, the world knows a huge revolution in telecommunications, which has led to the need to integrate many services, such as long-term evolution (LTE), 5G, wireless local area network (WLAN), and Bluetooth, in one receiving and transmitting device. In the same way, all active and passive microwave circuits must be compatible with the integration of services, including the power divider, which is the subject of our work. This passive component is used in several fields such as medicine, surveillance, radar systems and others applications. Wilkinson divider is one of the most prominent power dividers, it is classified as narrow-band power divider and it is a very useful component in mobile applications (2.4 and 5.8 GHz). In this work, a reconfigurable 4-ports Wilkinson divider is designed using PIN diodes and simulated using connected speech test (CST) simulator software. This designed divider can easily modify the operation mode by activating or disabling the PIN diodes.&lt;/span&gt;&lt;/p&gt;

On Improved-Reliability Design Optimization of High-Frequency Structures Using Local Search Algorithms

The role of numerical optimization has been continuously growing in the design of high-frequency structures, including microwave and antenna components. At the same time, accurate evaluation of electrical characteristics necessitates full-wave electromagnetic (EM) analysis, which is CPU intensive, especially for complex systems. As rigorous optimization routines involve repetitive EM simulations, the associated cost may be significant. In the design practice, the most widely used EM-driven procedures are by far local (e.g., gradient-based) ones. While typically incurring acceptable expenses that range from dozens to a few hundreds of objective function evaluations, they are prone to failure whenever a decent initial design is not available. Representative scenarios include simulation-based size reduction of compact devices or re-design of structures for operating/material parameters being distant from those at the available design. A standard mitigation approach is the involvement of global search methods, which entails significantly higher computational costs. This paper reviews the recent methodologies introduced to improve the reliability of local parameter tuning algorithms without degrading their computational efficiency. We discuss frequency-based regularization, adaptively adjusted design specification approach, as well as accelerated feature-based optimization. All of these techniques incorporate mechanisms that improve the performance of the search process under challenging scenarios, primarily poor initial conditions. The outline of the mentioned methods is accompanied by illustrative examples including passive microwave circuits and microstrip antennas. Benchmarking against conventional local search is provided as well. Furthermore, the paper discusses the advantages and disadvantages of the reviewed frameworks as well as speculates about future research directions.

Inductorless, Widely Tunable N-Path Shekel Circulators Based on Harmonic Engineering

Recently demonstrated non-magnetic circulators rely on the interference between a linear periodically time-varying nonreciprocal gyrator and reciprocal passive microwave circuits, which limits their form factor and tunability. In this work, a new class of widely tunable non-magnetic inductorless nonreciprocal circulators based on harmonic engineering is introduced. LPTV circuits rely on modulating the input signal with a square-wave clock that contains multiple harmonics. The introduced harmonic engineering concept controls the response of the circuit to various harmonics of the clock waveform, the superposition of which results in the desired functionality. Two miniaturized N-path Shekel circulators have been implemented in 65-nm CMOS. The first prototype, which uses a four-path structure operating in the large- RC-regime, can be reconfigured for operation across 0.1-1.1 GHz with losses ranging from 2.5 to 3.4 dB. It has a form factor of (λ <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /(2×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> )) at 500 MHz, with a power consumption of 3-21 mW. The second prototype uses an eight-path structure and operates in the low- RC-regime with a tuning range of 0.28-1.15 GHz and losses of 2.3-3.3 dB and achieves more than 20-dB isolation across a 233-MHz BW (38%) within a (λ <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /(1.5×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> )) form factor at 600 MHz consuming 26-67 mW of power. To date, this work has the smallest form factor reported among the state of the art.

АВТОМАТИЗИРОВАННЫЙ СТРУКТУРНО-ПАРАМЕТРИЧЕСКИЙ СИНТЕЗ СТУПЕНЧАТОГО НАПРАВЛЕННОГО ОТВЕТВИТЕЛЯ НА СВЯЗАННЫХ ЛИНИЯХ НА ОСНОВЕ ГЕНЕТИЧЕСКОГО АЛГОРИТМА

An automated approach to the structural-parametric synthesis of a stepped directional coupleron connected lines based on a genetic algorithm (GA) is described, which makes it possible tocreate an algorithmic environment in the field of genetic search for solving NP complete problems,in particular, the structural-parametric synthesis of a stepped directional coupler on connectedlines. The purpose of this work is to find ways of structural-parametric synthesis of a stepped directionalcoupler on coupled lines based on the bionspiration theory. The scientific novelty lies inthe development of a modified genetic algorithm for automated structural-parametric synthesis ofa stepped directional coupler on connected lines. The problem statement in this work is as follows:to optimize the synthesis of passive and active microwave circuits by using a modified GA. A fundamentaldifference from the known approaches in the use of new modified genetic structures inautomated structural-parametric synthesis, in addition, a new method for calculating a steppeddirectional coupler on connected lines based on a modified GA is righteous in the work. Thus, theproblem of creating methods, algorithms and software for automated structural synthesis of microwavemodules is currently of particular relevance. Its solution will improve the quality characteristicsof the designed devices, reduce design time and costs, and reduce the requirements fordeveloper qualifications.

Coplanar Waveguide Based Sensor Using Paper Superstrate for Non-Invasive Sweat Monitoring

This paper presents a broadband, simple, re-useable and low-cost approach for noninvasive sweat monitoring using a passive microwave circuit and a cellulose filter paper as a superstrate. The proposed sensor is composed of filter paper with the ability to absorb the sample liquid under test (LUT) placed on top of a coplanar waveguide (CPW) transmission line. Various samples of sodium chloride (NaCl) solutions with concentrations in the range of 0.01-2 mol/L and models of artificial sweat are used to test the proposed sensor. The difference in transmission coefficient (S21) between dry and wet states is used to determine the concentrations of tested solutions in the band of 1-6 GHz. The sensor detects concentrations as low as 0.01 mol/L (0.58 g/L) and quantities as low as $137~\mu \text{L}$ with a maximum sensitivity of 46.7 dB/g/L. The proposed sensor presents a simple approach to sample and characterize liquids with enhanced sensitivity and consistent performance using microwave signals.

Analysis of Microwave Passive Circuits Designed Using 3D Printing Techniques

This work presents the results of a preliminary study conducted to assess the viability of using 3D printing techniques for the manufacturing of microwave passive circuits based on microstrip techniques, both for prototyping new low-cost devices and for fast and costless testing of new circuits designs. The study was aimed to test two crucial factors in the viability of these procedures: the performance of the circuit in terms of its functionality and the structural integrity of the resulting structure. A low-cost 3D printer is proposed for the dielectric substrate design of microstrip circuits. Standard PolyLactic Acid (PLA) material has been characterized in the microwaves frequencies for different substrate sizes and densities. To verify the proposed method, a low-pass stepped impedance filter was designed, simulated, and measured. Finally, a structural analysis using Non-Destructive Testing (NDT) ultrasonic techniques has been carried out based on deconvolution and resonant spectroscopy. Both, electronic and structural results, have shown the feasibility of using low-cost additive techniques in the design of microwave circuits. DOI: 10.5755/j01.eie.25.2.23202

Data Transmission Analysis using MW-5000 at 5.8 GHz Frequency

&lt;p align="justify"&gt;In the recent years, the data communication system become the main type of communication in the world. The FSK modulator or demodulator is one of the part that becomes the most important part and extremely advanced with the involvement of microwave active and passive circuits. This paper presents the data transmission analysis using MW-5000 at 5.8 GHz frequency. This experiment use the microwave communication module MW-5000 that is available in electronic laboratory. From this experiment the duration taken for the transmission of data is depend on the length of sentence and the value of baud rate.&lt;/p&gt;

High quality silicon-based substrates for microwave and millimeter wave passive circuits

Porous silicon substrate is very promising for next generation wireless communication requiring the avoidance of high-frequency losses originating from the bulk silicon. In this work, new variants of porous silicon (PSi) substrates have been introduced. Through an experimental RF performance, the proposed PSi substrates have been compared with different silicon-based substrates, namely, standard silicon (Std), trap-rich (TR) and high resistivity (HR). All of the mentioned substrates have been fabricated where identical samples of CPW lines have been integrated on. The new PSi substrates have shown successful reduction in the substrate's effective relative permittivity to values as low as 3.7 and great increase in the substrate's effective resistivity to values higher than 7kΩcm. As a concept proof, a mm-wave bandpass filter (MBPF) centred at 27GHz has been integrated on the investigated substrates. Compared with the conventional MBPF implemented on standard silicon-based substrates, the measured S-parameters of the PSi-based MBPF have shown high filtering performance, such as a reduction in insertion loss and an enhancement of the filter selectivity, with the joy of having the same filter performance by varying the temperature. Therefore, the efficiency of the proposed PSi substrates has been well highlighted.

An adaptive wideband frequency-sweeping algorithm and its application to full-wave analysis of multilayered structures

In this paper, with the fast and accurate evaluation of multilayered Greens functions, we propose an adaptive algorithm of wideband frequency sweeping for microwave passive circuits, which is based on the mixed potential integral equation (MPIE).The proposed method selects Chebyshev zeros from the frequency band as sampling points to perform interpolation. The relative error of the interpolated matrix can be calculated using the Frobenius norm, which can also be used as a criterion for convergence in the adaptive mechanism. A numerical example demonstrates that sampling Chebyshev zeros provides a much lower and more consistent error rate. Furthermore, the full-wave analysis of a microwave wideband passive circuit can be efficiently obtained using this algorithm without any a priori conditions. The trade-off between numerical accuracy and computational efficiency of this algorithm is obtained through numerous statistical experiments and discussed quantitatively.

Novel approach in design of miniaturized passive microwave circuit components using metamaterials

Novel approach in design of miniaturized passive microwave circuit components using metamaterials

Demonstration of RF and Microwave Passive Circuits Through 3-D Printing and Selective Metalization

The ultimate goal of this paper is to print radio frequency (RF) and microwave structures using a 3-D platform and to pattern metal films on nonplanar structures. To overcome substrate losses, air core substrates that can readily be printed are utilized. To meet the challenge of patterning conductive layers on complex or nonplanar printed structures, two novel self-aligning patterning processes are demonstrated. One is a simple damascene-like process, and the other is a lift-off process using a 3-D printed lift-off mask layer. A range of microwave and RF circuits are designed and demonstrated between 1 and 8 GHz utilizing these processes. Designs are created and simulated using Keysight Advanced Design System and ANSYS High Frequency Structure Simulator. Circuit designs include a simple microstrip transmission line (T-line), coupled-line bandpass filter, circular ring resonator, T-line resonator, resonant cavity structure, and patch antenna. A commercially available 3-D printer and metal sputtering system are used to realize the designs. Both simulated and measured results of these structures are presented.

Frequency‐periodic microwave passive circuits and their digital matching

Frequency-periodic microwave passive devices can be analysed in such a way that the coefficients of their digital counterparts can be extracted. In this study, this analysis procedure is exploited with the aim of providing a new theoretical framework to model these circuits, which could hopefully make their synthesis easier in the future. Interesting results observed from the application of this method to three examples of passive devices are as follows: (i) the appearance of zero-pole cancelations (ZPCs), (ii) the explanation of the required redundancy in certain microwave structures, and (iii) some difficulties observed in the synthesis of some frequency-periodic circuits, given a predefined digital design as a single starting point. The ZPCs appearing for the first example corresponding to a stepped-impedance-stub-based lowpass filter explain its inherent structure redundancy. Next, the analysis performed for a frequency-periodic wide-band matching network as second example also reveals the ZPC phenomenon, which justifies the existence of difficulties in its theoretical synthesis starting from a prefixed digital design. Finally, the third example consists in the application of the procedure to the well-known 3-dB branch-line hybrid, for which no ZPCs arise.

Single-conductor co-planar quasi-symmetry unequal power divider based on spoof surface plasmon polaritons of bow-tie cells

In this paper, the spoof surface plasmon polaritons (SSPPs) transmission line (TL) of periodical grooved bow-tie cells is proposed. The complex propagation constant and characteristic impedance of the SSPPs TLs and microstrip lines (MLs) are extracted using the analytical method of generalized lossy TL theory. The properties of the SSPPs TLs with different substrates and the same geometrical configuration are experimented. Then, for comparison, two ML counterparts are also experimented, which shows that the SSPPs TL is less sensitive to the thickness, dielectric constant and loss tangent of the chosen substrate below the cutoff frequency, compared with the ML ones. The single-conductor co-planar quasi-symmetry unequal power divider based on this SSPPs TL is presented in microwave frequencies. For experimental validation, the 0-dB, 2-dB, and 5-dB power dividers are designed, fabricated, and measured. Both simulated and measured results verify that the unequal power divider is a flexible option, which offers massive advantages including single-conductor co-planar quasi-symmetry structures, wide-band operation, and convenient implementations of different power-dividing ratios. Hence, it can be expected that the proposed unequal power dividers will inspire further researches on SSPPs for future design of novel planar passive and active microwave components, circuits and systems.

Power amplifier linearisation using digital predistortion and multi‐port techniques

Power amplifiers are essential components in communication systems and are inherently non-linear. The non-linearity creates spectral growth (broadening) beyond the signal bandwidth, which interferes with adjacent channels. It also causes distortions within the signal bandwidth, which decreases the bit error rate at the receiver. This study reports an adaptive digital predistorter with fast convergence rate and low complexity and cost to alleviate these problems. In this design, a lookup table-based adaptive digital predistortion (DPD) technique using a five-port receiver instead of traditional heterodyne and homodyne architectures is proposed to realise the linearisation loop for this amplifier. The five-port receiver is implemented by use of passive microwave circuits and detector diodes. This approach highly reduces the cost and complexity of the linearisation system. Simulation and measurement results obtained are presented for a laterally diffused metal–oxide–semiconductor-based high-power amplifier biased in class AB operation with wideband code-division multiple access input signal to demonstrate the effectiveness of this novel DPD design. Moreover, these results are compared with DPD technique using homodyne receiver in feedback path.

Design and characterization of a resonator-based metamaterial and its sensor application using microstrip technology

Design of a metamaterial based on an S-shaped resonator surrounded by a ground frame and excited by using a feeding transmission line on microstrip technology is presented. Since the resonator, ground frame, and its excitation mechanism are all realized on a microstrip, its characterization can be carried out using common laboratory equipment without needing any waveguide components or plane-wave-illumination techniques. The structure presented here may be realized on any microstrip and does not require special materials. The resonator and ground frame are both on the same side of the microstrip, thus the proposed topology may also be populated with active and passive microwave components, and hybrid active, passive, or reconfigurable microwave circuits may be realized. In metamaterial designs that require plane wave illumination, usually many numbers of periodic unit cells are needed; however, in our design, only one cell is capable of achieving metamaterial properties. The constitutive parameters of the metamaterial are retrieved and compared to demonstrate the agreement between simulations and measurements. The proposed topology is also demonstrated in a sensor application, where simulated and measured results agree well. Thus, it can be realized using standard microwave technology and used for numerous applications where metamaterial properties are needed.