Research

16 pages, 12832 KiB

Open AccessArticle

Automatic Optimization of Input Split and Bias Voltage in Digitally Controlled Dual-Input Doherty RF PAs

by Mattia Mengozzi, Gian Piero Gibiino, Alberto Maria Angelotti, Alberto Santarelli, Corrado Florian and Paolo Colantonio

Energies 2022, 15(13), 4892; https://0-doi-org.brum.beds.ac.uk/10.3390/en15134892 - 04 Jul 2022

Cited by 9 | Viewed by 1417

Abstract

Digitally controlled Dual-Input Doherty Power Amplifiers (DIDPAs) are becoming increasingly popular due to the flexible input signal splitting between the main and auxiliary stages. Nevertheless, the presence of many degrees of freedom, e.g., input amplitude split and phase displacement as well as biasing [...] Read more.

Digitally controlled Dual-Input Doherty Power Amplifiers (DIDPAs) are becoming increasingly popular due to the flexible input signal splitting between the main and auxiliary stages. Nevertheless, the presence of many degrees of freedom, e.g., input amplitude split and phase displacement as well as biasing for multiple stages, often involves inefficient trial-and-error procedures to reach a suitable PA performance. This article presents automated parameter setting based on coordinate descent or Bayesian optimizations, demonstrating an improvement in the performance in terms of RF output power and power-added efficiency (PAE) in the presence of broadband-modulated signals, yet maintaining suitable linear behavior for, e.g., communications applications. Full article

(This article belongs to the Special Issue RF/Microwave Circuit Design and Characterization Techniques)

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12 pages, 16346 KiB

Open AccessArticle

Design and Implementation of a Dual-Band Filtering Wilkinson Power Divider Using Coupled T-Shaped Dual-Band Resonators

by Sobhan Roshani, Slawomir Koziel, Saeed Roshani, Faezeh Sadat Hashemi Mehr and Stanislaw Szczepanski

Energies 2022, 15(3), 1189; https://0-doi-org.brum.beds.ac.uk/10.3390/en15031189 - 06 Feb 2022

Cited by 7 | Viewed by 1844

Abstract

The paper introduces a novel structure of a dual-band filtering Wilkinson power divider (WPD). Its essential component is a dual-band bandpass filter (BPF), implemented using coupling lines and two T-shaped resonators. The BPF is incorporated into the divider structure to suppress the unwanted [...] Read more.

The paper introduces a novel structure of a dual-band filtering Wilkinson power divider (WPD). Its essential component is a dual-band bandpass filter (BPF), implemented using coupling lines and two T-shaped resonators. The BPF is incorporated into the divider structure to suppress the unwanted harmonics within the circuit. The latter is achieved owing to a wide stopband of the filter. The designed dual-band WPD can suppress third unwanted harmonics in both channels with high levels of attenuation. The designed dual-band WPD operates at 2.6 GHz and 3.3 GHz with a return loss of 22.1 dB and 22.3 dB at the operating frequencies. Furthermore, the insertion loss and isolation are 0.3 dB and 20.2 dB at 2.6 GHz and 0.9 dB and 24.5 dB at 3.3 GHz. The analysis and simulation results are corroborated by the measurements of the fabricated divider prototype. The competitive performance of the proposed circuit is also demonstrated through comparisons with state-of-the-art divider circuits from the literature. Full article

(This article belongs to the Special Issue RF/Microwave Circuit Design and Characterization Techniques)

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20 pages, 4148 KiB

Open AccessArticle

Improved-Efficacy EM-Based Antenna Miniaturization by Multi-Fidelity Simulations and Objective Function Adaptation

by Marzieh Mahrokh and Slawomir Koziel

Energies 2022, 15(2), 403; https://0-doi-org.brum.beds.ac.uk/10.3390/en15020403 - 06 Jan 2022

Cited by 5 | Viewed by 1318

Abstract

The growing demand for the integration of surface mount design (SMD) antennas into miniaturized electronic devices has imposed increasing limitations on the structure dimensions. Examples include embedded antennas in applications such as on-board devices, picosatellites, 5G communications, or implantable and wearable devices. The [...] Read more.

The growing demand for the integration of surface mount design (SMD) antennas into miniaturized electronic devices has imposed increasing limitations on the structure dimensions. Examples include embedded antennas in applications such as on-board devices, picosatellites, 5G communications, or implantable and wearable devices. The demands for size reduction while ensuring a satisfactory level of electrical and field performance can be managed through constrained numerical optimization. The reliability of optimization-based size reduction requires utilization of full-wave electromagnetic (EM) analysis, which entails significant computational costs. This can be alleviated by incorporating surrogate modeling techniques, adjoint sensitivities, or the employment of sparse sensitivity updates. An alternative is the incorporation of multi-fidelity simulation models, normally limited to two levels, low and high resolution. This paper proposes a novel algorithm for accelerated antenna miniaturization, featuring a continuous adjustment of the simulation model fidelity in the course of the optimization process. The model resolution is determined by factors related to violation of the design constraints as well as the convergence status of the algorithm. The algorithm utilizes the lowest-fidelity model for the early stages of the optimization process; it is gradually refined towards the highest-fidelity model upon approaching convergence, and the constraint violations improve towards the preset tolerance threshold. At the same time, a penalty function approach with adaptively adjusted coefficients is applied to enable the precise control of constraints, and to increase the achievable miniaturization rates. The presented procedure has been validated using five microstrip antennas, including three broadband, and two circularly polarized structures. The obtained results corroborate the relevance of the implemented mechanisms from the point of view of improving the average computational efficiency of the optimization process by 43% as compared to the single-fidelity adaptive penalty function approach. Furthermore, the presented methodology demonstrates a performance that is equivalent or even superior to its single-fidelity counterpart in terms of an average constraint violation of 0.01 dB (compared to 0.03 dB for the reference), and an average size reduction of 25% as compared to 25.6%. Full article

(This article belongs to the Special Issue RF/Microwave Circuit Design and Characterization Techniques)

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15 pages, 2884 KiB

Open AccessArticle

Design Centering of Compact Microwave Components Using Response Features and Trust Regions

by Anna Pietrenko-Dabrowska and Slawomir Koziel

Energies 2021, 14(24), 8550; https://0-doi-org.brum.beds.ac.uk/10.3390/en14248550 - 18 Dec 2021

Cited by 8 | Viewed by 1719

Abstract

Fabrication tolerances, as well as uncertainties of other kinds, e.g., concerning material parameters or operating conditions, are detrimental to the performance of microwave circuits. Mitigating their impact requires accounting for possible parameter deviations already at the design stage. This involves optimization of appropriately [...] Read more.

Fabrication tolerances, as well as uncertainties of other kinds, e.g., concerning material parameters or operating conditions, are detrimental to the performance of microwave circuits. Mitigating their impact requires accounting for possible parameter deviations already at the design stage. This involves optimization of appropriately defined statistical figures of merit such as yield. Although important, robust (or tolerance-aware) design is an intricate endeavor because manufacturing inaccuracies are normally described using probability distributions, and their quantification has to be based on statistical analysis. The major bottleneck here is high computational cost: for reliability reasons, miniaturized microwave components are evaluated using full-wave electromagnetic (EM) models, whereas conventionally utilized analysis methods (e.g., Monte Carlo simulation) are associated with massive circuit evaluations. A practical approach that allows for circumventing the aforementioned obstacles offers surrogate modeling techniques, which have been a dominant trend over the recent years. Notwithstanding, a construction of accurate metamodels may require considerable computational investments, especially for higher-dimensional cases. This paper brings in a novel design-centering approach, which assembles forward surrogates founded at the level of response features and trust-region framework for direct optimization of the system yield. Formulating the problem with the use of characteristic points of the system response alleviates the issues related to response nonlinearities. At the same time, as the surrogate is a linear regression model, a rapid yield estimation is possible through numerical integration of the input probability distributions. As a result, expenditures related to design centering equal merely few dozens of EM analyses. The introduced technique is demonstrated using three microstrip couplers. It is compared to recently reported techniques, and its reliability is corroborated using EM-based Monte Carlo analysis. Full article

(This article belongs to the Special Issue RF/Microwave Circuit Design and Characterization Techniques)

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10 pages, 827 KiB

Open AccessArticle

Estimation of Phase Noise Transfer Function

by Igor Rutkowski and Krzysztof Czuba

Energies 2021, 14(24), 8234; https://0-doi-org.brum.beds.ac.uk/10.3390/en14248234 - 07 Dec 2021

Viewed by 1825

Abstract

Quantifying frequency converters’ residual phase noise is essential in various applications, including radar systems, high-speed digital communication, or particle accelerators. Multi-input signal source analyzers can perform such measurements out of the box, but the high cost limits their accessibility. Based on an analysis [...] Read more.

Quantifying frequency converters’ residual phase noise is essential in various applications, including radar systems, high-speed digital communication, or particle accelerators. Multi-input signal source analyzers can perform such measurements out of the box, but the high cost limits their accessibility. Based on an analysis of phase noise transmission theory and the capabilities of popular instrumentation, we propose a technique extending the functionality of single-input devices. The method supplements absolute noise measurements with estimates of the phase noise transfer function (also called the jitter transfer function), allowing the calculation of residual noise. The details of the hardware setup used for the method verification are presented. The injection of single-tone and pseudo-random modulations to the test signal is examined. Optional employment of a spectrum analyzer can reduce the time and number of data needed for characterization. A wideband synthesizer with an integrated voltage-controlled oscillator was investigated using the method. The estimated transfer function matches a white-box model based on synthesizer’s structure and values of loop components. The first results confirm the validity of the proposed technique. Full article

(This article belongs to the Special Issue RF/Microwave Circuit Design and Characterization Techniques)

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23 pages, 570 KiB

Open AccessArticle

A Comprehensive Harmonic Analysis of Current-Mode Power Amplifiers

by Chiara Ramella, Paolo Colantonio and Marco Pirola

Energies 2021, 14(21), 7042; https://0-doi-org.brum.beds.ac.uk/10.3390/en14217042 - 28 Oct 2021

Viewed by 1713

Abstract

This work presents a comprehensive theoretical analysis of current-mode power amplifiers as a function of input power for different biasing classes under the common simplifying assumption of constant transconductance and hard current cut-off/saturation. Typically, the theoretical analysis of power amplifier performance and behavior [...] Read more.

This work presents a comprehensive theoretical analysis of current-mode power amplifiers as a function of input power for different biasing classes under the common simplifying assumption of constant transconductance and hard current cut-off/saturation. Typically, the theoretical analysis of power amplifier performance and behavior are carried out only at maximum output power. However, to achieve high data-rates, modern telecommunication systems adopt signals characterized by a very high peak-to-average power ratio, thus it is useful to analyze the power amplifier behavior as a function of power back-off. Moreover, in many cases, to enhance the efficiency and/or to apply harmonic shaping techniques, a clipped drain-source current, which approaches a square wave, is required. The classical analysis can be extended to low power levels only under the assumption of power-independent conduction angle, which is true only for class-A and class-B amplifiers, and does not take into account possible waveform clipping at maximum current. This work presents a complete theoretical Fourier analysis of FET-based power amplifiers as a function of quiescent drain-source current at any input power level and accounting for the clipped current case, up to the square-wave limit, reorganizing and completing the material that can be found in classical textbooks in the field. Full article

(This article belongs to the Special Issue RF/Microwave Circuit Design and Characterization Techniques)

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15 pages, 658 KiB

Open AccessArticle

Source/Load-Pull Noise Measurements at K_a Band

by Sergio Colangeli, Walter Ciccognani, Patrick Ettore Longhi, Lorenzo Pace, Antonio Serino, Julien Poulain, Rémy Leblanc and Ernesto Limiti

Energies 2021, 14(18), 5615; https://0-doi-org.brum.beds.ac.uk/10.3390/en14185615 - 07 Sep 2021

Viewed by 1477

Abstract

This paper is focused on the extraction of the noise parameters of a linear active device by exploiting both forward and reverse noise power measurements associated with different terminations. In order for load-pull measurements to yield a significant marginal improvement (as compared to [...] Read more.

This paper is focused on the extraction of the noise parameters of a linear active device by exploiting both forward and reverse noise power measurements associated with different terminations. In order for load-pull measurements to yield a significant marginal improvement (as compared to forward measurements only) it is expected that the device under test should appreciably deviate from unidirectionality. For this reason, the source/load-pull technique is applied to frequencies at which the considered devices are still usable but their reverse noise factor exhibits a measurable dependence on the output terminations. Details on the test bench set up to the purpose, covering the 20–40 GHz frequency range, are provided. A characterization campaign on a 60 nm gate length,

4 \times 35

µm GaN-on-Si HEMT fabricated by OMMIC is illustrated. Full article

(This article belongs to the Special Issue RF/Microwave Circuit Design and Characterization Techniques)

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18 pages, 7371 KiB

Open AccessArticle

Microwave Spectroscopy as a Potential Tool for Color Grading Diamonds

by Yossi Rabinowitz, Ariel Etinger, Asher Yahalom, Haim Cohen and Yosef Pinhasi

Energies 2021, 14(12), 3507; https://0-doi-org.brum.beds.ac.uk/10.3390/en14123507 - 12 Jun 2021

Cited by 2 | Viewed by 1888

Abstract

A diamond’s color grading is a dominant property that determines its market value. Its color quality is dependent on the light transmittance through the diamond and is largely influenced by nitrogen contamination, which induces a yellow/brown tint within the diamond, as well as [...] Read more.

A diamond’s color grading is a dominant property that determines its market value. Its color quality is dependent on the light transmittance through the diamond and is largely influenced by nitrogen contamination, which induces a yellow/brown tint within the diamond, as well as by structural defects in the crystal (in rare cases boron contamination results in a blue tint). Generally, spectroscopic instrumentation (in the infrared or UV–visible spectral range) is used in industry to measure polished and rough diamonds, but the results are not accurate enough for precise determination of color grade. Thus, new methods should be developed to determine the color grade of diamonds at longer wavelengths, such as microwave (MV). No difference exists between rough and polished diamonds regarding stray light when the MW frequency is used. Thus, several waveguides that cover a frequency range of 3.95–26.5 GHz, as well as suitable resonator mirrors, have been developed using transmission/reflection and resonator methods. A good correlation between the S₁₂ parameter and the nitrogen contamination content was found using the transmission/reflection method. It was concluded that electromagnetic property measurements of diamonds in the MW frequency range can be used to determine their nitrogen content and color grading. The MW technique results were in good agreement with those obtained from the infrared spectra of diamonds. Full article

(This article belongs to the Special Issue RF/Microwave Circuit Design and Characterization Techniques)

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10 pages, 2710 KiB

Open AccessArticle

A Stripline-Based Integrated Microfluidic-Microwave Module

by Laura Jasińska, Krzysztof Szostak, Mateusz Czok, Karol Malecha and Piotr Słobodzian

Energies 2021, 14(9), 2439; https://0-doi-org.brum.beds.ac.uk/10.3390/en14092439 - 25 Apr 2021

Cited by 1 | Viewed by 1484

Abstract

The paper presents the preliminary results on the development of an integrated stripline-based microwave-microfluidic module. The measurements were performed in a frequency range from 300 MHz up to 12 GHz, with the microchannel filled with three different test fluids—deionized water, the ethanol-water solution [...] Read more.

The paper presents the preliminary results on the development of an integrated stripline-based microwave-microfluidic module. The measurements were performed in a frequency range from 300 MHz up to 12 GHz, with the microchannel filled with three different test fluids—deionized water, the ethanol-water solution and pure ethanol. Due to the higher-than-expected losses in transmittance, the selected module was examined with use of the cross-sections taken along its length. The possible causes were highlighted and described. Likewise, the proposed areas of further investigations have been clearly described. Full article

(This article belongs to the Special Issue RF/Microwave Circuit Design and Characterization Techniques)

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