Microwave

17 pages, 13522 KB

Open AccessArticle

Distance-Invariant Constant-Power DC-to-DC Wireless Power Transfer Using Nonlinear Resonance

by Abdullah Alothman, Andrew DeVries and Amir Mortazawi

Microwave 2026, 2(1), 5; https://doi.org/10.3390/microwave2010005 - 26 Feb 2026

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Wireless power transfer (WPT) systems are generally sensitive to variations in separation distance and coil alignment, which result in reduced power transfer efficiency and delivered power. Various approaches based on control system and active matching circuits have resulted in more complex implementations. This work, by contrast, presents a full DC–DC inductively coupled WPT system employing coupled nonlinear resonators to automatically adapt the system for variations in transfer coil separation and orientation, maintaining high transfer efficiency at a constant output power level. With entirely passive circuit components, the nonlinear resonators suppress the frequency-splitting phenomenon typical of WPT systems that leads to efficiency degradation. A class-EF power amplifier used in the transmitter experiences an approximately constant impedance, providing a constant output power while maintaining high efficiency. On the receive side, a class-E rectifier operates at a constant input power, achieving high overall efficiency without active control. An experimental demonstration delivers 5 W with a 6.12% power variation over a 1 to 9 cm distance variation and achieves a peak DC–DC efficiency of 71.6%. The response of the system to changes in coil separation is compared with a conventional linear WPT circuit, showing a constant-power and high-efficiency operation. Full article

(This article belongs to the Special Issue Advances in Microwave Devices and Circuit Design)

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20 pages, 4533 KB

Open AccessReview

Microwave-Assisted Processing of Advanced Materials: A Comprehensive Review of CNR-SCITEC Genova Developments

by Maurizio Vignolo

Microwave 2026, 2(1), 4; https://doi.org/10.3390/microwave2010004 - 31 Jan 2026

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Abstract

Microwave-assisted heating (MWH) has established itself as a transformative and energy-efficient paradigm for advanced materials processing. This review provides a comprehensive overview of the advances achieved at the CNR-SCITEC laboratories in Genoa. In this context, a customized microwave platform has been strategically employed for the synthesis, sintering, foaming, and melting of diverse inorganic, organic, and hybrid systems. The spectrum of materials investigated includes superconducting magnesium diboride (MgB₂), hydroxyapatite-based scaffolds, polyethylene components obtained via microwave-assisted rotational molding, cork-based sound-adsorbing composites, recycled expanded polystyrene (rEPS) panels, and polyvinylidene fluoride (PVDF) piezoelectric films. Across the case studies, MWH demonstrated a superior capacity for reducing energy consumption and processing times while maintaining—or even enhancing—the target functional properties. Furthermore, this work evaluates the technological maturity and emerging market opportunities of microwave-based processing, positioning it as a key and sustainable platform for next-generation materials development. Full article

(This article belongs to the Special Issue Microwave-Assisted Materials Design for Energy Storage and Conversion)

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22 pages, 3128 KB

Open AccessReview

Continuous Wave Magnetron Technologies

by Heping Huang, Bo Yang and Naoki Shinohara

Microwave 2026, 2(1), 3; https://doi.org/10.3390/microwave2010003 - 31 Dec 2025

Viewed by 929

Abstract

Continuous-wave magnetrons continue to offer the highest efficiency, lowest cost per watt, and greatest compactness among high-power microwave sources, making them attractive for industrial, scientific, and defense applications. Emerging missions, particularly space solar power systems, industrial microwave heating, and accelerators, demand significantly enhanced performance metrics, including high DC-to-RF efficiency, thermal stability, ultra-low phase noise, and precise phase controllability for coherent operation. To satisfy the critical requirement for high power, low-cost microwave sources with high spectral purity, extensive research has focused on injection-locking techniques, external phase/frequency modulation methods, and large-scale coherent power combining. This paper reviews the fundamental characteristics of CW magnetrons, recent advances in injection-locked magnetron transmitters, power-combining systems employing multiple injection-locked magnetrons, magnetron-based phased-array systems, and emerging applications. Finally, the challenges and promising development directions for next-generation CW magnetrons are discussed. Full article

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29 pages, 24222 KB

Open AccessArticle

A 60-GHz Current Combining Class-AB Power Amplifier in 22 nm FD-SOI CMOS

by Dimitrios Georgakopoulos, Vasileios Manouras and Ioannis Papananos

Microwave 2026, 2(1), 2; https://doi.org/10.3390/microwave2010002 - 27 Dec 2025

Viewed by 718

Abstract

This work presents a fully integrated, two-stage, deep class-AB power amplifier (PA) operating at a center frequency of 60 GHz. High efficiency and suppression of third-order intermodulation products are targeted, achieving improved linearity compared to reported state-of-the-art designs. A current combining architecture is also employed to enhance the output power capability. The PA is designed in a 22 nm FD-SOI CMOS technology and is optimized through a complete schematic-to-layout design flow. Post-layout simulations indicate that the PA achieves a peak power-added efficiency (PAE) of 28%, a saturated output power (

P_{s a t}

) of 20.2 dBm, and a maximum large-signal gain (

G_{m a x}

) of 19.6 dB at 60 GHz, evaluated at an operating temperature of 60 °C. The design maintains high linearity across the targeted output power range, exhibiting effective suppression of third-order intermodulation distortion (IMD3), which enhances its suitability for spectrally efficient modulation schemes. Full article

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17 pages, 1189 KB

Open AccessArticle

AI-Driven RF Fingerprinting for Secure Positioning Optimization in 6G Networks

by Ioannis A. Bartsiokas, Maria-Lamprini A. Bartsioka, Anastasios K. Papazafeiropoulos, Dimitra I. Kaklamani and Iakovos S. Venieris

Microwave 2026, 2(1), 1; https://doi.org/10.3390/microwave2010001 - 23 Dec 2025

Viewed by 727

Abstract

Accurate user positioning in 6G networks is essential for next-generation mobile services. However, classical approaches such as time-difference-of-arrival (TDoA) remain vulnerable to dense multipath and NLoS conditions commonly found in indoor and industrial environments. This paper proposes an AI-driven RF fingerprinting framework that leverages uplink channel state information (CSI) to achieve robust and privacy-preserving 2D localization. A lightweight convolutional neural network (CNN) extracts location-specific spectral–spatial fingerprints from CSI tensors, while a federated learning (FL) scheme enables distributed training across multiple gNBs without sharing raw channel data. The proposed integration of CSI tensor processing with FL and structured pruning is introduced as a novel solution for practical 6G edge positioning. To further reduce latency and communication costs, a structured pruning mechanism compresses the model by 40–60%, lowering the memory footprint with negligible accuracy loss. A performance evaluation in 3GPP-compliant indoor factory scenarios indicates a median positioning error below 1 m for over 90% of cases, significantly outperforming TDoA. Moreover, the compressed FL model reduces the FL communication load by ~38% and accelerates local training, establishing an efficient, secure, and deployment-ready positioning solution for 6G networks. Full article

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Microwave, Volume 2, Issue 1 (March 2026) – 5 articles

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