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In this paper, a novel concept of a three-dimensional full metal system including a Dual-Mode Converter (DMC) network integrated with a high-gain Conical Horn Antenna (CHA) is presented. This system is designed for 5G millimeter wave applications requiring monopulse operation at K-band (37.5–39 GHz). The DMC integrates two mode converters. They excite either the TE11cir or the TE01cir modes of the circular waveguide of the CHA. The input of the mode converters is the TE10rec mode of two independent WR-28 standard rectangular waveguide ports. By integrating the DMC with the CHA, the whole system, called a Dual-Mode Conical Horn Antenna (DM-CHA), is formed, radiating the sum (Σ) and difference (Δ) patterns associated to the monopulse operation. To adequately prevent the propagation of higher order modes and mode mutual coupling, this integration procedure is carefully designed and fabricated. To prove the performance of the design, the DMC network was fabricated using subtractive manufacturing by Computer Numerical Control (CNC) technology. The CHA was fabricated using additive manufacturing by Direct Metal Laser Sintering (DLMS) technology. Finally, the simulation and measurement results were exhaustively compared, including return loss, isolation, radiation pattern, and gain of the full DM-CHA structure. It is noteworthy that this system provided up to ±11° per beam in the angular of arrival detection to support the high data rate operation for 5G satellite communications in the millimeter-wave band.

A modified high gain single switch high-voltage converter is presented in this paper. The proposed converter is a blend of a voltage tripler and a SEPIC-boost mode converter. Its operational modes are presented in detail. This converter has advantages that include a single switch, reduced component stress and size, and reduced ripple output voltage and input ripple current. The simulation results of the suggested converter and a conventional multilevel SEPIC converter are presented. The prototype of a 30 V to 400 V input, 400 W output is developed and the performance of the designed topology is evaluated. The theoretical and experimental results conclude that this converter is suitable for high-voltage applications.

A mode converter design using the concept of periodic substrates loading in a circular waveguide, to convert TM 01 mode to TE 11 mode is presented in this paper. The detailed design principle, simulation, and measurement results are included in this study. Simulation results show that the purity of output fundamental TE 11 mode of the converter approaches 99.2% for an operating frequency of 3.2 GHz. The mode conversion efficiency is more than 90% over 3.07–3.25 GHz band and the relative bandwidth is 5.6% (180 MHz). The proposed TM 01 – TE 11 mode converter has advantages, such as the compact, lightweight structure, high conversion efficiency, and proper bandwidth. The fabrication cost is relatively low and the structure is easy to fabricate. The power-handling capability is limited to 10 MW due to dielectric-based design. The compactness and portability of the system (e.g. Space applications, Accelerators, High Power Microwave) can be improved significantly using the proposed mode converter.

This paper presents the design and optimization of a compact quasi-optical (QO) mode converter for a high-performance gyrotron operating at 105 GHz in the mode. The converter integrates a dimpled-wall launcher with a novel dual-direction perturbation technique alternating positive and negative deviations based on coupled mode theory. This approach reduces the launcher length to 85 mm, with a cut length of 20 mm (23.53% of the total length), while maintaining high mode conversion efficiency. MATLAB-based parametric analysis was used to optimize the launcher’s field distribution, and FEKO simulations validated its radiation performance. The mirror system comprising quasi-elliptical, elliptical, and parabolic mirrors ensures precise phase correction and beam shaping, contributing to high mode purity and compactness. Simulations demonstrate outstanding performance, achieving 99.4% scalar and 98.6% vector Gaussian mode content at the output. This design offers a compact and efficient solution for next-generation millimeter-wave applications.

In the big data era, mode division multiplexing, as a technology for extended channel capacity, demonstrates potential in enhancing parallel data processing capability. Consequently, developing a compact, high-performance mode converter through efficient design methods is an urgent requirement. However, traditional design methodologies for these converters face significant computational complexities and inefficiencies. Addressing this challenge, this paper introduces a novel topology optimization design method for mode converters employing a Dynamic Adjustment of Update Rate (DAUR). This approach markedly reduces computational overhead, accelerating the design process while ensuring high performance and compactness. As a proof-of-concept, an ultra-compact dual-mode converter was designed. The DAUR method demonstrated an 80% reduction in computational time compared to traditional methods, while maintaining a compact design (only 1.4 μm × 1.4 μm) and an insertion loss under 0.68 dB across a wavelength range of 1525 nm to 1575 nm. Meanwhile, simulated inter-mode crosstalk remained below − 24 dB across a 40 nm bandwidth. A comprehensive comparison with traditional inverse design algorithms is presented, demonstrating our method’s superior efficiency and effectiveness. Our findings suggest that DAUR not only streamlines the design process but also facilitates exploration into more complex micro-nano photonic structures with reduced resource investment.

This paper presents a review of our work concerning the recent progress in fabrications and applications of heating-induced long period fiber gratings (LPFGs). Firstly, three kinds of heating fabrication techniques based on CO2 laser, hydrogen–oxygen flame and arc discharge are demonstrated to fabricate LPFGs, i.e., standard LPFGs (SLPFGs) and helical LPFGs (HLPFGs), in different types of optical fibers such as conventional fibers, photonic crystal fibers, and photonic bandgap fibers. Secondly, the all-fiber orbital angular momentum (OAM) mode converters based on heating-induced SLPFGs and HLPFGs in different types of fibers are studied to increase the transmission capacity. Finally, the heating-induced SLPFGs and HLPFGs are investigated to develop various LPFG-based strain, pressure, torsion and biochemical sensors.

In this paper, a numerical analysis of a plasmonic sensor based on a metal-insulator-metal (MIM) waveguide is conducted for the detection of tuberculosis (TB)-infected blood plasma. It is not straightforward to directly couple the light to the nanoscale MIM waveguide, because of which two Si3N4 mode converters are integrated with the plasmonic sensor. This allows the efficient conversion of the dielectric mode into a plasmonic mode, which propagates in the MIM waveguide via an input mode converter. At the output port, the plasmonic mode is converted back to the dielectric mode via the output mode converter. The proposed device is employed to detect TB-infected blood plasma. The refractive index of TB-infected blood plasma is slightly lower than that of normal blood plasma. Therefore, it is important to have a sensing device with high sensitivity. The sensitivity and figure of merit of the proposed device are ~900 nm/RIU and 11.84, respectively.

The main goal of this study was to derive small-signal models of the input characteristics of buck, boost, and flyback converters working in continuous conduction mode (CCM) and discontinuous conduction mode (DCM). The models presented in the paper were derived using the separation of variables approach and included the parasitic resistances of all converter components. The paper features a discussion about the limitations of the model accuracy. The presented characteristics were obtained by calculation and verified by measurements. The input characteristics of converters are essential in the design of converters used in Power Factor Correction systems as well as in maximum power point tracking systems (MPPT).

We demonstrated a wavelength-tunable, ultra-wideband, biconical, long-period fiber grating (BLPFG) mode converter in a two-mode fiber based on fusion taper technology and CO2 laser writing technology. Theoretical and experimental results show that after changing the diameter of the two-mode fiber by fusing and tapering, the dispersion turning point of the fiber is adjusted and wavelength-tunable broadband mode conversion is achieved efficiently. Theoretical simulation shows that the mode conversion bandwidth can cover the O + E + S + C band. In the experiment, we fabricated adiabatic tapers with cladding diameters of 113 μm and 121 μm and wrote gratings on these tapers to achieve dual-resonance coupling, thus realizing mode conversion from LP01 to LP11, with a 15 dB bandwidth of 148.8 nm from 1229.0 nm to 1377.8 nm and of 168.5 nm from 1319.7 nm to 1488.2 nm, respectively. As far as we know, this is the first time that fusion taper technology has been used to adjust the window of the dual-resonant coupling of an optical fiber. This work broadens the scope of application of the dual-resonance effect and proposes a general method for widening the bandwidth of a fiber grating with tunable wavelength.

The mode converter, as a passive mode conversion device in transmission lines, is well-investigated and widely implemented in various electromagnetic systems. However, most traditional mode converters can only realize a single conversion mode. Thus, a mode converter achieving multiple controllable output modes is urgently needed. In this paper, a reconfigurable mode converter operating in the microwave range is achieved by embedding a deformable all-dielectric material with quadrilateral shape into a rectangular waveguide based on coupled-mode theory. It can achieve different target modes with controllable output for the same input by exciting the deformable all-dielectric material. The design principle of the mode converter is expounded concretely and simulation is carried out using HFSS software 2022 R2. Experimental results, consisting of the simulation results, demonstrate that the proposed mode converter can achieve various mode conversions with mode purity higher than 95%. This article innovatively applies deformable materials to waveguide mode conversion, expanding the application of deformable memory materials in electromagnetic devices.