Progress in THz Rectifier Technology: Research and Perspectives

Schottky diode (SD) has seen great improvements in the past few decades and, for many THz applications, it is the most useful device. However, the use and recycling of forms of energy such as solar energy and the infrared thermal radiation that the Earth continuously emits represent one of the most relevant and critical issues for this diode, which is unable to rectify signals above 5 THz. The goal is to develop highly efficient diodes capable of converting radiation from IR spectra to visible ones in direct current (DC). A set of performance criteria is investigated to select some of the most prominent materials required for developing innovative types of electrodes, but also a wide variety of insulator layers is required for the rectification process, which can affect the performance of the device. The current rectifying devices are here reviewed according to the defined performance criteria. The main aim of this review is to provide a wide overview of recent research progress, specific issues, performance, and future directions in THz rectifier technology based on quantum mechanical tunneling and asymmetric structure

Thrust Vector Controller Comparison for a Finless Rocket

The paper focuses on comparing applicability, tuning, and performance of different controllers implemented and tested on a finless rocket during its boost phase. The objective was to evaluate the advantages and disadvantages of each controller, such that the most appropriate one would then be developed and implemented in real-time in the finless rocket. The compared controllers were Linear Quadratic Regulator (LQR), Linear Quadratic Gaussian (LQG), and Proportional Integral Derivative (PID). To control the attitude of the rocket, emphasis is given to the Thrust Vector Control (TVC) component (sub-system) through the gimballing of the rocket engine. The launcher is commanded through the control input thrust gimbal angle δ , while the output parameter is expressed in terms of the pitch angle θ . After deriving a linearized state–space model, rocket stability is addressed before controller implementation and testing. The comparative study showed that both LQR and LQG track pitch angle changes rapidly, thus providing efficient closed-loop dynamic tracking. Tuning of the LQR controller, through the Q and R weighting matrices, illustrates how variations directly affect performance of the closed-loop system by varying the values of the feedback gain (K). The LQG controller provides a more realistic profile because, in general, not all variables are measurable and available for feedback. However, disturbances affecting the system are better handled and reduced with the PID controller, thus overcoming steady-state errors due to aerodynamic and model uncertainty. Overall controller performance is evaluated in terms of overshoot, settling and rise time, and steady-state error

Modeling and simulation of a digital control design approach for power supply systems

Electronic designers need to model and simulate system features as close as possible to its effective behaviour. Moreover, today, electronics systems are often composed of mixed analog and digital components. The increasing complexity has led to the use of different simulation softwares, each one specific for a particular level of abstraction: mathematical, circuital, behavioural, etc. In order to simulate the entire system these softwares should work together: co-simulation is necessary for digitally controlled power electronics systems. In this paper, the modeling of a digitally controlled switching power supply system using MATLAB/Simulink, ALDEC Active-HDL and Powersys PSIM is presented. The power converter is modelled in PSIM, the digital control is described in VHDL by using Active-HDL, and the complete system is simulated in MATLAB/Simulink environment. This design approach presents all the advantages of each used software and all its features will be discussed. The comparison between simulation and experimental results of the digitally controlled step-down converter prototype are reported

Dynamic reconfiguration of electrical connections for partially shaded PV modules: Technical and economical performances of an Arduino-based prototype

The partial shading phenomenon is a well known problem of photovoltaic plants. Partial shading leads to undesirable effects such the electrical mismatch, the generation of hot spots, and generally the decrease of production of electric energy. To mitigate the last effect, a dynamic reconfiguration of the electrical connections between modules was taken into account. In this paper, starting from an already developed system for a small-scale photovoltaic plant reconfiguration, the study of the economical benefits of the employment of a reconfigurator are traced. Five different incentive policies of diverse Countries have been considered to evaluate the increase of Net Present Value of system with and without a reconfigurator

Symmetric Vlasov-type antenna for High Power Microwave applications

We present a novel Vlasov-type antenna operating at 2.5 GHz and composed of a circular waveguide with a double bevel-cut. Simulation results show that the proposed antenna is capable of providing a wider emission angle if compared to standard Vlasov configurations, while still maintaining an adequate gain level. For this reason, it could be of interest for those High-Power Microwave (HPM) applications in which a larger area need to be covered by the EM field

An antenna array utilizing slotted conductive slab: inspired by metasurface and defected ground plane techniques for flexible electronics and sensors operating in the millimeter-wave and terahertz spectrum

This paper describes an innovative design of an antenna array that is metamaterial inspired using sub-wavelength slots and defected ground structure (DGS) for operation over millimeter-wave and terahertz (THz) spectrum. The proposed antenna array consists of a 2 × 4 array of conductive boxes on which are implemented rectangular slots. The presence of dielectric slots introduces resonant modes within the structure. These resonant modes result in enhancing the electromagnetic fields within the slots, which radiate energy into free space. The resonant frequencies and radiation patterns depend on the specific geometry of the slots and the dielectric properties. The antenna array is excited through a single microstrip line. The radiating elements in the array are interconnected to each other with a microstrip line. Unwanted mutual coupling between the radiating elements can degrade the performance of the antenna. This was mitigated by defecting the ground plane with rectangular slots. It is shown that this technique can enhance the array’s reflection coefficient over a wider bandwidth. The array was constructed on polyimide substrate having dielectric constant of 3.5 and thickness of 20 μm. The design was modelled, and its performance verified using an industry standard electromagnetic package by CST Studio Suite. The proposed array antenna has dimensions of 20 × 10 mm2 and operates between 80 and 200 GHz for radiation gain better than 4 dBi and efficiency above 55%. The peak radiation gain and efficiency are 7.5 dBi and 75% at 91 GHz, respectively. The operational frequency range of the array corresponds to a fractional bandwidth of 85.71%

Josephson Traveling Wave Parametric Amplifiers as non-classical light source for Microwave Quantum Illumination

Detection of low-reflectivity objects can be enriched via the so-called quantum illumination procedure. In order that this quantum procedure outperforms classical detection protocols, entangled states of microwave radiation are initially required. In this paper, we discuss the role of Josephson Traveling Wave Parametric Amplifiers (JTWPAs), based on circuit-QED components, as suitable sources of a two-mode squeezed vacuum state, a special signal-idler entangled state. The obtained wide bandwidth makes the JTWPA an ideal candidate for generating quantum radiation in quantum metrology and information processing applications

A Novel Conical Cut Frequency-Tapered Ring Bar SWS for High-Power and Wide-Bandwidth K-Band TWTs

This article presents a novel frequency-tapered Ring Bar Slow Wave Structure (RBSWS) for high-gain and wide-bandwidth Traveling Wave Tubes (TWTs) operating in the K-band for space applications. Starting from an analytical circuit model of the RBSWS, a conical-cut geometry is introduced to reduce the phase velocity. Our proposed novel RBSWS operates over a frequency range of 18.8 to 20.1 GHz, under a cathodic voltage and current of 19.8 kV and 0.3 A, respectively. Particle-In-Cell (PIC) results, carried out by CST Studio 2023, show a very high output peak power of 840.5 W at a gain of 20.2 dB, for an input power of 8 W, and an electron efficiency of 15.3%. The tapered RBSWS-TWT achieves a wider bandwidth, higher output power, and higher electron efficiency with respect to the untapered RBSWS-TWT, demonstrating the effectiveness of the proposed structure