DETERMINATION OF DYNAMIC RESPONSE COMPUTATION OF CONSTANT VOLTAGE PULSE CONVERTER MICROCHIPS

Work objective is the determination of data on the frequency-domain behavior of components in the composition of the microcircuit and within the microcircuit as a whole, intended for using in DC voltage pulse converters. Research methods: simulation modeling. Research results and novelty: for microcircuits with an external frequency weighing network a frequency analysis scheme using an auxiliary operational amplifier and an active low-pass filter of the second order is proposed. Using a simulator in the LT-spice environment, the amplitude and phase frequency response data of the microchips of the step-down and step-up converters have been obtained. The possibility of technical implementation of the proposed scheme for experimental determination of frequency-domain behavior including final control of the parameters of the appropriate microchips has been noted. For microchips having built-in frequency weighing circuit, the possibility of determining frequency-domain characteristics during the formation of a test signal in an external control circuit has been confirmed. It is found that the use of this method for microchips with increased dynamic properties is problematic. Conclusion: the frequency analysis scheme using an auxiliary operational amplifier is suitable for both step-down and step-up DC/DC converters with an external frequency weighing network. This scheme can be recommended for experimental determination of frequency-domain behavior, including final control of the parameters of the appropriate microchips.

Architecture for microcomb-based GHz-mid-infrared dual-comb spectroscopy

Dual-comb spectroscopy (DCS) offers high sensitivity and wide spectral coverage without the need for bulky spectrometers or mechanical moving parts. And DCS in the mid-infrared (mid-IR) is of keen interest because of inherently strong molecular spectroscopic signatures in these bands. We report GHz-resolution mid-IR DCS of methane and ethane that is derived from counter-propagating (CP) soliton microcombs in combination with interleaved difference frequency generation. Because all four combs required to generate the two mid-IR combs rely upon stability derived from a single high-Q microcavity, the system architecture is both simplified and does not require external frequency locking. Methane and ethane spectra are measured over intervals as short as 0.5 ms, a time scale that can be further reduced using a different CP soliton arrangement. Also, tuning of spectral resolution on demand is demonstrated. Although at an early phase of development, the results are a step towards mid-IR gas sensors with chip-based architectures for chemical threat detection, breath analysis, combustion studies, and outdoor observation of trace gases.

Frequency microcomb stabilization via dual-microwave control

Optical frequency comb technology has been the cornerstone for scientific breakthroughs in precision metrology. In particular, the unique phase-coherent link between microwave and optical frequencies solves the long-standing puzzle of precision optical frequency synthesis. While the current bulk mode-locked laser frequency comb has had great success in extending the scientific frontier, its use in real-world applications beyond the laboratory setting remains an unsolved challenge due to the relatively large size, weight and power consumption. Recently microresonator-based frequency combs have emerged as a candidate solution with chip-scale implementation and scalability. The wider-system precision control and stabilization approaches for frequency microcombs, however, requires external nonlinear processes and multiple peripherals which constrain their application space. Here we demonstrate an internal phase-stabilized frequency microcomb that does not require nonlinear second-third harmonic generation nor optical external frequency references. We demonstrate that the optical frequency can be stabilized by control of two internally accessible parameters: an intrinsic comb offset ξ and the comb spacing frep. Both parameters are phase-locked to microwave references, with phase noise residuals of 55 and 20 mrad respectively, and the resulting comb-to-comb optical frequency uncertainty is 80 mHz or less. Out-of-loop measurements confirm good coherence and stability across the comb, with measured optical frequency instability of 2 × 10−11 at 20-second gate time. Our measurements are supported by analytical theory including the cavity-induced modulation instability. We further describe an application of our technique in the generation of low noise microwaves and demonstrate noise suppression of the repetition rate below the microwave stabilization limit achieved.

Effect of color converters on the performance of solar or light-emitting diode pumped solid-state lasers

The effect of using external frequency converters on the luminescence intensity of an Nd:YAG crystal is studied. The crystal is illuminated by light-emitting diode (LED) with and without Y3Al5O12:Ce3+ material as an external converter. Obtained experimental results show that the luminescence intensity of Nd:YAG crystal increased by 1.5 times when Nd:YAG crystal is illuminated by LED together with color converter based on Y3Al5O12:Ce3+ demonstrating that external frequency converters can be a potential candidate for creating more efficient solar or LED pumped lasers.

Negative Effective Mass in Plasmonic Systems

We report the negative effective mass (density) metamaterials based on the electro-mechanical coupling exploiting plasma oscillations of a free electron gas. The negative mass appears as a result of the vibration of a metallic particle with a frequency of ω, which is close the frequency of the plasma oscillations of the electron gas m 2 relative to the ionic lattice m 1 . The plasma oscillations are represented with the elastic spring k 2 = ω p 2 m 2 , where ω p is the plasma frequency. Thus, the metallic particle vibrated with the external frequency ω is described by the effective mass m e f f = m 1 + m 2 ω p 2 ω p 2 − ω 2 , which is negative when the frequency ω approaches ω p from above. The idea is exemplified with two conducting metals, namely Au and Li.

Negative Effective Mass in Plasmonic Systems

We report the negative effective mass metamaterials based on the electro-mechanical coupling exploiting plasma oscillations of a free electron gas. The negative mass appears as a result of vibration of a metallic particle with a frequency of ω which is close the frequency of the plasma oscillations of the electron gas m_2 relatively to the ionic lattice m_1. The plasma oscillations are represented with the elastic spring k_2=ω_p^2 m_2, where ω_p is the plasma frequency. Thus, the metallic particle vibrated with the external frequency ω is described by the effective mass m_eff=m_1+(m_2 ω_p^2)/(ω_p^2-ω^2 ) , which is negative when the frequency ω approaches ω_p from above. The idea is exemplified with two conducting metals, namely Au and Li.

Assessment of Grid-Connected Wind Turbines with an Inertia Response by Considering Internal Dynamics

This paper presents a small-signal analysis of different grid side controllers for full power converter wind turbines with inertia response capability. In real wind turbines, the DC link controller, the drivetrain damping controller and the inertial response might present contradictory control actions in a close bandwidth range. This situation might lead to reduced control performance, increased component stress and non-compliance of connection agreements. The paper presents an analysis of the internal wind turbine dynamics by considering different grid-side converter control topologies: standard current control used in the wind industry, standard current control with inertia emulation capabilities and virtual synchronous machines. Comments are made on the similarities between each topology and the negative effects and limits, and possible remedies are discussed. Finally, the conclusion poses that the inclusion of a DC link voltage controller reduces the ability of a converter to respond to external frequency events without energy storage. The degradation increases with the DC link voltage control speed.

Theoretical Verification of Dielectric and Magnetic Properties of Polyaniline-Nickel Ferrite Nanocomposites Synthesized in Green Medium Extracted from the Fruit of Tamarindus indica

Nanocomposite materials of nickel ferrite incorporated polyaniline (PANI) have been synthesized via in situ oxidative polymerization technique in a green medium extracted from the fruit of plant Tamarindus indica. Synthesized particles were characterized by FT-IR spectroscopy, X-ray diffraction technique and scanning electron microscopy. Various samples of composites were prepared with 5, 10 and 15 g of filler nickel ferrite and the variation in dielectric permittivity is calculated by measuring the capacitance of the materials in various external frequency ranges from 100 Hz to 20 MHz. Experimental values of dielectric property are compared with theoretical values obtained from Maxwell-Wagner equation. The magnetic properties such as saturation magnetization (Ms), magnetic remanance (Mr) and coercivity (Hc) of the samples were analyzed by vibrating sample magnetometer (VSM). Retention of the magnetic filler in the PANI matrix is evaluated by comparing the experimental Ms values of the composites with the values computed from a theoretical linear equation. The experimental results were well fitted with the theoretical values and confirmed the synthesis of PANI-nickel ferrite composites with desired electrical and magnetic properties by varying the amount of components.

A plain approach for center manifold reduction of nonlinear systems with external periodic excitations

We present a relatively plain, direct and intuitive methodology that accomplishes model order reduction on the invariant center manifold of large-dimensional nonlinear systems subjected to external periodic excitations. This methodology is applicable to parametrically excited (periodic coefficients) and constant coefficient nonlinear systems. Our approach is empowered by intuitive augmentation of system states and is further liberated from typical special strategies such as the need for a ‘book-keeping’ parameter, a detuning parameter and minimal excitation. Consequently, it is relatively straightforward to implement and applicable to a broad range of nonlinear systems with external periodic excitations. Two illustrative application cases are investigated, and their subsequent results validate the accuracy of our approach. The first case considers a parametrically excited system with a single external periodic frequency excitation. A mass-spring-damper system with constant coefficients and two heterogeneous external frequency excitations is considered in the second example. In both cases, the long-term steady-state behavior analysis shows exact or cogent agreement between the original and the reduced-order system.