Input Frequency Research Articles

Novel Frequency Dependent OFET Attenuator Using ClInPc with Al2O3 Embedded Nanoparticles in Nylon 11 for Flexible Electronics

The Organic field-effect transistors (OFETs) have been largely investigated due to their low-cost manufacturing, flexibility, and lightweight, as well as their optical and electrical characteristics. That allow its application in sensors, amplifiers, attenuators signal filtering, and high-frequency response devices, like biosensing, wearable electronics, optoelectronics, telecommunications, and other potential applications. Throughout this investigation, a ClInPc flexible OFET with Al2O3 embedded particles in nylon 11, was manufactured and characterized to evaluate the optoelectronic and morphological properties. For the manufacturing, a high-vacuum thermal evaporation deposition technique was used, and UV-vis spectroscopy analysis and scanning electron microscopy were conducted to evaluate the optoelectronic and morphological properties. Also, a study regarding the electrical characteristics for different time-dependent wavefunction input signals, changing the input voltage and frequency, has been conducted. The latter was driven to determine the time-response characteristics, gains, phase shift and to determine whether the device function as an attenuator or an amplifier with the selected configuration. The device has been modelled to obtain the OFET operation parameters. A resulting capacitance of 567 pF was calculated. Uniform and continuous films where obtained, which guarantees an efficient charge transport. For all signals the output voltage is lower than that of the input voltage. Also, for the higher frequency the output voltage is decreased compared to lower frequencies. Gains decreasing variation of up to 0.05 indicate the operating application as an attenuator. Phase variation of up to 100 °, resulted while varying the input frequency. The model resulted on a gate capacitance value between 500 and 1180 pF, and gate-drain capacitance value between 50 and 500 pF. All of this could give evidence that state of the art ClInPc flexible OFET device with Al2O3 embedded nanoparticles in nylon 11 could be used toward current high-performance frequency-dependent flexible applications.

Compact high-efficiency energy harvesting positive and negative DC supplies voltage for battery-less CMOS receiver

In this paper, novel compact high-efficiency multi-band rectifiers that supply positive and negative output voltages are demonstrated for energy harvesting applications. The proposed voltage doubler circuits are used as real DC voltage supplies of radio frequency mm-wave CMOS receivers. Operating multi-band rectifiers have a complicated structure that required more resonance networks to force the rectifier to work in multi-band. Novel series and parallel resonance networks are implemented to force the rectifier to operate in dual-band at frequencies of 850 and 1400 MHz. The proposed resonance network eliminates the Schottky diode impedance variation as the input power or frequency changes and supports the impedance matching and minimizes the insertion loss. A novel high-quality sine-shape micro-strip inductor that obtains a quality factor above 65 over the frequency band from 200 to 1400 MHz and inductance equal to 14 ± 2 nH is designed to improve efficiency and enhance performance at low power levels. The first suggested RF voltage doubler rectifier with series resonance feedback between the input and cathode of the diode and parallel resonance operates at two frequency bands of 850 and 1400 MHz and obtains a peak conversion efficiency of 59%, a saturated output DC voltage is 2.5 V, and the conversion efficiency is 40% at RF-input-power of − 10 dBm. This voltage doubler achieves the required DC supply parameter (1.1 V and 450 uA) for biasing the mm-wave receiver at an RF input power of 0 dBm. Otherwise, the second suggested negative voltage rectifier has a maximum simulated conversion efficiency of 65%, saturated negative DC-voltage is − 3.5 V, and the conversion efficiency is 45% at an RF input power of − 10 dBm. The negative voltage rectifier obtains DC supply parameters (− 0.5 V and no current condition used for a gate bias) at − 10 dBm input power.

Surface Acoustic Wave (SAW)‐Based Sonoporation of Single‐Adherent‐Cell

Sonoporation refers to the formation of tiny transient pores in cell plasma membranes by using ultrasound to increase the permeability to bioactive materials. Recently, the Sonoporation technique has been widely researched in cell treatment applications, such as gene transfection. However, due to the random distribution of microbubbles, it is challenging to perform controllable and precise localized sonoporation of a target cell. In this work, a device based on the surface acoustic wave is developed to achieve a selective manipulation and cavitation of microbubbles. The device consists of a pair of microbubble positioning slant‐finger interdigital transducers (SFITs) for moving a selected microbubble in a two‐dimensional plane. Meanwhile, another narrow‐frequency‐band SFIT is integrated into the device for local cavitation control of the same microbubble. As a result, a microbubble can be transported orthogonal to and along the acoustic transmission path by continuously adjusting the input frequency and relative phase. Upon reaching the target cell, the selected microbubble can be cavitated without exciting other microbubbles, resulting in local sonoporation. The resolution of phase‐based positioning and frequency‐based transportation are 8.3 and 7.0 µm with 45° and 10 kHz settings, respectively.

Simulations predict differing phase responses to excitation vs. inhibition in theta-resonant pyramidal neurons.

Rhythmic activity is ubiquitous in neural systems, with theta-resonant pyramidal neurons integrating rhythmic inputs in many cortical structures. Impedance analysis has been widely used to examine frequency-dependent responses of neuronal membranes to rhythmic inputs, but it assumes that the neuronal membrane is a linear system, requiring the use of small signals to stay in a near-linear regime. However, postsynaptic potentials are often large and trigger nonlinear mechanisms (voltage-gated ion channels). The goals of this work were to 1) develop an analysis method to evaluate membrane responses in this nonlinear domain and 2) explore phase relationships between rhythmic stimuli and subthreshold and spiking membrane potential (Vmemb) responses in models of theta-resonant pyramidal neurons. Responses in these output regimes were asymmetrical, with different phase shifts during hyperpolarizing and depolarizing half-cycles. Suprathreshold theta-rhythmic stimuli produced nonstationary Vmemb responses. Sinusoidal inputs produced "phase retreat": action potentials occurred progressively later in cycles of the input stimulus, resulting from adaptation. Sinusoidal current with increasing amplitude over cycles produced "phase advance": action potentials occurred progressively earlier. Phase retreat, phase advance, and subthreshold phase shifts were modulated by multiple ion channel conductances. Our results suggest differential responses of cortical neurons depending on the frequency of oscillatory input, which will play a role in neuronal responses to shifts in network state. We hypothesize that intrinsic cellular properties complement network properties and contribute to in vivo phase-shift phenomena such as phase precession, seen in place and grid cells, and phase roll, also observed in hippocampal CA1 neurons.NEW & NOTEWORTHY We augmented electrical impedance analysis to characterize phase shifts between large-amplitude current stimuli and nonlinear, asymmetric membrane potential responses. We predict different frequency-dependent phase shifts in response excitation vs. inhibition, as well as shifts in spike timing over multiple input cycles, in theta-resonant pyramidal neurons. We hypothesize that these effects contribute to navigation-related phenomena such as phase precession and phase roll. Our neuron-level hypothesis complements, rather than falsifies, prior network-level explanations of these phenomena.

Analysis of transient laminar forced convective heat transfer in parallel-plate channels with time-varying thermal boundary conditions of the inlet and wall

The problem of transient laminar forced convective heat transfer in parallel-plate channels with time-varying thermal boundary conditions of the inlet and wall is thoroughly investigated in this study. By employing the methodologies of generalized integral transform technique (GITT) and Duhamel's theorem, we successfully derive an analytical solution for this problem. To validate the accuracy of our analytical findings, a comparison is made with the corresponding numerical solution, demonstrating a remarkable level of agreement between the two approaches. In order to obtain the general patterns of heat transfer, we employ a decoupling technique to separate the thermal response in the case of harmonic temperature boundary conditions of the inlet and wall. This approach enables us to uncover the intricate relationship between the weight coefficient of heat input and the two-dimensional spatial location of the channel, as well as the dimensionless angular frequency of heat input. Furthermore, we present the corresponding dimensionless cut-off angular frequency of heat input at various locations within the channel. To gain further insights, we conduct an in-depth analysis of the effects of integration time or distance on the dimensionless optimum angular frequency corresponding to the dimensionless maximum average heat flux.

Analysis of a DC converter working on a plasma arc

Introduction. The article is devoted to the analysis of a stabilized direct current converter operating on a plasma arc. Electroplasma technologies of the new generation cause the need to design workable systems that provide control of technological processes and their dynamic optimization in real time. The improvement of any electroplasma technology begins with the improvement of the operating parameters of the main element of plasma installations - the power source. Goal is to build and study a continuous model of a pulsed source of secondary power supply, which works on an electric welding and plasma arc. Methodology. In the work, a mathematical description of the converter was performed. The continuous model of the system is substantiated, taking into account its features, namely, the load (gas-discharge gap) is a source of voltage and dynamic resistance. The parameters of the constant part during circuit synthesis are determined: the components of the gain of the constant part, the relative signal coefficient of the current sensor and the PWM gain. Studies of the open system «power source - arc» have been carried out. Results. MATLAB objects were created - continuous mathematical models of the object in the form of transfer functions. The obtained transient characteristics for different options: «arc current - control signal» and « inductor current - control signal» showed that open systems are unstable. It was found that in the case of instability, the filling frequency of self-oscillations occurring in the linear mode is close to the frequency of natural oscillations of the circuit. The dependence of the module and the argument of the input resistance of the power part of the pulsed power supply with parallel capacitance to the electric arc and without it, which have matching frequency characteristics, is established. The circuit considered with the initial data adopted in this article has a frequency transfer coefficient of the same type as the first-order non-minimum-phase (phase-shifting) link. Frequency response graphs for the output impedance of the power unit show that this power unit is a broadband frequency-selective system with a bandwidth of B0.707 = 100 kHz. Originality. Expressions for the frequency transfer function, input and output resistance of the pulse voltage converter operating on an arc load were obtained by the method of averaging and linearization. The frequency amplitude and phase characteristics for the pulse voltage converter with an LC filter and the output according to the arc current and the choke current were studied. The transfer functions of the continuous model in terms of arc current and choke current at the specified parameters are the same, which must be taken into account when designing regulators. Practical significance. The frequency characteristics of the input and output resistances and transfer functions can be used when forming a technical task for designing a power source to assess the stability of the «pulse converter - arc» system and rational calculation of input filters.

Data-driven analysis of parametrized acoustic systems in the frequency domain

A data-driven method combined with the formulations of boundary integral equations is developed for the frequency-domain analysis of parametrized acoustic systems, arising from the spatial discretization of the linear Helmholtz equation. The method derives surrogate models for the approximation of frequency response functions at selected field points via the construction of neural networks with radial basis function interpolation. This requires the offline collection of a training database consisting of discrete frequency-parameter samples and their associated response values, whereas the information about system matrices and interference with boundary element kernels are no longer necessary, leading to a matrix-free and non-intrusive nature. To ensure accurate fitting results, a tensor decomposition technique is employed to decouple the naturally formed tensor grid between the frequency and parameter inputs in the database. After establishing two sets of radial basis networks separately, the final reduced-order solutions as a continuous function of the frequency and parameters are represented by the linear combinations of tensor products. In the online phase, the original transfer function at any testing frequency-parameter location can be quickly predicted as direct output from the compact surrogate model. With the analytical solution, the traditional boundary element method and the fast multipole boundary element method as solvers for the generation of training data, two benchmark problems and one complex system are investigated. In all cases, the simplicity, versatility and efficiency of the proposed method are demonstrated through examples of multi-frequency solutions of acoustic systems with parametrized material and geometric properties.

Experimental realization of convolution processing in photonic synthetic frequency dimensions.

Convolution is an essential operation in signal and image processing and consumes most of the computing power in convolutional neural networks. Photonic convolution has the promise of addressing computational bottlenecks and outperforming electronic implementations. Performing photonic convolution in the synthetic frequency dimension, which harnesses the dynamics of light in the spectral degrees of freedom for photons, can lead to highly compact devices. Here, we experimentally realize convolution operations in the synthetic frequency dimension. Using a modulated ring resonator, we synthesize arbitrary convolution kernels using a predetermined modulation waveform with high accuracy. We demonstrate the convolution computation between input frequency combs and synthesized kernels. We also introduce the idea of an additive offset to broaden the kinds of kernels that can be implemented experimentally when the modulation strength is limited. Our work demonstrate the use of synthetic frequency dimension to efficiently encode data and implement computation tasks, leading to a compact and scalable photonic computation architecture.

Insight into the Long-Lasting Control Efficacy of Neonicotinoid Imidacloprid against Wheat Aphids during the Entire Growth Period.

Understanding the mechanism of long-lasting control efficacy of pesticides is important for developing sustainable high-efficacy pesticides, decreasing pesticide-use frequency and environmental input. This study investigates the long-term control mechanism of imidacloprid against wheat aphids under seed treatment. The concentrations of imidacloprid and its metabolites were 2.2-69.6 times lower than their individual LC50 after 238 days of treatment, and the control efficacy was still higher than 94.6%. The mixed bioactivity tests demonstrated that the insecticidal activity of the mixture of imidacloprid and its bioactive metabolites was approximately 1.5-189.7 times greater than that of a single compound against wheat aphids. The concentrations of imidacloprid, 5-hydroxy imidacloprid, and imidacloprid olefin in top flag leaves were 0.022, 0.084, and 0.034 mg/kg, respectively, during the aphid flourishing period, which were higher than the LC50 of the mixture (0.011 mg/kg), therefore providing long-lasting control efficacy. The study provides a first insight into the synergistic effects between a pesticide and its bioactive metabolites in ensuring long-term control performance.

Amplitude modulated feed-forward thermal drift compensation for linear and nonlinear current sensors

The linear and nonlinear temperature responses restrict the application of Hall current sensors operating in thermal power plants and industries. The rise in temperature of electron device-based measurement causes a significant error, leading to undesirable consequences for plant operation and relay coordination. This paper investigates four Hall current sensor types with linear and nonlinear temperature responses. The Hall current sensor, which receives the magnetic excitation from the permanent magnet, exhibits a linear temperature response, and the wire-wound design exhibits a nonlinear temperature response in the temperature range of 306–376 K. The solution scheme with amplitude modulation and thermal sensor integration with interdigitated electrode design having graphene and ZnO–KMnO4 compounds as the dielectric is also proposed. The use of amplitude modulation achieves input frequency immunity with a 0.03% K−1 improvement in the temperature response of the capacitive thermal sensor. Experimental observations confirm the validity of the thermal drift compensation scheme with a 20%–99% reduction of thermal drift error with a suitable choice of a thermal sensor.

Low-Power Process and Temperature-Invariant Constant Slope-and-Swing Ramp-Based Phase Interpolator

This article presents a process-and temperature-invariant high-resolution and highly linear low-power phase interpolator (PI) as an enabler for discrete-time spatial signal processors (SSPs) and for various mixed-mode RF transceiver architectures. Using current integration techniques, the proposed PI generates an adaptable constant slope-and-swing ramp signal to achieve significantly lower power suited for multiple antenna elements. Switched-capacitor-based bias generation enables tracking the ramp generator over process, voltage, and temperature enhancing the PI linearity. The 7-bit PI realized in the 65-nm CMOS technology can generate full delay range with a resolution of 4.88 ps at 1.6-GHz input frequency. The PI consumes a power of 503 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu$</tex-math> </inline-formula> W and occupies an active area of 0.021 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^2$</tex-math> </inline-formula> with a jitter of 0.410 ps for a 1.6-GHz operation and measured DNL and INL of 0.52 and 0.52 LSB, respectively.

Design of RF energy harvester for 700 MHz

Abstract Radio frequency energy harvester is the conversion of ambient radio frequency electromagnetic waves into usable electrical energy, powering low-power devices without traditional power sources. In this paper, a novel RF energy harvester is proposed for 700 MHz frequency band. For the purpose of rectification, a Greinacher voltage rectifier cum multiplier is used in the circuit and Schottky Diode HSMS-2852 is used for implementing a rectifier. The LC impedance matching is implemented to improve the circuit performance of the harvester including conversion efficiency and output voltage. Simulation of the rectifier is done using the PathWave Advanced Design System (ADS) software. The rectifier shows the optimized performance at 5 kΩ load impedance. Simulation results show the highest efficiency of 33.1 % and an output voltage of 3.2 V with 8 dBm RF power at 700 MHz input frequency.

Performances of Multi-Configuration Piezoelectric Connection with AC-DC Converter in Low Frequency Energy Harvesting System

Harvesting energy by capturing vibration from low frequency energy have been explored extensively. In essence, a single piezoelectric transducer or an array of piezoelectric connections are used to convert kinetic energy into electrical energy in order to produce low frequency energy. In this paper, multi-configuration array piezoelectric connections are used to investigate the performances of different converter circuit types in low energy harvesting applications. This research utilized three pieces of circular piezoelectric sensor to test the combinations of array connection. There are four options for the piezoelectric sensor configuration: parallel (P), series (S), parallel-series (PS), and series-parallel (SP) while the full wave bridge rectifier (FWBR), parallel voltage multiplier (PVM), and parallel Synchronized Switch Harvesting on Inductor (P-SSHI) converter circuit are chosen AC-DC converter circuits. The system is assessed using a variety of load configurations, including 10 kΩ and 1 MΩ with a 3 Hz input frequency. In order to produce the highest possible output of collected power, the observation focuses on identifying the ideal combination of array piezoelectric connections with AC-DC converter. The result shows that 3-Parallel (3P) piezoelectric connection obtained a higher power output among the other types of array piezoelectric which was 5.97μW. The FWBR circuit generated the highest output power with 2.42μW for a combination of piezoelectric sensors array of 3P connection with the AC-DC converter.

Choosing optimal input and sampling frequencies for analog to digital converter testing

The main objective of this paper is to study of the ideal input and sampling frequencies, as well as determining the necessary number of samples for achieving coherent sampling. This aspect holds significant importance when it comes to testing analog-to-digital converters (ADCs) using various techniques such as the Histogram Test Method, Discrete Fourier Transform Method, or Sine-Fitting Method. The study conducted in this paper sheds light on a crucial consideration, which is the trade-off between testing duration and the proximity to the required frequencies. This trade-off is determined by the number of acquired samples. The balance between the amount of time spent on testing and the accuracy achieved in terms of the frequencies being targeted is of great importance. By exploring the ideal input and sampling frequencies, along with the determination of the necessary number of samples for coherent sampling, this research contributes to enhancing the understanding of ADC testing methodologies. It provides valuable information for researchers and practitioners in the field, enabling them to make informed decisions regarding the selection of appropriate testing techniques and algorithms based on their specific requirements and constraints. Ultimately, the findings presented in this paper have the potential to improve the efficiency and effectiveness of ADC testing processes, leading to more accurate and reliable results.

An Alternative Method to Analyze Waveforms from Bender Element Tests in Soft Clays

Bender element (BE) testing has become a widely used technique to evaluate S-wave velocities and to derive shear moduli from them in laboratory tests. Results of BE tests depend heavily on the proper identification of the S-wave travel time from waveforms often affected detrimentally by factors such as the near-field effect, crosstalk, noise, or drift. The authors have performed BE tests on soil specimens of Texcoco Clay over the last few years in triaxial cells and oedometers and have sometimes dealt with waveforms influenced by those undesirable factors thus, it was observed that the using of different available techniques to evaluate the S-wave travel time are often prone to errors. This paper shows that the S-wave travel time can be assessed unambiguously from the distance between the inflection points present in both the source and the received signals when waveforms generated with different input frequencies are superimposed, even in signals affected by the near-field effect, crosstalk, noise, or drift. This approach, named here the Wave Inflection Method (WI method), yields good results, at least when applied to data obtained from BE tests on soft Texcoco Clays. The method was validated by applying it to synthetic signals and experimental waveforms obtained from triaxial and oedometer tests equipped with BE. When applied to previously published waveforms on a wide range of soil types, our results suggest that the WI method significantly reduces subjectivity and produces improved reliability in evaluating the S-wave travel time.

A novel time delay‐based phase‐locked loop with improved anti‐harmonic interference performance for grid synchronization

SummaryThe time delay unit‐based PLLs (TD‐PLLs) are widely used in grid synchronization in single‐phase power systems. However, the TD‐PLL is vulnerable to frequency variations and harmonic disturbances, leading to grid synchronization failures. Analysis shows that the performance degradation is due to the inability to obtain the variation of the input signal frequency. This paper proposes a new time delay‐based phase‐locked loop called immune to double frequency component TD‐PLL (IDFC‐TD‐PLL) based on a feedback structure to accurately capture the variation of input signal frequency, which can improve the dynamic performance and the performance against harmonic interference. Simulations and experiments have evaluated the performance of the proposed phase‐locked loop, demonstrating its superior accuracy and dynamic performance compared to the phase‐locked loops referred in the paper.

Mental Tasks Modulate Motor-Units Above 10 Hz and are a Potential Control Signal for Movement Augmentation: a Preliminary Study.

Spinal motor neurons receive a wide range of input frequencies. However, only frequencies below ca. 10 Hz are directly translated into motor output. Frequency components above 10 Hz are filtered out by neural pathways and muscle dynamics. These higher frequency components may have an indirect effect on motor output, or may simply represent movement-independent oscillations that leak down from supraspinal areas such as the motor cortex. If movement-independent oscillations leak down from supraspinal areas, they could provide a potential control signal in movement augmentation applications. We analysed high-density electromyography (HD-EMG) signals from the tibialis anterior muscle while human subjects performed various mental tasks. The subjects performed an isometric dorsiflexion of the right foot at a low level of force while simultaneously (1) imagining a movement of the right foot, (2) imagining a movement of both hands, (3) performing a mathematical task, or (4) performing no additional task. We classified the channel-averaged HD-EMG signals and the cumulative spike train (CST) of motor-units using a filter bank and a linear classifier. We found that in some subjects, the mental task can be classified from the channel-averaged HD-EMG signals and the CST in oscillations above 10 Hz. Furthermore, we found that these oscillation modulations are incompatible with a systematic and task-dependent change in force level. Our preliminary findings from a limited number of subjects suggest that some mental task-induced oscillations from supraspinal areas leak down to spinal motor neurons and are discriminable via EMG or CST signals at the innervated muscle.

Welsh–English bilingual adolescents’ performance on verbal analogy and verbal classification tasks: the role of language exposure and use on vocabulary knowledge

ABSTRACT Numerous studies suggest that bilinguals demonstrate smaller vocabularies than monolinguals, and that bilinguals’ breadth of vocabulary knowledge – both expressive and receptive – is linked to input frequencies in each language [e.g. Hoff, E., S. Welsh, S. Place, and K. Ribot. 2014. “Properties of Dual Language Input That Shape Bilingual Development and Properties of Environments That Shape Dual Language Input.” In Input and Experience in Bilingual Development, edited by T. Grüter, and J. Paradis, Vol. 13, 119–140. Amserdam: John Benjamins]. However, relatively little is known about the quality of bilinguals’ knowledge of the words they do know (e.g. their understanding of how words relate to each other semantically) and how input frequencies influence that knowledge. Using the Cognitive Abilities Tasks – 4 (CAT-4), this study explored the potential links between three types of input sources – home language exposure, self-reported rates of language use in general, and language use with friends – and bilinguals’ performance on two types of vocabulary tests in both Welsh and English: verbal analogy and verbal categorisation. Results revealed similar performance across-the-board in relation to their knowledge of English vocabulary, regardless of their exposure to and use of Welsh and/or English in general and with friends, but their knowledge of the links between words in Welsh was related to home language exposure and rates of language use. The implications and application of these results in practice are discussed.

Building Intelligence in the Mechanical Domain—Harvesting the Reservoir Computing Power in Origami to Achieve Information Perception Tasks

Herein, the cognitive capability of a simple, paper‐based Miura‐ori—using the physical reservoir computing framework—is experimentally examined to achieve different information perception tasks. The body dynamics of Miura‐ori (aka its vertices displacements), which is excited by a simple harmonic base excitation, can be exploited as the reservoir computing resource. By recording these dynamics with a high‐resolution camera and image processing program and then using linear regression for training, it is shown that the origami reservoir has sufficient computing capacity to estimate the weight and position of a payload. It can also recognize the input frequency and magnitude patterns. Furthermore, multitasking is achievable by simultaneously applying two targeted functions to the same reservoir state matrix. Therefore, it is demonstrated that Miura‐ori can assess the dynamic interactions between its body and ambient environment to extract meaningful information—an intelligent behavior in the mechanical domain. Given that Miura‐ori has been widely used to construct deployable structures, lightweight materials, and compliant robots, enabling such information perception tasks can add a new dimension to the functionality of such a versatile structure.

A microwave comb generator based on AlGaN/GaN heterostructure Schottky diodes nonlinear transmission line

We report a microwave nonlinear transmission line (NLTL) based on AlGaN/GaN Schottky-barrier diodes. As a comb generator, the NLTL produces a frequency comb from 4 to 40 GHz at an input frequency of 4 GHz. The power of harmonics from 28 to 40 GHz exceeds that of commercial GaAs NLTL at an input power of 26 dBm. The power of harmonic starts to saturate as the input power increases to 33 dBm. Compared with the maximum input power of 26 dBm of commercial GaAs NLTLs, the comb generator based on AlGaN/GaN NLTL is more advantageous at a high input power.