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This study examines the extraction of small-signal equivalent circuit parameters, linearity and intermodulation metrics, and capacitance–voltage characteristics for both AlGaN and GaN channel HEMTs. Compared to GaN channel HEMTs, AlGaN channel HEMTs have better linearity and intermodulation distortion. In the instance of AlGaN channel HEMTs, the device parasitics are decreased. Additionally, the effect of graded AlGaN buffer layer thickness on breakdown characteristics and linearity is examined. For breakdown characteristics, the 200 nm-graded AlGaN buffer layer thickness yields superior results with VBOff 157 V for a thickness of 200 nm (147 V in the case of 500 nm). At 200 nm thickness, the linearity and intermodulation distortion FOMs are also reasonably good, and the remaining device properties are essentially unchanged. Hence, the graded AlGaN buffer thickness can be reduced for high-voltage applications. For higher-voltage applications, the graded AlGaN buffer thickness can, therefore, be decreased. [ABSTRACT FROM AUTHOR]

This research exclusively presents a short-channel III–V heterojunction tunnel field-effect transistor (TFET) featuring a high-κ gate dielectric. The study includes a comprehensive comparison of direct-current (DC) performance, analog/radio-frequency (RF) characteristics, and linearity distortion analysis with a Ge-source-based TFET. To optimize the device behavior, heterojunctions based on InGaAs and SiGe materials are considered over the Ge-source and Si-source TFET to improve the tunneling mechanism. The transfer characteristics of the proposed device have been acquired and elucidated using different device parameters. The reported device structure achieves I ON / I OFF = 1.4 × 10 13 and subthreshold swing of 12.3 mV/decade. Analog and RF characterization of the proposed device involves in-depth analysis of various parameters such as transconductance, parasitic capacitance, cutoff frequency, and other linearity distortion parameters. These specific aspects are thoroughly illustrated to provide a comprehensive understanding of the device performance in analog and RF applications. The findings also indicate that the heterojunction TFET device showcases reduced transconductance derivatives, decreased intermodulation distortion-3, and enhanced voltage intercept points. There is an increase in the input intercept point-3, indicating improved linearity performance and a reduction in distortion for the device. It is thus concluded that the heterojunction TFET is a viable choice for applications requiring low power, high speed, and stable performance. [ABSTRACT FROM AUTHOR]

Ferroelectric devices have traditionally been utilized in memory circuits due to their ability to retain a polarization charge and potentially act as a nonvolatile storage device. Their usage in applications unrelated to memory has also previously expanded into other digital and analog circuits, and now, it is being investigated in radio frequency circuits. This work explores the implementation of a frequency mixer using ferroelectric field-effect transistors in order to demonstrate stability against voltage offsets in a single-balanced mixer, making use of the polarization in the switching transistors to improve the performance of the second-order intermodulation product. [ABSTRACT FROM AUTHOR]

This paper presents a new behavioural mixer model in a multi-box structure. In the proposed model, as well as amplitude and phase nonlinearity, the memory effect is also modelled. The multi-box structure is constructed in line with the Hammerstein model to characterise both fundamental signals, intermodulation distortion (IMD) and harmonic distortion (HD) for mixers in particular and all frequency translating devices in general. A testbed is constructed to measure both amplitude and phase characteristics. A good match between the measured and the calculated results is obtained using curve fitting and optimisation algorithms. In order to model the memory effect, a finite impulse response (FIR) filter is used. The measured IM3 imbalance is successfully modelled with this filter. For fundamental components, amplitude and phase errors are less than 0.1 dB and 1 degree, respectively. For IM3 components, amplitude and phase errors are less than 4 dB and 10 degrees, respectively. For the overall accuracy of the model, measurements are conducted with two-tone and modulated signals, and normalised mean square error (NMSE) values are calculated as −31.5 dB and −29.3 dB, respectively. The results are obtained for a wide range of input power span, including the compression region where nonlinearity is strongly pronounced. The proposed model is capable of accurately representing nonlinearity and memory effect for mixers and frequency translating devices in general and thus may be used for system-level modelling and linearisation applications. [ABSTRACT FROM AUTHOR]

We explore the relationship between rough surface conductors and the phenomenon of passive intermodulation. The underlying surface is taken to be the boundary of a Lipschitz domain, and a characteristic angle of the domain is used to track boundary dependence on the various fields. To model electro‐thermal passive intermodulation in particular, we consider a specific type of temperature‐dependent conductivity and determine conditions on the conductivity under which one can use fixed point arguments to solve an induction heating and Joule heating problem on a Lipschitz domain. In the latter problem, we also consider a time‐dependent permittivity function ε$\varepsilon$. Finally, weak solutions to a magneto‐quasi‐static problem are obtained when the permeability µ is temperature dependent and is allowed to degenerate in a certain way. An interesting effect of the rough surface is the inherently limited Sobolev regularity of the electric field, which can be improved if one assumes additional constraints on the boundary. [ABSTRACT FROM AUTHOR]

This article proposes a new nonlinear behavioral analysis of the Spice diode model by using Volterra series theory, in which the expression of the third‐order intermodulation was expressed. Moreover, the impact on the behavior of diode CV characteristic parameters Zero‐bias Junction capacitance Cjo, gradient coefficient M, and built‐in potential Vj are discussed. Two‐tones harmonic balance simulations are performed with the hpeesofsim circuit simulator. Results are consistent with the Volterra series analysis, showing the rationality and validity of this behavioral modeling method. [ABSTRACT FROM AUTHOR]

Abstract Skeletal muscle is the largest metabolic organ of the human body. Maintaining the best quality control and functional integrity of mitochondria is essential for the health of skeletal muscle. However, mitochondrial dysfunction characterized by mitochondrial dynamic imbalance and mitophagy disruption can lead to varying degrees of muscle atrophy, but the underlying mechanism of action is still unclear. Although mitochondrial dynamics and mitophagy are two different mitochondrial quality control mechanisms, a large amount of evidence has indicated that they are interrelated and mutually regulated. The former maintains the balance of the mitochondrial network, eliminates damaged or aged mitochondria, and enables cells to survive normally. The latter degrades damaged or aged mitochondria through the lysosomal pathway, ensuring cellular functional health and metabolic homeostasis. Skeletal muscle atrophy is considered an urgent global health issue. Understanding and gaining knowledge about muscle atrophy caused by mitochondrial dysfunction, particularly focusing on mitochondrial dynamics and mitochondrial autophagy, can greatly contribute to the prevention and treatment of muscle atrophy. In this review, we critically summarize the recent research progress on mitochondrial dynamics and mitophagy in skeletal muscle atrophy, and expound on the intrinsic molecular mechanism of skeletal muscle atrophy caused by mitochondrial dynamics and mitophagy. Importantly, we emphasize the potential of targeting mitochondrial dynamics and mitophagy as therapeutic strategies for the prevention and treatment of muscle atrophy, including pharmacological treatment and exercise therapy, and summarize effective methods for the treatment of skeletal muscle atrophy.

This paper presents a generalized vibration-based multiple breathing crack localization technique in beams with an unknown number of cracks based on Singular Spectrum Analysis (SSA). Localization of multiple breathing cracks is a highly challenging inverse problem, as all these breathing cracks (more than two) might be in a similar state (either opening or closing state) at any particular time instant or in contrasting states (while some breathing cracks are opening, others in closing state) during vibration. The level of nonlinearity of vibration response is strongly dependent not only on each crack size, and location but also on the application of driving force along the cracked beam. The concept of varied input frequency excitation sources is employed in the present work for multiple breathing crack identification over the tedious traditional approach of varying input force application positions. The major advantage of using singular spectrum analysis in the present work is that it can reliably isolate and extract the very low-amplitude nonlinear sensitive components (super harmonics and intermodulation) being buried in the total response based on the pairwise eigenvalue property of harmonic components. Investigations have been carried out by varying the number, spatial locations, and also intensities of the breathing cracks. Sensitivities associated with measurement noise and also with limited sensors are also investigated. The results of both numerical and experimental investigations carried out in this paper concluded that the proposed SSA can effectively localize closely spaced or sparsely spaced (i.e.,, spatially far apart) multiple cracks in the beam. The proposed SSA approach is data-driven, works with limited sensors, and does not need reference healthy state measurements. [ABSTRACT FROM AUTHOR]

Numerical analysis of Transistor Laser is carried out to investigate the influence of Franz-Keldysh (F-K) Effect on the non-linear distortion characteristics such as intermodulation (IM). The device considered for the study incorporates an intrinsic GaAs absorption layer in the collector–base junction of a TL emitting around 980 nm. The base current threshold is obtained as 39 mA for the collector to base voltage of 1 V and it is discerned that the threshold current of TL is dependent on electric field in addition to the bias current. The analytical solution of rate equations at steady state is derived and compared with the numerical simulation and the same is plotted for VCB = 1 V. Moreover, maximum optical light output loss of 12 mW and 1.37 mA additional current is contributed to the collector current for collector base voltage of 3 V, under various base currents due to F-K effect. The modulation bandwidth (f-3 dB) of TL under voltage modulation is obtained as 9.63 GHz. While, under current modulation, it is found as 8.38 GHz respectively. A maximum modulation depth of 86% is obtained for IB = 1.06Ith, at 2.4 GHz. The frequency components related to intermodulation product, IMD3 (2.15 GHz) magnitudes are obtained as − 10.26 dBc, − 12.37 dBc, − 13.54 dBc and − 15.92 dBc for VCB voltage value of 0 V, 1 V, 2 V and 3 V respectively. The intermodulation product, IMD5 (2.05 GHz) magnitudes are obtained as − 18.89 dBc, − 25.76 dBc, − 28.22 dBc and − 36.05 dBc for the collector bias voltage (VCB) value of 0 V, 1 V, 2 V and 3 V respectively. In both cases, the intermodulation is found to decrease with increase in F-K absorption. [ABSTRACT FROM AUTHOR]

Aiming at the quantitative evaluation requirements of radar second-order intermodulation false alarm (SIFA) effect, a radar SIFA effect model is established from the field-circuit coupling mechanism, and the parameter test method of the model is given. Taking a certain type of radar as the test object, the SIFA effect test is carried out by using the method of electromagnetic injection equivalent substitution irradiation. The results show that the tested radar will produce a SIFA signal higher than the selected sensitive level when the frequency difference of dual-frequency electromagnetic interference (EMI) is within 3 MHz and the frequency offset is within ±200 MHz. Using the model parameters of the SIFA interference effect measured in the experiment, it is assumed that they do not change with the interference field strength. Combined with the SIFA interference field strength of the tested radar and the single frequency blocking critical interference field strength, the effect model can evaluate the degree of radar SIFA interference. [ABSTRACT FROM AUTHOR]

This paper addresses the issue of sidelobe imbalance due to spurious coupling in quasi-elliptic filters designed in groove gap waveguide (GGW) technology using TE102 overmoded cavity based resonator to realize the cross coupling in the cascaded quadruplet topology. The filter is designed at 38 GHz with 750 MHz bandwidth (1.97% fractional bandwidth) to demonstrate its potential as a narrowband, high-power output filter at mm-wave frequencies in next-generation high throughput satellites. The filter is designed for production yield avoiding any complex structures to realize the negative cross coupling and using an all-capacitive iris structure. Systematic studies have been performed to identify and mitigate the sidelobe imbalance issue, and a final design has been proposed with a very low (< 1 dB) sidelobe imbalance. The measured results of the realized hardware closely match simulated ones. The proposed design configuration is an ideal filter option for next generation SATCOM applications as it provides benefits of narrowband symmetrical frequency response with low insertion loss, sharp near band rejection, and high-power handling capability along with the benefits of gap waveguide technology in terms of ease of fabrication, low passive intermodulation (PIM) level, and low sensitivity towards surface imperfections and misalignment [ABSTRACT FROM AUTHOR]

Nonlinear detection is a technique that detects nonlinear interactions, such as harmonics and intermodulation, caused by semiconductor junctions, enabling the remote detection of nonlinear objects, such as small electronic devices with small radar cross-sections. The characteristics of such nonlinear radars enable the effective detection of targets equipped with small electronic devices in camouflaged and concealed environments, particularly in security and military applications. Therefore, this study constructs a nonlinear radar system utilizing FMCW to effectively detect the nonlinear response of small electronic devices at long distances. Using the constructed system, four small electronic devices, and manufactured nonlinear targets, successful detection was confirmed at a line-of-sight condition of 10 m, and even at a nonline-of-sight condition of 6 m. [ABSTRACT FROM AUTHOR]

Skeletal muscle is the largest metabolic organ of the human body. Maintaining the best quality control and functional integrity of mitochondria is essential for the health of skeletal muscle. However, mitochondrial dysfunction characterized by mitochondrial dynamic imbalance and mitophagy disruption can lead to varying degrees of muscle atrophy, but the underlying mechanism of action is still unclear. Although mitochondrial dynamics and mitophagy are two different mitochondrial quality control mechanisms, a large amount of evidence has indicated that they are interrelated and mutually regulated. The former maintains the balance of the mitochondrial network, eliminates damaged or aged mitochondria, and enables cells to survive normally. The latter degrades damaged or aged mitochondria through the lysosomal pathway, ensuring cellular functional health and metabolic homeostasis. Skeletal muscle atrophy is considered an urgent global health issue. Understanding and gaining knowledge about muscle atrophy caused by mitochondrial dysfunction, particularly focusing on mitochondrial dynamics and mitochondrial autophagy, can greatly contribute to the prevention and treatment of muscle atrophy. In this review, we critically summarize the recent research progress on mitochondrial dynamics and mitophagy in skeletal muscle atrophy, and expound on the intrinsic molecular mechanism of skeletal muscle atrophy caused by mitochondrial dynamics and mitophagy. Importantly, we emphasize the potential of targeting mitochondrial dynamics and mitophagy as therapeutic strategies for the prevention and treatment of muscle atrophy, including pharmacological treatment and exercise therapy, and summarize effective methods for the treatment of skeletal muscle atrophy. [ABSTRACT FROM AUTHOR]

Orthogonal frequency division multiplexing technology, as a key technology of NR air interface transmission, has the advantages of resisting frequency selective fading and narrowband interference, but the problem of high peak-to-average power ratio (PAPR) is easy to cause semiconductor devices to work in the nonlinear region. There are serious problems with intermodulation component, in-band interference, and out-band spectrum regeneration. Especially in NR 3GPP R15 protocol, the PAPR of the demodulation reference signal symbol is further increased when the three or four-layer beamforming is carried out based on the precoding matrix indicator (PMI) mode. The paper analyzes the cause of this problem, theoretically. And in order to solve the above problem, a rotation factor algorithm based on step gradient is proposed. The simulation results show that the algorithm can effectively reduce the PAPR of DMRS symbol in PMI mode without affecting the demodulation performance of data symbols and is easy to implement in engineering with low computational complexity. [ABSTRACT FROM AUTHOR]

We study magneto-optical coupling in a ferrimagnetic sphere resonator made of yttrium iron garnet. We find that the resonator can be operated in the telecom band as a polarization-selective optical modulator. The input state of polarization (SOP) contributing to the Stokes sideband is orthogonal to the one contributing to the anti-Stokes sideband. In the region of single sideband modulation, the SOP of both sidebands is nearly orthogonal to the SOP of the incident light. Intermodulation gain can be employed in the nonlinear regime for amplification. [ABSTRACT FROM AUTHOR]

The design and the characterization of a non-linear target to test an intermodulation radar was performed using the AWR design environment Version 22 by Cadence software. Two experimental setups for intermodulation measurements were realized in order to characterize connectorized or antenna-equipped devices. Both setups were modeled using the VSS software available inside AWR Version 22. The comparison between measurements and simulations on the designed target showed a very good agreement. Intermodulation measurements were performed on connectorized devices present inside electronic systems and on various transceiver available on the market. This experimental study evidenced that the non-linearities of devices such as amplifiers and mixers are visible at their access ports even when the device is switched off. Moreover, this study highlights the ability of an intermodulation radar to remotely detect the presence of a particular transceiver, even when the latter is switched off, thanks to the specific frequency response of its intermodulation products. [ABSTRACT FROM AUTHOR]

With the development of communication technology, the interference from passive intermodulation to the communication system has become increasingly severe. Locating the source of passive intermodulation and then repairing or replacing the device experiencing passive intermodulation is a reliable method. Therefore, this paper proposes a dual-frequency signal localization method based on the principle of phase ranging to accurately locate the passive intermodulation sources in RF cables. This method switches the test signal frequency to obtain the phase of passive intermodulation signals at different frequencies to localize the passive intermodulation source. This paper analyzes the principle of the passive intermodulation localization method based on dual-frequency signals, establishes a localization system for experiments, and finally, analyzes the experimental error to propose an optimization strategy. Through experimental verification, this method can stabilize the positioning error of a passive intermodulation source in a transmission line less than 0.06 m. Meanwhile, this method has high positioning accuracy and the advantages of slight computational complexity, fast positioning speed, and only a small number of requirements on hardware resources. It can work in communication scenarios like satellite and base stations, providing a new technical solution for localizing passive intermodulation interference sources in 5G and 6G communication systems. [ABSTRACT FROM AUTHOR]

We describe a technique to optimize the dynamic performance of microwave SQUID multiplexer (µMUX)-based systems. These systems proved to be adequate for reading out multiple cryogenic detectors simultaneously. However, the requirement for denser detector arrays to increase the sensitivity of scientific experiments makes its design a challenge. When modifying the readout power, there is a trade-off between decreasing the signal-to-noise ratio (SNR) and boosting the nonlinearities of the active devices. The latter is characterized by the spurious free dynamic range (SFDR) parameter and manifests as an increment in the intermodulation products and harmonics power. We estimate the optimal spectral location of the SQUID signal containing the detector information for different channels. Through the technique, what we refer to as Spectral Engineering, it is possible to minimize the SNR degradation while maximizing the SFDR of the detector signal, thus, overcoming the trade-off. [ABSTRACT FROM AUTHOR]

High bit rate modulation is an essential aspect of next-generation WiFi and plays a crucial role in achieving high data rates and increased network capacity. high-bit rate modulation uses advanced modulation schemes, such as 4096-QAM, to increase the maximum number of bits sent over a particular frequency band. Using nonlinear amplifiers in wireless communication systems will significantly improve the performance of high bit rate modulation techniques, such as 4096-QAM. Nonlinear amplifiers can cause a range of impairments, including intermodulation, harmonic distortion, and amplitude compression, which can affect the transmitted signal quality. It is essential to minimize the effects of these impairments through proper design and optimization of the amplifier to ensure the highest quality possible of the transmitted signal. In this paper, M-QAM with nonlinear amplifier system design and implanted with MATLAB Simulink where in terms of Transmitted and Received spectrum signal and constellation diagram and calculated error vector magnitude (EVM) and modulation error ratio (MER) measurements for 1024, 2048, and 4096-QAM that used in WiFi 6, WiFi 6E, WiFi 7, respectively. [ABSTRACT FROM AUTHOR]

Traveling Wave Tubes (TWT) are most widely used in civil, defense, and space applications as power amplifiers over a wide range of frequency. When a TWT works at a higher bandwidth, it suffers from nonlinearities, which affects the overall performance of the tube and hence the required results aren't achieved. So, optimization of a TWT is required, mainly in terms of its power characteristics. Power characteristics of the TWTs are specified in terms of output power at different input drive levels, AM/PM transfer and AM/PM conversions, input, and output back-off, gain at saturation, etc. Some of the linearity factors like 3rd order inter modulation product (IMP), and the 1 dB compression point are also optimized. An exhaustive study has been made to achieve the optimum performance of a 140W TWT in Ku-Band. The result has been validated by experimental results.

We present a new open-loop implementation of Kelvin probe force microscopy (KPFM) that provides access to the Fourier spectrum of the time-periodic surface electrostatic potential generated under optical (or electrical) pumping with an atomic force microscope. The modulus and phase coefficients are probed by exploiting a double heterodyne frequency mixing effect between the mechanical oscillation of the cantilever, modulated components of the time-periodic electrostatic potential at harmonic frequencies of the pump, and an ac bias modulation signal. Each harmonic can be selectively transferred to the second cantilever eigenmode. We show how phase coherent sideband generation and signal demodulation at the second eigenmode can be achieved by using two numerical lock-in amplifiers configured in cascade. Dual-heterodyne KPFM (DHe-KPFM) can be used to map any harmonic (amplitude/phase) of the time-periodic surface potential at a standard scanning speed. The Fourier spectrum (series of harmonics) can also be recorded in spectroscopic mode (DHe-KPFM spectroscopy), and 2D dynamic images can be acquired in data cube mode. The capabilities of DHe-KPFM in terms of time-resolved measurements, surface photovoltage (SPV) imaging, and detection of weak SPV signals are demonstrated through a series of experiments on difference surfaces: a reference substrate, a bulk organic photovoltaic heterojunction thin film, and an optoelectronic interface obtained by depositing caesium lead bromide perovskite nanosheets on a graphite surface. The conclusion provides perspectives for future improvements and applications.

This paper presents measurement of third order intermodulation distortion and third order intercept (TOI) in a Fabry–Perot semiconductor laser lasing at 1550.3 nm when the laser is biharmonically bias-current modulated. Keeping the modulation current of one signal fixed, the third order intermodulation power at two different frequencies has been found to increase with the increase in second signal modulation power. There is an eventual crossover or tendency to crossover in the intermodulation characteristics when the modulation current amplitudes of the channels assume the same value. The TOI has been experimentally measured. The intermodulation power appearing at two different frequencies along with their signal power dependence and measurement of TOI constitute the outcome of this paper. The typical value of spurious-free dynamic range of the modulation scheme is 70 dB. [ABSTRACT FROM AUTHOR]

Ultra-wideband (UWB) applications require lowpower and low-noise amplifiers (LNAs) that can operate over a wide frequency range. However, conventional LNAs often suffer from poor linearity and high-power consumption. This research work proposes a novel LNA design that uses the adjusted derivative superposition (DS) technique and feedback to improve the linearity and reduce the power consumption of UWB LNAs. The DS technique enhances the third-order intermodulation (IM3) cancellation by adjusting the bias currents of the transistors, whereas the feedback improves the stability and input matching of the LNA. The LNA is implemented using a degenerated common source topology in a 180 nm standard CMOS technology. The simulation results show that the LNA achieves a power gain of 10-12.2 dB, an input thirdorder intercept point (IIP3) of about 12 dBm, and a noise figure of less than 2.5 dB over the UWB frequency band of 3.1-10.6 GHz. The input reflection coefficient is less than -10 dB, and the power consumption is 11.6 mW with a 1.5 V power supply. The designed LNA offers a novel and innovative solution for UWB applications that significantly improve the performance and efficiency of UWB LNAs whereas reducing the cost and complexity of implementation. [ABSTRACT FROM AUTHOR]

This paper presents a generalized time domain-based multiple breathing crack localization technique in beams with an unknown number of cracks based on Quadratic-Teager Kaiser Energy (Q-TKE) using vibration data. Localization of multiple breathing cracks is a highly challenging inverse problem, as all these breathing cracks (more than two) might be in a similar state (either opening or closing state) at any particular time instant or in contrasting states (while some breathing cracks are opening, others are in closing state) during vibration. The level of nonlinearity of vibration response is strongly dependent not only on each crack size and location but also on the application of driving force along the cracked beam. The concept of varied input frequency excitation sources is employed in the present work for multiple breathing crack identification over the tedious traditional approach of varying input force application positions. The major advantage of using Q-TKE in the present work is that it can reliably isolate and extract the very low-amplitude nonlinear sensitive components (superharmonics and intermodulation) being buried in the total response and enhance them in the time domain signal itself. Investigations have been carried out by varying the number, spatial locations, and also intensities of the breathing cracks. Sensitivities associated with measurement noise and also with limited sensors is also investigated. The results of both numerical and experimental investigations carried out in this paper concluded that the proposed Q-TKE can effectively localize closely spaced or sparsely spaced (i.e., spatially far apart) multiple cracks in the beam. The proposed Q-TKE approach is data-driven, works with limited sensors, and does not need reference healthy state measurements. [ABSTRACT FROM AUTHOR]

Abstract A novel method for modelling the passive intermodulation (PIM) in radio frequency (RF) devices, which works as a complex non‐linear system, was proposed. Both behaviour modelling and experimental validation were introduced to clarify the generation of PIM in a parallel and series non‐linear system. Taking the coaxial connector as an example, two types of N‐type connectors with 4 and 6 contact petals were selected and put into research. The measurements both agree well with the predicted results, validating the proposed model.

In this paper, an Integrated Phase Linearizer (IPL) technique is designed to improve the linearity performance of a CMOS power amplifier (PA). The IPL is integrated at the gate of the PA so that the effect of the parasitic gate-to-source ( C gs ) capacitance of the main transistor is compensated by the linearizer. Thus, it improves the 3rd-order intermodulation point (OIP3) without trading-off the power added efficiency (PAE). The proposed solution is designed and fabricated in an 180 nm CMOS technology process consuming the chip area of 2.25 mm2. At the operating frequency of 2.45 GHz, it exhibits a gain of 11.14 dB with unconditional stability characteristics from 1 GHz to 10 GHz. Biased quiescent current of 19.35 mA, the IPL-PA delivers a maximum output power of 15.20 dBm with 40.86% peak PAE, 34.91 dBm of peak OIP3 and maximum power consumption of 63.65 mW at 2.45 GHz with supply voltage headroom of 1.8 V. The proposed linearization scheme proved to be an excellent solution for low-power transceivers integration. [ABSTRACT FROM AUTHOR]

This paper proposes a compact K-band dual-circularly polarized antenna that can be implemented on a non-linear tag based on third-order intermodulation (IM3) for bio-sensing applications. The proposed antenna has the characteristics of being low-profile and lightweight, with opposite circular polarizations (CP) between ports. The non-linear tag-based bio-sensing scenario utilizes K-band millimeter wave frequencies, which allows for compact non-linear tags for attachment to the body. Also, the proposed antenna features dual-CP, which are for the reception and re-radiation of incident transmit signals and the IM3 responses, respectively. To this end, a two-port traveling-wave series-fed patch array with coplanar proximity coupling is designed. Here, to minimize the size of the antenna, we use only four circular patch elements with a modified diamond-shaped microstrip feedline. Through simulation and measurement, we demonstrate that the proposed antenna has an axial ratio of less than 3 dB from 23.25 GHz to 24.1 GHz, with the reflection coefficients below −10 dB and port-to-port coupling below −15 dB. These results indicate the potential utility of the proposed antenna as a tag antenna for non-linear detection-based bio-sensing applications. [ABSTRACT FROM AUTHOR]

This paper presents a novel test platform for passive intermodulation measurement on planar microwave circuits using a filter design strategy. A finger planar band-pass filter is proposed and optimized to have an evenly distributed stimulation field on the surface. The layout is optimized with symmetrical coupling lines from two directions, and the feed line is with a tapered transformer. A pair of T-type resonators is adopted to improve the atness of the field distribution. In the application of this test platform, print circuit boards with different layouts are tested, and the passive intermodulation difference of different layouts can be differentiated. As this platform is an open space, the device under test can be easily replaced without suspending the passive intermodulation test system, which can be applied in the production line to speed up the production quality inspection. [ABSTRACT FROM AUTHOR]

The effect of load-pull on 3rd order intermodulation (IM3) radiation characteristics of a transmitting active phased array is studied and a general model for predicting the spatial distribution of fundamental tones and intermodulation products is introduced. The used data is obtained from a load pull measured amplifier prototype and a simulated linear antenna array, which are used in co-simulation of the system behavior. The system is optimized for maximum main tone beam powers with a two-tone excitation while satisfying a signal-to-IM3 ratio (SI3R) of 40 dB. In this paper, we demonstrate the case, where two separate beams are scanned independently from each other. The used load-pull system model achieves on average an improvement of 10.4 dB for SI3R, when compared to traditional small-signal modelling, while decreasing the main beam power densities by only 0.3 dB when compared to traditional small-signal modelling. Optimizing for SI3R degrades beam pattern by increasing beamwidths and decreasing sidelobe levels (SLL).

Passive intermodulation (PIM) is usually expressed by the third‐order intermodulation power excited by two‐tone signal, which has limitations in characterising nonlinear distortion of signal in actual communication system. The effect of PIM on modulated signals are analysed at both the transmit and receive port with multiple passive nonlinear sources. Four types of coaxial connectors are adopted to represent four different levels of PIM. The equivalent circuits of PIM sources in series or parallel are proposed. With the circuit simulations and theoretical modelling, the effect of PIM on the analog and the digital modulation signals are analysed respectively. Two indexes of adjacent channel leakage ratio and error vector magnitude are modelled, showing the PIM effect at transmit port. A system model of a transmit‐receiver is provided, investigating the effect of PIM on the symbol error rate in a receiver. The effects of PIM distortion on different modulated signals are observed both in experimental measurements and simulation tests, verifying the theoretical models. [ABSTRACT FROM AUTHOR]

A novel method for modelling the passive intermodulation (PIM) in radio frequency (RF) devices, which works as a complex non‐linear system, was proposed. Both behaviour modelling and experimental validation were introduced to clarify the generation of PIM in a parallel and series non‐linear system. Taking the coaxial connector as an example, two types of N‐type connectors with 4 and 6 contact petals were selected and put into research. The measurements both agree well with the predicted results, validating the proposed model. [ABSTRACT FROM AUTHOR]

Swept-sines provide a tool for fast and high-resolution measurement of evoked otoacoustic emissions. During the measurement, a response to swept-sine(s) is recorded by a probe placed in the ear canal. Otoacoustic emissions can then be extracted by various techniques, e.g., Fourier analysis, the heterodyne method, and the least-square-fitting (LSF) technique. This paper employs a technique originally proposed with exponential swept-sines, which allows for direct emission extraction from the measured intermodulation impulse response. It is shown here that the technique can be used to extract distortion-product otoacoustic emissions (DPOAEs) evoked with two simultaneous swept-sines. For proper extraction of the DPOAE phase, the technique employs previously proposed adjusted formulas for exponential swept-sines generating so-called synchronized swept-sines (SSSs). Here, the SSS technique is verified using responses derived from a numerical solution of a cochlear model and responses measured in human subjects. Although computationally much less demanding, the technique yields comparable results to those obtained by the LSF technique, which has been shown in the literature to be the most noise-robust among the emission extraction methods. [ABSTRACT FROM AUTHOR]

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Attaining a high-resolution and accurate location for a radiated passive intermodulation source (R-PIMS) has been an increasingly interesting problem in modern multi-carrier wireless communication systems. For precisely positioning multiple closely spaced R-PIMSs, a novel imaging method called cascade decomposition of time-reversal operator (C-DORT) was developed. C-DORT constructs a new spectrum calculation by normalizing and multiplying the pseudo-spectrum at each sampled frequency together. The cascade process focuses the pseudo-spectrum at R-PIMS positions to form a highly brightened spectrum peak and to suppress the remained pseudo-spectrum to approximately zero, contributing to distinguishing the closely spaced R-PIMSs. The positioning performance of the positioning resolution, pseudo-spectrum width, positioning accuracy, and imaging robustness are analyzed by numerical simulations. Compared with the conventional central frequency decomposition of time-reversal operator (CF-DORT) and the time domain decomposition of time-reversal operator (TD-DORT) methods, the multiple R-PIMSs, spaced at a distance of diffraction limit, which is the spacing of 1/2 of a wavelength, are distinguished effectively in C-DORT. Additionally, the cross-range pseudo-spectrum full width at half maxima (CRPS-FWHM) is suppressed to the width of 1/4 of a wavelength by multiplication to improve the cross-range resolution in C-DORT. In addition, accurate positioning is obtained by providing the approximately zero positioning root mean square estimation (RMSE) at an SNR ranging from 0 dB to 10 dB. The results show that the proposed C-DORT improves the positioning accuracy and enhances the positioning resolution for locating an R-PIMS. [ABSTRACT FROM AUTHOR]

Training of viewing an altered‐reality environment dichoptically has been found to reactivate human adult ocular dominance plasticity, allowing improvement of vision for amblyopia. One suspected mechanism for this training effect is ocular dominance rebalancing through interocular disinhibition. Here, we investigated whether the training modulated the neural responses reflecting interocular inhibition. Thirteen patients with amblyopia and 11 healthy controls participated in this study. Before and after six daily altered‐reality training sessions, participants watched flickering video stimuli with their steady‐state visually evoked potential (SSVEP) signals recorded simultaneously. We assessed the amplitude of SSVEP response at intermodulation frequencies, which was a potential neural indicator of interocular suppression. The results showed that training weakened the intermodulation response only in the amblyopic group, which was in agreement with the hypothesis that the training reduced interocular suppression specific to amblyopia. Moreover, even one month after the training ended, we could still observe this neural training effect. These findings provide preliminary neural evidence in support of the disinhibition account for treating amblyopia. We also explain these results with the ocular opponency model, which, to our knowledge, is the first time for this binocular rivalry model to be used in explaining long‐term ocular dominance plasticity. [ABSTRACT FROM AUTHOR]

Interference caused by passive intermodulation (PIM) has seriously affected system performance. Compressed sensing (CS) can be used to locate radial PIMs. In CS-based electromagnetic imaging methods, the ability to locate the number of targets is usually limited by the number of receiving antennas, and there are flooding problems in the imaging results. To solve these problems, traditional methods are used to increase the number of receiving antennas. To reduce the number of receiving antennas and improve the imaging effect, this paper proposes a virtual array expansion synchronous imaging compressed sensing (SI-CS) method. With the full-wave electromagnetic simulation demonstrations, the proposed method exhibits significant improvement in imaging performance compared to the conventional methods. In addition, the proposed method can discriminate between targets in the presence of the flooding problem in which the paraflap is too large and the location of the PIM source cannot be determined by the amplitude value. [ABSTRACT FROM AUTHOR]

The conventional radar technology is based on linear detection—i.e., the same transmit and receive frequencies are used. However, with linear radars, difficulties arise when detecting electronic objects with relatively small radar cross section (RCS). To overcome these limitations, a nonlinear radar that can detect nonlinear responses (i.e., harmonic and intermodulation) scattered by electronic devices due to nonlinear interaction can be utilized. Nonlinear radars require a different analysis from linear radars for analyzing RCS. In this paper, we present an experimental analysis of the nonlinear RCS of various electronic devices. Unlike linear radars, RCS in nonlinear radars is determined by the amount of nonlinear responses backscattered to the radar. Therefore, we derive a radar equation accustomed to harmonic radars that consists of nonlinear RCS. We then obtain and analyze the nonlinear RCS of various targets from the measured harmonic responses of the targets based on the nonlinear radar equation.

In this article, a Ka-band broadband analog predistortion (APD) microwave monolithic integrated circuit (MMIC) with independent tunability based on a 0.15 μm GaAs pHEMT process is proposed, which can be cascaded in front of traveling wave tube amplifiers (TWTAs) to improve their linearity. The influence of different diode sizes on the parameters of Schottky diodes is analyzed and used to design the gain and phase nonlinear branches. The broadband APD MMIC is realized based on a dual-branch vector synthesis design and nonlinear frequency adjust module (NFAM). The independent tunability and broadband characteristics of the APD MMIC are verified by simulated and measured results with an error of less than 5%. Furthermore, a Ka-band 60 W TWTA is linearized by the APD MMIC, and the gain and phase compressions are reduced from 8 dB and 50° to within 3 dB and 12°, respectively. The third-order intermodulation (C/IM3) is greater than 28 dBc and noise power ratio (NPR) is greater than 15.7 dBc at 3 dB output power backoff (OPBO) over the operating band of 25.1~27.5 GHz, indicating that the APD MMIC can improve the nonlinearity of TWTA effectively under broadband signals. [ABSTRACT FROM AUTHOR]

Human movement synchronisation with moving objects strongly relies on visual input. However, auditory information also plays an important role, since real environments are intrinsically multimodal. We used electroencephalography (EEG) frequency tagging to investigate the selective neural processing and integration of visual and auditory information during motor tracking and tested the effects of spatial and temporal congruency between audiovisual modalities. EEG was recorded while participants tracked with their index finger a red flickering (rate fV = 15 Hz) dot oscillating horizontally on a screen. The simultaneous auditory stimulus was modulated in pitch (rate fA = 32 Hz) and lateralised between left and right audio channels to induce perception of a periodic displacement of the sound source. Audiovisual congruency was manipulated in terms of space in Experiment 1 (no motion, same direction or opposite direction), and timing in Experiment 2 (no delay, medium delay or large delay). For both experiments, significant EEG responses were elicited at fV and fA tagging frequencies. It was also hypothesised that intermodulation products corresponding to the nonlinear integration of visual and auditory stimuli at frequencies fV ± fA would be elicited, due to audiovisual integration, especially in Congruent conditions. However, these components were not observed. Moreover, synchronisation and EEG results were not influenced by congruency manipulations, which invites further exploration of the conditions which may modulate audiovisual processing and the motor tracking of moving objects. [ABSTRACT FROM AUTHOR]

Induction heating appliance operation is constrained by the nonlinear pot material behavior under the generated magnetic field. The equivalent load seen by the inverter varies with the intensity of the field, meaning that this variation is dependent on the mains voltage. In flexible-surface induction cooktops, this fact is combined with a high coil number and different pots to be powered simultaneously, increasing the complexity to control the transmitted power while maintaining proper mains current consumption. In this article, two noncomplementary asymmetrical modulations with in-cycle parameter variation are proposed for improved power factor correction while avoiding the need for switching frequency variation and intermodulation noise in multiload systems. The proposed strategies are analyzed and experimentally tested using a 3.6 kW multi-inverter prototype featuring five induction coils. [ABSTRACT FROM AUTHOR]

The demands of emerging wireless communication are higher bandwidth, low latency, high-quality multimedia applications, less environmental impact etc., with cost-effective network implementation. The Radio over Fiber (RoF) link will be the best substitute, and this paper presents an analytical and simulation of the dual parallel DE-MZMs based RoF link while considering of different optical fiber distances. The utility of dual parallel DE-MZMs in RoF link provides the significant enhancement in dynamic range of link in microwave photonic link. Further, it is found that the IM3 terms are approximate eliminated or 40.9 dB much lower w.r.t. fundamental signals for 1 km optical fiber length by the proposed DPMZM based RoF link. The analytical analysis is verified by simulation using OptSIM (Optical Simulator) software. Finally, the comparative analysis of the proposed DPMZM based RoF link with the conventional link confirms the optimization against third order intermodulation and fiber impairments. This optimization of the proposed link will be helpful for microwave photonic links without any digital processing. [ABSTRACT FROM AUTHOR]

Accurate passive intermodulation (IM) test calls for precise IM reference for verifying and evaluating the test error from the tester, which makes the IM calibrator source with a wide working band and dynamic range important. This letter reports on a low‐cost and broadband IM generator with a compact area of 5 × 5 cm2. The broadband IM source is designed and demonstrated on the coplanar waveguide structure, where an artificial nonlinear dipole is used to generate IM reference. In special, the dipole is constructed by a diode (HSMS 2822) and two independent copper islands with optimized size. By controlling the bias voltage across the diode, the IM magnitude level can be changed accordingly. The IM tunable dynamic range is over 47.5 dB that covers GSM 800 MHz, GSM 900 MHz, DCS 1800 MHz, and TD‐LTE band. Meanwhile, the obtained IM has an improved IM‐bias flat response. [ABSTRACT FROM AUTHOR]

Previous intermodulation (IM) studies have employed two (or more) temporal modulations of a stimulus, with different local elements of the stimulus being modulated by different frequencies. Brain activities of IM obtained mainly from electroencephalograms (EEG) have been analyzed in the frequency domain. As a powerful tool, IM, which can provide a direct and objective physiological measure of neural interaction, has emerged as a promising method to decipher neural interactions in visual perception, and reveal the underlying different perceptual processing levels. In this review, we summarize the recent applications of IM in visual perception, detail the protocols and types of IM, and extend its utility and potential applications to the multisensory domain. We propose that using IM could prevail in partially revealing the potential hierarchical processing of multisensory information and contribute to a deeper understanding of the underlying brain dynamics. [ABSTRACT FROM AUTHOR]

In order to improve the radar's electromagnetic protection ability, it is essential to master the law of the false alarm effect of the radar's out-of-band third-order intermodulation electromagnetic radiation, starting from the circuit field-circuit coupling mechanism, and the mechanism of the third-order intermodulation false alarm effect is analyzed. Taking a stepped frequency ranging radar as the research object, the absolute level value of the false alarm signal is selected as the sensitive criterion of the false alarm effect. The dual-frequency electromagnetic false alarm interference effect is carried out by using the method of the differential mode injection equivalent substitution electromagnetic radiation. The results show that the dual-frequency electromagnetic interference will cause the radar to generate the third-order intermodulation false alarm signal with the random position and waveform spreading. Under a certain interference intensity, the level of the third-order intermodulation false alarm signal increases with the increase of the interference field strength. With the continuous increase of the interference field strength, the fifth-order intermodulation false alarm signal gradually appears. The imaging mechanism, the waveform characteristics, and the level change law of the fifth-order intermodulation false alarm target, are similar to the third-order intermodulation false alarm target, and its position is also random. The maximum third-order intermodulation false alarm signal can reach 18 dBmV, indicating that the radar is sensitive to the out-of-band intermodulation electromagnetic interference. [ABSTRACT FROM AUTHOR]

The work presented here, investigates the effect of overlap and underlap extensively on dual-material gate-oxide-stack double-gate tunnel field effect transistor (DMGOSDG-TFET) for the first time. To observe the influence of overlap and underlap on the device performance, DC parameters and analog/RF parameters such as: transfer characteristics, parasitic capacitances, transconductance ( g m ), cutoff frequency ( f T ), Gain Bandwidth Product (GBP) for DMGOSDG-TFET with overlap and underlap have been inspected and analyzed in contrast with the conventional device dual-material double-gate tunnel field effect transistor (DMDG-TFET) with similar dimension. Along with this, the impact of overlap and underlap on linearity parameters such as Input Intercept Point ( IIP 3 ), Intermodulation Point ( IMD 3 ) and Voltage Intercept Point ( VIP 3 ) have been also investigated and contrasted with the conventional DMDG-TFET. The impact of positive and negative trap charges has also been carried out in this work for the I DS - V GS characteristics of devices. Along with this, the gate leakage has also been studied. The TCAD simulation results prove that DMGOSDG-TFET is a better candidate where DC, analog/RF and linearity performance would be of great importance under overlap and underlap conditions. The simulation results also demonstrate that gate to source overlap and underlap, improves the device performance and makes the device more reliable for analog/RF applications. However, increasing the overlapping beyond 5nm does not bring any further enhancement in the device performance. [ABSTRACT FROM AUTHOR]

In order to master the law of the pseudo-signal interference effect of dual-frequency electromagnetic radiation in typical radar equipment, a certain type of Ku-band swept-frequency ranging radar was used as the test object to carry out single-frequency continuous wave and dual-frequency continuous wave pseudo-signal interference effect experiments. Through experiments, it is found that dual-frequency electromagnetic radiation will cause "hill" and "spike" type pseudo-signal interference to the swept-frequency radar. Based on the frequency analysis of the radar receiving circuit, the interference mechanism of the dual-frequency pseudo-signal is revealed, and the morphological characteristics and distance law of the pseudo-signal are explained. The variation law of the pseudo-signal level with interference field strength is obtained. The results show that the in-band dual-frequency nonintermodulation interference is similar to the single-frequency interference, and the only difference is that the number of pseudo-signals increases; when the interference frequency difference is about 400∼600 MHz, the out-of-band dual-frequency second-order intermodulation signal will cause "hill" type pseudo-signal interference, and the pseudo-signal distance is random; when the interference frequency difference is less than 5 MHz, both the dual-frequency second-order intermodulation signal and the third-order intermodulation signal will cause "spike" pseudo-signal interference inside and outside the radar operating frequency band; the pseudo-signal distance is fixed. [ABSTRACT FROM AUTHOR]

A significant challenge for dual-beam, codesigned systems, such as for simultaneous radar and communications transmission, has been identified as the spurious beams produced by spatial intermodulation from nonlinearities in the transmitter power amplifier. We demonstrate that tuning the load impedance of the power amplifiers can reverse the elementwise power amplifier nonlinear distortion, reducing the magnitude of the unwanted beam transmissions and restoring the integrity of the dual-beam antenna pattern for application to an active electronically scanned array. A comparison to a recently documented predistortion approach for correcting spurious transmissions is provided, and it is shown that impedance tuning can address both element output power and linearity, whereas predistortion addresses only the linearity issue and causes the amplifier gain in many of the array elements to suffer. For multiple dual-beam angle scenarios, simulation results show that impedance tuning is effective at maximizing beam power in both beam directions, maximizing current gain in the element power amplifiers, and minimizing the size of the unwanted spurious beams. [ABSTRACT FROM AUTHOR]