Amplitude Compensation Research Articles

Modulating Phase Encoding With Amplitude Compensation for Hologram Reconstruction

Modulating Phase Encoding With Amplitude Compensation for Hologram Reconstruction

Design of a Near-Field Synthetic Aperture Radar Imaging System Based on Improved RMA

Traditional near-field synthetic aperture radar (SAR) imaging algorithms reveal target features by exploiting signal amplitude and phase information. However, electromagnetic wave propagation is constrained by short distance. Therefore, the spherical wave approximation needs to be considered. In addition, it is also limited by equipment ambient noise, azimuth-distance coupling, wave scattering, and transmission power. Both the amplitude and phase of the signal suffer from the interference of multiple clutter, so they cannot be effectively utilized. To address these issues, this paper introduces a covering penetration detection system based on an improved Range Migration Algorithm (IMRMA) imaging method. Firstly, the proposed method minimizes interferences from the front end of the system using an optimized window to balance denoising and information preservation. Next, interval non-uniform interpolation, instead of Stolt interpolation decoupling, is employed to reduce the computational overhead significantly. To minimize the effects due to wave scattering and propagation loss, distance information is enhanced using amplitude and phase compensation. This reduces scattering effects and enhances image quality. An experimental system is constructed based on a vector network analyzer (VNA) to image the target. The proposed method takes about half the time of traditional RMA. The PSNR in the chunky bowl experiment is higher than 14 dB, which is higher than all the compared methods in the paper. The test results show that the designed system and the reported method can effectively achieve high-resolution images by strengthening the target intensity and suppressing the environmental artifacts.

Ultrasonic testing method for impeller brazing defects with refraction wave perpendicular to brazing surface and angle amplitude compensation

Abstract There are blind areas in ultrasonic brazing defect detection, due to the non-parallel brazing surface and outer surface for many components including impeller. In this paper an oblique incident ultrasonic testing method with a refraction wave perpendicular to brazing surface is proposed. Meanwhile, an incident angle amplitude compensation is implemented to decrease the influence of the defect echo amplitude difference caused by oblique incidence and unify the sensitivity of different scanning positions. The compensation curve based on the theoretical curve of echo energy at different incident angles is optimized with iteration of actual measured defect echo amplitude. In order to prove the need for ultrasonic testing method with a refraction wave perpendicular to brazing surface, bottom surface echo test for conical samples is operated. In addition, with the method proposed in this paper, scanning image of impeller sample with the same detection sensitivity is obtained successfully. Testing results suggest that in relation to old method with incident wave perpendicular to the outer surface, the method proposed in this paper can solve the blind area problem effectively.

A Spoof Surface Plasmon Polaritons Filter with Controllable Negative Slope Equalization Based on Surface Resistance

This paper presents a novel spoof surface plasmon polariton (SSPP) filter integrated with controllable negative slope equalization. Different from traditional microwave filters, two microwave functions - amplitude compensation and interference suppression - are integrated into one device by depositing a lossy indium tin oxide (ITO) film on the rectangular corrugated stub of the SSPP unit. The key point of negative slope equalization benefits from the surface resistance of the ITO film, and the circuit model and behavior are analyzed in detail. Based on the principle, a prototype of a SSPP filter operating from S to C band is designed and fabricated. The measurement results show that the attenuation in the passband increases almost linearly from 3.5 GHz (−4.8 dB) to 6.9 GHz (−15.4 dB), indicating that −10.6 dB equalization is achieved. The improved S21 is attributed to the good impedance matching by sputtering the ITO film on the rectangular metal strip rather than the central strip. Due to the natural low-pass property of SSPPs, the high-order parasitic band is suppressed above the cut-off frequency of 8.5 GHz. The analyses, simulations and measurements show that the proposed SSPP filter is provided with an additional ability to compensate for positive amplitude fluctuation in wideband antennas.

Electrically tunable substrate integrated waveguide equalizer based on PIN diodes

AbstractIn this letter, a novel design of electrically tunable substrate integrated waveguide (SIW) equalizer, based on PIN diodes, is proposed. Compared to previous SIW equalizers, this one introduces PIN diodes that exhibit varying impedance under different direct current (DC) voltages. The equalizing values of the SIW equalizer are directly linked to the DC voltage applied to the PIN diode within a specific voltage range. This feature allows it to be considered as an electrically tunable SIW equalizer. The experimental results demonstrate that the equalizing values are consistently monotonic and adjustable within the range of 1.59–7.56 dB in Ku‐band. This adjustment is attained through a DC voltage step of −0.01 V, applied within the range of 1.23–1.11 V. Additionally, the microwave equalizer is a planar structure that can be conveniently implemented on traditional printed circuit board, resulting in lower costs, easier realization, and integration. This SIW equalizer can be applied in amplitude compensation circuits and networks to compensate flatness dynamically.

A 5.6-dB Noise Figure, 63–86-GHz Receiver Using a Wideband Noise-Cancelling Low Noise Amplifier With Phase and Amplitude Compensation

A 5.6-dB Noise Figure, 63–86-GHz Receiver Using a Wideband Noise-Cancelling Low Noise Amplifier With Phase and Amplitude Compensation

Experimental evaluation of the SNR in counting detectors under pile-up conditions

As a follow-up of a Signal-to-Noise Ratio (SNR) study presented previously, this work discusses the experimental results obtained for the statistical analysis of photon counting detector measurements. The test device is a hybrid assembly built with a pixelated 400 μm thick electron collection Si sensor bump-bonded to a SPHIRD test readout ASIC. The analog front-end in each pixel of the ASIC produces a pulse of tens of nanoseconds for each X-ray hit, and its digital circuitry implements both amplitude and time-based pile-up compensation methods, making this device an excellent candidate for this study. Under pile-up conditions, the SNR of the photon counting measurements deviates from Poisson statistics and it has been evaluated by applying the numerical method introducedin a previouswork. In addition to standard photon counting operation, two pile-up compensation methods implemented in SPHIRD were tested. The results were evaluated for individual pixels. The standard photon counting results reproduce the simulated behavior, presenting a SNR response that peaks around 30% pile-up, and then drops. Meanwhile, both pile-up compensation methods have presented a comparable effect on improving not only the count rate but also the statistical response of the system, for the covered count-rate range of up to 45Mcps/pixel. The obtained results validate the presented methodology to obtain the SNR, also elucidating the pile-up detrimental effect on the statistical quality of the data.

A Periodic Multiple Phases Modulation Active Deception Jamming for Multistatic Radar System

Aiming at the problem that the amplitudes of false targets (FTs) are correlated among receivers in multistatic radar system (MSRS), a multi-jammer cooperative deception jamming method based on periodic multiple phases modulation (PMPM) is proposed. A FT string with random fluctuations in amplitude can be generated after the signal undergoes PMPM. In the distributed jammer system, each jammer adopts PMPM jamming method with different parameters, and then jointly transmit beamforming to forward jamming signals. Finally, the amplitude of the FTs between receivers is jointly affected by the azimuth angle and the phase modulation coefficient, which destroys the amplitude "coherence" of the FTs between receivers, and eliminates the amplitude symmetry and high-order attenuation characteristics of the FT strings generated by traditional jamming method. We study the amplitude compensation and amplitude correlation performance of the proposed jamming method, derive the rank of the ratio matrix of amplitude correlation factors, and prove that FTs have dispersiveness in the amplitude ratio space. In order to obtain the optimal and stable jamming effect, a genetic algorithm (GA)-based jamming modulation parameter optimization method is designed, which effectively drops the discrimination probability of physical targets (PTs) to 14% in the benchmark scenario. Simulation experiments demonstrate the feasibility and effectiveness of the jamming method.

A Multimode 28 GHz CMOS Fully Differential Beamforming IC for Phased Array Transceivers

A 28 GHz fully differential eight-channel beamforming IC (BFIC) with multimode operations is implemented in 65 nm CMOS technology for use in phased array transceivers. The BFIC has an adjustable gain and phase control on each channel to achieve fine beam steering and beam pattern. The BFIC has eight differential beamforming channels each consisting of the two-stage bi-directional amplifier with a precise gain control circuit, a six-bit phase shifter, a three-bit digital step attenuator, and a tuning bit for amplitude and phase variation compensation. The Tx and Rx mode overall gains of the differential eight-channel BFIC are around 11 dB and 9 dB, respectively, at 27.0–29.5 GHz. The return losses of the Tx mode and Rx mode are >10 dB at 27.0–29.5 GHz. The maximum phase of 354° with a phase resolution of 5.6° and the maximum attenuation of 31 dB, including the gain control bits with an attenuation resolution of 1 dB, is achieved at 27.0–29.5 GHz. The root mean square (RMS) phase and amplitude errors are <3.2° and <0.6 dB at 27.0–29.5 GHz, respectively. The chip size is 3.0 × 3.5 mm2, including pads, and Tx mode current consumption is 580 mA at 2.5 V supply voltage.

Accurate Thickness Measurement Based on Dispersion Compensation via Terahertz Time-Domain Spectroscopy

Terahertz time-domain spectroscopy (THz-TDS) has shown significant potential in thickness detection. The time-of-flight (TOF) method is most widely used for judgment. However, the method only refers to peak information, and waveform information, such as deformation, is simply ignored. Consequently, errors are introduced when testing samples with high dispersion and large absorptive properties. As a result, the signals are broadened, and the peaks become smooth or even disappear, which makes the TOF method fail. In this article, we propose a dispersion compensation (DC) algorithm to solve the above problems. Thickness can be accurately determined by nondispersive signals in the spatial domain. Amplitude compensation is used for materials with large absorption. The DC algorithm’s error is less than 1% of the TOF algorithm’s error in simulations. While measuring LiNbO <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{3}$</tex-math> </inline-formula> and water film, errors are, respectively, reduced by 96.24% and 50% compared with using the TOF method, and corresponding deviations are 0.2% and 1.6% compared with the reference thickness. Moreover, the DC algorithm is noniterative, stable, and requires much less calculations than the fitting method. The DC method drastically improves the accuracy by overcoming inherent drawbacks of the TOF method. It can be applied in fields such as nondestructive testing and in-line quality control because of noncontact and real-time advantages.

An inverse Q filtering method with adjustable amplitude compensation operator

The generalized stable inverse Q filtering method can flexibly select the intensity and frequency bandwidth of amplitude compensation operator according to the signal-to-noise ratio (SNR) of seismic data. When processing noisy seismic data, the method can avoid enhancing some noise energy by adjusting parameters. However, this method still faces the problem of noise amplification when the SNR of seismic data is low. In order to solve this problem, this paper proposes an adjustable amplitude compensation operator, which can suppress part of the high frequency noise energy effectively without affecting the intensity of the amplitude compensation by introducing a dynamically adjustable amplitude compensation curve. Combining this operator with the generalized stable inverse Q filtering algorithm, an inverse Q filtering method with adjustable amplitude compensation operator is developed. Compared with the generalized stable inverse Q filtering method, this method has the ability of adjustable amplitude compensation and adjustable noise suppression. When inverse Q filtering is performed on the seismic records, the compensation strategy can be more flexible according to its quality and processing requirements. In addition, this method almost not introduce extra calculation cost, and has the characteristics of simplicity and high efficiency. Theoretical and practical seismic records show that the proposed method can further improve the SNR and resolution of seismic records after inverse Q filtering.

The Development of 3D Atomic Force Microscopy with Magnetically Driven-Orthogonal Cantilever Probes

This paper presents a three-dimensional (3D)-atomic force microscopy (AFM) method based on magnetically driven (MD)-orthogonal cantilever probes (OCPs), in which two independent scanners with three degrees of freedom are used to achieve the vector tracking of a sample surface with a controllable angle. A rotating stage is integrated into the compact AFM system, which helps to achieve 360° omnidirectional imaging. The specially designed MD-OCP includes a horizontal cantilever, a vertical cantilever, and a magnetic bead that can be used for the mechanical drive in a magnetic field. The vertical cantilever, which has a protruding tip, can detect deep grooves and undercut structures. The design, simulation, fabrication, and performance analysis of the MD-OCP are described first. Then, the amplitude compensation and home positioning for 360° rotation are introduced. A comparative experiment using an AFM step grating verifies the ability of the proposed method to characterize steep sidewalls and corner details, with a 3D topography reconstruction method being used to integrate the images. The effectiveness of the proposed 3D-AFM based on the MD-OCP is further confirmed by the 3D characterization of a micro-electromechanical system (MEMS) device with microcomb structures. Finally, this technique is applied to determine the critical dimensions (CDs) of a microarray chip. The experimental results regarding the CD parameters show that, in comparison with 2D technology, from which it is difficult to obtain sidewall information, the proposed method can obtain CD information for 3D structures with high precision and thus has excellent potential for 3D micro–nano manufacturing inspection.

Enhanced Forward-Looking Missile-Borne Bistatic SAR Imaging With Electromagnetic Vortex

Bistatic radar possesses the forward-looking imaging performance that conventional synthetic aperture radar (SAR) lacks. Nevertheless, bistatic forward-looking imaging is seriously limited by the motion of the transmitter and receiver, resulting in a restrained resolution. In this work, the method for vortex missile-borne bistatic SAR (BSAR) is proposed, which combines the orbital angular momentum (OAM) beam with the traditional missile-borne BSAR technique to obtain a larger Doppler bandwidth. Higher azimuth resolution is achieved by compensating large spatial range cell migration (RCM) and serious range-azimuth coupling. First, the imaging scene of vortex missile-borne BSAR and the OAM-based echo model are established and deduced. Second, the preprocessing method for amplitude compensation is proposed with the design of the transmitted OAM beam, which improves the uncorrelation between different pulse echoes. Then, the improved range Doppler (RD) algorithm with azimuth compensation factor is proposed for vortex missile-borne BSAR to obtain the super-resolution 2-D reconstruction for the target. Simulation results show that compared with conventional missile-borne BSAR, the proposed vortex missile-borne BSAR possessing the extending Doppler bandwidth can obtain superior azimuth resolution performance with the identical synthetic aperture length situation. Furthermore, this work will contribute to the application for OAM-carrying in the field of radar forward-looking imaging and the development for high-resolution missile-borne BSAR imaging technology.

The inverse Q filtering method based on a novel variable stability factor

The inverse Q filtering method with a stabilization factor solves the noise amplification problem caused by the exponential growth of the amplitude compensation operator in traditional inverse Q filtering to a certain extent, but it is not ideal for reducing noise and amplitude compensation of deep seismic records. The inverse Q filtering method with a variable stabilization factor is superior to the inverse Q filtering method with a constant stable factor in reducing noise, but the amplitude compensation for the deep seismic record is still not ideal, especially when the quality factor Q value is small. In addition, because its compensation function changing with time and frequency is fixed, its amplitude compensation cannot be flexibly carried out according to the characteristic of seismic records. We have developed a novel inverse Q filtering method with a new variable stabilization factor under the constraint of signal-to-noise ratio (S/N). The S/N of seismic data is taken as prior information, and the stabilization factor is a function of the S/N and the quality factor. The amplitude compensation operator changes dynamically with time, frequency, S/N, and the quality factor, which can accurately compensate for the effective amplitude while avoiding enhancing the noise energy. Theoretical synthetic seismic data and real seismic data using the new method find significant improvements in amplitude compensation and suppression of noise energy. The new method has the strongest comprehensive ability of amplitude compensation and noise suppression. The resolution and S/N of seismic data processed by the new method have been improved.

Evaluation of space charge distribution under a divergent electric field by combining experiment and simulation

Under divergent electric fields, space charge is locally accumulated and controls the initiation and evolution of insulation degradation phenomena, such as electrical trees and partial discharge. The space charge profiles provide crucial information for evaluating the insulation performance. However, the existing space charge measurement methods are not directly applicable under divergent electric fields. In this paper, a method combining experiment and simulation is proposed to evaluate the space charge distribution around a needle electrode. An experimental system is established, and the acoustic waves are measured with a hydrophone placed on the symmetric axis. In order to obtain the space charge distribution, the space charge injection process is simulated using the bipolar charge transport model to reduce the freedom of the distribution. Then, calculations are made for the acoustic waves produced by the simulated space charge distributions. Using the signals without the contribution of internal charge, a correspondence between the experiment and simulation is established. For each experimental signal, the matched calculated signal is obtained using the zero-crossing time as a reference. A perfect match between them is presented after the amplitude compensation, which indicates that the space charge distribution in the experiment is identical to that in the simulation model.

An explicit stable Q-compensated reverse time migration scheme for complex heterogeneous attenuation media

Prestack reverse-time migration (RTM) is a popular imaging technique for complex geological conditions, since the amplitude attenuation and velocity dispersion are common in seismic recordings. To image attenuated seismic recordings accurately, a robust migration algorithm with a stable attenuation compensation approach should be considered. In the context of the Q-compensated RTM approach based on the decoupled fractional Laplacians (DFLs) viscoacoustic wave equation, amplitude compensation can be implemented by flipping the sign of the dissipation term. However, the non-physical magnification of image amplitude could lead to a well-known numerical instability problem. The explicit stabilization operator can rectify the amplitude attenuation and suppress the numerical instability. However, limited by the inconvenient mixed-domain operator, the average Q value rather than the real Q value is often used in the compensation operator, lowering the compensated accuracy of the migration image. To overcome this problem, we propose a novel explicit Q-compensation scheme. The main advantage of the proposed compensation operator is that its order is space-invariant, making it more suitable for handling complex heterogeneous attenuation media. Several two-dimensional (2D) and three-dimensional (3D) synthetic models are used to verify the superiority of the proposed approach in terms of amplitude fidelity and image resolution. Field data further demonstrates that our approach has potential applications and can greatly enhance the resolution of seismic images.

Accurate and Efficient Method for Analyzing the Transfer Efficiency of Metasurface-Based Wireless Power Transfer System

An accurate and efficient calculation method for analyzing the transfer efficiency of a metasurface-based wireless power transfer system (ATEMWS-method) is proposed in this article. According to the amplitude and phase compensation information of the metasurface units (MUs) and using the superposition of the radiated electric field of each MU, the ATEMWS-method can calculate the wireless power transfer (WPT) efficiency from the metasurface to the energy harvester in any case. WPT systems based on a transmissive metasurface with a focused beam and a reflective metasurface with a high-gain directional beam are simulated to verify the method’s effectiveness and correction. The results show that the proposed method has high accuracy in evaluating the WPT efficiency and dramatically improves the near-field accuracy by more than 70% compared with traditional methods. To further verify the accuracy of the ATEMWS-method in the near-field region, WPT systems based on transmissive and reflective metasurfaces with focused beams are fabricated to compare the experimental measurement and calculation results. The calculated results of the proposed method are particularly close to both simulated and measured values with a relative error of less than 0.5%, while it takes only one-thousandth of the simulation time by the commercial software. Due to its accuracy and convenience, the proposed method provides guidance and simplifies the design difficulty for the metasurface-based WPT system.

Wideband Noncontact Voltage Measurement for EMC Applications: Design and Implementation

A methodology of amplitude and phase compensation for non-contact voltage measurements, which can be applied to wideband signal and noise observation in the EMC application, is presented. The non-contact techniques are based on a small amount of coupling capacitance between probe electrode and cable conductor where the observed signal is induced. In this case, a main technical issue to be overcome is the amplitude and phase error introduced by stray capacitance of the internal circuit, which needs to be resolved for application of the wideband EMC measurements. Herein, a design and implementation of phase compensation with inverting OpA configuration are discussed. Moreover, by introducing a system calibration with numerical process, validity for recovering the frequency response at 100 Hz ~ 100 MHz is indicated. In the calibration process, frequency compensation for dielectric dispersion of the PVC cable is also discussed. As for the time-domain measurement, the evaluation result of the fast transient impulsive noise of tr/tf: 10 ns emitted from a commercial power supply module is also discussed.

Online Dynamic Detection of Hazardous Cracks in Train Wheels by Probe Combination: Based on Classical Piezoelectric Ultrasonic Technology

Online dynamic crack detection of train wheels is critical to ensure transportation safety. In the existing detection system, because the electromagnetic ultrasonic surface wave technology is challenging to detect the deep cracks in the wheel that endanger the safety of the vehicle operation, the online detection of train wheel cracks needs to explore new technologies. Based on the classical piezoelectric ultrasonic technology, this paper proposes a novel ultrasonic probe combined array method to meet the needs of online dynamic detection of deep cracks in train wheels. To reduce the difference in the sensitivity of the probe array, a method of drawing the Distance Amplitude Compensation (DAC) curve is given, and the defect equivalent is judged by software gain compensation. Experiments show that the process design and method of the probe array proposed in this paper can detect the deep, dangerous cracks in the radial and circumferential directions of the wheel, and the test results have acceptable repeatability and consistency. It has advantages in flaw detection coverage and data processing efficiency and is suitable for daily online crack detection of train wheels.

Cryogenic Multiplexing Control Chip for a Superconducting Quantum Processor

This paper proposes a scheme and design of a cryogenic multiplexing control chip (MCC), which enables one microwave cable to control many superconducting qubits. Designed based on an adjustable inductor, the MCC is a nonreciprocal device that generates microwave signals between 4 and 8 GHz and constructs a $XY$ control circuit to operate qubits. The effects of filters, isolators, power splitters, qubits, and load impedance on the MCC are analyzed in the frequency-domain simulation. And in the time-domain simulation, the response time, Gaussian pulses, single sideband, amplitude, and frequency compensation of the MCC are examined. The MCC can be integrated with the superconducting qubits on the same package at the 20-mK temperature stage with insertion loss of $\ensuremath{-}6$ dB and isolation of $\ensuremath{-}26$ dB. The time-domain simulation has revealed that the output specific microwave pulses of the MCC can be used for driving the superconducting qubits with crosstalk of about $\ensuremath{-}80$ dB. This is much less than $\ensuremath{-}40$ dB of the physical requirements on crosstalk, which can meet fidelity on single-qubit (99.92%) and two-qubit gates (99.40%). The power dissipation for each qubit control is less than 1 pW. The MCC can greatly reduce the number of microwave control lines and is beneficial to the development of a large-scale superconducting quantum processor.