Amplitude Errors Research Articles

A ku-band common-leg transceiver with built-in configurable register in 130-nm CMOS technology for phased-array systems

To solve the bottleneck of amplitude and phase accuracy deterioration caused by process and unpredictable errors, this paper proposes a Ku-band common-leg transceiver with built-in configurable register to achieve 64-state amplitude and phase accuracy correction, respectively, by redefining control codes of each state after taping out. Two-stage cascaded variable gain amplifiers (VGAs) and the vector-summing phase shifter (VSPS) with tail current source controlled by DAC are adopted to achieve large amplitude and phase coverage of 31.5 dB with the LSB of 0.5 dB and 360° with the LSB of 5.625°, respectively. According to the measurement results, in the frequency range of 14–18 GHz, the chip has amplitude accuracy with the root mean square (rms) error of ＜ 0.4 dB, while the rms phase error is ＜ 5.3°. The phase shifting accuracy is measured to be ＜ 2.2°, while the rms amplitude error is ＜ 0.67 dB. The receiving and transmitting channels have reference gain of 3.6–6 dB and 8–10.4 dB, respectively. The whole transceiver occupies 3 × 2.3 mm2 chip area including pads.

Calibration of Wideband LFM Radars Based on Sliding Window Algorithm

This paper addresses the challenges of wideband signal beamforming in radar systems and proposes a new calibration method. Due to operating conditions, the frequency-dependent characteristics of the system can be changed, and the amplitude, phase, and time delay error can be generated. The proposed method is based on the concept of the sliding window algorithm for linear frequency modulated (LFM) signals. To calibrate the frequency-dependent errors from the transceiver and the time delay error from the true time delay elements, the proposed method utilizes the characteristic of the LFM signal. The LFM signal changes its frequency linearly with time, and the frequency domain characteristics of the hardware are presented in time. Therefore, by applying a matched filter to a part of the LFM signal, the frequency-dependent characteristics can be monitored and calibrated. The proposed method is compared with the conventional matched filter-based calibration results and verified by simulation results and beampatterns. Since the proposed method utilizes LFM signal as the calibration tone, the proposed method can be applied to any beamforming systems, not limited to LFM radars.

Fault Detection and Location of 35 kV Single-Ended Radial Distribution Network Based on Traveling Wave Detection Method

With the progress of society and the iterative improvement of infrastructure construction, the power grid transmission lines have also entered an era of intelligence. The national distribution system has made ensuring the regular operation of the distribution network as well as prompting troubleshooting and detection its top priority. Research on fault diagnosis for 35 kV single-ended radial distribution networks is still in its infancy compared to other hot topics in the industry, such as short-circuit fault detection and fault node localization. This study adopts the 35 kV single-ended radial distribution network as a model, detects fault lines via the traveling wave method, and accurately locates fault nodes using the wavelet conversion method, hoping to quickly identify and locate fault nodes in distribution networks. The experimental results demonstrate that the research method can quickly identify the faulty line and carry out further fault node location detection. The final obtained fault distance is 1.19 km with an actual error of only 0.16 km; the maximum relative errors are only 0.33 km and 0.21 km when the initial phase angle and transition resistance parameters are changed, respectively; and the error amplitude fluctuations are essentially stable. The experimental results also demonstrate that the research method can quickly identify the faulty line and carry out further fault node location.

Design and implementation of a real-time compensation algorithm for nonlinear error based on ellipse fitting.

To improve the measurement accuracy of interferometer displacement measurement systems, this study analyzes the characteristics of the interference signal to identify sources of nonlinear errors and develops compensation strategies. Specifically, a model is established for the nonlinear errors of the interferometer, which can be attributed to a laser and polarizing beam splitter (PBS). Following that, the dual orthogonal lock-in amplification algorithm is used to separate and compensate for the frequency uncertainty and amplitude errors. Additionally, a real-time compensation algorithm based on ellipse fitting is proposed to compensate for errors caused by the PBS and the uncertainty of amplitude caused by the light source. Experimental results demonstrate that the peak-to-peak value of the compensated nonlinear error is reduced from 11.62 nm to 5.37 nm.

A 2.4 GHz low-power and compact 3-bit active phase shifter utilizing miller capacitance

A low-power and compact 3-bit active phase shifter is designed and implemented in a 22 nm FDSOI CMOS process. A modified inverter-based topology, which takes advantage of miller capacitance, is used to create a compact and low-power solution, resulting in ∼10× and ∼90× reduction in the power and chip area, respectively, for a given phase shift, compared to the standard inverter-based topology. At the same time, the proposed phase shifter exhibits less sensitivity to device mismatch. The proposed design measures ∼0.004 mm2, consumes 1.8 mW, and delivers up to 65°of phase shift with RMS phase and amplitude error of 3.85°and ±0.34 dB, respectively. The measured die-to-die variation is also confined to ±6.2°, which is <10% of the full range.

Transmission Line Voltage Measurement Utilizing a Calibrated Suspension Grounding Voltage Sensor.

The accurate voltage measurement of distribution networks is of great significance in power dispatching and fault diagnosis. Voltage sensors based on the spatial electric field effect do not require grounding, which provides the possibility for the distributed measurement of transmission line voltages. However, the divider ratio of suspension grounding voltage sensors is affected by the height between the sensor and the ground, as well as the distance between the sensor and the telegraph pole. In this paper, a self-calibration method based on internal capacitance transformation is proposed to realize the on-line calibration of suspension grounding voltage sensors. The calibration is accomplished by switching different parameters in the conditioning circuit, and the calibration process does not require power failure or known input excitation. In addition, the impact of electric fields in the other two phases of three-phase transmission lines on measurement through simulation research is quantified in this paper. In order to reduce the impact of interference electric fields, an equipotential shielding structure is designed. The circuit topology and probe prototype have been developed and testing has been conducted in laboratory conditions; the experimental results show that the maximum relative error of voltage amplitude is 1.65%, and the phase relative error is 0.94%. The measurement accuracy is not limited by the height to ground or the distance to the telegraph pole. In addition, in the application of an equipotential shielding probe, the maximum deviation of measured voltage is 0.7% with and without interference electric fields.

Online measurement of capacitor voltage transformer metering errors based on GRU and MTL

The metering accuracy of capacitive voltage transformers (CVTs) affects the fairness of electricity settlement, and the online measurement of their metering errors has become a research hotspot. This error consists of amplitude and phase errors of three-phase voltages. In this paper, because the error data is characterized by time series, nonlinearity, and large volumes, the Gate recurrent unit is selected as a deep learning framework to predict it, the Batch normalization is proposed to prevent gradient disappearance, and the self-attentive mechanism is proposed to help learn long-time information. To measure all six errors simultaneously, multitask learning is employed to mine the shared information and coupling among multiple tasks, and the loss function is reconstructed to ensure simultaneous convergence of the six tasks. Experimental results show that, compared with the traditional single-task model, the accuracy indexes MSE, RMSE, and MAE of the proposed model are reduced by 95.1%, 81.1%, and 89.5% on average for all tasks, and the total training time is reduced by 57.8%; compared with other multitask models, the accuracy indexes are improved by orders of magnitude. This shows that the proposed model fully meets the requirements of both accuracy and speed for online measurement of CVT error.

On the Design of Broadband Truly Balanced Inductor-Less Differential-to-Single-Ended Converter in CMOS Friendly to Wire-Bond Package

This brief presents a broadband inductor-less differential to single-ended (D2S) converter employing complementary structure with series resistor. The developed D2S converter has a unique advantage in terms of amplitude and phase balance performance, achieving true balance in theory and while maintaining wire-bond package friendliness. The D2S converter is validated in a prototype of broadband driver amplifier (DA) for the transmitter front-end and fabricated in 65 nm CMOS process. The measurement results show an amplitude and phase error of less than 0.2 dB and 1∘, respectively, over a frequency range of 0.1 to 6 GHz. The proposed D2S occupies a core chip area of only 0.04×0.1 mm and consumes 6.5–7.4 mW power from a 1.2 V supply voltage.

Using Perfectly Matched Layer in a GPU simulation of ultrasound NDT

Full Waveform Inversion (FWI) is a state-of-the-art method of image reconstruction with promising results for seismology and NDT. FWI estimates the velocity of wave propagation along the inspected object by iteratively comparing acquired data with simulated data. This method is computationally demanding as at least three simulations are needed per iteration, which motivates the research effort for fast simulation methods. When simulating acoustic waves within a finite domain, artificial reflections created at the boundaries yield unrepresentative signal acquisition in the simulation. These reflections disturb the computation of residuals in FWI, creating artifacts that result in inaccurate positioning of flaws and discontinuities. Various absorbing boundary conditions (ABCs) have been proposed to avoid these reflections, e.g., Higdon, Reynolds, and Perfectly Matched Layers (PML). Although Reynolds and Higdon have been used in other applications, they are not well suited for FWI for reasons such as weak absorption rate and excessive introduction of amplitude errors. On the other hand, the PML method, an ABC that gradually attenuates boundary reflections with the addition of layers with matched acoustic impedance, provides adequate attenuation for FWI and can be readily extended to elastic waves. In this work, we describe an implementation of PML in a parallel GPU-accelerated CUDA simulator, which is intended to be integrated into an FWI regression in future works. Finally, we provide examples demonstrating that PML can significantly reduce the domain of simulation of an ultrasound NDT while maintaining simulation accuracy.

A Wideband True Time Delay Circuit Using 0.25 µm GaN HEMT Technology.

This paper presents a wideband 4-bit true time delay IC using a 0.25 μm GaN HEMT (High-Electron-Mobility Transistor) process for the beam-squint-free phased array antennas. The true time delay IC is implemented with a switched path circuit topology using DPDT (Double Pole Double Throw) with no shunt transistor in the inter-stages to improve the bandwidth and SPDT (Single Pole Single Throw) switches at the input and the output ports. The delay lines are implemented with CLC π-networks with the lumped element to ensure a compact chip size. A negative voltage generator and an SPI controller are implemented in the PCB (Printed Circuit Board) due to the lack of digital control logic in GaN technology. A maximum time delay of ~182 ps with a time delay resolution of 10.5 ps is achieved at DC-6 GHz. The RMS (Root Mean Square) time delay and amplitude error are <5 ps and <0.6 dB, respectively. The measured insertion loss is <6.8 dB and the input and output return losses are >10 dB at DC-6 GHz. The current consumption is nearly zero with a 3.3 V supply. The chip size including pads is 2.45 × 1.75 mm2. To the authors' knowledge, this is the first demonstration of a true time delay IC using GaN HEMT technology.

Exponential fitting for interpolation of oscillatory functions. A numerical approach

We develop an entirely numerical approach for the interpolation of the first derivative of an oscillatory function y(x) with frequency ω. Two versions for the number of data at equidistant points xk, k=1,2,…,K are considered: single y(xk) and pair y(xk),y′′(xk), identified by parameter nd with values 1 and 2, respectively. Experimental results show that the accuracies from the new ω-dependent procedure are better than from the polynomial fitting, with a gain which increases with ω. They also show that an approximate value for ω continues to give advantageous results. A special test is reported with respect to the evolution of the error along the interpolation interval. It is found that when nd=1 the errors have the tendency of increasing in amplitude towards the ends, thus following the Runge effect for the interpolation of y(x) but, quite unexpected, when nd=2 the error amplitude is unchanged over the whole interval.

Bioimpedance spectroscopy measurement method based on multisine excitation and integer-period undersampling

Bioimpedance spectroscopy (BIS) is a detection technology that uses the bioimpedance characteristics of human tissues and their changes to analyze their physiological and pathological status, and is widely used in clinical and scientific research applications. Traditional BIS measurement must satisfy the Nyquist sampling theorem so as to ensure that the measurement signal has no frequency aliasing, but at the same time the sampling frequency and the number of sampling points will be increased, which will increase the computation and hardware costs. This paper proposes a novel BIS measurement method based on multisine excitation and integer-period undersampling (IPUS) technology. Firstly, the multisine-based IPUS theory is deduced, and the BIS measurement principle based on multisine excitation and IPUS technology is introduced. Secondly, a BIS measurement system based on a field-programmable gate array + analog-to-digital converter + digital-to-analog converter architecture is designed, and multisine excitation with 32 pseudo-logarithmically distributed frequency components in the range of 2–997 kHz is generated. Comparative BIS measurement experiments on three RC three-element models are carried out under the Nyquist sampling condition (sampling frequency fs = 2.56 MHz) and under the IPUS condition (fs = 512 kHz), respectively. Experimental results show that the mean amplitude error of BIS measurement under the Nyquist sampling condition is 0.80% (±1.19% SD), while the mean amplitude error under the IPUS condition is 1.02% (±1.13% SD). Moreover, the signal-to-noise ratio (SNR z ) is calculated in 40 repeated BIS measurements, where the mean SNR z is 63.60 dB under the IPUS condition, similar to the value of 62.77 dB under the Nyquist sampling condition. The proposed multisine-based IPUS theory and its implementation method in this paper can complete a BIS measurement with only one fundamental period, and the sampling frequency and sampling point requirements are lower than for Nyquist sampling, laying a theoretical and technical foundation for a BIS measurement system with reduced hardware and computation requirements.

Preparation of a superior damping coating and study on vibration damping properties

In this paper, a superior damping coating was prepared, which can be easily sprayed onto the samples, showing a promising application in the vibration reduction for aircraft. This paper aims to investigate the effect of filler content, size and coating thickness on the damping properties of aluminum flake samples. It is found that the vibration of the sample is significantly suppressed with the vibration reduction rate of the coating reaching 63.23%. Moreover, the damping ratio of the coating was calculated using the half-power bandwidth method, based on which the finite element simulation model was established. The simulation results are in perfect agreement with the test ones, and the maximum vibration amplitude error stayed within 9.06%. These results fully demonstrated the effectiveness and practicality of the damping coating.

On designing and developing single‐step second‐order implicit methods with dissipation control and zero‐order overshoots via subsidiary variables

AbstractHilber and Hughes gave several competitive demands on the implicit methods in 1978. However, there are no such integration methods in the traditional algorithm design. Via imposing subsidiary variables, this article proposes two novel implicit methods to splendidly achieve these competitive demands without increasing computational costs. The two novel methods are self‐starting, unconditionally stable, single‐solve, identically second‐order accurate, controllably dissipative, and non‐overshooting. The novel methods achieve the maximal dissipation of auxiliary variables in the high‐frequency limit, although such the design is not a must. The first novel method uses auxiliary velocity and acceleration variables, whereas the second one employs two auxiliary acceleration variables. After embedding desired numerical characteristics, the novel methods employ four eigenvalues of amplification matrices in the high‐frequency limit as user‐specified parameters to flexibly control numerical high‐frequency dissipation. To reduce the number of use‐specified parameters, this article gives some recommended sub‐families of algorithms, such as optimal low‐frequency dissipation schemes. The article further refines the error analysis to analytically calculate amplitude and phase errors for some implicit methods. The error analysis technique can be applied to almost all direct time integration methods. Comparisons of amplitude and phase errors highlight the superiority of the novel methods over the published algorithms. In addition, some classical measures, such as numerical damping ratios and relative period errors, are analyzed and compared. Numerical examples are solved to show the novel methods' superiority.

A Multi-Box Behavioural Nonlinear Mixer Model

ABSTRACT 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.

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 &gt;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 &lt;3.2° and &lt;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.

Dynamic displacement monitoring by integrating high-rate GNSS and accelerometer: on the possibility of downsampling GNSS data at reference stations

We combine accelerometer and asynchronous high-rate GNSS data to retrieve dynamic displacements. The method adopts relative GNSS positioning with observations of different sampling rates at rover and reference stations. The objective is to examine the feasibility of downsampling GNSS data at reference stations and thus, verify whether permanent GNSS networks collecting low-rate observations can serve as reference sites. The performance is assessed using a shake table to induce displacement waveforms. We show that the combined GNSS and accelerometer solution improves displacement accuracy by half compared to the GNSS-only one. Further accuracy improvement is obtained by applying the Rauch Tung Striebel (RTS) smoother. Consequently, it is reasonable to downsample high-rate GNSS data at the reference station even to a 2 s interval and preserve the displacement error below 1 mm. The results also reveal that a fusion of GNSS with accelerometer and RTS smoothing helps to mitigate the ephemeris error. With the assessment in the time–frequency domain, we show that the combined solution better recovers displacement waveforms than GNSS-only. For the former solution, the detected peak frequencies agree very well with those of the Linear Variable Differential Transformer responsible for providing the ground truth displacements, and the amplitude error does not exceed 0.5 mm. We conclude that the proposed approach based on asynchronous GNSS observations provides millimeter-level precision results and is better for reconciling dynamic displacements than a GNSS-only solution or simply integrating accelerometer data.

A Harmonic and Interharmonic Detection Method for Power Systems Based on Enhanced SVD and the Prony Algorithm

To address the problem of harmonic pollution in power systems, a harmonic and interharmonic detection method based on the adaptive order and the dominant factor algorithms is proposed. The proposed method greatly improves the accuracy and precision of harmonic detection, overcoming the notorious problem of high sensitivity to noise of the traditional Prony algorithm that often leads to unsatisfactory detection results. In the proposed method, the “adaptive order determination” algorithm is first used to determine the optimal order of Singular Value Decomposition (SVD) denoising, resulting in a more accurate distinction between signal and noise components. Then, signal reconstruction is carried out to effectively remove noise components to enhance the denoising ability of SVD. This mitigates the Prony algorithm’s high sensitivity to noise and greatly reduces the amplitude of false components in the fitting results. Finally, the dominant factor algorithm is applied to accurately screen out the non-false components in Prony’s fitting results. Simulation results show that the proposed method can effectively reduce signal noise in different noise environments with noise intensities ranging from 5 dB to 30 dB, achieving an average signal-to-noise ratio improvement of around 20 dB. Meanwhile, the identification and screening results of harmonic and interharmonic components in the signal are accurate and reliable, with detection errors in amplitude, frequency, and phase at around 0.5%, 0.01%, and 0.5%, respectively. Overall, the proposed method is well suited for detecting harmonics and interharmonics in power systems under various noise environments.

Design and implementation of high sensitivity microwave radiometer

In this paper, to solve the problem that the square-law baud detection in traditional full power radiometers restricts their sensitivity performance, inspired by the complex correlation algorithm and the Hilbert transformation, an innovative orthogonal autocorrelation microwave radiometer architecture is proposed. This paper solves the mathematical relationship between the additional error of the architecture unit and the temperature measurement sensitivity by establishing the mathematical model of the architecture and using the harmonic balance and the envelope method simulation plugins in ADS.The sensitivity of the autocorrelation architecture is less affected by the additional amplitude error, and the detection accuracy of it is higher when the additional phase and amplitude errors exist. Through the comparison of the two architectures in 12–14 GHz, the test results show that the autocorrelation radiometer is much better than the full power radiometer in temperature sensitivity and detection sensitivity. The temperature of human palm was tested in laboratory environment using the radiometer engineering prototype. To solve the problem of large fluctuations in the output voltage value of the radiometer, a digital integration algorithm is introduced to process the output voltage value. The average error of the radiometer for measuring temperature is decreased from 0.19 °C to 0.034 °C.

Can a failure in the error-monitoring system explain unawareness of memory deficits in Alzheimer’s disease?

Unawareness of memory deficits is an early manifestation in patients with Alzheimer’s disease (AD), which often delays diagnosis. This intriguing behavior constitutes a form of anosognosia, whose neural mechanisms remain largely unknown. We hypothesized that anosognosia may depend on a critical synaptic failure in the error-monitoring system, which would prevent AD patients from being aware of their own memory impairment. To investigate, we measured event-related potentials (ERPs) evoked by erroneous responses during a word memory recognition task in two groups of amyloid positive individuals with only subjective memory complaints at study entry: those who progressed to AD within the five-year study period (PROG group), and those who remained cognitively normal (CTRL group). A significant reduction in the amplitude of the positivity error (Pe), an ERP related to error awareness, was observed in the PROG group at the time of AD diagnosis (vs study entry) in intra-group analysis, as well as when compared with the CTRL group in inter-group analysis, based on the last EEG acquisition for all subjects. Importantly, at the time of AD diagnosis, the PROG group exhibited clinical signs of anosognosia, overestimating their cognitive abilities, as evidenced by the discrepancy scores obtained from caregiver/informant vs participant reports on the cognitive subscale of the Healthy Aging Brain Care Monitor. To our knowledge, this is the first study to reveal the emergence of a failure in the error-monitoring system during a word memory recognition task at the early stages of AD. This finding, along with the decline of awareness for cognitive impairment observed in the PROG group, strongly suggests that a synaptic dysfunction in the error-monitoring system may be the critical neural mechanism at the origin of unawareness of deficits in AD.