Offset Compensation Research Articles

Sensing offset analysis and compensation of a capacitive displacement transducer for space inertial sensors

Abstract Capacitive displacement transducers play a crucial role in inertial sensors especially for space gravitational wave detection missions. One of the major requirements for the displacement transducer is to have a lower sensing offset. The sensing offset will adversely affect the accuracy of the absolute position measurement of the test mass, providing erroneous data to the drag-free controller and leading to spacecraft mispositioning. Additionally, the offset could introduce multiplicative noise to the sensing output and the closed loop output of the inertial sensor. The asymmetry of the sensing bridge within the front-end electronics has been identified as the primary source of these offsets. This paper analyzes the requirements of the main parameters in the sensing bridge. A method is proposed to reduce the sensing offset by utilizing differentiated resonant capacitors while maintaining the ability to tune the resonant frequency and ensure a sufficiently low sensing noise level. Experimental results show that this approach can effectively reduce the residual sensing offset to (−15.7 ± 5.0) ppm, which satisfies the stringent requirement for space inertial sensors in the TianQin mission.

Investigation of laser phase noise tolerance in simplified coherent PON with subcarrier multiplexing

In this paper, we experimentally investigate the laser phase noise tolerance for a 100 Gb/s/λ coherent passive optical network (PON) with simplified optical network units (ONUs) transceivers when distributed feedback (DFB) laser is used as the local oscillator (LO). In the proposed scheme, the digitally subcarrier-multiplexed (DSCM) signals are generated in the coherent transmitter at the optical line terminal (OLT) side based on Alamouti encoding in two polarizations and received by a single-polarization heterodyne receiver at the ONU side. The experimental results show that the power budget can achieve 34.2 dB and 33.9 dB after a 25 km standard single-mode fiber (SSMF) link when external cavity laser (ECL) and DFB lasers are used as the LOs at the ONU side. Polarization and carrier phase tracking schemes for the DSCM systems based on frequency domain pilot tones were used in digital signal process (DSP). At the same time, the frequency offset estimation and phase noise compensation algorithms are conducted using residual carriers. By choosing an appropriate width for the low-pass filter, the optimal performance for the phase noise compensation can be achieved. The pre-equalization operation at the OLT side is also verified for the subcarrier-multiplexed signals to provide better and flatter performances.

Dataset Augmentation and Fractional Frequency Offset Compensation Based Radio Frequency Fingerprint Identification in Drone Communications

Dataset Augmentation and Fractional Frequency Offset Compensation Based Radio Frequency Fingerprint Identification in Drone Communications

A Better Sense Amplifier Improves the Resilience in Compute-In-Memory and Row Hammer

As machine learning (ML) workloads continue to scale, the demand for higher-density DRAM (Dynamic Random-Access Memory) and SRAM (Static Random-Access Memory) is intensifying, and also driving interest in compute-in-memory (CIM) architectures as a promising approach to enhancing computational efficiency. However, increasing DRAM cell density introduces significant challenges, particularly in the reliable identification of charge sharing between cells and bit lines. This challenge heightens the susceptibility of DRAM to row hammer attacks, where unintended data corruption occurs due to repeated access to adjacent rows. Furthermore, CIM architectures necessitate more precise sensing of bit lines to ensure accurate computation within memory. In light of these challenges, our study proposes an investigation into the potential benefits of utilizing an offset compensation sense amplifier (OCSA). The OCSA is designed to address the accuracy limitations posed by high-density DRAM in CIM applications. By enhancing the precision of bit line sensing, the OCSA may mitigate the vulnerability to row hammer attacks and improve the overall reliability and performance of CIM architectures. This study will explore the effectiveness of the OCSA in maintaining data integrity and computational accuracy within high-density DRAM environments, offering insights into its applicability for future ML workloads.

Sampling frequency offset compensation scheme based on machine learning for MB-OFDM UWBoF system

Digital to analogue converter (DAC) at the transmitter side and analogue to digital converter (ADC) at the receiver side with not exactly same clock period leads to sampling frequency offset (SFO) that affects the performance of multi-band ultra-wideband orthogonal frequency division multiplexing over fiber (MB-OFDM UWBoF) system, four machine-learning algorithms are proposed for compensating the SFO for the system and are compared in this paper. Simulation results show that the best compensation among the three conventional machine learning algorithms after 100 km standard single mode fiber (SSMF) transmission is the self-organising mapping (SOM) algorithm, which is able to compensate the SFO in the range of ±150 ppm, with a high complexity. The next best is the conventional kmeans algorithm which can compensate ±40 ppm and is slightly better compared to the density-based spatial clustering of applications with noise (DBSCAN) algorithm. The DBSCAN algorithm only compensates around ±25 ppm of SFO, when the constellation points are slightly chaotic, the wrong cluster results in failure of demodulation, which makes it less applicable for problems of SFO. Moreover, the improved kmeans algorithm proposed in this paper can compensate the SFO of ±225 ppm, better than three conventional machine learning algorithms. And it can still make the BER lower than 3.8e-3 at received optical power (ROP) of −15 dBm when the SFO is 225 ppm.

W-band photonic-aided mm-wave ISAC system enabled by a shared OFDM signal waveform and a two-stage carrier frequency recovery algorithm.

Integrated sensing and communication (ISAC) systems will play a potential role in the upcoming six-generation (6G) networks. The reason is that ISAC systems can effectively solve the spectrum resource shortage problem and decrease the cost of deploying hardware equipment for simultaneously realizing communication and sensing. In this Letter, we successfully realize a W-band photonic-aided millimeter-wave (mm-wave) ISAC system enabled by a shared orthogonal-frequency-division-multiplexing (OFDM) signal waveform and two-stage carrier frequency recovery (CFR) algorithm. The digital-signal-processing (DSP)-based two-stage CFR algorithm includes the first-stage fractional frequency offset (FFO) estimation and compensation as well as the second-stage integer frequency offset (IFO) estimation and compensation. We experimentally analyze and verify that, with the introduction of the two-stage CFR algorithm, the system robustness to carrier frequency offset can be significantly enhanced. We also experimentally demonstrate, based on the ISAC system and our receiver DSP, a net data rate of up to 47.54 Gbit/s with a total signal bandwidth of 16 GHz over a 5.2 m wireless link at 94.5 GHz. Moreover, the sensing results indicate that the ISAC system can realize the detection of one target 2 m away from the transmitter with a ranging resolution of 0.98 cm and a ranging error of 4 mm. The system is anticipated to facilitate diverse potential applications in future 6G networks.

Coarse frequency offset estimation and compensation based on short-time spectrum analysis in FSO communication system

Due to the high-speed movement of low-orbit satellites, the Doppler frequency offset in 1550-nm wavelength satellite-to-ground coherent laser communication is as high as ±4.5 GHz, which greatly increases the difficulty of carrier frequency acquisition. Low complexity, short capture time, and stable coarse frequency offset estimation and compensation algorithms are technical bottlenecks that must be addressed. In this work, a coarse frequency offset estimation and compensation algorithm based on short-time spectrum analysis is proposed. In the proof-of-principle system, the feasibility of the coarse frequency offset capture is verified based on a 2.5-GBaud data rate PM-QPSK modulation FPGA-based coherent receiver. The results show that the frequency offsets capture range is extended to ±4.5 GHz, covering the Doppler frequency offset range. Moreover, the standard deviation of the residual frequency offset after coarse frequency offset compensation is less than 140 MHz, which is smaller than the accurate frequency offset compensation range of 312.5 MHz.

A high-speed dynamic comparator with automatic offset calibration

A high-speed dynamic comparator with preamplifier and automatic dc offset calibration in all stages is proposed in this paper. The offset compensation is applied in two stages, following a two-part sequential loop training topology, offering significant reduction of the dc offset in each stage. The final resolution is improved with a final value less than 800 μV operating at 7.5 GHz clock speed. The dynamic comparator stage is a double-tail topology while the calibration topology is based on a current injection technique, instead of the commonly used capacitive calibration which can reduce the operating speed. Designed in a CMOS 65 nm technology node, the circuit operates with 1 V supply voltage. Results of PVT Monte Carlo post-layout simulations verify the operation of the proposed topology.

Dual-chirp-based photonic THz-ISAC system with adaptive frequency synchronization.

Recent advancements have brought significant attention to photonic terahertz (THz)-integrated sensing and communication (ISAC) systems. In this work, we present an adaptive frequency offset (FO) compensation method for dual-chirp-based ISAC waveforms, using the fractional Fourier transform (FrFT) method. The proposed scheme can enable frequency synchronization without a need for training preambles and exhibit robustness against system noise. We validate this approach through an experimental demonstration in a 300 GHz photonic THz-ISAC system with 20 Gbps quadrature-phase shift keying (QPSK) data transmission and 1.5 cm range resolution. The experiment successfully compensates for frequency offsets ranging from -5 to 5 GHz, achieving an estimation error of less than 0.08% and a chirp-pilot power overhead of 0.5%.

IQ-channel multiplexed DP-4ASK signal using power loading for downlink coherent PON system with access-span length difference

This study explores the integration of dual-polarized (DP) four-level amplitude shift keying (4ASK) signals within an intensity and quadrature division multiplexing framework, mainly focusing on coherent passive optical network (PON) systems. The primary objective is to address the challenges associated with distance disparities in downstream transmissions, which are prevalent in coherent PON architectures. We introduce a novel approach that significantly reduces the power consumption of digital-to-analog converters by implementing power loading strategies tailored explicitly for IQ channel division multiplexing (IQDM)-DP-4ASK signals. Our simulations confirm that ASK standard frequency offset compensation is adaptable to these signals, providing a robust method for managing frequency offsets in a dynamic network environment. Moreover, we propose and empirically validate an energy-efficient adaptive downlink solution capable of supporting 128 Gb/s per optical network unit (ONU), utilizing IQ-imbalanced DP-4ASK signals. This solution is particularly advantageous for systems where the transmission conditions include a 10 km variance in access span lengths between ONUs. Results from our experimental setup demonstrate that reducing the digital-to-analog converter output current for the Q channel by 137 mA is feasible without compromising signal integrity or system performance. Additionally, the research verifies the effectiveness of the automatic bias controller on the transmitter side, ensuring stable operation across varying conditions. Equally, the receiver-side digital signal processing effectively handles polarization separation, illustrating the system's capability to maintain high data integrity and reliability under diverse operational scenarios. These findings highlight the technical feasibility and operational benefits of using IQDM-DP-4ASK signals in coherent PON systems and underscore the potential for significant power savings and enhanced system efficiency in optical networks. The study paves the way for future research into scalable, energy-efficient solutions suitable for high-capacity optical access networks striving for increased sustainability and reduced operational costs.

Biodiversity Offset Mechanisms and Compensation for Loss from Exceptional to Popular: Rediscovering Environmental Law

The use of compensatory mechanisms for biodiversity conservation, also known as biodiversity offsets, has increased significantly in recent decades. The Kunming Montreal Global Biodiversity Framework mentions them as an innovative scheme in support of substantially and progressively increasing the level of financial resources for biodiversity conservation. This article traces the origin of compensatory mechanisms in international environmental law and their development in transnational biodiversity governance. The article points to the shifts in the application of the biodiversity offsets: from the context of wetlands to other habitats and ecosystems; from its use in intergovernmental conventions to an increasing number of transnational (business) networks; and from an instrument of last resort to a source of additional funding for biodiversity conservation. In the evolution, compensatory mechanisms have been decoupled from their original purpose as an exceptional mitigation measure and a strong focus of environmental law on the preventive function. The increased rhetoric of commitment to no net loss, net gain, restoration, and the mitigation hierarchy has not been matched by an improved status of wetlands and other ecosystems. The processes within the biodiversity conventions (Ramsar and CBD) have accepted an ongoing destruction of nature and limited the role of environmental law to minimizing harmful impacts on nature and consolidating the decline, rather than shaping socio-ecological outcomes. An ambiguous position about the spread of compensatory mechanisms has been part and parcel of this; biodiversity conventions have neither endorsed nor distanced themselves from the application, promotion, and justification of compensatory mechanisms. To maintain the integrity of environmental law, the rules that prevent biodiversity loss need to be emphasised and enforced.

Offset compensation for differential charge‐based capacitance measurement

Offset compensation for differential charge‐based capacitance measurement

OFDM Modulation Classification Using Cross-SKNet With Blind IQ Imbalance and Carrier Frequency Offset Compensation

OFDM Modulation Classification Using Cross-SKNet With Blind IQ Imbalance and Carrier Frequency Offset Compensation

A hardness-based constitutive model for numerical simulation of blind rivet with gradient hardness distribution

A286 superalloy blind rivets find extensive applications in the structural connections of aerospace equipment owing to their exceptional strength and heat resistance. However, the gradient hardness distribution within the rivet sleeves complicates achieving precise numerical simulation results with traditional constitutive models. This study aims to establish a constitutive model suitable for materials exhibiting gradient hardness to support the development of A286 superalloy blind rivets. Initially, quasi-static compression experiments were conducted on A286 superalloy samples at different hardness levels (160–324 HV), strain rates (0.01–10 s⁻¹), and temperatures (25–600°C). Subsequently, the influence of material microstructural evolution on flow stress during compression was investigated using electron backscatter diffraction technique. Furthermore, a hardness-based Johnson-Cook (J-C) constitutive model was developed by introducing hardness and offset compensation onto the original J-C model and compared with its counterpart. Finally, the hardness-based model was employed to simulate the bulge compression forming of A286 blind rivets and validated through experimental trials. The findings reveal that dislocation strengthening predominantly contributes to the increased material flow stress with escalating strain rates and sample hardness. Compared to the original J-C model, the stress prediction error of the hardness-based model reduced from 26.8 % to 2.9 %, effectively depicting the variation in material flow stress under different hardness values. The simulated values of bulge morphology, dimensions, and load closely align with experimental data, affirming the efficacy of the hardness-based model in numerically simulating blind rivets with gradient hardness distribution.

Sampling Frequency Offset Estimation and Compensation for Asynchronous Optical IMDD FBMC Systems

Sampling Frequency Offset Estimation and Compensation for Asynchronous Optical IMDD FBMC Systems

A Capacitance Monitoring Strategy Based on Offset Error Compensation for Modular Multilevel Converters

The modular multilevel converter (MMC) is a research hotspot in medium-voltage and high-voltage applications. The measurement offset error would cause an increase in the monitoring error of the submodule (SM) capacitance of the MMC, affecting the estimation accuracy of the SM capacitance monitoring. This paper proposes a capacitor monitoring strategy based on the offset error compensation, where two reasonable capacitor monitoring periods are selected in one fundamental period under the proposed voltage-balancing control (VBC) based on the virtual capacitor voltage (VCV) to compensate for the offset error impact on the capacitance monitoring. The proposed strategy can effectively eliminate the offset error impact on the capacitance monitoring, which ensures the accuracy of the SM capacitance monitoring in the MMCs. The effectiveness of the proposed monitoring strategy is confirmed by the simulations and experiments.

A Current-Mode Analog Front-End for Capacitive Length Transducers in Pneumatic Muscle Actuators.

This paper reports on the design, implementation, and characterization of a current-mode analog-front-end circuit for capacitance-to-voltage conversion that can be used in connection with a large variety of sensors and actuators in industrial and rehabilitation medicine applications. The circuit is composed by: (i) an oscillator generating a square wave signal whose frequency and pulse width is a function of the value of input capacitance; (ii) a passive low-pass filter that extracts the DC average component of the square wave signal; (iii) a DC-DC amplifier with variable gain ranging from 1 to 1000. The circuit has been designed in the current-mode approach by employing the second-generation current conveyor circuit, and has been implemented by using commercial discrete components as the basic blocks. The circuit allows for gain and sensitivity tunability, offset compensation and regulation, and the capability to manage various ranges of variations of the input capacitance. For a circuit gain of 1000, the measured circuit sensitivity is equal to 167.34 mV/pF with a resolution in terms of capacitance of 5 fF. The implemented circuit has been employed to measure the variations of the capacitance of a McKibben pneumatic muscle associated with the variations of its length that linearly depend on the circuit output voltage. Under step-to-step conditions of movement of the pneumatic muscle, the overall system sensitivity is equal to 70 mV/mm with a standard deviation error of the muscle length variation of 0.008 mm.

An FFT-Based DC Offset Compensation and I/Q Imbalance Correction Algorithm for Bioradar Sensors

An FFT-Based DC Offset Compensation and I/Q Imbalance Correction Algorithm for Bioradar Sensors

Capacitor Voltage Balancing Control of MMC Sub-Module Based on Neural Network Prediction

The issue of sub-module (SM) capacitor voltage unbalance is a hot topic in the current research into the modular multilevel converter (MMC). An excellent strategy comprises mitigating the SM capacitor voltage imbalance by adjusting the SM on time. The traditional capacitor voltage balancing control regulates the speed to maintain accuracy. A unique SM capacitor voltage balancing control strategy is presented in this paper and is based on conventional capacitor voltage balance management and neural network prediction. Firstly, the SM capacitor voltage and arm current are speculated by operating the time series forecasting technique in real time, considering the dynamic changes in the SM capacitor voltage and arm current. Secondly, the SM capacitor voltage distinction between the actual and theoretical value is determined, and a deviation’s mixed Gaussian distribution is established to estimate its compensation voltage. Thirdly, the SM triggering sequence is anticipated by using the neural network along with the pilot values of the SM capacitor voltage, arm current, and the offset compensation value, and the control is executed. Finally, a three-phase, six-leg, eight-module, nine-level MMC model is built to verify the feasibility of the suggested approach.

Joint equalization of frequency offset and phase noise using two-stage cascaded extended Kalman filter for discrete spectrum 16/64APSK NFDM systems.

For the discrete spectrum nonlinear frequency division multiplexing (DS-NFDM) 16/64 amplitude phase shift keying (APSK) system, the inevitable laser impairments including frequency offset (FO) and carrier phase noise (CPN) would cause different rotations of the received signal constellations. In addition, the combined effect of FO and amplifier spontaneous emission (ASE) noise induces the eigenvalue shift, accordingly the residual channel impairment (RCI) is inevitably yielded. To address the above problems, we deduce the joint impairment model of FO, CPN and RCI, and then propose a joint equalization scheme using two-stage cascaded extended Kalman filter (TSC-EKF) for these impairments. It performs frequency offset compensation in the first stage, subsequently carries out joint equalization of CPN and RCI in the second stage. Meanwhile, the minimum Euclidean distance and phase difference between the received symbols and the ideal 16/64APSK constellations are ingeniously fused to calculate the innovations of TSC-EKF. The effectiveness has been verified by 2 GBaud DS-NFDM 16/64 APSK simulations and DS-NFDM 16APSK transmission experiments. The results demonstrate that when performing the joint equalization of FO, CPN and RCI, the maximum FOE range of TSC-EKF scheme achieves 1.2 and 9.6 times as that of nonlinear frequency domain (NFD) scheme and fast Fourier transform -Like (FFT-Like) scheme, respectively. Furthermore, its maximum LW tolerance reaches 3.3 times as that of the M-th power scheme. Importantly, the complexity of TSC-EKF is 63.4% as that of NFD scheme and on an order of O(N).