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In the past decade, the proliferation of modern telecommunication technologies, including 5G, and the widespread adoption of the Internet-of-things (IoT) have led to an unprecedented surge in data generation and transmission. This surge has created an escalating demand for advanced signal processing capabilities. Microwave photonic (MWP) processors offer a promising solution to satisfy this unprecedented demand for data processing by capitalising on the high bandwidth and low latency achievable by optical systems. In this work, we introduce an integrated MWP processing unit for all-optical RF filtering using elemental antimony. We exploit the crystallisation dynamics of antimony to demonstrate a photonic leaky integrator, which is configured to operate as a first-order low-pass filter with a bandwidth of 300 kHz and ultra-compact footprint of 16 × 16 μm . We experimentally demonstrate the implementation of such a filter as an envelope detector to demodulate an amplitude-modulated signal. Finally, a discussion on achieving bandwidth tunability is presented.

This article presents a non-AC-side voltage sensor control method applied to More Electric Aircraft rectifiers. The control strategy can operate properly over a wide range of frequencies. This strategy calculates the AC supply frequency through an instantaneous phase-locked loop and feeds it back to a dual low-pass filter. The reconstructed rectifier-side voltage is filtered using two low-pass filters with different scale factors. Then, the values of the two filter outputs are subtracted and the effect of the DC bias due to the initial value of the integration is eliminated. The subtracted value is amplitude-phase compensated to calculate the virtual flux value. The phase angle can then be calculated from the virtual flux value. This phase angle is used for the implementation of the voltage-oriented vector control and as an input to the instantaneous phase-locked loop. Simulation and experimental results show that the use of dual low-pass filters under different frequency conditions improves the speed and accuracy of virtual flux estimation and eliminates DC-side bias errors.

This letter presents a subthreshold second‐order transconductor–capacitor (Gm‐C) low‐pass filter (LPF) for portable biomedical applications. To broaden the range of linear signal processed by the filter, we modified the source–follower biquad and proposed an advanced gm cell based on source‐coupled pair (SCP). The implementation of self‐cascode composite transistors (SC) in the gm cell resulted in a notable enhancement of the filter's linearity and dynamic range (DR) while maintaining a low power consumption level. The circuit simulations using a 55‐nm CMOS process verified that the proposed filter consumes 4.6 nW and contributes input‐referred noise (IRN) of 104 µVrms at a cut‐off frequency of 100 Hz. Furthermore, the LPF attains DR and figure of merit (FoM) values of 63.88 dB and 14.71 fJ, respectively, which is a potential candidate for biomedical applications. In this letter, a 4.6‐nW, 100‐Hz, 63.88‐dB DR, second‐order subthreshold Gm‐C filter has been discussed, and the figure of merit is 14.71 fJ, which is a potential candidate for portable biomedical applications.

Precise pose estimation is crucial to various robots. In this paper, we present a localization method using correlative scan matching (CSM) technique for indoor mobile robots equipped with 2D-LiDAR to provide precise and fast pose estimation based on the common occupancy map. A pose tracking module and a global localization module are included in our method. On the one hand, the pose tracking module corrects accumulated odometry errors by CSM in the classical Bayesian filtering framework. A low-pass filter associating the predictive pose from odometer with the corrected pose by CSM is applied to improve precision and smoothness of the pose tracking module. On the other hand, our localization method can autonomously detect localization failures with several designed trigger criteria. Once a localization failure occurs, the global localization module can recover correct robot pose quickly by leveraging branch-and-bound method that can minimize the volume of CSM-evaluated candidates. Our localization method has been validated extensively in simulated, public dataset-based, and real environments. The experimental results reveal that the proposed method achieves high-precision, real-time pose estimation, and quick pose retrieve and outperforms other compared methods.

This paper presents three different optimization cases for normalized fractional order low-pass filters (LPFs) with numerical, circuit and experimental results. A multi-objective optimization technique is used for controlling some filter specifications, which are the transition bandwidth, the stop band frequency gain and the maximum allowable peak in the filter pass band. The extra degree of freedom provided by the fractional order parameter allows the full manipulation of the filter specifications to obtain the desired response required by any application. The proposed mathematical model is further applied to a case study of a practical second- generation current conveyor (CCII)-based fractional low-pass filter. Circuit simulations are performed for two different fractional order filters, with orders 1.6 and 3.6, with cutoff frequencies 200 and 500 Hz, respectively. Experimental results are also presented for LPF of 4.46 kHz cutoff frequency using a fabricated fractional capacitor of order 0.8, proving the validity of the proposed design approach.

The Recursive Pseudo Random Pursuit Strategy (RPRPS) is proposed to predict the frequency difference of atomic clocks relative to reference. It further improves the computational efficiency and reduces the time complexity. The core of RPRPS is to replace the refitting of the updated predictor and recalculating of the sum of square residuals of the unupdated predictors in a recursive process. In experiments, it is employed to predict the readings of the cesium clock and hydrogen maser relative to UTC (NIM). Compared with PRPS, the experimental results show that RPRPS reduces running time by about 70% without reducing predictive accuracy. This paper proposes a recursive prediction algorithm suitable for the relative frequency difference readings of atomic clocks. It has the characteristic of low time complexity. The initialisation process of the algorithm is shown in Figure 1, and the recursive update process is shown in Figure 2.

Purpose The purpose of this paper is to derive a new fractal active low-pass filter (LPF) within the local fractional derivative (LFD) calculus on the Cantor set (CS). Design/methodology/approach To the best of the author’s knowledge, a new fractal active LPF within the LFD on the CS is proposed for the first time in this work. By defining the nondifferentiable (ND) lumped elements on the fractal set, the author successfully extracted its ND transfer function by applying the local fractional Laplace transform. The properties of the ND transfer function on the CS are elaborated in detail. Findings The comparative results between the fractal active LPF (for γ = ln2/ln3) and the classic one (for γ = 1) on the amplitude–frequency and phase–frequency characteristics show that the proposed method is correct and effective, and is expected to shed light on the theory study of the fractal electrical systems. Originality/value To the best of the author’s knowledge, the fractal active LPF within the LFD calculus on the CS is proposed for the first time in this study. The proposed method can be used to study the other problems in the fractal electrical systems, and is expected to shed a light on the theory study of the fractal electrical systems.

It is well known that fully differential signal processing is more advantageous than single-ended signal processing in a noisy environment, and is widely used in audio, video and other signal processing applications. This paper introduces a new fully differential configuration that contains a first-order low-pass (LP) filter, high-pass (HP) filter, and all-pass (AP) filter, all present within the same circuit design. The proposed fully differential configuration is simple and employs only one multiple-output current differencing transconductance amplifier and one grounded capacitor. The circuit has a wide operating frequency range (up to 73 MHz). The additional features offered by the proposed circuit include use of the lowest number of active and passive components, suitability of the integrated circuit chip, support of cascadability, electronic tunability, no passive component-matching restrictions, availability of all first-order responses, i.e., LP, HP, and AP, and low-level operating supply voltages. Non-ideal and parasitic analyses are investigated for the proposed circuit, and PSPICE simulation results are presented to verify the proposed theory. Additionally, the proposed fully differential LP filter circuit is experimentally verified using off-the-shelf ICs. Moreover, the cascading feasibility is demonstrated by realizing a fully differential nth-order LP filter.

In this paper two new first order filter topologies realizing low-pass/all-pass (LP/AP) and low-pass/high-pass (LP/HP) outputs using electronically controllable second generation voltage conveyors (CVCIIs) are presented. Unlike second generation voltage conveyors (VCII), in CVCII each performance parameter, including ports, parasitic impedances, current and/or voltage gains can be electronically varied. Here, in particular, the proposed filter topologies are based on two CVCIIs, one resistor and one capacitor. In the first topology VLP/IAP/VAP and in the second topology ILP/VLP/IHP/VHP outputs are achievable, respectively. However, the current and voltage outputs are not achievable simultaneously and a floating capacitor is used. A control current (Icon) is used to change the first CVCII Y port impedance, which sets the filter −3 dB frequency (f0) of all the outputs. Moreover, in the second topology, the gains of HP and AP outputs are electronically adjusted by means of a control voltage (Vcon). Favorably, no restricting matching condition is necessary. PSpice simulations using 0.18 µm CMOS technology and supply voltages of ±0.9V show that by changing Icon from 0.5 µA to 50 µA, f0 is varied from 89 kHz to 1 MHz. Similarly, for a Vcon variation from −0.9 V to 0.185 V, the gains of IAP and IHP vary from 30 dB to 0 dB and those of VAP and VHP vary from 100 dB to 20 dB. The total harmonic distortion (THD) is about 8%. The power consumption is from 0.385 mW to 1.057 mW.

This paper proposes a new design method of energy management strategy (EMS) with adaptive super-twisting sliding mode control (ASTSMC) for fuel cell/battery/supercapacitor hybrid vehicle (FCHEV). The main objective of the proposed EMS is to improve power performance, fuel cell lifetime, and fuel consumption while considering the regulation of the DC-bus voltage. The proposed EMS is designed based on a frequency-decoupling technique using an adaptive low-pass filter, Harr wavelet transform (HWT), and FLC to decouple the required power into low, medium, and high-frequency components for fuel cell, battery, and supercapacitor, respectively. The presented frequency-decoupling-based strategy can improve the power performance of the vehicle as well as reduce load stress and power fluctuation in the fuel cell. Nevertheless, the neural network optimization algorithm (NNOA) is employed to optimize the membership functions of FLCs while considering the hydrogen consumption and constraints on the state of charge (SOC) of the battery and supercapacitor. To achieve robustness and high precision control, the ASTSMC is developed based on a nonlinear disturbance observer (NDOB) to stabilize the DC-bus voltage and currents of the energy sources, ensuring that the fuel cell, battery, and supercapacitor track their obtained reference values. The FCHEV system with the proposed EMS is modeled on MATLAB/Simulink, and three typical driving cycles such as HWFET, UDDS, and WLTP driving schedules are used for evaluation. The findings exhibit that the proposed EMS can effectively improve the fuel economy, reduce power fluctuation in the fuel cell, and prolong its lifetime compared to other existing methods such as the equivalent consumption minimization strategy (ECMS), state machine (SM), and FLC-based EMSs.