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This paper proposes an improved multiple synchronous reference frame (MSRF) current harmonic regulation strategy for dual three phase permanent magnet synchronous machine drive system. A new vector space decomposition transformation combined with auxiliary currents is designed to decouple the current fundamental with current harmonics, and the auxiliary currents can be established by the /9 phase shifting of the physical currents in ABC set and the /18 phase shifting of the physical currents in XYZ set. By employing the proposed current decomposition, it is easy to detect them using low pass filters in MSRFs. A generic complex vector proportional integral regulator is then employed to control the detected current harmonics to track the current harmonic references. Compared with the existing MSRF-based methods, the proposed method provides a new current harmonic detection with reduced delay effect, which contributes to enhancing the dynamic performance of current harmonic regulation, and also stabilizing the control system. Comprehensive experimental results are given to validate the effectiveness of the proposed control strategy.

This study deals with a new approach to tackle the challenges encountered in the filters-based reactive power calculation techniques utilized in the control system of Static VAr compensators (SVCs). In this approach, step and time-varying responses are improved by a combination of differential and filter-based methods. Then, optimum values of the main parameters of the low-pass and band-stop filters are determined considering three criteria: accuracy, speed, and capability for following the time-varying loads. To assess the performance of proposed method, a new objective function is introduced, calculated for two sets of signals, captured from a real filed in Mobarakeh Steel Company (MSC) in Isfahan/Iran. Then, the proposed and the other reactive power calculation methods are assessed in practice and simulation. Also, the algorithm is implemented using a TMDSCNCD28335 as the processor to assess the real-time feasibility of the method. To do so, reactive power variation of an electrical arc furnace is emulated in a prototype test bench and the algorithm is run in real-time by the processor during the system operation.

Compared with current source converters, voltage source converters (grid-forming converters) have better frequency support capabilities, voltage support capabilities, and regulation performance, thus they have broad application prospects. However, the grid-forming (GFM) converter has insufficient current control ability, and it easily causes problems such as overcurrent issues when a fault occurs. Thus, this insufficiency is one of the most important challenges the GFM converter is faced with. Aiming to solve the problems mentioned above, this paper proposes a control method of a GFM converter achieved with a low-pass filter structure and an additional current loop. The additional current loop controls the dq-axis current components by acting on the outer loop to generate appropriate phase and voltage amplitude reference. The low-pass filter structure is used to solve the system frequency stability problem caused by the inclusion of the additional current loop. On the premise of ensuring that the system frequency meets the grid-connection requirements, the proposed strategy rapidly limits the output current within the allowable range and guarantees expected voltage source characteristics of the converter during the fault period. Finally, the effectiveness and superiority of the proposed control strategy are verified by MATLAB/Simulink simulations.

The extra acoustic noise caused by the high–frequency (HF) signal injection imposes restrictions on its extensive applications for sensorless synchronous reluctance motor (SynRM) drives. To attenuate the undesired acoustic noise further, a hybrid pseudorandom signal injection scheme is proposed in this paper. The hybrid pseudorandom signal injection is implemented by injecting square wave signals chosen in a random manner from a set of signals having either different frequency or phase from each other. The optimal assembly of hybrid pseudorandom signals is designed via current power spectral density analysis, aiming at reducing acoustic noise as much as possible. In this way, the proposed scheme achieves a success in a massive acoustic noise reduction by means of completely eliminating the discrete harmonics of the current spectrum and distributing the current spectrum to a wider range. Besides, the low pass filters used to separate the fundamental frequency component from injected HF components of currents could be eliminated, because no discrete harmonics at injected frequencies exist with the proposed hybrid pseudorandom signal injection. The validity and superiority of the proposed sensorless control scheme are verified on a 3-kW position sensorless SynRM drive platform.

High-speed digitizers operating at sampling rates higher than 10GS/s require low-pass anti-aliasing filters in the multi-GHz range. Asynchronous Time-Interleaved (ATI) digitizers also need low-pass filters before digitization, and additional requirements on their design are set by this specific application. In integrated solutions, inductor-less filters are important for minimizing the chip area footprint. In this paper, we present the design of a 6th-order inductor-less 10GHz low-pass filter implemented in the STMicroelectronics SiGe BiCMOS55 process. It can be used as anti-aliasing filter for conventional 30GS/s digitizers or at the output of a 40GS/s ATI digitizer. We exploit positive feedback to synthesize the active inductor based on a stacked topology, minimizing the number of current branches, and thus power consumption. Analysis and design guidelines for the biquad are presented. The filter exhibits a bandwidth of 10GHz with a power consumption of 43mW, a THD of -45dB and an SNR of 43dB with an input amplitude of 710mV peak-to-peak differential. Extensive corner and Monte Carlo post-layout simulations have been carried out to highlight the robustness of the circuit to PVT and mismatch variations. Experimental results have confirmed very good agreement between measured and simulated performance, validating the proposed design flow.

The LCL filter has been widely used in the grid-tied inverter systems. However, the resonance of the LCL filter can reduce the system stability margin and the control performance. Moreover, the grid impedance variations can lead to the drift of the resonant frequency, which can further worsen the system robustness. Thus, it is important to know the actual resonant frequency of the LCL filter. In this letter, an adaptive extremum seeking control (AESC) based estimation scheme is proposed to estimate the resonant frequency of the LCL filter online. By injecting a high-frequency (HF) signal into the inverter output voltage, the AESC scheme can identify the extremum of the LCL filter amplitude response, i.e., resonant peak. The amplitude of injection signal is adaptive based on the inverter HF response, which can address the tradeoff between the dynamic response and inverter output current quality. Most importantly, compare to other method, the proposed scheme has very low computational complexity, which minimizes the burden to the normal inverter controller operation. Stability analysis is given in this letter, and experimental studies are conducted to validate the effectiveness of the proposed scheme.

By using integrated lumped elements based on through-silicon via (TSV) technology, a 3-D low-pass filter (LPF) with ultracompact size and ultrawide stopband is proposed. The 3-D magnetic coupling is enhanced between microsize spiral inductors to increase the mutual inductance and improve the high-frequency performance. A coaxial TSV with enhanced capacitance in high resistivity silicon (HRS) is utilized both as capacitor and as a vertical interconnection without any overhead in area and routing. The 3-D nature of the proposed filter yields a miniaturized size of 0.2 x 0.10 mm². The LPF is analyzed with equivalent circuit model and validated with the well-matched S-parameters obtained by finite element method simulation and measurement. With -3-dB cutoff frequency at 2.6 GHz, the LPF exhibits an insertion loss below 1 dB, a reflection loss over 17 dB in the passband, and a suppression level over 20 dB from 5.28 up to 40 GHz in the stopband.

Design procedure of a novel transmission line low‐pass filter is presented. The filter has a flexible rejection response for a prescribed cut‐off frequency and an in‐band ripple factor. It is compact by using a Z‐shaped coupled‐line section, which is loaded with open‐circuited stubs. All of the transmission line elements are identical in electrical length, and the impedances can be calculated by solving certain specific equations according to prescribed in‐band specifications. The simulated results show that the circuit can generate low‐pass responses with third‐, fifth‐, and seventh‐order filtering functions. The filter order depends on the number and position of the loading stubs. For verification, two sample filters with cut‐off frequency of 0.5/0.3 GHz are fabricated using a three‐/five‐layer PCB process, which generate seventh‐order low‐pass filtering responses with good selectivity. The experimental results agree well with the predictions.

This paper presents an effective design method to integrate bandpass filtering response into an aperture-fed dual-polarized magneto-electric dipole antenna (ME-dipole). The antenna is composed of a traditional ME-dipole radiator and a modified aperture-coupled feeding structure. In one aspect, highpass filtering radiation response is realized by approximating the antenna radiator as a highpass filter network. In another aspect, by developing an improved aperture-coupled feeding structure with lowpass filter characteristic, the antenna obtains lowpass filtering radiation response. As a result, bandpass filtering radiation response is achieved. Since no intricate filter resonators are used, the in-band antenna gains are not degraded. The highpass/ lowpass filter networks are studied and specific radiation nulls generated by the two networks are analyzed. For demonstration, a single-polarized model is presented first and its working mechanism is studied in detail. It realizes a 78.6% impedance bandwidth, flat in-band gains of 7.5 -7.8 dBi, and more than 22 dB out-of-band radiation suppression level. Then, based on the same methodology, a dual-polarized antenna model is developed with 69.3 % operating bandwidth, 7.1 -9.3 dBi measured in-band gains and integrated bandpass filtering radiation response.

Most MMC distributed control systems require the central controller to collect capacitor voltages measured by local controllers to perform the phase average capacitor voltage control. Transmitting considerable capacitor voltages can greatly increase the communication burden in an MMC with numerous submodules. In this letter, we aim to significantly reduce the communication burden with adequate data exchange to maintain the control performance by proposing two round-robin transmission modes with voltage-ripple-filtering capability. The two transmission modes are elaborately designed to filter out specific harmonics for the removal of the low-pass filter in the voltage control loop. The feasibility of the capacitor voltage transmission modes is confirmed by the simulation and experimental results.

In the electrical power and energy (EPE) area, the traditional concept in designing the synchronization system of power converters is using the phase-locked loop (PLL) concept. An alternative way is using the frequency-locked loop (FLL) concept, which is also known as the adaptive notch filter, adaptive noise cancelation technique, gradient descent estimator, adaptive observer, D-estimation method, and transformation angle detector, among others names. Along with the increased popularity and application of FLLs in EPE systems, the misconception about this design concept is growing. To be more exact, most EPE research communities introduce FLLs as synchronization systems of different properties compared to PLLs. This article aims to explain the main reasons behind this misconception and contribute to dispelling it.

In this article, a compact microstrip lowpass filter (LPF) using elliptical shaped resonators with ultra-wide stopband is rendered. In this respect, LC equal structures of the elliptical shaped resonators are calculated based on the formula of circumference. In addition, to calculate transmission zeros of the presented elliptical shaped resonator, the LC equal structure and its output to input ratio are employed. The proposed LPF has a −3 dB cut-off frequency at 1.50 GHz and the stopband bandwidth of the designed filter is about 13fc, which refers to its ultra-wide stopband. The occupied circuit size of the presented filter is 0.151λ g × 0.044λ g (λ g is the guided wavelength at 1.50 GHz). The designed filter is fabricated on RT/Duroid 5880 substrate. The results of the fabricated and designed filter have clearly demonstrated that not only has the proposed LPF shown a suitable agreement between measured and simulated S-parameters, but also an appropriate stopband bandwidth.

In this brief, a new miniaturized ultra-wideband (UWB) bandpass filter (BPF) with ultra-wide stopband (UWS) using $\pi $ -type unit with inductive loading on integrated passive device (IPD) is proposed. the $\pi $ -type with non-periodic response is equivalent to the coupled line with open-ends diagonally for the first time. The proposed compact lumped BPF based on three $\pi $ -type units is not only easy to design UWB response without strong coupling, but also has the advantage of the UWS due to the non-periodic phase of the unit. Besides, the high frequency selectivity can be obtained for two transmission zeros near the passband. In final, a prototype with 3-dB fractional bandwidth of 111% is designed and fabricated at 4 GHz ( ${f} _{0}$ ). The upper-stopband attenuation higher than 24 dB is extended to more than 45 GHz ( $> 11.25{f} _{0}$ ). It occupies only 0.008 $\lambda _{0} \times 0.032\,\,\lambda _{0}$ , where $\lambda _{0}$ is the free-space wavelength at ${f} _{0}$ .

In order to improve the dynamic performance of the sensorless permanent magnet synchronous motor drive system, the modified pulsating high frequency voltage injection method is proposed. Firstly, the second order generalized integrator can be used to extract the high frequency voltage signal instead of band-pass filters. The specific frequency harmonic elimination unit is applied to obtain the rotor position error signal to avoid using the low-pass filter. Therefore, the system dynamic performance can be improved. In addition, the system parameter is easier to adjust than traditional methods with band-pass filters and low-pass filters. Finally, the simulation model and experimental platform are built to verify the effectiveness of the proposed method. The simulation and experimental results present that the dynamic performance of motor drive system can be improved.

The design process of analog circuits is a challenging issue due to the nonidealities. Thus, analog IC design must be automated to shorten the design time and must be optimized to improve the important performance criteria, such as power dissipation, estimated chip occupation area, etc. In this work, a genetic algorithm (GA)-based approach is proposed for the low-pass filter design of IEEE 802.11n Wireless LAN. The performance criteria of OTA and CCII are modeled with an artificial neural network and transistor sizes of those blocks are determined with GA to improve the performance and to satisfy the constraints. The advantage of the proposed methodology is to eliminate infeasible solutions before starting circuit design by modeling the design constraints according to the transistor sizes allowed by production technology. The performance of the proposed method is tested with 0.18- $\mu \text{m}$ technology in CADENCE environment.

Large time delay is one of the inherent features in modular multilevel converter (MMC) based high voltage direct current (HVDC) system. It is the main factor leading to the unfavorable ‘negative resistance and inductance’ characteristics of MMC impedance. Researches indicate that such unfavorable characteristics interacting with the capacitive characteristics of AC system is the reason causing high frequency resonances (HFRs) in YuE HVDC project. As the current controller is one of the main factors to shape the MMC impedance, a compensation control to imitate the paralleled impedance at point of common coupling (PCC) is proposed. Therefore, the structure and parameter design of the compensation controller are the core to realize HFRs suppression. There are two potential risky frequency ranges of HFRs (around 700Hz and 1.8 kHz) in the studied AC system within 2.0 kHz. The core concept of HFRs suppression is to make the phase angle of MMC impedance smaller than 90° in the two risky frequency ranges according to impedance stability theory. Hence, the parameters designing are to coordinate the phase angle of MMC impedance in the two risky frequency ranges. In this paper, three types of compensation controller are studied to suppress HFRs, namely, first-order low pass filter (LPF), second-order LPF, and third-order band pass filter. The results of parameters design show that the first-order LPF cannot suppress the both HFRs simultaneously. The second-order LPF can suppress the both HFRs. However, it will bring DC component into the current control loop. Therefore, a high pass filter is added to form the recommended third-order controller. All the parameter ranges of compensation controller are derived using analytical expressions. Finally, the correctness of the parameters design is proofed by the time-domain simulations.

In this letter, a combined approach based on circuit equivalent and field analysis is employed to design a waveguide low-pass filter. According to the field analysis and out-of-band transmission poles responses, the transmission pole spacing distribution method is proposed to obtain a wide stopband. The simulation indicates that this method can provide a well-performed harmonic suppression. Different from the large-scale parameter optimization method for the wide stopband, this technique has the advantage of consuming relatively small computation resources. Finally, the X-band waveguide low-pass filter is fabricated and tested. Measurements show that the stopband suppression can exceed the fourth-order harmonic of the fundamental mode with more than 56-dB suppression levels.

Due to the increasing development of renewables in power systems, the requirements for phasor measurement units (PMUs) become higher. A PMU calibrator is an important tool to test and calibrate PMUs to ensure their measurement performance. This device can provide accurate reference values for error analysis of PMUs. In this paper, a phasor algorithm with low computational complexity and high accuracy is proposed for the PMU calibrator. This method reduces the processor requirements and development cost of the calibrator, thereby facilitating its popularization. At first, an enhanced discrete Fourier transform (DFT) method is put forward: 1) the frequency response of the windowed DFT method is analyzed to reveal its large measurement errors under dynamic conditions; 2) the parameter requirements of the DFT window that is regarded as a lowpass filter are analyzed, and thus a lowpass filter with better filtering performance is designed as the window coefficients to improve the estimation accuracy. Then, based on the enhanced DFT algorithm, a calibrator algorithm framework consisting of two-stage filters and signal recognition module is established. This algorithm can consider the anti-interference ability and dynamic measurement accuracy at a low reporting rate. Simulation and experimental test results show that the proposed calibrator algorithm provides high-accuracy measurements of the static and dynamic signals with low computational complexity.

In this paper, the application of microstrip technology is investigated in low-pass filters. A cascade microstrip low-pass filter with a sharp frequency response and a good cut-off bandwidth is presented using a modified radial resonator. The advantages of this proposed filter include minor losses in the transit band as well as the desired return. This filter design shows consistency when compared with the results of simulation and model performance. A comparison between the parameter values of this filter and previous structures indicates that it is desirable. The proposed filter can be used in modern communication systems such as aircraft distance measurement equipment (DME) antenna.

This article presents a new algorithm of finite control set model predictive control (FCS-MPC) with floating virtual voltage vectors (VVs) applied to grid-connected voltage source converter. The new solution improves the conventional FCS-MPC and FCS-MPC with virtual VVs, assuring a fixed switching frequency. In comparison with FCS-MPC using virtual VVs, the proposed algorithm ensures a shorter distance between floating virtual VVs and actual voltage vector achieves lower THDi and ripples of the grid current for the same sampling time. The proposed control method has been experimentally validated using a 5-kW prototype. The algorithm was examined and compared in steady and transient states as well as under grid voltage disturbances, such as higher harmonics, dips, and unbalance. The simulation results and experimental measurements confirm that the developed control technique shows a high quality of the grid current (low THDi value), high dynamic performance, and immunity in case of weak grid conditions.

This article proposes an improved virtual inertia control strategy, which reduces the lag effect of a low-pass filter in conventional control and increases the speed of virtual inertia control in wind turbines. The grid frequency obtained by phase locked loop (PLL) must pass through a low- pass filter with a small cutoff frequency under distorted grid voltage. The delay caused by the low- pass filter conflicts with the goal of fast support required for virtual inertia control. This article analyzes the influence of filter on system stability and response speed in frequency detection. First, the advantages and disadvantages of differential feed-forward (DFF) control are proposed and analyzed. Then, a lag-lead-based phase compensator (LLPC) scheme is proposed to provide better system stability and rapidity. Finally, the effectiveness of the proposed control strategy is validated on an 11-kW doubly fed induction generator (DFIG) platform.

To maintain the compactness of future 5G smartphones, integration of sub-6 GHz and millimeter-wave (mm-wave) bands is a challenging task due to the large frequency ratio. We, therefore, propose a single-fed triple-band antenna with a large frequency ratio. The proposed antenna is composed of a microstrip patch radiator with an inverted U-shaped slot for dual-band operation in the mm-wave frequencies (28 and 38 GHz). A meandered radiating structure is linked to the microstrip patch radiator through a compact microstrip resonant cell (CMRC) low-pass filter (LPF), which is used for the integration of these structures to be operated at 3.5 GHz. A compact size of 22 mm $\times10$ mm $\times0.508$ mm for the proposed antenna was realized by incorporating the radiator slot, an LPF, the truncated ground, and a meandered line structure. Wide, decoupled −10 dB bandwidths of 12.9%, 5.8%, and 2.4% at 3.5, 28, and 38 GHz, respectively, were realized for the proposed MIMO antenna without utilizing an external decoupling structure. A detailed safety study with respect to specific absorption rates and power densities was analyzed in data, reading, and talking modes. Finally, the measurements were performed in an anechoic chamber, and the measured results were in a good correlation with the simulation results.

Automatic voltage regulator (AVR) is used at each generating station or synchronous generators to maintain voltage supply at steady state or at a constant value otherwise the performance of the generator will be affected. The combination of AVR system with controllers clears fluctuation due to variation in load, speed, temperature, and power factor. This causes deviation in generator’s voltage and damage to power equipment. This work presents performance enhancement of AVR system using Proportional Integral and Derivative (PID) with pre-filter control technique. The enhanced performance was achieved by designing a nonlinear model of a synchronous generator, a PID controller and a low pass filter or pre-filter using MATLAB/Simulink model. The introduction of the proposed PID controller with LPF at load variation of 20 seconds, reduces the rise time and the peak time to 5.2975 seconds and 12.31 seconds respectively. This increases the overshoot and the settling time to 4.28 seconds and 17.60 seconds. However, the developed scheme provides a stable time response performance for various desired generator voltages considered. The performance of the proposed scheme was compared with conventional PID controlled AVR system without LPF. The proposed scheme provides more stability as indicated by the percentage overshoot, which is 4.5788% (for PID) and 4.2765% (for PID with prefilter). This has contributed to knowledge an AVR control system with better performance in terms of rise time, peak time, overshoot and settling time for stabilized generator output voltage.

This paper proposes a nonlinear flux linkage observer for the PMSM speed controls without motion sensors, introducing the deviation among the real stator flux linkage and an estimated stator flux linkage to suppress feedback and integral flux drift. In the position detection of an interior PMSM without a speed sensor, the traditional back EMF integration method uses a pure integrator, or LPF, to estimate the stator flux. Its inherent defects inevitably lead to inaccurate flux estimation, which directly affects the estimation of the motor mover position, resulting in the decline in motor control operation and the distortion of phase current. This paper uses an improved integrator with adaptive compensation. The projected value of the stator flux linkage has been derived from the estimated value of the rotor permanent magnetic flux linkage position angle and the algebraic model (m-model) of the stator flux linkage, along with a synchronous coordinate system. The IPMSM stator coil flux linkage obtained from the stator coil current and integral voltage models in the static coordinate system is compared to form a feedback closed-loop to suppress the integral drift, and using the cross-product approach of the actual and estimated flux linkage yields the projected value of the IPMSM rotor speed and position through a PLL. Compared with the existing motion-sensorless observers, the methodology proposed in this article is simple and exhibits better dynamic and static estimation performance. Extensive and comprehensive MATLAB computer simulation and experimental findings validate the proposed motion-sensorless control mechanism.

A microstrip planar lowpass filter with ultra-wide stopband up to 40 GHz is presented. The filter is designed based on four types of hexagonal-shaped resonators, producing multiple transmission zeroes and extending the stopband. The high-impedance transmission line is folded to make the circuit more compact and form the coupling gaps between the adjacent resonators. A pair of folded open stubs are added to enhance the cut-off rate. As a result, an ultra-wide stopband with 23rd-harmonic suppression has been attained. A demonstration filter has been designed and fabricated with 3 dB cut-off frequency of 1.70 GHz. The measured results show that the relative stop bandwidth of the low-pass filter (LPF) is 182% with suppression level of 25 dB, covering 1.85–40 GHz. The functional area size of the filter is 21.50 × 21.70 mm, which corresponds to 0.198λ g × 0.200λ g (λ g is the guided wavelength at 3 dB cut-off frequency).

Based on the hybrid microstrip and substrate-integrated waveguide (SIW) technologies, a compact filter with wide-stopband characteristics is presented in this letter. Two microstrip-based uniform impedance resonators (UIRs) are etched between two SIW cavities, which not only resonate to generate transmission poles, but also constitute coupling-null structures to prevent the propagation of TE102 mode. In addition, the staggered higher mode frequencies of the UIRs and SIW cavities also contribute to harmonics rejection of the two resonant structures. The suppression method of higher order modes is carefully illustrated. For validation, a prototype operated at 10 GHz is designed, fabricated, and measured. The experimental results show good agreement with simulation. Besides suppressing the TE102 and TE201 modes, the proposed filter also has the capability to suppress other harmonics, presenting an ultrawide stopband compared with the conventional SIW filters.

The increasing number of nonlinear loads and the integration of renewable energy sources into the grid make the conventional SRF-PLL less accurate for estimating the phase and frequency of the grid voltage. A variety of enhanced filtering-based PLLs have been reported in the literature to solve this issue. However, these techniques are computationally more complex. For this reason, a method has been proposed to improve the performance of low pass filter (LPF)-based SRF-PLL, which is easy to implement and is computationally less expensive. In this paper, two in-loop second-order notch filters have been used with an LPF to nullify the effect of dominant lower order harmonics. The dynamic performance of the proposed technique is improved by implementing a PID type loop filter. The proposed scheme is compared with the other methods, like MRF-PLL, conventional and LPF-based SRF-PLL. The response of the proposed PLL is found to be encouraging under different grid disturbances. The efficacy of the proposed PLL has been verified by implementing the current controller to control the active and reactive grid current for the grid side converter in the hardware setup.

Water vapor temperatures in a heating device were measured by ultra-low sampled and high-precision tunable diode laser spectroscopy (TDLAS) Bichromatic distributed feedback (DFB) lasers were used as light sources. Sampled data at an ultra-low rate was collected after laser passing through a low-pass filter and served as the inputs of an artificial neural network. Classical direct absorption spectroscopy using the line-shape fitting method provided the training dataset, i.e., the integrated absorbances. The proposed method required an ultra-low sampling rate, i.e., only 1/50 of the classical method, but its calculation speed was nearly 14,000 times faster. Also, the proposed method yielded satisfying estimates at temperatures uncovered by the training dataset and was insensitive to random noises.

This brief presents a highly linear and high-speed operational amplifier that consists of a double-recycling folded cascode input stage and an adaptive biasing with a flipped voltage follower to boost slew-rate and unity-gain frequency. In addition, frequency compensation is performed by an input cross-coupled phase-lead passive compensation scheme and hybrid Miller-cascode compensation. A 56 MHz −3 dB bandwidth fifth-order programmable gain continuous-time active low pass filter is fabricated in 180 nm CMOS to validate the proposed scheme. The filter achieves 30.5 dBm of third-order interception point at 38 MHz and occupies 0.215 mm2. The filter consumes 14.7 mW with 1.8 V supply and has 0.2 dB in-band ripple.

This article presents a digital-intensive transmitter (TX) architecture for ultralow-power (ULP) wireless communication telemetry applications. A Type-I correction loop is proposed to adjust the frequency of the voltage-controlled oscillator (VCO) and enable the use of harmonically injection-locked (IL) technique without significant spurious tones. Two TXs implementations with different loop filters in the Type-I phase-locked loop (PLL) are demonstrated to suppress the voltage ripple at the VCO input. The proposed implementation not only minimizes the spurs from the correction loop but also overcomes the performance tradeoff between spur suppression, phase margin, and maximum achievable bandwidth. Prototyped in the standard 180-nm CMOS process, the two proposed TXs achieve an energy efficiency of 66.97 and 12.5 pJ/bit, respectively, and occupy an active silicon area of 0.0413 and 0.0435 mm2, respectively, while delivering the same output power of −14 dBm with >60-dB in-band spur suppression.

In this brief, a novel reconfigurable bandpass filter with adjustable center frequency and wide bandwidth reconfiguration is presented. The proposed bandpass filter is formed by cascading tunable high-pass (HP) and low-pass (LP) filter sections directly. Both the operating frequency and bandwidth of the reconfigurable bandpass filter can be reconfigured independently by tuning the frequencies of the band edges, which are controlled by the cut-off frequency of the HP and LP filter sections. Finally, the proposed filter is designed, fabricated and measured for validation purposes. The measured results demonstrate that the bandwidth can be tuned from 180 MHz to 1390 MHz at the fixed center frequency with tuning ratio up to 7.8:1. Center-frequency agility is also verified with different constant absolute bandwidth of 400 MHz, 600 MHz, and 800 MHz The measured results show that proposed filter possesses the advantages of simple implementation, wide bandwidth tuning range, wide frequency tuning range, and compact size.

This article proposes an average periodic delay-based repetitive controller for power factor correction (PFC) converters undergoing grid frequency variations. When the grid frequency is changed, a conventional repetitive controller requires an interpolation method or additional memory to achieve frequency adaptability. Furthermore, frequency adaptability can also be realized using a variable sampling frequency; however, this requires additional computation effort and a multirate digital control system. In this article, with a fixed sampling frequency and memory length, the proposed repetitive controller, which generates the average periodic delay unit, maintains its harmonic compensation performance under grid frequency variations. In the proposed method, the control variables are updated depending on the phase of the grid voltage to reflect the grid frequency deviations in the average period delay unit. Because no complicated software modification is necessary, the proposed scheme can be easily plugged in the existing control algorithm. The theoretical analysis and stability issues of the proposed scheme have been discussed in detail to ensure stable operation and disturbance rejection. Both the simulations and the experiments on a 1.5-kW PFC converter have been carried out to verify the effectiveness of the proposed repetitive control.

Plane wave (PW) transmission (TX) can be profitably used to improve the performance of color flow mapping (CFM) systems by increasing the autocorrelation ensemble length (EL) and/or the frame rate (FR). Although high-end scanners tend to include imaging schemes using PW TX and parallel receive beams, high frame rate (HFR) CFM has been so far experimentally implemented mostly through research platforms that transmit PWs and beamform/process the received channel data off-line. In this article, full real-time implementation of PW CFM with continuous-time clutter filtering and extended FR/EL is reported. The field-programmable gate arrays (FPGAs) and digital signal processors (DSPs) onboard the ULA-OP 256 research scanner were programmed to perform high-speed parallel beamforming and autocorrelation-based CFM processing, respectively. Different strategies were tested, in which the TX of PWs for CFM is either continuous or interleaved with the TX of packets of B-mode pulses. A fourth-order Chebyshev continuous-time high-pass filter with programmable cutoff frequency was implemented and its clutter rejection performance was positively compared with that obtained when operating on packet data. CFM FRs up to 575 were obtained. The possibility of programming the autocorrelation EL up to 64 permitted to detect flow with high sensitivity and accuracy (average relative errors down to 0.4% ± 8.4%). In vivo HFR movies are presented, showing the dynamics of flow in the common carotid artery, which highlight the presence of secondary flow components.

High frequency (HF) transmitter whose operating frequency range is about four octaves is always faced with the problems of harmonics because of the nonlinearity of the power amplifier (PA). The conventional analog harmonic cancellation scheme uses lossy and bulky filter banks. The digital harmonic cancellation scheme requires a high sampling rate. In this brief, a hybrid harmonic cancellation digital predistortion (HHC-DPD) technique is proposed to suppress the interfering harmonics by adding a low-pass filter between the PA and the directional coupler. The proposed HHC-DPD scheme can greatly lower the sampling rate, in turn, decrease the digital power consumption and resource occupation. Further, a feedback loop compensation (FLC) method is proposed to cancel the time misalignment between the harmonics and the fundamental caused by the chromatic dispersion in the feedback loop. With the FLC method, the non-convergence issue in iterations can be avoided. Experimental results on an HF PA with carrier frequency located at 8 MHz validate that the proposed HHC-DPD scheme with the FLC outperforms current harmonic cancellation approaches. The sampling rate was reduced from 300 MHz to 100 MHz. Both the harmonics and the adjacent channel power ratio (ACPR) were cancelled for being below −50 dBc after the HHC-DPD.

$\text{N}\times \text{N}$ filter operations are frequently used in various image processing algorithms in display driver circuits. The implementation of the $\text{N}\times \text{N}$ filter requires a storage element to temporarily retain N or N-1 lines of display data. The traditional approach for this temporary storage element for $\text{N}\times \text{N}$ image filter is either by using N blocks of memory to store N lines of display data with single-port six-transistor (6T) SRAM bit-cells or by using N-1 blocks of memory to store N-1 lines of display data with dual-port eight-transistor (8T) SRAM bit-cells. In this paper, a pseudo multi-port SRAM circuit is proposed for $\text{N}\times \text{N}$ filter in image processing in a display driver integrated circuit (IC). By using pre-read mechanism and word-line/column selection signal forwarding technique, the proposed approach only stores N-1 lines of display data and can use the small single-port 6T SRAM bit-cells. For a $3\times 3$ filter application, the proposed approach reduces the overall layout area by 50.3% and 30.2% compared to the traditional dual-port 8T and single-port 6T memory implementations, respectively, in an industrial 0.18- $\mu \text{m}$ CMOS technology. Furthermore, the power used to perform a $3\times 3$ filter operation is reduced by 47% and 30.8% with the proposed approach as compared to the traditional dual-port 8T and signal-port 6T memory circuits, respectively, with slight degradation of the access speed.

This work discusses the synthesis and design methodology of high-order and frequency-tunable low-pass active-R filter architectures for multi-standard wireless applications. Active-R filters use the inherent integrator-like behavior of amplifiers to realize their frequency response. The main advantages of this type of filter are high-frequency performance and a low integrated area. Active-R filters only need the Miller capacitor used in internally compensated amplifiers. In this work, amplifiers with configurable unity-gain frequencies enable the continuous tuning of active-R filters. Three different filter architectures realize a fifth-order Butterworth prototype tunable in the 1–50 MHz frequency range. These filters are designed, fabricated, and tested using the TSMC 0.18 ${\mu }\text{m}$ process. Each fifth-order filter consumes power in the range 7.45 mW to 9.38 mW from a 1.8 V supply and has an integrated area ${\leq }~0.33$ mm2. Compared with state-of-the-art active filters, the filters presented in this work have the largest tuning range without linearity degradation and the smallest area per tuning range ratio. Also, the measured filters show a competitive FoM 153.3 dB/J when operating at high frequencies.

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.

This paper describes the design of a compact microstrip microwave diplexer based on bandpass filters and a stepped impedance resonator for 4G applications. The diplexer is composed of two band-pass filters (BPF) that operate at 1.8 and 2.5 GHz. Both bandpass filters for the receiver at 1.705-1.895 GHZ and the transmitter at 2.41-2.6 GHZ have a -3dB fractional bandwidth of 10.5 % and 7.6 % respectively. These BPF, suitable for 4G telecommunications, are examined, evaluated, developed, and simulated, yielding theoretically consistent results. With a dielectric permittivity of 4.4 and a thickness of 1.6 mm, FR-4 is employed as a substrate material. The theoretical design and simulation are used to calculate the size and position of the SIR and feed lines. The diplexer has a low insertion loss and a high isolation, and its efficiency is quantitatively analyzed using the HFSS software. This application allows us to swiftly and simply create electrodynamic structures. A diplexer prototype was developed using a typical method of fabricating PCBs, with a structural area of (47.4020x247.063=11711.28 mm2). The obtained simulation results of the proposed circuit are in good agreement with the measurements.

Optimizing the adaptive circuit of piezoelectric sensors is important in accurately measuring blast waves. This study analyzed the impact of the bandpass cut-off frequencies and quality factor of adaptive circuits on shock wave measurements. We proposed a Multi-objective particle swarm optimization based on weighted Pareto-dominance sort (W-MOPSO) for optimizing the multi-objective function of an adaptive circuit in order to improve precision during shock wave measurements. W-MOPSO obtained a Pareto-optimal solution set through Pareto-dominant sorting of global optimal solutions to the weighted sum of a multi-objective function. The relative mean error in the optimized adaptive circuit mostly ranged between −2% and +2%. Simulations were used to analyze the impact of the optimized adaptive circuit on shock wave measurements. The effectiveness of W-MOPSO was verified through a real-world experiment using a TNT explosive and blast wave gauges. W-MOPSO provided a basis for adapter circuit design and optimization in shock wave measurement.

In this communication, a ±45° dual-polarized antenna for 690–960 MHz base station applications is proposed. The proposed antenna has a crisscross-shaped radiator which is fed by four triangular-shaped couplers. The ±45° dual polarization is achieved by vector synthesis of the currents on the radiator. To further broaden the impedance bandwidth (IBW), a miniaturized lowpass filter is designed and integrated with the baluns of the proposed antenna. With the lowpass filter, a new resonance is introduced and harmonic suppression is also realized. The experimental results which agree with the simulations show that wide harmonic suppression bandwidth which can cover the interference bands (1.69–2.69 GHz and 3.3–3.8 GHz) is obtained. In the operating frequency band (690–960 MHz), a voltage standing-wave ratio (VSWR) of less than 1.5, a polarization isolation (ISO) of more than 35 dB, a half-power beamwidth (HPBW) of 66.8° ± 1.5°, and the gains of 8.3 dBi ± 0.2 dBi are obtained by the proposed antenna.

This paper introduces a novel out-loop compensation scheme with a selective filtering stage for Type-1 Frequency Locked Loop (FLL) to obtain the same features of Type-2 FLL in response to frequency drift. The proposed scheme can eliminate the phase angle error during frequency drift without compromising its benefits of the low order control system. The performance of the proposed Type1-c FLL is evaluated with alternatively employed Delayed Signal Cancellation (DSC), Low Pass Filter (LPF) with selective harmonics filtering and multiple second-order generalized integrator (MSOGI) as a pre-filtering stage under the various grid disturbances. The effects of each filtering scheme on the dynamic response and harmonics mitigation are identified. As each filter has a distinct advantage in response to each grid disturbance, a selective control approach is used to insert the most suitable filter based on the severity of the grid disturbance to achieve the best performance. A comprehensive study is conducted to demonstrate the superior performance of the proposed schemes with both simulation and experimental validation. In addition, the potential application of the proposed Type-1c FLL for enhancing the islanded microgrid operation has been presented and verified.

In many applications, circuits containing lumped-elements are preferred because of their small sizes. But it is not possible to avoid losses caused by the connections between lumped-elements at high frequencies. However, the use of these connections as circuit elements will improve the performance of the circuit. Therefore, it becomes inevitable to use circuits with mixed (lumped and distributed) elements at high frequencies. In this brief, phase shifting properties of high-pass and low-pass mixed-element two-ports is explained. Then these two-ports are used to form the initial design of high-pass and low-pass sections of a phase shifter. Finally, the initial design performance can be improved by means of commercially available computer-aided design (CAD) tools.

A microstrip-based lowpass filter (LPF) containing modified ring structures has been presented. Ring resonators are used to form a sharp transition region. In addition, rectangular- and tapered-shaped suppressing cells are used to create an ultra-wide stopband region. By combining the designed ring resonator and suppressors, an LPF has been designed with −3 dB cut-off frequency at 1.83 GHz. A sharp transition region has been achieved from 1.83 (at −3 dB) to 2.1 GHz (at −60 dB). A stopband region has been concluded from 2 to 21 GHz (with the corresponding attenuation level of at least 20 dB). The measured insertion loss is better than 0.1 dB (equal to a return loss of 18.1 dB) in the passband region. The proposed circuit is fabricated and measured. The measured results have an appropriate adaption with the simulated results.

In this work, the different elements of a rectenna were optimized for the energy harvesting from Wi-Fi at 2.45 GHz, using the particle swarm optimization method with real or hybrid dimensions depending on the element. The antenna was optimized in different steps and for each one the effect on its performance was determined. For the rectifier, several commercial diodes were compared for evaluating the best selection for this application. Additionally, a low pass filter and an impedance matching of L-section were implemented as coupling elements. The antenna from the novel rectenna had a gain equal to 4.42 dBi due to the incorporation of a pixeled metasurface structure in the ground layer, and a maximum conversion efficiency of 73% with the diode SMS-7630. In this sense, the optimized rectenna presented a better performance than others from the literature for RF energy harvesting at 2.45 GHz. Therefore, the proposed rectenna can be a good alternative as a power supply in nodes of wireless sensor networks with the addition of the DC–DC boost converter LTC3105.

Voltage resonance and fluctuation deteriorate the stability of DC microgrids (DC-MGs) and restrict their popularization. Conventional droop control cannot suppress voltage fluctuation and damp oscillations. Therefore, new control methods, namely, droop+filter control and virtual inertia and damping control, are proposed. These methods differ owing to the addition of low pass filter (LPF) and virtual inertia loop. In this study, the stability of these control methods is investigated comprehensively to understand their differences arising from the use of LPF and inertia loop as well as the underlying dynamic stability mechanism. The leading causes of voltage instability in DC-MGs regulated by droop control are first presented. Subsequently, control methods for solving this issue are compared and their simplified small-signal models are constructed. Based on eigenvalue analysis, the DC-MG is equivalent to a third-order system. Different control effects can be acquired by changing the control parameters and the location of the eigenvalues; furthermore, they can be used to understand the dynamic stability. Eigenvalue analysis can provide parameter design guidelines. Finally, the simulation results verify the validity of the theoretical analysis.

For the LCL -type grid-connected inverter, grid voltage full feedforward scheme is an effective method to improve the quality of the injected grid current. However, in the applications where a step-up transformer is adopted and its leakage inductance serves as the grid-side inductor, it is difficult to directly measure the grid voltage. For this case, the capacitor voltage full feedback scheme is proposed in this article to suppress the injected grid current distortion due to the grid voltage harmonics, and the full feedback function includes proportional, derivative, and second-derivative components. It is found that the derivative component counteracts the capacitor current feedback active damping, and both of them can be removed. Thus, the current sensor for sensing the capacitor current is saved. Instead, the LCL filter resonance is damped by the proportional and second-derivative feedback components, and a low-pass filter is added to the second-derivative component for ensuring a positive equivalent resistance within the full controllable frequency range. Experimental results from a 6-kW single-phase grid-connected inverter are provided to verify the effectiveness of the proposed method.