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Dual active bridge converters are widely applied to bidirectional power conversion systems. However, the volume and the losses of the high-frequency transformer are responsible for a considerable share of the total volume and losses of the converter system. Transformer-less capacitor-coupled dual active bridge converters that replace the transformer with series-connected capacitors have been introduced to mitigate this problem. For both the transformer-coupled and capacitor-coupled dual active bridge converters, digital isolators are used to transmit the high-frequency gating signals for the primary or secondary full-bridge circuit. However, the digital isolators bring in the issue of system reliability, manufacturing cost, and propagation delay. In this paper, a phase control using a network node voltage feedback for the capacitor-coupled dual active bridge has been proposed. The proposed method implements the phase-locked-loop on the opposite side phase information directly extracted from the node voltage of the capacitor-coupling network. The proposed method eliminates the digital isolator or any other communication methods for capacitor-coupled dual active bridge control. The proposed method is experimentally verified with a 2.2 kW capacitor-coupled dual active bridge DC-DC converter prototype with a peak efficiency of 98.6%.

Outdoor insulator is one of the important equipment in an electrical power system. The failure of the isolator, especially in the form of flashover, contributes significantly to the total system failure. In order to improve the performance of the outdoor insulator, a number of efforts have been made, such as the use of new materials, surface coatings to improve dielectric strength and improvement of insulator design. Systematic efforts to improve insulator performance require an understanding of insulator behavior. This paper describes how to understand the behavior of an insulator by using an electrical equivalent circuit derived from the leakage current waveform. Using the proposed equivalent circuit, the leakage current wave simulation was carried out for ceramic and silicone rubber insulators under clean fog and salt fog conditions. Information about insulator parameters such as resistant, non-linearity property and arc that can be obtained from simulation are important to improve the performances of the insulators

Vibration isolator is widely used in aerospace, vehicle, ship and other industries, its dynamic stiffness, impedance and other dynamic performance are its core parameters. A large number of test instruments have been developed for dynamic performance test of vibration isolators, but they are usually aimed at low frequency, light load and simple structure of vibration isolators. For vibration isolators with different characteristics, it is usually necessary to carry out specific structural design for their test instruments to avoid resonance and other safety problems during the test. In this paper, the structure design of dynamic performance test instrument for a certain type of high frequency vibration isolator was carried out. Based on the modal analysis of finite element simulation, the beam, column and foundation of the test instrument were optimized. And the variation law of its natural frequency was summarized. The simulation results showed that the optimized test instrument could meet the safety requirements. Its natural frequency was above 1000Hz, which could be used for the next step of production and manufacturing. This study also provided guidance for the structural design of the high frequency dynamic test instrument.

We present the design of a thermal isolator, based on a simple gap in a standard rectangular waveguide with external circular profile. The proposed solution allows to achieve high return loss and low insertion loss by a suitable selection of the of the external radius of the waveguide circular profile, which determines the waveguide wall thickness. High robustness to misalignment is obtained, improving the performance of a recently published work in the same topic.

RF front-end antenna interfaces with the ability to simultaneously transmit and receive (STAR) at the same frequency and at the same time are highly desirable in a plethora of wireless communication and electronic warfare (EW) systems. Whereas full-duplex radios enhance spectral efficiency by doubling the channel throughput, EW applications benefit from the ability to listen while jamming. The effectiveness of STAR systems is highly-dependent on the levels of isolation (> 80 dB is typically required) that can be achieved between the transmit and the receive module of the antenna interface. Monostatic and bi-static STAR antennas [1] followed by multi-stage circulator/isolator networks and self-interference cancellers may potentially meet the desired 80-140 dB levels of isolation, however their size is prohibitively large for small/medium-size base stations. Alternative miniaturization techniques such as self-biased materials [2] or transistor-based implementations [3] are nowadays being explored for these systems. However, all of these approaches are at their infancy and suffer from poor isolation (~20-30 dB) and high in-band loss (> 5 dB). Taking into consideration the aforementioned limitations, this paper provides an overview of our research on RF front-end modules with collocated RF signal processing actions with the purpose of miniaturizing the overall size, loss and power consumption of an RF front-end. In particular, we address different techniques that are used for size compactness and loss reduction through the realization of isolators/circulators with embedded bandpass filter (BPF) capabilities, as shown in Fig. 1 . The main approaches that will be presented include: i) ferrite-based co-designed BPF and circulators [4] , ii) transistor-based nonreciprocal BPF and isolators [5] , and iii) fully-integrated non-reciprocal BPFs and isolators/circulators [6] . A discussion of the trade-offs for each implementation (i.e., size, complexity, performance, scalability, etc.) along with experimental validation of the proposed topologies will be presented at the conference.

An isolator with high static low dynamic stiffness (HSLDS) is an efficient instrument to expand its range of low frequency. This paper explains what the nonlinear vibration isolator with the HSLDS and reports several HSLDS passive vibration isolators(PVIs), such as vertical mechanical spring combining with Euler bar in series horizontal mechanical spring, vertical pneumatic isolator in parallel with maglev isolator, maglev isolator connected with rubber ligaments, and so on. The harmonic balance method is efficient to analyze the transmissibility of the HSLDS isolator. In this paper, the stability of the HSLDS is discussed. The increasing damping shrinks the unstable region. We propose a method for the readers how to construct, design, and research the vibration isolation performance(VIP) of an HSLDS isolator.

Optical transmission non-reciprocity requires a propagation medium that simultaneously offers time and spatial symmetry breaking [1] . In the quest for integrated optical isolator, different physical mechanisms have been proposed, explored and improved to attain time-reversal breaking such as magneto-optics (MO) [2] , optical nonlinear methods [3] , dynamic modulation [4] or optomechanical interactions [5] . Transverse Magneto-Optical Kerr Effect (TMOKE) has appeared as the most relevant non-reciprocal effect to be used in guided configurations, enabling either non-reciprocal intensity transmission [6] or non-reciprocal phase shift in interferometric or resonant structures [2] . Very recently, another TMOKE based mechanism has been explored by the authors, which induces asymmetrisation of guided modes in MO slot waveguides [7] , [8] : the combination of magneto-plasmonic and coupled modes in this mechanism, is called "magneto-biplasmonic" effect. Due to this phenomena, the light propagates mainly on one side of the slot waveguide in forward direction, and along the other side in backward direction ( Fig. 1 ). By inserting absorbers on only one side, isolation function is obtained. The slot waveguide is a gold-BIG-gold structure, where BIG is a MO garnet. Since the asymmetrisation operates on the long-range (LR) or short-range (SR) surface plasmon polariton (SPP) coupled modes, the isolating structure must be interfaced with a single TE mode waveguide to realize full integration and selectively excite only the LRSPP mode ( Fig. 2 ).

A new class of an RF front-end component that exhibits the co-designed function of a dual-band bandpass filter and an RF isolator is presented. The proposed non-reciprocal dual-band bandpass filter (NDBPF) is based on two multiresonant cells and one non-reciprocal resonant stage. By cascading them in series, a dual-band transfer function-shaped by four poles (two for each passband) and six transmission zeros-is created in the forward direction and full RF signal cancellation is obtained in the reverse one. For proof-of-concept demonstration purposes, a NDBPF prototype was designed at X-band and manufactured with a commercially-available MMIC GaAs process. It exhibited two bands with the following RF measured characteristics: center frequencies: 8.33 GHz and 10.17 GHz, 3-dB fractional bandwidth: 6.4% and 3.6%, maximum gain: 6.38 dB and 0.3 dB, and isolation >36.7 dB and 19.5 dB at respectively the lower and upper band.

We propose a lightweight compact highly efficient non-magnetic time-modulated isolator based on signal interference in phase-shifted time-modulated loops. The proposed isolator exhibits large isolation level and weak undesired time harmonics. In contrast to the recently proposed space-time-modulated isolators which are governed by progressive unidirectional coupling between the incident wave and the modulation, our isolator is not governed by such a progressive process and therefore possesses a very low-profile. An experimental demonstration of the proposed time-modulated isolator at microwave frequencies is provided, showing strong unidirectional wave transmission through the isolator with more than 27 dB contrast between the forward and backward waves.

Terahertz (THz) non-reciprocal components such as circulators, isolators, filters, and gyrators are anticipated to play vital roles in THz system. However, to the best of our knowledge, silicon-based THz non-reciprocal components have not been reported. This paper presents the first silicon-based THz magnetic-free non-reciprocal isolator in SiGe BiCMOS process $(f_{T}/fmax=\mathrm{300}/\mathrm{450}\ \text{GHz})$ , covering 305–325 GHz. Peak-control gain-boosting technique is utilized to push the operating frequency of the magnetless non-reciprocal metamaterials (MNMs) to THz spectrum. By cascading three MNMs operating at different frequencies, a wideband non-reciprocal isolator is achieved. It exhibits 3.6 dB loss (with pad) and 15.3 dB isolation while consuming 3.52 mW (1.17 mW/unit) from 0.88-V supply.

Fast switching transitions of the SiC MOSFET power semiconductor devices, can cause abundance of issues due to injected common-mode (CM) noise current through gate driver, possibly preventing converter successful operation. Therefore, this paper presents a detailed methodology of simulation and new measurement method of CM noise current on a gate driver. For simulation, detailed consideration of circuit parasitics (inductances, resistances and capacitances) is included and analyzed. Considering measurement, small high-precision chip resistors are utilized to measure the CM noise current. The results achieved by simulation and measurement are in agreement. This method is applied to design a novel gate driver for 1.7 kV SiC MOSFET half-bridge module having "on-board communication" between top and bottom devices. By comparing different options, simple communication by a digital isolator is deemed the best. As this paper illustrates, proposed method of evaluating and measuring the noise is useful to design new gate drivers.

Measuring absolute gravity acceleration from a ship or aircraft is essential in gravimetry. Unlike conventional ground measurement, absolute marine gravimeters are disturbed in six degrees-of-freedom. Among the six degrees-of-freedom, the translation along the Z-axis and the rotations around the X-axis and Y-axis have the main influences on the measured gravity acceleration. Thus a six-degrees-of-freedom vibration isolator with output constraints is developed in this paper. The structure of the vibration isolator is based on the Stewart platform, and the state-space dynamic model with disturbances is established via the Newton-Euler method. A constrained model predictive controller is then designed for the vibration isolator. The controller handles the constraints of the three dominant degrees-of-freedom explicitly. Finally, the simulation is performed to validate the presented isolator. The external disturbances in six degrees-of-freedom are well attenuated, besides the motion of the three dominant degrees-of-freedom is within the designed constraints. Thus, the precision of the absolute marine gravimeter can be satisfied with this six-degrees-of-freedom vibration isolator.

Because the optical payloads in the spacecraft is generally large, it is necessary to design a large-size Stewart platform for the attenuation of micro-vibration. However, it is difficult to carry out the ground experiment of integral control system without the influence of gravity. Therefore, the vibration control performance research of the single active-passive rod as the core component of Stewart platform, has become the primary and feasible tasks. Firstly, the active-passive rod structure is introduced, and its equivalent dynamic model, including piezoelectric exciter, damper, force sensor, active piezoelectric rod and concentrated load, is derived. Then the application methods of ideal force feedback control algorithm and PD control algorithm are given. Finally, the simulation and experimental study of the control system are completed respectively. The results show that the designed active-passive rod has good low-frequency micro-vibration isolation performance, which provides a basic reference for the subsequent active-passive vibration isolation platform research.

We present four examples of metasurfaces nonreciprocal wavefront manipulations using transistor-loaded resonators: nonreciprocal phase-gradients, nonreciprocal waveplates, a nongyrotropic reflective isolator and a gyrotropic reflective isolator.

Passive millimeter components play an important role in all future communication systems. Among the most significant devices are isolators, which are considered as essential protection elements in high power applications. It prevents the RF signal from reflecting to the source, and provide the required protection. It depends mainly on the non-reciprocity to allow the power flow in one direction only. In this work, we have designed an isolator based on the non-reciprocal mode conversion in the mm-wave band. This isolator is realized using rectangular waveguide loaded with horizontal ferrite slab in one path. As a result the wave maintain dominant mode operation in one direction, while the mode is converted to the higher order one on the other direction. Afterwards, the second order mode is collected and terminated to a load to protect the source and realize isolation. The proposed design is modeled and simulated to show the objective performance in the operating bandwidth 27-32 GHz. The proposed waveguide isolator achieved an insertion loss below 0.5 dB with an isolation level above 15 dB over the operating bandwidth.

Bulk acoustic wave (BAW) thin-film lithium niobate (LN)-silicon (Si) delay lines are presented that offer more than 30 dB of non-reciprocal transmission ratio enabled by the acoustoelectric (AE) effect. In this scheme, the interaction of drifting electrons and acoustic phonons turns the microacoustic waveguide into a strong isolator. By tailoring a heterostructure stack of LN and Si, up to ~22 dB of AE gain (160 μW) is measured at only ~4 mW of DC bias power, yielding an unprecedented high power-added efficiency of 4%. This is realized within a 4.3% fractional bandwidth and a spurious-free span of 400 MHz centered around 700 MHz. Furthermore, thermal analysis and measurement results support device operation under large and continuous bias, mostly due to the high thermal conductivity of Si. The increasing demand for nonreciprocal RF components such as isolators and circulators in rapidly growing areas, namely, 5G communications and quantum computing could render this platform a potentially suitable candidate for further investigations.

This paper discusses the RF design and characterization of an X-band MMIC isolator. It is based on a directional coupler and a non-reciprocal RF signal path that comprises a gain stage and two transmission line elements for phase control. In this manner, enhanced power transmission is obtained in the forward direction and isolation in the reverse one. The operating principles and RF design trade-offs (isolation, gain, matching) of the isolator are presented through circuit-based analysis. For proof-of-concept demonstration purposes, a prototype was designed at X-band and manufactured with a commercial MMIC GaAs process. Its RF measured performance is summarized as follows: center frequency: 9.4 GHz, maximum gain = 9.3 dB, maximum isolation = 27.7 dB, and 3 dB passband bandwidth with > 23 dB of isolation= 1.61 GHz.

We present a design approach for a self-biased Ka-band isolator. A pre-sintered barium hexaferrite is integrated in a RO4003C laminate. In combination with a microstrip design this yields a compact and cost-effective component. The operating principle of the isolator and a concrete design example are presented. The experimental work confirms the theoretical expectations and reveals the optimization potential.

In the field of industrial measurement and control, analog signals, such as pressure, temperature, valve opening, and flow, are widely transmitted in the form of current signals. Analog signals often need to participate in a variety of control or display process loops after being converted into current signals. To ensure the stable and reliable operation of the industrial process control system, the input current signal needs to be converted and output by an isolator. However, the isolator has conversion error and the conversion errors of different channels of the isolator are generally different, so the current values of different output channels of the isolator are generally inconsistent. With the long-term operation of the industrial process control system, this numerical difference may increase gradually be unbearable. To solve this problem, this paper proposes a design scheme of the current isolator based on FPGA. In this design scheme, FPGA collects the current value of each output channel, runs the automation correction algorithm, adjusts the value of the output current dynamically, and finally makes the current value of each output channel remain consistent. The hardware implement and test of the current isolator are carried out and the test results show that this isolator implementation scheme is feasible.

Considering both vibrational force and vibrational velocity, the power flow transmission characteristics of an active vibration isolation module are derived from the viewpoint of vibration energy. Then, the expressions of the power flow transmission from the direct disturbance and the foundation disturbance to the load are deduced using the four-pole parameter method. The effects of different isolator parameters and feedback control parameters on the power flow transmission are analyzed and summarized by numerical simulations.

An active vibration isolation equipment for isolating low frequency ground vibration of cold atom interferometry is demonstrated experimentally. This system combines the passive vibration isolator of negative stiffness elements and voice coil motor actuator can be used to counteract the ground vibration force measured by the seismometer. The processor with high integration and fast computation can be applied to the algorithm of active vibration isolation. Passive vibration isolation equipment can handle vibration above 10 Hz With the feedback path closed, the vertical vibration noise is greatly reduced by a factor of 100 from 0.1 to 10Hz With the help of active vibration isolation equipment, cold atom gravimeter can measure gravity precisely.

This paper presents a new robust fault detection and isolation (FDI) strategy for distributed and decentralized systems. Such a system consists of several interconnected subsystems. A novel FDI system architecture is designed for these systems. Each subsystem is assigned to a local fault detector performing a part of the overall fault detection algorithm. Fault isolation is performed in a separate global fault isolator. Consistency-based methods based on state-set observation are used for robust FDI. Moreover, this paper introduces a faster fault isolation. For this, the search-space containing all fault candidates is split. Possible network effects in the communication between the computing units are also considered. A simulation example of a three-tank system is used to illustrate the effectiveness of this FDI strategy.

A hybrid transformer (HT) is implemented by augmenting the traditional low frequency transformer with a partially rated power electronic (PE) module. This paper presents a control methodology that enables the hybrid transformer to perform harmonic isolation in addition to typical load voltage regulation. The operational challenges with the hybrid transformer due to the limited power rating of the power electronic module is addressed while formulating the proposed control approach. An adaptive gain is introduced to ensure that the hybrid transformer operates within the permissible limits, regardless of the grid and load conditions. A dq-frame small-signal analysis is carried out to derive the emulated impedance by the hybrid transformer. The emulated impedance validates the operation of the hybrid transformer as a harmonic isolator, and also gives insight into physical meaning of the adaptive gain. The proposed hybrid transformer system is suitable for power delivery to sensitive clustered harmonic loads, such as data centers. The effectiveness of the proposed system is validated through simulation results.

This contribution focuses on the analytical and finite element modelling of the thermo-mechanical behaviour of a friction-pendulum bearing device for passive seismic isolation. Influences of some crucial factors, such as the magnitude and the rate of change of the sliding velocity, the weight of the superstructure, and the rise in temperature on the force-displacement relationship characterizing the isolator, are studied. Numerical results obtained for a realistic testing protocol (plausible value of the applied normal force and sliding velocity) are presented.

Novel configuration of the Faraday rotation isolator employing longitudinally-magnetized ferrite coupled line (FCL) is realized by connecting two lines with a resistor at the end of the ferrite section. The scattering parameters of this microstrip structure obtained through circuit and normal mode analysis are providing information for practical design of the isolator. The nonreciprocal behavior of the isolator and its dependence on resistor parameters are reported.

With the development of ocean renewable energy, offshore wind power has been widely recognized. More and more wind turbines have been built in the offshore area. However, there would be annoying noise during the operation of the wind turbines. A large part of the vibration and noise of the turbine will radiate directly into seawater through the tower, which is potentially harmful to the marine organisms. Therefore, it is necessary to prevent the vibration energy transmission through the tower with vibration isolation design. For one degree-of-freedom (DOF) vibration isolation system, the stiffness of the isolator has to be lower enough to obtain better effectiveness; however, such type of the isolator has soft support, which affects the stability of mechanical system and is not suitable for large equipment. While, for multi-DOF vibration isolation system, the vibration energy transmission characteristics are quite complicated. Therefore, this paper provides the derivation process of analytical solution of the multi-DOF vibration isolation system, which could provide analytical guidance for researchers to decrease the vibration transmission through ocean engineering structures to the ocean, resulting in less noise radiation to the marine environment.

This study introduces a highly efficient magnet-free isolator based on signal interference in time-modulated loops. The proposed isolator offers strong nonreciprocity. It also possesses a low profile architecture in comparison to other recently proposed space-time-modulated isolators. This is due to the fact that the it is not governed by unidirectional progressive coupling between the input signal and the space-time modulation signal where a long structure is required.