Multiport Circuit Research Articles

An Integrated Multiport Circuit Breaker With Current Flow Controlling Capability for Meshed Multiterminal HVDC Grids

An Integrated Multiport Circuit Breaker With Current Flow Controlling Capability for Meshed Multiterminal HVDC Grids

Super-Wideband Massive MIMO

We present a unified model for connected antenna arrays with a large number of tightly integrated (i.e., coupled) antennas in a compact space within the context of massive multiple-input multiple-output (MIMO) communication. We refer to this system as tightly-coupled massive MIMO. From an information-theoretic perspective, scaling the design of tightly-coupled massive MIMO systems in terms of the number of antennas, the operational bandwidth, and form factor was not addressed in prior art. We investigate this open research problem using a physically consistent modeling approach for far-field (FF) MIMO communication based on multi-port circuit theory. In doing so, we turn mutual coupling (MC) from a foe to a friend of MIMO systems design, thereby challenging a basic percept in antenna systems engineering that promotes MC mitigation/compensation. We show that tight MC widens the operational bandwidth of antenna arrays thereby unleashing a missing MIMO gain that we coin “bandwidth gain”. Furthermore, we derive analytically the asymptotically optimum spacing-to-antenna-size ratio by establishing a condition for tight coupling in the limit of large-size antenna arrays with quasi-continuous apertures. We also optimize the antenna array size while maximizing the achievable rate under fixed transmit power and inter-element spacing. Then, we study the impact of MC on the achievable rate of MIMO systems under line-of-sight (LoS) and Rayleigh fading channels. These results reveal new insights into the design of tightly-coupled massive antenna arrays as opposed to the widely-adopted “disconnected” designs that disregard MC by putting faith in the half-wavelength spacing rule.

External Identification of a Reciprocal Lossy Multiport Circuit under Measurement Uncertainties by Riemannian Gradient Descent

The present paper deals with the external identification of a reciprocal, special passive, 2n-port network under measurement uncertainties. In the present context, the multiport model is represented by an admittance matrix and the condition that the network is ‘reciprocal special passive’ refers to the assumption that the real part of the admittance matrix is symmetric and positive-definite. The key point is to reformulate the identification problem as a matrix optimization program over the matrix manifold S+(2n)×S(2n). The optimization problem requires a least-squares criterion function designed to cope with over-determinacy due to the incoherent data pairs whose cardinality exceeds the problem’s number of degrees of freedom. The present paper also proposes a numerical solution to such an optimization problem based on the Riemannian-gradient steepest descent method. The numerical results show that the proposed method is effective as long as reasonable measurement error levels and problem sizes are being dealt with.

Reducing the Number of Measurements of a Multiport Circuit Using Covering Designs and Turán Systems

A theory of arrangements of measurements for obtaining the scattering matrix of a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$v$ </tex-math></inline-formula> -port circuit using a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$k$ </tex-math></inline-formula> -port vector network analyzer (VNA) is developed based on covering designs and Turán systems, which are two kinds of structures in combinatorial design theory. The results of this letter provide a general strategy for reducing the number of multiport measurements of microwave circuits.

Multi-port admittance model and SISO stability criterion for oscillatory stability analysis of VSC-based AC/DC interconnected renewable systems

The voltage-source converter (VSC) is physically a multi-port circuit consisting ac and dc terminals. The impedance/admittance models (IMs/AMs) of VSC are generally developed considering the frequency-couplings at its ac port, while couplings between ac and dc ports are paid less attention. The ac AM cannot directly reflect oscillatory risks between dc grid and VSC’s dc port, and vice versa. This paper proposes a multi-port admittance modeling-based framework to simplify the above modeling and analysis procedure. First, a VSC is viewed as a three-port circuit modeled by a three-dimensional admittance matrix (3DAM). Both ac and dc port dynamics are incorporated into 3DAM with couplings among ports explicitly expressed by off-diagonal elements. Then, the dc and ac grids are easily modeled into 3DAM by sequentially terminating the VSC’s three ports with grid impedances. In doing so, the three-port circuit is reduced into a one-port circuit. The principle and steps to transform the 3DAM to a single-input–single-output (SISO) equivalent form are introduced. The resulting SISO model preserves all coupling information in 3DAM and facilitates a more intuitive stability analysis procedure, where a single Nyquist curve suffices. Finally, the 3DAM and SISO model are applied to identify the dominant factors of oscillatory instability. Time-domain simulations validate the effectiveness of the proposed modeling and analysis methods.Index Terms: Admittance matrix, circuit theory, stability criterion, transfer function.

A multi‐port hybrid circuit breaker integrated with power flow control ability

Power flow controllers and DC circuit breakers are compulsory components in a multi-terminal DC grid with overhead lines. They are both composed of similar power electronic devices and thus can be reasonably combined together to realize cost savings. This paper proposes a multi-port circuit breaker integrated with a multi-port power flow controller (M-PFCHCB). The topology structure, operation principles, control strategy and parameter configuration are illustrated in detail. The main breakers are composed of unidirectional power electronic switches, and the selection branch is based on two diode strings, which can significantly save the investment of the breaker. The proposed M-PFCHCB is able to deal with the fault isolation and the ultra-fast disconnector failure with high performance. Besides, the power flow of multiple lines can be simultaneously regulated by the M-PFCHCB without any external power supply. The internal power balance is achieved by controlling the AC circulating current inside the M-PFCHCB. The simulations conducted on PSCAD in a five-terminal DC grid with eight DC lines verify the feasibility of the proposed M-PFCHCB. The technical and economic analysis performed proves that the proposed M-PFCHCB can achieve the comprehensive functions of fault isolation and power flow control with low construction cost.

Achieving signal power amplification using energetically passive devices

This article discusses some fundamental properties of electronic amplifiers and the associated implications. When defining the passivity of a multi-port circuit in the sense of net power consumption (rather than the ability to amplify signals), devices such as transistors, which are commonly described as “active”, have to be considered passive, which is referred to as “energetically passive” to avoid confusion with other definitions. It is shown that, when using such energetically passive devices to achieve signal power amplification, the amplifier circuit necessarily has to feature a non-linear transfer function. The article discusses how two common concepts (class A and B amplifiers) to achieve signal power amplification with such devices can be fundamentally related to Poynting’s theorem and that both of these concepts allow the realization of at least piecewise linear transfer functions in spite of the necessary non-linearity.

Radio frequency energy harvesting circuits design for the applications of low power electronics

ABSTRACT Radio frequency (RF) energy harvesting, a new demanding area of research during last decade promises to be a source of generating a small amount of electrical power to drive low power consumable electronics devices. This paper presents different RF energy harvesting circuits and techniques to improve the performance of RF energy harvesting technology. A multiport Wilkinson power combiner circuit followed by Villard voltage multiplier circuit has been achieved to combine output power from multiple RF input sources. The performance of a multiport Schottky diode-based energy harvesting circuit is also studied. Experimentally RF power is captured at different frequencies. A Monte Carlo simulation along with worst case analysis has been carried out and results show close proximity to the nominal or actual outcome. A multiport NMOS-based Dickson’s charge pump is also designed compatible with MOS fabrication technology which shows remarkable results.

Millimeter-Wave Dielectric Slab-Based Chip-to-Chip Interconnect Network Allowing for Relaxed Assembly Tolerances

An on-chip, low-loss, and wideband transition to dielectric slab waveguide is proposed in this article, for millimeter-wave interchip communication network applications. The transition design features a three-terminal circuit with one on-chip planar microstrip line and two off-chip dielectric slab-waveguide ports. It presents an add-drop attribute, which can be employed to realize the traditional bus and backbone network topologies. Prototypes presented operate on a thin-film layer imitating the back-end-of-line layers of a chip. Measurements are performed for an end-to-end connection and a hexagonal ring interconnect network at 170 and 100 GHz, respectively. In addition, the proposed transition is shown to enable an equal signal power distribution scheme in a linear array of receivers. To provide much needed relaxation against mechanical tolerances and thermal expansion effects in multiport circuits based on the ceramic dielectric waveguide, a novel low-loss and mechanically flexible connection between two dielectric slab waveguides is presented. The design of this connection, operating from 80 to 100 GHz, is verified by measurements. Technical merits, packaging attributes, and limitations of the proposed single hierarchy interchip interconnect network are discussed.

A Combination of Mixed FETD Method and SPICE to Simulate Nonlinear Multiport Circuits

A combination of the mixed finite-element time-domain method (MFETD) and SPICE solver is proposed in this letter to analyze the circuit response and crosstalk effects in complex microwave circuits with linear/nonlinear, passive/active components. The MFETD method in the EM part is adopted as an unconditionally stable time integration scheme to account for the low-frequency breakdown problem. SPICE is introduced to solve the nonlinear circuit equations in the circuit part by taking into account the coupling between multiport circuits. A microwave circuit based on an AD633 chip and an MCP3221 board is simulated to verify that this hybrid MFETD-SPICE method not only is superior in mesh flexibility to the finite-difference time-domain (FDTD)-based method but also exploits the well-developed open-source software SPICE to solve the nonlinear equations.

Comprehensively Efficient Analysis of Nonlinear Wire Scatterers Considering Lossy Ground and Multi-tone Excitations

In this paper based on intelligent water drops algorithm (IWD), comprehensively nonlinear analysis of nonlinearly loaded wire scatterers are carried out. The analyses involve two stages. First, the problem is modeled as a nonlinear multi-port equivalent circuit and it is then reformulated into an optimization problem which is solved by the IWD. The simulation results are compared with harmonic balance (HB), arithmetic operator method (AOM), approximate methods and experiment. Analysis of the problem under strongly nonlinear loads, presence of lossy ground, multi-port structures, and multi-ton excitations are included to cover all the complex aspects. In one hand, the proposed modeling approach is in excellent agreement with other conventional techniques. On the other hand, the run time is considerably reduced.

Multiport Driving Topology for a Photovoltaic Aircraft Light Transmission System Driven by Switched Reluctance Motors

In order to meet the working requirements of high performance and low cost for a photovoltaic (PV) aircraft driven by switched reluctance motors (SRMs), a multiport driving topology (MDT) is proposed. The converter is composed of an asymmetric half-bridge and a multiport power source circuit. Three driving and two charging modes can be realized through simple control of the switches. The output torque and the efficiency of the system are improved, because the excitation and demagnetization processes are accelerated by increasing the commutation voltage. The battery pack can be self-charged when the system is running, and PV panels can be used to charge the battery pack to reduce energy consumption when the system is stationary. The simulation analysis and the experimental verification on an 8/6 SRM confirm the effectiveness of the MFT proposed in this paper.

Multi-port cavity model and low-level RF systems design for VHF gun

Very high frequency (VHF) photocathode guns have excellent performance and are being increasingly selected as electron sources for high-repetition-rate X-ray free-electron lasers. As a highly loaded quality factor cavity, the VHF gun requires high stability in the amplitude and phase of the cavity field. However, the gun is microwave powered by two solid-state power sources through two separate power couplers. The input difference between the two power couplers will influence the stability of the cavity field. To systematically study this influence and obtain measurement formulae, a multi-port VHF gun LCR circuit model is built and analyzed. During the warm-up condition, the cavity structure will be deformed due to the large-scale change in the cavity temperature. Then, the deformation will result in cavity resonant frequency changes. To prevent the mechanic tuner from suffering damages due to the frequent and long-distance movement for correcting the cavity resonant frequency, a self-excited loop (SEL) control system is considered for changing the loop phase and make the loop frequency follow the resonant frequency. In this study, a steady-state model of the VHF gun cavity is built for obtaining the optimal input coupler coefficient and the stability requirement of the forward voltage. Then, the generator-driven resonator and SEL control system, which combine with the VHF multi-port modeling, are modeled and simulated. The simulated results show that the SEL system can perfectly operate in the process of condition and warm-up.

A New FPGA-Based Real-Time Digital Solver for Power System Simulation

Considering the rational use of field programmable gate array (FPGA) resources, this paper proposes a new FPGA-based real-time digital solver (FRTDS) for power system simulation. Based on the relationship between the number of computing components, the operating frequency, and the pipeline length, the best selection principle is given. By analyzing the implementation method of the Multi-Port Read/Write Circuit, the computing formula of the Look-Up-Table (LUT) consumption was derived. Given the excessive use of LUTs in the original computing components, the computing components were assembled in a single typical arithmetic expression of the power system simulation program, as the basic computing formula was characterized by a subset of the typical computing formula and multiple uses of the same variable. Data communication between different computing components was realized by using Multi-Port Input Circuits that share some outputs of read controller, and Multi-Port Output Circuits, which share some outputs of computing cores. According to the test results of original FRTDS and new FRTDS, it was found that the solution proposed in this paper had a shorter ideal simulation time and a higher parallel computing capability, which was very suitable for real-time digital simulation of power systems.

S-Parameter-Based Theoretical Analysis of a Matching Network for Generic Multiport Antennas

This article describes a general method for finding an S-parameter of a matching network converting between arbitrary passive reciprocal multiport electrical circuits with the same amount of ports. In particular, the application to multiport antennas is explored. A quality of the matching is shown on a simulated 73 GHz 16-element $0.4\lambda $ -spaced bow-tie linear array, with its matched optimum realized gain achieving the theoretical maximum of the optimal gain over the $[-\pi /2,\pi /2]$ scanning arc and showing a 5 dB improvement over the unmatched case. Degrees of freedom describing different matching network’s realizations with the proposed method are enumerated, and their utilization for the transmitter amplifiers back-off reduction are presented. A fitness of the obtained matching network S-parameter for the conversion into a physical design is explored, and a practical method of obtaining a robust, feasibly realizable solution is given. The proposed network is estimated to require a quality factor 100 or better and demonstrates the useful bandwidth of 2 GHz and a good performance even with the coupling compensation reduced only to the neighboring ports.

A Multiport Circuit Breaker-Based Multiterminal DC System Fault Protection

Although hybrid circuit breaker (HCB) uses a combination of mechanical switch and insulated-gate bipolar transistors (IGBTs) to accommodate HVDC application, it still has a large number of series-connected IGBTs in its main breaker. Besides, in multiterminal HVDC system, three or more HCBs appear in cluster at one node, which worsens the HCBs’ disadvantage in volume. To simplify the breaker cluster’s topology structure and control system as well as increase the compactness, a multiport circuit breaker (MPCB) is proposed in this paper with its control procedure presented. By assembling the HCBs at one node, it can not only cut down the component count for fault interruption remarkably but also reduces the number of control signals. Apart from this, due to a more compact structure, the proposed circuit breaker avoided the use of a dc bus and, hence, dc bus fault which will result in disconnecting the node completely from the system. Hence, regardless of faults and their fault locations, it is always able to connect the remaining healthy ports together. Finally, the effectiveness of the proposed MPCB in different fault scenarios is verified by RTlab.

Energy-Based Representation of Multiport Circuits and Antennas Suitable for Near- and Far-Field Syntheses

An energy-based representation suitable for the electromagnetic characterization of linear multiport circuits and antenna systems, as well as for the optimization of antenna beamforming and near-field radio frequency-focusing performances, is presented. Radiation, ohmic, dielectric power loss, and reactive power storage are described in the concise matrix form, yielding respective eigenmodes and eigenfields that rigorously account for all energetic processes. Noteworthy eigenfields orthogonality properties are illustrated and employed to maximize (minimize) active power flow through, or to synthesize fields on, arbitrary surfaces. Applications of the proposed formulation include multiport antennas, microwave-sensing devices, microwave hyperthermia applicators, through-the-wall imaging, and wireless power transfer systems. The numerical results illustrate features and performance advantages of the proposed formulation as applied to multiport antennas and lead to define some basic design guidelines.

Symbolic Distortion Analysis of Multistage Amplifiers

This paper studies the automation of the distortion analysis of multistage operational amplifiers by a symbolic analysis. The goal is to generate the readable closed-form design equations that relate the frequency-dependent harmonic distortion (HD) features, such as dc level, corner frequency, peaking, and zero, to the circuit parameters (including the nonlinearity coefficients). Prior research achieved such kind of characterization by carrying out the traditional signal-flow graph (SFG) analysis, which is highly algebra-involved and depends mainly on the manual derivation. This paper achieves automation by formulating a multiport circuit analysis strategy and applying a topological symbolic analysis method as an intermediate step in generating nodal transfer functions. The frequency-dependent HD factors are then characterized by analytically forming proper virtual current sources associated with the nonlinearity of each stage, modeled by a cubic polynomial. Implementation shows that the proposed tool can generate approximate closed-form HD characterization with comparable accuracy to full transistor-level simulation. The proposed automation tool can substantially mitigate heavy manual derivation work required by the existing SFG-based methods. Theory, software implementation, and circuit application are covered in detail.

Efficient Multiport Equivalent Circuit for Skin and Proximity Effect in Parallel Conductors With Arbitrary Cross Sections

A broadband Foster-type circuit model for skin and proximity effect in arbitrarily shaped parallel conductors is presented. Based on a quasi-static partial element equivalent circuit approach, a modal multiport circuit is derived with a minimal computational effort, offering fast convergence and inherent stability for time-domain simulations with arbitrary active/passive nonlinear loads. The model order can be estimated rigorously for a given frequency range. The proposed model is validated in the frequency and time domain.

A ZERO-Power Sensor Using Multi-Port Direct-Conversion Sensing

This paper presents a class of zero-power microwave sensor architecture based on the direct-conversion principle to eliminate data processing at the Internet of Things sensors and provide unpowered nodes. A base station (BS) transmits a single tone signal at the frequency of $f_{0}$ /2 toward the sensing node using an antenna. At the node, an antenna receives the signal, and a passive frequency doubler makes the frequency twice. Then, a multi-port structure directly modulates the sensing data at the frequency of $f_{0}$ and sent back to the BS by an antenna. The multi-port circuit has one input, one output, and some loading ports. In this paper, a six-port modulator and four similar sensitive capacitive resonators are used. A pair of resonators senses the variation of a sample under test (SUT) while the other pair is covered by a reference or known material. At the BS, any quadrature receiver can be used to demodulate sensing data. Here, a similar six-port structure is used to extract data and find the SUT variations. An example one-node system is implemented at $f_{0} = 2.45$ GHz and evaluated by some standard SUTs. To support multiple nodes, a smart directional antenna is necessary at the BS, which also improves the overall efficiency of the system.