Equivalent Two-port Network Research Articles

An 85-GHz Power Amplifier Utilizing a Transformer-Based Power Combiner Operating Beyond the Self-Resonance Frequency

In this study, we demonstrate an 85-GHz eight-way four-stage power amplifier (PA) with transformer-based power combiners (PCs) and power splitters (PSs) operating beyond their self-resonance frequencies in 65-nm CMOS. An equivalent two-port network of a multiport PC/PS was developed to investigate the circuit behavior for estimating the possible operating frequency ranges and performing optimal impedance matching of the PA with PCs/PSs. From the results, the PA achieved a power gain of 29.3 dB with a 3-dB gain bandwidth recorded from 82.7 to 86.7 GHz, a saturated output power of 19.1 dBm with an output 1-dB gain compression point of 16.2 dBm, and a peak power-added efficiency of 8.6%. The total chip size is 0.72 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , and the core size excluding pads is only 0.172 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

Reconfigurable Transmitarray With Near-Field Coupling to Gap Waveguide Array Antenna for Efficient 2-D Beam Steering

A novel array antenna architecture is proposed that can enable 2-D (full-space) radiation pattern control and efficient beam steering. This solution is based on a gap waveguide array antenna and a reconfigurable transmitarray (TA) that are coupled in the radiative near field. An equivalent two-port network model of the coupling mechanism is presented and validated numerically. The desired TA reconfiguration capability is realized by an $8 \times 8$ array of cavity-backed patch resonator elements, where two AlGaAs p-i-n diodes are integrated inside each element providing a 1-bit phase shift. The TA is implemented in an eight-layer printed circuit board (PCB), which includes radiating elements, fixed phase-shifting inner-stripline sections, impedance matching, and biasing circuitry. The combined antenna design is low profile (~1.7 wavelength) owing to the small separation between two arrays (~0.5 wavelength), as opposed to conventional TAs illuminated by a focal source. The design procedure of the proposed architecture is outlined, and the measured and simulated results are shown to be in good agreement. These results demonstrate 23.5–25.2 GHz −10-dB impedance bandwidth and 23.3–25.3 GHz 3-dB gain bandwidth, a beam-steering range of ±30° and ± 40° in the E- and the H-planes with the gain peak of 17.5 dBi, scan loss $\le3.5$ dB, and TA unit cell insertion loss $\le1.8$ dB, respectively.

Efficient Method for Calculating the Shielding Effectiveness of Axisymmetric Multilayered Composite Enclosures

An efficient method is proposed to determine the shielding effectiveness of an axi symmetric multilayered composite enclosure by using a generalized transition matrix. In this method, each layer is approximated with a generalized transmission line and the interface between two consecutive layers is modeled by an equivalent two-port network. The method of moments (MoM) solution of the governing surface integral equations at each layer is elucidated in detail to determine the parameters of the respective network and the transmission operator relating the neighboring layers. The resultant cascaded network is used to relate the tangential components of the transferred fields to the tangential components of the incident field, enabling one to compute the shielding properties of the enclosure. The main feature of the proposed method is its remarkable high computation speed as compared to the conventional methods wherein the layers and their respective interfaces are treated simultaneously, causing the size of the impedance matrix in the MOM to become excessively large. The efficiency of the proposed model is demonstrated by comparing the simulation results of several case studies with those available in the literature and obtained using a commercial finite integration technique code.

Two-port network equivalent of VSC-HVDC for power flow studies

This paper presents a novel harmonic domain (HD) approach that computes a two-port network equivalent of a switching converter for power flow studies. The equivalent stems from the harmonic domain admittance matrix (HDAM) of a switching converter which accounts for harmonics interaction. Power flow studies, involving switching converters, require modifying the Jacobian matrix via calculation and incorporation of the partial derivative terms corresponding to the switched part within the iterative solution process. The proposed approach is readily applicable to modern power systems involving electronic converters. Also, it avoids calculating partial derivative terms of the switching converter by including it as a simple, yet an effective, equivalent two-port network, i.e., by just modifying the admittance matrix within the iterative power-flow solution process. This paper demonstrates that the procedure to obtain the PI equivalent is general for any linear time-periodic system and does not rely on library components when embedded into a commercial software tool.The proposed approach is validated by two test networks which involve High-Voltage Direct Current (HVDC) systems. The obtained results are compared, in terms of accuracy, with those given by the Power System Computer-Aided Design/Electromagnetic Transients including Direct Current (PSCAD/EMTDC) software tool, which involves the detailed system model, once steady-state is reached. Also, the results of the proposed approach are verified against those obtained from a dedicated power flow software tool, i.e., Power System Simulator for Engineering (PSS/E).

Middle range wireless power transfer systems with multiple resonators

The equivalent two-port network model of a middle range wireless power transfer (WPT) system was presented based on strongly coupled multiple resonators. The key parameters of the WPT system include self-inductance, resistance, parasitic capacitance, mutual inductance and S-parameters of coils & resonators were analyzed. The impedance matching method was used to optimize load power and transmission efficiency of the multi-resonator WPT system, and the impedance matching method was realized through adjusting the distances between the coils and resonators. Experiments show that the impedance matching method can effectively improve load power and transmission efficiency for middle range wireless power transfer systems with multiple resonators, at distances up to 3 times the coil radius with efficiency more than 70% and load power also close to 3.5 W.

Absolute Stability of Multi-DOF Multilateral Haptic Systems

Multi-degree-of-freedom (DOF) multilateral haptic systems involve teleoperation of several robots in physical environments by several human operators or collaborative interaction of several human operators in a virtual environment. An $m$ -DOF $n$ -lateral haptic system can be modeled as an $n$ -port network where each port (terminal) connects to a termination defined by $m$ inputs and $m$ outputs. The stability analysis of such systems is not trivial due to dynamic coupling across the different DOFs of the robots, the human operators, and the physical/virtual environments, and unknown dynamics of the human operators and the environments exacerbate the problem. Llewellyn's criterion only allows for absolute stability analysis of 1-DOF bilateral haptic systems ( $m=1$ and $n=2$ ), which can be modeled as two-port networks. The absolute stability of a general $m$ -DOF bilateral haptic system where $m>1$ cannot be obtained from $m$ applications of Llewellyn's criterion to each DOF of the bilateral system. In addition, if we were to use Llewellyn's criterion for absolute stability analysis of a general 1-DOF $n$ -lateral haptic system where $n>2$ , we would need to couple $n-2$ terminations of the $n$ -port network to (an infinite number of) known impedances to reduce it to an equivalent two-port network; this is a cumbersome process that involves an infinite number of applications of Llewellyn's criterion. In this brief, we present a straightforward and convenient criterion for absolute stability analysis of a class of $m$ -DOF $n$ -lateral haptic systems for any $m\geq 1$ and $n\geq 2$ . As case studies, a 1-DOF trilateral and a 2-DOF bilateral haptic system are studied for absolute stability with simulations and experiments confirming the theoretical stability conditions.

A Transponder-Based, Nonradiative Wireless Power Transfer

A transponder-based system is proposed for wireless nonradiative power transfer. The system consists of three elements: a transmitter, a receiving loop, and a transponder at a fixed distance from the transmitter. The transmitter and the transponder are made of concentric, reactively loaded wire loops. One loop of the transmitter is directly fed by a power source, while its remaining loops and those of the transponder act as parasitic loops. The reactive impedances of the parasitic loops comprising the transmitter and transponder are chosen to maximize power transfer from the source to the receiving loop. The equivalence of the system with a two-port network is used to derive the required reactive impedances. A conjugate impedance match is applied to both input and output ports of the equivalent two-port network for maximum power transfer. The proposed transponder-based scheme overcomes the monotonic decay of efficiency with distance that is seen in classical wireless power transfer systems. An improvement in efficiency exceeding 50% is achieved at larger distances when compared to similar systems without a transponder.

Accurate Bloch Analysis of 1-D Periodic Lines Through the Simulation of Truncated Structures

A common approach to perform dispersive analyses of waveguides periodic along one direction is based on the electromagnetic simulation of a single spatial period of the structure. However, the resulting equivalent two-port network representation of the single cell may lead to inaccurate modal results, since mutual coupling between cells has been neglected. When a finite number of adjacent cells are simulated, with the aim of improving the accuracy of the analysis, spurious solutions are introduced; they are shown here to be related to the nonuniqueness of root-extraction operations in the complex plane. A simple automatic method is proposed to recover the correct solution and to test the convergence of the analysis as the number of simulated cells is increased.

Shared control architectures for haptic training: Performance and coupled stability analysis

A novel shared control architecture is presented for dual-user haptic training simulation systems for enhanced interaction between the users and between each user and the virtual environment. The coupled stability of the proposed control architecture against uncertainties in the environment and the user’s dynamics is investigated using the three-port master–slave network model of the dual-user haptic simulation system. For this purpose, Llewellyn’s unconditional stability criterion is applied to an equivalent two-port network model obtained from the corresponding three-port network, considering the environment as a load termination. The kinesthetic performance of the proposed architecture is numerically analyzed for transparency and evaluated against a benchmark control architecture under different operating conditions, such as various types of environments, users’ grasps, and levels of dominance of users over the task. An experimental user study is carried out to assess the effectiveness of the proposed architecture in terms of users’ perception of environment stiffness sensing, device agility, and haptic guidance reception.

Comments on “Comments on ‘Measuring the Impedance of Balanced Antennas by an S-Parameter Method’”

In [1], the authors presented an equivalent two-port network for the balanced antenna, as shown in Figure 1. For such a two-port network, the S matrix was given by S prime equal square brackets with a particular multivaried matrix structure (1) The antenna's impedance can be expressed as Z equal two Z zero S prime eleven all over 1 minus S prime eleven (2) or Z equal two Z zero multiplies with one minus S prime twelve all over S prime twelve (3) where S′ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</inf> and S′ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</inf> are the S parameters of the equivalent two-port network, and Z <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf> is the characteristic impedance. The antenna's impedance can be calculated by using Equation (2) or (3).