Impedance Results Research Articles

Nth order current mode universal filter using MOCCCIIs

This article presents a new current mode single-input-multiple-output nth order universal filter. The proposed circuit employs (n + 1) number multiple output second generation current conveyors and n number grounded capacitors only. Presented circuits can realize current mode low pass, high pass, band pass, notch and all pass responses simultaneously at different high output impedance terminals. The current mode filter circuit provides low input impedance by selecting the proper value of bias current and also has high output impedance, which is suitable for cascading. The circuit offers some important features such as resistor less realization, no passive component matching constraints, low sensitivity, electronic tunability and active-C realization. The functionality of the proposed filter circuit is tested with the PSPICE simulation, which is found to agree well with the proposed theory.

A Coupled Line Impedance Transformer for High Termination Impedance with a Bandpass Filtering Response

A Coupled Line Impedance Transformer for High Termination Impedance with a Bandpass Filtering Response

Dual Feed Pattern Reconfigurable Antenna for Wireless Applications

In this paper, a novel dual band dual feed multiple input multiple output reconfigurable antenna is designed. On-plane printing methodology is focused in designing the antenna. To implement the design, a circular Defected Ground Structure (DGS) with concentric split ring is employed beneath the signal plane and the reconfiguration is attained without using any switching elements. The signal plane comprises of octagonal ring pattern with orthogonal dual feed arrangement. The antenna prototype has the dimension of 0.66ź × 0.66ź, where the octagonal ring is of 0.34ź. An impedance of 50 Ω is maintained in designing the prototype. The dual band has been achieved by the periodic property of split ring employed within the circular DGS in the ground plane. Alternate shorting of ports has been performed to attain the reconfiguration. The prototype is designed to be utilized in public safety and aeronautical radio navigation under US standards at 0.816 and 1.072 GHz with reflection coefficients of ź 17 and ź 21 dB respectively. The patterns have been reconfigured by terminating one of the ports with 50 ź impedance termination. This resulted in change of beam directions, attaining pattern reconfiguration.

Sub‐synchronous oscillation mechanism and its suppression in MMC‐based HVDC connected wind farms

A subsynchronous oscillation (SSO) phenomenon in a wind farm integrated with a modular multilevel converter (MMC)-based high-voltage direct current (HVDC) transmission system has been recently observed in the real world. An attempt is made in this paper to contribute to the understanding of the root cause of the SSO in the MMC-HVDC connected wind farms. For that, the small-signal impedance model of the MMC is first developed based on the harmonic state-space (HSS) modelling method. An inherent low-frequency resonance peak in the MMC excluding any control influence is identified by its terminal impedance. Arguably, this could be the reason why the SSO occurs in the MMC-HVDC connected wind farms. In addition to that, the influence factors, such as main circuit parameters, controller parameters, and power level, on the stability of the interconnected system are examined, which can provide guidelines for the system design in order to guarantee the stability of the interconnected system. Based on the mechanism analysis, a stabilization control for suppressing the SSO in the MMC-HVDC based wind farms is also proposed. Finally, the theoretical analysis and stabilization control are validated by both time-domain simulations and field measurements in a real MMC-HVDC connected wind farm in China.

A Method for Acquiring the Terminal Common Mode Impedance of Cables

A method is presented for quickly acquiring the equivalent terminal common-mode impedance of cables. Firstly, the parallel cables are treated as equivalent multi-conductor transmission line. Using vector network analyzer (VNA) and current probe to measure voltage reflection coefficients at two locations of each cable. Then a nonlinear equation about terminal equivalent impedance is constructed. By solving the nonlinear equations, broadband terminal equivalent impedance for each cable can be acquired. Compared with existing methods, the efficiency of this method is improved significantly. Furthermore, the precision is improved in that this method including the coupling effect between cables. This method helpful to the EMC test and fault diagnosis.

Active Control of Pressure Resonance in Long Pipeline of Bottom Founded Hydraulic Wind Turbines Based on Multi-Objective Genetic Algorithm

The long pipeline in bottom-founded hydraulic wind turbines will greatly reduce the system natural frequency, and pressure resonances can occur more easily at multiple frequencies under time-varying wind excitation, which will reduce the electrical power quality and endanger the safe operation of the system. First, the hydraulic system impedance model is established based on electric–hydraulic analogy, and the pressure transfer function of two ends of the long pipeline is obtained, based on which the pressure resonance condition equation is solved by theoretical derivation. Furthermore, the multiple parameters sensitivity analysis of resonant frequency is carried out by using Isight and MATLAB. A novel active control strategy of pressure resonance is proposed, where the variable motor is adopted as the control object for real-time control of the terminal impedance to make the resonance frequency avoid the excitation frequency, and its feasibility is verified. Finally, with the objectives of optimizing the pressure pulsation attenuation and wind energy loss, a multi-objective genetic algorithm is used to optimize the parameters of the control object. A reliable Pareto set is obtained through multiple iterations, and different degrees of resonance suppression can be achieved.

Unequal termination impedance parallel-coupled lines band-pass filter with arbitrary image impedance

This paper presents an analytical design for a microstrip parallel-coupled line bandpass filter (BPF) with arbitrary termination and image impedances. Using the proposed design formulas, multistage arbitrary termination impedance BPFs can be designed with a very high impedance transforming ratio (r). The fractional bandwidth and return losses are maintained even though the r and image impedance are varied. To validate the design formulas, two- and three-stage BPFs are fabricated and measure at the center frequency (f0) of 2.6 GHz. The filter 1 and filter 2 are designed with termination impedances of 50–300 Ω and 20–50 Ω, respectively. The measured results of both filters show a good agreement with the simulations. The measured passband insertion and return losses of filter 1 are better than 0.8 and 19.6 dB, respectively. Similarly, the measured passband insertion and return losses of filter 2 are better than 1.5 and 19 dB, respectively.

A Method for Acquiring the Terminal Common Mode Impedance of Cables

A Method for Acquiring the Terminal Common Mode Impedance of Cables

Analysis of Output Loading Effects in Autonomous Circuits

A methodology is presented to analyze the impact of the termination load on the oscillation frequency and output power of autonomous circuits. Variations of this load can also lead to an extinction of the oscillation signal, due to their effect on the impedance seen by the active device(s). The new methodology enables an efficient analysis and mitigation of the pulling effects, in the case of undesired output mismatch, as well as an efficient oscillator synthesis in large-signal conditions, for specified values of oscillation frequency and output power. The method is based on the calculation of constant-amplitude and constant-frequency contours, traced in the Smith chart. Oscillation extinctions and some forms of hysteresis can be predicted through the inspection of these contours. However, the stability properties will generally depend on the frequency characteristic of the termination impedance. In an oscillator synthesis, the selected impedance, providing the specified values of oscillation frequency and output power, must be implemented in order to guarantee a stable solution. The dependence of the phase-noise spectral density on the particular implementation is predicted, combining an analysis based on the variance of the phase deviation with the conversion-matrix approach.

임의의 종단 임피던스를 갖는 고출력 증폭기용 다층 구조형 3dB 결합기 설계

임의의 종단 임피던스를 갖는 고출력 증폭기용 다층 구조형 3dB 결합기 설계

Analysis and design of an unequal termination impedance power divider with bandpass filtering response

The design of an unequal termination power divider (PD) with a bandpass filtering response and wide out-of-band suppression characteristics is presented. The two-cascaded coupled lines can be designed with a low impedance transforming ratio. For the validation, a 50-to-5 Ω termination impedance PD was implemented at a centre frequency (f 0) of 2.6 GHz. The measured results are in good agreement with the simulations, showing input and output return losses that are better than 19 dB over a passband bandwidth of 190 MHz (2.51–2.7 GHz), and an out-of-band suppression that is better than 19.6 dB from DC to 2.25 and 2.9 to 7.2 GHz. The isolation between the output ports is 39.2 dB at f 0, and it is better than 19 dB with a broadband frequency (DC to 7.2 GHz).

SNEM: Full S-Parameter Synthesis From Near-End Measurement

A novel method called SNEM (full S-parameter synthesis from near-end measurement) is proposed to obtain the full S-parameter matrix by probing only a subset of all the ports of a passive linear time-invariant network. Other ports that are not probed need to be terminated by various impedance values. The traditional open-short-load method is a special case in the SNEM framework. A termination error correction algorithm and a guideline for choosing termination impedance values have also been developed to make the method robust, accurate, and efficient. Examples are included in this paper to demonstrate the applications of the SNEM method in integrated circuit package, on-die structure, and socket/connector characterizations. Simulation results also show that the SNEM method can be applied to power line communication system characterization. The SNEM method has been validated by both simulations and lab measurements.

Prediction of odd-mode instabilities under output mismatch effects

A methodology is presented to predict odd-mode instability in power amplifiers under output mismatch effects, as in the case of amplifiers connected to an antenna. This kind of instability is often observed in multi-device configurations, due to their symmetry properties. Unlike the single-ended situation, there is a cancellation of odd multiples of the oscillation frequency at the circuit output, so there is no impact of the load-impedance values at the sideband frequencies. The odd-mode instability only depends on the impedance terminations at the fundamental frequency and its harmonic terms, and can only be detected within the circuit unstable loop, instead of the antenna-connection terminals. The possible unstable modes are related with the eigenvectors of an outer tier conversion matrix accounting for the symmetry properties of the circuit topology. Under sufficient low-pass filtering of the amplifier output network, the analysis parameters can be limited to the magnitude and phase of the reflection coefficient at the fundamental frequency. This analysis involves a computationally efficient graphical technique to detect potential instabilities and a bifurcation-detection method to determine the instability boundaries in the Smith chart. The two main types of instability from periodic regime are considered, respectively associated with incommensurable and subharmonic oscillations. Results have been validated through pole-zero identification and experimental measurements.

Influence of the MV/LV Transformer Impedance on the Propagation of the PLC Signal in the Power Grid

Improving the operation of power grid and offering new smart applications, the deployment of a supervisory infrastructure is necessary. One solution to transmit data may be based on the power-line communication (PLC) technology. It consists of the superposition of high-frequency signals with the electrical signal of 50/60 Hz. However, the power grids have not been designed to operate in high frequencies. Therefore, they provide a transmission channel with difficult propagation conditions. This paper deals with the modeling of the medium-voltage/low-voltage (MV/LV) power transformers in PLC frequencies. The proposed models are based on the “lumped model” and “black box model.” They are performed in the frequency band from 1 kHz to 1 MHz on SPICE and MATLAB software, respectively. These models are based on impedance measurements and validated by experimental data. The advantages and drawbacks of each model are detailed from the presentation of the modeling method and simulation results. The comparison of the simulation results show that “black box model” offers good accuracy. The transmission results show that transformers are an important element in PLC studies because they provide significant losses. Moreover, these losses depend mainly on the values of the impedance terminals of the MV/LV transformer.

A New Resistorless and Electronic Tunable Third-Order Quadrature Oscillator with Current and Voltage Outputs

ABSTRACTThis paper presents a new resistorless and electronic tunable third-order quadrature oscillator based on voltage difference transconductance amplifiers (VDTAs). The proposed configuration using two VDTAs and three grounded capacitors has three current outputs and two voltage outputs. The resistorless circuit enjoys electronically and independently control of oscillation condition and oscillation frequency. It can simultaneously provide two quadrature output voltages, two quadrature output currents, and one amplitude-controllable output current. All the current output terminals possess high-output impedance terminals. The active and passive sensitivities of the quadrature oscillator are low. The simulation and experimental results are included to validate the theoretical analysis.

New Design of a Variable Impedance Based on Polarized Diodes at Microwave Frequency

In this letter, we present a new variable impedance termination consisting of two polarized diodes. To generate a complex-valued impedance, two controlled current sources polarize the diodes, which are interconnected with a Wilkinson power divider through transmission lines of different electric lengths. Because of the reduced number of diodes, this structure presents low power consumption and simple control. We validated the proposed design by implementing a prototype at the operating frequency of 1575.42 MHz. Mapping the measured results in the Smith chart, the impedance can produce reflection coefficients with full-phase coverage within the circle of magnitude 0.35 over a frequency range of 1.5–1.6 GHz.

Nulls-Free Wireless Power Transfer With Straightforward Control of Magnetoinductive Waves

We present a straightforward and yet, effective method to modulate the termination impedance of 1-D $LC$ resonating arrays for wireless power applications. The modulation method is based on activating/deactivating the last two cells of the array allowing to remove the power nulls caused by standing waves inside this type of arrays. The modulation of the terminating impedances is done at a distinct frequency than the resonance frequency of the cells. We explain why and how this distinct frequency was chosen. We further demonstrate how the same modulation is applicable for a wide range of load resistances on the receiver device. Modulation is achieved by wirelessly sensing the voltage delivered by the power supply according to where above the array a receiver device is located. A microcontroller records these voltages and determines which terminating impedance will provide the highest possible efficiency to the receiver device. Changes in the terminating impedances are set by digitally controlled solid state relays. The proposed modulation method permitted to power up a receiver device with a system efficiency of up to 60% anywhere over the 30 cm length of the resonating array.

Universal Voltage Conveyor and its Novel Dual-Output Fully-Cascadable VM APF Application

This letter presents a novel realization of a voltage-mode (VM) first-order all-pass filter (APF) with attractive features. The proposed circuit employs a single readily available six-terminal active device called as universal voltage conveyor (UVC) and only grounded passive components, which predict its easy monolithic integration with desired circuit simplicity. The auxiliary voltage input (W) and output (ZP, ZN) terminals of the device fully ensure easy cascadability of VM APF, since the input and output terminal impedances are theoretically infinitely high and zero, respectively. Moreover, thanks to mutually inverse outputs of the UVC, the proposed filter simultaneously provides both inverting and non-inverting outputs from the same configuration. All of these features make the UVC a unique active device currently available in the literature. The behavior of the filter was experimentally measured using the readily available UVC-N1C 0520 chip, which was produced in cooperation with ON Semiconductor Czech Republic, Ltd.

Electromagnetic, complex image model of a large area RF resonant antenna as inductive plasma source

A large area antenna generates a plasma by both inductive and capacitive coupling; it is an electromagnetically coupled plasma source. In this work, experiments on a large area planar RF antenna source are interpreted in terms of a multi-conductor transmission line coupled to the plasma. This electromagnetic treatment includes mutual inductive coupling using the complex image method, and capacitive matrix coupling between all elements of the resonant network and the plasma. The model reproduces antenna input impedance measurements, with and without plasma, on a m2 antenna used for large area plasma processing. Analytic expressions are given, and results are obtained by computation of the matrix solution. This method could be used to design planar inductive sources in general, by applying the termination impedances appropriate to each antenna type.

Enhancement of Turbo-Generators Phase Backup Protection Using Adaptive Neuro Fuzzy Inference System

This research work presents an advanced solution for the problem due to the current setting of Relay (21). This problem arises when it is set to provide thermal backup protection for the generator during two common system disturbances, namely a system fault and a sudden application of a large system load. These investigations are carried out using Adaptive Neuro Fuzzy Inference System (ANFIS). The results of the investigations have shown that the ANFIS has a promising tool when applied for turbo-generators phase backup protection. The effect of this tool varies according to the type of input data used for ANFIS testing and validation. The proposed method in this paper proposes the use of two different sets of inputs to the ANFIS, these inputs are the generator terminal impedance measurements (R and X) and the generator three phase terminal voltages and currents (V and I). The dynamic simulations of a test benchmark have been conducted using the PSCAD/EMTDC software. The results obtained from the ANFIS scheme are encouraging.