Short Transmission Line Research Articles

A Low-Noise Transmission-Type Yttrium Iron Garnet Tuned Oscillator Based on a SiGe MMIC and Bond-Coupling Operating up to 48 GHz

Wideband and low-noise tunable oscillators at microwave frequencies are crucial within microwave frequency synthesizers and key to high-end measurement systems based on electromagnetic sensing in the microwave range as well as in the terahertz (THz) and sub-THz range. This paper presents a novel, wideband, and low-noise differential yttrium iron garnet (YIG) tuned oscillator. It is based on a SiGe monolithic microwave integrated circuit and a transmission-type YIG resonator. The integrated circuit contains a fully differential amplifier as a part of the oscillator core. The resonator was realized by two orthogonal, crossed pad-to-pad bonds and an YIG sphere, which is positioned between those bonds and the integrated circuit. To design and optimize the oscillator, an equivalent circuit modeling the resonator was developed. Concerning the tuning range and the phase noise, the results of the circuit simulations are in good agreement with the measurements. Two oscillators with different lengths of the inductive load transmission line were realized. First, the oscillator with a short transmission line offers very high-oscillation frequencies with a tuning range from 32.0 to 48.2 GHz. It exhibits an excellent phase noise of less than -119dBc/Hz at an offset frequency of 100kHz for oscillation frequencies up to 42GHz. Second, the oscillator with a longer transmission line length offers a tuning range from 19.1 to 41.4 GHz. This configuration exhibits an excellent phase noise of less than -120dBc/Hz at an offset frequency of 100 kHz for oscillation frequencies up to 38GHz.

Novel Subwavelength Magnetic Conductor Surface of Lumped Element Electrical Network

It is shown experimentally that a 2-D lumped element electrical network composed of inductors, capacitors ( $LC$ ), and short transmission lines functions as an artificial magnetic conductor (AMC) surface, and that it reflects electromagnetic fields with only a fraction of surface area that is much smaller than the wavelength. In contrast to the existing electromagnetic metamaterials, our AMC surfaces have the unit cell size of 1/50 of wavelength and the overall surface size of 1/10 of wavelength or even smaller. The magnetic conductor property is confirmed by the measurement of reflection from the AMC surface and by the unidirectionality of antennas closely backed by the AMC.

Electromagnetic Field Coupling Between a Horizontal Loop Antenna and a Transmission Line: An Analytical Time-Domain Model

The time-domain electromagnetic (EM) reciprocity theorem and the Cagniard–DeHoop technique are applied to analyze the pulsed EM coupling between a horizontal small loop antenna and a finite transmission line above the perfect ground. It is demonstrated that this approach yields closed-form analytical formulas describing the impact of transmission, EM propagation, and reception on the exciting pulse signature. Moreover, approximate expressions applying to relatively short transmission lines are given and discussed, thus revealing similarities with the loop-to-loop EM coupling. Numerical results are presented and validated using an alternative analytical solution and an EM computational tool.

Time and Frequency Domain Response of HTS Resonators for Use as NMR Transmit Coils.

Replacing normal metal NMR coils with thin-film high-temperature superconductor (HTS) resonators can significantly improve the sensitivity of analytical NMR. To study the use of these resonators for excitation as well as detection, we investigated the radio frequency properties of the HTS NMR coils in both frequency and time domain at a variety of transmit power levels. Experiments were conducted on a double-sided, counter wound spiral resonator designed to detect NMR signals from 13C nuclei at 14.1 T. Power-dependent nonlinearity was observed in the transmission coefficient and quality factor. The ability of the HTS resonators to accurately generate short pulses was studied in the time domain over the range power levels. The results of this study show that some form of Q switching is needed to get good transmit performance from HTS coils for 13C. For that purpose, the effect of adding a shorted transmission line stub to improve the pulse shapes and reduce phase transients was studied.

Small signal fault analysis for renewable energy (Wind) power system distributed generation by using MATLAB software (Simulink)

<span>In distribution system, wind power plants are becoming popular renewable energy sources. It employs Doubly Fed Induction Generator (DFIG) to generate power based on wind conversion. Short and long transmission lines, presence of faults and presence of Static Synchronous Compensator (STATCOM) are highlighted issues in this paper. Basically, this research develops investigations on some electrical variables such as voltage and current to control them. Distribution Static Synchronous Compensator (DSTATCOM) is proposed in this paper. Wind farm acts as a source while DSTATCOM is connected to the distribution system with a DFIG based wind farm. The controller proposed is DSTATCOM is modeled and simulated in MATLAB/SIMULINK and the results are given. A microgrid based small signal analysis is performed in the laboratory using MATLAB and different comparisons are made and simulation case studies are presented and validated.</span>

Fault analysis for renewable energy power system in micro-grid distributed generation

<span>In distribution system, wind power plants are becoming popular renewable energy sources. It employs Doubly Fed Induction Generator (DFIG) to generate power based on wind conversion. Short and long transmission lines, presence of faults and presence of Static Synchronous Compensator (STATCOM) are highlighted issues in this paper. Basically, this research develops investigations on some electrical variables such as voltage and current to control them. Distribution Static Synchronous Compensator (DSTATCOM) is proposed in this paper. Wind farm acts as a source while DSTATCOM is connected to the distribution system with a DFIG based wind farm. The controller proposed is DSTATCOM is modeled and simulated in MATLAB/SIMULINK and the results are given. A microgrid based small signal analysis is performed in the laboratory using MATLAB and different comparisons are made and simulation case studies are presented and validated.</span>

Small Signal Fault Analysis for Renewable Energy (Wind) Power System Distributed Generation by Using MATLAB Software (Simulink)

In distribution system, wind power plants are becoming popular renewable energy sources. It employs Doubly Fed Induction Generator (DFIG) to generate power constructed on wind conversion. Short and long transmission lines, presence of faults and presence of Static Synchronous Compensator (STATCOM) are highlighted issues in this paper. Basically, this research develops investigations on some electrical variables such as voltage and current to control them. Distribution Static Synchronous Compensator (DSTATCOM) is proposed in this paper. Wind farm acts as a source while DSTATCOM is associated with the distribution system with a DFIG based wind farm. The controller proposed is DSTATCOM is modeled and simulated in MATLAB/SIMULINK and the results are given. A microgrid based small signal analysis is performed in the laboratory using MATLAB and different comparisons are made and simulation case studies are presented and validated.

Inverse spin Hall effect in Nb doped SrTiO<sub>3</sub>

The inverse spin Hall effect (ISHE), namely spin flows converted into charge currents due to spin orbital interaction, is investigated extensively in heavy metals, such as Pt, W, Au, etc. Recently, the effect was also found in Cu doped with Au. Their difference is that the spin Hall effect is from the intrinsic effect which is related to the topological character of the electronic bands, while the ISHE is mainly from the extrinsic spin dependent scattering by the impurities. The impurity scattering can give opportunities to tune the effect, for example by impurity concentration, which is impossible by the intrinsic mechanism. In this work, we extend the material to the doped oxides. NiFe films are deposited on undoped and doped SrTiO<sub>3</sub> substrates by magnetron sputtering, respectively. The spins are injected from the magnetic thin films by spin pumping through using a shorted microstrip transmission line fixture at different frequencies and room temperature. The spin rectification voltage and the inverse spin Hall voltage in the doped sample are separated by the inverting spin injection direction method, which is realized by flipping the samples. The results show that in the undoped SrTiO<sub>3</sub> substrate, the voltage curves before and after flipping the sample are basically the same, which is due to the voltage generated by the spin rectification effect of the NiFe film. For Nb-doped SrTiO<sub>3</sub> substrates with Nb concentration <i>x</i> = 0.028, 0.05, 0.1, 0.15 and 0.2, the inverse spin Hall voltage decreases with doping concentration increasing and is not detectable in sample with doping concentration of 0.15, nor with doping concentration of 0.2. The decrease of the ISHE effect may be due to the spin coherent length decreasing with the increase of the impurity concentration. The correlation between spin-charge conversion and transportation needs knowing in detail. Nevertheless, the results show that by doping strong spin-orbit coupling impurities into SrTiO<sub>3</sub>, thus by changing the doping concentration, the inverse spin Hall effect in SrTiO<sub>3</sub> can be controlled. This tunable spin-charge conversion provides more possibilities for developing the spintronic devices and it will have great potential applications in the future.

On the Radiated Susceptibility of a Two-Wire Transmission Line Under Near- and Far-Field Conditions

An analytical transmission line (TL) coupling model is presented for evaluating the deviation between the susceptibility of a DUT in the near- and far-field of a noise source. Appropriate field solutions of elementary antennas are used in combination with coupling equations of an electrically short two-wire TL. A normalized coupling is defined to quantify the difference between the near- and far-field disturbances. It is found that the field coverage and the wave impedance of the radiating source are the dominant factors. The evaluation of the normalized coupling voltage results in potential deviations up to an order of magnitude. Therefore, it is concluded that standard EMC-test in the far-field may not always reflect the coupling level under different realistic circumstances appropriately. The analytical model is validated by accurate three dimensional field simulations and experiments.

Penetrating power characteristics of half-wavelength AC transmission in point-to-grid system

With the concept of global energy interconnection being proposed, half-wavelength alternating current transmission (HWACT) technology becomes of more interest. HWACT lines can be adopted to establish a point-to-grid system, in which the penetrating power (PP) is produced between receiving terminals, having a significant effect on the power flow distribution. In order to investigate this phenomenon, the PP characteristics of the HWACT system are researched in this paper. First, the mathematical relationship between the transmission power and terminal bus voltages of a single HWACT line is derived using the equations of a distributed parameter model. The research indicates that the relationship between power and terminal voltages shows “reverse characteristics” opposite to those of regular short transmission lines. Then, the concept and definition of PP in a point-to-grid system with two receiving terminals are proposed, and the corresponding relationship between PP and the terminal bus voltages is derived. Simulations are carried out to validate the theory under different conditions, so that the accuracy and adaptiveness of the theoretical analysis can be proved. In addition, the results demonstrate that selecting the location for a HWACT system has demanding requirements in order to control the value of PP.

Three-Wave Mixing as the Limit of Nonlinear Dynamics Theory for Nonlinear Transmission Line-Type Metamaterials

Using nonlinear dynamics (NLD) theory, a linear time periodic equivalent circuit of a sinusoidally pumped distributed transmission line-type metamaterial is proposed. For small pump power and sufficient number of unit cells, it is shown that three-wave mixing, coupled with phase matching, can be used to determine the frequencies of the autonomous components and their propagation behavior. The resulting signal and idler waves satisfy the well-known Manley-Rowe relation. However, unlike NLD theory and stability analysis, three-wave mixing can be inaccurate for relatively large input power levels and/or short transmission lines. In particular, the waveform profile and consequently radiation of the autonomous frequencies located inside the light cone cannot be described using three-wave mixing and NLD and/or stability analysis must be applied.

Kalman filter estimation of RLC parameters for UMP transmission line

This paper present the development of Kalman filter that allows evaluation in the estimation of resistance (R), inductance (L), and capacitance (C) values for Universiti Malaysia Pahang (UMP) short transmission line. To overcome the weaknesses of existing system such as power losses in the transmission line, Kalman Filter can be a better solution to estimate the parameters. The aim of this paper is to estimate RLC values by using Kalman filter that in the end can increase the system efficiency in UMP. In this research, matlab simulink model is developed to analyse the UMP short transmission line by considering different noise conditions to reprint certain unknown parameters which are difficult to predict. The data is then used for comparison purposes between calculated and estimated values. The results have illustrated that the Kalman Filter estimate accurately the RLC parameters with less error. The comparison of accuracy between Kalman Filter and Least Square method is also presented to evaluate their performances.

Analytically calculate shielding effectiveness of enclosure with horizontal curved edges aperture

An analytical method is presented for calculating the shielding effectiveness (SE) of an enclosure with a horizontal curved edges aperture. Based on the transmission line theory, the horizontal curved edges aperture is treated as many short coplanar strip transmission lines connected in series. Then the equivalent impedance of the curved edges aperture is calculated by the iterative formula proposed in this Letter. Submitting the equivalent impedance into the existing equivalent circuit, the SE of the enclosure with a horizontal curved edges aperture can be calculated efficiently and precisely. The proposed method was validated with measurements and the transmission line matrix algorithm.

Hybrid fault diagnosis algorithms for transmission lines

This paper presents a fault location method for transmission lines with the application of a mono-objective optimization technique using the ellipsoid algorithm with voltage and current data of both terminals. The fault detection is performed using the stationary wavelet transform and Parseval’s theorem, and the classification was conducted with the application of artificial neural networks. The minimization of the objective function defined for the short and long transmission line models provides not only the distance to the fault point, but also the fault resistance value. Many short-circuit situations simulated in the alternative transients program are tested with variations in the fault type, adjustments in the distance to the fault point, and fault resistance. The results of the algorithm applied to real faults in the electrical system of Brazil are also presented and compared to the values obtained with a classic fault location algorithm. According to the observations, the adopted formulation achieves the pre-established objectives, with mean errors of fault location for the real cases lower than 2% of the line length.

The delta-models of reactive elements and low-pass filters

Frequency limitations of lumped and distributed reactive elements traditional models are considered. Based on equivalent ciruit of infinitely short transmission line section inductance and capacitance models with properties correspond to delta-function are received. These models called delta-models are without frequency restrictions. In the delta-model graphic designation delta-function length is directly proportional to inductance or capacitance value. Unlike to ordinary graphic designations delta-models allow to represent scheme reactivities values ratios. Traditional models and delta-models reactive elements frequency characteristics are compared. It is found that because of frequency limitations traditional planar microstrip quasi-lumped reactive elements characteristics have substantial errors. Considerable reduction of errors is ensured by microstrip quasi-lumped reactive elements on the basis of three-dimensional inhomogeneities. Based on reactive elements delta-models Butterworth and Chebyshev low-pass filters delta-models are presented. Low-pass filter delta-model "prompt" possibility of filter selectivity increasing. Frequency characteristics of Chebyshev low-pass filter designed on traditional planar microstrip quasi-lumped reactive elements and three-dimensional inhomogeneities are given.

Noniterative Parameter-Free Fault Location on Untransposed Single-Circuit Transmission Lines

Extra high voltage transmission networks include many untransposed single-circuit overhead lines with horizontal configuration of phase conductors. This paper develops a setting-free fault-location method specific to these types of transmission lines. Utilizing synchronized measurements at line terminals, the proposed method accurately locates faults irrespective of fault type, fault resistance, external network parameters, and faulted-line parameters. As such, fault location is robust against ambient conditions as well as inherent inaccuracy of line parameters. The bisymmetry of the impedance matrix of the line is utilized to obtain a closed-form solution for fault location on short transmission lines. For long transmission lines, shunt capacitance of the line is taken into account to obtain an accurate closed-form estimation for fault location. Electromagnetic transient simulation in PSCAD/EMTDC environment validates the accuracy of the proposed fault-location method for a long untransposed 400-kV transmission line. The obtained results are also compared with an existing noniterative parameter-free fault-location method to demonstrate salient features of the proposed method.

Low insertion loss and high isolation capacitive RF MEMS switch with low pull-in voltage

Micro electromechanical system (MEMS) shunt capacitive switches behave chiefly as a capacitor at both up and down states. Therefore, input-output matching for these switches is affected by varying the frequency. Although increasing the amount of capacitance at the up state reduces the actuation voltage, it deteriorates the RF parameters. This paper proposes a remedy for this problem in the form of two short high-impedance transmission lines (SHITLs) which are included at both ends of the MEMS switch. The SHITLs are implemented through adoption of a discontinued CPW transmission line. With this implementation, the switch can be modelled as a T circuit, neutralizing a capacitance behavior of MEMS switch at the up state. The paper also proposes an optimised fabrication process to realize a flat and planar bridge for the suggested RF MEMS switch. The measurement recorded by SEM and AFM shows that the proposed method significantly improves the planarity of the membrane. The RF and mechanical parameters of the fabricated switch are evaluated by Vector Network Analyser and Laser Doppler Vibrometer. At the up state, the switch has a return loss less than -20 dB in the entire frequency band (C-K). The isolation at the down state is better than 10 dB for the lower frequencies and increases to values better than 18 dB for the higher frequencies. The measured pull-in voltage is almost 20 V and the mechanical resonance frequency is 164 kHz.

An AC MPPT with Active/Reactive Power Control Feature for Single-Stage Three-Phase Grid-Connected Photovoltaic VSIs

This article introduces a new AC MPPT (maximum power point tracking) controller for single-stage three-phase grid-connected photovoltaic (PV) voltage source inverters (VSIs) with active/reactive power control capability. Novelty lies in employing the theory of power transfer in short AC transmission lines to achieve MPPT, where two independent control variables exist: load angle and inverter modulation index. Accordingly, the proposed controller maximizes the capabilities of the single-stage VSI and enables it to control either/both active power or/and reactive power, besides achieving MPPT function. Such contribution opens up avenues in MPPTs world in terms of flexibility, fast performance, and low hardware count/cost. AC refers to Alternate Current since the MPPT is managed in AC terms. Theoretical framework of the proposed controller has been addressed. Moreover, the overall system is simulated in MATLAB (The MathWorks, Natick, Massachusetts, USA) environment, and results have been introduced. Design and implementation of proposed algorithms have been carried out using a fixed-point digital signal processor (DSP)TMS320F2812. Furthermore, a breadboard circuit is built up for experimentally investigating the controller's performance using 3-phase VSI that connects PV with the grid. In addition to that, a comprehensive discussion is conducted for demonstrating results. Moreover, a detailed comparison of proposed work with a number of previously published papers in literature is carried out and addressed in this manuscript. Results reveal that introduced controller achieves satisfactory performance.

Review on Reactive Power Compensation in Short Transmission Line

Review on Reactive Power Compensation in Short Transmission Line

Integrated On-Chip Solenoid Inductors With Nanogranular Magnetic Cores

On-chip integrated solenoid inductors with nanogranular FeCoTiO magnetic cores have been fabricated. Both single-layered and multilayered magnetic cores with different geometries were studied. An inductance of 14.2 nH was achieved when using a multilayered core structure and keeping the device area of 0.14 mm2. The inductance of the magnetic core inductor is $\sim 14$ times that of the air core inductor, and the quality factor is 7.5. The permeability trends calculated from inductance were compared with the permeability spectra of the patterned FeCoTiO films measured by an improved shorted microstrip transmission line perturbation method. Consistent results have been obtained after considering the demagnetization effect of the magnetic core with high permeability.