Commercial Electromagnetic Simulation Research Articles

S-Parameter Deembedding Algorithm and Its Application to Substrate Integrated Waveguide Lumped Circuit Model Extraction

In this paper, a unified method is introduced and formulated for deriving the equivalent circuit model of a guided wave structure as well as its characteristic impedance for any mode. This method is developed through the combination of a generalized multimode calibration and a full-wave simulation, and it is applicable to the fundamental mode as well as higher order modes. The method is verified for both TEM and non-TEM propagating modes and is applied to extract the characteristic impedance and circuit model of non-TEM guided-wave structures. This scheme allows for the effective use of a commercial electromagnetic field simulator in removing inherent numerical simulation noises or errors. Extracting circuit parameters through this technique for establishing equivalent circuit models can overcome the shortcomings encountered in the modeling of guided-wave eigenvalue problems as well as in the design of multimode structures.

Microwave characterization of normal and superconducting states of MOCVD made YBCO tapes

We have used a microwave, non-contact, non-destructive, dielectric resonator (DR) technique to characterize complex conductivity of different quality YBCO/Hastelloy tapes for the purpose of exploring such a technique as a potential quality control method for fabrication of YBCO tapes. The tapes were deposited at different temperatures on Hastelloy-supported oxide buffer layers using the MOCVD technique. The buffer stack consisted of aluminum oxide (Al2O3), yttrium oxide (Y2O3), and textured ion beam assisted deposition-MgO and LaMnO3 layers. Two dielectric resonators (DRs), the single post DR, consisting of high-permittivity barium zirconium titanate ceramic operating at 13 GHz in quasi-TE01δ mode, and the rod DR, consisting of rutile single crystal disk operating at 9.4 GHz in-TE011 mode, were designed to meet sensitivity requirements for characterization of conductivity of the superconductor at normal and superconducting states, respectively. For calculations of complex conductivity from experimental data of Q-factor and resonant frequency shift, a commercial electromagnetic simulator HFSS, based on finite elements analysis, was used. The theoretical Q-factor and resonant frequency on conductivity functions obtained from full wave numerical simulations of microwave fields were matched with the experimental data to determine conductivity of the YBCO tapes in both normal and superconducting states. In addition, for comparison purposes, 280 nm thick high-quality YBCO epitaxial film deposited on a dielectric substrate was also characterized, including frequency dependence of the complex conductivity. Discussion about feasibility of using DR microwave techniques as a quality control tool via measurements of conductivity versus temperature slope of the YBCO/Hastelloy tape in normal state is included. Also, microwave conductivity values of Hastelloy substrate as a function of temperature are reported.

A Rigorous Proof on the Radiation Resistance in Generalized PEEC Model

This paper develops a theory on the proof of the radiation resistance in frequency-domain partial element equivalent circuit (PEEC) model. Specifically, the total power dissipated on the imaginary part of the complex inductance and capacitance derived from the PEEC model is found to be the total radiated or scattered power when the structure is internally excited by independent sources, or externally by incident waves, respectively. Accordingly, the imaginary part of the complex inductance and capacitance represents a radiation resistance network of the structure. Numerical simulations based on PEEC and commercial electromagnetic simulation tool are presented for comparison, and some physical implications are discussed.

Numerical Method for Exposure Assessment of Wireless Power Transmission under Low-Frequency Band

In this paper, an effective numerical analysis method is proposed for calculating dosimetry of the wireless power transfer system operating low-frequency ranges. The finite-difference time-domain (FDTD) method is widely used to analyze bio-electromagnetic field problems, which require high resolution, such as a heterogeneous whole-body voxel human model. However, applying the standard method in the low-frequency band incurs an inordinate number of time steps. We overcome this problem by proposing a modified finite-difference time-domain method which utilizes a quasi-static approximation with the surface equivalence theorem. The analysis results of the simple model by using proposed method are in good agreement with those from a commercial electromagnetic simulator. A simulation of the induced electric fields in a human head voxel model exposed to a wireless power transmission system provides a realistic example of an application of the proposed method. The simulation results of the realistic human model with the proposed method are verified by comparing it with the conventional FDTD method.

TEM-TE 11 high power microwave mode convertor with metallic metamaterial

A metallic metamaterial high power microwave (HPM) mode converter which converts cylindrical TEM mode to TE11 mode is presented. Metallic sector grid elements are periodically arranged both in the azimuthal and longitudinal directions to gain high refractive index to act as phase shifter in the convertor. The mode converter is simulated by 3D commercial electromagnetic simulation software CST Microwave Studio. Simulation results show that the converter has high conversion efficiency with a relative bandwidth of about 4%. The radiation antenna with a metamaterial mode converter is simulated. The mode convertor is simulated combined with an L-band MILO tube using a particle-in-cell software, and a TE11 mode HPM is obtained in the outlet of the tube.

Physics‐based RF/microwave characterization of wave interactions within electrical connectors with partial insertion faults

AbstractElectrical failures in avionics systems may result from connector faults. If fault precursors are not detected in advance, they may lead to hard failures such as open and short circuits that could ultimately result in fire or loss of flight critical systems. Therefore, It is crucial to detect, locate, and characterize fault precursors for timely preventive maintenance and mitigation before hard failures occur. In this paper, a physics‐based connector model consisting of multiple coaxial line sections with different characteristic impedances and lengths is proposed. Method of Moments (MoM) analyses were performed using commercial electromagnetic simulation software, FEKO, for transverse electric and magnetic (TEM) wave propagation through a connector. The physical parameters of the connector were optimized to match the measured S parameters for multiple insertion depths. The proposed models represent the connector for multiple insertion depths by varying only two length parameters at a time while other parameters are fixed. Insertion depth‐dependent resonant frequency shifts observed during measurement are also captured by the model over the full range of fully inserted to barely touching contacts. Hence, the models provide accurate representations of the connector and properly detect precursors to partial insertion faults.

Computational human model VHP-FEMALE derived from datasets of the national library of medicine.

Simulation of the electromagnetic response of the human body relies upon efficient computational models. The objective of this paper is to describe a new platform-independent and computationally-efficient full-body electromagnetic model, the Visible Human Project® (VHP)-Female v.3.0 and to outline its distinct features. We also report model performance results using two leading commercial electromagnetic antenna simulation packages: ANSYS HFSS and CST MICROWAVE STUDIO®.

Wideband Modeling and Characterization of Differential Through-Silicon Vias for 3-D ICs

This paper presents the wideband modeling and analysis of differential through-silicon vias (D-TSVs) in 3-D ICs. An equivalent-circuit model of the ground–signal–signal–ground-type D-TSVs is given and validated against a commercial full-wave electromagnetic simulation tool. The common- and differential-mode impedances are extracted using the partial-element equivalent-circuit method, while the admittances are calculated analytically, with the MOS effects considered and treated appropriately. The circuit model can also be used for studying the differential annular TSVs (ATSVs). It is shown that the ATSVs are more suitable for transmitting differential signals in comparison with the cylindrical TSVs. Based on the equivalent-circuit model, the characteristic impedances and the forward transmission coefficients of the D-TSVs made of Cu and carbon nanotubes are characterized and compared under different settings of frequencies and temperatures.

Electromagnetic Simulation of Influence of Metamaterial for Magnetic Resonance Imaging at 3T.

This paper presents an approach to investigate the influence of metamaterial to radio-frequency (RF) magnetic field in magnetic resonance imaging (MRI) at 3T. The variety of magnetic fields of RF receiving coil was calculated using the commercial electromagnetic simulation software (CST). The simulation results demonstrate that the transmitting and receiving magnetic field (B1+ and B1-) can be enhanced when the metamaterial is inserted into the RF coil, suggesting that the metamaterial has potential in MRI applications at 3T.

Metal mesh filters based on Ti, ITO and Cu thin films for terahertz waves

In this study, we have investigated the spectral performance of resonant terahertz (THz) bandpass filters which were produced from thin films with a metal-mesh shape. The aforementioned filters were fabricated from titanium, copper and indium tin oxide thin films on fused silica substrates by UV lithography with an array of cross-shaped apertures. Since the mesh period, cross-arm length and its width specify the spectral characteristics of the filters, we were able to reveal the performance of these filters experimentally using both a THz time domain spectrometer and a Fourier transform infrared spectrometer. A commercial electromagnetic simulation software, CST microwave studio, was used to verify the experimental data. The transmission of the filters are in the range 20–55 % at their relevant center frequencies. To our knowledge this study is the first to show that fabricated patterns based on ITO thin films can be used to filter THz radiation.

Vertical microstrip-to-microstrip transition through the highpass-filter topology for ultra-wideband (UWB) applications

A vertical microstrip-to-microstrip transition with ultra-wideband (UWB) filtering response is proposed and constituted based on the highpass or UWB bandpass filtering structure with the composite series or shunt stubs. By centrally feeding a slotline resonator on the common ground, two microstrip feed lines in the top and bottom layers are interconnected to make up a three-pole signal transmission network. Based on the ideal transmission-line model, this proposed transition is at first synthesised with the Chebyshev equal-ripple frequency responses. Next, the transition is formed on a two-layered dielectric substrate and its frequency response is simulated via the commercial electromagnetic simulator to confirm the predicted three-pole transmission behaviour from the synthesis approach. Finally, a prototype vertical transition centred at 6.0 GHz is fabricated and measured, showing the good agreement among predicted, simulated and measured results over a wide frequency band.

A Design of Vehicular GPS and LTE Antenna Considering Vehicular Body Effects

In this paper, a vehicular antenna design scheme considering the vehicular body effects is proposed. A wire antenna for GPS and LTE is implemented on the plastic plate, then it is mounted on the front glass. The outputs are commonly used to share the feed. It is necessary for GPS to increase the right hand circularly polarization (RHCP) gain near the zenith and to reduce the axis ratio while for LTE to increase the horizontal and vertical polarization (HP and VP) gain in the horizontal plane. Also for LTE, multiband characteristics are required. In order to achieve the specified performance, the antenna shape is optimized by Parato genetic algorithm (PGA). When the antenna is mounted on the body, the performance is seriously changed. To evaluate performance of the antenna mounted on the body with a complex shape, a commercial electromagnetic simulator (Ansoft HFSS) is used. To apply electromagnetic results output by HFSS to PGA algorithm operating on the MATLAB, MATLAB to HFSS linking program via Visual BASIC (VB) script was used. It is difficult to carry out the electromagnetic analysis with the whole body because of limitations of the calculating load and memory size. To overcome the limitation, we consider only a predominant part where it has an influence on the performance. It is presented that degradations caused by the body are improved through a series of optimization stages. The simulation results obtained clearly show that it is well optimized at 1.575 for GPS and 766.5 MHz and 2.135 GHz for LTE, respectively.

OPTIMIZED DESIGN OF W-BAND QUASI-OPTICAL LENS BY USING OPTICAL SIMULATOR AND NUMERICAL ANALYSIS

A large aperture quasi-optical dielectric lens antenna for passive imaging at W-band frequency is proposed. The lens is designed to obtain best resolution at a designate distance of 3.5 m from it. The lens has biconvex aspheric surface to achieve low aberration. The initial parameters of the optical path are obtained with Gaussian beam method, and then the optical simulator ZEMAX is applied to optimize the shape of the lens which improves design efficiency greatly. A hybrid numerical method is used to analyze near field distribution of the lens, and the final design of the lens is evaluated and determined by the results. The method is the combining of ANSOFT HFSS software, ray tracing method and integration algorithm based on Huygens' Principle. It is feasible and efficient for the analysis of various lens antennas, such as large aperture lens antennas which are difficult to be simulated by commercial electromagnetic simulation software. The lens is fabricated with HDPE. Experimental results show that its 3 dB beam size is 29 mm at distance of 3.5 m, which is in good agreement with theoretical calculation. The measured patterns on the image plane show that the lens has 0.3 dB decrease of field intensity in field view of 690 mm. Imaging result shows that the lens is a good candidate for focal plane imaging.

A Modeling Method for Small Packing Particles in Electromagnetic Simulation

A modeling method for small packing particles is proposed in this paper, especially for the application of the electromagnetic simulation. This method is able to model random distributed and mutual-contacted packing particles efficiently and accurately. This modeling method is faster than a commonly used software, especially for large number of particles. The accuracy of this modeling method is validated by experiments of packing density and effective permittivity. The established model can be easily imported into commercial electromagnetic simulation software.

Antenna gain and link budget for waves carrying orbital angular momentum

AbstractThis paper addresses the RF link budget of a communication system using unusual waves carrying an orbital angular momentum (OAM) in order to clearly analyze the fundamental changes for telecommunication applications. The study is based on a typical configuration using circular array antennas to transmit and receive OAM waves. For any value of the OAM mode order, an original asymptotic formulation of the link budget is proposed in which equivalent antenna gains and free‐space losses appear. The formulations are then validated with the results of a commercial electromagnetic simulation software. By this way, we also show how our formula can help to design a system capable of superimposingseveral channels on the same bandwidth and the same polarization, based on the orthogonality of the OAM. Additional losses due to the use of this degree of freedom are notably clearly calculated to quantify the benefit and drawback according to the case.

Estimation of the Bandwidth of Acceptable Crosstalk of Parallel Coupled Ring Resonator Add/Drop Filters

In this paper, a parallel coupled optical ring resonator filter is studied and the transfer function is derived using the signal flow graph (SFG) approach to identify the filter performance in terms of crosstalk suppression bandwidth and signal integrity. This paper proposes the use of the SFG (Mason's rule) approach to determine the filtering characteristics of parallel coupled ring resonators. A commercial electromagnetic simulator is used to validate the analytical model. The modeling of the parallel coupled ring resonator covers the analysis of the out-of-band rejection ratio, crosstalk suppression, loss effect, and the effect of coupling coefficients on the crosstalk bandwidth. The good agreement between analytical model results and simulation results suggests that using the derived analytical model provides an accurate starting point for design and analysis and, in doing this, provides a better insight into the signal integrity performance of the filter.

Metamaterial-based antennas for integration in UWB transceivers and portable microwave handsets

Two planar antennas based on metamaterial unit-cells are designed, fabricated, and tested. The unit-cell configuration consists of H-shaped or T-shaped slits and a grounded spiral. The slits essentially behave as series left-handed capacitance and the spiral as a shunt left-handed inductance. The unit-cell was modeled and optimized using commercial 3D full-wave electromagnetic simulation tools. Both antennas employ two unit-cells, which are constructed on the Rogers RO4003 substrate with thickness of 0.8 mm and er = 3.38. The size of H-shaped and T-shaped unit cell antennas are 0.06λ0 × 0.02λ0 × 0.003λ0 and 0.05λ0 × 0.02λ0 × 0.002λ0, respectively, where λ0 is the free-space wavelength. The measurements confirm the H-shaped and T-shaped unit-cell antennas operate across 1.2-6.7 GHz and 1.1-6.85 GHz, respectively, for voltage standing wave ratio VSWR < 2, which correspond to fractional bandwidth of ~140% and ~ 145%, respectively. The H-shaped unit-cell antenna has gain and efficiency of 2-6.8 dBi and 50-86%, respectively, over its operational range. The T-shaped unit-cell antenna exhibits gain and efficiency of 2-7.1 dBi and 48-91%, respectively. The proposed antennas have specifications applicable for integration in UWB wireless communication systems and microwave portable devices. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:88-96, 2016.

Application of the Array Scanning Method in Periodic Structures with Large Periods

The problem of aperiodic excitation of periodic structures with periods larger than a half-wavelength is revisited. A large number of antennas and other electromagnetic wave propagation problems fall within this category. Because of overlapping branch cuts, the conventional path deformation techniques employed in application of the array scanning method for this type of problem fail when the period is larger than a half-wavelength. A new method based on the subdivision of the integration path and using the double exponential quadrature formula is introduced to alleviate this problem and apply the array scanning method to structures with an arbitrary spatial period. To demonstrate the application of the new method and to validate the results, reflection and transmission coefficients of a frequency selective surface excited by a single electric dipole are calculated. Near fields of the frequency selective surface with aperiodic excitation are obtained and compared with those of a commercial electromagnetic simulator. The proposed method, similar to the path deformation technique, which is applicable to small periods, shows considerable advantage in terms of computational time and memory requirement.

Modeling and Parameter Extraction of Coplanar Symmetrical Meander Lines

In this paper, a coplanar symmetrical meander line structure is presented, and an equivalent circuit model is proposed to allow estimation of its electrical characteristics based on numerical modeling. The parasitic couplings in the proposed structure are considerably different from those of a simple meander line with a ground structure below it. Analysis and derivation of inductive and capacitive couplings and of resistance in the effective frequency band are addressed in detail, and the effects of geometrical parameters on the electrical characteristics are also demonstrated. The validity of the proposed equivalent circuit model is verified by both commercial electromagnetic simulator and measurement of the scattering parameters in the frequency domain, as well as of the reflected and transmitted waveforms in the time domain. Because the proposed model is easily coded, and takes little time to compute the parameters, it is very useful in the design of inductance and capacitance in circuits on substrate, which can be used for the design of time-delay elements and stop band filters in power delivery lines.

Miniaturized C-Band SIW Filters Using High-Permittivity Ceramic Substrates

This paper introduces an effective way to build efficient miniature C-band filters using high-permittivity ceramics. The objective was to evaluate the feasibility of such filters using commercial electromagnetic simulators and a conventional fabrication process. For the demonstration, the substrate integrated waveguide (SIW) technology was chosen. Compared with planar solutions, this configuration offers good quality factors and good electrical performances as a consequence. However, its dimensions are large, leading to unacceptably large footprints for many applications. The solution proposed in this paper is based on a ceramic substrate with a permittivity of 90, which allowed us to work with shorter wavelengths. In comparison with a standard alumina substrate (permittivity $\varepsilon _{r}= 9.9$ ), this approach makes it possible to reduce the footprint up to nine times. Two prototypes were realized on a Trans-Tech ceramic substrate ( ${\rm thickness}=635~\mu \text{m}$ , $\varepsilon _{r} = 90$ , and tan $\delta = 9\cdot 10^{-4})$ . The first prototype is a folded sixth-order SIW filter including a cross coupling combining coplanar waveguide probes and a thin microstrip line on an InterVia substrate. The second one is a folded eighth-order SIW filter without cross couplings. Here, we compare the sixth-order prototype with an identical one built on alumina. The eighth-order filter, which had no alumina counterpart, is a potentially useful alternative for situations where complex technological steps must be avoided.