SPICE-compatible Equivalent Circuit Research Articles

SPICE-Compatible Equivalent Circuit Models for Accurate Time-Domain Simulations of Passive Photonic Integrated Circuits

Passive photonic integrated circuits (PICs) can be easily characterized in the frequency-domain, but their accurate time-domain performance evaluation is a hurdle for system-level designers, especially when dealing with resonant circuits having highly dispersive behavior, such as ring resonators. In this paper, a new equivalent circuit modeling and simulation approach is proposed, based on the Complex Vector Fitting algorithm, able to perform accurate and robust time-domain simulations of passive PICs directly in standard SPICE simulators. The proposed modeling technique starts from scattering parameters of passive PICs, and is able to capture linear and high order dispersion, backscattering, and wavelength dependent effects. Considering the different nature of optical and electronic signals, a novel concept of equivalent voltage and current for optical waveguides is proposed to simplify the optical to electronic ports conversion and to make it possible to connect and terminate the equivalent circuit models as needed in SPICE simulators, natively supporting bidirectional signal propagation in a waveguide. This work provides a precise and reliable solution to evaluate time-domain characteristics of passive PICs and to access any internal nodes within a circuit, such as the signals inside a ring resonator. Three examples of time-domain simulations of passive PICs in commercial SPICE simulators are presented to demonstrate the flexibility and advantages of the proposed technique.

Incorporating the Dynamic Threshold Voltage Into the SPICE Model of Schottky-Type p-GaN Gate Power HEMTs

The threshold voltage (VTH) of an enhancement-mode Schottky-type p-GaN gate high-electron-mobility transistor (HEMT) is found to have a special dependence on the drain bias. The device commonly requires higher gate voltage to switch on the transistor from a high-drain-voltage off-state than what is expected from the static device characteristics. The reason behind the dynamic VTH has been proved to be the floating p-GaN layer, where charges could be stored and further influence VTH under different drain bias. In this article, a SPICE-compatible equivalent circuit model is presented according to the structure of Schottky-type p-GaN gate HEMTs. It features a floating node to imitate the charge storage process within the gate stack. Compared to conventional models, the proposed model could accurately predict the dynamic VTH characteristics and switching behaviors of power electronics circuits, where Schottky-type p-GaN gate HEMTs are deployed as power transistors. The phenomena related to the dynamic VTH, including the disappearance of Miller plateau, the overestimated false-turn-on problem, and the higher reverse conduction loss are evaluated with a half-bridge circuit and the merits of the proposed model are verified.

Control Device Thermal Modeling in MRI Receive Coil Q-Spoiling Circuits

Q-spoiling circuits for detuning receive coils during high-power magnetic resonance imaging (MRI) slice-select pulses protect both sensitive electronics as well as the patient from undesired high energy signals and associated heating. These circuits have traditionally used PIN diodes and, more recently, field effect transistors to switch in small values of inductance to shift the coil resonance away from the Larmor frequency. These semiconductor devices can see the full radio frequency (RF) power during operation, and will exhibit significant heating, potentially leading to device failure. Even if the device does not reach a destructive heating level, the resistance of the device can increase and effectively degrade the level of blocking in the RF coil. A useful tool for MRI circuit designers would be a thermal model that predicts this change in resistance, and hence degradation in MRI coil blocking, as device temperature rises. This paper presents a method for modeling thermal effects in MRI Q-spoiling control devices. A PIN diode resistance–temperature model is reviewed, and two approaches for field effect transistors that model the temperature rise and subsequent device resistance variation with temperature using SPICE-compatible equivalent circuit elements are covered. Experimental results are presented that validate the form of the models and show that increased device resistance due to temperature rise will degrade MRI blocking by several decibels. The ability to model the control device's thermal characteristics will lead to improved understanding of circuit operation, aid in the selection of the control device for the specific application, and will lead to more reliable MRI instrumentation.

Broadband Equivalent-Circuit Model for Uniform Multiconductor Transmission Lines

A passive and inherently stable Foster equivalent-circuit representation for uniform multiconductor transmission lines for moderate losses is presented. The method is based on an analytic eigenfunction expansion. An efficient model-order reduction is achieved by appropriate inductances that are extracted by a quasistatic approach. The order number of the truncated modal circuit is simply estimated, according to the required signal bandwidth. The accuracy and versatility of the suggested SPICE-compatible equivalent circuit is demonstrated by examples in frequency and time domain, including nonlinear terminations.

A Foster-Type Field-to-Transmission Line Coupling Model for Broadband Simulation

A passive and inherently stable multiport equivalent circuit for lossy transmission lines is presented. The convergence of the infinite modal representation is accelerated by appropriate inductances, for which an exact closed-form expression is developed. The order number of the truncated modal circuit is estimated by a simple relation, according to the required signal bandwidth. The coupling of arbitrary external electromagnetic fields is incorporated by a limited number of corresponding modal sources. The accuracy and versatility of the suggested SPICE-compatible equivalent circuit is demonstrated by examples in frequency and time-domain, including nonlinear terminations.

An Equation-Based Circuit Model and Its Generation Tool for 3-D IC Power Delivery Networks With an Emphasis on Coupling Effect

In this paper, a methodology to characterize the electrical behaviors of power delivery networks (PDNs) in 3-D integrated circuits is presented. An automation tool is developed to effectively construct SPICE compatible equivalent circuit models of target PDNs. The core of the tool consists of three equation-based algorithms, which not only model the planar PDN and through-silicon vias in detail, but also the interactions between them through the silicon surface. Simulation results from the proposed SPICE model are in close agreement with the ones obtained from the full-wave simulator up to 40 GHz with more than 100 times speedup.

Modeling of the Electrical Fast Transient/Burst Generator and the Standard Injection Clamp

This paper presents an accurate and systematic method to simulate the interference imposed on the input/output (I/O) ports of electronic equipment under the electrical fast transients/burst (EFT/B) test. The equivalent circuit of the EFT/B generator and the coupling clamp are modeled respectively. Firstly, a transfer function (TF) of the EFT pulse-forming network is constructed with the latent parameters based on circuit theory. In the TF, two negative real parameters characterize the non-oscillation process of the network while one complex conjugate pair characterizes the damping-oscillation process. The TF of the pulse-forming network is therefore synthesized in the equivalent circuit of the EFT/B generator. Secondly, the standard coupling clamp is modeled based on the scatter (S) parameter obtained by using a vector network analyzer. By applying the vector fitting method during the rational function approximation, a macromodel of the coupling clamp can be obtained and converted to a Spice compatible equivalent circuit. Based on the aforementioned procedures, the interference imposed on the I/O ports can be simulated. The modeling methods are validated experimentally, where the interference in differential mode and common mode is evaluated respectively.

Rational modeling of on-chip inductor by vector fitting

This paper proposes a new methodology of modeling on-chip inductor. Rational polynomial is used to approximate the performance curve of on-chip inductor via vector fitting. This procedure will generate highly accurate model with proper poles location and frequency-independent SPICE-compatible equivalent circuit, which can be used in simulator to obtain time-domain waveform.

On-Chip Coupled Transmission Line Modeling for Millimeter-Wave Applications Using Four-Port Measurements

Transmission lines are fundamental elements in millimeter-wave circuits. In this paper, on-chip coupled transmission lines, fabricated in a commercial 0.18 ?m complementary metal-oxide semiconductor process, have been modeled, based on measured 50 GHz four-port scattering-parameters. The two-port open-short deembedding technique and thru deembedding method were successfully extended and applied to the four-port structures presented here. The accuracy of the deembedding techniques was verified by full-wave electromagnetic simulation. Based on the deembedded S-parameters, a SPICE-compatible equivalent circuit model of on-chip coupled transmission lines was extracted. Simulation and measurement results agree well over the entire frequency band from 100 MHz up to 50 GHz.

Delay-Based Macromodeling of Long Interconnects From Frequency-Domain Terminal Responses

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> We present a robust and efficient scheme for the generation of delay-based macromodels from frequency-domain tabulated responses. These responses can come from both simulation or direct measurement. The main algorithm is based on an iterative weighted least-squares process for the identification of delayed rational approximations. In case that pole relocation is performed during the iterations, the scheme can be interpreted as a generalization of the well-known vector fitting algorithm to delayed systems. Therefore, we denote this algorithm as delayed vector fitting (DVF). In case no pole relocation is performed, the scheme generalizes the so-called Sanathanan–Koerner iteration, calling for the denomination of delayed Sanathanan–Koerner algorithm. These techniques produce compact macromodels that are readily synthesized in SPICE-compatible equivalent circuits including delayed sources or ideal transmission line elements. These macromodels outperform classical rational macromodels in terms of simulation time. Several examples illustrate the advantages of proposed methodology. </para>

A SPICE COMPATIBLE MODEL OF ON-WAFER COUPLED INTERCONNECTS FOR CMOS RFICs

This paper investigates the properties of the on-wafer coupled interconnects built in a 0.18m CMOS technology for RF applications. A SPICE compatible equivalent circuit model is developed. The proposed model is an extension of a 2-ƒ equivalent circuit model for single-line interconnects by adding two coupling components. The model parameters are extracted from four-port S-parameter simulation results through a calibrated electromagnetic (EM) simulator, i.e., HFSS. The accuracy of the model is validated from 500MHz to 20GHz.

A Low-Frequency Accurate Cavity Model for Transient Analysis of Power-Ground Structures

With increased operating frequencies and circuit component density, signal and power integrity problems caused by voltage bounces have become more important for high-speed digital systems. This paper presents a systematic macromodeling of power-bus structures based on the cavity model: first, more accurate models are used to describe conductor and dielectric losses, thus improving accuracy at low frequencies; second, a rational model of the overall power/ground structure in the Laplace domain is presented, and third, the rational macromodel is used to identify the dominant poles, and a simplified SPICE-compatible equivalent circuit is synthesized by using only the selected poles. The numerical results confirm the correctness and effectiveness of the method.

Analysis of Thermoelectric Coolers by a Spice-Compatible Equivalent-Circuit Model

The objective of this work was to develop a PSPICE-compatible equivalent circuit of a thermoelectric cooler (TEC). Equivalent circuits are convenient tools for power electronics engineers since they help in presenting a problem in electronic circuit terms and can assist in the design of power stages and the control circuitry and algorithms. A methodology is developed for extracting the parameters of the proposed model from manufacturers' data of TECs. The present model is compatible with PSPICE or other electronic circuit simulators. An important feature of the model is its ability to generate small-signal transfer functions that can be used to design feedback networks for temperature-control applications. Several examples of successful utilization of the model are presented. Data of many different manufacturers were examined and the model parameters were extracted. In all cases, the model was found to reproduce accurately the performance of commercial TECs. The accuracy of the model was also verified by experiments.

Physically consistent transmission line models for high-speed interconnects in lossy dielectrics

The development of a physically consistent multiconductor transmission line model for high-speed interconnects in lossy, dispersive dielectrics is presented. Based on this model, a methodology is presented which constructs SPICE-compatible equivalent circuits that take into account dielectric loss and dispersion. Simulations using wideband measurement data of alumina demonstrate the effect of the Debye based permittivity model.

Envelope simulation by SPICE-compatible models of linear electric circuits driven by modulated signals

SPICE-compatible equivalent circuits were developed to facilitate the analysis and envelope simulation of electric circuits driven by modulated signals. The circuits are based on a novel complex phasor-domain transformation. The proposed method facilitates simulation of any general linear circuit driven by a modulated signal such as amplitude modulation, frequency modulation, or phase modulation. Simulation time by the proposed envelope simulation is much faster than the full cycle-by-cycle simulation of the original circuit and excitation.

Envelope simulation by SPICE-compatible models of electric circuits driven by modulated signals

SPICE-compatible equivalent circuits were developed to facilitate the analysis and envelope simulation of electric circuits driven by modulated signals. The circuits are based on a novel complex phasor domain transformation. The proposed method facilitates fast simulation of any general linear circuit driven by a modulated signal, such as amplitude, frequency, or phase modulation.

Modeling the high-frequency behavior of a fluorescent lamp: a comment on "a PSpice circuit model for low-pressure gaseous discharge lamps operating at high frequency"

The shortcomings of the model presented by Wu et al. (see ibid., vol. 44, p. 428-31, 1997) are pointed out and an improved SPICE-compatible equivalent circuit that dodges the limitations is presented. It is shown that the proposed model is useful in emulating the fluorescent lamp response to a change in excitation frequency.