Introduction to RF simulation and its application

Radio-frequency (RF) circuits exhibit several distinguishing characteristics that make them difficult to simulate using traditional SPICE transient analysis. The various extensions to the harmonic balance and shooting method simulation algorithms are able to exploit these characteristics to provide rapid and accurate simulation for these circuits. This paper is an introduction to RF simulation methods and how they are applied to make common RF measurements. It describes the unique characteristics of RF circuits, the methods developed to simulate these circuits, and the application of these methods     

Fast periodic steady-state analysis for large-signal electronic circuits

It is shown that current computer-aided circuit analysis programs that are capable of the transient analysis of nonlinear circuits can be modified to include the determination of the periodic steady-state response of large-signal electronic circuits such as class C amplifiers, frequency multipliers, parametric circuits, and oscillators. With this modification only a portion of the transient response is computed, then a Newton iterative technique is used to find the periodic state of the circuit from which the periodic response can be found by a numerical integration over one period. This technique is especially valuable for analyzing high Q circuits and for design purposes where fast analysis is essential.     

Computer-aided design considerations for mixed-signal coupling inRF integrated circuits

This paper reviews computer-aided design techniques to address mixed-signal coupling in integrated circuits, particularly wireless RF circuits. Mixed-signal coupling through the chip interconnects, substrate, and package is detrimental to wireless circuit performance as it can swamp out the small received signal prior to amplification or during the mixing process. Specialized simulation techniques for the analysis of periodic circuits in conjunction with semi-analytical methods for chip substrate modeling help analyze the impart of mixed-signal coupling mechanisms on such integrated circuits. Application of these computer-aided design techniques to real-life problems is illustrated with the help of a design example. Design techniques to mitigate mixed-signal coupling can be determined with the help of these modeling and analysis methods     

A circuit reduction technique for finding the steady-state solutionof nonlinear circuits

Computing the steady-state response of large nonlinear circuits is becoming a key simulation requirement due to the rapid market growth of RF silicon integrated circuits. In this paper, we describe a nonlinear circuit reduction algorithm for finding the steady-state response. The proposed algorithm uses a congruent transformation-based technique to reduce the harmonic-balance equations into a much smaller set of equations. The main feature of the reduced circuit is that it shares with the original one a certain number of the derivatives with respect to the RF input power, steady-state analysis is then carried out on the reduced circuit instead of the original circuit     

Tools for contactless testing and simulation of CMOS circuits

Short channel effects in MOSFETs are responsible for time-dependent hot-carrier luminescence, synchronous with the switching transitions in CMOS circuits. We propose an optical non-invasive inspection technique for high-speed signals, based on a high sensitivity solid-state photodetector with sharp time resolution. This tool is able to probe the fast electrical waveforms propagating through ULSI circuits without electrically loading the circuit under test. The measured time resolution of 50 ps allows an equivalent analog bandwidth of about 20 GHz. From the experimental results and the luminescence characterization of single transistors, we propose a SPICE model able to foresee the photoemission in complex ULSI circuits, down to transistor level. The optical testing equipment and the SPICE modeling are valuable tools for simulation, characterization and testing of fast ULSI circuits.     

基于MOSFET PDE模型的射频自治电路周期稳态算法研究

本文研究了基于MOSFET PDE模型的射频自治电路周期稳态求解算法.采用该算法仿真典型的Colpitts振荡器电路,得到电压波形和工业界公认标准器件仿真器MEDICI瞬态模拟得到电压波形具有很好的一致性.     

CAD tools for efficient RF/microwave transistor modeling and circuit design

In today’s radiofrequency and microwave communication circuits, there is an ever-increasing demand for higher integration and miniaturization. This trend leads to massive computational tasks during simulation, optimization and statistical analyses, requiring robust modeling tools so that the whole process can be achieved reliably. In this paper, the authors proposed frequency- and time-domain computer-aided design tools that can characterize RF/microwave field effect and heterojunction bipolar transistors and efficiently predict a circuit performance. The proposed tools are demonstrated through examples.     

Time-Domain Simulation of Nonlinear Circuits Through Implicit Runge–Kutta Methods

This paper presents a novel approach to the accurate time-domain simulation of nonlinear circuits that employs a class of high-order implicit Runge-Kutta (RK) formulas. The RK methods that are here considered are selected among the wide family of known RK methods as being particularly suited to the task of analog simulation. The properties of stability and accuracy of these RK methods are briefly reviewed while the implementation in the flow of an analog simulator is described in detail. When compared to standard multistep methods, the considered RK techniques reveal to be much more reliable and thus particularly suited to the analysis of those circuits, such as circuits for RF applications or sharply nonlinear switched circuits, that are critical for conventional integration methods     

Dynamic Threshold Delay Characterization Model for Improved Static Timing Analysis

Transistors within a gate take a finite amount of time to switch and hence there is always a propagation delay associated with it. These delays are evaluated by standard cell characterization techniques using EDA tools. However, these standard measurement methods tend to fail when simulating the design with practical values of slope and load and gives rise to the problem of negative or non-monotonic delays. Negative/non-monotonic delays lead to false positives during static timing analysis, synthesis and simulation of circuits and are undesirable. Hence, there is a need to implement new methods for characterization of propagation delay that will lead to more realistic monotonic delay values, ultimately achieving early timing closures. One such method of delay measurement based on actual switching thresholds has been proposed in this work.     

Steady-state analysis of nonlinear circuits with periodic inputs

In the computer-aided analysis of nonlinear circuits with periodic inputs and a stable periodic response the steady-state periodic response is found for a given initial state by simply integrating the system equations until the response becomes periodic. In lightly damped systems this integration could extend over many periods making the computation costly. In this paper a Newton algorithm is defined which converges to the steady-state response rapidly. The algorithm is applied to several nonlinear circuits. The results show a considerable reduction in the amount of time necessary to compute the steady-state response. In addition, the initial iterates give information on the transient response of the system.     

Microwave Bandstop Filters Using Novel Artificial Periodic Substrate Electromagnetic Band Gap Structures

Novel microwave and millimeterwave (mm-wave) bandstop filters using artificial periodic substrate electromagnetic bandgap (EBG) are investigated in this paper. Three types of microstrip structures using periodically modified trace width, patterned dielectric substrate, and periodically modified ground plane are treated, respectively. By periodically modifying either the width of the conductor trace, the substrate height, or the dielectric constant of a standard microstrip transmission line, it has been possible to design microwave bandstop filter functions with wide stopband characteristics and reduced size, compared to conventional microwave/RF filter structures. Commercial electronic design automation (EDA) and computational electromagnetic tools such as Agilent's advanced design system (ADS) and CST Microwave Studio are used in the design and simulations of these filter structures. The effects of the physical parameters of the structures on the filter characteristic are studied. The design procedure and simulation results are described and possible applications of these filter structures are discussed in this paper. A particularly wide stopband is achieved by the circuits presented in this paper, which use only a few cell elements. A significant performance improvement of microstrip patch antenna has been observed by implementing one of the presented EBG periodic substrate structures.      

A time-domain approach to simulation and characterization of RF HBT two-tone intermodulation distortion

In this paper, we evaluate the two-tone intermodulation distortion for heterojunction bipolar transistors (HBTs) operated at RF. We directly solve the nonlinear differential equations of the HBT large-signal model in time domain by employing the waveform-relaxation and monotone-iterative methods. Based on time-domain results, sinusoidal waveform outputs are transformed into the frequency domain with the fast Fourier transform. Furthermore, the output third-order intercept-point values of the HBT are computed with the spectra. Results for a fabricated InGaP HBT under different testing conditions are reported and compared among the HSPICE results, the results with harmonic balance methodology, and the measured data. Comparisons among these results show that our method demonstrates its superiority over the conventional approaches. This characterization alternative has allowed us to study RF device properties, perform thermal consumption and sensitivity analysis, and extract model parameters.     

Symbolic Steady-State Analysis for Strongly Nonlinear Circuits and Systems

A symbolic method for steady-state analysis of nonlinear circuits and systems is presented. This method is based on the principle of the Equivalent Small Parameter method (the ESP method), which is an improved perturbation technique combined with the harmonic balance method. Using this method, a set of high-order nonlinear differential equations can be solved and the symbolic expressions of the steady-state periodic solutions for the required variables can be obtained. Two examples are given and show that the method is general and can be used for both weakly and strongly nonlinear circuits, and time-variant nonlinear circuits such as switching mode circuits.     

Compact non-binary fast adders using single-electron devices

This paper proposes compact adders that are based on non-binary redundant number systems and single-electron (SE) devices. The adders use the number of single electrons to represent discrete multiple-valued logic state and manipulate single electrons to perform arithmetic operations. These adders have fast speed and are referred as fast adders. We develop a family of SE transfer circuits based on MOSFET-based SE turnstile. The fast adder circuit can be easily designed by directly mapping the graphical counter tree diagram (CTD) representation of the addition algorithm to SE devices and circuits. We propose two design approaches to implement fast adders using SE transfer circuits: the threshold approach and the periodic approach. The periodic approach uses the voltage-controlled single-electron transfer characteristics to efficiently achieve periodic arithmetic functions. We use HSPICE simulator to verify fast adders operations. The speeds of the proposed adders are fast. The numbers of transistors of the adders are much smaller than conventional approaches. The power dissipations are much lower than CMOS and multiple-valued current-mode fast adders.     

TNPT-an efficient method to simulate forced nonlinear RF networks in time domain

A new method to simulate forced nonlinear RF networks in time domain is introduced. This method is a generalization of the well-known steady-state algorithm of Trick and Aprille (1972). The proposed method allows one to calculate all time solutions until steady-state is reached similar to transient simulation (TR). It compares with steady-state like TR simulation with DC, and can therefore be considered to be a transient simulation of nonlinear periodic transients (TNPT).     

Improving Design and Fault Detection in Linear and Nonlinear High Frequency Circuits by Performing a Sensitivity Based Analysis

The rapid growth of wirelesscommunication has led to an increasing demand forreliable and high performance RF products. Oneway of achieving high reliability andperformances is having an efficient testprocedure. Considering the complexity of analogtesting and the high frequency constraints,testing RF circuits introduces a new challenge tothe test community. In this paper, a test methodfor RF circuits is presented. This test methoddivides RF circuits between linear and nonlinearcircuits. It helps perform a quick and efficienttest with a limited number of test vectors. Byusing this method the design engineer candetermine parameters influencing the circuitperformances and the best topology that can beused to improve these performances. On the otherhand, it helps a test engineer to plan his teststrategy and to predict which elements can beisolated by a given test set.     

A Versatile Time-Domain Approach to Simulate Oscillators in RF Circuits

This paper presents a versatile simulation technique for the time-domain analysis of RF oscillators. The method blends the superior accuracy and robustness of implicit Runge–Kutta integration formulas with the high efficiency of a particular envelope-following technique. The method can be applied to study both transient and steady-state responses of autonomous and nonautonomous circuits and can also be applied to the case of harsh nonlinear oscillator topologies.      

Computer-aided design of analog and mixed-signal integratedcircuits

This survey presents an overview of recent advances in the state of the art for computer-aided design (CAD) tools for analog and mixed-signal integrated circuits (ICs). Analog blocks typically constitute only a small fraction of the components on mixed-signal ICs and emerging systems-on-a-chip (SoC) designs. But due to the increasing levels of integration available in silicon technology and the growing requirement for digital systems to communicate with the continuous-valued external world, there is a growing need for CAD tools that increase the design productivity and improve the quality of analog integrated circuits. This paper describes the motivation and evolution of these tools and outlines progress on the various design problems involved: simulation and modeling, symbolic analysis, synthesis and optimization, layout generation, yield analysis and design centering, and test. This paper summarizes the problems for which viable solutions are emerging and those which are still unsolved