TIME DOMAIN NONLINEAR TRANSIENT ANALYSIS SIMULATION

MMICAD WAVEFORM, Optotek's time domain, transient analysis simulator, allows the prediction of waveforms in fast, nonlinear circuits where accurate S-parameter data can be imported and used in the simulation. MMICAD WAVEFORM represents a major advance in the accurate prediction of the nonlinear response of RF and microwave circuits and can be used to great advantage in the design of high speed optical communication modules, microwave packages, and nonlinear transmission lines.

MMICAD WAVEFORM Version 3 represents the state-of-the-art in transient circuit analysis, combining the accuracy of frequency domain simulation of passive circuit elements with time domain simulation of nonlinear components using the best available models. The MMICAD WAVEFORM time domain simulator has been developed for use in the prediction of waveforms in fast, microwave circuits where accurate S parameter data can be imported and used in the simulation. This capability allows the designer to include complex, frequency-dependent effects in passive circuits. Since the simulator can import S and Y parameter data for passive networks with up to 19 ports, the designer can make use of advanced electromagnetic simulators or measured data to determine the transfer response for the passive circuitry external to a MMIC, and so predict the effects of both the packaging and interactions between the MMICs. To ensure accurate simulation, advanced GaAs FET, HEMT and BJT models are included, in addition to the SPICE diode. Externally defined signals, as encountered in the microwave and optical communications worlds, can be used to control voltage and current sources.

MMICAD WAVEFORM operates as a stand-alone package, and also interfaces with other components of the MMICAD Suite (for example, the MMICAD Linear Simulator and LASIMO transistor parameter extractor). Time domain analysis tools complement frequency domain circuit simulators, allowing prediction of the non-steady state response of a circuit. The strengths of time domain simulation are as follows:

• Prediction of voltage waveforms at every node in a nonlinear circuit.
  
  
• Analysis of pulsed RF network responses.
  
  
• Analysis of filter step-function
  
  
• Examination of transients and start-up times in oscillators.
  
  
• Visualization of switching waveforms in fast digital circuits.
  
  

MMICAD WAVEFORM Version 3 imports processed S-parameter data, supports advanced GaAs MESFET, HEMT and BJT models, and integrates with the other components of Optotek's MMICAD Suite.

The software is intended for the design of circuits where difficulties are experienced with conventional time domain and/or harmonic balance simulators. Beneficial applications for MMICAD WAVEFORM would have some, or all, of the following characteristics:

• complex, externally defined, volage and/or current source driving waveforms
  
  
• signal large enough to cause strongly nonlinear operation of the active devices
  
  
• circuits which have inherently, and strongly, nonlinear electrical response, including assessing the stability of power MMICs
  
  
• circuits consisting of a mixture of microwave passive elements, defined by S parameter data, and nonlinear active devices
  
  
• "transient" phenomena of interest, for example, the start-up of oscillations, or phase shift as a function of time in pulsed microwave circuits such as phased array radar systems.
  
  

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Application Areas

• Predicting the behavior of strongly nonlinear circuits containing such elements as step recovery diodes and nonlinear transmission lines while still maintaining the full description of the frequency-dependent effective dielectric constants and loss in microstrip lines.
  
  
• Examining waveform distortion in amplifiers (adjacent channel power ratio, 1 dB compression, 3rd order intercept), including spectral regrowth.
  
  
• Determining whether an amplifier will unintentionally oscillate, possibly due to the bias circuitry.
  
  
• Predicting the linear and saturation characteristics and functioning of transimpedance amplifiers.
  
  
• Predicting the settling time of a circuit with automatic gain control.
  
  
• Emulating the use of a load pull tuner to estimate the load and source impedance for maximum power gain.
  
  
• Determining oscillator start-up conditions, with prediction of the resultant waveform and phase relationships.
  
  
• Determining the dynamic waveform characteristics of a voltage-controlled-oscillator in which the control voltage is varied.
  
  
• Predicting signal integrity in high-speed digital circuits including rise time, timing delay, ground bounce, crosstalk and reflection.
  
  
• Predicting the response of a nonlinear circuit to a complex driving waveform such as an NRZ-PRBS signal. Viewing the predicted "EYE" diagram at any node in an optical fiber communications circuit.
  
  
• Checking all relevant components in a nonlinear circuit to verify that parameters such as the voltage across the device, the average dissipated in the device and the current through a metal track are within design limits.
  
  

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Features

Time domain simulation augments harmonic balance nonlinear simulation.

MMICAD WAVEFORM supports:

• Use of RLC lumped passive elements
  
  
• Independent and controlled voltage and current sources.
  
  
• Nonlinear SPICE-equivalent diode model.
  
  
• Advanced GaAs MESFET, HEMT and BJT models, including EEHEMT, TOM3 and Gummel-Poon.
  
  
  • model parameters can be extracted from DC bias and S-parameter data through the use of Optotek's LASIMO^TM model extraction software.
    
    
• Database for commonly used GaAs transistors.
  
  
• Use of S-parameter data derived from:
  
  
  • microwave circuit theory simulators such as the MMICAD Linear Simulator
    
    
  • electromagnetic simulators
    
    
  • vector network analyzer measurements
    
    
• Circuit topology defined using MMICAD WAVEFORM schematic front-end.
  
  
• Digital bit stream definition, with arbitrary waveform import capability used to control a current or voltage source.
  
  
• Display of voltages at each node and currents into each element part on the circuit schematic, allowing the user to verify the DC bias condition of the circuit.
  
  
• Voltages at all nodes and currents in each element are saved in a SPICE-compatible raw data file for each time step, allowing the subsequent display of waveforms, I-V characteristics, bias plane trajectories, and circuit transfer characteristics.
  
  
• Complements existing time domain and harmonic balance simulators allowing:
  
  
  • prediction of voltage waveforms at every node in a nonlinear circuit
    
    
  • analysis of pulsed RF network responses
    
    
  • examination of transient and start-up times in oscillators
    
    
  • analysis of filter step-function
    
    
  • detection of unintentional oscillation in amplifier circuits
    
    
  • assessment of response to complex driving signals such as in NRZ-PRBS optical communication circuits
    
    
  • visualization of switching waveforms in fast digital circuits
    
    

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Software and Hardware Requirements
MMICAD WAVEFORM Version 3 runs under Windows 95, 98, 2000, ME and NT. The minimum recommended system configuration is a Pentium II with 64MB RAM.

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Pricing

Contact sales@optotek.com.

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