LSSP Simulation Parameters


The parameters for LSSP Simulation are identical to those for Harmonic Balance, with these exceptions:

For details about the parameters not described here, see the section HB Simulation Parameters.

Setting Up Ports

Set up the ports portion of the simulation using the information shown in the following table. Names listed in the Parameter Name column are used in netlists and schematics.



LSSP Simulation Ports Parameters  
Setup Dialog Name Parameter Name Description
Port Frequency LSSP_FreqAtPort[n] Ports must be placed and defined. Set the port number of the input source to 1, and the port number of the output Term (termination) component to 2.
Select   Contains the list of fundamental frequencies. Use the Edit field to add fundamental frequencies to this window.
- Add enables you to add an item.
- Cut enables you to delete an item.
- Paste enables you to take an item that has been cut and place it in a different order.
Edit   Edit the Frequency field, then use the buttons to Add the frequency to the list displayed under Select.
  Frequency   The frequency of the fundamental(s). Change by typing over the entry in the field. Select the units (None, Hz, kHz, MHz, GHz) from the drop-down list.

Defining Simulation Parameters

Defining the LSSP simulation parameters in ADS consists of these basic parts:

The following table describes the parameter details. Names listed in the Parameter Name column are used in netlists and schematics.

LSSP Simulation Parameter Options  
Setup Dialog Name Parameter Name Description
Device operating point level DevOpPtLevel Enables you to save all the device operating-point information to the dataset. Default setting is None.
  None None No information is saved.
Brief Brief Saves device currents, power, and some linearized device parameters.
Detailed Detailed Saves the operating point values which include the device's currents, power, voltages, and linearized device parameters.
FFT
  Fundamental Oversample FundOversample Sets the FFT oversampling ratio. Higher levels increase the accuracy of the solution by reducing the FFT aliasing error and improving convergence. Memory and speed are affected less when the direct harmonic balance method is used than when the Krylov option is used.
More... Oversample[n] Displays a small dialog box. To increase simulation accuracy, enter in the field an integer representing a ratio by which the simulator will oversample each fundamental.
Initial Guess
  Use Initial Guess UseInFile Check this box to enter a file name for a solution to be used as initial guesses. This file is typically generated from a previous simulation by enabling Write Final Solution. If no initial guess file name is supplied, a default name (using DC solution) is generated internally, using the design name and appending the suffix .hbs. A suffix is neither required nor added to any user-supplied file name. For example, if you have saved the Harmonic Balance solution from a previous simulation, you can later do a nonlinear noise simulation and use this saved solution as the initial guess, removing the time required to recompute the nonlinear Harmonic Balance solution. Or you could quickly get to the initial Harmonic Balance solution, then sweep a parameter to see the changes. In this latter case, you will probably either want to disable the Write Final Solution option or use a different file name for the final solution to avoid overwriting the initial guess solution. See Write Final Solution below (parameter: UseOutFile).
The Annotate value specified in the DC Solutions tab in the Options block is also used to control the amount of annotation generated when there are topology changes detected during the reading of the initial guess file. Since HB simulations also utilize the DC solution, to get optimum speed-up, both the DC solution and the HB solution should be saved and re-used as initial guesses.†
The initial guess file does not need to contain all the HB frequencies. For example, one could do a one-tone simulation with just a very nonlinear LO, save that solution away and then use it as an initial guess in a two tone simulation. The exact frequencies do not have to match between the present analysis and the initial guess solution. However, the fundamental indexes should match. For example, a solution saved from a two tone analysis with Freq[1]=1GHz and Freq[2]=1kHz would not be a good match for a simulation with Freq[1]=1kHz and Freq[2]=1 GHz.
If the simulator cannot converge with the supplied initial guess, it then attempts to a global node-setting by connecting every node through a small resistor to an equivalent source. It then attempts to sweep this resistor value to a very large value and eventually tries to remove it.
File InFile Specify a filename to save results.
Regenerate Initial Guess for ParamSweep (Restart)    
Final Solution
  Write Final Solution UseOutFile Check this box to save your final HB solution to the output file. If a filename is not supplied, a file name is internally generate using the design name, followed by an .hbs suffix. If a file name is supplied, the suffix is neither appended nor required. If this box is checked, then the last HB solution is put out to the specified file. If this is the same file as that used for the Initial Guess, this file is updated with the latest solution.
Transient simulations can also be programmed to generate a harmonic balance solution that can then be used as an initial guess for an HB simulation. ‡
File OutFile Specify a filename to save results.
Harmonic Balance Assisted Harmonic Balance HBAHB_Enable Set the HBAHB mode to Auto, On, or Off. Default is Auto and is recommended.

† See DC Simulation.
‡ See Harmonic Balance Simulation.

 

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