Choosing Frequencies for Full-Wave SPICE

If you plan to perform a full-wave SPICE analysis, use the Time Domain Calculation dialog box to help determine a suitable frequency sweep range for the solution.

To perform the calculation of suitable frequencies to solve:

1. In the Edit Sweep dialog box, click Time DomainCalculation.

The Time Domain Calculation dialog box appears.

2. Type a minimum rise time value in the Signal Rise Time box.

This value represents the time scale that will characterize the rate of change of the input time signal, which will be applied in the circuit simulator.

3. Type a value in the Time Steps Per Rise Time box.

The time sampling increment for the entire signal is calculated using

(1)

where

• Dt is the time sampling increment.
• tis the signal rise time.
• N_tis the number of time steps per signal rise time.

4. Type a value in the Number of Time Points box.

Note that the input time signal duration is determined using , where N is the number of time points.

5. Click Calculate.

• HFSS now determines the Maximum Frequency using

  (2)

• where F_max is the maximum frequency.

HFSS determines the Frequency Step Size using .

6. Click OK to transfer the data to the frequency sweep fields in the Edit Sweep dialog box.