Number of Frequencies 
Lets you set the desired number of natural (resonant) frequencies to be calculated. The default is to calculate the lowest five frequencies. Rigid body modes are calculated by the FFEPlus solver. A body without any restraints has six rigid body modes. Rigid body modes have zero frequencies (infinite period).
If the working scenarios of the model include dynamic loads, it is important to calculate at least one frequency that is higher than the frequency of the load. In most situations, resonance is not desirable because it causes failure. However, some devices exploit resonance to trigger an event while providing measures to control the excessive associated deformation.

Upper Bound Frequency 
Lets you set the upper bound frequency of the desired frequency range. Use the default value of zero unless you are not interested in natural frequencies higher than a certain value. Entering zero results in calculating the specified number of frequencies.
For the FFEPlus solver, you can specify the Number of Frequencies or the Upper Bound Frequency. For the Direct Sparse solver, you can only specify the Number of Frequencies and specify a frequency shift.

Calculate frequencies closest to (frequency shift) 
Available for the Direct Sparse and Intel Direct Sparse solvers. Select this option to specify a frequency value of interest. The software calculates the frequencies closest to the specified value. This option is referred to as frequency shift in the literature. You can use this option to avoid calculating rigid body modes.
In cases where the frequency analysis cannot run due to singularity of the stiffness matrix, use the frequency shift option to overcome the singularity issue. Increase the shift value gradually from zero until the Direct Sparse solver successfully calculates the requested frequencies.
If you set a higher value for the frequency shift, the Direct Sparse solver selectively calculates the requested number of frequencies, which are clustered around the shift value. Thus, you can avoid the computation of lower range frequencies (including the rigid body modes), which are of no interest to your analysis, and save computational time.

Use inplane effect 
This option is internally activated to account for the effects of any applied loads on the model's stiffness. See also SOLIDWORKS Simulation Help: Use Inplane Effect. 
Use soft spring to stabilize model 
Select this option to add soft springs to stabilize inadequately supported models.
