LTSpice Frequency variable source
Add a B source with a time value in the parameter"

For example put this in for the value of the B-source:


  V=0.00205*sin(2 * pi * time * (1 + (2 * time)))


time is a system variable, so you are essentially doing this:

$$ V = A\sin(2\pi t*(1+\beta t))$$

The amplitude can be varied with A and the frequency with \$\beta\$, you can also choose other equations, there are if statements and other neat things you can do to generate a source.

You either have to do math or play with the values to get the starting frequency and ending frequency.