Learning Forum

[KENNY.HH.CHEN]

We attempted to use Interconnect to perform FFT, and after incorporating the formula, we could generate time-varying frequency modulation as shown in the figure below: the horizontal axis represents time, and the vertical axis represents frequency. You can observe the frequency shifting from low to high and then back to low, forming a triangular wave.

Next, we aim to transform this triangular wave using the formula cos(2piFT), where F is the time-varying frequency modulation mentioned above. For related settings, refer to the following image:

From the results displayed on OSC_2, the frequency pattern is slow-->fast-->slow-->fast, which is inconsistent with our expected result of slow-->fast-->slow.

Regarding this issue, I am wondering if there is a conflict between the time $T$ of the triangular wave itself and the time $t$ used in $\cos (2\pi ft)$, which could be causing this result?

 

Thanks.

[Chih-Hao Chen]

Hi Kenny

In summary.  the equations should be:

phi(t)

d pi(t) /dt = f(t)

s(t) = cos(2*pi*phi(t))

In your case, we start from f(t). The first step is to obtain phi(t), which is the integral of f(t).

Once we found phi(t), we could plugthis to cosine function and got s(t).