Can the Hanning Window be represented in the time domain
So what you mean is that you want the continuous-time Hann window instead of the discrete-time window?

$$w_{Hann}(t) = 1 - \cos \left(2\pi \frac{t}{T} \right)$$ 

is not correct, since it goes to 0 at 0.

Blackman &amp; Tukey give the continuous time window as:

$$D_2(\tau)=\frac 1 2 \left (1+\cos \frac{\pi \tau}{T_m} \right )$$

for $|\tau| &lt; T_m$ and 0 elsewhere.

Wolfram Alpha

https://en.wikipedia.org/wiki/Hann_function

https://archive.org/details/TheMeasurementOfPowerSpectra/page/n58