I tried to sample NTSC signal with decimation rate = 8 (8Msps) using
board. The 8Mspc sample rate is supposed to covered the whole range of
TV channel bandwidth. Thus, the obtained signal should contain all TV
information including luminance and color. I have two related questions:
- For TVRX board, as we know, the output signal is a 6MHz chuck. But in
which band is this 6MHz bandwidth located? For example, if the carrier
frequency is 477.25MHz, is the output signal from 477.25-1.5MHz to
477.25+4.5MHz, or from 477.25-3MHz to 477.25+3MHz, or in other band?
- I analyzed the frequency response of the sampled signal, and found
are two peaks in spectrum. A higher peak is located in DC frequency.
one, which is a little bit lower, is located at roughly f = 2.5MHz. It
different from what I expected. My original thought is that the second
should be in f=3.58MHz which is the frequency of the subcarrier carrying
color information. Could someone help to explain this?