new TV Tuner Chip, the Si2177

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Adam Nielsen a.nielsen at shikadi.net
Sat Sep 21 07:11:54 UTC 2013


> > The bandwidth of the I/Q pair is too large to be transmitted 
> > over USB for the reception of TV signals. After demodulation
> > the bandwidth is lower so it would (marginally) fit an USB 
> > interface if we talk about traditional analogue TV. For digital
> > TV the bandwidth reduction by the decoder is much larger.

Is that correct?  From what I can find, an analogue TV signal has a
bandwidth of around 6-8MHz.  The HackRF is an SDR that works over
USB2.0 and can capture a chunk of RF spectrum up to 20MHz, which
should be ample for one analogue (or even digital) TV signal, perhaps
even two if the channels are close enough together.

> How much is actually needed? You know there's USB 3 these days,
> which can transmit about a megabit with some change (due to
> overhead).

A megabit? :-)  USB3.0 has a signalling rate of 5Gbps and according to
Wikipedia, a usable data rate of up to 4Gbps.  If you can fit 20MHz of
RF over USB2.0 at 480Mbps, you should be able to start approaching
200MHz of bandwidth with a USB3.0 SDR!

Cheers,
Adam.




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