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Re: [Discuss-gnuradio] TV_RX anti-aliasing filter
From: |
Matt Ettus |
Subject: |
Re: [Discuss-gnuradio] TV_RX anti-aliasing filter |
Date: |
Wed, 26 Sep 2007 14:04:09 -0700 |
User-agent: |
Thunderbird 2.0.0.0 (X11/20070326) |
Nirali Patel wrote:
> Hello everyone,
>
> I am a new user and recently set up the USRP and TV_RX boards to receive FM
> radio and now trying to take the dive into capturing HDTV. I had a basic,
> maybe dumb question on the presence of a low pass filter before the A/D
> converter. Does anyone know if the TV_RX board has an anti-aliasing low pass
> filter on it? Or within the Microtune 4937 tuner module? I looked at the
> schematic for the daughter board and the data sheet for 4937 but I am not
> sure if there is one. The TV_RX I got has an IF frequency of 44MHz and I
> understand that undersampling it at 64 Msps with the A/D converter causes it
> to fold to 20 MHz. I wanted to know whether there is or there needs to be a
> low pass filter before the A/D converter to suppress any energy in the lower
> frequencies before sampling.
>
The output from the tuner module has already been filtered by a SAW
filter, so there is no need for any further filtering. There is only
significant energy in the desired band.
Matt