Gr_freq_xlating_fir_filter usage

GNU Radio
1

In the gr_xlating_fir_filter, how do I correctly use the
center-frequency parameter?

If I have a signal that is at 5MHz from baseband center, do I specify
-5MHz as the center-frequency? Or do I use the
“positive sense”??

–
Marcus L.
Principal Investigator
Shirleys Bay Radio Astronomy Consortium

2

On Tue, Jul 12, 2011 at 12:51 AM, Marcus D. Leech [email protected]
wrote:

In the gr_xlating_fir_filter, how do I correctly use the center-frequency
parameter?

If I have a signal that is at 5MHz from baseband center, do I specify -5MHz
as the center-frequency? Or do I use the
“positive sense”??

Hi Marcus,

It is the “negative sense” so you specify -5 MHz in order to tune to
+5 MHz from center. I think it is because in practice it
shifts/rotates the whole spectrum, so to get +5MHz down to 0 we have
to shift 5 MHz in the negative direction.
In a way calling it center is a bit misleading.

Alex