Base band signal sample frequency in RFX 900 daughter board

GNU Radio
1

Hi,

I use USRP1 and RFX 900 daughter board to receive an 925MHz signal. The
receiver configuration code is shown below. Some people told me that the
RFX 900MHz board will do down conversion and convert the 925MHz signal
to a
base band signal automatically. Can you tell me what is the frequency to
sample the base band signal? I cannot figure it out according to the
following code. Thanks.

Receiver’s configuration code:
rx = usrp.source_c(0, dec_rate, fusb_block_size = 512, fusb_nblocks = 8)
rx_subdev_spec = (1,0)
rx.set_mux(usrp.determine_rx_mux_value(rx, rx_subdev_spec))
rx_subdev = usrp.selected_subdev(rx, rx_subdev_spec)
rx_subdev.set_gain(rx_gain)
rx_subdev.set_auto_tr(False)
rx_subdev.set_enable(True)
r = usrp.tune(rx, 0, rx_subdev, freq)

Pengyu

2

On 8/9/12 11:09 AM, pengyu zhang wrote:

Receiver’s configuration code:
rx = usrp.source_c(0, dec_rate, fusb_block_size = 512, fusb_nblocks = 8)
^^^^^^^^
The decimation rate determines the final sample rate.

For example:
Since the USRP1 digitizes at 64 Msamples/sec, a decimation factor
of 64 would yield baseband complex samples at 1 MSamples/sec.

@(^.^)@ Ed

3

Got it. How to figure out the frequency USRP1 uses to digitize the
signal?
Is 64M samples/sec the default configuration? Thanks.

On Thu, Aug 9, 2012 at 11:21 AM, Ed Criscuolo