Tx frequency changing by clk_divider

GNU Radio
1

Dear all,

I’m trying to use clk_divider block to down the frequency of baseband PN
code in project gr-sounder to 32kHz. The time quest analysis of the
verilog code shows the result is correct. After the FPGA bitstream
loaded,however, the waveform of the signal still contains some high
frequency component (noise) but much more better than PN code spread
32MHz.Â

The major problem of the frequency decreasing is the transmitting signal
from the antenna doesn’t show the result of BPSK modulation in the
waveform of the signal. Could you please give some suggestions about
what the problem?

Thanks in advanced.

Regards,
Yan

2

On Wed, Jan 27, 2010 at 15:08, Yan N. [email protected] wrote:

The major problem of the frequency decreasing is the transmitting signal
from the antenna doesn’t show the result of BPSK modulation in the waveform
of the signal. Could you please give some suggestions about what the
problem?

I’d like to help you out with this, as I wrote the original gr-sounder
FPGA code, but to be honest I have no idea what you’ve done or what
issue you are seeing with it.

Could you perhaps elaborate with the kinds of extensions you have
written to it, maybe a description of your signal flow, post links to
screenshots of your lab equipment displays, or something more concrete
than what you have written above?

What is it doing that it shouldn’t be, or what isn’t it doing that it
should?

Johnathan

3

Hi Johnathan,

I’m doing something similar as you did in gr-sounder project, sending a
code modulated as BPSK with the suppplied center frequency, but
different code (which contains 1 and -1 also), and bandwith for the
code, which is 32kHz instead of 32MHz. I used the clk_divider block to
down the frequency to 32kHz, then I monitored the signal from the
antenna part on daughterboard by an oscilloscope. The waveform of the
signal is a nicer sinusoid wave, but it doesn’t show the phase shift for
-1 part in the sequence.

I’m not sure if it’s clear. If not, I will post some photos of the
oscilloscope, but it just a continued sine wave without any phase shift
for BPSK modulation.

Thank you so much!

Regards,
Yan

----- Original Message -----
From: Johnathan C. [email protected]
Date: Thursday, January 28, 2010 7:19 am
Subject: Re: [Discuss-gnuradio] tx frequency changing by clk_divider
To: Yan N. [email protected]
Cc: [email protected]