Re: [Discuss-gnuradio] Issues with porting a radio design to USRP2

[Matt Ettus]

On 12/29/2009 10:49 AM, Charles Irick wrote:
> Hello,
> I'm currently trying to port a radio design to the USRP2 platform but
> I am having a few issues. The current radio hardware contains a DAC
> with variable sampling rates allowing for it to be a multiple of the
> bitrate. It is currently using an IF of 60Mhz and a bitrate of 6Mbps.
> I'm wondering if there are any utilities the USRP2 provides for
> designing radios where the sampling rate and bitrate are not
> multiples, such as a DDS, given that the sampling rate is locked to
> 100MS/s. Thanks in advance.

We do have all sorts of DDS modules in the FPGA and in software, but 
that will only change the center frequency, not sample rate.

There are many resampling options in GNU Radio.  There are polyphase 
resamplers, rational resamplers, arbitrary resamplers, etc.  There is 
also timing recovery.

While it is often convenient to have a hardware sample rate which is an 
integer number of symbols on the transmit side, you will usually still 
need to resample on the receive side for timing recovery.


Matt