The input data rate of interpolator model

[kdhjp]

Good morning ,everyone ! I'm recently studying the USRP-2944R. I am confused about the interpolator in DSP. According the help document, the passband of anti-image filter is 0.4*input data rate, and the stopband is 0.6*input data rate .And the input data rate is associated with the input valid signal. However ,I can't control the input valid signal ,so how can I ensure that the anti-image filter work effectively ? What's more , I'm also confused about the function of the 'clock *2' signal.What does it mean?

I have been confused for nearly one week.Anyone could help me ? Thanks a lot in advance ! 

[carmen9]

Hi,

I think this is the page you are referring to (Fractional Interpolator): http://zone.ni.com/reference/en-XX/help/374500C-01/oscopes/idl_dsp_fpga/

From the description of data rate: The input sample rate input may be in the range of [1.52588E-5 to 1.0] -> This corresponds to interpolation factors of [65,536.0 down to 1.0], and interpolation factor = 1 / input sample rate .

Regarding the clock x 2, it is explained in Over-clocking  that this VI requires an additional in-phase clock at two times the frequency of the single-cycle Timed Loop clock.

[kdhjp]

Thanks for your reply. I have seen this page. I'm confused about the passband and stopband of the anti-image filter. According to this page, it is associated with the input data rate.And the input data rate is associated with the 'input valid signal'. And I find the ‘input valid’ signal is changing with the 'input sample' rate. So  how can I ensure my signal could pass the filter losslessly ?  

And I think the output data rate is equal to the Data clock, is it right?

Thanks in advance!

[carmen9]

The stopband rejection range is >85 dB so anything >85 dB will be filtered.