That is exactly what I was trying to say, there are no periods of "pause" expected, like in waveform per seconds of an oscilloscope. Once the AD9363 is tuned and locked on a frequency, then the Rx data stream is continuous, without any periods lost.
The minimum pulse that can be viewed is given by the ADC frequency. AD9363 have a maximum of 20MHz Rx bandwidth:
http://www.analog.com/media/en/technical-documentation/data-sheets/AD9363.pdf The 20 MHz limit comes from the maximum clock of the ADC (40 MHz), and not from the analog parts of the AD9363, so any pulse longer than 1/20MHz = 50ns will have a POI of 100% guaranteed. Anything shorter than 50ns will be based on luck only, so it's not relevant to test it with pulses shorter than 50ns.
One more thing to take into account here is that the ADC clock can be changed in the range of 400KHz-40MHz (this is how the 200KHz-20MHz tunable channel bandwidth is achieved). So, if we set the Rx bandwidth to 1 MHz, the minimum pulse with 100% POI guaranteed must be at least 1 microsecond long. Anything shorter than 1 us will be based on luck.
Of course, all that stands only if the whole chain works perfectly, and without any software bugs, so a test for POI totally makes sense, even when we expect 100% POI.
Now, assuming that the whole receiving chain is working properly, and that the above logic is correct, this is how I propose to test the POI: instead of preparing a pulsed carrier signal (a GHz range switch is not trivial), send just the pulse without any carrier. A single pulse of 50ns can be produced much easier with some digital counters or with logic gates.
For a narrowed Rx bandwidth, the DC pulse must be longer in order to have a 100% guaranteed POI.
E.g. for 500KHz Rx bandwidth, the minimum pulse with 100% POI guaranteed is 2 microseconds.
If the single DC pulse is seen on the output with 100% POI, then most probably the whole Rx chain is working correctly, so there will be no need to prepare a modulated pulse with variable length, which will be much harder to DIY than a non-modulated DC pulse.