Hi Jon! On 06.10.2015 04:44, Jon Elson wrote: > On 10/05/2015 10:16 AM, Mark Wendt wrote: >> >> Well, it does say the "analogue bandwidth" is 2 MHz. It could be >> using sub-sampling to acheive that bandwidth. >> >> > Even if the analog BW is 2 MHz, if you feed in a 2 MHz > signal with a 2.5 MSa/sec sampling > rate, you are bound to get a seriously aliased signal. it > will probably look like a perfectly clean sine wave at 500 KHz. > > Lovely!
This is absolutely true for simple regular sampling of the signal with a 1:1 reconstruction. But if you have a good trigger and a periodic input signal, it is possible to use several periods which are sampled at slightly shifted points. If you then take all those samples and overlay them onto a single period, it looks as if you had used a higher sampling rate. This is sometimes called the "equivalent-time sampling": http://www.tek.com/document/application-note/real-time-versus-equivalent-time-sampling btw: Having a high analog bandwidth (OK, can 2MHz be considered "high"? Anyway...) is a good thing whatsoever. It usually also means that the analog frontend won't greatly attenuate your signal or cause a lot of frequency-dependent phase shift. And it may help you detect some transients which you would otherwise miss. Regards, Philipp
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