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FAQ
Chapter 9
FAQ
9.1 Q. What is coherent sampling?
9.2 Q. How to manage the internal temperature?
9.3 Q. What are the differences between the various data streaming firmware options
supported by high-speed ADC cards ?
9.4 Q. What happens if the host processor goes in hibernation mode?
9.1 Q. What is coherent sampling?
A. Coherent Sampling refers to the relationship between the input frequency F
F
, number of cycles in the sampled set and the number of samples. With coherent sampling one is
s
assured that the signal power in an FFT is contained within one FFT bin (assuming a single input tone).
The condition for coherent sampling is given by:
F
/F
=N
in
s
For example if we have N
F
/2, let's say F
s
round down to N
that satisfies coherent sampling.
The integer number should be chosen carefully. We have three possible types of integers, even, odd,
and prime. Even is not a good idea since we would hit the same code every M
much less than N. Odd is a better idea since it takes longer to hit the same code. According to some
sources a prime number of cycles is the best (with the exception of the prime 2) because it takes a
long time before the same code repeats.
——————————————————————
9.2 Q. How to manage the internal temperature?
A. The operating temperature of the U5310A as specified in the U5310A datasheet, is the workstation
internal ambient temperature at intake of the ADC card's fan.
84
/N
cycles
samples
= 2
samples
= 44 MHz, then N
in
= 901 and we would get F
cycles
11
, and F
= 100e6, and we expect and input frequency close to
s
= 901.12 which is close to an integer. We could therefore
cycles
= 43.994140625 MHz, which is an input frequency
in
84
84
85
86
, sampling frequency
in
, where M can be
samples
U5310A User's Manual
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