Result Length (Custom IQ)
determines the number of symbols that the VSA displays. For example, if the result length is set to 10, the VSA displays 10 symbols in time-domain traces (such as vector, eye, and constellation diagrams).
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Minimum: |
8 symbols (both 32 and 64 bit versions) |
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Maximum: |
100,000 symbols (both 32 and 64 bit versions) |
Impairment estimates and synchronization capability will be less accurate with very low result lengths.
Recommended minimum result lengths are as follows:
- For a signal with uniform probability transitions The probability of any given symbol does not depend on previous symbols. between constellation points, use 25 * number of constellation points. For example, for QPSK Quadrature phase shift keying (4 constellation points) you should use 25*4 = 100 minimum result length.
- For a signal with non-uniform probability of transitions between constellation points, you should increase the number of points depending upon the probability distribution characteristics (you may need to use 100 * number of constellation points or more for some extreme distributions).
Frequency lock range depends on constellation density (number of points, spacing between points). It is affected by the Synch Persistence Target setting.
Result lengths with Coarse Frequency Estimation Enable turned OFF in PPM 1) Parts Per Million or 2) pulse position modulation (parts-per-million - ratio of symbol clock error to symbol clock rate):
QPSK 5300
8PSK 4200
16PSK 1000
16QAM 800
32QAM 520
64QAM 330
See Also
