Bit Error Rate Test SMIQ
1125.5555.03 2.368 E-9
2.23 Bit Error Rate Test
Option SMIQB21 allows evaluation of the signal demodulated and decoded by the DUT. For this
purpose, a PRBS-modulated data sequence (PRBS = Pseudo R
andom Binary Sequence) is sent to the
DUT. This data sequence can be generated continuously (by means of option SMIQB20) or in sections
(option SMIQB60), using a loaded waveform.
The PRBS data sequence is decoded by the DUT and sent to the SMIQ in the form of clock and data
signals. The SMIQ synchronizes to the known PRBS sequence and counts the bit errors.
RF, containing
PRBS Data
Clock
Demodulated Data
Fig. 2-234 BER Measurement
Termination of a measurement can be induced by various criteria. With option SMIQB21,
measurements can be stopped either manually or because of one of the following two criteria: a user-
defined number of data bits has been transmitted or a maximum number of errors has been detected.
By means of the RESTART function (eg for IQ signals that are not generated continuously and therefore
do not contain integer multiples of PRBS sequences) BER results can be integrated onto the (partial)
sequences. In this way, long BER measurements can also be performed on short IQ signals (which
normally do not allow BER measurement because the PRBS sequence is not continuous).
The BER measurement can also be performed separately (with data from another source).
In addition to testing PN bit sequences, the option may also be used to verify CRC checksums. This
operating mode is described in section 2.23.2.
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