SMIQ
Bit Error Rate Test
1125.5555.03
2.373
E-9
2.23.1.2 Signal Path and Waveform
See also chapter 1, section "Option SMIQB21", Connector.
Test setup
The signal is computed using one of the modulation sources listed above and then
output by the SMIQ and sent to the DUT (device under test). The latter
demodulates the source bits contained and returns them to the SMIQ together
with a transfer clock. In the SMIQ, the data bits are checked for errors. The total of
the transmitted bits and the faulty bits are counted. The quotient of error bits/total
bits is the BER.
PRBS data
To be able to detect faulty bits in a BER measurement, the data generation
polynomial must be known. Data are calculated with the aid of so-called pseudo-
random binary sequences (PRBS). These are quasi-random bit sequences which
are repeated according to the selected polynomial.
An advantage of the PRBS data is that the bit error detector has only to know the
polynomial but not the total sequence. Furthermore, the analysis can be started
anywhere in the bit stream, ie the bit-stream source and the analyzer need not be
synchronized.
Transfer clock
Should the DUT not provide a transfer clock, the bit clock can be taken from the
output connector PAR-DATA for the generation of the signal using option
SMIQB11 (DGEN). If AMIQ is used as the IQ source, a marker channel may be
programmed as clock output. However, the clock-to-data ratio is to be observed.
