Bit Error Rate Tester | BERT 1005
Quantifi Photonics Ltd.
Version
2.04
52
Pulse pattern generation
The Pulse Pattern Generator (PPG) generates signals with different patterns, such as PRBS9 or DIV8.
The output voltage, de-emphasis levels, cursor, and cross point values can be set independently for each
PPG channel, and can be also inverted to a digital NRZ format pattern at the pattern generator output.
The BERT PXIe takes advantage of the common 10MHz and 100MHz clocks on the PXIe chassis
backplane, which allows the user to install multiple BERT PXIe modules on the same chassis to have a
common clock reference. Therefore, all the PPG channels in the chassis synchronize to each other. This
ability is useful when testing more than four channels.
All PPG channels are linked to the same pattern. The amplitude, de-emphasis, cursor, and
cross-point are not linked and can be independently controlled on a per-channel basis.
To configure the pattern generation settings, click the PPG tab.
To reduce crosstalk between channels, ensure 50ohm loads are used to terminate unused PPG
channels.
8.5.1
Set up the transmitter de-emphasis
The pattern generator features adjustable two-tap clocked/ unclocked output de-emphasis, to
respectively compensate for the pre-cursor or the post-cursor inter-symbol interference in the
transmission medium. The generator can be programmed to enable either the pre-cursor de-emphasis
or post-cursor de-emphasis, but not both simultaneously.
De-emphasis on the output channels boosts the high frequency content by the selected amount. This
type of adjustment can be useful for counter-balancing the loss of higher frequency components in the
signal as it travels down a length of coaxial cable.
The PLL must be enabled and locked for the pre-cursor or post-cursor de-emphasis to operate.
De-emphasis of the output waveform is realized by summation of the contributions of a main tap and
the pre-cursor tap. By default, there is no de-emphasis applied upon power-on.
The control of the post-cursor de-emphasis is available at any data rate; however, the control of the pre-
cursor is only available for input data rates between 6.25Gbps to 7.25Gbps, 12.5Gbps to 14.5Gbps, or
25Gbps to 29Gbps. When both the pre-cursor and the post cursor de-emphasis are available, they are
mutually exclusive.
