GUI Reference
R&S
®
ZNB/ZNBT
626
User Manual 1173.9163.02 ─ 53
This dialog is available with
option R&S
ZNB/ZNBT-
K20 only.
In transmission systems known losses of the channel are typically compensated
already in the transmitter. The most common setting is to boost high frequencies com-
pared to low frequencies since the channels show typically larger losses for high fre-
quencies.
This type of equalization is done using finite impulse response (FIR) filters using
between 2 and 4 taps. The filter’s sampling time is identical to bit period.
The coefficients of the FIR filter are not provided directly but in terms of pre- and post-
cursor values. The cursor value is defined as voltage ratio of two adjoining bits. Since
up to four taps can be used, the bit pattern for defining all cursor values must use four
consecutive bit values. Here a repeating bit pattern 0 1 1 1 1 0 is used. By definition
the voltage levels for encoding the bits are symmetrical using +V for the ones and -V
for the zeros.
In the graphic below the blue and the red trace indicate the signals used for differential
encoding on a symmetric line. Va indicates the level directly after a transition, Vd indi-
cates the level before a transition, Vb and Vc are optionally used to specify further lev-
els after the transition.
0
1
1
1 1 0
...
...
Va Vb Vc Vd
In dB the pre- and post cursors are defined as:
●
Pre Cursor = 20 log
10
( Vd / Vc )
●
Post 1 Cursor = 20 log
10
( Vb / Va )
●
Post 2 Cursor = 20 log
10
( Vc / Vb )
Simple applications of the emphasis only define the Post 1 Cursor. Use a negative
value (in dB) for increasing the amplitude of the first bit after a transition. Below an
example for Post 1 Cursor = -3dB:
Applic Softtool
