GS1528 Data Sheet
GS1528
SDO
SDO
Figure 3-3: Static Protection Diodes
3.4 Output Return Loss Measurement
To perform a practical return loss measurement, it is necessary to force the
GS1528 output to a DC high or low condition. The actual measured return loss will
be based on the outputs being static at V or V -1.6V. Under normal operating
CC
CC
conditions the outputs of the GS1528 swing between V -0.4V and V -1.2V, so
CC
CC
the measured value of return loss will not represent the actual operating return
loss.
A simple method of calculating the values of actual operating return loss is to
interpolate the two return loss measurements. In this way, the values of return loss
are estimated at V -0.4V and V -1.2V based on the measurements at V and
CC
CC
CC
V
-1.6V.
CC
The two values of return loss (high and low) will typically differ by several decibels.
If the measured return loss is R for logic high and R for logic low, then the two
H
L
values can be interpolated as follows:
R
= R - (R -R )/4 and
H H L
IH
R = R +(R -R )/4
IL
L
H
L
where R is the interpolated logic high value and R is the interpolated logic low
IH
IL
value.
For example, if R = -18dB and R = -14dB, then the interpolated values are R =
IH
H
L
-17dB and R = -15dB.
IL
16632 - 5 June 2005
9 of 13
GENNUM [ GENNUM CORPORATION ]
