Chapter 16
Performing RFoCPRI Testing
JD700B Series User’s Guide
561
2
Select the unit of the display scale from:
dBm
,
dBV
,
dBmV
,
dBµV
,
V
, or
W
.
The scale unit on the screen changes accordingly.
Setting scale per division
You can use the
Scale/Div
feature to change the scale per division, representing the value of one division
on the horizontal scale. The default setting is 10 dB per division and the maximum value can be set up to
20 dB.
Procedure
1
Press the
AMP/SCALE
hard key.
2
Select
More (1/2) > Scale/Div
.
3
Enter a value between 1 and 20 by using the numeric keys.
4
Press the
dB
soft key to complete the entry.
Setting external offset
You can turn the
External Offset
on and manually set the external offset value. An offset consists of a cable
loss and a user offset, and the measurement result shows the value reflecting both offset values. When the
external offset value is set at 40 dB, the measurement result compensates 40 dB.
Procedure
To set the external offset:
1
Press the
AMP/SCALE
hard key.
2
Toggle the
External Offset
soft key to
On
.
3
Enter a value by using the numeric keys.
4
Press the
dB
soft key to complete the entry.
To turn the external offset off:
1
Press the
AMP/SCALE
hard key.
2
Toggle the
External Offset
soft key to
Off
.
Enabling auto leveling
It is normal that you see higher level of RSSI in CPRI spectrum than you have seen in RF spectrum because
the digital signal has a different gain level from RF’s. If you use the Auto Leveling feature and enter the
Noise Figure (NF) for the system to be tested, the instrument calculates an offset that compensates the
digital gain of RRH and applies it to the spectrum automatically to displace the level of spectrum to a known
RSSI power even though its accuracy cannot be guaranteed. Offset calculation for Auto Leveling is based
on the following:
Auto Level offset = (Noise Floor of RFoCPRI) – (Ideal Noise Floor of RRH), where (Idea Noise Floor) =
N.F (RRH) + Thermal Noise + 10log (RBW)
Procedure
1
Press the
AMP/SCALE
hard key.
2
Press the
Auto Leveling
soft key.
A calculated level of offset without NF is applied as the external offset and the user input field is
activated for entry of the noise figure value.
