XRT5894 Datasheet, PDF (14/19 Pages) Exar Corporation – Four-Channel E1 Line Interface (3.3V or 5.0V)

XRT5894
Transmitter Output Return Loss Measurements
The following measurements were made with a Wandel
and Goltermann SNA--2 Network Analyzer equipped with
an RFZ--1 75W Return Loss Bridge. A 75W to 120W
impedance matching transformer was used to make the
120W measurement. A network analyzer calibration run
subtracted out the effects of this transformer.
Test Conditions:
D Output transformer ratio was 1:2.
D Transmitter series resistors (R3 and R4 in Figure 1)
were 9.1W .
D Device was powered from a 3.3V source, transmitter
was enabled, and no output data was present.
This configuration was used for both 75W and 120W
measurements. The only change was the termination
resistance provided by the return loss bridge.
Test Results:
Table 5 compares measured output return loss with
requirements in ETSI FINAL DRAFT prETS 300 166,
June 1993. These results show that measured return loss
is mainly determined by the characteristics of the output
transformer. This is particularly evident for the 120W load
where the measured result is better than the calculated
value.
Specified
Frequency
0.025 fb
0.05 fb
1.5 fb
Frequency
(KHz)
51.2
102.4
3072
ETSI Spec.
(Min. dB)
6
8
8
Meas. Value (dB)
75W Load
22.6
22.6
18.0
Meas. Value (dB)
120W Load
15.4
15.7
14.6
Table 5. Transmitter Output Return Loss Measurements
Notes:
fb = 2048KHz
This data shows that the XRT5894 is fully compliant with the ETSI Output Return Loss Specification for E1 operation with either
75W or 120W loads.
Rev. 1.10
14