ABB ETL600, Instruction Manual

Page: 66 / 382

ABB Switzerland Ltd
1KHW001489-EN ETL600
E5TX
RF
+
-
P1LA
P3LE Hybrid
Rx-Filter
P4RX
Tx
Rx
Power
Amplifier
Tx-Filter
a
E5TX
RF
+
-
P1LA
Power
Amplifier
P3LE
Hybrid
Tx-Filter
Tx
Rx
b
Fig. 3-23 The two possible topologies of the RF front end
Both topologies have specific advantages and disadvantages listed in
Table 3-2.
Analog front end with Rx-filter
(
Fig. 3-23
a)
Analog front end without Rx-filter
(
Fig. 3-23
b)
-
Rx filter required
+
No Rx filter required
-
Return loss is low in the Rx
frequency band
+
Return loss is high also in the Rx
frequency band
+
Applicable for 40 and 80 W
-
Only applicable for 40 W
+
Applicable for full range of
nominal bandwidths
-
Only applicable for nominal
bandwidths of 16 kHz and less
+
Higher Rx selectivity and better
suppression of spurious Tx
signals due to halved Rx- and
Tx-filter bandwidths
-
Reduced selectivity in the Rx-
signal-path due to wider Tx-filter
+
Lower frequency gap to parallel
PLC due to narrower Tx filter
-
Higher frequency gap to parallel
PLC due to wider Tx filter
+
No restriction regarding the
position of Tx- and Rx-bands
-
Only applicable if Tx- and Rx-
bands are adjacent
Table 3-2 Comparison of RF front end topologies with and without Rx-filter
Dummy load P3LK:
The transmitter is terminated by its rated load by inserting the dummy
load P3LK in place of the RF hybrid. In this way a local loop is formed,
which enables both transmitter and receiver to be fully tested. The
transmitter frequency band is automatically converted to the receiver
frequency band when the dummy load is inserted. Also, the equalizer
in the Rx signal path of the ETL600 is bypassed.
3-34 November 2005 Structure and Function