ABB ETL600 Instruction Manual page 66

ABB Switzerland Ltd
Power
Amplifier
+
Tx P1LA
-
Rx-Filter
Rx
Fig. 3-23
Both topologies have specific advantages and disadvantages listed in
Table 3-2.
Analog front end with Rx-filter
Fig. 3-23
(
-
Rx filter required
-
Return loss is low in the Rx
frequency band
+
Applicable for 40 and 80 W
+
Applicable for full range of
nominal bandwidths
+
Higher Rx selectivity and better
suppression of spurious Tx
signals due to halved Rx- and
Tx-filter bandwidths
+
Lower frequency gap to parallel
PLC due to narrower Tx filter
+
No restriction regarding the
position of Tx- and Rx-bands
Table 3-2
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
1KHW001489-EN
Tx-Filter
E5TX
Hybrid P3LE
P4RX
a
The two possible topologies of the RF front end
a)
Comparison of RF front end topologies with and without Rx-filter
November 2005
Power
Amplifier
+
Tx P1LA
-
RF
Hybrid
Rx
Analog front end without Rx-filter
Fig. 3-23
( b)
+
No Rx filter required
+
Return loss is high also in the Rx
frequency band
-
Only applicable for 40 W
-
Only applicable for nominal
bandwidths of 16 kHz and less
-
Reduced selectivity in the Rx-
signal-path due to wider Tx-filter
-
Higher frequency gap to parallel
PLC due to wider Tx filter
-
Only applicable if Tx- and Rx-
bands are adjacent
Structure and Function
ETL600
Tx-Filter
RF
P3LE E5TX
b