Hubbel RFL PLC Hybrid Pro, Руководство пользователя

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RF-MCHYBRIDPRO-01
Hubbell Power Systems, Inc. – RFL™ Products
June 2019 15 973.334.3100
4 Hybrid Module Descriptions
This section contains details on the 1RU hybrid chassis and the individual hybrid modules such as
losses, isolation, etc.
For the purposes of this manual, the following assumptions are made:
-
All values stated in the “specification” tables are valid for the PLC frequency range, from
30 kHz to 500 kHz
-
All stated losses and isolation figures, such as insertion loss and trans-hybrid loss, assume
that all hybrid ports terminated into the specified termination impedance (50 ohms or 75
ohms).
4.1 Balanced Hybrid
BAL
TX1
TX2
> 30 dB
- 3.5 dB
- 3.5 dB
OUT
Figure 9 – Balanced Hybrid, Functional Diagram
The balanced hybrid is most often used to combine two transmitters onto a single coax connection
while providing high isolation (trans-hybrid loss) between the two transmitter inputs. This isolation
prevents the PLC transmitters from mutually loading each other, and from creating intermodulation
distortion products which can interfere with other PLC systems.
A balanced hybrid is “balanced” because its losses are balanced: the loss from each input to the output
is approximately 3.5 dB, meaning each signal loses a little bit more than half its power through the
hybrid. So, a signal at the TX1 port with a level of +30 dBm can be expected to have a level of roughly
+26.5 dBm at the OUT port. This is the price which is paid to achieve the high isolation between input
signals while combining those signals at the output port.
Isolation between input ports is typically greater than 30 dB. For example, a signal at the TX1 port with
a level of +30 dBm can be expected to have a level somewhere below 0 dBm when the same frequency
is measured at the TX2 port. The best isolation values will be seen when bench testing with near-
perfectly matched loads / impedances. In field applications, line tuning imperfections and impedance