Hybrid Applications; Terminal Line Applications - Ametek UPLC CU44-VER04 Applications Manual

UPLC™ Application Manual
DTT Trip
(Trip 1)
D
f (f – f)
L C
Figure 3–17. UPLC™ 3-Frequency System.
criminate between these four frequencies and pro-
vide the necessary input to the logic portion.
The logic is two sets of the full unblock logic. This
allows you to select either command function,
DTT or Unblock. Should both inputs be keyed
simultaneously, the frequency that is sent will
engage both Trip A and Trip B outputs.
The trip test feature is not available in the four-fre-
quency system.
3.3.6 Three-Terminal Line
Applications
When a three terminal line protection requires
power line carrier equipment, each terminal must
have one transmitter and 2 receivers, since each
terminal must receive a signal from each of the 2
other ends of the line. Fig. 3–20 is a representation
of the transmitter/receiver complement required to
implement a single function: Hybrids or other iso-
lation devices are required between transmitters
and transmitters to receivers. See the following
section for details.

3.4 Hybrid Applications

The purpose of the hybrid is to enable the connec-
tion of two or more transmitters together on one
coaxial cable without causing intermodulation
distortion due to the signal from one transmitter
affecting the output stages of the other transmitter.
Hybrids are also required between transmitters
and receivers, depending on the application. The
hybrid circuits can, of course, cause large losses in
the carrier path and must be used appropriately.
Page 3–18
Unblock Trip
(Trip 2)
D
f f (f + f)
C H C
High/low-pass and band-pass networks may also
be used, in some applications, to isolate carrier
equipment from each other. Several typical appli-
cations of hybrids are shown in the following dia-
grams, Figures 3–21 through 3–25. A summary of
some of the more important application rules are
given below:
1. All hybrids in a chain should be resistive
type hybrids except the last hybrid, that is,
the one connected to the line tuner.
2. The last hybrid in the chain should be the
reactance type hybrid or a skewed type.
3. When applying transmitters to reactance
type hybrids, the frequency spacing
between the widest spaced transmitters is
about 4% for frequencies below 50 kHz
and 6% for frequencies above 50 kHz. If
this rule is not followed then the hybrid
cannot be adjusted to provide the best pos-
sible isolation between all transmitters.
4. When applying transmitters and receivers
to a reactance type hybrid the frequency
spacing between the transmitter group and
receiver group is of no concern; however,
all the transmitter frequencies must meet
the frequency spacing rule above. This rule
is based on receivers with high input
impedance.
5. When the last hybrid is a skewed type then
the receiver port should be terminated with
a 50Ω resistor to obtain proper isolation.
A few guidelines follow in order of importance:
1. The hybrids should be arranged with the
lesser losses in the transmitter path and the
greater losses in the receiver path to pro-
vide more transmitter signal levels onto the
power line.
2. Transmitters that are used with wide band-
width channels should be arranged with
lower losses and those of narrower band-
widths should have the higher losses.
3. Narrow band systems are not as susceptible
to noise as wider band systems are, there-
fore they can tolerate the higher loss.
If possible, transmitters used for common applica-
tions should be arranged for equal attenuation.