Filtros Hechos por MFC

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Example with a UHF filter of a pay TV operator: The left picture shows the whole CATV
spectrum without any filter. The right picture shows the result of using a low pass filter
with a cut-off frequency of 296 MHz.
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The new catalogue by MFC gives an extensive overview of all available filters made by MFC. The
catalogue can also be downloaded directly from their website: www.microwavefilter.com
tive impact on neighbouring
frequencies. In addition, receivers
and other active elements
within the system are
at risk of malfunctioning due
to interference.
The trick now is to filter
out those unused frequency
ranges that carry the interfering
signals.
Existing signals can be filtered
in a number of different
ways. For one, it is possible
to filter out signals above
and/or below a certain specified
frequency. Low-pass and
high-pass filters are used to
that end. A low-pass filter
allows all frequencies below
the cut-off frequency, while a
high-pass filter lets through
all frequencies above a set
cut-off frequency. Unwanted
frequencies that are outside
the cut-off frequencies are
highly attenuated, whereas
the target frequency range
comes through with minimal
attenuation.
Now if you combine a highpass
filter with low cut-off
frequency and a low-pass
filter with high cut-off frequency
it is even possible to
only allow a single frequency
range through the filter setup.
The correct term for such
a configuration is band-pass
filter.
If, on the other hand, a
low-pass filter is used in conjunction
with a high-pass filter
that has a higher cut-off
frequency, only the centre
frequency space is filtered
and what we get is a socalled
reject filter.
Then again, what’s the use
of all those filters? To start
with, they allow providing
individual frequency bands
to different receivers without
those receivers having to
share frequency bands. SCR
(Single Cable Routing) distribution
setups, for instance,
make use of this approach,
with up to eight receivers
having independent access
to all satellite channels via a
single cable that is led from
one wall outlet to the next.
In such a configuration, each
receiver is assigned a dedicated
frequency band with
a central router modulating
the required transponder
onto the corresponding frequency
band.
Network operators, on
the other hand, use filters
in analog CATV networks
as well to make sure customers
with less expensive
subscriptions cannot receive
premium channels. Those
channels are usually transmitted
on higher frequencies
and a sealed low-pass filter
at the transfer point just outside
the house or apartment
prevents those subscribers
from watching channels they
don’t pay for.
The most important reason
for installing filters,
however, can be found in the
fact that neighbouring signals
are generally prone to
interference from each other.
Unlike the number of different
applications and uses
sharing the same resources,
the frequency range cannot
be increased at random
and has to be accepted as
a given, with all its capacity
constraints. Even very strict
technical regulations and
mandatory frequency charts
cannot do much in terms of
interference prevention.
A prominent everyday example
is interference in the
DVB-T/T2 and ATSC range
caused by LTE signals. As
far as the regulator is concerned,
all applications
should work side by side
in the frequency spectrum
without doing harm to each
other by using only those
frequencies that have been
specifically sat aside for each
application.
We all know too well, however,
that in the real world
it’s often an entirely different
story.
Generally speaking, highfrequency
interference can
by caused by a number of
different phenomena.
As far as receivers are
concerned:
• Interference from neighbouring
frequencies
• Interference in the IF
(intermediate frequency)
• Interference in the LO
(local oscillator) frequency
Interference can also be
caused at the transmitting
end:
• In addition to the desired
emission frequency,
neighbouring frequencies
may be affected by unwanted
emissions that are
caused by the modulator.
• Harmonics emissions
• Interference caused by
intermodulation
When it comes to selecting
an appropriate filter it
is paramount to understand
all parameters given by the
manufacturer. Listed below
are the most important of
them:
• Attenuation
Attenuation is measured
in decibels and indicates
the level by which the input
signal is decreased. To find
out the exact attenuation
the signal level is measured
first at input and then again
at output, with the resulting
difference in decibels (dB)
being the achieved attenuation.
• Bandwidth
This parameter indicates
the bandwidth of a bandpass
filter, that is to say the
frequency range that passes
through the filter with a relative
insertion loss of 3 dB or
less.
• Cut-off frequency
This is the frequency that
triggers either the high-pass
New High-Frequency Filters by MFC
for the C-Band
Model 18253 - C-Band (INSAT) Transmit Reject Filter
• This TRF provides deep rejection of the transmit band with minimal effect on the
receive band.
• Ideal for INSAT and other Region-Specific Receive Applications
• Alternate Flange Configurations are Available Upon Request
Pass band
4.5 - 4.8 GHz (C-INSAT Downlink)
Insertion Loss
0.50 dB Max
VSWR
1.30:1 Max
Reject Band
6.725 - 7.025 GHz (C-INSAT Uplink)
Rejection
80 dB Min
Operating Temperature Range -10°C to +60°C
Flanges
CPR229G
Dimensions
3.95” x 3.88” x 2.75” (100mm x 98mm x 70mm)
Finish
Gloss White Lacquer
Model 18323 - C-Band (INSAT) Receive Reject Filter
• Same as before but rejection of the receive (Downlink) band
Passband
6.725 - 7.025 GHz
Insertion Loss
0.10 dB Approx.
VSWR
1.22:1 Max
Reject Band
4.5 - 4.8 GHz
Rejection
80 dB Typ
Flanges
CPR137/CPR137G
Dimensions
5.00“ x 2.69“ x 1.94“ (127mm x 68mm x 49mm)
Finish
White Lacquer
Model 18506 - Multi-Purpose C-Band Transmit Filter
• This Uplink filter not only rejects the entire receive band (below 4.2 GHz), but
it also rejects transmissions from other potential sources of interference etc., that
RRFs do not.
• Ideal for use in high-density transmit paths, like:
Wireless Services (Point-Multipoint) 4.55 - 4.9 GHz
Maritime & Aeronautical Radio Navigation 4.2 - 5.6 GHz
Broadcast Auxiliary Services
6.95 -7.15 GHz
• Ideal for all “standard band” C-Band Uplink Applications
• Easy bolt-on installation and no power supply required
Passband
5.925 - 6.425 GHz
Passband Loss
0.3 dB Max
Passband Return Loss
17.7 dB Min
Rejection
50 dB Min @ 5.625 GHz
40 dB Min @ 6.725 GHz
Power Rating
400 Watts
Flanges
CPR137F
Dimensions
9.50” x 2.69” x 1.94” (241mm x 68mm x 49mm)
Finish
Gloss White Lacquer
174 TELE-audiovision International — The World‘s Largest Digital TV Trade Magazine — 11-12/2013 — www.TELE-audiovision.com
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