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ITAS offers
in the VHF band a variety of
standard products. Our TV combiners are designed for VHF and UHF
applications and are characterized by low transmission loss end. which allows
the combining of two or more programs. According to the power
transmitter and channels, two combiner's
types are available: |
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A bridge system with a phasing line made
of coaxial feeder line. |
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A bridge system with three or four
cavities filter. |
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Both combinations.
cavities system and phasing line system.
follow the channels and their power. solving
most combining requests. |
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Description of
Phasing Line Combiner |
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The
basic combiner is composed of two 3 dB couplers.
between which two coaxial lines of different
electrical lengths. These two lines operate
in progressive waves and ensure the selectivity.
The DL different
length depends on the spacing between the
combined channels and allows to obtain on
the output all the high frequency made by
the E1 and E3 transmitter (fig 1).
The lowest part of the power, which doesn't
transmit through the output is absorbed towards
the system balancing load. The series association
of two basic combiner allows the transmission
of three programs on a same antenna (fig 2). |
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Description of
Cavities Filter Combiner |
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The principal function of the cavities combiner with bridge system is to
put together on the same output several TV channels. The basic combiner.
including two 3 dB couplers. treats simultaneously on the same output
two TV channels. Tuners tuned identically (fig 3). The basic combiner
has two inputs: one narrow band and one broadband. We provide the Fi
frequency at the narrow band input and the transmission response
combiner is similar to the transmission response filter: type
butterworth of the 6th order for the 3 cavities filters. The F2
frequency is provided at the broad band input. The transmission response
to the output is a band stop type function, it's similar to one filter
reflection response. Concerning the 3 dB couplers both inputs must
ensure signal way to the matched load which is the combiner output
impedance. Any signal which doesn't travel through the output is
directed towards the balancing load where it's absorbed. The bridge
system transmits several TV channels in series association of basic
combiner. |
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Electrical
Characteristics |
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Frequency Range |
UHF
470 MHz - 860 MHz |
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Characteristic Impedance |
50 W |
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Minimum Spacing between vision carriers |
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Cavities Combiner |
16 MHz |
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Line Combiner |
24 MHz
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Minimum Isolation Between Channels |
30
dB |
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Maximum GDT Variation in Channels |
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Cavities Combiner |
30 ns
ΔF = 16 MHz
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20 ns
ΔF = 24 MHz
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Line Combiner |
4 ns
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A bridge system with three or four
cavities filter |
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A bridge system with a phasing line made
of coaxial feeder line. |
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The cavities combiner is characterized by low
perdition loss in transmission and allows the
combination of two or more programs with a minimum spacing of two
channels. The simplicity of this combiner gives it a high degree of stability, reliability and the delay time is very short.
The phasing line system allows the combination of two or three
channels with a minimum spacing if two channels.
Both combiners follow the channels and their power; solving most combining requests. |
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Description of phasing line
combiner |
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The
basic combiner is composed of two 3 dB couplers between which are two
coaxial lines of different electrical lengths. These two lines operate
in progressive waves to ensure the selectivity. The DL
different length depends on the spacing between
the combined channels and allows to obtain on the
output all the high frequency made by the E1 and
E2 transmitter (Fig 3). The lowest part
of the power which doesn't transmit through the
output is absorbed towards the system balancing
load. The series association of two basic combiner
allows the transmission of three programs on a same
antenna (Fig 2). |
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Electrical Characteristics |
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ΔF=0.8MHz
ΔF=1.2
MHz ΔF=1.4
MHz |
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ITAS
offers a series of FM combiners which allows
the use of a single antenna with several
close FM frequency channels. The use of noble materials
enables a good insertion loss and a good attenuation
for the whole range of frequencies covered by our combiners (from
1 to 40 kW). There are two
types of combiners available: |
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A bridge system with a two
cavities filter which accepts a minimum spacing of 1.2 MHz. |
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A bridge system with a
three cavities filter which accepts a minimum spacing of .08 MHz. |
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The extremity couplings
are made with loops so we achieve an isolation between the narrow band
input and the broadband input at better than 40 dB (fig 1). The
dimension of cavities. the precision of the mechanical realization. the
utilization off it material and the treatment quality have enable to
obtain: |
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Insertion loss between
0.35 dB and 0.6 dB according to the type of combiner |
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A transmission attenuation
equivalent at 25 dB or F± 1.2 MHz to F ± 0.8 MHz. |
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This is important because
attenuation protects against the intermodulation products. |
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Function
Description |
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The main function of
the cavities combiner with bridge system is to enable the placement of
several FM channels on the same output. |
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The main function of
the basic combiner. including two 3 dB couplers is to join together
simultaneously two FM channels on the same output. Between the two
couplers, it's insert two band-pass filters tuned identically (fig 2).
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The basic combiner has
two inputs: one narrow band and one broad band. We provide the F1
frequency at the narrow band input and the transmission response
combiner is similar to the transmission response filter: type
"BUTTERWORTH" of the 4th order for the two cavities filters and 6th
order for the 3 cavities filters. The F2 frequency is provided at the
broad band input. |
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The transmission
response to the output is a band-stop type function. This function is
similar to one filter reflection response. For the two 3 dB couplers
both inputs must ensure the signal way to the matched load which is the
combiner output impedance. Any signal which doesn't travel through the
output is directed towards the balancing load where it's absorbed.
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The "bridge system"
transmits several FM channels in series association that basic combiners
follow (fig 3) allowing the transmission of several FM channels by the
association of basic combiners. |
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Electrical Characteristics |
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