Adjacent Channel/Block Combination

COM-TECH has exploited the of Adjacent Channel/Block Combination thanks to innovative techniques: DualCross and XLine Filters, MultiStep Hybrid Couplers, and an improved Manifold combination.
The combination of Adjacent Channels/Blocks requires Mask-Combiner configuration, together with Manifold or Balanced Combiners:
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Manifold Starpoint Balanced
4-Pole Yes
5-Pole Yes
6-Pole No
4-Pole A.N.T. Yes
6-Pole XLine No Yes
7-Pole XLine No Yes
6-Pole DualCross No Yes
8-Pole DualCross No Yes
7-Pole (DAB) No Yes
6-Pole DualCross (DAB) No Yes
8-Pole DualCross (DAB) No Yes

Notes

  • Adjacent Channel/Block Combination can be implemented independently of the required Mask (e.g.: Critical), it does not necessary require 8-Pole Filters
  • Adjacent Channel/Block Combination involves an increased dissipation for the filters reflecting the adjacent channel; for these modules, Narrowband power ratings must be consequently reduced
  • No-Mask-Combiner configuration, and Starpoint or Stretchline Combiners do not allow the combination of Adjacent Channels/Blocks

Chain Combiners

Combiners can be connected together to realize Chain Combiners with different techniques (Starpoint, Manifold, and Balanced) and with different cavity sizes and different number of poles, allowing to optimize the Combiner chain.
A chain of n Balanced Combiners has n Narrowband inputs and one Wideband input, which can be further used to extend the combiner combination capability:
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Wideband Port Use Combination Future Expansion Combiner Cost
Not used, Terminated with Load 0 channels added
(can be added later)
In the Wideband port or in the Output (antenna) side Most Expensive
Filter, Starpoint, Manifold Combiner, or existing Combiner 1, 2 or more extra channels added In the Output (antenna) side Cheapest

Balanced Combiners also allow to be extended at a later stage. The new channels can be added inserting a new combiner in two possible different positions into the Combiner chain:
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Position New Combiner required Advantages Disadvantages
In the Output (antenna) side Balanced Combiner The new Balanced combiner can be optimized to accept the existing channels Requires major mechanical work.
The new Combiner is generally bigger
In the Wideband port Filter, Starpoint, Manifold, Balanced Combiners Requires minor mechanical work.
The new Combiner is generally smaller
The Wideband of the existing combiner port must accept the new frequencies and withstand the increased power

Combiner Request Guidelines

The system engineering of a Chain Combiner requires several data to be collected from the Customer.
When requesting a quotation please specify as much information as possible, completing the following guideline table:
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Data Values
Operating band,
Standard and Bandwidth
Include as much information as possible on the standard
Eg.: UHF DVB-T2 8 MHz
Channels to be combined Channel list with: channel number or frequency, RMS or Sync Peak Power input power of each channel.
If a preferred order is requested, please specify the channel list from the farthest to the closest to the output (antenna)
Eg.: 21 (1.5 kW RMS) – 23 (1 kW RMS) – 24 (2 kW S.P.)
Adjacent Channel Combination
(Yes / No)
Adjacent Channel Combination requires Mask-Combiner configuration, together with Manifold or Balanced Combiners.
In case of FM Combiners specify minimum frequency distance.
Constant Impedance requested
(Yes / No)
Constant Impedance requires a Balanced Combiner, with its Wideband port not used (terminated with Load)
Existing Combiner to be added
(Yes / No)
The presence of existing Combiner to be extended requires a Balanced Combiner, with its Wideband port used to add existing channels
Existing channels to be added
(if any)
Channel list with: channel number or frequency, RMS or Sync Peak Power input power of each channel.
Eg.: 31 (2.5 kW RMS) – 33 (1.5 kW RMS) – 44 (2.5 kW S.P.)
Inputs: Connectors and Directional Couplers Inputs Connectors type. If Directional Couplers are required, please specify the number of probes per each input
Eg.: 3x EIA 1+5/8” Flanged, 3xDirectional Couplers with 1xFWD and 1xRFL
Output: Connector and Directional Coupler Output Connector type. If Directional Coupler is required, please specify the number of probes
Eg.: EIA 3+1/8” Flanged, Directional Couplers with 2xFWD and 2xRFL
Forced Air Cooling or Liquid Cooling accepted
(Yes / No)
Liquid Cooled Combiners require transmitters to have to liquid cooled and to connect their system to the Combiners
Environmental Conditions Specify transmitting site altitude, room temperature, expected maximum combiner body temperature, etc.

Wideband Power and Peak Voltage

Wideband Input Power
COM-TECH Balanced Combiners have been dimensioned to withstand the overall output power even in Wideband mode (the Wideband input power having a double impact on hybrid couplers), thus making the calculation of the Wideband Input power extremely easy:

WB Input Power = Maximum Output Power – Sum of NB Input Powers

Voltage Peaks
COM-TECH Balanced Combiners have been dimensioned to widely sustain the increased voltage peaks caused by the vector composition of several signals (up to 10 channels).

Wideband Tuning Optimization

The Return Loss on the Wideband port can be optimized either for the best value on specific channel(s) (at the expense of reducing the performances outside the given frequencies), or to reach the best tradeoff value on the whole operating band.

Wideband Tuning Features
Channel Optimized Best Return Loss values on the specified channel(s)
(reduced performances outside)
Whole-band Optimized Best Return Loss tradeoff on all operating band

Combiners with MultiStep technique, available on DF Series UHF Balanced Combiners, have unparalleled Return Loss performances, allowing an almost optimal Return Loss value on all the operating band.

Return Loss

Tuning data reported on the Datasheets refer to one single Balanced Combiner module.
The combination of several Balanced Combiner modules involves a derating of the overall Return Loss, influenced by the number of combined channels, channel order and assortment, and adjacency. For basic reference, and in case Channel-Optimized Wideband tuning (see above), the following table is provided:

No. of Modules Overall Return Loss (VSWR)
1 26 dB (1.11)
2-5 25 dB (1.14)
6-8 24 dB (1.16)
9-10 23 dB (1.18)

Insertion Loss

Tuning data reported on the Datasheets refer to one single Balanced Combiner module.
The overall insertion loss of a Balanced Combiner Chain is the sum of the insertion loss of the single module, increased by the sum of the Wideband insertion losses of the following modules:

 I.L. (Overall) = I.L. (Single Module ) + n x I.L. (Wideband)