Newtec Proprietary
Confidentiality: Unrestricted
R3.2_v1.0
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Feature Descriptions
MDM9000 Satellite Modem
16.3 Equalink® 3
Predistortion is applicable for a single carrier per transponder scenario.
As shown on the figure above, a satellite payload contains an input multiplexing (IMUX), a traveling
wave tube amplifier (TWTA), and an output multiplexing (OMUX) filter. The IMUX filter selects the
input frequency band of your transponder (which is often a bit wider than your carrier). The TWTA
amplifies your signal. A side effect of this amplification is frequency components generated outside
the initial signal bandwidth.. Therefore, the OMUX filter cuts away unwanted frequencies to avoid
interference in other frequency bands. Because the average power of the signal arriving at the
TWTA varies (e.g. due to rain in the uplink), a pre-gain stage is included in most payloads,
performing automatic level control (ALC) which keeps the drive level of the TWTA constant.
The goal of Newtec's Equalink 3 technology is to achieve the most efficient communication. At first,
efficient communication implies bandwidth efficient communication. To get most out of your
transponder, your carrier bandwidth should approach the bandwidth of the IMUX/OMUX filters.
Because these filters operate at very high frequencies in extreme conditions, imperfections in the
filter response introduce linear distortion into your signal.
Linear Equalink 3 will compensate for this linear distortion so that you can extend your carrier
bandwidth.
Secondly, efficient communication implies power efficient communication. To get most out of your
transponder, your carrier signal should get amplified as much as possible by the TWTA, which is
achieved by increasing the drive level of the TWTA., Equalink 3 can compensate for the Non-Linear
distortion that is introduced by the Non-Linear amplification, so that you can extend the drive level.
Summarizing, Equalink 3 optimizes the satellite link performance by counteracting distortion effects
(linear and non-linear distortion) in a satellite link.
The performance of Equalink 3 depends on many factors (the type of TWTA and its drive level, the
characteristics of the IMUX and OMUX filters, the uplink and downlink noise, the characteristics of
your signal, ...).
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