Satcr Overview - Deviser S7200 User Manual

Part III: Background and Concepts
9-3

SaTCR Overview

Unicable LNBs (see below) receive Ku-band satellite signals the same way that traditional LNBs do. The
difference is the addition of SCR and MCU chips.
When the receiver's low-noise amplifier receives satellite signals, they may be of four different frequency
bands: low- and high-LO vertical polarization (V/L and V/H), and low- and high-LO horizontal polarization
(H/L and H/H). These signals pass the bandpass filter to filter out useless signals. When signals with low LO
and high LO are mixed, the result is converted to the L band. These L band signals are input into a circuit
matrix switch.
Some components, such as the SaTCR-1 (Satellite Channel Router), target the LNB, multi-switch, and SMATV
market. The SaTCR-1 can translate a transponder to any location in the satellite bandwidth (950~2150MHz).
With multiple SaTCR devices coupled with band-pass filters and an RF matrix, it is possible to combine
transponders from different polarizations and bands on a single coaxial cable.
In order to receive all available channels in the Ku-band using a conventional LNB, a set top box has to
select the polarization and the local oscillator corresponding to the desired transponder. The polarization is
selected by changing the voltage of the LNB supply (13V for vertical, 18V for horizontal). The local oscillator
is selected by adding or omitting a 22kHz tone on the LNB supply. (When the 22kHz tone is present, the
highest LO is selected). The local oscillator frequency can be 9750 or 10600 MHz, depending on the
location of the transponder. If the respective transponder is in the lower part of the spectrum (<11700MHz)
the 9750MHz LO is selected; otherwise the 10600MHz LO is selected. The tuner must be set to the correct
frequency using the following formula:
F = F - F
tuner transponder LO
With a LNB-integrating SaTCR-1 device, transponders are selected (polarization, LO selection and
frequency translation) through a single DiSEqC command, ODU_ChannelChange.
The first stage of a SaTCR LNB (up to the matrix) is similar to a conventional LNB. Consequently, the
transponder frequency at the input of a SaTCR device is the same as F
F = F – F
satcr_input transponder
Then, the SaTCR device should translate the transponder inside the bandwidth of its associated band-pass
filter. To perform this operation, the SaTCR VCO must be set according to the following formula:
F = F + F
satcr_voc satcr_input
In addition, SaTCR LNB includes new features that allow auto-detection of its settings.
112
LO
= I F – F I + F
bpf transponder LO bpf
with a classical LNB:
tuner