Satellite TV installations use
a set-top box (STB) that works
with a remote low-noise block
(LNB) converter at the antenna
so the Ku band signals (10.95 to
14.5 GHz) are downconverted
to the 950- to 2150-MHz range,
making them more friendly to
the coax connection between
the LNB and STB. But this creates
compromises in multi-set
installations, as extra wiring is
often needed. Any other special
arrangement typically results
in a more complex and expensive
installation.
The TDA20136 dual tuner
from NXP Semiconductors
solves the problem (see the figure).
It integrates a dual eightphase
shift keying (8PSK) satellite
tuner with some highly
desirable pre-tuner circuitry
to create a platform that is
more flexible in diverse installation
scenarios without any
hardware changes. This will
dramatically reduce design cost
and complexity.
The pre-tuner circuitry provides the
flexibility that allows set-top boxes to use
either a single cable input, splitting the
signal internally to the device, or legacy
mode with two separated inputs. In both
cases, an optional dual loop-through
function is available.
The single-input setting is most commonly
used when the set-top box is used
with a single-cable reception outdoor
unit (ODU). In this case, signals from
multiple LNBs are multiplexed onto a
single cable at the ODU. This single cable
can then provide the required signals for
many STBs in a single home or multidwelling
unit (MDU). With no hardware
changes, an STB using this IC can also
be used in an installation with a legacy
multi-LNB, multi-cable ODU. In this legacy
installation, each tuner gets its signal
from a separate cable.
“The industry trend towards singlecable
reception (SCR) has the potential
to dramatically reduce installation costs
because there are fewer cables to install,
but implementing SCR circuitry in a settop
box using a standard satellite tuner is
complex and expensive,” said Tim Kirstein
of NXP Semiconductors. “We have created
the TDA20136 with the highest levels
of RF integration to directly address these
problems, while also providing the settop
box maker with the flexibility to be
backwards-compatible with traditional
multi-LNB, multi-cable ODUs.”
The TDA20136 system is based on the
company’s proven dual-tuner technology
with its CX24132. This unique secondgeneration
complete dual 8PSK tuner
offers outstanding performance and low
power consumption. It includes all of the
necessary low-noise amplifiers (LNAs),
voltage-controlled oscillators (VCOs),
synthesizers, mixers, and filters for common
applications. Additionally, its small
size (7 by 7 mm) enables system designers
to reduce the size of front ends. Production
will begin this month.
LOUIS E. FRENZEL
NXP SEMICONDUCTORS
www.nxp.com