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CMOS Silicon Tuners for
Large-Screen TV Sets
Introduction to Sony's CMOS Silicon Tuner Technology |
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SAW filter no longer required due to
the adoption of a low IF system |
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Low-noise/Low-distortion RF amplifier
circuit |
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Built-in tracking filter improves interference
rejection performance |
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Low phase noise PLL circuit achieves
high reception sensitivity |
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Reduction of the spurious radiation that could degrade picture quality during analog broadcast reception |
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Low power |
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As the trend towards even thinner home TV sets progresses, the need for further miniaturization
in the tuner module, one of the largest functional
components in a TV set, is increasing.
At the same time, the number of functions provided
by TV sets continues to increase, with
multi-screen display and recording capabilities,
such as hard disk and Blu-ray disc drives, now
being common. As a result, the number of models
that include multiple tuners is increasing,
thus making the need for further miniaturization
in tuner modules even stronger.
The high-functionality silicon tuner IC, which
can replace the CAN tuner (see photograph
1), which is implemented with many discrete
components such as coils and variable capacitance
diodes (varactor diodes), is now seen as
the desired solution for implementing miniature
tuner modules. Although silicon tuner ICs are
now used in cellular phones for One Seg small
screen TV broadcast reception to achieve the
required ultraminiaturization, when it comes to
use in TV sets, creating a silicon tuner IC that can provide the performance required to achieve
high picture quality and the performance to satisfy
the requirements of the many TV broadcast
standards used around the world is an exceedingly
difficult technological problem.
Sony has now created, using a CMOS process,
a silicon tuner with superlative sensitivity and picture quality performance for use in large-screen
flat panel TVs. This device makes it
possible to design a miniature tuner in an area
1/10 or less that of existing Sony tuners.
This CMOS silicon tuner achieves sensitivity
and picture quality performance equivalent to
or better than those in current high-performance
tuners used in large-screen TV sets. Sony's TV
tuner module and IC design experts held many
discussions to overcome the challenges posed
by this difficult technology development and
succeeded in developing the industry's first
silicon tuner that can receive both analog and
digital broadcasts. Sony has also announced
the “BRAVIA” series of LCD TVs that use
this IC.
*: “BRAVIA” is a registered trademark of
Sony Corporation.
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 What is a Tuner? |
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A tuner is one of the basic building blocks that
makes up a TV set, and at least one is included
in every TV set.
TV sets, as one realizes from the origin of the
abbreviation (television), receive broadcast
signals sent from distant broadcasting stations,
extract the video and audio signals from the
broadcast signal waveform, and then display the video on an LCD screen while outputting
the audio from speakers.
The role of the tuner is to "tune" (i.e. select) the
channel that the user wants to watch from the
many broadcast waveforms that reach the TV set
after being collected by the home antenna.
Functionally, a tuner could be called a "variable
frequency filter". The range of frequencies
received, however, is extremely wide: from 50
MHz to 800 MHz, and the tuner must extract
an arbitrary 6 MHz band from this range.
Furthermore, the suppression of adjacent channels
must be at least 50 dB. Another problem is
that the TV set receives signals from stations
both near and far with power levels ranging
from 1 μV to a few volts, and must amplify
these signals without distortion.
To make the frequency variable in this manner,
at the start of TV broadcasting, tuners were
constructed by switching a coil contact or using
a variable capacitor. (See figure 1.) At that
time, the channel selector was a dial that was
turned, and was also called a mechanical (or
rotary) tuner.
The varactor diode had been developed by the
latter half of the 1970s and electronic tuning
became practical. This made possible the current
form of the TV in which the channel is
selected by pressing buttons or using a remote control.
In the 30 years since then, although there have
been some advances in tuner modules, such as
certain sections being implemented as ICs, there
has been no change in the basic form.
In this article, we introduce the points that
allowed the extremely technologically difficult
tuner function to be implemented using
solid state devices and what problems had to
be resolved to achieve that. |
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| Implementing the Functions Required in a Terrestrial TV Tuner in a Single Chip |
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As we mentioned previously, tuners use the
superheterodyne method, in which the frequency
is converted and then passed through a fixed
filter to amplify the weak signal that comes from
the antenna, control the gain, and implement a
variable frequency filter.
Sony has now integrated the circuits required
to form a superheterodyne receiver on a single
chip: an RF amplifier, an RF filter, a frequency
conversion mixer, a frequency conversion local
oscillator, a frequency control PLL, an IF (intermediate
frequency) filter, and an IF amplifier.
(See figures 2 and 3.) |
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Photograph 1 : Example of an Existing Tuner Module
The marked section corresponds to the silicon tuner Sony has developed.
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Figure 3 : Chip Layout
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 Features of this Tuner |
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See
all articles with figures and tables.  |
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Vol.56 |
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