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Second Generation IR Digital Audio Transmission IC Chipset
Achieves CD Quality Audio
CXD4016R, CXD4017R, CXA3668N
In 2001, Sony developed the DIAT (Digital Infrared Audio Transmission)
system that transmits CD quality audio through space using infrared light,
and in 2004 this system was standardized as the IEC61603-8-1 international
standard. Now, in preparation for the increasing popularity of DIAT, Sony
has developed a second generation DIAT chipset, consisting of the
CXD4016R, CXD4017R, and CXA3668N. Compared to the first generation
chipset, this chipset features integration of the PLL circuit, lower power
through a reduction in the size of the chips, and smaller packages. |
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CXD4016R |
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*Transmission digital signal processing
IC with integrated PLL
circuit |
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CXD4017R |
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* Reception digital signal processing
IC with integrated PLL circuit |
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CXA3668N |
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* Reception analog signal processing
IC with integrated AGC
and BPF circuits |
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With the development of this chipset, IR
digital audio transmission systems (DIAT)
stipulated by the IEC61603-8-1 international
standard can now be implemented
easily and at lower cost than was possible
with the first generation chipset. While the
first generation chipset could only support
high-end products, this new chipset can be
used in popularly priced products and contribute
to more widespread use of the
DIAT system.
DIAT applications include wireless headphones
and wireless connection of rear
speakers in home theater systems. |
Coexistence with Other IR
Systems |
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In systems that use IR, the IR subcarrier
frequency band occupied by each application
is determined in advance to avoid
interfering with other IR systems. (See figure
1.) The 3 MHz to 6 MHz band is allocated
to the DIAT system, and DIAT
applications can be used at the same time
as other IR equipment such as IR remote
controllers. |
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Two Transmission Modes |
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There are two transmission modes, full-band
mode and half-band mode, provided
for DIAT systems, and depending on the
application, one or the other may be chosen.
(See table 1.)
Full-band mode is a mode in which the
allocated band can be used directly, and
half-band mode divides the allocated band
into two bands and allows them to be used
independently. (See figure 2.) Full-band
mode supports the transmission of 24-bit
stereo signals, and thus makes high-quality
audio transmission possible. In contrast,
half-band mode can transmit 16-bit
stereo signals, and thus can transmit audio
signals with quality equivalent to that
of CDs. It also has the advantage that when
used with the same transmission power as
full-band mode it extends the service distance
by roughly a factor of 1.4. |
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Simple System Structure |
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Figure 3 shows an implementation of a
transmission system and figure 4 shows
an implementation of a reception system.
Since digital audio signals can be transmitted
without compression, and since
microcontroller support is not required, a
digital audio wireless transmission system
can be implemented with an extremely
simple structure. In the transmission side,
the second generation IC reduces costs and
mounting area by the integration on the
same chip of the PLL circuit, which was
implemented externally in the first generation
IC. Furthermore, in the reception
side, the chip size of the CXA3668N has
been reduced allowing the 28-pin SOP
used in the first generation chip to
be replaced with a 24-pin SSOP, thus
reducing the package area to about 1/3 of
that of the previous generation and allowing
mounting areas to be reduced in end
products. |
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•••• Mr. MIYAMORI ••••
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The problem that concerned us
the most at the start of development
was how to increase the
popularity of the DIAT method. In
addition to there being a strict
deadline, the schedule for the end
product that would use this
chipset was already fixed and we
designed this chipset with only a
single digital systems designer
on the team. This made the design
particularly difficult. However,
those difficulties spurred us on to
greater efforts, and I am confident
that we have succeeded in designing
a product that will fully
satisfy our customers. I strongly
urge you to consider this product. |
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See
all articles with figures and tables.  |
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Vol.46 |
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