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RFICs
Benefits of CSS technology in European
DBS systems
Traditional satellite system installations require a separate cable from the
satellite outdoor unit to each STB and to each tuner in each STB. Thus, PVR
STBs and multituner STBs require multiple cables per box. Installation upgrades
to PVRs or adding STBs requires new cable drops, adding cost to the
equipment and installation for the consumer. Channel stacking switch (CSS)
technology dramatically reduces the cost of installation by delivering multiple
satellite channels on a single cable within the home. This article addresses
system design challenges and performance requirements of European DBS
systems using CSS technology.
By Bill Windsor and Peter Wong
I
n traditional European digital broadcast
satellite (DBS) installations, each tuner is
connected directly to the satellite ODU with a
dedicated coaxial cable. Cabling must be added
when additional STBs or PVR STBs are
added.
Installing additional cabling has many
drawbacks:
 Truck rolls are expensive.
 Wiring and installation is complex and
time consuming.
 Multiple cables are required around the
dwelling.
 Homeowners’ associations or local
ordinances may restrict access.
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CSS technology and solution
The drawbacks are eliminated by channel stacking switch (CSS) systems. Figure 1
illustrates how CSS technology operates: CSS
translates, filters and performs frequencydivision multiplexing (channel stacking) onto
a single cable, based on channel requests from
multiple STBs and tuners connected to that
cable. A single cable drop from the ODU
provides each STB tuner with a dedicated
frequency band, eliminating the need for
multiple cables. Figure 1 shows a multiswitch
CSS product and application, and Figure 2
shows an integrated LNB CSS application.
Figure 2 shows the signal flow diagram in the
satellite ODU’s low-noise block (LNB). Satellite signals are received by the satellite dish, amplified by the low-noise amplifier (LNA), and
mixed down to IF. In European DBS systems,
the received satellite signals are downlinked in
two polarizations, horizontal (H) and vertical
(V) over the 10.7 GHz to 12.75 GHz frequency
range. Since STB tuners can only tune over
1.2 GHz of bandwidth (950 MHz to 2150 MHz)
and the downlinked satellite signals cover
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Figure 1. European DBS system with channel stacking technology. CSS technology enables a single
cable to drive multiple STBs and tuners.
www.rfdesign.com
March 2007
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RF Design
703RFDF4.indd 41
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2.05 GHz of bandwidth, the incoming signal
is split into two bands (low and high) and each
band is down mixed within the 950 MHz to
2150 MHz IF bandwidth.
European legacy STB ports are passthrough ports that accept the IF input signal,
amplify it, and enable channel selection from
the European legacy STB. This functionality
enables installs for current satellite TV users
who wish to keep their existing STBs.
A block diagram of a six-stacked channels
reference design is shown in Figure 3. The
example CSS system shown accepts four
1 GHz inputs, which represent the full signal
bandwidth of one European DBS satellite.
The signals are stacked onto the 950 MHz to
2150 MHz IF band. A particular transponder
of interest is converted to the desired user
band and passed through a dedicated SAW
filter. Each IC can process three channels and
the outputs of both ICs are combined using a
printed structure on the printed circuit board.
The RF5210 architecture can process up
to 12 stacked channels in the 950 MHz to
2150 MHz band using four CSS chips.
Figure 4 shows the modulated CSS
single cable output within the 950 MHz to
2150 MHz band (L-band tuning frequency
range for European STBs), with six user bands
selected from the satellite inputs to drive six
individual tuners (up to 12). Each user band
(each tuner) can independently tune to any
satellite transponder.
The CSS chips achieve excellent integrated
phase noise performance of substantially less
than 1 rms, which is negligible when added
to standard LNB phase noise performance.
Therefore, adding CSS functionality results
in virtually no degradation in video lock and
video continuity performance of the LNB.
The traditional universal quad LNB
includes a built-in multiswitch and four
outputs that requires four cables. The CSS
LNB design can eliminate the multiswitch and
transmit two to 12 outputs down one cable, reducing overall BOM and installation costs.
CSS technology requires an extension to
the existing communications protocol between the STBs and the ODU. CENELEC,
the European Committee for Electrotechnical
Standardization, is ratifying an extension of
the digital satellite equipment communications
(DiSEqC) standard to support the necessary
communications and enable users to send
channel requests from the STB to the ODU.
STB manufacturers have already endorsed the
emerging standard, and currently available
STBs incorporate support for CSS technology. Existing STBs enable the functionality
via firmware upgrades transmitted by the
operator on a network channel.
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Figure 2. European DBS single-family home low-noise block (LNB) configuration: 4-input, 6-output,
+ 2 legacy ports.
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Figure 3. European DBS channel stacking reference design: 4-input, 6-output, + 2 legacy block diagram.
Key specs in satellite LNB
Delivering high-quality video and audio
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Figure 4. CSS 6-output channel stacking, modulated output signal.
www.rfdesign.com
March 2007
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RF Design
703RFDF4.indd 43
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Figure 5.
entertainment requires high signal quality
and performance levels in the satellite LNB.
RF Magic architected the CSS chip to be
placed into the IF section of the LNB, to
perform complex signal processing across
>1 GHz of bandwidth, and to achieve limited
degradation to overall LNB performance.
Low noise figure: The chip was designed
to enable CSS-LNBs to have equivalent noise
figures to traditional LNBs.
Gain: The chip enables CSS-LNBs to
maintain output power levels consistent with
traditional LNBs.
Linearity: The chip was designed to enable
CSS-LNBs with virtually no degradation to
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703RFDF4.indd 44
linearity performance.
Phase noise: The chip is designed to support DVB-S2 perfomance and has excellent
phase noise performance that does not degrade
the performance of the incoming signals.
LO crosstalk: The chip implements proprietary design techniques to minimize LO
crosstalk.
Channel to channel isolation:The chip was
architected to provide high isolation to ensure
virtually no signal performance degradation.
Sample installations
To see the advantages of CSS, it is useful
to review some examples.
www.rfdesign.com
Figure 5 shows examples of a single-family
home (SFH) with one dual-tuner/PVR STB
and a single-tuner STB that is upgraded to
a dual-tuner/PVR STB with traditional
technology and with CSS technology.
Multiple dwelling
A small multiple-dwelling unit (MDU) can
be treated like the previous SFH example. For
a larger MDU, a trunked system is commonly
used (Figure 6).
Simplifying the installation of satellite TV
systems enables new revenue opportunities for
operators, installers and retailers.
CSS technology improves operators’
March 2007
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RF Design
703RFDF4.indd 45
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Figure 6.
drive for increased average revenue per user
from content sales by simplifying the
connection of additional viewing locations.
Reducing install time will result in greater
efficiency, more installs per day and customer
satisfaction. CSS technology drives reductions
in costs, which lowers consumer acquisition
and upgrade costs, and results in increased
profitability:
 Lower cost of STB upgrades and
add-ons. Upgrading a single-tuner STB to a
dual-tuner PVR or adding a new STB requires
installing additional cables. This can cost on
the order of 100 euros. In a CSS system, the
existing cable run can be used, and the installation cost for this upgrade is zero.
 Lower cost of initial installation. Cost
savings can be substantial for installations with
several STBs and tuners, which would traditionally require several cable runs from the ODU.
 Lower costs for MDUs. CSS systems
enable support of multiple tuners and STBs in
a flat by using a single cable run. Because most
European MDUs have at least one cable into
each flat, no new cabling is required.
Other benefits from CSS include:
Aesthetics: CSS system eliminates unsightly
multiple cable drops. For MDUs, CSS can eliminate multiple satellite dishes on balconies.
Self installation and upgradability: CSS
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703RFDF4.indd 46
facilitates self installations, an important factor
in free-to-air markets. Installing a traditional
universal quad or Octo LNB requires running
four or eight separate cables, compared to a
CSS LNB where only one cable is required.
Scalability: CSS systems can be cascaded
to support additional inputs and outputs and
stack more channels on the single cable.
Simplicity, reliability: Fewer cables and
connectors provide simplicity and increased
reliability with CSS installations by reducing
weather entry points.
tuner STBs and media server equipment, CSS
technology is poised to simplify and reduce
installation complexity. Reducing the need for
multiple cables to a single cable drop results
in greater customer acceptance, more efficient
installation and lower overall cost. RFD
Semiconductor processing for CSS
Peter Wong is senior applications engineer
at RF Magic for the CSS product line.
Jazz Semiconductor manufactures the
CSS chip in a robust, high reliability, and
cost-effective BiCMOS process with 30 GHz
bipolar and high density CMOS. The process
includes a variety of high-performance passive
elements for highly integrated analog and RF
products. In this design, the silicon bipolar
devices approach the performance of SiGe
devices while remaining cost effective. Passive elements include MIM capacitors, thick
top metal for inductors, and a high-performance varactor. The process meets the stringent performance and market requirements of
satellite IF signals in CSS applications.
As the European DBS market continues to
grow and expand into multiple STBs, multi-
www.rfdesign.com
ABOUT THE AUTHORS
Bill Windsor is director of product marketing at RF Magic for the CSS product line.
March 2007
3/16/2007 2:59:14 PM