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In 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.

The drawbacks are eliminated by channel stacking switch (CSS) systems. Figure 1 illustrates how CSS technology operates: CSS translates, filters and performs frequency-division 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 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 pass-through 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.

Delivering high-quality video and audio 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 linearity performance.

Phase noise: The chip is designed to support DVB-S2 performance 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.

To see the advantages of CSS, it is useful to review some examples.

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.

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' 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 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.

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, multituner 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.

Bill Windsor is director of product marketing at RF Magic for the CSS product line.

Peter Wong is senior applications engineer at RF Magic for the CSS product line.

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