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Tuner enables broadcast TV in European, N. American handsets

Posted: 16 Jun 2005 ?? ?Print Version ?Bookmark and Share

Keywords:mt2260? tuner? microtune?

Tuner complies with MBRAITuning in TV signals for mobile handsets is significantly different than tuning in voice and data packets. While cellular phone receivers single out narrowband signals, TV tuners need to receive across a wider band, filter out unwanted interference, and not consume a lot of power. For a stationary TV, a 1W tuner is considered a low-power device. For mobile TV, power consumption would have to be taken down nearly two orders of magnitude.

Enter Microtune. This is a company that was founded on the technology for silicon TV tuners. They have been heavily involved with European manufacturers developing products for DVB-T, the European digital TV standard, and they are deep in the trenches with manufacturers working on TV systems for use in automobiles. These automotive systems face similar challenges to mobile handset TVs, including handling interference and receiving signals while in motion. But the mobile handset offered additional challenges, such as overcoming the interference of the nearby power amplifier, and not draining the handset battery.

DVB-H is a standard developed for mobile TV over broadcast; it is built on top of the DVB-T standard, and allows for high-quality full-motion TV on a smaller viewing screen. This approach to delivering TV to a mobile phone is gaining traction, with companies like Siemens, Nokia, and Samsung developing prototype phones and testing them in field trials. In the US, Crown Castle has acquired a license for L-band spectrum to support North American DVB-H services, and is currently offering field trials of its service.

For handset manufacturers, the bottom line is that the first broadcast DVB-H TV signals for handsets will either be in the 470MHz to 890MHz range in Europe or in the 1,670MHz to 1,675MHz range in North America. This is a bit of a nuisance for system designers, who would need to build one system for Europe and another for North America. With clients on both continents, Microtune realized early on that "the first thing we needed to do was develop a dual-band tuner to enable design flexibility," explains Albert Taddiken, COO of Microtune. "With a common design and a common set of software, manufacturers can simply use the appropriate input components for the band in which their product will be operating."

The design team recognized that the most efficient way to implement their new tuner was to use an integrated design, one that required no external low noise amplifier (LNA) or transformer balun. The result was the company's MT2260 multi-band silicon tuner that is compliant with the Mobile and Portable DVB-T/H Radio Access Interface Specification (MBRAI).

But what about the power? Recognizing the need for low power with power-down and sleep modes, the team took on the task of optimizing each block of the design for power consumption. The result is 20mW to 40mW typical consumption in viewing mode. "We have built in programmability that allows the device to be run at higher power consumption when signal reception environment is more severe," explains Taddiken. DVB-H transmits different channels in bursts, known as multiplex broadcasting using time slicing, so the device powers down to 9mW in between bursts and slips to a few hundred?W in sleep mode when the TV functionality is not in use.

In terms of interference, you cannot use a fixed filter (like in cellular receivers) and expect to reject interferers across the TV band. The challenge was to design a tuner that could filter out interferers without blowing the power budget. In their case, the team at Microtune is using a specialized filter, and they have dubbed the approach "ClearTune" technology.

As the mobile TV market grows in Europe and North America, the focus of early generation handsets will be functionality, power, and cost. By hitting the MBRAI specs, the frequency bands for both markets, and addressing power issues, this new tuner from Microtune is definitely worth a close look.

The MT2260 is priced at $5.00 each in 10,000-piece quantities. It is sampling now.

- Janine Love

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