NXP Develops Broadband Doherty UHF Amp

In my June 15 TV Technology column Coming: Higher Efficiency for Higher-Power Amplifiers I outlined how Doherty amplifiers work and some of the challenges designers face in using them. Last week NXP announced it had developed the industry's first full-band UHF Doherty Architecture. The new devices are targeted for UHF broadcast applications.

“We believe that the new ultra wideband variant of Doherty will have a major impact on the digital broadcast market,” said Mark Murphy, NXP's director of marketing, RF power and base stations. “Today's high-performance TV transmitters constitute serious investments, and so our customers need to implement higher efficiency solutions without incurring extra costs, and without delaying time to market. For this challenge to be met, the market needs suppliers who not only provide leading-edge products in areas such as Doherty power amplifiers, but can also offer expert application support to match. This is exactly where NXP fits in.”

The company noted that Doherty topologies offer 45 to 50 percent efficiency, which is an improvement of at least 15 percent over traditional UHF technologies that can only achieve a 30 percent efficiency. Of course, as the announcement notes, the principal challenge up until now has been how best to apply the narrow-band, high-efficiency benefits of Doherty amplifiers to a market that requires bandwidth coverage of some 400 MHz.

NXP said its new Doherty amplified is capable of operating over an ultra-wideband spectrum and that it has achieved this without an increase in the bill of materials. It’s based on NXP's 50 Volt LDMOS technology.<

NXP's Doherty solution will be available with the next 2 to 3 months. A video is available describing the technology.

This could shake up the UHF transmitter market.

The only companies I saw offering Doherty UHF TV amplifiers at the 2012 NAB Show were Screen Services, with a narrow-band amplifier, and Rohde and Schwarz, with a wide-band unit which used an undisclosed technology.

Doug Lung is one of America's foremost authorities on broadcast RF technology. He has been with NBC since 1985 and is currently vice president of broadcast technology for NBC/Telemundo stations.