12 December 2011

Cree licenses key Doherty amplifier patents to RFHIC

Cree Inc of Durham, NC, USA has announced a non-exclusive worldwide license agreement with RFHIC Corp of Suwon, South Korea, which makes gallium nitride (GaN)- and gallium arsenide (GaAs)-based active RF & microwave components and hybrid modules for telecom and broadcast markets), that provides access to Cree’s Doherty amplifier-related patents.

Cree says that its novel Doherty architecture can serve as the foundation for advanced 4G base stations that are substantially more efficient than conventional designs. 4G mobile data networks are being deployed around the world to address the burgeoning demand for mobile broadband services.

“From our early work in maximizing the efficiency of silicon LDMOS amplifiers to our current initiatives using GaN-based devices, Cree has successfully developed innovative circuits that enhance the performance of the classic Doherty architecture,” says Jim Milligan, Cree’s director of RF.

Cree says that, with its advanced circuits, amplifier efficiency can be increased by as much as five percentage points when conventional silicon LDMOS or GaAs transistors are used. The improved performance can help to meet the stringent efficiency and linearity requirements of upcoming 4G LTE base stations, and related wireless systems, that use high peak-to-average ratio signal modulation. When these circuit innovations are implemented using Cree’s high-frequency, high-power GaN high-electron-mobility transistors (HEMTs) and the latest-generation digital pre-distortion systems, the resulting efficiency improvements can be up to 15 percentage points greater than that achieved by a conventional Doherty amplifier implemented with silicon LDMOS, says the firm.

The Doherty amplifier is a fundamental RF amplifier architecture invented by William Doherty in 1936 using vacuum tubes, but modern implementations use power transistors. The fundamental Doherty architecture uses two parallel, equal power split transistors, a carrier amplifier transistor for low-level signals and a peaking amplifier transistor for high-level signals. The fundamental, equal power split Doherty architecture offers up to a 40% improvement in efficiency over traditional non-Doherty Class A/B approaches. Cree says that interest in Doherty amplifiers has grown with increased demand for higher-efficiency systems employing digital modulation formats, such as those used for 3G W-CDMA networks. Online applications including video chat and streaming video are driving a need for still higher-efficiency amplifiers to support 4G LTE systems.

“Cree innovations in Doherty amplifier technology can set the standard for the newest generation of 4G network deployments requiring high-efficiency macro and pico cell base stations,” Milligan says. “Cree’s advancements on the fundamental two-transistor, parallel Doherty architecture can yield significant efficiency improvements,” he adds.

Cree says that the non-exclusive license agreement with RFHIC underscores each firm’s commitment to developing products that enhance the telecoms infrastructure, while respecting the value and importance of intellectual property.

Tags: Cree RFHIC Doherty amplifier

Visit: www.rfhic.com

Visit: www.cree.com/licensing/programs.asp

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