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RF Electronics ♦ news digest


silicon LDMOS or GaAs transistors are used. This improved performance can help 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 HEMTs and the latest generation digital pre-distortion systems, the resulting efficiency improvements can be up to a staggering 15 percentage points greater than that achieved by a conventional Doherty amplifier implemented with silicon LDMOS.


The Doherty amplifier is a fundamental RF amplifier architecture invented by William Doherty in 1936 using vacuum tubes. Modern implementations of the Doherty amplifier 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 percent improvement in efficiency over traditional non- Doherty Class A/B approaches. 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. Cree’s advancements on the fundamental two-transistor, parallel Doherty architecture can yield significant efficiency improvements,” Milligan added.


The nonexclusive license agreement between


RFHIC, headquartered in Suwon, South Korea, and Cree underscores each company’s commitment to developing products that enhance the telecommunications infrastructure, while respecting the value and importance of intellectual property.


Skyworks showcases new design centre in Korea


The site will support integrated circuit and multi-chip-module designs and layouts, RF- laboratory work, and customer support through early manufacturing.


The new design centre in Korea will support the Company’s increasing demand for 3G and 4G front-end solutions.


In fiscal 2011, Skyworks grew its 3G front-end module shipments by more than 150 percent year-over-year.


“Skyworks is delighted to be placing more of our highly-skilled engineering teams closer to our customers,” said Gregory L. Waters, executive vice president and general manager, front-end solutions at Skyworks. “We realise that our customers’ success depends upon the performance and reliability of our products, and the strength of our service. We are committed to meeting the market’s need for the smallest and highest performance device architectures, as well as strengthening our local support for leading smart phone providers and handset manufacturers.”


Global adoption of 3G and 4G devices, including smart phones, tablets and a seemingly unending array of new applications, continues to be robust. The proliferation of embedded wireless functionality is driving a tremendous increase in RF content and the number of connected devices. In fact, the GSMA recently released research which suggests that the number of mobile connected


January / February 2012 www.compoundsemiconductor.net 133


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