LDMOS devices to boost basestation efficiency

A breakthrough in LDMOS technology offers opportunities to reduce the complexity and operating costs of 3G cellular basestations while enhancing their performance and reliability.

A breakthrough in LDMOS (laterally diffused metal oxide semiconductor) technology offers opportunities to reduce the complexity and operating costs of 3G cellular basestations while enhancing their performance and reliability.

RF power transistors fabricated using Philips' new 4th generation LDMOS technology operate with higher gain and higher operating efficiencies than existing LDMOS devices.

As a result, fewer gain stages are needed in RF power amplifiers and less operating energy is wasted.

The exceptional linearity of these new transistors, even at high power levels, means they meet the ultra-low distortion requirements of multicarrier W-CDMA and GSM Edge basestation amplifiers.

The rollout of long awaited 3G cellular infrastructures is seen as the next big step in delivering a richer multimedia experience and more advanced data services to mobile users.

The same characteristics that make Philips' LDMOS technology ideal for use in new 3G infrastructures also allows it to be used in transmitters for the many digital terrestrial TV systems that are currently being rolled out across the world.

"With our 4th generation LDMOS technology we have given RF power amplifier designers the extra design space they need to overcome difficult efficiency versus linearity tradeoffs", said Rick Dumont, Marketing Manager for LDMOS RF Power Devices at Philips Semiconductors.

"These new devices will make it significantly easier to meet the performance requirements of systems such as W-CDMA at the price points demanded by the telecommunications industry and will further strengthen our position as a leading supplier of LDMOS RF power devices to key cellular infrastructure manufacturers".

Philips' new 0.6um LDMOS technology takes RF power transistor performance to a whole new level, achieving a 50% higher power density, a 6-8% higher W-CDMA efficiency, and a 2dB higher power gain than previous 0.8um technologies.

In addition, the patented double gold metallisation and gold-gold wirebonding used in these transistors extends their MTTF by 8 to 10 times that of conventional LDMOS devices, or alternatively allows designers to operate them at junction temperatures up to 20C higher.

Due to the intrinsically low system efficiency of W-CDMA power amplifiers, all these features significantly reduce power consumption and thermal issues in state-of-the-art 3G basestations and facilitate the trend towards mast-mounted rather than ground-based amplifiers.

The exceptional backoff linearity of Philips' 4th generation LDMOS transistors particularly suits them for MCPA (multicarrier power amplifier) and future DPD (digital predistortion) applications.

The first power transistors to use this breakthrough LDMOS technology will be sampled in Q4 2003 and will be ready for volume production in the Q1 2004.

The first device to be introduced will be the BLF4G22-100, a WCDMA transistor with 13.5dB gain, a gain flatness of 0.1dB (2110 to 2170MHz), and two-carrier WCDMA operating efficiency of 26% at a power output of 24W, an ACPR of -40dBc and IMD of -36dBc.

Peak output power for this transistor under the above operating conditions with an IS95 signal and 3dB compression of the CCDF is over 150W.

Philips' 4th generation LDMOS technology will ultimately be applicable across all cellular frequency bands from 800MHz to 2.2GHz.

Philips' LDMOS roadmap shows that in future developments, the advanced fabrication capabilities of the company's 0.18um mainstream CMOS manufacturing process will be leveraged.

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