Freescale announces RF power LDMOS transistors that cover full frequency bands for wireless base stations

Freescale Semiconductor has introduced two LDMOS RF power transistors that allow wireless base station amplifiers to cover all channels in an entire allocated frequency band. The high-efficiency transistors help reduce capital and operating expenditures, and their wide instantaneous bandwidth allows operators to increase network flexibility.

Most of today’s amplifier systems operate with instantaneous (video) bandwidth limitations of 20 to 40 MHz and require a separate power amplifier for each channel. However, increasing wireless data traffic is driving a trend to extend amplifier systems to cover entire wireless frequency bands. Freescale’s new RF power LDMOS transistors deliver a compelling combination of high linearity, high efficiency, wide instantaneous bandwidth and high power that extend the instantaneous signal bandwidth to an industry-leading 160 MHz, making them ideal for these next-generation amplifier systems.

Freescale’s MRF8P20165WH/S for the 1930 to 1995 MHz PCS band and the MRF8P20140WH/S for the 1880 to 2025 MHz TD-SCDMA bands F & A, can support the corresponding wireless spectrum with one amplifier. This significantly reduces the number of power amplifiers needed for a multi-band base station and enables network operators to consolidate devices and equipment, resulting in lower operating expenditures.

In addition, the wide instantaneous bandwidth of Freescale’s new LDMOS devices increases network flexibility for network operators by allowing network equipment sharing between operators and by simplifying upgrades. Operators can add/exchange spectrum holdings within a frequency band without upgrading equipment, and because wideband/multi-band PAs are generally agnostic to modulation formats, operators can upgrade to 4G LTE and other wireless standards with a simple software change and no additional hardware. This means network operators save on both capital and operating costs. Operators also can reconfigure channels on the fly and apply channel consolidation to support increased data rates.

“The need for RF power transistors to deliver exceptional linearity and efficiency over a full wireless band is no longer simply desirable; it is essential,” said Ritu Favre, vice president and general manager of Freescale’s RF Division. “The devices we are introducing today are the first in a family of broadband RF power transistors that includes all current and emerging wireless bands. Each device will be designed to combine all of the attributes – high efficiency and linearity and high output power– required to allow carriers to meet the challenges of the future.”

Freescale’s MRF8P20165WH/S and MRF8P20140WH/S meet linearity requirements for PCS and TD-SCDMA standards while delivering efficiency of at least 43.7 percent when amplifying multiple wireless carriers separated by up to 65 MHz (PCS) and 140 MHz (TD-SCDMA). Both devices are dual-path designs, and can implement the final stage of a Doherty amplifier with one path as the main amplifier and the other as the peaking amplifier.

Key specifications of the new RF power LDMOS devices:

MRF8P20165WH/S (1930 to 1995 MHz)

* 37 W average power with input signal peak-to-average ratio (PAR) of 9.9 dB
* 47.7% drain efficiency
* 16.3 dB typical power gain

MRF8P20140WH/S (1880 to 2025 MHz)

* 24 W average power with input signal PAR of 9.9 dB
* 43.7% drain efficiency
* 16 dB typical power gain

Both devices are designed for use in Doherty amplifier configurations and digital pre-distortion. They are extremely rugged and can handle a 10:1 VSWR impedance mismatch when operating at 30V and driven with twice their recommended input power. The transistors are internally matched with low capacitance to simplify circuit design and have integrated electrostatic discharge (ESD) protection that makes them more resistant to stray voltage encountered on assembly lines. In addition, their broad gate-source voltage range of -6 to +10V increases their performance when operated in Class C mode. The transistors are housed in Freescale’s NI-780-4 and NI-780S-4 air cavity packages.