FETs Optimized to Enhance Performance in GSM Base Station Transceivers
By Barry Manz, Contributing Editor

While the media devotes its attention to next-generation (4G) wireless services such as the Long Term Evolution (LTE) to the UMTS standard, the fact remains that equipment designed to be employed in GSM/EDGE systems remains far and away the greatest consumer of RF power transistors. To increase average revenue per subscriber by improving the efficiency of base station transceivers and reduce costs as much as possible, OEMs are turning to their suppliers to make it easier and more cost-effective to employ their devices. To serve this need, Freescale introduced three LDMOS FETs at IMS 2009 that incorporate enhancements to make them easy to integrate into amplifiers while delivering exceptional levels of performance.

The MRFE6S9046N (Figure 3) is designed to operate in the 920 to 960 MHz GSM band, and produces, under GSM EDGE test conditions, 17.8 W of average RF output power with 19 dB of gain, up to 42.5% drain efficiency, and EVM under 2.1% RMS. The FET is housed in Freescale’s cost-effective over-molded packaging that is surface-mountable, which makes it compatible with automated pick-and-place manufacturing. Enhanced internal impedance matching also allows manufacturers to more easily accommodate printed circuit board variations, and internal output matching provides a “design-friendly” terminal impedance. Second and third harmonic terminations ensure high efficiency when employed in Class F amplifiers.

The MRF8S9100H/HS, designed for 920 to 960 MHz operation and the MRF8S18120H/HS for 1805 to 1880 MHz operation are 28-VDC devices designed for Class AB and Class C operation. In GSM EDGE service, the MRF8S9100H/HS delivers 45 W average power, gain of 19.1 dB, efficiency of 44% at 940 MHz, and EVM of 2% RMS. In GSM EDGE service, the MRF8S18120H/HS delivers 46 W average power gain of 18.2 dB, efficiency of 42% at 1840 MHz and EVM of 1.7 percent RMS. Both devices are housed in rugged air-cavity ceramic packages.
The MRF8S9100H/HS can also be operated in the 800 MHz GSM band, and the MRF8S18120H/HS supports operation in the 1900-MHz GSM band. Like the MRFE6S9046N, the devices are internally-matched to simplify circuit design, are RoHS compliant, and contain internal ESD protection circuitry. The MRFE6S9046N is in full production and samples are available. The MRF8S9100H/HS and the MRF8S18120H/HS are in full production. Reference test fixtures and large-signal models are also available. For additional details, visit our website.

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