RF power amplifiers target industrial radios

20th July 2015

Siobhan O'Gorman

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Two RF power amplifiers that can be operated at 3.6 or 7.5V and are targeted for applications where power for radio range and efficiency for battery life are key design requirements have been introduced by Freescale Semiconductor.

Mobile radio systems, for instance, are transitioning from analogue to digital modulation schemes, which usually require a radio redesign. The outstanding efficiency of Freescale’s Airfast AFIC901N and AFT05MS003N allows land mobile radio OEMs to enhance battery life. In addition, the devices’ high gain provides an opportunity to reduce the number of transistors used, thus minimising system cost. Radio designers can also leverage available reference circuits to minimise time to market for their own products.

Freescale’s Airfast AFIC901N LDMOS RF integrated device and AFT05MS003N LDMOS transistor are designed to meet these challenges, with broad bandwidths that cover frequency bands between 136 and 941MHz. They also offer high efficiency and gain, and are housed in compact and lightweight over-molded plastic packages. Their extreme ruggedness, which is greater than 65:1 VSWR, enables highly robust handheld radios.

The transistors are well-suited for use in combination with Freescale MCUs for applications such as automatic meter readers that operate at 169, 434 or 868MHz, where they can cost-effectively increase the application’s communication range. They are also suitable for other M2M applications and SCADA systems.

The AFIC901N two-stage LDMOS device delivers 1W CW of RF output power with 63% efficiency and 30dB gain at VHF frequencies between 136 and 174MHz. The device is housed in a QFN 4×4 package. As it delivers its full 30dBm rated power with an input power of only 0dBm, it eliminates the need for pre-amplification. The AFIC901N offers RF matching flexibility externally to the device at the input and output, as well as at the interstage level. This lets designers optimise the device for their particular system requirements, including multiple radio bands, by changing only a few discrete components on the circuit board.

The single-stage AFT05MS003N provides 3W of CW power. It covers 136 to 941MHz with 17dB gain and 67% efficiency in the VHF band, and has exceptional input and output. The AFT05MS003N is housed in a SOT-89 over-molded plastic package. The new transistors join Freescale’s Airfast portfolio of 7.5 to 12.5VDC transistors for mobile and M2M radio applications ranging from 1 to 75W.