Maxim Integrated’s SC2200 RF power amp linearizer promises greener cellular networks

Introduced at IMS2016, the dual-path SC2200 RF power amplifier linearizer (RFPAL) from Maxim Integrated aims to let designers of RF front­ends achieve high linearity at lower power, cost, and size in small-cell MIMO base stations, active antennas systems (AAS), distributed antennas systems (DAS), or in systems requiring two different simplex bands. Wideband signals in today’s telecommunications systems have high peak-to-average ratios and stringent spectral regrowth specifications that place high linearity demands on power amplifiers.

Linearity can be achieved by backing off output power at the price of reducing efficiency. However, this increases the component and operating costs of the power amplifier. Better linearity can be achieved through the use of digital predistortion (DPD) and other linearization techniques, but many of these methods are time consuming and costly to implement. The SC2200 is a true RFIN/RFOUT solution where the complex signal processing is done in the RF domain, supporting modular power amplifier designs that are independent of the baseband and transceiver subsystems. The device uses the PA output and input signals to adaptively generate an optimized correction function to minimize the PA’s distortion.

Power savings result because the dual-­channel linearizer enables Class A/AB and Doherty power amplifiers to consume up to 70% less power compared to a 37-dBm power amplifier operated in back-off mode; the RFPAL uses less than 1.5 W when both paths are fully operational. The device saves money by cutting bill-of-materials (BOM) costs up to 50%, through use of smaller power supplies, heat sinks, and enclosures, and reducing transistor cost due to back-off. Finally, the SC2200 is up to eight times smaller than other DPD solutions, and occupies less than 1 in.² of board space. The SC2200 supports 2G to 4G standards (FDD and TDD) from 698 MHz to 2700 MHz as well as an expanded range of signal bandwidths from 60 MHz down to 1.2 MHz. It accepts single-ended RF signals to eliminate baluns and features a mirrored pinout facilitating design of both paths. The part is available now, as are three evaluation kits: SC2200­EVK900 (698 to 960 MHz), SC2200­EVK1900 (1,800 to 2,200 MHz), and SC2200­EVK2400 (2,300 to 2,700 MHz).