As wireless carriers are constantly seeking ways to increase the performance, capacity, and efficiency of their networks while also extending their operating frequencies, RF power devices are always in the spotlight. This is true not just for macro cells but increasingly for small cells to ensure high quality of service at cell edges and other areas where optimum coverage is difficult to provide. With these challenges in mind, NXP has extended its portfolio of 48-VDC GaN RF power transistors to cover frequencies up to 3600 MHz, and its 28-VDC LDMOS RFICs for outdoor small cells to 3800 MHz. All of the devices are designed for use in Doherty-type amplifiers and are optimized for seamless integration with digital predistortion linearization circuits.
The GaN transistors collectively cover 1805 to 3600 MHz and combine efficiency up to 57% and gain up to 17.7 dB with the ability to deliver their rated performance without failure when exposed to an impedance mismatch VSWR greater than 10:1 with 3 dB overdrive. They include the AG22S251-01S symmetrical Doherty amplifier that covers 1805 to 2200 MHz with average RF output power of 71 W, gain of 17.7 dB, and drain efficiency of 37.5%.
The A2G26H281-04S represents NXP’s first dual-path Doherty transistor that covers 2496 to 2690 MHz and delivers power of 50 W, gain of 15.3 dB, and 57% drain efficiency. Finally, A2G35S160-01S and A2G35S200-01S are a two-device Doherty solution that covers 3400 to 3600 MHz. The A2G35S160-01S delivers 32 W average RF output power, gain of 15.9 dB, and drain efficiency of 38.9%. The A2G35S300-01S delivers 40 W average output power with gain of 16.1 dB and efficiency of 36.7%. Detailed specifications for the new devices are shown in Table 1.
LDMOS ICs for Small Cells
With the introduction of eight new devices, NXP’s expanded LDMOS IC portfolio is the industry’s largest, and features two-stage, dual-path Doherty-optimized design for use in small cell base stations. The new LDMOS ICs cover all current and proposed frequency bands from 728 to 3800 MHz, with RF output power of 2.5 to 12 W. They combine two stages of gain to supply both the carrier and peaking stages required by Doherty power amplifiers in a single device. The four symmetric devices cover wide frequency ranges—up to 900 MHz of RF bandwidth and 365 MHz of instantaneous bandwidth. All are easy to linearize with analog and digital predistortion solutions. Detailed specifications are shown in Table 2.
The LDMOS ICs are extremely rugged and can operate into an impedance mismatch (VSWR) of 10:1 when driven by twice their rated RF input power without performance degradation or failure. They also incorporate features at the die and package levels that make them extremely small, which is of considerable importance in outdoor small cells that are designed to blend unobtrusively into their environments. All have RF-decoupled drain pins to reduce required board space, on-chip input and output matching to 50 ohms, and incorporate quiescent current temperature compensation that can be disabled if required. More information about the GaN and LDMOS devices is available at www.nxp.com/RF.