RF CMOS Ready for Prime Time
Three major players have now released RF CMOS Handset PA Modules
As Mobile World Congress starts this week, one of the biggest trends taking place on the mobile handset side is the release of 4G CMOS PAs that integrate other functions such as envelope tracking and antenna tuning. While CMOS PAs have been around for a while, most have struggled to meet 4G performance requirements but these new products promise to reduce the costs, reduce RF footprint and improve efficiency even in the highest end phones. First out of the gate a year ago was the Qualcomm RF360 includes an envelope power tracker for 3G/4G LTE mobile devices, a dynamic antenna matching tuner, an integrated power amplifier-antenna switch, and an innovative 3D-RF packaging solution incorporating key front end components. The Qualcomm RF360 solution is designed to reduce power consumption and improve radio performance while reducing the RF front end footprint inside of a smartphone by up to 50 percent compared to the current generation of devices. The solution can reduce design complexity and development costs by combining the new RF front end chipsets with Qualcomm Snapdragon all-in-one mobile processors and Gobi™ LTE modems for a complete solution. Interesting that Qualcomm chose to enter the RF market but makes sense that they can supply the whole radio system. The 3D design is unique in that the envelope tracking module can be supplied separately and has already been designed into other phones.
A few weeks ago Peregrine announced their Global 1 SOI CMOS single chip solution for handsets. It includes a multimode, multiband power amplifier PA, post-PA switch, antenna switch, and antenna tuner. It supports over 40 frequency bands and supports envelope tracking and has a common RFFE MIPI interface. As they stated in their release, a standard industry benchmark for PA performance is PAE using a WCDMA (voice) waveform at an ACLR of -38 dBc. Under these conditions, the performance of the Global 1 PA approaches 50% PAE. This is on par with the leading GaAs PAs and exceeds the performance of other CMOS PAs by 10 percentage points. The Global 1 PA maintains GaAs-equivalent PAE for LTE waveforms with varying resource-block allocations. With an envelope tracker, the system efficiency of Global 1 typically increases 10 percentage points, depending on band.
And at Mobile World Congress, we get word that RFaxis is introducing the RFX9160, a multi-mode, multi-band envelope tracking PA that comes fully integrated with the RFaxis envelope tracker designed for the latest 4G LTE cellular radio standards. Its supports 3G WCDMA/HSPA+ and 4G FDD/TDD LTE QPSK and 16QAM modulation. The RFX9160 consists of single-die multi-band CMOS ET PA and meets UMTS (Rel 99) linearity requirements up to +28.5dBm output power and LTE (MPR=0dB) to +27.5dBm. Control is managed over the integrated MIPI™ digital RFEE and eTrak interfaces. This device also has input and output impedance matching, a harmonic filter, and ESD protection. It is compatible with the latest class of LTE transceivers and a broad range of power management ICs (PMICs) with ET algorithm support. It is packaged in the ultra-small 3.0x3.0 mm QFN which is a very small footprint. It achieves about 41% PAE in high power WCDMA mode.
Where does this leave the GaAs manufacturers? These products are still new so it will be a while before these can be widely adopted into handsets and while CMOS-based products promise cost advantages, this is probably only realized in high volume handsets. GaAs based products may also be able to offer greatly flexibility since not everything is integrated onto a single chip or module as leverage the best technology for each function. Several GaAs companies have recently purchased CMOS PA companies to reduce their risk such as RFMD acquiring Amalfi and Avago acquiring Javelin. But I think the writing is on the wall that CMOS will be displacing a significant percentage of GaAs in the handset market. This is probably evidenced by the merger of RFMD and TriQuint announced today.