Fabless semiconductor firm Nujira Ltd of Cambridge, UK has released details of test results that demonstrate how its envelope tracking (ET) technology can unlocks the potential of RF CMOS power amplifiers (PAs) for high-end 3G and 4G smartphone applications, it is reckoned. The details of the results are available to download in a white paper on Nujira’s web-site.
Traditional silicon CMOS PAs suffer from low inherent linearity, limiting their application to low-cost 2G and 3G devices, says the firm. ET removes this limitation and boosts the linearity, efficiency and output power for CMOS PAs beyond the performance of existing gallium arsenide (GaAs) PAs, even for high-linearity LTE signals, it claims.
Extensive lab testing by Nujira has shown that the combination of its ET power modulators and a prototype CMOS PA device achieves the performance required for 4G, it is reckoned. The key metrics achieved were 57% efficiency, 28dBm average output power, and -38dB adjacent-channel leakage ratio (ACLR), with a high peak-to-average power ratio LTE signal.
Nujira says that the high-end performance results have been made possible by its patented ISOGAIN linearization. ISOGAIN removes the need for digital pre-distortion in CMOS PAs and linearizes the PA at no extra cost, power or complexity, while keeping the device in a highly efficient compressed state across a wide power control range, it is claimed.
The firm says that demonstrating the potential for high-end applications of CMOS PAs opens the door for what is set to be a “hugely disruptive technology shift in the RF market”.
“The exploding complexity of the RF front-end in today’s smartphones is driving unprecedented rates of change in the component industry,” says CEO Tim Haynes. “Our test results are a significant breakthrough, demonstrating that CMOS PAs can also be used in high-end 3G/4G smartphone applications,” he reckons. “The combination of CMOS PAs with Nujira’s patented ET architectures could ultimately signal the death of the GaAs industry for handset applications. In the longer term, these results open the door for further CMOS integration, enabling a highly integrated RF front-end architecture for complex multi-mode, multi-band handsets.”
