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Power Amplifiers: Nujira CMOS could spell the end for GaAs


UK BASED FIRM Nujira has released the details of significant test results that demonstrate how ET technology unlocks the potential of RF CMOS PAs for high end 3G and 4G smartphone applications.


The firm is a specialist in Envelope Tracking (ET) technology. Envelope tracking is an approach to RF amplifier design in which the power supply voltage applied to the power amplifier is constantly adjusted to ensure that the amplifier is operating at peak efficiency for the given instantaneous output power requirements. Traditional CMOS PAs suffer from low inherent linearity, limiting their application to low cost 2G and 3G devices. ET removes this limitation and boosts the linearity, efficiency and output power for CMOS PAs beyond the performance of today’s GaAs PAs, even for high linearity LTE signals.


Extensive lab testing by Nujira has shown that the combination of the firm’s ET power modulators and a prototype CMOS PA device achieves the performance required for 4G. The key metrics achieved were 57 percent efficiency, 28dBm average output power, and -38dB ACLR, with a high peak-to-average power ratio LTE signal.


These high end performance results have been made possible by Nujira’s patented ISOGAIN Linearisation. ISOGAIN removes the need for Digital Pre Distortion in CMOS PAs and linearises 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. By demonstrating the potential for high end applications of CMOS PAs, Nujira has opened the door for what is set to be a hugely disruptive technology shift in the RF market.


Tim Haynes, CEO of Nujira comments, “The exploding complexity of the RF front- end in today’s smartphones is driving unprecedented rates of change in the component industry. Our test results are a significant breakthrough, demonstrating that CMOS PAs can also be used in high- end 3G/4G smartphone applications. The combination of CMOS PAs with Nujira’s patented ET architectures could ultimately


RFMD welcomes envelope tracking


RF MICRO DEVICE’S ET-based solutions leverage the company’s leadership in RF power management and cellular power amplifiers (PAs) to improve system-level efficiency in high-data rate applications.


The new RF solutions - the RF7389, RF7390, RF7459, RF8081, and RF8085 - comprise ET PMICs, ET multimode multi- band (MMMB) PAs, and ET ultra-high efficiency PAs.


According to RFMD, the PA products are predominantly gallium arsenide (GaAs based), while the PMIC products are based on silicon.


RFMD’s expanding ET product portfolio is compatible with the leading LTE chipsets and provides full ET compatible coverage of all FD-LTE and TD-LTE bands (1-14, 17-21, 25-28, 38, 40, 41, and 44). RFMD anticipates the combination of ET technology and RFMD’s advancements in RF power management will be a disruptive combination that raises the bar significantly in RF performance.


In February, Nujira and Qualcomm announced that they were players in the envelope tracking market using silicon CMOS solutions which could displace GaAs based solutions. Eric Creviston,


10 www.compoundsemiconductor.net March 2013


president of RFMD’s Cellular Products Group, says, “RFMD is at the forefront of technology development in RF power management, and we are enthusiastic about the deployment of ET-based solutions.


We believe the importance of power management technologies such as average power tracking (APT) and envelope tracking will continue to expand in smartphones, enabling RFMD to leverage our combined leadership in power amplifiers and RF power management and increase our RF content opportunity.”


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.”


Nujira’s mission is to dramatically improve the energy efficiency of transmitters for 3G and 4G handsets, base stations and TV broadcast applications by reducing the amount of waste energy dissipated as heat in the RF Power Amplifier circuit. Nujira’s patented Coolteq Modulator technology dynamically controls the power supply to the circuit in line with the amplitude of the signal, enabling the creation of highly efficient RF Power Amplifiers.


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