HAT™ Technology Overview
Evolving standards - including WCDMA, WiMAX and DVB use complex modulation schemes that require the use of linear RF power amplifiers (PAs) which are only efficient when operating at peak power, a condition that rarely occurs because the signal amplitude varies with the data being transmitted.
In a traditional (Class AB) amplifier the main output amplifier stage is operated at a constant supply (drain) voltage. When amplifying real-life WCDMA signals such amplifiers have an efficiency of around 15%, i.e. 85% of the power provided to the PA is dissipated as heat.
Using an advanced envelope tracking technique, Nujira’s technology overcomes this problem by modulating the voltage supplied to the PA in line with the modulation envelope, to ensure that the output device remains in its most efficient operating region, via a high-efficiency High Accuracy Tracking (HAT™) power modulator. Using this technique, the amplifier always operates in compression, even at reduced output power, and this dramatically improves the PA efficiency - providing PA efficiencies of 45% and more.
The Nujira HAT technology is fully compatible with digital pre-distortion techniques, and does not degrade system linearity. PAs designed with HAT technology are inherently broadband, and do not need to be optimised for specific modulation types. The technique is equally applicable to LDMOS, GaAs or GaN based PAs.
