Envelope-tracking 4G PA achieves record 40-MHz bandwidth with carrier aggregation

August 27, 2013 // By Paul Buckley
Nujira says it can now support 40 MHz channel bandwidths for 4G LTE-Advanced signals, using the company's NCT-L1300 ET modulator IC and a commercially available handset RF Power Amplifier.

Enabled by Nujira’s ET technology, the company claims it is the first time that an ET system has delivered 40 MHz bandwidth, while meeting stringent regulatory compliance standards.
The results used the Carrier Aggregation feature of the LTE-Advanced specification to transmit a 200 Resource Block LTE waveform – the highest bandwidth currently specified (CA Class C), corresponding to an instantaneous data rate of approximately 150 Mbps.
Performance was measured at 27 dBm at the PA output, corresponding to 23 dBm at the antenna, the maximum power permitted for LTE terminals.  Error Vector Magnitude (EVM) of 3% and Adjacent Channel Leakage Ratio of -35 dBc were achieved using Nujira’s ISOGAIN ET Linearisation technique, giving an adequate margin over regulatory requirements without relying on Digital PreDistortion or other modem assistance techniques.
Achieving the full bandwidth, Nujira notes, is important, as it is always preferable for the handset to transmit data at the highest data rate for as short a time as possible, to maximise network capacity and to save energy. Transmitting the same amount of data over a 20 MHz channel, rather than 40 MHz, would take twice as long and use almost twice as much power.  Field trial data from LTE networks has shown that high bandwidth transmissions from the handset can represent more than 50% of the energy consumed by the RF front end.
Tim Haynes, CEO of Nujira said: “Nujira’s High Accuracy Tracking architecture for ET has consistently delivered the highest bandwidths in the industry.  Our Coolteq-L chips were the first to deliver the 20 MHz bandwidths needed for today’s LTE smartphones, and this result shows that we can support the 40 MHz LTE-A Carrier Aggregation requirements of leading operators such as China Mobile, Softbank and Clearwire.”
“Competing ET solutions are either limited to a few MHz of signal bandwidth in ET mode, or deliver no useful efficiency advantage at higher bandwidths.  By supporting the highest possible channel bandwidths