Novel front-end rejects RF self-interference for LTE

With the proof-of-concept demonstrator, an electrical-balance duplexer is used to passively cancel transmitter noise in the receive band, and an active canceller is employed to suppress self-interference in the transmit band.

It has been characterised in duplex configurations working between 700MHz and 950MHz, as well as LTE bands 3 (1.9GHz) and 7 (2.6GHz).

Noise figure is 6.0–7.4dB in the presence of a +27dBm LTE uplink Tx blocker for duplex separations of 47.5MHz and above.

According to the team, it is compliant with the reference sensitivity test cases in the 3GPP LTE specification in LTE bands 3 and 7, as well as 28 (700MHz).

Although U-blox is Swiss, it was the firm’s Cork design centre that was involved in the collaboration – with Bristol’s Communication Systems & Networks (CSN) Group – and it involved postgraduate students from the University funded by and trained through the EPSRC Centre for Doctoral Training in Communications.

“Much has been achieved through our research collaboration with ublox,” said Professor Mark Beach of Bristol. “This dates back to 2012 with the sponsorship and mentoring of Leo Laughlin’s PhD, followed by collaborative R&D through EPSRC Impact Acceleration funding, building-on the innovation from Leo’s and Chunqing Zhang’s PhDs.”

The work had been published in the IEEE Transactions on Microwave Theory and Techniques journal as ‘Tunable frequency-division duplex RF front end using electrical balance and active cancellation‘.