A Dual-Notch +27dBm Tx-Power Electrical-Balance Duplexer

Abstract

An electrical-balance duplexer uses series connected step-down transformers to enhance linearity and power handling capability by reducing the voltage swing across nonlinear components. Wideband, dual-notch Tx-to Rx isolation is demonstrated experimentally with a planar inverted-F antenna. The O.181lm CMOS prototype achieves >50dB isolation for 220MHz aggregated bandwidth or >40dB dual-notch isolation for 160MHz bandwidth, +49dBmTx-path IIP3 and -48dBc ACLR, for +27dBm at the antenna.

Tunable Frequency-Division Duplex RF Front End Using Electrical Balance and Active Cancellation

“…This isolation bandwidth is feasible for an EBD without high RF complexity in the balancing network (e.g. [20]), and providing sufficient isolation in both bands using the EBD would obviate the requirement for AC. For example, in configuration 5 with the AC disabled, no desensitisation was observed, achieving a noise figure of 6.1 dB and almost 40 dB of Tx band isolation from the EBD alone.…”

“…This work also implements a +27 dBm transmitter chain, and characterises the desensitisation in the presence of a full-power LTE uplink Tx blocker. This goes beyond previous works, which either did not characterise desensitisation noise [16]- [18], [20], [22], or did not achieve +27 dBm Tx power [11]- [13]. The architecture was previously presented in [7]; this paper extends [7], providing further qualitative and quantitative system level analysis of the architecture, presenting additional measurement results at different operating frequencies, duplex separations, bandwidths, and power levels, and analyzing desensitization noise coupling mechanisms in the system.…”

“…Active SIC [7]- [15], in which an additional transmitter is used to actively generate an RF cancellation signal, and passive SIC [16]- [26], wherein the cancellation signal generation is performed through analog signal processing of the RF Tx signal, have both been studied. Electrical balance duplexers (EBDs) [5], [14]- [22], which implement a form of passive SIC, can be implemented on-chip, are tunable over wide frequency ranges, and have demonstrated the power handling, linearity, and low insertion losses required for cellular handset applications [16], [17], [20], [21]. Likewise, tunable integrated active cancellers have also been demonstrated [11]- [13].…”

“…Passive feedforward cancellation requires adaptive multi-tap analog filters [24], [25]. Similarly, in EBDs, the isolation bandwidth is limited by frequency domain variation in the antenna and balancing reflection coefficients, and therefore providing isolation in both bands entails increased RF complexity in the balancing network [18], [20], [27], [28]. Higher order RF processing not only increases the size and cost of the RF front-end, but also requires higher order multidimensional optimisation to tune the circuit parameters [29]- [31].…”

Electrical Balance Duplexer Field Trials in High-Speed Rail Scenarios

“…However, this analysis can be performed by reducing the bandwidth of interest, which will provide higher average isolation across the band. This therefore allows the effect of the environment on EBDs with higher isolation to be observed, and the conclusions which can be drawn from this are also relevant to EBDs which achieve similar levels of isolation over wider bandwidths by employing a more complicated balancing network design with a larger number of tunable elements [9], [13].…”