A Frequency-Agile RF Frontend Architecture for Multi-Band TDD Applications

Emerging wireless standards specify dozens of bands spanning several octaves, which need to be supported in form-factor and energy constrained mobile devices targeting ubiquitous connectivity. However, in current multi-band radio implementations, significant redundancy is still the norm in the RF frontend. This work introduces an improved architecture for multi-band, time-division duplexed (TDD) radios, which replaces multiple narrowband frontend components with a frequency-agile solution, tunable over a wide frequency range. A highly digital architecture is adopted, leading to a fully integrated solution wherein both efficiency and achievable frequency range benefit from CMOS scaling. A prototype is integrated in 45 nm SOI CMOS. Peak PA output power is 27.7 ±0.5 dBm from 1.3 to 3.3 GHz, with up to 30% total efficiency at 2 V. For TDD LTE applications, better than -30 dBc ACLR and -30 dB EVM is measured with 64 QAM, 20 MHz signals from 1.44 to 3.41 GHz, with up to 17.2% average efficiency and 23.4 dBm average power. The LNA achieves AV ≥ 14 dB, NF = 4.4 ±1.6 dB and IIP 3 ≥ -7 dBm from 1.3 to 3.3 GHz while drawing just 6 mA from 1 V. The demonstrated frequency range covers a total of 11 TDD bands .