13.3 A SAW-less reconfigurable multimode transmitter with a voltage-mode harmonic-reject mixer in 14nm FinFET CMOS

Abstract

Multimode cellular RFICs need high dynamic range in order to simultaneously satisfy the high linearity requirements of LTE and the low-noise performance of 2G. Traditionally, SAW filters are employed to relax the noise-linearity trade-off at the cost of higher BOM. In a highly competitive market, mobile devices need to support >35 LTE bands, a number which is expected to rise further in the future, providing a strong motivation for SAW-less transmitter (TX) design. An LTE TX operating in the single resource-block (RB) mode is susceptible to spurious out-of-band (OOB) emission due to the high power spectral density concentrated in narrow bandwidths at frequency offsets as large as 4.5 MHz (LTE10) or 9 MHz (LTE20) from the carrier. The most challenging condition is for B13 where the 3 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rd</sup> -order counter intermodulation (CIM3) product falls in an adjacent public-safety band. With 23dBm at the antenna, a B13-TX must ensure OOB emission less than -57dBm/6.25kHz in the public safety band.