ystems will require the PA to operate with APT mode to accommodate the wider bandwidth signals. Therefore, users can expect a 100 MHz channel when the PA is operating under APT conditions. Conversely, conventional ET is challenged to perform in 40-60 MHz bandwidth. In order to extend the ET modulator bandwidth to reach 100 MHz, additional power consumption would be required, in addition to addressing amplitude/phase delay mismatch sensitivity, management of memory effects, limitations in RF_IN (n77) Antenna 1 (n77) Switches multiplexer Antenna 2 (n79) RF_IN (n79) PA + antenna Low-noise switch modules amplifier RFFE 1 (PMIC) RFFE 2 (PMIC) Wideband directional couplers outputs Clocks, control inputs/outputs, etc. PMIC: power management integrated circuit Figure 5.27 Example of sub-6 GHz 5G NR transmit/receive front-end architecture 28]. 732 Chapter 5 capacitive supply loading, OOB [transmitter] emissions, and intermodulation leakage into the LTE anchor band. Although, there are several promising techniques under development to extend ET to wider operating bandwidth, it will take several years before they can be commercialized. Designers are thus left with the challenge of delivering a better performing PA at two to three times the present state-of-the-art instantaneous bandwidth, while operat- ing with a higher peak-to-average power ratio of CP-OFDM and over much larger pass- bands than present filters for LTE sub-3 GHz. Aside from the wider channel bandwidth, operators have shown significant interest in high- power UE capabilities, especially as it pertains to TDD bands in the sub-6 GHz range. At present, there is some uncertainty regarding whether the bands will require 2 X 2 uplink (two transmitters operating at the same time) or a single transmitter would suffice, which means that the PAs will not only need to deliver industry-grade output powers compared to their LTE counterparts, but also they will have to achieve that over a wider bandwidth and at higher frequencies. Meeting higher output power at higher fre