The pressure is on for smartphone manufacturers to add 5G New Radio (NR) support to handset designs even while 5G standards are still being developed. Initial mobile deployments will utilize the non-standalone (NSA) 5G NR specification, which creates additional RF challenges due to the need to simultaneously enable 4G LTE and 5G connectivity. These topics and more are discussed in Qorvo’s white paper “Is Your Handset RF Ready for 5G?,” which delves into what the advent of 5G means to smartphone manufacturers.
The white paper explains that uncertainties still exist regarding key details of fundamental RF specifications for 5G. Specific points mentioned include power back-off levels, regional band combinations, uplink multiple-input, multiple-output (MIMO), and supplemental uplink (SUL). Furthermore, inclusion of 5G content in time for planned network deployments places pressure on smartphone manufacturers to develop the implementation strategies needed to meet tough 5G RF requirements.
Various challenges are associated with adding 5G support to handsets that are already densely packed with 4G LTE functionality. Enabling the dual 4G LTE/5G connectivity required for the 5G NSA specification results in significantly greater levels of RF complexity. In many cases, operators are expected to combine 4G FDD-LTE bands with a 5G band. The NSA specification allows the handset to transmit on one or more of these LTE bands while also receiving on a 5G band. However, this scenario means that harmonics of the transmit frequencies can potentially de-sense the receiver.
Dual connectivity is associated with other challenges, such as accommodating two primary cellular antennas in a handset. Power management is another concern, due to the need for an additional dc converter. 4-×-4 MIMO represents a challenge, too, as does the unprecedented bandwidth and new waveforms utilized for 5G communications.
The white paper notes that many existing 3G/4G spectrum allocations will be refarmed for 5G NR bands, resulting in additional complications. The document concludes by noting that RF suppliers must raise the bar in areas like power-amplifier (PA) design, RF front-end (RFFE) module integration, antenna tuning, and antenna-plexers.
Qorvo Inc., 7628 Thorndike Rd., Greensboro, NC 27409; (336) 664-1233.