Issue link: https://resources.mouser.com/i/1313800
Meeting Sub-6GHz RFFE Design Goals Building the RF front end (RFFE) to support these new sub-6GHz 5G applications will be a challenge. The RFFE is critical to the system's power output, selectivity, and power consumption. The complexity and higher frequency range are driving the need for RFFE integration, size reductions, lower power consumption, high output power, wider bandwidth, improved linearity, and increased receiver sensitivity. In addition, there are tighter coupling requirements between the transceiver, RFFE, and antenna. Some of the goals of the 5G sub-6GHz RFFE, and how GaN PAs can help achieve them, include: • Higher frequencies and increased bandwidth: 5G uses higher frequencies than 4G and requires much wider component carrier bandwidths (up to 100MHz). GaN-on-silicon-carbide (GaN-on-SiC) Doherty PAs achieve wider bandwidths and higher power-added efficiencies (PAEs) than LDMOS at these frequencies. The higher efficiency, higher output impedance, and lower parasitic capacitance of GaN devices allow for easier wideband matching and scaling to very high output power. • High power efficiency at higher data rates: GaN has soft compression characteristics, making it easier to pre- distort and linearize. Thus, it's easier to use in digital pre-distortion (DPD) high-efficiency applications. GaN is able to operate across multiple cellular bands, helping network operators deploy carrier aggregation to increase spectrum and create larger data pipes for increasing network capacity. • Minimizing system power consumption: How do we meet the high data requirements of 5G? We will need more infrastructure, such as data centers, servers, and small cells. This means an overall increase in network power consumption, thus driving the need for system efficiency and overall power savings. Ultimately, the carriers demand more for less, which might seem difficult. But again, GaN can help provide the solution by offering high output power coupled with increased efficiency in base stations. Figure 6 shows a high-level block diagram of an example sub-6GHz RFFE, which uses a Qorvo Doherty PA design to attain high efficiency. | 26 | Figure 6: This sub-6GHz massive MIMO RFFE includes a Doherty PA.