Issue link: https://resources.mouser.com/i/1520712
33 Qorvo 2024 Accompanying these trends is the proliferation of small Internet of Things (IoT) devices with cellular and/or non- cellular connectivity, including watches, other wearables, and small tracking devices. Space is at a premium in these devices, and the ability to squeeze RF content into a tiny amount of space is essential. Antenna Challenges These innovations in connectivity and industrial design create a broad variety of interrelated antenna challenges for engineers working on next-generation smartphones and other mobile devices. RF Paths More Than Double The addition of new cellular and non-cellular bands is massively increasing the total number of RF paths in mobile devices (Figure 2). A typical 5G phone with support for mmW bands and UWB has more than twice as many RF paths as a typical 4G phone. Each RF path needs to connect to an antenna, but it's simply impossible to double the number of antennas due to the limited space available in handsets: Increasing the number of antennas means they must be closer to each other, which reduces the isolation between them. This causes coupling-related issues, increasing the potential for non-linear elements in the RFFE, which desensitizes (i.e., desenses) the receiver. Given the limitation on the total number of antennas that may be implemented in a fixed form factor, the logical approach to handling the growing number of RF paths is to increase each antenna's bandwidth to support a larger number of bands. However, this approach brings its own challenges: Wider-bandwidth antennas tend to be more lossy, and they may require more space because the size of an antenna is determined by the lowest frequency it supports. Furthermore, using a single antenna to simultaneously transmit and receive multiple bands increases the risk of non- linear spurious emissions generated by mixing signals. Solving these problems is not easy—it requires careful analysis and specialized antenna design techniques combined with appropriate filtering and routing within the RFFE. UWB Supporting UWB requires three or four relatively large patch antennas, which consume a considerable amount of the already crowded space within handsets. Accordingly, manufacturers are looking for ways to combine some of these antennas to reduce the overall area required. A further consideration is whether to position one antenna on the edge of the phone for optimal omnidirectional ranging. Carrier Aggregation and EN-DC The rapid increase in band combinations for CA and EN-DC exacerbates the antenna challenges. Potential aggregations now include hundreds of different permutations of high-, mid-, and low-frequency bands. They include combinations of multiple bands within each frequency range (such as low- low or mid-mid aggregations) as well as combinations of bands in different regions of the spectrum (such as low-mid and low-mid-high). Furthermore, the maximum bandwidth of each CC has also increased. While 4G limited carrier bandwidth to 20MHz, 5G increases the maximum contiguous bandwidth to 45MHz for bands below 2300MHz and up to 100MHz for bands above 2300MHz. Because the total number of antennas is limited, each antenna may need to provide high performance for wideband transmit and receive signals over a very wide frequency range, from 600MHz to 5000MHz. Figure 2: 4G to 5G transition increases constraints on the RF. (Source: Qorvo)