Issue link: https://resources.mouser.com/i/1484091
12 The Future of Automotive How high-selectivity filter solutions tackle co-existence challenges Let's examine some of the ways filter technology solutions help address V2X coexistence with Wi-Fi and cellular spectrum. Here are three of the top challenges: • V2X and 5GHz Wi-Fi • Wi-Fi 2.4GHz and Cellular bands 7, 40, 41 • Electronic Toll Collection (ETC) and V2X V2X Coexistence Challenge with 5GHz Wi-Fi As shown in Figure 2, the Wi-Fi 5GHz Unlicensed National Information Infrastructure 3 (UNII 3) band overlaps with the 5.9GHz V2X band. For these two radios to operate without interference, a filter is required. This filter needs to have very steep attenuated out of band edges near the 5.855GHz area to ensure the V2X and Wi-Fi UNII 3 signals do not cause communication interference. Additionally, the UNII 2C receive band noise can cause receive signal desense. Desense, in this case, is the design challenge of interference among wireless devices with multiple radios operating simultaneously. These signals could interfere and compromise the receiver's sensitivity, making it less able to receive weak signals. For example, if a transmit signal is not properly isolated from the receiver, it could interfere with the receive path signal, thus causing desense. Therefore, an additional filter is required to reduce the noise on the 5GHz receive signal. Figure 2: 5GHz automotive coexistence of V2X and Wi-Fi. Figure 3: Coexistence between cellular and Wi-Fi 2.4GHz band. Wi-Fi 2.4GHz Coexistence with Cellular Bands 7, 40, and 41 A second coexistence issue seen in V2X is the interference between cellular bands 7, 40 and 41 and the 2.4GHz Wi-Fi band. Shown in Figure 3, you can see that Wi-Fi 2.4GHz is positioned between and close to these TDD (B40 & B41) and FDD (B7) signals. When Wi-Fi 2.4 signals are transmitting and receiving in the vehicle, filters must be employed to make sure users on the cellular bands can continue communications without interruption. Again, this is achieved using BAW filter technology—both in discrete form and inside highly-integrated Qorvo modules. V2X Coexistence Challenge with Electronic Toll Collection Radios Beyond the above-mentioned coexistence challenges, there is the issue of V2X interfering with Electronic Toll Collection (ETC) services. ETC services in China and Europe operate very closely to the V2X bands. As shown in Figure 4, the European V2X band is only 40MHz from the European ETC band. The European V2X spectral emissions specification cannot be met without incorporating a notch filter at the input of the V2X front-end module, which allows the ETC to coexist with V2X. The same issue exists in a China ETC application. The V2X China band is only 65MHz from the downlink of the ETC band. A notch filter must be employed on the front-end input to reduce spectral emissions to properly coexist. In the future, the China ETC band may likely become even closer to the V2X band because Chinese carriers are seeing possible capacity constraints due