Issue link: https://resources.mouser.com/i/1207833
13 In-device coexistence: For in-device coexistence, the system's multiple antenna architectures can interfere with each other. As a result, the coupling between the affected antennas (antenna isolation) is compromised. The foreign transmit (Tx) signal increases the noise power at the affected receiver, which has a negative impact on the signal-to-noise ratio. The receive (Rx) sensitivity decreases, which causes what engineers call "desensitization." Desensitization is a degradation of the sensitivity of the receiver due to external noise sources, and results in dropped or interrupted wireless connections. It isn't a new problem—early radios encountered receiver sensitivity when other components became active—but now it's particularly troublesome for today's wireless technologies, including smartphones, Wi-Fi routers, Bluetooth speakers, and other devices. The primary "desense" scenarios are: • Two radio systems occupy bordering frequencies, and carrier leakage occurs. • The harmonics of one transmitter fall on the carrier frequencies used by another system. • Two radio systems share the same frequencies. LTE and Wi-Fi: As shown in the below figure, several LTE bands— Bands 40, 7, and 41—are very close to the Wi-Fi band channels. Leakage into the adjacent Wi-Fi radio band is very probable at both the high and low end of the 2.4 GHz band. Without proper system design, the cellular and Wi-Fi channels 1 and 11 can interfere with each other's transmissions and receive capability. Bluetooth and Wi-Fi: Bluetooth and Wi-Fi transmit in different ways using differing protocols, but they operate in the same frequency ranges, as shown in the following figure. As a result, when Wi-Fi operates in the 2.4 GHz band, Wi-Fi and Bluetooth transmissions can interfere with each other. Because Bluetooth and Wi-Fi radios often operate in the same physical area (such as inside an access point), interference between these two standards can impact the performance and reliability of both wireless interfaces. Why Band Edges Matter for Wi-Fi Coexistence One way federal governments have tried to help consumers is by regulating the emissions and spectrum of many electronic devices and requiring consumer products to undergo compliance testing. In the United States, the Federal Communications Commission (FCC) requires that most RF devices undergo testing to demonstrate compliance to FCC rules. They enforce strict band edges by requiring steep skirts on the lower and upper Wi-Fi frequencies, to help with coexistence with neighboring spectrum. There are two ways for Wi-Fi access points to meet this FCC requirement: 1. Back off the power level on Wi-Fi channel 1 and 11, because they're at the edge of the Wi-Fi spectrum. 2. Use filters with very steep band edges. ©2018 Qorvo, Inc. In-Device and External Interference ©2018 Qorvo, Inc. Spectrum Example of Asia and EMEA TD-LTE China (Indoor) / Asia Worldwide HK / EMEA China (Outdoor) / EMEA TD-LTE TD-LTE China / N. Amer. LTE-FDD Band 40 Wi-Fi Band 41 Band 7 (Up) Band 38 Band 7 (Down) Band E China TD-SCDMA Wi-Fi Ch1-Ch13 2320 2370 2496 2690 2690 2300 2400 2483 2500 ©2018 Qorvo, Inc. ISM, Wi-Fi & Bluetooth Channel Frequencies 2360-2390 MHz 2483.5-2495 MHz FCC Bandedge FCC Bandedge Wi-Fi Ch1-Ch11 Wi-Fi Worldwide 2400-2473 MHz ©2018 Qorvo, Inc. Spectrum Example of Wi-Fi and Bandedge