Issue link: https://resources.mouser.com/i/1207833
Qorvo 885136 2.4GHz RF BAW Filter Wi-Fi Band Edge Qorvo 885128 2.4GHz Wi-Fi/BT LTE Co-Existence Filter Key Features: • Industry leading size - 1.1 x 0.9 x 0.50mm • Performance over -40 to +95ºC • High rejection at 2390MHz, 2483.5MHz, B38/ B40/B7/B41 Key Features: • Low loss in Wi-Fi band with extended upper corner for inclusion of Bluetooth • High rejections in LTE bands B7 / B41 / B38 / B40 • Performance over -40 to +95ºC 14 Design Tips to Overcome Interference Challenges: Use High-Q BAW Filters Our approach is to use high-performance coexistence and bandedge filters, to allow Wi-Fi transmitters to operate close to the upper and lower FCC band edges. Customers have had success using high-Q bulk acoustic wave (BAW) bandpass filters, which offer many advantages: • Extremely steep skirts that simultaneously exhibit low loss in the Wi-Fi band and high rejection in the band edge and adjacent LTE/Time-Division Long-Term Evolution (TD-LTE) bands • Significant size reductions, which aid designers in creating smaller, more attractive end-user devices for homes and office environments • Resolves coexistence of Wi-Fi and LTE signals within the same device or near one another • Unique power handling capabilities, allowing for implementation into high-performance, high-power access points and small cell base stations These filters address the stringent thermal challenges of multi-user multiple input/multiple output (MU-MIMO) systems, without compromising harmonic compliance and emissions performance. This is critical to achieving reliable coverage across the full allocated spectrum. But why do high-Q BAW filters make such a difference for FCC band edges? #1: BAW devices have lower insertion loss, steeper band edges, and better temperature stability than SAW technology at Wi-Fi frequencies As you move into higher bandwidths like Wi-Fi, surface acoustic wave (SAW) devices can suffer from higher insertion losses than BAW due to radiation of acoustic energy into the bulk of the substrate. As shown in the following figure, as you move up (to the right) in frequency, you can see high-Q BAW is a better option for filter designs due to this bulk radiation loss effect. Also, BAW maintains the steep skirts required for FCC band edges; SAW can't meet the performance requirements at these higher frequencies. BAW also has better temperature stability than other technologies, which gives it an advantage during FCC certification tests. Most Wi-Fi designs are created at room temperature (20-25°C) on a bench, but the system in its application environment can actually operate around 60-80°C. Insertion loss increases as temperature increases, and failing to estimate for this can cause issues during product certification. Using BAW reduces the shifts in insertion loss and makes certification test results more predictable. BAW vs. SAW B3 Tx Filter db(S(116,119)) dB(S(56,59)) db(S(116,120)) dB(S(56,60)) db(S(116,117)) dB(S(56,57)) db(S(116,118)) dB(S(56,58)) Frequency (GHz) 1.690 0 -1 -2 -3 -4 -5 0 -1 -2 -3 -4 -5 0 -1 -2 -3 -4 -5 0 -1 -2 -3 -4 -5 1.710 1.730 1.750 1.770 1.790 1.805 1.785 1.805 1.825 1.845 1.865 1.885 1.900 1.90 1.91 1.92 1.93 1.94 1.95 1.96 1.97 1.98 1.99 2.00 2.09 2.10 2.11 2.12 2.13 2.14 2.15 2.16 2.17 2.18 2.19 Frequency (GHz) Frequency (GHz) Frequency (GHz) 1700 1740 B3 UL B3 DL B1 UL B1 DL 1780 1820 1860 Frequency 1900 1940 1980 2100 2140 2180 B3 Rx Filter B1 Tx Filter B1 Rx Filter BAW SAW ©2018 Qorvo, Inc. BAW Versus SAW Technology