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@ -218,7 +218,7 @@ Linux mac80211 (struct ieee80211_ops openwifi_ops in sdr.c) uses the "config" AP
## Analog and digital frequency design
Following figure shows the current openwifi analog and digital frequency design strategy. The Tx RF center frequency is tuned with 10MHz offset deliberately to ease Tx Lo leakage suppressed by Rx filter. This RF offset is pre-compensated by Tx DUC (Digital Up Converter) in FPGA (duc_bank_core.bd used by tx_intf.v). It combines AD9361's bandwidth, frequency, sampling rate and FPGA's digital down/up converter (ddc_bank_core.bd/duc_bank_core.bd) setting to achieve this example spectrum arrangement. Values in the figure are configurable in the openwifi design.
Following figure shows the current openwifi analog and digital frequency design strategy. The Tx RF center frequency is tuned with 10MHz offset deliberately to ease Tx Lo leakage suppressed by Rx filter. This RF offset is pre-compensated by Tx DUC (Digital Up Converter) in FPGA (duc_bank_core.bd used by tx_intf.v). It combines AD9361's bandwidth, frequency, sampling rate and FPGA's digital down/up converter (ddc_bank_core.bd/duc_bank_core.bd) setting to achieve this example spectrum arrangement. Values in the figure are configurable in the openwifi design. Please be noticed that ddc_bank_core.bd is not used anymore. Because the digital and analog RX Lo is the same, mixer is not needed. Decimation by 2 is implemented in adc_intv.v.
![](./rf-digital-if-chain-spectrum.jpg)
Above spectrum setting has two benefits: