From 4160411d335b7edb6ca4b6f911987cdeb148594a Mon Sep 17 00:00:00 2001 From: Jiao Xianjun Date: Tue, 18 Aug 2020 10:31:01 +0200 Subject: [PATCH] Update README.md --- doc/README.md | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/doc/README.md b/doc/README.md index 70e273f..e1850a6 100644 --- a/doc/README.md +++ b/doc/README.md @@ -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: