From 8421731be5b14581f5c566727cbdde1dd79b37f1 Mon Sep 17 00:00:00 2001 From: Jiao Xianjun Date: Sun, 20 Dec 2020 16:02:28 +0100 Subject: [PATCH] Update iq_2ant.md --- doc/app_notes/iq_2ant.md | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/doc/app_notes/iq_2ant.md b/doc/app_notes/iq_2ant.md index 42504bf..74da5a5 100644 --- a/doc/app_notes/iq_2ant.md +++ b/doc/app_notes/iq_2ant.md @@ -40,7 +40,9 @@ In this app note, we show how to use the dual antenna I/Q capture to capture the python3 iq_capture_2ant.py (if smaller FPGA, like z7020, is used, add a argument that equals to iq_len_init, like 4095) ``` - Above script will plot the real-time rx0 and rx1 I/Q captured each time trigger condition met. Meanwhile the script also prints the maximum amplitutde of the rx0 and rx1 I/Q samples. Check the 3rd column that is displayed by the script: Those small value printing indicate noise (most probably, because the rx1 gain is very low). The big value printing indicate a packet from rx1 (although rx1 has very low gain, rx1 is very close to the peer WiFi node). Go through the noise and the packet max I/Q amplitude numbers from rx1 printing (the 3rd column), and decide a threshold value that is significantly higher than the noise but less than those big values (packets). + Above script will plot the real-time rx0 and rx1 I/Q captured each time trigger condition met. + ![](./iq_2ant-screen-shot.jpg) + Meanwhile the script also prints the maximum amplitutde of the rx0 and rx1 I/Q samples. Check the 3rd column that is displayed by the script: Those small value printing indicate noise (most probably, because the rx1 gain is very low). The big value printing indicate a packet from rx1 (although rx1 has very low gain, rx1 is very close to the peer WiFi node). Go through the noise and the packet max I/Q amplitude numbers from rx1 printing (the 3rd column), and decide a threshold value that is significantly higher than the noise but less than those big values (packets). - Set trigger condition to 29, which means that rx1 I/Q is found larger than a threshold while SDR is transmitting -- this means a collision condition is captured because rx1 I/Q implies the transmitting from the peer WiFi node. The threshold value is decided in the previous step (2500 is assumed here). ``` (Quit side_ch_ctl by Ctrl+C)