From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benoit Papillault Date: Tue, 12 Jun 2012 10:38:59 +0200 Subject: [ath9k-devel] TX power and TPC Message-ID: <4FD70023.1000603@free.fr> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: ath9k-devel@lists.ath9k.org Hello there, I'm working on EN 301 893 certification. There is a part regarding the RF Output Power to make sure that the RF Output Power is within some limits. Let's say 27 dBm at 5600 MHz for instance. In 4.4.1.1, the RF Output Power is defined as the "mean EIRP during a transmission burst". This is exactly the RF power at the connector + the antenna gain. So, I started with an AR9280 card / ath9k and hookep up to a Spectrum Analyzer with a Channel Power measure. It has been configured with RMS detector / Average trace over 100 samples. In order to be close to 100% duty cycle, I did a "ping -I wlan0 -b 255.255.255.255 -f -s 1472" (OK, this is not perfect, but it has been compared with continuous transmit on some other chipset and gives a 0.1 dBm difference). I also did a Peak power measure using the Peak detector / Max hold trace of the spectrum analyzer. I made another measure using a USB power sensor over 10MHz - 12.4 GHz. Here are the raw results (iwconfig is the reported TX power, BTW, any way to do that with iw ? ) : mBm | iwconfig | Peak/Max Hold | RMS/Average | USB Power Sensor 0 | 3 dBm | -3.8 dBm | -14.5 dBm | -14.2 dBm 100 | 3 dBm | -3.2 dBm | -14.4 dBm | -14.1 dBm 200 | 3 dBm | -3.3 dBm | -14.4 dBm | -14.1 dBm 300 | 3 dBm | -3.1 dBm | -14.5 dBm | -14.1 dBm 400 | 4 dBm | 0.6 dBm | -11.4 dBm | -10.0 dBm 500 | 5 dBm | 2.9 dBm | -9.5 dBm | -7.9 dBm 600 | 6 dBm | 4.8 dBm | -7.8 dBm | -6.0 dBm 700 | 7 dBm | 6.2 dBm | -6.5 dBm | -4.6 dBm 800 | 8 dBm | 7.4 dBm | -5.6 dBm | -3.5 dBm 900 | 9 dBm | 8.6 dBm | -4.6 dBm | -2.3 dBm 1000 | 10 dBm | 9.7 dBm | -3.6 dBm | -1.1 dBm 1100 | 11 dBm | 10.8 dBm | -2.7 dBm | -0.1 dBm 1200 | 12 dBm | 12.0 dBm | -2.0 dBm | 0.9 dBm 1300 | 13 dBm | 12.7 dBm | -1.2 dBm | 1.6 dBm 1400 | 14 dBm | 13.5 dBm | -0.2 dBm | 2.8 dBm 1500 | 15 dBm | 15.0 dBm | 1.0 dBm | 3.9 dBm 1600 | 16 dBm | 16.3 dBm | 2.2 dBm | 5.2 dBm 1700 | 17 dBm | 18.1 dBm | 2.8 dBm | 6.1 dBm 1800 | 18 dBm | 18.4 dBm | 3.5 dBm | 6.9 dBm 1900 | 19 dBm | 19.7 dBm | 4.2 dBm | 7.6 dBm 2000 | 20 dBm | 20.1 dBm | 5.2 dBm | 8.8 dBm 2100 | 21 dBm | 21.0 dBm | 6.0 dBm | 9.7 dBm I am not 100% confident in the way I did all those measures. If you know a better way to achieve them, please stand up. Questions are : 1. since regulatory limitation are based on "mean EIRP over burst" ... why the driver is calibrated over "peak power" ? We are just loosing 11 dBm or so. 2. What would explain the difference between the RMS power measured from the SA and the power measured by the power sensor ? Regards, Benoit