Automated Calibration of RF Test Station and Out of Band Emission Measurements

Abstract

There is a tremendous development in WLAN technologies since last few years. Latest 802.11 standards for WLAN radios are 802.11n and 802.11ac were accepted in the year 2009 and 2013 respectively. It provides for very high data rates of the order of 780 Mbps, in the frequency band of 2 GHz and 5 GHz. Higher data rate transmission also requires very high power, which ultimately leads to Spurious emissions. There are various devices in the transmitter and receiver chain of radio devices which leads to spurious emissions. These emissions if left uncontrolled, interferes with the other neighboring devices. It ultimately degrades the chip performance and at times leads to chip failure. The aim of this report is to follow regulations prescribed by Federal Commission Committee (FCC). It is the regulatory bodies specifying and enforcing the spectral mask requirements. The process is developed to automate the calibration of entire RF test station. Such that it can accurately perform out of band emission measurements. A step by step procedure is evolved and followed to measure and maintain the spurious emission levels in the range of -60 dBm to -72 dBm. RF Test station is calibrated for out of band emission measurement using python scripting language. Standard commands for programmable instruments (SCPI) commands are used to automate network analyzer. It is important to calibrate the entire station for higher frequency range. As frequency increases we see a lot of fluctuations/jitter in insertion loss. It must be reduced to the minimal level, otherwise this can wrongly be interpreted as spur. These fluctuations can couple through actual spur and at times may lead to misleading results. Critical spur levels of WLAN chip is analyzed and steps are taken to improve the same. With the optimization methods applied, were able to improve the spur levels in the range of 3 dBm to 10 dBm in different WLAN channels. The overall spur reduction falls in the range of (1.5 - 8) percentage.