Automatic direction system for outdoor WLAN antenna array driven by AT89S51 microcontroller

In this paper an automatic direction system developed driven by AT89S51 microcontroller is proposed for outdoor wireless local area network (WLAN) antenna array. The system is intended to overcome the issue of direction lost of outdoor WLAN antenna array installed on a high spot caused by the wind and surrounding circumstances. The proposed system which is equipped with automatic radio frequency (RF) power level sensor will fix the direction of antenna to the proper orientation in azimuth direction by retrieving the received RF signal. In general the system consists of RF rectifier in the front-end to rectify the received RF signal and then convert it into a dc voltage. The output of RF rectifier is fed into operational amplifier (Op-Amp) to achieve the dc voltage level suitable for analog-to-digital converter (ADC) before being processed by microcontroller. From experimental characterization, it shows that the shifting of antenna array direction influences remarkably the received RF signal and is linear to the output voltage level of RF sensor in which for each 5dBm received RF signal produces 1mV output voltage level of RF sensor. Furthermore, the realized automatic direction system can handle the reflection angle of antenna array up to ±18° in azimuth direction.