Method of evaluating electromagnetic-interference characteristics of wireless LANs by narrowing frequency bandwidth of desired waves

We evaluated the electromagnetic-interference characteristics of WLANs by using an opened Parallel Wired (PW) cell that is placed in a radio anechoic chamber. We used a new narrowband WLAN system to do this evaluation, which we have been developing to reduce electromagnetic-interference problems and increase the number of channels so that many systems can use this simultaneously in the same location. As a result, we found that 10- and 5-MHz WLAN systems can improve the PER characteristics more than a conventional WLAN system with a channel spacing of 20 MHz when impressing an interference wave with a narrow bandwidth such as that specified by the IEC 61000-4-3 standards as well as that with a wide bandwidth such as that specified by the WLAN IEEE802.11b standards. In addition, when impressing the IEEE802.11b wave to the 10-MHz system, the PER characteristics to Chs. 1 and 2 were improved by about 20 dB on the desired-to-undesired (D/U) signal power ratio and those to Ch. 3 were improved by about 30 dB on D/U compared with impressing an interference wave to a 20-MHz system.