in [10] marks a characteristic design of antenna with two
separate radiators and a microstrip feed line suitable for the
WLAN operation. We want to expand the bandwidth and
apply it to the WLAN/WiMax operation but cannot find an
easy way out. The main difference of frequency requirement
between WLAN and WLAN/WiMax is the bandwidth of low
frequency. According to my experiences in the design of
antenna, there are always more difficulties nested in low
frequency than high frequency for bandwidth expansion.