There is a fast development and expansion of portable computer wireless systems. Cellular network radios are integrated into some modem laptop, notebook and palmtop computers in order to give the user access to the Internet in areas not covered by WLANs. Furthermore, computer manufacturers are now offering integrated WiMax as an option on some notebooks and, laptops. Introduction of other applications such as GPS and digital TV, built into portable computers, is expected in the near future. On the other hand, most of these applications have different standards with different frequency allocations worldwide. For example, DVB-H mobile TV is designed to work in different bands such as UHF and L bands. Also, WiMax has many frequency allocations worldwide such as 700 MHz, 2.5 GHz and 3.5 GHz. Even GPS has different codes at different bands such as L_1 (1575.42 MHz) and L_2 (1227.6 MHz). In order to cover all these bands, several antennas have to be used. The problem is that the bands of some applications are very close to each other or even overlapping as in GSM and UHF digital TV. As a result, there will be a severe interference between these antennas.
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