Integrated laptop antennas - design and evaluation

Two performance parameters are used to define integrated antennas for laptop applications. One is SWR, and another is the average antenna gain. Based upon link budget models and system requirements, the integrated antennas should have a 2:1 SWR bandwidth, wide enough to cover the 2.4 GHz ISM band to ensure a wireless system to have reliable, high data rate performance over a useful range or coverage area. The antenna should have average gain values similar to that of an isotropic radiator. The average gain value can be used in a communication link budget model to predict system level performance such as throughput and range. The antenna polarization is not a critical parameter for laptop applications since laptops are primarily used in indoor environment where there is high scattering and mixing of signals. As one would expect, the best location for integrated antennas in laptops is to place the antenna on the laptop display as high as possible. But using this location forces a design trade-off between the antenna's "visibility" and the necessity of a lossy feed cable, since wireless cards are usually placed in the base of a laptop. The ultimate system cost, time to market and performance are consciously traded off for each and every application.