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WILEY ANTENNAS FOR PORTABLE DEVICES phần 6

đã được sử dụng cho nghiên cứu này. Hai ăng-ten khe cắm đã được thực hiện trên laptop ThinkPad, một phía trên bên trái và một ở cạnh trên bên phải của màn hình. Tỷ lệ cao của IBM Wireless LAN card PC đã được sử dụng cho việc nghiên cứu so sánh. | 134 Laptop Antenna Design and Evaluation Table 4.4 Integrated and PC Card Wireless Solutions SNR Comparison. Distance m 0 deg 90 deg 180 deg 270 deg Int Card Int Card Int Card Int Card 0 59 54 52 47 54 45 49 49 5 53 50 49 43 49 49 53 50 10 45 37 47 35 45 38 43 36 15 42 31 51 34 46 35 45 26 20 40 22 52 32 45 35 45 26 25 41 33 49 29 43 30 48 22 30 37 21 46 30 43 30 46 24 35 42 22 43 31 42 29 45 20 40 34 23 46 23 42 23 46 27 45 37 29 46 25 42 25 46 28 From 6 . Reproduced by permission of IBM. was used for this study. Two slot antennas were implemented in the ThinkPad one on the upper left side and another on the top right edge of the display. An IBM High Rate Wireless LAN PC card was used for the comparison study. Table 4.4 lists the SNR values for distances from 0 to 45 meters with laptop orientation angles 0 90 180 and 270 . The SNR values were obtained through the IBM WLAN Client Configuration Utility gain test program. Distances were measured from AP to laptop. Angle 0 is the laptop rear cover toward the north 90 is toward the west AP direction 180 is toward the south and 270 is toward the east. These actual tests indicate that integrated wireless is 47 better on average than the PC card version. When the laptop is far from the AP the integrated antenna has much higher gain values than the PC card antenna resulting in much higher SNR. Above 25 meters the SNR for the integrated wireless system is more than 10 dB larger than that of the PC card system. The higher SNR values imply longer distance for the same data rate or higher data rate for the same distance. As a practical example an iSeries ThinkPad with the integrated antenna was tested against a PC card version and shown to have superior performance. The test was conducted on the fifth floor of an IBM building in Yamato Japan. This floor has three APs. When the RF signal was weak the PC card switched to another AP while the iSeries integrated antenna performance was still good and maintaining a connection to .