A planar dipole array antenna having good omnidirectional radiation in the azimuthal plane is presented. The planar dipole array antenna comprises two 1 2 dipole arrays arranged back to back and separated by a narrow rectangular ground plane, and is easily constructed by printing on both sides of a dielectric substrate. Prototypes of the proposed antenna for WLAN operation in the 2.4 GHz band (2400-2484 MHz) were constructed and studied. Good omnidirectional radiation with gain variations less than 2 dBi in the azimuthal plane has been obtained, and the measured maximum antenna gain for operating frequencies across the 2.4 GHz band is about 5.0-6.1 dBi. Effects of the ground-plane width and the array spacing on the performance of the proposed antenna are also studied.Index Terms-Antennas, array antennas, dipole antennas, omnidirectional dipole array antennas.
of the printed PIFA show no special distinction when compared with those of the hybrid PIFA shown here. Thus, the radiation patterns of the printed PIFA are not shown for brevity. Figure 10 presents the measured antenna gain and simulated radiation efficiency over the lower and upper bands of the hybrid PIFA studied in Figure 3. For the lower band from 1.88 to 2.75 GHz, the antenna gain is varied in the range of 1.3-2.5 dBi, while the radiation efficiency is about 85% over the band. As for the upper band from 4.89 to 5.90 GHz, the antenna gain is varied from about 4.1 to 5.5 dBi, and the radiation efficiency is also about 85% over the band. The corresponding results of the printed PIFA studied in Figure 4 are shown in Figure 11. It can be seen that the obtained antenna gain and radiation efficiency are about the same as those shown in Figure 10. That is, similar radiation characteristics of the hybrid and printed PIFAs studied here are obtained.
CONCLUSIONTwo kinds of promising PIFAs (hybrid PIFA and printed PIFA) for application in a USB dongle have been proposed, fabricated, and tested. Both the hybrid and printed PIFAs occupy a compact volume and can easily be embedded inside the casing of the general USB dongle as internal antennas. In addition, both the two PIFAs can provide two wide operating bands for covering UMTS/ WLAN/WiMAX multi-network operation. Easy adjustment of the two wide operating bands of the proposed hybrid and printed PIFAs has also been obtained. The two PIFAs also show good radiation characteristics over their two wide operating bands.
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