New Types Of Flat Broadband Multi-frequency Antenna Research And Design

In recent years, mobile communication has been developed fast and new wireless communication standards appear continuously. These standards demand that systems can operate in wideband multi-band. For example, the WLAN systems operate in the band at 2.45 GHz (2400-2484 MHz), 5.2 GHz (5150-5350 MHz) and 5.8 GHz (5725-5825 MHz), the WIMAX systems operate in the band at 2.5/3.5/5.5 GHz (2500-2690/3400-3690/5250-5850 MHz). Therefore, in order to satisfy these standards, antennas with wideband dual- or multi- frequency capabilities become a hot topic in the field of antennas.In this thesis, many new techniques of wideband dual-frequency antennas and wideband triple-frequency antennas are presented and studied in detail, firstly. Secondly, a novel isosceles triangular multi-frequency microstrip antenna is presented. This antenna can operate at three frequencies. Furthermore, the antenna's operating frequency ratios can be tuned. Thirdly, on the base of this triangular antenna, three novel wideband dual-frequency antennas are designed. They are a dual-band patch antenna with an F-shaped parasitic strip, a printed circular disc monopole antenna with an H-shaped ground plane and a dual-band circle slot antenna with a cross-shaped parasitic strip, respectively. The center frequency ratios of these antennas can be tuned. This means that the antennas can satisfy different demand. Optimizing the geometric parameters of the antennas, all of them can meet the IEEE 802.11 WLAN standards in the 2.45/5.2/5.8 GHz operating bands.In this investigation, the simulation tools are HFSS and CST. For dual-band monopole antenna with an F-shaped parasitic strip, very good agreement between two simulated results is obtained. For other dual-band antennas, we fabricate the experimental models. Some experimental results show good agreement with simulated results.