Design Of Dual-band Antenna And Feeding Units For WLAN Application

With the development of communication and network technology the demands for network communication grow more and more. We hope that we can break up traditional wired network mode and realize the target of wireless communication without geographical restrictions. Soon after, many specialists and scholars develop WLAN (Wireless Local Area Network) communication system. The appearance of WLAN commutation system brings people great convenience which promotes wireless networking to a new period.IEEE (Institute of Electrical and Electronics Engineers) released 802.11 standard about WLAN commutation system in 1997. After years of development, there have been many kinds of standards about WLAN communication system. Among all the standards,2.4GHz (2.4GHz-2.484GHz) of IEEE802.11b standard and 5.2GHz (5.15GHz-5.35GHz) of IEEE802.11a standard are the most common standards. To reduce size and weight of communication device, developing dual-band WLAN system components working at both 2.4GHz band and 5.2GHz band is significant.Antenna, filter and power divider are important antenna and feeding units in WLAN system. This paper researches on the design and implementation method about dual-band antenna and feeding units for WLAN system. At present, although there are many ways of realizing dual-band WLAN antenna and feeding units, such as, waveguide structure, microstrip structure, coaxial structure, etc, microstrip structure is adopted in this paper because of its advantages, such as, small size, light weight, planar structure, low cost, easy to implementation and so on. In this paper, theoretical analysis combining with electromagnetic simulation is used to design these units. The monopole antenna takes advantage of double-sided loading of the radiating patch to achieve dual-band performance. Its-10dB return loss frequency bands are from 2.271 GHz to 2.547GHz and 4.908GHz to 5.397GHz, bandwidthes are 276MHz and 489MHz,respectively, Gains are 1.93dB at 2.4GHz and 2.45dB at 5.2GHz, both of them meet the requirement for WLAN antenna. The power divider uses two different impendence transmission lines to achieve broadband and dual-band performance. Its bandwith is 1.84GHz (1.58GHz-3.42GHz) and 1.48GHz(4.34GHz-5.92GHz) when return loss is below-10dB, the isolation between two output ports are-18dB and-32dB at the two frequencies. The filter realizes dual-band performance by coupled resonators’ parasitic passband. Its insertion loss is below 0.7dB at 2.4GHz and 1.79dB at 5.2 GHz, which achieve a good frequency response.